import { Inject, Injectable, Logger, OnModuleDestroy, OnModuleInit, Optional } from '@nestjs/common'
import { ConfigService } from '@nestjs/config'
import Database from 'better-sqlite3'
import { mkdirSync } from 'node:fs'
import { dirname, join } from 'node:path'
import { EXPECTED_TABLES, listUserTables, runSchemaMigrations } from './migration.service'

@Injectable()
export class DatabaseService implements OnModuleInit, OnModuleDestroy {
  private readonly logger = new Logger(DatabaseService.name)
  private db: Database.Database | null = null
  private readonly dbPath: string

  constructor(@Optional() @Inject(ConfigService) private readonly config?: ConfigService) {
    const configured = this.config?.get<string>('DB_PATH') ?? process.env.DB_PATH
    this.dbPath = configured ?? join(process.cwd(), 'data', 'app.db')
  }

  onModuleInit(): void {
    mkdirSync(dirname(this.dbPath), { recursive: true })
    this.db = new Database(this.dbPath)
    this.db.pragma('journal_mode = WAL')
    runSchemaMigrations(this.db)
    this.logger.log(`SQLite ready at ${this.dbPath}`)
  }

  onModuleDestroy(): void {
    if (this.db) {
      this.db.close()
      this.db = null
      this.logger.log('SQLite connection closed')
    }
  }

  getDbPath(): string {
    return this.dbPath
  }

  getDb(): Database.Database {
    if (!this.db) {
      throw new Error('Database is not initialized')
    }
    return this.db
  }

  transaction<T>(fn: () => T): T {
    return this.getDb().transaction(fn)()
  }

  verifyMigrationsApplied(): { ok: boolean; tables: string[]; missing: string[] } {
    const tables = listUserTables(this.getDb())
    const missing = EXPECTED_TABLES.filter((name) => !tables.includes(name))
    return { ok: missing.length === 0, tables, missing }
  }
}