import {promises as fs} from 'fs'
import * as path from 'path'
import type {UmzugStorage} from './contract'

const filesystem = {
  /** reads a file as a string or returns null if file doesn't exist */
  async readAsync(filepath: string) {
    return fs.readFile(filepath).then(
      c => c.toString(),
      () => null,
    )
  },
  /** writes a string as file contents, creating its parent directory if necessary */
  async writeAsync(filepath: string, content: string) {
    await fs.mkdir(path.dirname(filepath), {recursive: true})
    await fs.writeFile(filepath, content)
  },
}

export type JSONStorageConstructorOptions = {
  /**
	Path to JSON file where the log is stored.

	@default './umzug.json'
	*/
  readonly path?: string
}

export class JSONStorage implements UmzugStorage {
  public readonly path: string

  constructor(options?: JSONStorageConstructorOptions) {
    this.path = options?.path ?? path.join(process.cwd(), 'umzug.json')
  }

  async logMigration({name: migrationName}: {name: string}): Promise<void> {
    const loggedMigrations = await this.executed()
    loggedMigrations.push(migrationName)

    await filesystem.writeAsync(this.path, JSON.stringify(loggedMigrations, null, 2))
  }

  async unlogMigration({name: migrationName}: {name: string}): Promise<void> {
    const loggedMigrations = await this.executed()
    const updatedMigrations = loggedMigrations.filter(name => name !== migrationName)

    await filesystem.writeAsync(this.path, JSON.stringify(updatedMigrations, null, 2))
  }

  async executed(): Promise<string[]> {
    const content = await filesystem.readAsync(this.path)
    return content ? (JSON.parse(content) as string[]) : []
  }
}