#!/usr/bin/env node

/**
 * XXX: we use Node.js native modules only here to avoid
 * requiring any runtime dependencies when folks install
 * @primer/css
 */

const fs = require('fs')
const {promisify} = require('util')
const readFile = promisify(fs.readFile)
const writeFile = promisify(fs.writeFile)
const {dirname, join} = require('path')

const IMPORT_PATTERN = /\@import\s+['"]([^'"]+)['"]/g
const replacements = [
  [/primer-marketing-(\w+)(\/lib)?/, '@primer/css/marketing/$1'],
  [/primer-(\w+)(\/lib)?/, '@primer/css/$1'],
  [/primer\b/, '@primer/css']
]

const paths = process.argv.slice(2)
const warn = (...args) => console.warn(...args)

if (paths.length) {
  Promise.all(
    paths.map(path => {
      return migrate(path).then(reps => report(reps, path))
    })
  ).catch(die)
} else {
  readFile('/dev/stdin', 'utf8')
    .then(input => {
      const [output, reps] = replace(input)
      report(reps, 'stdin')
      process.stdout.write(output)
    })
    .catch(die)
}

function migrate(path) {
  return readFile(path, 'utf8').then(input => {
    if (!IMPORT_PATTERN.test(input)) {
      warn(`No SCSS imports found in ${path}`)
      return false
    }

    const [output, reps] = replace(input)
    if (reps.length) {
      return writeFile(path, output, 'utf8').then(() => reps)
    } else {
      return false
    }
  })
}

function replace(input) {
  const reps = []
  const output = input.replace(IMPORT_PATTERN, (str, path) => {
    for (const [from, to] of replacements) {
      if (from.test(path)) {
        const replaced = str.replace(from, to)
        reps.push([path, path.replace(from, to)])
        return replaced
      }
    }
    return str
  })
  return [output, reps]
}

function report(reps, path) {
  if (reps.length) {
    warn(`Replaced ${reps.length} imports in ${path}:`)
    for (const [i, [from, to]] of Object.entries(reps)) {
      warn(`  ${Number(i) + 1}. (${from}) -> (${to})`)
    }
  } else {
    warn(`No legacy imports found in ${path}`)
  }
}

function die(error) {
  console.error(error)
  process.exitCode = 1
}