/**
 * Tests for fresh reads (issue #75, an owner amendment to design #36).
 *
 * The default read namespaces answer from RAM and never touch the network; a
 * background loop keeps the local copy current. `fresh()` adds an awaited path:
 * it forces a refresh, waits for it to complete and persist, and only then
 * hands back the `albums`/`photos`/`timeline` namespaces, guaranteeing the
 * local copy reflects a completed server round-trip. The contracts here:
 *
 *  1. A fresh read observes a server change that a same-instant default read
 *     would miss (the default path has not refreshed yet).
 *  2. Concurrent fresh reads coalesce onto one in-flight refresh — three
 *     concurrent `fresh()` calls make exactly one collections round-trip, not
 *     three.
 *  3. A refresh that fails rejects the fresh read (currency was unavailable),
 *     while the default reads stay silent and keep serving the last good copy.
 *
 * The client is the same metadata-only mock the background-refresh tests use:
 * no crypto, no network, scripted pages, and a record of each call. A long
 * refresh interval keeps the background timer out of the way so each test's
 * refreshes are exactly the ones it triggers.
 */

import { describe, it, expect, beforeEach, afterEach } from "vitest";
import { mkdtempSync, rmSync } from "node:fs";
import { tmpdir } from "node:os";
import { join } from "node:path";

import { Library } from "../../src/library/index.js";
import type { CollectionsPage, FilesPage } from "../../src/client.js";
import type { Collection, EnteFile } from "../../src/model/types.js";

const USER_ID = 42;

// Long enough that no background tick fires during a test; each test's
// refreshes are only the ones its own `fresh()` calls force.
const SLOW_INTERVAL = 3600;

const collection = (id: number, updationTime: number): Collection => ({
    id,
    ownerID: USER_ID,
    key: new Uint8Array([id & 0xff]),
    name: `album-${id}`,
    type: "album",
    updationTime,
    isShared: false,
});

const file = (
    id: number,
    collectionID: number,
    updationTime: number,
): EnteFile => ({
    id,
    collectionID,
    ownerID: USER_ID,
    key: new Uint8Array([id & 0xff]),
    metadata: {
        title: `file-${id}.jpg`,
        fileType: "image",
        creationTime: updationTime,
        modificationTime: updationTime,
    },
    file: { decryptionHeader: "aGVhZGVy" },
    thumbnail: { decryptionHeader: "dGh1bWI=" },
    updationTime,
});

class MockClient {
    userID = USER_ID;
    failCollections = false;
    collectionsQueue: CollectionsPage[] = [];
    filesByCollection = new Map<number, FilesPage[]>();

    collectionsSinceTimes: number[] = [];
    filesCalls: { collectionID: number; sinceTime: number }[] = [];

    whoami(): { email: string; userID: number } {
        return { email: "user@example.com", userID: this.userID };
    }

    async collectionsSince(args: {
        sinceTime: number;
    }): Promise<CollectionsPage> {
        this.collectionsSinceTimes.push(args.sinceTime);
        if (this.failCollections) throw new Error("network down");
        return (
            this.collectionsQueue.shift() ?? {
                collections: [],
                deleted: [],
                cursor: args.sinceTime,
            }
        );
    }

    async filesSince(args: {
        collectionID: number;
        collectionKey: Uint8Array;
        sinceTime: number;
    }): Promise<FilesPage> {
        this.filesCalls.push({
            collectionID: args.collectionID,
            sinceTime: args.sinceTime,
        });
        const queue = this.filesByCollection.get(args.collectionID);
        return (
            queue?.shift() ?? {
                files: [],
                deleted: [],
                cursor: args.sinceTime,
            }
        );
    }

    filesFor(collectionID: number, ...pages: FilesPage[]): void {
        this.filesByCollection.set(collectionID, pages);
    }
}

// A client seeded with one collection and one file, opened with an empty cache
// so the initial refresh is awaited and post-`open()` state is deterministic.
const openSeeded = async (
    cacheDirectory: string,
): Promise<{ client: MockClient; lib: Library }> => {
    const client = new MockClient();
    client.collectionsQueue.push({
        collections: [collection(1, 100)],
        deleted: [],
        cursor: 100,
    });
    client.filesFor(1, {
        files: [file(1001, 1, 90)],
        deleted: [],
        cursor: 90,
    });
    const lib = await Library.open({
        client,
        cacheDirectory,
        refreshIntervalSeconds: SLOW_INTERVAL,
    });
    return { client, lib };
};

describe("Library.fresh", () => {
    let dir: string;
    let cacheDirectory: string;

    beforeEach(() => {
        dir = mkdtempSync(join(tmpdir(), "quak-fresh-"));
        cacheDirectory = join(dir, "cache");
    });

    afterEach(() => {
        rmSync(dir, { recursive: true, force: true });
    });

    it("observes a server change a same-instant default read would miss", async () => {
        const { client, lib } = await openSeeded(cacheDirectory);
        try {
            // A new file appears on the server after open, advancing its
            // collection so the next refresh re-enumerates it.
            client.collectionsQueue.push({
                collections: [collection(1, 200)],
                deleted: [],
                cursor: 200,
            });
            client.filesFor(1, {
                files: [file(1002, 1, 190)],
                deleted: [],
                cursor: 190,
            });

            // A default read at this instant has not refreshed: it misses 1002.
            expect(lib.photos.byID({ fileID: 1002 })).toBeUndefined();

            // A fresh read forces the round-trip and sees it.
            const reads = await lib.fresh();
            expect(reads.photos.byID({ fileID: 1002 })?.fileID).toBe(1002);
            // And the change is now live for the default namespaces too.
            expect(lib.photos.byID({ fileID: 1002 })?.fileID).toBe(1002);
        } finally {
            lib.close();
        }
    });

    it("coalesces concurrent fresh reads onto one in-flight refresh", async () => {
        const { client, lib } = await openSeeded(cacheDirectory);
        try {
            client.collectionsQueue.push({
                collections: [collection(1, 200)],
                deleted: [],
                cursor: 200,
            });
            client.filesFor(1, {
                files: [file(1002, 1, 190)],
                deleted: [],
                cursor: 190,
            });

            const collectionsBefore = client.collectionsSinceTimes.length;
            const filesBefore = client.filesCalls.length;

            // Gate the next collections fetch so all three fresh reads are in
            // flight together before any of them completes.
            let release: () => void = () => {};
            const gate = new Promise<void>((r) => {
                release = r;
            });
            const inner = client.collectionsSince.bind(client);
            client.collectionsSince = async (args: { sinceTime: number }) => {
                await gate;
                return inner(args);
            };

            const all = Promise.all([lib.fresh(), lib.fresh(), lib.fresh()]);
            release();
            const [a, b, c] = await all;

            // Exactly one collections round-trip and one file round-trip served
            // all three fresh reads.
            expect(client.collectionsSinceTimes.length).toBe(
                collectionsBefore + 1,
            );
            expect(client.filesCalls.length).toBe(filesBefore + 1);

            // All three observed the change.
            for (const reads of [a, b, c]) {
                expect(reads.photos.byID({ fileID: 1002 })?.fileID).toBe(1002);
            }
        } finally {
            lib.close();
        }
    });

    it("rejects the fresh read when the refresh fails, leaving defaults intact", async () => {
        const { client, lib } = await openSeeded(cacheDirectory);
        try {
            client.failCollections = true;

            // Two concurrent fresh reads both reject, and share one failed
            // round-trip rather than each making its own.
            const collectionsBefore = client.collectionsSinceTimes.length;
            const first = lib.fresh();
            const second = lib.fresh();
            await expect(first).rejects.toThrow(/network down/);
            await expect(second).rejects.toThrow(/network down/);
            expect(client.collectionsSinceTimes.length).toBe(
                collectionsBefore + 1,
            );

            // The default reads never rejected: they still serve the last good
            // copy, and the failure surfaced through status().
            expect(lib.photos.byID({ fileID: 1001 })?.fileID).toBe(1001);
            expect(lib.status().lastError).toMatch(/network down/);

            // Recovery: once the server answers, a fresh read resolves current.
            client.failCollections = false;
            client.collectionsQueue.push({
                collections: [collection(2, 300)],
                deleted: [],
                cursor: 300,
            });
            const reads = await lib.fresh();
            expect(reads.albums.byID({ collectionID: 2 })?.collectionID).toBe(
                2,
            );
            expect(lib.status().lastError).toBeUndefined();
        } finally {
            lib.close();
        }
    });
});