import {
    Kysely,
    Migrator,
    PostgresDialect,
    FileMigrationProvider
} from 'npm:kysely'

/// <reference types="npm:@types/pg" />
import pg from "npm:pg";
import { Database } from "./scheme.ts"
import { CompiledConfig } from "../cfg/config.ts";


export const dropDb = async (migrator: Migrator, downLimit?: number) => {
  console.log(`droping the DB`)
  let downCounter: number = 0 // to prevent infinite loop
  while (true) {
    if (downLimit && downCounter === downLimit) return
    const { results } = await migrator.migrateDown()
    if (!results) continue

    for (const { status, migrationName } of results) {
      if (status === "Error" || status === "NotExecuted") {
        return
      }
      console.log(`down migration "${migrationName}" was executed successfully`)
    }
    downCounter++
  }
}


export type SetupDbOutput = {
    pool: pg.Pool,
    db: Kysely<Database>,
}
export const setupDB = async (cfg: CompiledConfig): Promise<SetupDbOutput> => {
  console.log("creating db instance: ", cfg.pgPoolCfg)
  const pool = new pg.Pool(cfg.pgPoolCfg)
  const dialect = new PostgresDialect({ pool })
  const db = new Kysely<Database>({ dialect })

  if (cfg.migrationCfg?.applyMigrations) {
    console.log("applying db migrations", cfg.migrationCfg.migrationsPath)
    const migrator = new Migrator({
      db,
      provider: new FileMigrationProvider({
        fs: {
          readdir(path) {
            return Promise.resolve(
              [...Deno.readDirSync(path)].map((file) => file.name)
            )
          },
        },
        path: {
          join(...path) {
            return path.join('/')
          },
        },
        migrationFolder: cfg.migrationCfg.migrationsPath,
      }),
      allowUnorderedMigrations: true
    })

    if (cfg.migrationCfg.dropDb) {
      await dropDb(migrator, 100)
    }
    const { error, results } = await migrator.migrateToLatest()

    results?.forEach((it) => {
      if (it.status === 'Success') {
        console.log(`migration "${it.migrationName}" was executed successfully`)
      } else if (it.status === 'Error') {
        console.error(`failed to execute migration "${it.migrationName}"`)
      }
    })
  
    if (error) {
      console.error('failed to migrate')
      console.error(error)
      throw error
    }
  }

  return { pool, db }
}