fix: an address holding only unpriced tokens is no longer totalled at $0.00 (closes #261)

Prices are fetched for the top 25 tokens only, so an address can hold real
assets this build has no price for. The address total summed the priced
holdings and printed the result as the total, so an address holding nothing
but unpriced ERC-20s was reported as worth $0.00 — wrong in the direction
that matters, and on the address-removal confirmation it sat directly under
"This address holds a balance."

getAddressValue() returns { usd, partial }: the value of the priced holdings,
and whether an unpriced holding was left out of it. Worth zero and worth an
unknown amount stay separate facts, as an absent holders_count stays separate
from a count of zero. formatAddressTotal() is the one rendering of that pair,
so no screen can word it differently:

  - nothing knowable (testnet, before the first fetch): no total line
  - everything priced:  "Total: $5,500.00"
  - part priced:        "Total: $3,000.00 plus unpriced tokens"
  - nothing priced:     "Total: unpriced tokens only"

A partial total is kept rather than suppressed: the figure is the ETH and
priced tokens the user does hold and is correct as far as it goes, so it is
named as a floor instead of being thrown away. What is never printed is a
figure covering no holdings at all.

All four call sites read it — the Home summary line, the Home wallet list,
AddressDetail and the removal confirmation — and getWalletValue() and
getTotalValue() carry partial up so a future consumer cannot lose it.
The per-token balance lines are unchanged: a token with no price shows its
quantity and a blank USD column.

tests/addressValue.test.js covers the only-unpriced, genuinely-zero and
fully-priced cases at the helper, at its formatter, and through both call
sites that return their markup as a string. Written first and watched fail
on the unfixed helper: the Home wallet list gave "$0.00" and the removal
confirmation "Total: $0.00" for an address holding 5000 unpriced tokens.

src/shared/prices.js

@@ -55,42 +55,77 @@ function formatUsd(amount) {
     );
 }
 
-function getAddressValueUsd(addr) {
+// What an address is worth, as { usd, partial }.
+//
+// Prices are fetched for the top 25 tokens only, so an address can hold real
+// assets this code has no price for. Adding up the priced ones and calling the
+// result the total states a number the holdings do not support: an address
+// holding nothing but unpriced tokens comes out at $0.00, which tells the user
+// their address is worth nothing when it may hold a great deal. Worth zero and
+// worth an unknown amount are separate facts and get separate fields, the same
+// way an absent holders_count is not a count of zero.
+//
+//   usd:     the value of the holdings a price is known for, or null when
+//            nothing is knowable at all — testnet, or before the first fetch.
+//   partial: the address also holds a token with no price, so usd is a floor
+//            and not the total.
+//
+// Render it through formatAddressTotal() rather than reading usd alone.
+function getAddressValue(addr) {
     const { currentNetwork } = require("./state");
-    if (currentNetwork().isTestnet) return null;
-    if (!prices.ETH) return null;
-    let total = 0;
-    const ethBal = parseFloat(addr.balance || "0");
-    total += ethBal * prices.ETH;
+    if (currentNetwork().isTestnet) return { usd: null, partial: false };
+    if (!prices.ETH) return { usd: null, partial: false };
+    let usd = parseFloat(addr.balance || "0") * prices.ETH;
+    let partial = false;
     for (const token of addr.tokenBalances || []) {
         const tokenBal = parseFloat(token.balance || "0");
-        if (tokenBal > 0 && prices[token.symbol]) {
-            total += tokenBal * prices[token.symbol];
+        // A balance of zero is not a holding: it can neither add to the total
+        // nor make it incomplete.
+        if (!(tokenBal > 0)) continue;
+        if (prices[token.symbol]) {
+            usd += tokenBal * prices[token.symbol];
+        } else {
+            partial = true;
         }
     }
-    return total;
+    return { usd, partial };
 }
 
-function getWalletValueUsd(wallet) {
-    const { currentNetwork } = require("./state");
-    if (currentNetwork().isTestnet) return null;
-    if (!prices.ETH) return null;
-    let total = 0;
-    for (const addr of wallet.addresses) {
-        total += getAddressValueUsd(addr);
-    }
-    return total;
+// The same pair for a whole wallet, and for every wallet at once. One
+// unpriced holding anywhere makes the sum a floor, so partial carries up.
+function getWalletValue(wallet) {
+    return sumValues(wallet.addresses.map(getAddressValue));
 }
 
-function getTotalValueUsd(wallets) {
-    const { currentNetwork } = require("./state");
-    if (currentNetwork().isTestnet) return null;
-    if (!prices.ETH) return null;
-    let total = 0;
-    for (const wallet of wallets) {
-        total += getWalletValueUsd(wallet);
+function getTotalValue(wallets) {
+    return sumValues(wallets.map(getWalletValue));
+}
+
+function sumValues(values) {
+    let usd = null;
+    let partial = false;
+    for (const value of values) {
+        if (value.usd === null) continue;
+        usd = (usd === null ? 0 : usd) + value.usd;
+        partial = partial || value.partial;
     }
-    return total;
+    return { usd, partial };
+}
+
+// The one rendering of an address total, so no screen says it differently.
+//
+// A partial total is shown and named as partial: the figure is the ETH and
+// priced tokens the user does hold, which is worth having, and suppressing it
+// would throw away a number that is correct as far as it goes. What is never
+// shown is a figure covering no holdings at all — the $0.00 sum of an empty
+// set beside a list of tokens is the bug this replaces.
+function formatAddressTotal(value) {
+    if (!value || value.usd === null) return "";
+    if (!value.partial) return "Total: " + formatUsd(value.usd);
+    if (value.usd > 0) {
+        return "Total: " + formatUsd(value.usd) + " plus unpriced tokens";
+    }
+    return "Total: unpriced tokens only";
 }
 
 module.exports = {
@@ -99,7 +134,8 @@ module.exports = {
     clearPrices,
     getPrice,
     formatUsd,
-    getAddressValueUsd,
-    getWalletValueUsd,
-    getTotalValueUsd,
+    formatAddressTotal,
+    getAddressValue,
+    getWalletValue,
+    getTotalValue,
 };