import Database from 'better-sqlite3'
import { mkdirSync } from 'fs'
import { dirname } from 'path'
import type { SessionMeta } from '../../types/session.js'

export interface ListFilters {
  days?: number
  project?: string
  tool?: string
  skill?: string
  q?: string
  limit?: number
  offset?: number
}

export interface SessionsDb {
  upsertSession(meta: SessionMeta): void
  listSessions(filters: ListFilters): SessionMeta[]
  countSessions(filters: ListFilters): number
  getSession(id: string): SessionMeta | null
  deleteByJsonlPath(path: string): void
  close(): void
}

const SCHEMA = `
CREATE TABLE IF NOT EXISTS sessions (
  session_id      TEXT PRIMARY KEY,
  project_path    TEXT NOT NULL,
  project_slug    TEXT NOT NULL,
  jsonl_path      TEXT NOT NULL UNIQUE,
  started_at      TEXT NOT NULL,
  ended_at        TEXT,
  duration_sec    INTEGER,
  event_count     INTEGER NOT NULL,
  user_messages   INTEGER NOT NULL,
  assistant_msgs  INTEGER NOT NULL,
  tool_calls      INTEGER NOT NULL,
  first_prompt    TEXT,
  tools_used      TEXT NOT NULL,
  skills_invoked  TEXT NOT NULL,
  outcome         TEXT NOT NULL,
  permission_mode TEXT,
  file_size       INTEGER NOT NULL,
  indexed_at      TEXT NOT NULL
);
CREATE INDEX IF NOT EXISTS idx_started ON sessions(started_at DESC);
CREATE INDEX IF NOT EXISTS idx_project ON sessions(project_slug, started_at DESC);
`

function rowToMeta(row: Record<string, unknown>): SessionMeta {
  return {
    session_id: row.session_id as string,
    project_path: row.project_path as string,
    project_slug: row.project_slug as string,
    jsonl_path: row.jsonl_path as string,
    started_at: row.started_at as string,
    ended_at: (row.ended_at as string | null) ?? null,
    duration_sec: (row.duration_sec as number | null) ?? null,
    event_count: row.event_count as number,
    user_messages: row.user_messages as number,
    assistant_msgs: row.assistant_msgs as number,
    tool_calls: row.tool_calls as number,
    first_prompt: (row.first_prompt as string | null) ?? null,
    tools_used: JSON.parse(row.tools_used as string),
    skills_invoked: JSON.parse(row.skills_invoked as string),
    outcome: row.outcome as SessionMeta['outcome'],
    permission_mode: (row.permission_mode as string | null) ?? null,
    file_size: row.file_size as number,
    indexed_at: row.indexed_at as string,
  }
}

function buildWhere(f: ListFilters): { sql: string; params: Record<string, unknown> } {
  const parts: string[] = []
  const params: Record<string, unknown> = {}
  if (f.days) {
    const cutoff = new Date(Date.now() - f.days * 86400_000).toISOString()
    parts.push('started_at >= @cutoff')
    params.cutoff = cutoff
  }
  if (f.project) {
    parts.push('project_slug = @project')
    params.project = f.project
  }
  if (f.tool) {
    parts.push("tools_used LIKE @toolLike")
    params.toolLike = `%"${f.tool}"%`
  }
  if (f.skill) {
    parts.push('skills_invoked LIKE @skillLike')
    params.skillLike = `%"${f.skill}"%`
  }
  if (f.q) {
    parts.push('first_prompt LIKE @q')
    params.q = `%${f.q}%`
  }
  return {
    sql: parts.length ? 'WHERE ' + parts.join(' AND ') : '',
    params,
  }
}

export function openSessionsDb(dbPath: string): SessionsDb {
  mkdirSync(dirname(dbPath), { recursive: true })
  const db = new Database(dbPath)
  db.pragma('journal_mode = WAL')
  db.exec(SCHEMA)

  const upsertStmt = db.prepare(`
    INSERT INTO sessions (session_id, project_path, project_slug, jsonl_path, started_at, ended_at,
      duration_sec, event_count, user_messages, assistant_msgs, tool_calls, first_prompt,
      tools_used, skills_invoked, outcome, permission_mode, file_size, indexed_at)
    VALUES (@session_id, @project_path, @project_slug, @jsonl_path, @started_at, @ended_at,
      @duration_sec, @event_count, @user_messages, @assistant_msgs, @tool_calls, @first_prompt,
      @tools_used, @skills_invoked, @outcome, @permission_mode, @file_size, @indexed_at)
    ON CONFLICT(session_id) DO UPDATE SET
      project_path = excluded.project_path,
      project_slug = excluded.project_slug,
      jsonl_path = excluded.jsonl_path,
      started_at = excluded.started_at,
      ended_at = excluded.ended_at,
      duration_sec = excluded.duration_sec,
      event_count = excluded.event_count,
      user_messages = excluded.user_messages,
      assistant_msgs = excluded.assistant_msgs,
      tool_calls = excluded.tool_calls,
      first_prompt = excluded.first_prompt,
      tools_used = excluded.tools_used,
      skills_invoked = excluded.skills_invoked,
      outcome = excluded.outcome,
      permission_mode = excluded.permission_mode,
      file_size = excluded.file_size,
      indexed_at = excluded.indexed_at
  `)

  return {
    upsertSession(meta) {
      upsertStmt.run({
        ...meta,
        tools_used: JSON.stringify(meta.tools_used),
        skills_invoked: JSON.stringify(meta.skills_invoked),
      })
    },
    listSessions(filters) {
      const { sql, params } = buildWhere(filters)
      const limit = filters.limit ?? 50
      const offset = filters.offset ?? 0
      const rows = db
        .prepare(`SELECT * FROM sessions ${sql} ORDER BY started_at DESC LIMIT @limit OFFSET @offset`)
        .all({ ...params, limit, offset }) as Record<string, unknown>[]
      return rows.map(rowToMeta)
    },
    countSessions(filters) {
      const { sql, params } = buildWhere(filters)
      const row = db.prepare(`SELECT COUNT(*) as c FROM sessions ${sql}`).get(params) as { c: number }
      return row.c
    },
    getSession(id) {
      const row = db.prepare('SELECT * FROM sessions WHERE session_id = ?').get(id) as Record<string, unknown> | undefined
      return row ? rowToMeta(row) : null
    },
    deleteByJsonlPath(path) {
      db.prepare('DELETE FROM sessions WHERE jsonl_path = ?').run(path)
    },
    close() {
      db.close()
    },
  }
}