// Use the asm.js build — pure JS, no .wasm file, works from file://
import initSqlJs from 'sql.js/dist/sql-asm.js';
import type { Database } from 'sql.js';
import type { KVRecord, DocRecord, IndexDefinition } from './types.js';
import { extractIndexValue } from './utils.js';

// ── Value serialization ──────────────────────────────────────

function serializeIndexValue(v: unknown): unknown {
  if (typeof v === 'number' || typeof v === 'string') return v;
  if (v instanceof Date) return v.getTime();
  if (Array.isArray(v)) return JSON.stringify(v);
  return String(v);
}

// ── SqlJsStore ───────────────────────────────────────────────

export class SqlJsStore {
  private constructor(private db: Database) {}

  // ── Open ───────────────────────────────────────────────────

  static async open(
    _name: string,
    existingData?: Uint8Array,
  ): Promise<SqlJsStore> {
    // sql.js asm.js build: no .wasm file, no fetch, no headers
    const SQL = await initSqlJs();
    const db = existingData
      ? new SQL.Database(existingData)
      : new SQL.Database();
    const store = new SqlJsStore(db);
    store.createSchema(); // no-op if tables already exist (IF NOT EXISTS)
    return store;
  }

  // ── Disk persistence ────────────────────────────────────────

  /** Export the entire SQLite database as a binary Uint8Array. */
  exportDB(): Uint8Array {
    return this.db.export();
  }

  private createSchema(): void {
    this.db.run(`
      CREATE TABLE IF NOT EXISTS kv (
        key   TEXT PRIMARY KEY,
        value TEXT NOT NULL,
        ts    INTEGER NOT NULL,
        rev   INTEGER NOT NULL
      );
      CREATE TABLE IF NOT EXISTS docs (
        store   TEXT NOT NULL,
        id      TEXT NOT NULL,
        data    TEXT NOT NULL,
        ts      INTEGER NOT NULL,
        rev     INTEGER NOT NULL,
        deleted INTEGER NOT NULL DEFAULT 0,
        PRIMARY KEY (store, id)
      );
      CREATE INDEX IF NOT EXISTS docs_by_store
        ON docs (store) WHERE deleted = 0;
      CREATE TABLE IF NOT EXISTS idx_entries (
        store      TEXT NOT NULL,
        index_name TEXT NOT NULL,
        id         TEXT NOT NULL,
        value      ANY,
        PRIMARY KEY (store, index_name, id)
      );
      CREATE INDEX IF NOT EXISTS idx_lookup
        ON idx_entries (store, index_name, value);
      CREATE INDEX IF NOT EXISTS idx_by_doc
        ON idx_entries (store, id);
      CREATE TABLE IF NOT EXISTS applied (
        filename   TEXT PRIMARY KEY,
        applied_at INTEGER NOT NULL
      );
      CREATE TABLE IF NOT EXISTS meta (
        key   TEXT PRIMARY KEY,
        value TEXT
      );
    `);
  }

  // ── KV operations ──────────────────────────────────────────

  async getKV(key: string): Promise<KVRecord | undefined> {
    const rows = this.query(
      'SELECT key, value, ts, rev FROM kv WHERE key = ?',
      [key],
    );
    if (rows.length === 0) return undefined;
    const r = rows[0];
    return {
      key: r.key as string,
      value: JSON.parse(r.value as string),
      ts: r.ts as number,
      rev: r.rev as number,
    };
  }

  async putKV(record: KVRecord): Promise<void> {
    this.db.run(
      'INSERT OR REPLACE INTO kv (key, value, ts, rev) VALUES (?,?,?,?)',
      [record.key, JSON.stringify(record.value), record.ts, record.rev],
    );
  }

  async deleteKV(key: string): Promise<void> {
    this.db.run('DELETE FROM kv WHERE key = ?', [key]);
  }

  async getAllKVKeys(): Promise<string[]> {
    return this.query('SELECT key FROM kv').map((r) => r.key as string);
  }

  async getAllKVEntries(): Promise<KVRecord[]> {
    return this.query('SELECT key, value, ts, rev FROM kv').map((r) => ({
      key: r.key as string,
      value: JSON.parse(r.value as string),
      ts: r.ts as number,
      rev: r.rev as number,
    }));
  }

  // ── Doc operations ─────────────────────────────────────────

  async getDoc(store: string, id: string): Promise<DocRecord | undefined> {
    const rows = this.query(
      'SELECT store, id, data, ts, rev, deleted FROM docs WHERE store = ? AND id = ? AND deleted = 0',
      [store, id],
    );
    if (rows.length === 0) return undefined;
    return this.rowToDoc(rows[0]);
  }

  async getRawDoc(store: string, id: string): Promise<DocRecord | undefined> {
    const rows = this.query(
      'SELECT store, id, data, ts, rev, deleted FROM docs WHERE store = ? AND id = ?',
      [store, id],
    );
    if (rows.length === 0) return undefined;
    return this.rowToDoc(rows[0]);
  }

  async putDoc(record: DocRecord, indexes: IndexDefinition[]): Promise<void> {
    this.db.run(
      `INSERT OR REPLACE INTO docs (store, id, data, ts, rev, deleted)
       VALUES (?,?,?,?,?,?)`,
      [
        record.store,
        record.id,
        JSON.stringify(record.data),
        record.ts,
        record.rev,
        record.deleted ? 1 : 0,
      ],
    );

    // Update index entries
    this.db.run(
      'DELETE FROM idx_entries WHERE store = ? AND id = ?',
      [record.store, record.id],
    );

    if (!record.deleted) {
      for (const def of indexes) {
        const val = extractIndexValue(record.data, def.fields as string[]);
        if (val !== undefined) {
          this.db.run(
            `INSERT OR REPLACE INTO idx_entries (store, index_name, id, value)
             VALUES (?,?,?,?)`,
            [record.store, def.name, record.id, serializeIndexValue(val)],
          );
        }
      }
    }
  }

  async deleteDoc(
    store: string,
    id: string,
    ts: number,
    rev: number,
    indexes: IndexDefinition[],
  ): Promise<void> {
    return this.putDoc(
      { store, id, data: null, ts, rev, deleted: true },
      indexes,
    );
  }

  async getAllDocs(store: string): Promise<DocRecord[]> {
    return this.query(
      'SELECT store, id, data, ts, rev, deleted FROM docs WHERE store = ? AND deleted = 0',
      [store],
    ).map((r) => this.rowToDoc(r));
  }

  // ── Index queries ──────────────────────────────────────────

  async findByIndex(
    store: string,
    indexName: string,
    value: unknown,
  ): Promise<string[]> {
    return this.query(
      'SELECT id FROM idx_entries WHERE store = ? AND index_name = ? AND value = ?',
      [store, indexName, serializeIndexValue(value)],
    ).map((r) => r.id as string);
  }

  async queryByIndex(
    store: string,
    indexName: string,
    range: { gt?: unknown; gte?: unknown; lt?: unknown; lte?: unknown },
  ): Promise<string[]> {
    const conditions = ['store = ?', 'index_name = ?'];
    const params: unknown[] = [store, indexName];

    if (range.gte !== undefined) {
      conditions.push('value >= ?');
      params.push(serializeIndexValue(range.gte));
    } else if (range.gt !== undefined) {
      conditions.push('value > ?');
      params.push(serializeIndexValue(range.gt));
    }

    if (range.lte !== undefined) {
      conditions.push('value <= ?');
      params.push(serializeIndexValue(range.lte));
    } else if (range.lt !== undefined) {
      conditions.push('value < ?');
      params.push(serializeIndexValue(range.lt));
    }

    return this.query(
      `SELECT id FROM idx_entries WHERE ${conditions.join(' AND ')}`,
      params,
    ).map((r) => r.id as string);
  }

  async rebuildIndexes(
    store: string,
    indexes: IndexDefinition[],
  ): Promise<void> {
    this.db.run('DELETE FROM idx_entries WHERE store = ?', [store]);

    const docs = this.query(
      'SELECT id, data FROM docs WHERE store = ? AND deleted = 0',
      [store],
    );

    for (const row of docs) {
      const data = JSON.parse(row.data as string);
      for (const def of indexes) {
        const val = extractIndexValue(data, def.fields as string[]);
        if (val !== undefined) {
          this.db.run(
            `INSERT OR REPLACE INTO idx_entries (store, index_name, id, value)
             VALUES (?,?,?,?)`,
            [store, def.name, row.id, serializeIndexValue(val)],
          );
        }
      }
    }
  }

  // ── Applied-event tracking ─────────────────────────────────

  async isEventApplied(filename: string): Promise<boolean> {
    return (
      this.query('SELECT 1 FROM applied WHERE filename = ?', [filename])
        .length > 0
    );
  }

  async markEventApplied(filename: string): Promise<void> {
    this.db.run(
      'INSERT OR IGNORE INTO applied (filename, applied_at) VALUES (?,?)',
      [filename, Date.now()],
    );
  }

  async getAppliedSet(): Promise<Set<string>> {
    const rows = this.query('SELECT filename FROM applied');
    return new Set(rows.map((r) => r.filename as string));
  }

  // ── Meta ───────────────────────────────────────────────────

  async getMeta<T = unknown>(key: string): Promise<T | undefined> {
    const rows = this.query('SELECT value FROM meta WHERE key = ?', [key]);
    if (rows.length === 0) return undefined;
    const raw = rows[0].value as string | null;
    if (raw === null) return undefined;
    return JSON.parse(raw) as T;
  }

  async setMeta(key: string, value: unknown): Promise<void> {
    this.db.run('INSERT OR REPLACE INTO meta (key, value) VALUES (?,?)', [
      key,
      JSON.stringify(value),
    ]);
  }

  // ── Lifecycle ──────────────────────────────────────────────

  close(): void {
    this.db.close();
  }

  // ── Helpers ────────────────────────────────────────────────

  private query(
    sql: string,
    params?: unknown[],
  ): Record<string, unknown>[] {
    const results = this.db.exec(sql, params);
    if (results.length === 0) return [];
    const { columns, values } = results[0];
    return values.map((row) => {
      const obj: Record<string, unknown> = {};
      for (let i = 0; i < columns.length; i++) {
        obj[columns[i]] = row[i];
      }
      return obj;
    });
  }

  private rowToDoc(row: Record<string, unknown>): DocRecord {
    return {
      store: row.store as string,
      id: row.id as string,
      data: JSON.parse(row.data as string),
      ts: row.ts as number,
      rev: row.rev as number,
      deleted: (row.deleted as number) === 1,
    };
  }
}