#!/usr/bin/env node
import { readFileSync, writeFileSync } from 'node:fs'
import { resolve } from 'node:path'

const SECTION_BY_TYPE = {
  added: 'Added',
  changed: 'Changed',
  deprecated: 'Deprecated',
  removed: 'Removed',
  fixed: 'Fixed',
  security: 'Security',
}

function usage() {
  console.error(
    [
      'Usage:',
      '  pnpm changelog:add -- --type fixed --message "Fix thing"',
      '',
      `Types: ${Object.keys(SECTION_BY_TYPE).join(', ')}`,
    ].join('\n')
  )
  process.exit(1)
}

function argValue(name) {
  const index = process.argv.indexOf(`--${name}`)
  if (index === -1) return null
  return process.argv[index + 1] ?? null
}

const type = argValue('type')?.toLowerCase()
const message = argValue('message')?.trim()

if (!type || !message || !SECTION_BY_TYPE[type]) {
  usage()
}

const section = SECTION_BY_TYPE[type]
const changelogPath = resolve('CHANGELOG.md')
let changelog = readFileSync(changelogPath, 'utf8')

if (!/^## \[Unreleased\]/m.test(changelog)) {
  changelog = changelog.replace(/(\r?\n)(## \[[^\r\n]+\])/, `$1## [Unreleased]$1$1$2`)
}

// JS regex has no \z anchor, so match to the next version heading or true
// end-of-input ($ with nothing following — \n-tolerant under the m flag).
const unreleasedMatch = changelog.match(/^## \[Unreleased\][\s\S]*?(?=^## \[|$(?![\s\S]))/m)
if (!unreleasedMatch) {
  throw new Error('Could not find or create an Unreleased section.')
}

const unreleased = unreleasedMatch[0]
const lineEnding = changelog.includes('\r\n') ? '\r\n' : '\n'
const bullet = `- ${message}`

let nextUnreleased
const sectionRegex = new RegExp(`(^### ${section}\\s*)([\\s\\S]*?)(?=^### |$(?![\\s\\S]))`, 'm')
const sectionMatch = unreleased.match(sectionRegex)

if (sectionMatch) {
  const body = sectionMatch[2].trimEnd()
  const replacement = `${sectionMatch[1]}${body ? `${body}${lineEnding}` : ''}${bullet}${lineEnding}${lineEnding}`
  nextUnreleased = unreleased.replace(sectionRegex, replacement)
} else {
  const insert = `${lineEnding}### ${section}${lineEnding}${lineEnding}${bullet}${lineEnding}`
  nextUnreleased = unreleased.trimEnd() + insert + lineEnding
}

changelog = changelog.replace(unreleased, nextUnreleased)
writeFileSync(changelogPath, changelog)