Save import: read the Gen 2 Unown Report

Gen 2 (GSC) is the one mainline dex that records which Unown letters
you've caught — a 26-byte ordered list right after the Seen flag array
(seen + 0x20). Parse it, map letters to the app's Form Dex slugs
('unown' for A, 'unown-b'…'unown-z'), and tick them via a new
markFormsCaught() on the formTracking store. A garbage/out-of-range list
is ignored rather than guessed at.

The import dialog and result line now surface "· N Unown letters".

Verified: 6 new unit tests (synthetic Gen 2 SRAM → slugs, empty list,
garbage rejection; markFormsCaught behaviour) + a real end-to-end import
of a synthetic Crystal save writing {unown, unown-c, unown-o, unown-z}
to pdx.formTracking.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017Ve7HLspzeG2xDPtJQ8vmu

README.md

@@ -143,9 +143,9 @@ marks the Pokémon caught.
 bitfields — not an approximation — from:
 
 | Gen | Games                                              | Format                                                                  |
-| --- | -------------------------------------------------- | -------------------------------------------------------- |
+| --- | -------------------------------------------------- | ----------------------------------------------------------------------- |
 | 1   | Red / Blue / Yellow                                | 32 KB SRAM (`.sav` / `.srm`)                                            |
-| 2   | Gold / Silver / Crystal                            | 32 KB SRAM — checksum picks G/S vs Crystal               |
+| 2   | Gold / Silver / Crystal                            | 32 KB SRAM — checksum picks G/S vs Crystal; also reads the Unown Report |
 | 3   | Ruby / Sapphire / Emerald, FireRed / LeafGreen     | 128 KB — newer slot, rotated sections                                   |
 | 4   | Diamond / Pearl / Platinum, HeartGold / SoulSilver | 512 KB NDS — active slot, DeSmuME `.dsv` footer stripped                |
 | 5   | Black / White, Black 2 / White 2                   | 512 KB NDS — per-form "seen" copies OR'd                                |
@@ -156,6 +156,11 @@ species is also seen). A dialog then offers **merge** or **replace** into
 one game's bucket — the selected game if the save could be it, otherwise
 the parser's best guess.
 
+The dex bitfields are per-species, so form sets (Unown letters, Vivillon
+patterns…) can't be recovered from them — **except** the Gen 2 Unown
+Report, which records the letters you've caught; a Gen 2 import ticks
+those in the per-letter Form Dex.
+
 Full local state (settings, per-game tracking, team, form tracking, shiny
 hunts, played games) also exports / imports as a single JSON file.
 

src/lib/savedex.js

@@ -122,10 +122,14 @@ function tryGen1(bytes) {
  * ------------------------------------------------------------------ */
 
 const G2 = {
+  // `unown` is the Unown Report list — the letter forms caught, in
+  // first-caught order, one byte each (1 = A … 26 = Z), zero-terminated. It
+  // sits right after the 32-byte Seen flag array (`unown === seen + 0x20`).
   gs: {
     name: 0x200b,
     owned: 0x2a4c,
     seen: 0x2a6c,
+    unown: 0x2a8c,
     ck: 0x2d69,
     ckFrom: 0x2009,
     ckTo: 0x2d68,
@@ -136,6 +140,7 @@ const G2 = {
     name: 0x2009,
     owned: 0x2a27,
     seen: 0x2a47,
+    unown: 0x2a67,
     ck: 0x2d0d,
     ckFrom: 0x2009,
     ckTo: 0x2b82,
@@ -145,6 +150,32 @@ const G2 = {
 };
 const G2_SPECIES = 251;
 
+// Letter index (1 = A) → the app's cosmetic-form slug. The base "A" form is
+// tracked under the bare species slug; B…Z are `unown-b` … `unown-z`.
+const unownSlug = (n) => (n === 1 ? 'unown' : `unown-${String.fromCharCode(96 + n)}`);
+
+/**
+ * Read the Gen 2 Unown Report. Returns the caught letters as form slugs, or
+ * `null` if the bytes don't look like a valid ordered list (wrong offset,
+ * corruption) — a species-level import shouldn't tick form boxes on a guess.
+ */
+function readUnownDex(bytes, offset) {
+  const slugs = [];
+  const seen = new Set();
+  let ended = false;
+  for (let i = 0; i < 26; i++) {
+    const b = bytes[offset + i];
+    if (b === 0) {
+      ended = true;
+      continue;
+    }
+    if (ended || b > 26 || seen.has(b)) return null;
+    seen.add(b);
+    slugs.push(unownSlug(b));
+  }
+  return slugs;
+}
+
 function tryGen2Variant(bytes, v) {
   const caught = bitsToList(bytes, v.owned, G2_SPECIES);
   const seen = bitsToList(bytes, v.seen, G2_SPECIES);
@@ -162,6 +193,9 @@ function tryGen2Variant(bytes, v) {
     trainer: decodeName(bytes.subarray(v.name, v.name + 11), GB_CHARS, 0x50),
     seen,
     caught,
+    // Gen 2 is the only mainline dex that records which Unown letters you
+    // have — tick them in the app's per-letter Form Dex.
+    formCaught: readUnownDex(bytes, v.unown) || [],
     nationalUnlocked: true,
     checksumOk,
   };
@@ -387,7 +421,7 @@ function tryGen5(raw) {
 
 /**
  * @param {ArrayBuffer} buffer
- * @returns {{ gen:number, game:string, versionGroups:string[], trainer:string, seen:number[], caught:number[], nationalUnlocked:boolean }}
+ * @returns {{ gen:number, game:string, versionGroups:string[], trainer:string, seen:number[], caught:number[], formCaught?:string[], nationalUnlocked:boolean }}
  * @throws {Error} with a user-facing message if it can't be read.
  */
 export function parseSaveDex(buffer) {

src/store/formTracking.js

@@ -18,3 +18,13 @@ export function toggleFormCaught(slug) {
     caught: { ...s.caught, [slug]: !s.caught[slug] },
   }));
 }
+
+/** Mark a batch of form slugs caught (e.g. Unown letters from a save import). Never un-marks. */
+export function markFormsCaught(slugs) {
+  if (!slugs || !slugs.length) return;
+  formTracking.set((s) => {
+    const caught = { ...s.caught };
+    for (const slug of slugs) caught[slug] = true;
+    return { ...s, caught };
+  });
+}

src/views/SettingsView.js

@@ -4,7 +4,7 @@ import { selection, importFlags, replaceFlags, normalizeSelection } from '../sto
 import { prettify } from '../data/pokedex-resolver.js';
 import { chooseDialog } from '../lib/dialog.js';
 import { team } from '../store/team.js';
-import { formTracking } from '../store/formTracking.js';
+import { formTracking, markFormsCaught } from '../store/formTracking.js';
 import { shinyHunts } from '../store/shinyHunts.js';
 import { playedGames, markPlayed } from '../store/playedGames.js';
 import { parseSaveDex } from '../lib/savedex.js';
@@ -180,9 +180,11 @@ export async function SettingsView() {
       const target = cands.includes(settings.get().versionGroup)
         ? settings.get().versionGroup
         : cands[0];
+      const unown = dex.formCaught?.length || 0;
+      const unownLine = unown ? ` · ${unown} Unown letter${unown === 1 ? '' : 's'}` : '';
       const choice = await chooseDialog({
         title: `${dex.game}${dex.trainer ? ` · ${dex.trainer}` : ''}`,
-        body: `${dex.seen.length} seen · ${dex.caught.length} caught in this save.`,
+        body: `${dex.seen.length} seen · ${dex.caught.length} caught${unownLine} in this save.`,
         choices: [
           { key: 'merge', label: `Add to ${prettify(target)}` },
           {
@@ -195,12 +197,14 @@ export async function SettingsView() {
       });
       if (choice === 'merge') {
         importFlags({ seen: dex.seen, caught: dex.caught, game: target });
+        markFormsCaught(dex.formCaught);
         markPlayed(...cands);
-        saveNote.textContent = `Added ${dex.caught.length} caught / ${dex.seen.length} seen to ${prettify(target)}.`;
+        saveNote.textContent = `Added ${dex.caught.length} caught / ${dex.seen.length} seen${unownLine} to ${prettify(target)}.`;
       } else if (choice === 'replace') {
         replaceFlags({ seen: dex.seen, caught: dex.caught, game: target });
+        markFormsCaught(dex.formCaught);
         markPlayed(...cands);
-        saveNote.textContent = `Set ${prettify(target)}'s Pokédex from ${who}.`;
+        saveNote.textContent = `Set ${prettify(target)}'s Pokédex from ${who}${unownLine ? ` (${unown} Unown letters)` : ''}.`;
       } else {
         saveNote.textContent = '';
       }

test/formTracking.test.js

@@ -0,0 +1,37 @@
+import { describe, it, expect, beforeEach } from 'vitest';
+import {
+  formTracking,
+  isFormCaught,
+  toggleFormCaught,
+  markFormsCaught,
+} from '../src/store/formTracking.js';
+
+beforeEach(() => {
+  localStorage.clear();
+  formTracking.replace({ caught: {} });
+});
+
+describe('formTracking', () => {
+  it('toggle flips a slug', () => {
+    expect(isFormCaught('unown-c')).toBe(false);
+    toggleFormCaught('unown-c');
+    expect(isFormCaught('unown-c')).toBe(true);
+    toggleFormCaught('unown-c');
+    expect(isFormCaught('unown-c')).toBe(false);
+  });
+
+  it('markFormsCaught sets a batch and never un-marks', () => {
+    toggleFormCaught('unown-z'); // already caught
+    markFormsCaught(['unown', 'unown-c', 'unown-z']);
+    expect(isFormCaught('unown')).toBe(true);
+    expect(isFormCaught('unown-c')).toBe(true);
+    expect(isFormCaught('unown-z')).toBe(true); // stays caught
+    expect(isFormCaught('unown-q')).toBe(false); // untouched
+  });
+
+  it('markFormsCaught tolerates empty / missing input', () => {
+    markFormsCaught([]);
+    markFormsCaught(undefined);
+    expect(formTracking.get().caught).toEqual({});
+  });
+});

test/savedex.test.js

@@ -59,3 +59,41 @@ describe('parseSaveDex — Gen 1', () => {
     expect(() => parseSaveDex(new Uint8Array(0x20000).buffer)).toThrow();
   });
 });
+
+// --- Synthetic Gen 2 (Crystal) SRAM ---------------------------------
+// Offsets mirror src/lib/savedex.js `G2.cr`.
+const G2 = { owned: 0x2a27, seen: 0x2a47, unown: 0x2a67, ck: 0x2d0d, ckFrom: 0x2009, ckTo: 0x2b82 };
+
+function makeGen2Save({ caught, seen, unown = [] }) {
+  const bytes = new Uint8Array(0x8000);
+  setBits(bytes, G2.owned, caught);
+  setBits(bytes, G2.seen, seen);
+  unown.forEach((letter, i) => (bytes[G2.unown + i] = letter)); // 1 = A … 26 = Z
+  let sum = 0;
+  for (let i = G2.ckFrom; i <= G2.ckTo; i++) sum = (sum + bytes[i]) & 0xffffffff;
+  bytes[G2.ck] = sum & 0xff;
+  bytes[G2.ck + 1] = (sum >> 8) & 0xff;
+  return bytes.buffer;
+}
+
+describe('parseSaveDex — Gen 2 Unown Report', () => {
+  it('turns the caught-letter list into Form Dex slugs', () => {
+    const dex = parseSaveDex(
+      makeGen2Save({ caught: [1, 25], seen: [1, 25, 201], unown: [3, 1, 20] }), // C, A, T
+    );
+    expect(dex.gen).toBe(2);
+    expect(dex.game).toBe('Crystal');
+    expect(dex.checksumOk).toBe(true);
+    expect([...dex.formCaught].sort()).toEqual(['unown', 'unown-c', 'unown-t']);
+  });
+
+  it('no Unown caught → empty list', () => {
+    const dex = parseSaveDex(makeGen2Save({ caught: [1], seen: [1], unown: [] }));
+    expect(dex.formCaught).toEqual([]);
+  });
+
+  it('ignores a garbage list rather than ticking wrong boxes', () => {
+    const dex = parseSaveDex(makeGen2Save({ caught: [1], seen: [1], unown: [3, 99, 5] }));
+    expect(dex.formCaught).toEqual([]);
+  });
+});