// 同步服务存储层：SQLite（node:sqlite 内置，零依赖）
import { DatabaseSync } from 'node:sqlite';
import fs from 'node:fs';
import path from 'node:path';

export const DATA_DIR = process.env.DATA_DIR || path.join(process.cwd(), 'data');
export const BLOB_DIR = path.join(DATA_DIR, 'blobs');
const DB_PATH = path.join(DATA_DIR, 'sync.db');

let db = null;

export function getDb() {
  if (db) return db;
  fs.mkdirSync(BLOB_DIR, { recursive: true });
  db = new DatabaseSync(DB_PATH);
  db.exec('PRAGMA journal_mode = WAL;');
  db.exec('PRAGMA foreign_keys = ON;');
  db.exec(`
CREATE TABLE IF NOT EXISTS users (
  id TEXT PRIMARY KEY,
  username TEXT NOT NULL UNIQUE,
  password_hash TEXT NOT NULL,
  salt TEXT NOT NULL,
  created_at TEXT NOT NULL DEFAULT (datetime('now','localtime'))
);

CREATE TABLE IF NOT EXISTS devices (
  id TEXT PRIMARY KEY,
  user_id TEXT NOT NULL REFERENCES users(id),
  name TEXT NOT NULL,
  last_seen_at TEXT NOT NULL DEFAULT (datetime('now','localtime')),
  UNIQUE(user_id, name)
);

CREATE TABLE IF NOT EXISTS tokens (
  token TEXT PRIMARY KEY,
  user_id TEXT NOT NULL REFERENCES users(id),
  device_id TEXT NOT NULL REFERENCES devices(id),
  created_at TEXT NOT NULL DEFAULT (datetime('now','localtime')),
  expires_at TEXT NOT NULL
);

-- 每行最新状态（按 user + table + row_uuid 唯一，LWW 胜者）
CREATE TABLE IF NOT EXISTS current (
  user_id TEXT NOT NULL,
  table_name TEXT NOT NULL,
  row_uuid TEXT NOT NULL,
  op TEXT NOT NULL,
  hlc TEXT NOT NULL,
  ms INTEGER NOT NULL,
  cnt INTEGER NOT NULL,
  dev TEXT NOT NULL,
  data TEXT,
  updated_seq INTEGER,
  PRIMARY KEY (user_id, table_name, row_uuid)
);

-- 全量变更历史（seq 单调递增，作为拉取游标基准）
CREATE TABLE IF NOT EXISTS changes (
  seq INTEGER PRIMARY KEY AUTOINCREMENT,
  user_id TEXT NOT NULL,
  table_name TEXT NOT NULL,
  row_uuid TEXT NOT NULL,
  op TEXT NOT NULL,
  hlc TEXT NOT NULL,
  data TEXT,
  created_at TEXT NOT NULL DEFAULT (datetime('now','localtime'))
);

CREATE INDEX IF NOT EXISTS idx_current_seq ON current(user_id, updated_seq);
CREATE INDEX IF NOT EXISTS idx_changes_user ON changes(user_id, seq);

-- 附件：内容寻址去重
CREATE TABLE IF NOT EXISTS attachments (
  user_id TEXT NOT NULL,
  sha256 TEXT NOT NULL,
  size INTEGER NOT NULL,
  mime TEXT,
  file_name TEXT,
  created_at TEXT NOT NULL DEFAULT (datetime('now','localtime')),
  PRIMARY KEY (user_id, sha256)
);
`);
  // 管理员与邀请码（动态颁发制；首个注册用户自动成为管理员）
  const hasAdmin = db.prepare("SELECT COUNT(*) AS c FROM pragma_table_info('users') WHERE name='is_admin'").get().c;
  if (Number(hasAdmin) === 0) db.exec("ALTER TABLE users ADD COLUMN is_admin INTEGER NOT NULL DEFAULT 0;");
  db.exec(`CREATE TABLE IF NOT EXISTS invite_codes (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    code TEXT NOT NULL UNIQUE,
    created_by TEXT,
    created_at TEXT NOT NULL DEFAULT (datetime('now','localtime')),
    used_by TEXT,
    used_at TEXT,
    valid INTEGER NOT NULL DEFAULT 1
  );`);
  const hasRemark = db.prepare("SELECT COUNT(*) AS c FROM pragma_table_info('invite_codes') WHERE name='remark'").get().c;
  if (Number(hasRemark) === 0) db.exec("ALTER TABLE invite_codes ADD COLUMN remark TEXT;");
  return db;
}

// 允许同步的表（与客户端 schema 对应；footprint_dimension 以 uuid 对作普通行同步）
export const SYNC_TABLES = new Set([
  'footprint', 'footprint_type', 'taxonomy', 'dimension', 'attachment',
  'semester', 'course_grade', 'metric_def', 'saved_view', 'footprint_dimension'
]);