// ============================================================
// data_gateway/store.js - 数据存储模块
// 职责：动态创建/管理每个 skill 的独立 SQLite 数据库
// 表结构：id | source | data(JSON) | created_at
// 支持 mode: "append"（增量追加）和 "latest"（覆盖最新）
// ============================================================
const Database = require('better-sqlite3')
const fs = require('fs')
const path = require('path')

const DATA_DIR = path.join(process.cwd(), 'data', 'ingest')
if (!fs.existsSync(DATA_DIR)) fs.mkdirSync(DATA_DIR, { recursive: true })

// 已打开的数据库连接缓存
const dbCache = new Map()

const getDbPath = (skillId) => path.join(DATA_DIR, `${skillId}.db`)

const getOrOpenDb = (skillId) => {
  if (dbCache.has(skillId)) return dbCache.get(skillId)
  const dbPath = getDbPath(skillId)
  const db = new Database(dbPath)
  // 启用 WAL 模式提高并发写入性能
  db.pragma('journal_mode = WAL')
  db.pragma('synchronous = NORMAL')
  db.exec(
    `CREATE TABLE IF NOT EXISTS records (
      id INTEGER PRIMARY KEY AUTOINCREMENT,
      source TEXT NOT NULL DEFAULT '',
      data TEXT NOT NULL,
      created_at TEXT NOT NULL DEFAULT (datetime('now'))
    )`
  )
  db.exec(`CREATE INDEX IF NOT EXISTS idx_records_created ON records(created_at DESC)`)
  dbCache.set(skillId, db)
  return db
}

// 写入一条记录
const insert = (skillId, { source = '', data = {} }) => {
  const db = getOrOpenDb(skillId)
  const dataStr = JSON.stringify(data)
  const info = db.prepare(`INSERT INTO records (source, data) VALUES (?, ?)`).run(
    String(source || ''), dataStr
  )
  return { id: info.lastInsertRowid, source, data, created_at: new Date().toISOString() }
}

// 覆盖写入（mode: "latest"）- 先删后插，保证只有一条
const upsertLatest = (skillId, { source = '', data = {} }) => {
  const db = getOrOpenDb(skillId)
  const dataStr = JSON.stringify(data)
  const tx = db.transaction(() => {
    db.prepare(`DELETE FROM records`).run()
    return db.prepare(`INSERT INTO records (source, data) VALUES (?, ?)`).run(
      String(source || ''), dataStr
    )
  })
  const info = tx()
  return { id: info.lastInsertRowid, source, data, created_at: new Date().toISOString() }
}

// 查询最新一条记录
const queryLatest = (skillId) => {
  const db = getOrOpenDb(skillId)
  const row = db.prepare(`SELECT * FROM records ORDER BY id DESC LIMIT 1`).get()
  if (!row) return null
  try { row.data = JSON.parse(row.data) } catch { /* keep as string */ }
  return row
}

// 查询记录列表（分页）
const queryList = (skillId, { limit = 100, offset = 0, source = null } = {}) => {
  const db = getOrOpenDb(skillId)
  let sql = `SELECT * FROM records`
  const params = []
  if (source) {
    sql += ` WHERE source = ?`
    params.push(String(source))
  }
  sql += ` ORDER BY id DESC LIMIT ? OFFSET ?`
  params.push(Math.min(Number(limit) || 100, 1000), Math.max(0, Number(offset) || 0))
  const rows = db.prepare(sql).all(...params)
  for (const row of rows) {
    try { row.data = JSON.parse(row.data) } catch { /* keep as string */ }
  }
  const total = db.prepare(`SELECT COUNT(*) as cnt FROM records`).get().cnt
  return { rows, total }
}

// 按时间范围查询
const queryByTimeRange = (skillId, { start, end, limit = 100 } = {}) => {
  const db = getOrOpenDb(skillId)
  let sql = `SELECT * FROM records WHERE 1=1`
  const params = []
  if (start) { sql += ` AND created_at >= ?`; params.push(String(start)) }
  if (end) { sql += ` AND created_at <= ?`; params.push(String(end)) }
  sql += ` ORDER BY id DESC LIMIT ?`
  params.push(Math.min(Number(limit) || 100, 1000))
  const rows = db.prepare(sql).all(...params)
  for (const row of rows) {
    try { row.data = JSON.parse(row.data) } catch { /* keep as string */ }
  }
  return { rows, total: rows.length }
}

// 获取记录总数
const count = (skillId) => {
  const db = getOrOpenDb(skillId)
  return db.prepare(`SELECT COUNT(*) as cnt FROM records`).get().cnt
}

// 关闭所有数据库连接
const closeAll = () => {
  for (const [skillId, db] of dbCache) {
    try { db.close() } catch {}
    dbCache.delete(skillId)
  }
}

module.exports = {
  insert, upsertLatest, queryLatest, queryList, queryByTimeRange, count, closeAll, getDbPath, getOrOpenDb
}