Track inventory at the instance level, not by product

The products table conflated catalog ("kind of thing you scan") with
instance ("this jar I bought") — splitting it lets us record every
purchase as its own asset and autofill brand/shop/price/THC from the
last instance when scanning a known SKU.

- products: sku + strain + name + type + kind (catalog only)
- inventory_items: physical jars with short-UUID asset ids, per-batch
  brand/shop/bin/price/cannabinoids/weight, audits, lifecycle
- audits now key on inventory_id; strains lose brand_id and type
- migration: rename existing products/audits/strains to *_legacy on
  first boot so users keep historical reference, fresh start otherwise
- two-step add flow: scan SKU → select/create product → instance
  details (autofilled from last instance) → generated asset id shown
- ScanField matches asset id first, falls back to SKU
- inventory list defaults flat, "By product" toggle groups instances

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/src/db.ts

@@ -11,18 +11,48 @@ export const db = new Database(DB_PATH);
 db.pragma("journal_mode = WAL");
 db.pragma("foreign_keys = ON");
 
+archiveLegacyIfPresent();
+
 const schema = readFileSync(join(__dirname, "schema.sql"), "utf8");
 db.exec(schema);
 
-// Add strain_id to products table if missing — older DBs predate the column.
-const productCols = db
-  .prepare(`PRAGMA table_info(products)`)
-  .all() as { name: string }[];
-if (!productCols.some((c) => c.name === "strain_id")) {
-  db.exec(`ALTER TABLE products ADD COLUMN strain_id TEXT REFERENCES strains(id);`);
-  db.exec(`CREATE INDEX IF NOT EXISTS idx_products_strain ON products(strain_id);`);
+// One-shot migration: the old schema put per-instance fields (weight, bin_id,
+// etc.) directly on `products`. The new schema splits products (catalog) from
+// inventory_items (instance). When we detect the old shape, rename the live
+// tables out of the way so the new CREATE TABLE IF NOT EXISTS statements can
+// build the empty new ones. Legacy tables stay queryable for reference.
+function archiveLegacyIfPresent(): void {
+  const productCols = db
+    .prepare(`PRAGMA table_info(products)`)
+    .all() as { name: string }[];
+  const looksLikeOldSchema =
+    productCols.length > 0 && productCols.some((c) => c.name === "weight");
+  if (!looksLikeOldSchema) return;
+
+  const legacyExists = db
+    .prepare(
+      `SELECT name FROM sqlite_master WHERE type='table' AND name='products_legacy'`,
+    )
+    .get();
+  if (legacyExists) return;
+
+  db.exec(`
+    ALTER TABLE products RENAME TO products_legacy;
+    ALTER TABLE audits RENAME TO audits_legacy;
+    ALTER TABLE strains RENAME TO strains_legacy;
+  `);
 }
 
+const PAD: Record<string, number> = {
+  prd: 4,
+  pdt: 4,
+  inv: 4,
+  str: 4,
+  brd: 2,
+  shp: 2,
+  bin: 2,
+};
+
 export function nextId(prefix: string, table: string): string {
   const row = db
     .prepare<[string], { id: string }>(
@@ -30,11 +60,31 @@ export function nextId(prefix: string, table: string): string {
     )
     .get(`${prefix}-%`);
   const last = row ? Number(row.id.slice(prefix.length + 1)) : 0;
-  const pad = prefix === "prd" || prefix === "str" ? 4 : 2;
+  const pad = PAD[prefix] ?? 2;
   const n = String(last + 1).padStart(pad, "0");
   return `${prefix}-${n}`;
 }
 
+// Crockford base32 alphabet — drops I, L, O, U so labels are unambiguous when
+// read off a sticker. 32^6 ≈ 1B addresses, so collisions on any reasonable
+// inventory are vanishingly rare; we still loop just to be safe.
+const ASSET_ALPHABET = "0123456789ABCDEFGHJKMNPQRSTVWXYZ";
+export function generateAssetId(): string {
+  for (let attempt = 0; attempt < 16; attempt++) {
+    let id = "";
+    for (let i = 0; i < 6; i++) {
+      id += ASSET_ALPHABET[Math.floor(Math.random() * ASSET_ALPHABET.length)];
+    }
+    const taken = db
+      .prepare<[string], { id: string }>(
+        `SELECT id FROM inventory_items WHERE asset_id = ?`,
+      )
+      .get(id);
+    if (!taken) return id;
+  }
+  throw new Error("could not generate a unique asset id after 16 attempts");
+}
+
 export function randomSku(): string {
   return "SKU-" + Math.random().toString(36).slice(2, 8).toUpperCase();
 }