AutistMask/tests/uniswapRecipient.test.js

// The address a swap's output is paid to
// (https://git.eeqj.de/sneak/AutistMask/issues/594 and
// https://git.eeqj.de/sneak/AutistMask/issues/599), and the allow-revert flag
// on the steps that pay it
// (https://git.eeqj.de/sneak/AutistMask/issues/602).
//
// Every swap command, SWEEP, WRAP_ETH, UNWRAP_WETH, TRANSFER, PAY_PORTION,
// PAY_PORTION_FULL_PRECISION, PERMIT2_TRANSFER_FROM, ACROSS_V4_DEPOSIT_V3 and
// V4 TAKE and TAKE_PORTION names the address it pays, and TAKE_ALL pays the
// sender. The decoder read none of them: a swap whose output went to another
// address still read "Min. received", as if the user received it. The router
// reads address(1) as the sender and address(2) as the router itself, which
// holds what it is paid until a later step pays it out.
//
// The screens are driven against a minimal DOM stub in the shape
// tests/uniswapRouterAddress.test.js uses.

const { AbiCoder, Interface, solidityPacked } = require("ethers");

jest.mock("../src/shared/log", () => ({
    log: {
        debugf: () => {},
        infof: () => {},
        warnf: () => {},
        errorf: () => {},
    },
    debugFetch: async (url) => ({
        ok: true,
        json: async () => mockExplorerAnswer(url),
    }),
    setRuntimeDebug: () => {},
    isDebug: () => false,
}));

globalThis.chrome = {
    storage: { local: { get: async () => ({}), set: async () => {} } },
};

const uniswap = require("../src/shared/uniswap");
const { state } = require("../src/shared/state");
const approval = require("../src/popup/views/approval");
const transactionDetail = require("../src/popup/views/transactionDetail");

// UniversalRouterV2 on Ethereum Mainnet.
const ROUTER = "0x66a9893cc07d91d95644aedd05d03f95e1dba8af";
// UniversalRouterV2_1_2 on Ethereum Mainnet, whose mask reads 0x07 and 0x40.
const ROUTER_V2_1_2 = "0x23617e59A5925b2A4Bf75d73ff6711cD0b29De85";
// UniversalRouterV1 on Ethereum Mainnet.
const ROUTER_V1 = "0xEf1c6E67703c7BD7107eed8303Fbe6EC2554BF6B";
const USER = "0x66133E8ea0f5D1d612D2502a968757D1048c214a";
const OTHER = "0x7777777777777777777777777777777777777777";
const MSG_SENDER = "0x0000000000000000000000000000000000000001";
const ADDRESS_THIS = "0x0000000000000000000000000000000000000002";
const ZERO = "0x0000000000000000000000000000000000000000";

const USDT = "0xdAC17F958D2ee523a2206206994597C13D831ec7";
const USDC = "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48";
const WETH = "0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2";
// A token the wallet does not know.
const UNKNOWN_TOKEN = "0x5555555555555555555555555555555555555555";
const ONE_WETH = 1000000000000000000n;
const USDT_2000 = 2000000000n;
const USDC_1990 = 1990000000n;
// The router's whole-balance amount.
const CONTRACT_BALANCE = 2n ** 255n;

// The Paid to line's value when no address can be named.
const UNDECODED = "Unknown (could not be decoded)";
const UNNAMED = "Unknown (not named in the calldata)";
const STAYS_IN_ROUTER =
    "The router, where it stays (no later step pays it out)";
const PAID_TO_BRIDGE =
    "The bridge, which pays the deposit's recipient on another network";
// The Paid to line for a PERMIT2_TRANSFER_FROM of `amount` into the router.
const movedIntoRouter = (amount) =>
    "The router, " +
    amount +
    " from the sender (later steps may not spend all of it)";

const coder = AbiCoder.defaultAbiCoder();
const routerIface = new Interface([
    "function execute(bytes commands, bytes[] inputs, uint256 deadline)",
]);

// execute() of `steps`, each [command, input].
function execute(...steps) {
    const commands = steps.map(([command]) => command);
    return routerIface.encodeFunctionData("execute", [
        solidityPacked(
            commands.map(() => "uint8"),
            commands,
        ),
        steps.map(([, input]) => input),
        9999999999n,
    ]);
}

// V2_SWAP_EXACT_IN (0x08) and V2_SWAP_EXACT_OUT (0x09) share one layout.
function v2Swap(command, recipient, amount, limit, path, payerIsUser = true) {
    return [
        command,
        coder.encode(
            ["address", "uint256", "uint256", "address[]", "bool"],
            [recipient, amount, limit, path, payerIsUser],
        ),
    ];
}

function v3SwapExactIn(
    recipient,
    amountIn,
    amountOutMin,
    tokenIn,
    tokenOut,
    payerIsUser = true,
) {
    return [
        0x00,
        coder.encode(
            ["address", "uint256", "uint256", "bytes", "bool"],
            [
                recipient,
                amountIn,
                amountOutMin,
                solidityPacked(
                    ["address", "uint24", "address"],
                    [tokenIn, 3000, tokenOut],
                ),
                payerIsUser,
            ],
        ),
    ];
}

function sweep(token, recipient) {
    return [
        0x04,
        coder.encode(["address", "address", "uint256"], [token, recipient, 0n]),
    ];
}

// TRANSFER (0x05), PAY_PORTION (0x06) and PAY_PORTION_FULL_PRECISION (0x07)
// share one layout. `amount` is a quantity, bips, or 1e18ths respectively.
function transfer(command, token, recipient, amount) {
    return [
        command,
        coder.encode(
            ["address", "address", "uint256"],
            [token, recipient, amount],
        ),
    ];
}

// PERMIT2_PERMIT (0x0a) of `amount` of `token`, for the router to spend.
function permit2Permit(token, amount) {
    return [
        0x0a,
        coder.encode(
            [
                "tuple(tuple(address,uint160,uint48,uint48),address,uint256)",
                "bytes",
            ],
            [[[token, amount, 0, 0], ROUTER, 0n], "0x"],
        ),
    ];
}

function permit2TransferFrom(token, recipient, amount) {
    return [
        0x02,
        coder.encode(
            ["address", "address", "uint160"],
            [token, recipient, amount],
        ),
    ];
}

// ACROSS_V4_DEPOSIT_V3 (0x40) of `inputAmount` of `inputToken`, bridged to
// chain id 8453.
function acrossDeposit(
    depositor,
    recipient,
    inputToken,
    inputAmount,
    useNative = false,
) {
    return [
        0x40,
        coder.encode(
            [
                "tuple(address,address,address,address,uint256,uint256,uint256,address,uint32,uint32,uint32,bytes,bool)",
            ],
            [
                [
                    depositor,
                    recipient,
                    inputToken,
                    inputToken,
                    inputAmount,
                    1n,
                    8453n,
                    ZERO,
                    0,
                    0,
                    0,
                    "0x",
                    useNative,
                ],
            ],
        ),
    ];
}

function wrapEth(recipient, amount) {
    return [0x0b, coder.encode(["address", "uint256"], [recipient, amount])];
}

function unwrapWeth(recipient) {
    return [0x0c, coder.encode(["address", "uint256"], [recipient, 0n])];
}

function balanceCheck(token, minBalance) {
    return [
        0x0e,
        coder.encode(
            ["address", "address", "uint256"],
            [USER, token, minBalance],
        ),
    ];
}

// `step`, a [command or action, input] pair, with the top byte of the input's
// word `index` set. The decoder cannot read that word as an address.
function withDirtyWord([id, input], index) {
    const at = 2 + index * 64;
    return [id, input.slice(0, at) + "ff" + input.slice(at + 2)];
}

// The V4 actions a step below is built from.
const SWAP_USDT_FOR_USDC = [
    0x06, // SWAP_EXACT_IN_SINGLE
    coder.encode(
        [
            "tuple(tuple(address,address,uint24,int24,address),bool,uint128,uint128,bytes)",
        ],
        [[[USDT, USDC, 100, 1, ZERO], true, USDT_2000, USDC_1990, "0x"]],
    ),
];
const SWAP_USDT_FOR_ETH = [
    0x06, // SWAP_EXACT_IN_SINGLE
    coder.encode(
        [
            "tuple(tuple(address,address,uint24,int24,address),bool,uint128,uint128,bytes)",
        ],
        [[[ZERO, USDT, 500, 10, ZERO], false, USDT_2000, ONE_WETH, "0x"]],
    ),
];
// SWAP_EXACT_IN_SINGLE with no parameters, which cannot be read.
const UNREADABLE_SWAP = [0x06, "0x"];
const SETTLE_USDT = [
    0x0b,
    coder.encode(["address", "uint256", "bool"], [USDT, 0n, true]),
];
function take(currency, recipient) {
    return [
        0x0e,
        coder.encode(
            ["address", "address", "uint256"],
            [currency, recipient, 0n],
        ),
    ];
}
function takeAll(currency) {
    return [0x0f, coder.encode(["address", "uint256"], [currency, 0n])];
}
function takePortion(currency, recipient, bips) {
    return [
        0x10,
        coder.encode(
            ["address", "address", "uint256"],
            [currency, recipient, bips],
        ),
    ];
}

// A V4_SWAP step of `actions`, each [action, params].
function v4Swap(...actions) {
    return [
        0x10,
        coder.encode(
            ["bytes", "bytes[]"],
            [
                solidityPacked(
                    actions.map(() => "uint8"),
                    actions.map(([action]) => action),
                ),
                actions.map(([, params]) => params),
            ],
        ),
    ];
}

function decode(data, sender = USER, router = ROUTER) {
    return uniswap.decode(data, router, "0x1", {}, sender);
}

function labels(result) {
    return result.details.map((d) => d.label);
}

function detail(result, label) {
    return result.details.find((d) => d.label === label);
}

function paidTo(result) {
    return result.details
        .filter((d) => d.label === "Paid to")
        .map((d) => d.value);
}

// A swap paid to the user, the lines it has always had.
const PAID_TO_USER = [
    "Protocol",
    "Token In",
    "Amount",
    "Token Out",
    "Min. received",
    "Steps",
    "Deadline",
];
const PAID_ELSEWHERE = [
    "Protocol",
    "Token In",
    "Amount",
    "Token Out",
    "Paid to",
    "Min. paid out",
    "Steps",
    "Deadline",
];

// A swap of 2,000 USDT for at least 1 WETH, paid to `recipient`.
const swapToWeth = (recipient) =>
    v3SwapExactIn(recipient, USDT_2000, ONE_WETH, USDT, WETH);

beforeEach(() => {
    state.trackedTokens = [];
    state.wallets = [];
});

describe("each swap command's recipient", () => {
    test.each([
        {
            kind: "V2_SWAP_EXACT_IN",
            data: (r) =>
                execute(v2Swap(0x08, r, USDT_2000, ONE_WETH, [USDT, WETH])),
            min: "1.0000 WETH",
        },
        {
            kind: "V2_SWAP_EXACT_OUT",
            data: (r) =>
                execute(v2Swap(0x09, r, ONE_WETH, USDT_2000, [USDT, WETH])),
            min: "1.0000 WETH",
        },
        {
            kind: "V3_SWAP_EXACT_IN",
            data: (r) => execute(swapToWeth(r)),
            min: "1.0000 WETH",
        },
        {
            kind: "V4_SWAP with TAKE",
            data: (r) =>
                execute(v4Swap(SWAP_USDT_FOR_USDC, SETTLE_USDT, take(USDC, r))),
            min: "1990.0000 USDC",
        },
    ])(
        "$kind: paid to the user it reads as before; paid to another address it names that address",
        ({ data, min }) => {
            const viaPlaceholder = decode(data(MSG_SENDER));
            expect(labels(viaPlaceholder)).toEqual(PAID_TO_USER);
            expect(detail(viaPlaceholder, "Min. received").value).toBe(min);
            // The sender's own address, in any case, reads the same.
            expect(decode(data(USER), USER.toLowerCase()).details).toEqual(
                viaPlaceholder.details,
            );

            const toOther = decode(data(OTHER));
            expect(labels(toOther)).toEqual(PAID_ELSEWHERE);
            expect(paidTo(toOther)).toEqual([OTHER]);
            expect(detail(toOther, "Min. paid out").value).toBe(min);
        },
    );
});

describe("an output the router holds", () => {
    const toRouter = v3SwapExactIn(
        ADDRESS_THIS,
        USDT_2000,
        USDC_1990,
        USDT,
        USDC,
    );

    test("SWEEP pays it to the SWEEP's recipient", () => {
        const direct = decode(
            execute(
                v3SwapExactIn(MSG_SENDER, USDT_2000, USDC_1990, USDT, USDC),
            ),
        );
        const toUser = decode(execute(toRouter, sweep(USDC, MSG_SENDER)));
        expect(labels(toUser)).toEqual(PAID_TO_USER);
        const withoutSteps = (r) =>
            r.details.filter((d) => d.label !== "Steps");
        expect(withoutSteps(toUser)).toEqual(withoutSteps(direct));

        const toOther = decode(execute(toRouter, sweep(USDC, OTHER)));
        expect(labels(toOther)).toEqual(PAID_ELSEWHERE);
        expect(paidTo(toOther)).toEqual([OTHER]);
        expect(detail(toOther, "Min. paid out").value).toBe("1990.0000 USDC");
    });

    test("with nothing paying it out, it stays in the router", () => {
        const result = decode(execute(toRouter));
        expect(labels(result)).toEqual(PAID_ELSEWHERE);
        expect(paidTo(result)).toEqual([STAYS_IN_ROUTER]);
    });

    test("the router's own address as a recipient is read as address(2) is", () => {
        const toRouterAddress = v3SwapExactIn(
            ROUTER,
            USDT_2000,
            USDC_1990,
            USDT,
            USDC,
        );
        expect(paidTo(decode(execute(toRouterAddress)))).toEqual([
            STAYS_IN_ROUTER,
        ]);
        expect(
            labels(decode(execute(toRouterAddress, sweep(USDC, MSG_SENDER)))),
        ).toEqual(PAID_TO_USER);
    });

    test("UNWRAP_WETH pays its WETH, as ETH, to the UNWRAP_WETH's recipient", () => {
        const toWeth = swapToWeth(ADDRESS_THIS);

        const toUser = decode(execute(toWeth, unwrapWeth(MSG_SENDER)));
        expect(labels(toUser)).toEqual(PAID_TO_USER);
        expect(detail(toUser, "Token Out").value).toBe("ETH");
        expect(detail(toUser, "Min. received").value).toBe("1.0000 ETH");

        const toOther = decode(execute(toWeth, unwrapWeth(OTHER)));
        expect(labels(toOther)).toEqual(PAID_ELSEWHERE);
        expect(paidTo(toOther)).toEqual([OTHER]);
        expect(detail(toOther, "Min. paid out").value).toBe("1.0000 ETH");
    });

    test("WRAP_ETH pays its WETH to the WRAP_ETH's recipient", () => {
        const toUser = decode(
            execute(wrapEth(ADDRESS_THIS, ONE_WETH), unwrapWeth(MSG_SENDER)),
        );
        expect(detail(toUser, "Token Out").value).toBe("ETH");
        expect(paidTo(toUser)).toEqual([]);

        const toOther = decode(
            execute(wrapEth(OTHER, ONE_WETH), unwrapWeth(MSG_SENDER)),
        );
        expect(paidTo(toOther)).toEqual([OTHER]);
    });

    test("a V4 TAKE to the router, then SWEEP, pays the SWEEP's recipient", () => {
        const step = v4Swap(
            SWAP_USDT_FOR_USDC,
            SETTLE_USDT,
            take(USDC, ADDRESS_THIS),
        );

        const toUser = decode(execute(step, sweep(USDC, MSG_SENDER)));
        expect(labels(toUser)).toEqual(PAID_TO_USER);

        const toOther = decode(execute(step, sweep(USDC, OTHER)));
        expect(labels(toOther)).toEqual(PAID_ELSEWHERE);
        expect(paidTo(toOther)).toEqual([OTHER]);
    });
});

// Only a later SWEEP of the output token, or UNWRAP_WETH of WETH, pays the
// router's output out. A payment to the user of another token, of nothing, or
// before the swap leaves the output in the router.
describe("an output left in the router is not received", () => {
    const toRouter = swapToWeth(ADDRESS_THIS);

    test.each([
        {
            kind: "a SWEEP of WETH to the user, then the swap",
            data: execute(sweep(WETH, MSG_SENDER), toRouter),
            min: "1.0000 WETH",
        },
        {
            kind: "an UNWRAP_WETH to the user, then the swap",
            data: execute(unwrapWeth(MSG_SENDER), toRouter),
            min: "1.0000 ETH",
        },
        {
            kind: "the swap, then a WRAP_ETH of zero to the user",
            data: execute(toRouter, wrapEth(MSG_SENDER, 0n)),
            min: "1.0000 WETH",
        },
        {
            kind: "the swap, then a SWEEP of a token it does not buy to the user",
            data: execute(toRouter, sweep(USDC, MSG_SENDER)),
            min: "1.0000 WETH",
        },
    ])("$kind", ({ data, min }) => {
        const result = decode(data);
        expect(labels(result)).toEqual(PAID_ELSEWHERE);
        expect(paidTo(result)).toEqual([STAYS_IN_ROUTER]);
        expect(detail(result, "Min. paid out").value).toBe(min);
    });

    test("one V4 step: a TAKE of what it buys to the router, then a TAKE_ALL of it, which takes nothing", () => {
        const result = decode(
            execute(
                v4Swap(
                    SWAP_USDT_FOR_USDC,
                    SETTLE_USDT,
                    take(USDC, ADDRESS_THIS),
                    takeAll(USDC),
                ),
            ),
        );
        expect(detail(result, "Steps").value).toBe("V4 Swap");
        expect(labels(result)).toEqual(PAID_ELSEWHERE);
        expect(paidTo(result)).toEqual([STAYS_IN_ROUTER]);
        expect(detail(result, "Min. paid out").value).toBe("1990.0000 USDC");
    });
});

// https://git.eeqj.de/sneak/AutistMask/issues/599: TRANSFER, PAY_PORTION,
// PAY_PORTION_FULL_PRECISION and V4 TAKE_PORTION pay a token to an address,
// and PERMIT2_TRANSFER_FROM moves the user's own tokens to one.
describe("each transfer command's recipient", () => {
    // Each pays out all of a swap's output. Paid to another address, this is
    // the first shape the issue reports.
    test.each([
        {
            kind: "TRANSFER of CONTRACT_BALANCE",
            data: (r) =>
                execute(
                    swapToWeth(ADDRESS_THIS),
                    transfer(0x05, WETH, r, CONTRACT_BALANCE),
                ),
            min: "1.0000 WETH",
        },
        {
            kind: "PAY_PORTION of 10,000 bips",
            data: (r) =>
                execute(
                    swapToWeth(ADDRESS_THIS),
                    transfer(0x06, WETH, r, 10000n),
                ),
            min: "1.0000 WETH",
        },
        {
            kind: "PAY_PORTION_FULL_PRECISION of 1e18",
            data: (r) =>
                execute(
                    swapToWeth(ADDRESS_THIS),
                    transfer(0x07, WETH, r, 10n ** 18n),
                ),
            router: ROUTER_V2_1_2,
            min: "1.0000 WETH",
        },
        {
            kind: "V4 TAKE_PORTION of 10,000 bips",
            data: (r) =>
                execute(
                    v4Swap(
                        SWAP_USDT_FOR_USDC,
                        SETTLE_USDT,
                        takePortion(USDC, r, 10000n),
                    ),
                ),
            min: "1990.0000 USDC",
        },
    ])(
        "$kind: paid to the user it is received, to the router it stays there, to another address that address is named",
        ({ data, router = ROUTER, min }) => {
            const toUser = decode(data(MSG_SENDER), USER, router);
            expect(labels(toUser)).toEqual(PAID_TO_USER);
            expect(detail(toUser, "Min. received").value).toBe(min);
            expect(decode(data(USER), USER, router).details).toEqual(
                toUser.details,
            );

            const toRouter = decode(data(ADDRESS_THIS), USER, router);
            expect(labels(toRouter)).toEqual(PAID_ELSEWHERE);
            expect(paidTo(toRouter)).toEqual([STAYS_IN_ROUTER]);
            expect(detail(toRouter, "Min. paid out").value).toBe(min);

            const toOther = decode(data(OTHER), USER, router);
            expect(labels(toOther)).toEqual(PAID_ELSEWHERE);
            expect(paidTo(toOther)).toEqual([OTHER]);
            expect(detail(toOther, "Min. paid out").value).toBe(min);
        },
    );

    // The user's USDT, moved to `r`, then a swap of it paid to the user. A
    // move to another address is the issue's second shape.
    const movedThenSwapped = (r) =>
        execute(
            permit2TransferFrom(USDT, r, USDT_2000),
            v3SwapExactIn(MSG_SENDER, USDT_2000, ONE_WETH, USDT, WETH, false),
        );

    test("PERMIT2_TRANSFER_FROM: to the user it pays no one else, to another address that address is named", () => {
        for (const r of [MSG_SENDER, USER]) {
            const result = decode(movedThenSwapped(r));
            expect(labels(result)).toEqual(PAID_TO_USER);
            expect(detail(result, "Min. received").value).toBe("1.0000 WETH");
        }

        const toOther = decode(movedThenSwapped(OTHER));
        expect(labels(toOther)).toEqual(PAID_ELSEWHERE);
        expect(paidTo(toOther)).toEqual([OTHER]);
        expect(detail(toOther, "Min. paid out").value).toBe("1.0000 WETH");

        const alone = decode(
            execute(permit2TransferFrom(USDT, OTHER, USDT_2000)),
        );
        expect(detail(alone, "Steps").value).toBe("Permit2 Transfer");
        expect(paidTo(alone)).toEqual([OTHER]);
    });

    // Later steps may leave part of what a move into the router moves there,
    // where anyone can sweep it in a later transaction.
    test.each([
        { kind: "address(2)", r: ADDRESS_THIS },
        { kind: "the router's own address", r: ROUTER },
    ])(
        "PERMIT2_TRANSFER_FROM into the router as $kind names what it moves, and nothing is received",
        ({ r }) => {
            const result = decode(movedThenSwapped(r));
            expect(labels(result)).toEqual([
                "Protocol",
                "Token In",
                "Amount",
                "Token Out",
                "Paid to",
                "Token moved into the router",
                "Min. paid out",
                "Steps",
                "Deadline",
            ]);
            expect(paidTo(result)).toEqual([movedIntoRouter("2000.0000 USDT")]);
            expect(detail(result, "Token moved into the router")).toEqual({
                label: "Token moved into the router",
                value: "USDT (" + USDT + ")",
                address: USDT,
                isToken: true,
            });
            expect(detail(result, "Min. paid out").value).toBe("1.0000 WETH");
        },
    );

    test.each([
        { kind: "from the router's balance", payerIsUser: false },
        { kind: "from the user's", payerIsUser: true },
    ])(
        "a move of 2,000 USDT into the router, then a swap of 1 USDT $kind paid to the user",
        ({ payerIsUser }) => {
            const result = decode(
                execute(
                    permit2TransferFrom(USDT, ADDRESS_THIS, USDT_2000),
                    v3SwapExactIn(
                        MSG_SENDER,
                        1000000n,
                        1n,
                        USDT,
                        WETH,
                        payerIsUser,
                    ),
                ),
            );
            expect(detail(result, "Amount").value).toBe("1.0000 USDT");
            expect(paidTo(result)).toEqual([movedIntoRouter("2000.0000 USDT")]);
            expect(detail(result, "Min. received")).toBeUndefined();
            expect(detail(result, "Min. paid out")).toBeDefined();
        },
    );

    test("a move into the router of a token the wallet does not know gives the token's address", () => {
        const result = decode(
            execute(
                permit2TransferFrom(UNKNOWN_TOKEN, ADDRESS_THIS, 5n),
                swapToWeth(MSG_SENDER),
            ),
        );
        expect(paidTo(result)).toEqual([
            movedIntoRouter("5 base units (decimals unknown)"),
        ]);
        expect(detail(result, "Token moved into the router")).toEqual({
            label: "Token moved into the router",
            value: UNKNOWN_TOKEN,
            address: UNKNOWN_TOKEN,
            isToken: true,
        });
    });

    test("UniversalRouterV1 pays a PERMIT2_TRANSFER_FROM to address(1) or address(2) as written, and maps a TRANSFER's", () => {
        for (const r of [MSG_SENDER, ADDRESS_THIS]) {
            const result = decode(movedThenSwapped(r), USER, ROUTER_V1);
            expect(paidTo(result)).toEqual([r]);
            expect(detail(result, "Min. received")).toBeUndefined();
        }

        const transferred = decode(
            execute(
                swapToWeth(ADDRESS_THIS),
                transfer(0x05, WETH, MSG_SENDER, CONTRACT_BALANCE),
            ),
            USER,
            ROUTER_V1,
        );
        expect(labels(transferred)).toEqual(PAID_TO_USER);
    });

    test("TAKE_PORTION does not set Token Out: a TAKE_PORTION of another currency after the TAKE_ALL of the bought one", () => {
        const result = decode(
            execute(
                v4Swap(
                    SWAP_USDT_FOR_USDC,
                    SETTLE_USDT,
                    takeAll(USDC),
                    takePortion(USDT, OTHER, 25n),
                ),
            ),
        );
        expect(detail(result, "Token Out").address).toBe(USDC);
        expect(paidTo(result)).toEqual([OTHER]);
        expect(detail(result, "Min. paid out").value).toBe("1990.0000 USDC");
    });

    test("a router without command 0x07 does not read it as PAY_PORTION_FULL_PRECISION", () => {
        const result = decode(
            execute(
                swapToWeth(MSG_SENDER),
                transfer(0x07, WETH, MSG_SENDER, 10n ** 18n),
            ),
        );
        expect(detail(result, "Steps").value).toBe(
            "V3 Swap (Exact In) → Command 0x07",
        );
        expect(paidTo(result)).toEqual([UNDECODED]);
        expect(detail(result, "Min. received")).toBeUndefined();
    });
});

// A payout of only part of what the router holds leaves the rest there.
describe("a payout of part of the router's output", () => {
    test.each([
        {
            kind: "a TRANSFER of 1 base unit",
            step: transfer(0x05, WETH, MSG_SENDER, 1n),
        },
        {
            kind: "a PAY_PORTION of 5,000 bips",
            step: transfer(0x06, WETH, MSG_SENDER, 5000n),
        },
        {
            kind: "a PAY_PORTION_FULL_PRECISION of 1e18 less 1",
            step: transfer(0x07, WETH, MSG_SENDER, 10n ** 18n - 1n),
        },
    ])("$kind to the user leaves the rest in the router", ({ step }) => {
        const result = decode(
            execute(swapToWeth(ADDRESS_THIS), step),
            USER,
            ROUTER_V2_1_2,
        );
        expect(labels(result)).toEqual(PAID_ELSEWHERE);
        expect(paidTo(result)).toEqual([STAYS_IN_ROUTER]);
        expect(detail(result, "Min. paid out").value).toBe("1.0000 WETH");
    });

    // The router sends ETH as written, so a TRANSFER of CONTRACT_BALANCE of
    // ETH always reverts; PAY_PORTION reads the router's ETH balance.
    test("a TRANSFER of CONTRACT_BALANCE of ETH pays out nothing; a PAY_PORTION of 10,000 bips of ETH pays out all of it", () => {
        const ethToRouter = v4Swap(
            SWAP_USDT_FOR_ETH,
            SETTLE_USDT,
            take(ZERO, ADDRESS_THIS),
        );

        const transferred = decode(
            execute(
                ethToRouter,
                transfer(0x05, ZERO, MSG_SENDER, CONTRACT_BALANCE),
            ),
        );
        expect(detail(transferred, "Token Out").value).toBe("ETH");
        expect(paidTo(transferred)).toEqual([STAYS_IN_ROUTER]);
        expect(detail(transferred, "Min. received")).toBeUndefined();

        const portion = decode(
            execute(ethToRouter, transfer(0x06, ZERO, MSG_SENDER, 10000n)),
        );
        expect(labels(portion)).toEqual(PAID_TO_USER);
        expect(detail(portion, "Min. received").value).toBe("1.0000 ETH");
    });

    // An interface fee: a share of the output to another address, the rest
    // to the user. The swap's minimum includes the fee, so it is not what the
    // user receives.
    test.each([
        {
            kind: "PAY_PORTION of 25 bips, then SWEEP",
            data: execute(
                swapToWeth(ADDRESS_THIS),
                transfer(0x06, WETH, OTHER, 25n),
                sweep(WETH, MSG_SENDER),
            ),
            min: "1.0000 WETH",
        },
        {
            kind: "TRANSFER of a flat fee, then SWEEP",
            data: execute(
                swapToWeth(ADDRESS_THIS),
                transfer(0x05, WETH, OTHER, ONE_WETH / 400n),
                sweep(WETH, MSG_SENDER),
            ),
            min: "1.0000 WETH",
        },
        {
            kind: "PAY_PORTION of 25 bips, then UNWRAP_WETH",
            data: execute(
                swapToWeth(ADDRESS_THIS),
                transfer(0x06, WETH, OTHER, 25n),
                unwrapWeth(MSG_SENDER),
            ),
            min: "1.0000 ETH",
        },
        {
            kind: "V4 TAKE_PORTION of 25 bips, then TAKE_ALL",
            data: execute(
                v4Swap(
                    SWAP_USDT_FOR_USDC,
                    SETTLE_USDT,
                    takePortion(USDC, OTHER, 25n),
                    takeAll(USDC),
                ),
            ),
            min: "1990.0000 USDC",
        },
    ])(
        "a fee by $kind names the fee's recipient and calls nothing received",
        ({ data, min }) => {
            const result = decode(data);
            expect(labels(result)).toEqual(PAID_ELSEWHERE);
            expect(paidTo(result)).toEqual([OTHER]);
            expect(detail(result, "Min. paid out").value).toBe(min);
        },
    );
});

// ACROSS_V4_DEPOSIT_V3 hands the bridge what the router holds. The bridge
// pays the deposit's recipient on another network, and refunds a deposit
// nobody fills to its depositor; the router passes both on as written.
describe("a bridge deposit", () => {
    // A swap of 2,000 USDT for at least 1 WETH paid to the router, then a
    // deposit of all the router's WETH.
    const bridged = (depositor, recipient) =>
        execute(
            swapToWeth(ADDRESS_THIS),
            acrossDeposit(depositor, recipient, WETH, CONTRACT_BALANCE),
        );

    test.each([
        {
            kind: "the user is its recipient and its depositor",
            recipient: USER,
            depositor: USER,
            named: [],
        },
        {
            kind: "another address is its recipient",
            recipient: OTHER,
            depositor: USER,
            named: [OTHER],
        },
        {
            kind: "another address is its depositor",
            recipient: USER,
            depositor: OTHER,
            named: [OTHER],
        },
        {
            kind: "address(1) is its recipient and address(2) its depositor",
            recipient: MSG_SENDER,
            depositor: ADDRESS_THIS,
            named: [MSG_SENDER, ADDRESS_THIS],
        },
    ])(
        "when $kind, each that is not the user is named, and nothing is received",
        ({ recipient, depositor, named }) => {
            const result = decode(
                bridged(depositor, recipient),
                USER,
                ROUTER_V2_1_2,
            );
            expect(detail(result, "Steps").value).toBe(
                "V3 Swap (Exact In) → Across Bridge Deposit",
            );
            expect(paidTo(result)).toEqual([...named, PAID_TO_BRIDGE]);
            expect(detail(result, "Min. received")).toBeUndefined();
            expect(detail(result, "Min. paid out").value).toBe("1.0000 WETH");
        },
    );

    test("a deposit of part of the router's WETH leaves the rest there", () => {
        const result = decode(
            execute(
                swapToWeth(ADDRESS_THIS),
                acrossDeposit(USER, USER, WETH, ONE_WETH / 2n),
            ),
            USER,
            ROUTER_V2_1_2,
        );
        expect(paidTo(result)).toEqual([PAID_TO_BRIDGE, STAYS_IN_ROUTER]);
    });

    test("a deposit of all the router's ETH pays out the ETH it holds; one of all its WETH does not", () => {
        const ethToRouter = v4Swap(
            SWAP_USDT_FOR_ETH,
            SETTLE_USDT,
            take(ZERO, ADDRESS_THIS),
        );

        const native = decode(
            execute(
                ethToRouter,
                acrossDeposit(USER, USER, WETH, CONTRACT_BALANCE, true),
            ),
            USER,
            ROUTER_V2_1_2,
        );
        expect(detail(native, "Token Out").value).toBe("ETH");
        expect(paidTo(native)).toEqual([PAID_TO_BRIDGE]);

        const weth = decode(
            execute(
                ethToRouter,
                acrossDeposit(USER, USER, WETH, CONTRACT_BALANCE),
            ),
            USER,
            ROUTER_V2_1_2,
        );
        expect(paidTo(weth)).toEqual([PAID_TO_BRIDGE, STAYS_IN_ROUTER]);
    });
});

// Uniswap's mixed routes pay a V2 pair directly when the next step swaps
// through it. That V2 swap spends what the pair holds: its amountIn is
// CONTRACT_BALANCE, paid from the router, or ALREADY_PAID. The pairs below
// are the addresses the routers find for the first two tokens of that V2
// swap's path.
describe("a swap paid to the pair the next V2 swap spends", () => {
    // The WETH/USDC pair on Ethereum Mainnet, as its V2 factory reports it.
    const PAIR = "0xB4e16d0168e52d35CaCD2c6185b44281Ec28C9Dc";
    const AMOUNTS_IN = [
        { kind: "CONTRACT_BALANCE", amountIn: CONTRACT_BALANCE },
        { kind: "ALREADY_PAID", amountIn: 0n },
    ];
    const swapTo = (recipient) =>
        v3SwapExactIn(recipient, USDT_2000, 0n, USDT, WETH);
    const swapToPair = swapTo(PAIR);
    const pairSpends = (amountIn, path) =>
        v2Swap(0x08, MSG_SENDER, amountIn, USDC_1990, path, false);

    test.each(AMOUNTS_IN)(
        "a V3 swap, then a V2 swap whose amountIn is $kind, reads as a swap paid to the user",
        ({ amountIn }) => {
            const result = decode(
                execute(swapToPair, pairSpends(amountIn, [WETH, USDC])),
            );
            expect(result.name).toBe("Swap USDT → USDC");
            expect(labels(result)).toEqual(PAID_TO_USER);
            expect(detail(result, "Amount").value).toBe("2000.0000 USDT");
            expect(detail(result, "Min. received").value).toBe(
                "1990.0000 USDC",
            );
        },
    );

    test.each(AMOUNTS_IN)(
        "a V3 swap paid to another address, then a V2 swap whose amountIn is $kind, names that address",
        ({ amountIn }) => {
            const result = decode(
                execute(swapTo(OTHER), pairSpends(amountIn, [WETH, USDC])),
            );
            expect(labels(result)).toEqual(PAID_ELSEWHERE);
            expect(paidTo(result)).toEqual([OTHER]);
            expect(detail(result, "Min. paid out").value).toBe(
                "1990.0000 USDC",
            );
        },
    );

    test.each([
        { recipient: PAIR, lines: PAID_TO_USER, paid: [] },
        { recipient: OTHER, lines: PAID_ELSEWHERE, paid: [OTHER] },
    ])(
        "a V4 step whose TAKE pays $recipient, then the V2 swap",
        ({ recipient, lines, paid }) => {
            const result = decode(
                execute(
                    v4Swap(
                        SWAP_USDT_FOR_USDC,
                        SETTLE_USDT,
                        take(USDC, recipient),
                    ),
                    v2Swap(
                        0x08,
                        MSG_SENDER,
                        CONTRACT_BALANCE,
                        ONE_WETH,
                        [USDC, WETH],
                        false,
                    ),
                ),
            );
            expect(labels(result)).toEqual(lines);
            expect(paidTo(result)).toEqual(paid);
        },
    );

    test.each([
        {
            kind: "ETH wrapped into the router, then a TRANSFER of all of it",
            pay: (r) => [
                wrapEth(ADDRESS_THIS, ONE_WETH),
                transfer(0x05, WETH, r, CONTRACT_BALANCE),
            ],
        },
        {
            kind: "a PERMIT2_TRANSFER_FROM of the user's WETH",
            pay: (r) => [permit2TransferFrom(WETH, r, ONE_WETH)],
        },
    ])(
        "$kind, paid to the pair, is a hop; paid to another address, it is named",
        ({ pay }) => {
            const route = (r) =>
                execute(...pay(r), pairSpends(0n, [WETH, USDC]));

            const toPair = decode(route(PAIR));
            expect(paidTo(toPair)).toEqual([]);
            expect(detail(toPair, "Min. received").value).toBe(
                "1990.0000 USDC",
            );

            const toOther = decode(route(OTHER));
            expect(paidTo(toOther)).toEqual([OTHER]);
            expect(detail(toOther, "Min. received")).toBeUndefined();
        },
    );

    describe("on Sepolia", () => {
        const SEPOLIA = "0xaa36a7";
        // UniversalRouterV2_1_2 on Sepolia.
        const SEPOLIA_ROUTER = "0x7E4f6c5e954Da5c61B3423D81E2277431Ac043f3";
        // The WETH/USDC pair the routers on Sepolia find. Sepolia's V2
        // factory reports another address for it, and no contract sits at
        // this one (see V2_FACTORIES in src/shared/uniswap.js).
        const SEPOLIA_PAIR = "0x541b50d32B73E769ac42F0FddD86D15FcAa861Fb";
        const SEPOLIA_UNI = "0x1f9840a85d5aF5bf1D1762F925BDADdC4201F984";
        const SEPOLIA_WETH = "0xfFf9976782d46CC05630D1f6eBAb18b2324d6B14";
        const SEPOLIA_USDC = "0x1c7D4B196Cb0C7B01d743Fbc6116a902379C7238";
        // UNI for WETH, paid to `recipient`, then WETH for USDC through the
        // pair.
        const route = (recipient, amountIn) =>
            execute(
                v3SwapExactIn(
                    recipient,
                    ONE_WETH,
                    0n,
                    SEPOLIA_UNI,
                    SEPOLIA_WETH,
                ),
                v2Swap(
                    0x08,
                    MSG_SENDER,
                    amountIn,
                    USDC_1990,
                    [SEPOLIA_WETH, SEPOLIA_USDC],
                    false,
                ),
            );

        test.each(AMOUNTS_IN)(
            "paid to the pair, then a V2 swap whose amountIn is $kind, reads as a swap paid to the user",
            ({ amountIn }) => {
                const result = uniswap.decode(
                    route(SEPOLIA_PAIR, amountIn),
                    SEPOLIA_ROUTER,
                    SEPOLIA,
                    {},
                    USER,
                );
                expect(labels(result)).toEqual(PAID_TO_USER);
            },
        );

        test.each(AMOUNTS_IN)(
            "paid to another address, then a V2 swap whose amountIn is $kind, names that address",
            ({ amountIn }) => {
                const result = uniswap.decode(
                    route(OTHER, amountIn),
                    SEPOLIA_ROUTER,
                    SEPOLIA,
                    {},
                    USER,
                );
                expect(labels(result)).toEqual(PAID_ELSEWHERE);
                expect(paidTo(result)).toEqual([OTHER]);
            },
        );

        test("the same route on Ethereum Mainnet names the Sepolia pair", () => {
            const result = decode(route(SEPOLIA_PAIR, 0n));
            expect(paidTo(result)).toEqual([SEPOLIA_PAIR]);
        });
    });

    test.each([
        {
            kind: "takes its input from the user",
            next: v2Swap(0x08, MSG_SENDER, ONE_WETH, USDC_1990, [WETH, USDC]),
        },
        {
            kind: "spends another token",
            next: pairSpends(0n, [USDC, WETH]),
        },
    ])("when the V2 swap $kind, the pair is named", ({ next }) => {
        const result = decode(execute(swapToPair, next));
        expect(paidTo(result)).toEqual([PAIR]);
        expect(detail(result, "Min. received")).toBeUndefined();
    });
});

describe("every step's payee counts, whichever step sets the output", () => {
    test("TAKE_ALL pays the user; a TAKE to another address beside it is named", () => {
        const toUser = decode(
            execute(v4Swap(SWAP_USDT_FOR_USDC, SETTLE_USDT, takeAll(USDC))),
        );
        expect(labels(toUser)).toEqual(PAID_TO_USER);

        // TAKE with an amount of zero takes the whole open credit, so
        // TAKE_ALL after it pays the user nothing.
        const split = decode(
            execute(
                v4Swap(
                    SWAP_USDT_FOR_USDC,
                    SETTLE_USDT,
                    take(USDC, OTHER),
                    takeAll(USDC),
                ),
            ),
        );
        expect(paidTo(split)).toEqual([OTHER]);
        expect(detail(split, "Min. received")).toBeUndefined();
        expect(detail(split, "Min. paid out").value).toBe("1990.0000 USDC");
    });

    test("a swap paid to another address, then a V4 step that only takes the same token", () => {
        const emptyStep = v4Swap(takeAll(WETH));

        const result = decode(execute(swapToWeth(OTHER), emptyStep));
        expect(paidTo(result)).toEqual([OTHER]);
        expect(detail(result, "Min. received")).toBeUndefined();

        const checked = decode(
            execute(swapToWeth(OTHER), emptyStep, balanceCheck(WETH, ONE_WETH)),
        );
        expect(paidTo(checked)).toEqual([OTHER]);
        expect(detail(checked, "Min. received")).toBeUndefined();
        expect(detail(checked, "Min. paid out").value).toBe("1.0000 WETH");
    });

    test("a swap paid to the router, a V4 step that only takes, then SWEEP to another address", () => {
        const result = decode(
            execute(
                v3SwapExactIn(ADDRESS_THIS, USDT_2000, USDC_1990, USDT, USDC),
                v4Swap(takeAll(USDC)),
                sweep(USDC, OTHER),
            ),
        );
        expect(paidTo(result)).toEqual([OTHER]);
        expect(detail(result, "Min. received")).toBeUndefined();
    });

    test("a swap paid to another address, then a small swap paid to the user", () => {
        const result = decode(
            execute(
                swapToWeth(OTHER),
                v2Swap(0x08, MSG_SENDER, 1000000n, 1n, [USDT, WETH]),
            ),
        );
        expect(paidTo(result)).toEqual([OTHER]);
        expect(detail(result, "Min. received")).toBeUndefined();
        expect(detail(result, "Min. paid out")).toBeDefined();
    });

    test("one V4 step: a TAKE of what it buys to another address, then TAKE_ALL of another currency", () => {
        const result = decode(
            execute(
                v4Swap(
                    SWAP_USDT_FOR_USDC,
                    SETTLE_USDT,
                    take(USDC, OTHER),
                    takeAll(USDT),
                ),
            ),
        );
        expect(paidTo(result)).toEqual([OTHER]);
        expect(detail(result, "Min. received")).toBeUndefined();
    });
});

describe("a payout that cannot be read is never said to be received", () => {
    test.each([
        { kind: "TAKE", action: take(USDC, OTHER) },
        { kind: "TAKE_PORTION", action: takePortion(USDC, OTHER, 25n) },
    ])("a V4 $kind whose recipient word has its top byte set", ({ action }) => {
        const result = decode(
            execute(
                v4Swap(
                    SWAP_USDT_FOR_USDC,
                    SETTLE_USDT,
                    withDirtyWord(action, 1),
                    takeAll(USDC),
                ),
            ),
        );
        expect(paidTo(result)).toEqual([UNDECODED]);
        expect(detail(result, "Min. received")).toBeUndefined();
        expect(detail(result, "Min. paid out").value).toBe("1990.0000 USDC");
    });

    test.each([
        {
            kind: "V2_SWAP_EXACT_IN",
            step: v2Swap(0x08, OTHER, 1n, 1n, [USDT, WETH]),
        },
        {
            kind: "V2_SWAP_EXACT_OUT",
            step: v2Swap(0x09, OTHER, 1n, 1n, [USDT, WETH]),
        },
        { kind: "V3_SWAP_EXACT_IN", step: swapToWeth(OTHER) },
        { kind: "SWEEP", step: sweep(WETH, OTHER), word: 1 },
        { kind: "WRAP_ETH", step: wrapEth(OTHER, 1n) },
        { kind: "UNWRAP_WETH", step: unwrapWeth(OTHER) },
        {
            kind: "TRANSFER",
            step: transfer(0x05, WETH, OTHER, 1n),
            word: 1,
        },
        {
            kind: "PAY_PORTION",
            step: transfer(0x06, WETH, OTHER, 1n),
            word: 1,
        },
        {
            kind: "PAY_PORTION_FULL_PRECISION",
            step: transfer(0x07, WETH, OTHER, 1n),
            word: 1,
        },
        {
            kind: "PERMIT2_TRANSFER_FROM",
            step: permit2TransferFrom(WETH, OTHER, 1n),
            word: 1,
        },
        {
            kind: "ACROSS_V4_DEPOSIT_V3",
            step: acrossDeposit(USER, OTHER, WETH, 1n),
            word: 2,
        },
    ])(
        "a $kind whose recipient word has its top byte set",
        ({ step, word = 0 }) => {
            const result = decode(
                execute(swapToWeth(MSG_SENDER), withDirtyWord(step, word)),
                USER,
                ROUTER_V2_1_2,
            );
            expect(paidTo(result)).toEqual([UNDECODED]);
            expect(detail(result, "Min. received")).toBeUndefined();
            expect(detail(result, "Min. paid out")).toBeDefined();
        },
    );

    // The router reads only the low 32 bits of the action list's length, so
    // the step still runs, and may pay anyone.
    test("a V4_SWAP whose action list's length word has its top byte set", () => {
        const step = v4Swap(SWAP_USDT_FOR_USDC, SETTLE_USDT, take(USDC, OTHER));
        const result = decode(
            execute(swapToWeth(MSG_SENDER), withDirtyWord(step, 2)),
        );
        expect(paidTo(result)).toEqual([UNDECODED]);
        expect(detail(result, "Min. paid out").value).toBe("1.0000 WETH");
    });

    test("an output set only by BALANCE_CHECK_ERC20", () => {
        const result = decode(execute(balanceCheck(WETH, ONE_WETH)));
        expect(paidTo(result)).toEqual([UNNAMED]);
        expect(detail(result, "Min. received")).toBeUndefined();
        expect(detail(result, "Min. paid out").value).toBe("1.0000 WETH");
    });

    // Each is a payout this decoder does not read.
    test.each([
        {
            kind: "PERMIT2_TRANSFER_FROM_BATCH",
            step: [
                0x0d,
                coder.encode(
                    ["tuple(address,address,uint160,address)[]"],
                    [[[USER, OTHER, 1n, WETH]]],
                ),
            ],
        },
        {
            kind: "V3_SWAP_EXACT_OUT",
            step: [0x01, swapToWeth(OTHER)[1]],
        },
        {
            kind: "EXECUTE_SUB_PLAN",
            step: [
                0x21,
                coder.encode(
                    ["bytes", "bytes[]"],
                    ["0x05", [transfer(0x05, WETH, OTHER, 1n)[1]]],
                ),
            ],
        },
    ])("a swap paid to the user, then $kind", ({ step }) => {
        const result = decode(
            execute(swapToWeth(MSG_SENDER), step),
            USER,
            ROUTER_V2_1_2,
        );
        expect(paidTo(result)).toEqual([UNDECODED]);
        expect(detail(result, "Min. received")).toBeUndefined();
    });
});

describe("paths whose recipients were untested", () => {
    test("BALANCE_CHECK_ERC20 after a swap leaves who is paid as the swap says", () => {
        const check = balanceCheck(WETH, ONE_WETH);

        const toUser = decode(execute(swapToWeth(MSG_SENDER), check));
        expect(paidTo(toUser)).toEqual([]);
        expect(detail(toUser, "Min. received").value).toBe("1.0000 WETH");

        const toOther = decode(execute(swapToWeth(OTHER), check));
        expect(paidTo(toOther)).toEqual([OTHER]);
        expect(detail(toOther, "Min. paid out").value).toBe("1.0000 WETH");
    });

    test("a V4 step whose swap action cannot be read still has its TAKE read", () => {
        const step = (r) => v4Swap(UNREADABLE_SWAP, SETTLE_USDT, take(USDC, r));

        const toUser = decode(execute(step(MSG_SENDER)));
        expect(detail(toUser, "Steps").value).toBe(
            "V4 Swap (could not be decoded)",
        );
        expect(paidTo(toUser)).toEqual([]);

        expect(paidTo(decode(execute(step(OTHER))))).toEqual([OTHER]);
    });
});

// https://git.eeqj.de/sneak/AutistMask/issues/602: the top bit of a command
// byte (0x80) is the allow-revert flag. The router lets a step with it fail
// and goes on to the next step only for some commands, none of them a swap or
// a payment; on every other command the flag has no effect.
describe("the allow-revert flag", () => {
    // UniversalRouterV1_2_V2Support on Ethereum Mainnet.
    const ROUTER_V1_2 = "0x3fC91A3afd70395Cd496C647d5a6CC9D4B2b7FAD";
    // UniversalRouterV2_1_1 on Ethereum Mainnet.
    const ROUTER_V2_1_1 = "0x4C82D1fBFe28C977cBB58D8C7FF8FCF9F70a2cCA";
    // The WETH/USDC pair on Ethereum Mainnet, as its V2 factory reports it.
    const PAIR = "0xB4e16d0168e52d35CaCD2c6185b44281Ec28C9Dc";

    // `step` with the allow-revert flag set on its command byte.
    const flagged = ([command, input]) => [command | 0x80, input];
    // `steps` with the flag set on the one at `index`.
    const flagStep = (steps, index) =>
        steps.map((s, i) => (i === index ? flagged(s) : s));

    const usdcToRouter = v3SwapExactIn(
        ADDRESS_THIS,
        USDT_2000,
        USDC_1990,
        USDT,
        USDC,
    );
    const wethToPair = v3SwapExactIn(PAIR, USDT_2000, 0n, USDT, WETH);
    const pairSpends = v2Swap(
        0x08,
        MSG_SENDER,
        0n,
        USDC_1990,
        [WETH, USDC],
        false,
    );

    // The flag is set on the step at `index`: a swap, a payment, or the V2
    // swap that a payment to its pair hops into.
    test.each([
        {
            kind: "V2_SWAP_EXACT_IN",
            steps: [
                v2Swap(0x08, MSG_SENDER, USDT_2000, ONE_WETH, [USDT, WETH]),
            ],
            index: 0,
        },
        {
            kind: "V2_SWAP_EXACT_OUT",
            steps: [
                v2Swap(0x09, MSG_SENDER, ONE_WETH, USDT_2000, [USDT, WETH]),
            ],
            index: 0,
        },
        {
            kind: "V3_SWAP_EXACT_IN",
            steps: [swapToWeth(MSG_SENDER)],
            index: 0,
        },
        {
            kind: "V4_SWAP",
            steps: [v4Swap(SWAP_USDT_FOR_USDC, SETTLE_USDT, takeAll(USDC))],
            index: 0,
        },
        {
            kind: "SWEEP",
            steps: [usdcToRouter, sweep(USDC, MSG_SENDER)],
            index: 1,
        },
        {
            kind: "TRANSFER",
            steps: [
                usdcToRouter,
                transfer(0x05, USDC, MSG_SENDER, CONTRACT_BALANCE),
            ],
            index: 1,
        },
        {
            kind: "PAY_PORTION",
            steps: [usdcToRouter, transfer(0x06, USDC, MSG_SENDER, 10000n)],
            index: 1,
        },
        {
            kind: "PAY_PORTION_FULL_PRECISION",
            steps: [usdcToRouter, transfer(0x07, USDC, MSG_SENDER, 10n ** 18n)],
            index: 1,
        },
        {
            kind: "UNWRAP_WETH",
            steps: [swapToWeth(ADDRESS_THIS), unwrapWeth(MSG_SENDER)],
            index: 1,
        },
        {
            kind: "WRAP_ETH",
            steps: [
                wrapEth(ADDRESS_THIS, ONE_WETH),
                v3SwapExactIn(
                    MSG_SENDER,
                    ONE_WETH,
                    USDC_1990,
                    WETH,
                    USDC,
                    false,
                ),
            ],
            index: 0,
        },
        {
            kind: "ACROSS_V4_DEPOSIT_V3",
            steps: [
                usdcToRouter,
                acrossDeposit(USER, USER, USDC, CONTRACT_BALANCE),
            ],
            index: 1,
        },
        {
            kind: "PERMIT2_TRANSFER_FROM to the pair the next V2 swap spends",
            steps: [permit2TransferFrom(WETH, PAIR, ONE_WETH), pairSpends],
            index: 0,
        },
        {
            kind: "a swap paid to the pair the next V2 swap spends",
            steps: [wethToPair, pairSpends],
            index: 0,
        },
        {
            kind: "the V2 swap after a swap paid to its pair",
            steps: [wethToPair, pairSpends],
            index: 1,
        },
    ])(
        "$kind reads the same with the flag as without it",
        ({ steps, index }) => {
            const plain = decode(execute(...steps), USER, ROUTER_V2_1_2);
            const withFlag = decode(
                execute(...flagStep(steps, index)),
                USER,
                ROUTER_V2_1_2,
            );
            expect(withFlag).toEqual(plain);
            expect(detail(withFlag, "Steps").value).not.toContain(
                "allowed to fail",
            );
        },
    );

    test.each([
        { router: "UniversalRouterV1_2_V2Support", address: ROUTER_V1_2 },
        { router: "UniversalRouterV2", address: ROUTER },
        { router: "UniversalRouterV2_1_2", address: ROUTER_V2_1_2 },
    ])(
        "on $router, a BALANCE_CHECK_ERC20 with the flag is allowed to fail and does not replace the swap's minimum",
        ({ address }) => {
            const check = balanceCheck(WETH, 2n * ONE_WETH);

            const plain = decode(
                execute(swapToWeth(MSG_SENDER), check),
                USER,
                address,
            );
            expect(detail(plain, "Steps").value).toBe(
                "V3 Swap (Exact In) → Balance Check",
            );
            expect(detail(plain, "Min. received").value).toBe("2.0000 WETH");

            const withFlag = decode(
                execute(swapToWeth(MSG_SENDER), flagged(check)),
                USER,
                address,
            );
            expect(detail(withFlag, "Steps").value).toBe(
                "V3 Swap (Exact In) → Balance Check (allowed to fail)",
            );
            expect(detail(withFlag, "Min. received").value).toBe("1.0000 WETH");
        },
    );

    test("a BALANCE_CHECK_ERC20 with the flag, and no minimum before it, states none", () => {
        const check = balanceCheck(WETH, ONE_WETH);
        expect(detail(decode(execute(check)), "Min. paid out").value).toBe(
            "1.0000 WETH",
        );

        const withFlag = decode(execute(flagged(check)));
        expect(detail(withFlag, "Token Out").address).toBe(WETH);
        expect(detail(withFlag, "Min. paid out").value).toBe(
            "None (no minimum guaranteed)",
        );
    });

    // On these two routers 0x10 is an NFT market call the router lets fail,
    // still read as a V4 swap
    // (https://git.eeqj.de/sneak/AutistMask/issues/592).
    test.each([
        { router: "UniversalRouterV1", address: ROUTER_V1 },
        { router: "UniversalRouterV1_2_V2Support", address: ROUTER_V1_2 },
    ])(
        "on $router, a V4_SWAP with the flag is allowed to fail and states no minimum",
        ({ address }) => {
            const step = v4Swap(SWAP_USDT_FOR_USDC, SETTLE_USDT, takeAll(USDC));

            const plain = decode(execute(step), USER, address);
            expect(detail(plain, "Steps").value).toBe("V4 Swap");
            expect(detail(plain, "Min. received").value).toBe("1990.0000 USDC");

            const withFlag = decode(execute(flagged(step)), USER, address);
            expect(detail(withFlag, "Steps").value).toBe(
                "V4 Swap (allowed to fail)",
            );
            expect(detail(withFlag, "Token Out").address).toBe(USDC);
            expect(detail(withFlag, "Min. received").value).toBe(
                "None (no minimum guaranteed)",
            );
        },
    );

    // Only the routers from UniversalRouterV2 on let a PERMIT2_PERMIT fail.
    test.each([
        { router: "UniversalRouterV1", address: ROUTER_V1, mark: "" },
        {
            router: "UniversalRouterV1_2_V2Support",
            address: ROUTER_V1_2,
            mark: "",
        },
        {
            router: "UniversalRouterV2",
            address: ROUTER,
            mark: " (allowed to fail)",
        },
        {
            router: "UniversalRouterV2_1_2",
            address: ROUTER_V2_1_2,
            mark: " (allowed to fail)",
        },
    ])(
        "on $router, a PERMIT2_PERMIT with the flag is listed as 'Permit2 Permit$mark', and the swap reads as without the flag",
        ({ address, mark }) => {
            const steps = [
                permit2Permit(USDT, USDT_2000),
                swapToWeth(MSG_SENDER),
            ];
            const plain = decode(execute(...steps), USER, address);
            const withFlag = decode(
                execute(...flagStep(steps, 0)),
                USER,
                address,
            );
            expect(detail(withFlag, "Steps").value).toBe(
                "Permit2 Permit" + mark + " → V3 Swap (Exact In)",
            );
            const withoutSteps = (r) =>
                r.details.filter((d) => d.label !== "Steps");
            expect(withoutSteps(withFlag)).toEqual(withoutSteps(plain));
            expect(detail(withFlag, "Min. received").value).toBe("1.0000 WETH");
        },
    );

    test("a step the decoder does not read is marked too", () => {
        const positionManagerCall = [0x12, "0x"];
        const plain = decode(
            execute(swapToWeth(MSG_SENDER), positionManagerCall),
        );
        expect(detail(plain, "Steps").value).toBe(
            "V3 Swap (Exact In) → V3 Position Mgr Call",
        );

        const withFlag = decode(
            execute(swapToWeth(MSG_SENDER), flagged(positionManagerCall)),
        );
        expect(detail(withFlag, "Steps").value).toBe(
            "V3 Swap (Exact In) → V3 Position Mgr Call (allowed to fail)",
        );
        expect(paidTo(withFlag)).toEqual([UNDECODED]);
    });

    // A command from each router's list, by its name in that release's
    // Commands.sol.
    test.each([
        {
            router: "UniversalRouterV1",
            address: ROUTER_V1,
            command: "FOUNDATION",
            id: 0x1c,
            name: "Command 0x1c",
        },
        {
            router: "UniversalRouterV1_2_V2Support",
            address: ROUTER_V1_2,
            command: "ELEMENT_MARKET",
            id: 0x1e,
            name: "Command 0x1e",
        },
        {
            router: "UniversalRouterV2",
            address: ROUTER,
            command: "PERMIT2_PERMIT_BATCH",
            id: 0x03,
            name: "Permit2 Permit Batch",
        },
        {
            router: "UniversalRouterV2_1_1",
            address: ROUTER_V2_1_1,
            command: "V4_INITIALIZE_POOL",
            id: 0x13,
            name: "V4 Initialize Pool",
        },
        {
            router: "UniversalRouterV2_1_2",
            address: ROUTER_V2_1_2,
            command: "V4_POSITION_MANAGER_CALL",
            id: 0x14,
            name: "V4 Position Mgr Call",
        },
    ])(
        "on $router, $command with the flag is listed as '$name (allowed to fail)'",
        ({ address, id, name }) => {
            const step = [id, "0x"];
            const plain = decode(
                execute(swapToWeth(MSG_SENDER), step),
                USER,
                address,
            );
            expect(detail(plain, "Steps").value).toBe(
                "V3 Swap (Exact In) → " + name,
            );

            const withFlag = decode(
                execute(swapToWeth(MSG_SENDER), flagged(step)),
                USER,
                address,
            );
            expect(detail(withFlag, "Steps").value).toBe(
                "V3 Swap (Exact In) → " + name + " (allowed to fail)",
            );
        },
    );
});

// The DOM stub both screens are drawn into.
function makeElement(id) {
    const classes = new Set();
    const el = {
        id,
        textContent: "",
        value: "",
        innerHTML: "",
        style: {},
        dataset: {},
        classList: {
            add: (...names) => names.forEach((n) => classes.add(n)),
            remove: (...names) => names.forEach((n) => classes.delete(n)),
            contains: (n) => classes.has(n),
            toggle: () => false,
        },
        addEventListener: () => {},
        querySelectorAll: () => [],
        appendChild: () => {},
    };
    Object.defineProperty(el, "parentElement", {
        get: () => node(id + "-parent"),
    });
    return el;
}

function makeDocument() {
    const els = new Map();
    return {
        getElementById(id) {
            if (id === "debug-banner") return null;
            if (!els.has(id)) els.set(id, makeElement(id));
            return els.get(id);
        },
        createElement: () => makeElement("created"),
        body: { prepend: () => {} },
    };
}

function node(id) {
    return globalThis.document.getElementById(id);
}

// A swap of 2,000 USDT for at least 1 WETH, paid to `recipient`.
const swapPaidTo = (recipient) => execute(swapToWeth(recipient));

// Open the approval screen for a transaction from USER sending `data` to the
// router.
async function showApproval(data) {
    globalThis.document = makeDocument();
    globalThis.window = { location: { search: "" }, close: () => {} };
    globalThis.chrome.runtime = {
        connect: () => ({ postMessage: () => {} }),
        sendMessage: (_msg, reply) =>
            reply({
                type: "tx",
                origin: "https://dapp.example",
                isPhishingDomain: false,
                approvedFrom: USER,
                approvedTx: {
                    type: 2,
                    from: USER,
                    chainId: "0x1",
                    nonce: "0x7",
                    gasLimit: "0x30d40",
                    maxPriorityFeePerGas: "0x3b9aca00",
                    maxFeePerGas: "0x77359400",
                    to: ROUTER,
                    value: "0x0",
                    data,
                    accessList: [],
                },
            }),
    };
    state.networkId = "mainnet";
    state.currentView = null;
    await approval.show(1);
    return node("approve-tx-decoded-details").innerHTML;
}

// The transaction the explorer reports: from USER, sending `mockSentData` to
// the router.
const TX_HASH = "0x" + "5".repeat(64);
let mockSentData = null;

function mockExplorerAnswer(url) {
    if (url.endsWith("/transactions/" + TX_HASH)) {
        return {
            from: { hash: USER },
            to: { hash: ROUTER },
            raw_input: mockSentData,
            method: "execute",
        };
    }
    return {};
}

// Open the transaction detail screen for that transaction, sending `data`.
async function showDetail(data) {
    mockSentData = data;
    globalThis.document = makeDocument();
    globalThis.window = { location: { search: "" } };
    state.networkId = "mainnet";
    state.blockscoutUrl = "https://explorer.example/api/v2";
    state.viewData = {};
    state.viewStack = [];
    state.currentView = null;
    transactionDetail.show({
        hash: TX_HASH,
        from: USER,
        to: ROUTER,
        value: "",
        symbol: "ETH",
        timestamp: 1790000000,
        isError: false,
        direction: "contract",
        directionLabel: "Swap",
        method: "execute",
        chainId: "0x1",
    });
    for (let i = 0; i < 10; i++) await new Promise((r) => setTimeout(r, 0));
    return node("tx-detail-calldata-details").innerHTML;
}

describe("the screens judge the output against the transaction's sender", () => {
    test("the approval screen, against its From address", async () => {
        const toUser = await showApproval(swapPaidTo(USER));
        expect(toUser).toContain("Min. received");
        expect(toUser).not.toContain("Paid to");

        const toOther = await showApproval(swapPaidTo(OTHER));
        expect(toOther).toContain("Paid to");
        expect(toOther).toContain(OTHER);
        expect(toOther).not.toContain("Min. received");
    });

    test("the transaction detail screen, against the sender the explorer reports", async () => {
        const toUser = await showDetail(swapPaidTo(USER));
        expect(toUser).toContain("Min. received");
        expect(toUser).not.toContain("Paid to");

        const toOther = await showDetail(swapPaidTo(OTHER));
        expect(toOther).toContain("Paid to");
        expect(toOther).not.toContain("Min. received");
    });
});

// The address of each token moved into the router, a known one and one the
// wallet does not know, is shown as every other address is: with an explorer
// link, and copied when clicked. Neither token is the swap's.
describe("the screens show each token moved into the router as an address", () => {
    const twoMovesThenSwap = execute(
        permit2TransferFrom(USDC, ADDRESS_THIS, USDC_1990),
        permit2TransferFrom(UNKNOWN_TOKEN, ADDRESS_THIS, 5n),
        swapToWeth(MSG_SENDER),
    );

    test.each([
        { screen: "approval", show: showApproval },
        { screen: "transaction detail", show: showDetail },
    ])("the $screen screen", async ({ show }) => {
        const html = await show(twoMovesThenSwap);
        for (const token of [USDC, UNKNOWN_TOKEN]) {
            expect(html).toContain('data-copy="' + token + '"');
            expect(html).toContain("/address/" + token + '"');
        }
    });
});