import fs from 'fs'
import fsp from 'fs/promises'
import path from 'path'

const UPDATE_LOG = 'Changelog.md'

// parse the Changelog.md
export async function resolveUpdateLog(tag) {
  const cwd = process.cwd()

  const reTitle = /^## v[\d.]+/
  const reEnd = /^---/

  const file = path.join(cwd, UPDATE_LOG)

  if (!fs.existsSync(file)) {
    throw new Error('could not found Changelog.md')
  }

  const data = await fsp.readFile(file, 'utf-8')

  const map = {}
  let p = ''

  data.split('\n').forEach((line) => {
    if (reTitle.test(line)) {
      p = line.slice(3).trim()
      if (!map[p]) {
        map[p] = []
      } else {
        throw new Error(`Tag ${p} dup`)
      }
    } else if (reEnd.test(line)) {
      p = ''
    } else if (p) {
      map[p].push(line)
    }
  })

  if (!map[tag]) {
    throw new Error(`could not found "${tag}" in Changelog.md`)
  }

  return map[tag].join('\n').trim()
}

export async function resolveUpdateLogDefault() {
  const cwd = process.cwd()
  const file = path.join(cwd, UPDATE_LOG)

  if (!fs.existsSync(file)) {
    throw new Error('could not found Changelog.md')
  }

  const data = await fsp.readFile(file, 'utf-8')

  const reTitle = /^## v[\d.]+/
  const reEnd = /^---/

  let isCapturing = false
  const content = []
  let firstTag = ''

  for (const line of data.split('\n')) {
    if (reTitle.test(line) && !isCapturing) {
      isCapturing = true
      firstTag = line.slice(3).trim()
      continue
    }

    if (isCapturing) {
      if (reEnd.test(line)) {
        break
      }
      content.push(line)
    }
  }

  if (!firstTag) {
    throw new Error('could not found any version tag in Changelog.md')
  }

  return content.join('\n').trim()
}