/**
 * InkNote Offline Store — IndexedDB local-first storage.
 *
 * All reads and writes go here first, so the app works offline; the sync engine
 * pushes queued changes to the server when a connection is available.
 */

import type { Chapter, NoteMeta, NoteContent, Notebook, StrokeDoc, QueueEntry } from "./types";

const DB_NAME = "inknote";
const DB_VERSION = 4;

type StoreName = "notebooks" | "chapters" | "notes" | "noteContents" | "syncQueue" | "meta" | "attachments";

let db: IDBDatabase | null = null;

function open(): Promise<IDBDatabase> {
  return new Promise((resolve, reject) => {
    if (db) return resolve(db);
    const req = indexedDB.open(DB_NAME, DB_VERSION);

    req.onupgradeneeded = (e) => {
      const d = (e.target as IDBOpenDBRequest).result;

      if (!d.objectStoreNames.contains("notebooks")) {
        const nb = d.createObjectStore("notebooks", { keyPath: "id" });
        nb.createIndex("sortOrder", "sortOrder");
      }

      if (!d.objectStoreNames.contains("notes")) {
        const n = d.createObjectStore("notes", { keyPath: "id" });
        n.createIndex("folderId", "folderId");
        n.createIndex("trashed", "trashed");
        n.createIndex("updatedAt", "updatedAt");
      }

      // Bodies live apart from metadata so the note list stays cheap to load.
      if (!d.objectStoreNames.contains("noteContents")) {
        d.createObjectStore("noteContents", { keyPath: "id" });
      }

      if (!d.objectStoreNames.contains("syncQueue")) {
        const sq = d.createObjectStore("syncQueue", { keyPath: "queueId", autoIncrement: true });
        sq.createIndex("entityId", "entityId");
        sq.createIndex("timestamp", "timestamp");
      }

      if (!d.objectStoreNames.contains("meta")) {
        d.createObjectStore("meta", { keyPath: "key" });
      }

      // Attachment bytes, so images render offline and download only once.
      if (!d.objectStoreNames.contains("attachments")) {
        d.createObjectStore("attachments", { keyPath: "id" });
      }

      // Chapters — folders inside a notebook.
      if (!d.objectStoreNames.contains("chapters")) {
        const ch = d.createObjectStore("chapters", { keyPath: "id" });
        ch.createIndex("notebookId", "notebookId");
      }
    };

    req.onsuccess = (e) => {
      db = (e.target as IDBOpenDBRequest).result;
      resolve(db);
    };
    req.onerror = (e) => reject((e.target as IDBOpenDBRequest).error);
  });
}

function reqToPromise<T>(req: IDBRequest<T>): Promise<T> {
  return new Promise((res, rej) => {
    req.onsuccess = () => res(req.result);
    req.onerror = () => rej(req.error);
  });
}

/** Resolves when the whole transaction commits, not just one request. */
function txDone(t: IDBTransaction): Promise<void> {
  return new Promise((res, rej) => {
    t.oncomplete = () => res();
    t.onerror = () => rej(t.error);
    t.onabort = () => rej(t.error ?? new Error("Transaction aborted"));
  });
}

async function store(name: StoreName, mode: IDBTransactionMode): Promise<IDBObjectStore> {
  const d = await open();
  return d.transaction(name, mode).objectStore(name);
}

/* ─── Meta (key-value) ─── */
export async function getMeta<T = unknown>(key: string): Promise<T | null> {
  const s = await store("meta", "readonly");
  const r = await reqToPromise<{ key: string; value: T } | undefined>(s.get(key));
  return r?.value ?? null;
}

export async function setMeta(key: string, value: unknown): Promise<void> {
  const s = await store("meta", "readwrite");
  await reqToPromise(s.put({ key, value }));
}

export async function deleteMeta(key: string): Promise<void> {
  const s = await store("meta", "readwrite");
  await reqToPromise(s.delete(key));
}

/* ─── Chapters ─── */

export async function getAllChapters(): Promise<Chapter[]> {
  const s = await store("chapters", "readonly");
  return reqToPromise<Chapter[]>(s.getAll());
}

export async function putChapter(c: Chapter): Promise<void> {
  const s = await store("chapters", "readwrite");
  await reqToPromise(s.put(c));
}

export async function putChapters(list: Chapter[]): Promise<void> {
  const s = await store("chapters", "readwrite");
  for (const c of list) s.put(c);
  await txDone(s.transaction);
}

export async function deleteChapter(id: string): Promise<void> {
  const s = await store("chapters", "readwrite");
  await reqToPromise(s.delete(id));
}

/* ─── Notebooks ─── */
export async function getAllNotebooks(): Promise<Notebook[]> {
  const s = await store("notebooks", "readonly");
  const all = await reqToPromise<Notebook[]>(s.getAll());
  return all.sort((a, b) => (a.sortOrder || 0) - (b.sortOrder || 0));
}

export async function putNotebook(nb: Notebook): Promise<void> {
  const s = await store("notebooks", "readwrite");
  await reqToPromise(s.put(nb));
}

export async function putNotebooks(list: Notebook[]): Promise<void> {
  const d = await open();
  const t = d.transaction("notebooks", "readwrite");
  const s = t.objectStore("notebooks");
  for (const nb of list) s.put(nb);
  return txDone(t);
}

export async function deleteNotebook(id: string): Promise<void> {
  const s = await store("notebooks", "readwrite");
  await reqToPromise(s.delete(id));
}

export async function clearNotebooks(): Promise<void> {
  const s = await store("notebooks", "readwrite");
  await reqToPromise(s.clear());
}

/* ─── Notes (metadata) ─── */
export async function getAllNotes(): Promise<NoteMeta[]> {
  const s = await store("notes", "readonly");
  return reqToPromise<NoteMeta[]>(s.getAll());
}

export async function getNote(id: string): Promise<NoteMeta | undefined> {
  const s = await store("notes", "readonly");
  return reqToPromise<NoteMeta | undefined>(s.get(id));
}

export async function putNote(note: NoteMeta): Promise<void> {
  const s = await store("notes", "readwrite");
  await reqToPromise(s.put(note));
}

export async function putNotes(list: NoteMeta[]): Promise<void> {
  const d = await open();
  const t = d.transaction("notes", "readwrite");
  const s = t.objectStore("notes");
  for (const n of list) s.put(n);
  return txDone(t);
}

export async function deleteNote(id: string): Promise<void> {
  const d = await open();
  const t = d.transaction(["notes", "noteContents"], "readwrite");
  t.objectStore("notes").delete(id);
  t.objectStore("noteContents").delete(id);
  return txDone(t);
}

export async function clearNotes(): Promise<void> {
  const s = await store("notes", "readwrite");
  await reqToPromise(s.clear());
}

/* ─── Note content (lazily loaded) ─── */
export async function getNoteContent(id: string): Promise<(NoteContent & { id: string }) | undefined> {
  const s = await store("noteContents", "readonly");
  return reqToPromise<(NoteContent & { id: string }) | undefined>(s.get(id));
}

/**
 * `updatedAt` records which server revision this copy came from, so a background
 * prefetch can tell a stale cached body from an up-to-date one.
 */
export async function putNoteContent(
  id: string,
  content: string,
  drawingData: string | null,
  drawingStrokes: StrokeDoc | null = null,
  updatedAt: string | null = null
): Promise<void> {
  const s = await store("noteContents", "readwrite");
  await reqToPromise(s.put({ id, content, drawingData, drawingStrokes, updatedAt }));
}

/* ─── Attachments (binary cache) ─── */
export async function getAttachmentBlob(id: string): Promise<Blob | null> {
  const s = await store("attachments", "readonly");
  const r = await reqToPromise<{ id: string; blob: Blob } | undefined>(s.get(id));
  return r?.blob ?? null;
}

export async function putAttachmentBlob(id: string, blob: Blob): Promise<void> {
  const s = await store("attachments", "readwrite");
  await reqToPromise(s.put({ id, blob, cachedAt: Date.now() }));
}

/* ─── Sync queue ─── */
export async function enqueue(action: { action: string; data: Record<string, unknown> }): Promise<void> {
  const s = await store("syncQueue", "readwrite");
  await reqToPromise(s.add({ ...action, timestamp: Date.now() }));
}

export async function peekQueue(limit = 50): Promise<QueueEntry[]> {
  const s = await store("syncQueue", "readonly");
  return reqToPromise<QueueEntry[]>(s.getAll(null, limit));
}

export async function dequeue(queueId: number): Promise<void> {
  const s = await store("syncQueue", "readwrite");
  await reqToPromise(s.delete(queueId));
}

/** Records a failed attempt so a retried entry can eventually be given up on. */
export async function updateQueueEntry(queueId: number, patch: Partial<QueueEntry>): Promise<void> {
  const s = await store("syncQueue", "readwrite");
  const entry = await reqToPromise<QueueEntry | undefined>(s.get(queueId));
  if (!entry) return;
  await reqToPromise(s.put({ ...entry, ...patch }));
}

/**
 * Rewrites every queued reference to a temporary id.
 *
 * Something made offline carries an id this device invented. When its create
 * finally reaches the server, the server names it something else — and every
 * entry still waiting in the queue is addressed to the name nobody else knows.
 *
 * They used to be left as they were. The database was repointed and the queue
 * was not, so the create arrived and then every edit behind it asked the server
 * for `local_xxxx`, got a 404, retried five times and was thrown away: a note
 * written and drawn on offline reached the server empty and untitled, with the
 * work silently dropped.
 *
 * The replacement is a plain string match over the whole payload rather than a
 * list of fields to look in. Ids are long random strings, so a false match is
 * not a practical worry — and a list of fields is a list to forget to add to.
 */
export async function repointQueue(oldId: string, newId: string): Promise<void> {
  if (!oldId || oldId === newId) return;
  const s = await store("syncQueue", "readwrite");
  const entries = await reqToPromise<QueueEntry[]>(s.getAll());
  for (const entry of entries) {
    const before = JSON.stringify(entry.data ?? {});
    if (!before.includes(oldId)) continue;
    await reqToPromise(s.put({ ...entry, data: JSON.parse(before.split(oldId).join(newId)) }));
  }
}

export async function clearQueue(): Promise<void> {
  const s = await store("syncQueue", "readwrite");
  await reqToPromise(s.clear());
}

export async function getQueueSize(): Promise<number> {
  const s = await store("syncQueue", "readonly");
  return reqToPromise<number>(s.count());
}

/* ─── Full wipe (on logout) ─── */
export async function clearAll(): Promise<void> {
  const d = await open();
  const stores: StoreName[] = ["notebooks", "notes", "noteContents", "syncQueue", "meta", "attachments"];
  const t = d.transaction(stores, "readwrite");
  for (const s of stores) t.objectStore(s).clear();
  return txDone(t);
}