align plugin with new architecture

src/meta-shape.ts

@@ -0,0 +1,65 @@
+/**
+ * Reading a record regardless of the shape it arrives in, and writing only what
+ * is new.
+ *
+ * meta-sort's scheduler fills `existingMeta` from meta-sort's own GET /meta/{hash},
+ * which returns the NESTED document (`fileinfo: {duration: 1433.089}`,
+ * `stream: [...]`, a key-set as `subtitles: {fre: {<cid>: true}}`). meta-core's
+ * backend serves the FLAT form (`fileinfo/duration`, `stream/0`,
+ * `subtitles/fre/<cid>`). A plugin that reads `existingMeta['x/y']` silently sees
+ * nothing in production — so everything here goes through `flattenMeta`.
+ *
+ * Byte-identical in metamesh-plugin-subtitle and metamesh-plugin-subtitle-extractor.
+ */
+
+/** Flatten either form into `a/b/c -> string` (meta-sort's flattenMetadata, plus array indices). */
+export function flattenMeta(meta: Record<string, unknown> | undefined | null): Record<string, string> {
+    const out: Record<string, string> = {};
+    const walk = (value: unknown, key: string) => {
+        if (value === null || value === undefined) return;
+        if (Array.isArray(value)) {
+            value.forEach((v, i) => walk(v, key ? `${key}/${i}` : String(i)));
+        } else if (typeof value === 'object') {
+            for (const [k, v] of Object.entries(value as Record<string, unknown>)) {
+                walk(v, key ? `${key}/${k}` : k);
+            }
+        } else if (key) {
+            out[key] = String(value);
+        }
+    };
+    walk(meta ?? {}, '');
+    return out;
+}
+
+/** The subset of `wanted` the record does not already hold with that exact value. */
+export function onlyNewKeys(existingFlat: Record<string, string>, wanted: Record<string, string>): Record<string, string> {
+    const out: Record<string, string> = {};
+    for (const [k, v] of Object.entries(wanted)) {
+        if (existingFlat[k] !== v) out[k] = v;
+    }
+    return out;
+}
+
+/**
+ * Members of a LEGACY scalar csv-set (`subtitles = "cidA,cidB"`, written by the
+ * old `_add` path), or null when the field is absent or already a key-set.
+ *
+ * Such a scalar must be deleted before any `field/...` key is written: meta-sort
+ * rebuilds its nested document by walking the `/`-segments, and a string sitting
+ * where an object is needed either throws or silently hides the key-set.
+ */
+export function legacyCsvMembers(meta: Record<string, unknown> | undefined | null, field: string): string[] | null {
+    const v = meta?.[field];
+    if (typeof v !== 'string' && typeof v !== 'number') return null;
+    return String(v).split(/[,|]/).map((s) => s.trim()).filter(Boolean);
+}
+
+/** Every `<prefix>/<lang>/<cid>` leaf for `cid` whose language is not `lang3`. */
+export function staleLanguageLeaves(existingFlat: Record<string, string>, prefix: string, cid: string, lang3: string): string[] {
+    const stale: string[] = [];
+    for (const key of Object.keys(existingFlat)) {
+        const parts = key.split('/');
+        if (parts.length === 3 && parts[0] === prefix && parts[2] === cid && parts[1] !== lang3) stale.push(key);
+    }
+    return stale;
+}