import fs from 'node:fs'
import path from 'node:path'
import { parse } from 'yaml'
import type { Plugin } from 'vite'

const I18N_SOURCE_DIR = 'public/i18n'
const SOURCE_RELATIVE_PATH = `${I18N_SOURCE_DIR}/en.yml`
const UNIVERSAL_OUTPUT_RELATIVE_PATH = 'src/universal/types/i18n.d.ts'
const RENDERER_OUTPUT_RELATIVE_PATH = 'src/renderer/i18n/i18next.d.ts'

function formatKey (key: string) {
  return /^[A-Za-z_$][A-Za-z0-9_$]*$/.test(key) ? key : JSON.stringify(key)
}

function readTranslationKeys (sourcePath: string) {
  if (!fs.existsSync(sourcePath)) {
    return []
  }

  const raw = fs.readFileSync(sourcePath, 'utf8')
  const data = parse(raw)

  if (!data || typeof data !== 'object' || Array.isArray(data)) {
    return []
  }

  return Object.keys(data as Record<string, unknown>)
}

function buildUniversalTypeContent (keys: string[]) {
  const uniqueKeys = Array.from(new Set(keys))
  const lines = uniqueKeys.map((key) => `  ${formatKey(key)}: string`)

  return `// This file is auto-generated by vite-plugin-i18n-types. Do not edit.
interface ILocales {
${lines.join('\n')}
}

type ILocalesKey = keyof ILocales
`
}

function buildRendererTypeContent () {
  return `// This file is auto-generated by vite-plugin-i18n-types. Do not edit.
import "i18next"

declare module "i18next" {
  interface CustomTypeOptions {
    resources: {
      translation: ILocales
    }
  }
}
`
}

function writeFileIfChanged (outputPath: string, nextContent: string) {
  const previousContent = fs.existsSync(outputPath)
    ? fs.readFileSync(outputPath, 'utf8')
    : ''

  if (previousContent === nextContent) {
    return
  }

  fs.mkdirSync(path.dirname(outputPath), { recursive: true })
  fs.writeFileSync(outputPath, nextContent, 'utf8')
}

function writeTypesFiles (sourcePath: string, universalOutputPath: string, rendererOutputPath: string) {
  const keys = readTranslationKeys(sourcePath)
  writeFileIfChanged(universalOutputPath, buildUniversalTypeContent(keys))
  writeFileIfChanged(rendererOutputPath, buildRendererTypeContent())
}

export function i18nTypesPlugin (): Plugin {
  let sourcePath = ''
  let universalOutputPath = ''
  let rendererOutputPath = ''
  let projectRoot = ''

  const generate = () => {
    try {
      writeTypesFiles(sourcePath, universalOutputPath, rendererOutputPath)
    } catch (error) {
      const message = error instanceof Error ? error.message : String(error)
      console.error(`[vite-plugin-i18n-types] ${message}`)
    }
  }

  return {
    name: 'vite-plugin-i18n-types',
    enforce: 'pre',
    configResolved (config) {
      projectRoot = path.resolve(config.root, '../..')
      sourcePath = path.resolve(projectRoot, SOURCE_RELATIVE_PATH)
      universalOutputPath = path.resolve(projectRoot, UNIVERSAL_OUTPUT_RELATIVE_PATH)
      rendererOutputPath = path.resolve(projectRoot, RENDERER_OUTPUT_RELATIVE_PATH)
    },
    buildStart () {
      generate()
    },
    configureServer (server) {
      server.watcher.add(path.resolve(projectRoot, I18N_SOURCE_DIR))
    },
    handleHotUpdate ({ file }) {
      const normalizedFile = path.resolve(file)
      const normalizedSourceDir = path.resolve(path.dirname(sourcePath))

      if (normalizedFile.startsWith(normalizedSourceDir)) {
        generate()
      }
    }
  }
}