import * as fs from 'fs-jetpack'
import { PackageJson } from 'type-fest'

type PackageJsonUpdater = (packageJson: Record<string, any>) => Record<string, any>

/**
 * Read and validate the package.json from CWD.
 */
export async function getPackageJson(): Promise<ValidatedPackageJson> {
  const pj = await read(process.cwd())
  return validate(pj)
}

/**
 * Read and validate the package.json from CWD.
 */
export function getPackageJsonSync(): ValidatedPackageJson {
  const pj = readSync(process.cwd())
  return validate(pj)
}

type ValidatedPackageJson = PackageJson & { name: string }

/**
 * Validate that the given package json is defined, has a valid name property.
 */
function validate(pj: PackageJson | undefined): ValidatedPackageJson {
  if (!pj) {
    throw new Error('Could not find pacakge.json')
  }

  if (pj.name === undefined) {
    throw new Error('pacakge.json is missing name field')
  }

  if (pj.name === '') {
    throw new Error('pacakge.json name field is empty')
  }

  return pj as ValidatedPackageJson
}

/**
 * Read the package.json file.
 */
export async function read(cwd: string): Promise<undefined | PackageJson> {
  return fs.readAsync(fs.path(cwd, 'package.json'), 'json')

  // if (!packageJson) {
  //   throw new Error(
  //     `Looked for but could not find a package.json file at ${packageJsonPath}. This file is required for publishing to the npm registry.`
  //   )
  // }

  // if (typeof packageJson !== 'object') {
  //   throw new Error(
  //     `Found a package.json file at ${packageJsonPath} but it appears to be malformed. It did not parse into an object but rather: ${packageJson}`
  //   )
  // }
}

/**
 * Read the package.json file synchronously.
 */
export function readSync(cwd: string): undefined | PackageJson {
  return fs.read(fs.path(cwd, 'package.json'), 'json')
}

/**
 * Write the package.json file.
 */
export async function write(cwd: string, object: object): Promise<void> {
  return fs.writeAsync(fs.path(cwd, 'package.json'), object)
}

/**
 * Update the package.json located at cwd. The given updater function will
 * receive the parsed package contents and whatever is returned will be written
 * to disk.
 */
export async function update(cwd: string, updater: PackageJsonUpdater): Promise<void> {
  const packageJson = await read(cwd)
  if (packageJson) {
    const packageJsonUpdated = await updater(packageJson)
    await fs.writeAsync(fs.path(cwd, 'package.json'), packageJsonUpdated)
  }
}

export function create(cwd?: string) {
  cwd = cwd ?? process.cwd()
  return {
    read: read.bind(null, cwd),
    readSync: readSync.bind(null, cwd),
    write: write.bind(null, cwd),
    update: update.bind(null, cwd),
  }
}

export type PJ = ReturnType<typeof create>