import fs from 'node:fs/promises'
import { dirname, resolve } from 'node:path'
import { type Plugin, type Root } from 'postcss'
import { parseImportParams } from '../../../tailwindcss/src/at-import'
import { segment } from '../../../tailwindcss/src/utils/segment'
import * as ValueParser from '../../../tailwindcss/src/value-parser'

export function migrateImport(): Plugin {
  async function migrate(root: Root) {
    let file = root.source?.input.file
    if (!file) return

    let promises: Promise<void>[] = []
    root.walkAtRules('import', (rule) => {
      let [firstParam, ...rest] = segment(rule.params, ' ')

      let params = parseImportParams(ValueParser.parse(firstParam))

      let isRelative = params.uri[0] === '.'
      let hasCssExtension = params.uri.endsWith('.css')

      if (isRelative && hasCssExtension) {
        return
      }

      let fullPath = resolve(dirname(file), params.uri)
      if (!hasCssExtension) fullPath += '.css'

      promises.push(
        fs.stat(fullPath).then(() => {
          let ext = hasCssExtension ? '' : '.css'
          let path = isRelative ? params.uri : `./${params.uri}`
          rule.params = [`'${path}${ext}'`, ...rest].join(' ')
        }),
      )
    })

    await Promise.allSettled(promises)
  }

  return {
    postcssPlugin: '@tailwindcss/upgrade/migrate-import',
    OnceExit: migrate,
  }
}