import sqlite3InitModule from '@sqlite.org/sqlite-wasm';
import { getWebDAVBaseUrl, basename, listDirectory, putFileContents, deletePath } from './webdav';

const LOCATE_PATH = '/sd/.locate';
// Resolved against import.meta.url so it works under any Vite base path
// (/, /config/, etc.) the same way the sqlite-wasm library resolves it.
const WASM_URL    = new URL('sqlite3.wasm', import.meta.url).toString();

function parseContentLength(header: string | null): number | null {
  if (!header) return null;
  const n = Number(header);
  return Number.isFinite(n) && n > 0 ? n : null;
}

// Fetch a URL and report progress as { received, total } chunks arrive.
// Returns the full byte array. Streams the body so progress is real-time
// (not just a single notification when the whole thing is buffered).
async function fetchWithProgress(
  url: string,
  onProgress?: (p: { received: number; total: number | null }) => void,
): Promise<Uint8Array> {
  const response = await fetch(url);
  if (!response.ok) throw new Error(`Cannot fetch ${url}: ${response.status} ${response.statusText}`);
  const total = parseContentLength(response.headers.get('content-length'));
  if (!response.body) {
    const buf = new Uint8Array(await response.arrayBuffer());
    onProgress?.({ received: buf.byteLength, total: total ?? buf.byteLength });
    return buf;
  }
  const reader = response.body.getReader();
  const chunks: Uint8Array[] = [];
  let received = 0;
  for (;;) {
    const { done, value } = await reader.read();
    if (done) break;
    chunks.push(value);
    received += value.byteLength;
    onProgress?.({ received, total });
  }
  const combined = new Uint8Array(received);
  let offset = 0;
  for (const chunk of chunks) { combined.set(chunk, offset); offset += chunk.byteLength; }
  return combined;
}

// Memoize the module init — loading the WASM binary is expensive.
// We pre-fetch the WASM in the main thread (with progress reporting)
// and hand the bytes to Emscripten as Module.wasmBinary so it skips
// its own internal fetch. The sqlite-wasm worker still loads its own
// copy on first use, but the main-thread load (the one users see in
// the network panel as a 400 KB download) is gone.
let _sqlite3Promise: Promise<any> | null = null;
function getSqlite3(
  onProgress?: (p: { received: number; total: number | null }) => void,
): Promise<any> {
  if (_sqlite3Promise) return _sqlite3Promise;
  _sqlite3Promise = (async () => {
    const wasmBytes = await fetchWithProgress(WASM_URL, onProgress);
    return sqlite3InitModule({
      print: () => {},
      printErr: () => {},
      wasmBinary: wasmBytes,
    });
  })();
  return _sqlite3Promise;
}

let _db: any | null = null;

export function isLocateDbLoaded(): boolean {
  return _db !== null;
}

export function resetLocateDb(): void {
  try { _db?.close(); } catch { /* ignore */ }
  _db = null;
}

export type DbProgress =
  | { kind: 'engine'; received: number; total: number | null }
  | { kind: 'database'; received: number; total: number | null };

/**
 * Fetch /sd/.locate and open it as an in-memory SQLite database. On the first
 * call this also loads the SQLite WASM engine (~400 KB), so onProgress fires
 * twice: first for the engine download, then for the locate database itself.
 * Calling again when already loaded is a no-op unless you call
 * resetLocateDb() first.
 */
export async function openLocateDb(
  onProgress?: (p: DbProgress) => void,
): Promise<void> {
  if (_db) return;

  const sqlite3 = await getSqlite3(
    p => onProgress?.({ kind: 'engine',   received: p.received, total: p.total }),
  );

  const url = getWebDAVBaseUrl() + LOCATE_PATH;
  const bytes = await fetchWithProgress(
    url,
    p => onProgress?.({ kind: 'database', received: p.received, total: p.total }),
  );

  // Allocate the bytes in WASM heap, then deserialize into a fresh in-memory DB.
  const p = sqlite3.wasm.allocFromTypedArray(bytes);
  const db = new sqlite3.oo1.DB(':memory:', 'ct');
  const rc = sqlite3.capi.sqlite3_deserialize(
    db.pointer,
    'main',
    p,
    bytes.length,
    bytes.length,
    1 | 2, // SQLITE_DESERIALIZE_FREEONCLOSE | SQLITE_DESERIALIZE_RESIZEABLE
  );
  if (rc !== 0) {
    db.close();
    throw new Error(`sqlite3_deserialize failed (code ${rc})`);
  }
  _db = db;
}

export type ScanPhase = 'scanning' | 'building' | 'saving';

/**
 * Recursively scan /sd, build a fresh SQLite locate database in memory,
 * and upload it to /sd/.locate via WebDAV PUT.
 *
 * onProgress(phase, value):
 *   scanning  → bytes of PROPFIND XML received so far
 *   building  → number of entries inserted so far
 *   saving    → bytes of the serialized DB written to the server
 */
export async function buildLocateDb(
  onProgress?: (phase: ScanPhase, value: number) => void,
): Promise<{ count: number; bytes: number }> {
  const sqlite3 = await getSqlite3();

  // ── 1. Recursive PROPFIND on /sd ────────────────────────────────────────
  const entries = await listDirectory(
    '/sd', true,
    bytes => onProgress?.('scanning', bytes),
  );

  // ── 2. Build in-memory DB ───────────────────────────────────────────────
  const db = new sqlite3.oo1.DB(':memory:', 'ct');
  db.exec(
    'CREATE TABLE files (' +
    '  path TEXT PRIMARY KEY,' +
    '  size INTEGER NOT NULL DEFAULT 0,' +
    '  mtime INTEGER NOT NULL DEFAULT 0,' +
    '  is_dir INTEGER NOT NULL DEFAULT 0' +
    ');' +
    'CREATE INDEX IF NOT EXISTS idx_path ON files(path);',
  );

  db.exec('BEGIN');
  const stmt = db.prepare('INSERT OR REPLACE INTO files VALUES (?,?,?,?)');
  try {
    for (let i = 0; i < entries.length; i++) {
      const e = entries[i];
      stmt.bind([
        e.path,
        e.size,
        e.lastModified ? Math.floor(e.lastModified.getTime() / 1000) : 0,
        e.type === 'folder' ? 1 : 0,
      ]).stepReset();
      if (i % 250 === 0) onProgress?.('building', i);
    }
  } finally {
    stmt.finalize();
  }
  db.exec('COMMIT');
  onProgress?.('building', entries.length);

  // ── 3. Serialize to bytes ────────────────────────────────────────────────
  const pSaved = sqlite3.wasm.pstack.pointer;
  let dbBytes: Uint8Array;
  try {
    const pSize = sqlite3.wasm.pstack.alloc(8);
    const pData = sqlite3.capi.sqlite3_serialize(db.pointer, 'main', pSize, 0);
    if (!pData) throw new Error('sqlite3_serialize returned NULL');
    const rawSize = sqlite3.wasm.peek(pSize, 'i64');
    const size = Number(typeof rawSize === 'bigint' ? rawSize : rawSize);
    dbBytes = sqlite3.wasm.heap8u().slice(pData, pData + size);
    sqlite3.capi.sqlite3_free(pData);
  } finally {
    sqlite3.wasm.pstack.restore(pSaved);
    db.close();
  }

  // ── 4. Delete existing + upload ─────────────────────────────────────────
  onProgress?.('saving', 0);
  await deletePath(LOCATE_PATH).catch(() => {});
  await putFileContents(LOCATE_PATH, dbBytes);
  onProgress?.('saving', dbBytes.length);

  // Invalidate cached DB so the next search reloads the fresh file.
  resetLocateDb();

  return { count: entries.length, bytes: dbBytes.length };
}

export interface LocateEntry {
  path: string;
  name: string;
  size: number;
  mtime: number;
  is_dir: boolean;
}

/**
 * Convert a user wildcard query (* and ?) to a SQLite LIKE pattern.
 * Without wildcards, wraps in % for substring match.
 * SQL LIKE specials (% _ \) in the literal parts are escaped.
 */
function toSqlLike(query: string): string {
  const hasWildcard = /[*?]/.test(query);
  // Escape SQL LIKE special chars that the user did NOT type as wildcards
  const escaped = query.replace(/[\\%_]/g, '\\$&');
  if (!hasWildcard) return `%${escaped}%`;
  return escaped.replace(/\*/g, '%').replace(/\?/g, '_');
}

/**
 * Run a case-insensitive search against the loaded locate database.
 * Supports * (any chars) and ? (single char) wildcards.
 * Without wildcards, performs a substring match.
 * openLocateDb() must have been called (and resolved) before calling this.
 */
export function searchLocate(query: string, limit = 500): LocateEntry[] {
  if (!_db) throw new Error('Locate database is not loaded');
  const needle = toSqlLike(query);
  const rows: LocateEntry[] = [];
  _db.exec({
    sql: "SELECT path, size, mtime, is_dir FROM files WHERE path LIKE ? ESCAPE '\\' LIMIT ?",
    bind: [needle, limit],
    rowMode: 'array',
    callback: (row: any[]) => {
      rows.push({
        path: row[0] as string,
        name: basename(row[0] as string) || (row[0] as string),
        size: row[1] as number,
        mtime: row[2] as number,
        is_dir: (row[3] as number) !== 0,
      });
    },
  });
  return rows;
}