var fs = require('fs')
var child_process = require('child_process')

var pkg = JSON.parse(fs.readFileSync('package.json', 'utf8'))
var v = JSON.parse(fs.readFileSync('version.json', 'utf8'))

var name = pkg.name
var oldVersions = pkg.meta.oldVersions
var version = v.version
var date = v.date

var branch = version.replace(/\.\d+$/, '')
var headerLevel = branch.replace(/(\.0)*$/, '').split('.').length
var headerPrefix = new Array(headerLevel + 1).join('#')
var separator = `${headerPrefix} v${branch}`

var today = date.split('T')[0]
var filename = `/builds/${name}-noupdate`
var ffLink = `${oldVersions}${version}${filename}.user.js`
var crLink = `${oldVersions}${version}${filename}.crx`
var line = `**v${version}** *(${today})* - [[Userscript](${ffLink})] [[Chrome extension](${crLink})]`

var changelog = fs.readFileSync('CHANGELOG.md', 'utf8')

var breakPos = changelog.indexOf(separator)
if (breakPos >= 0) {
  breakPos += separator.length
} else {
  breakPos = Math.max(changelog.indexOf('\n\n#'), 0)
  line = `${separator}\n\n${line}`
}

var prevVersion = changelog.substr(breakPos).match(/\*\*v([\d\.]+)\*\*/)[1]
if (prevVersion.replace(/\.\d+$/, '') !== branch) {
  line += `\n- Based on v${prevVersion}.`
}
line +=
  '\n- ' +
  child_process
    .execSync(`git log --pretty=format:%s ${prevVersion}..HEAD`)
    .toString()
    .replace(/\n/g, '\n- ')

fs.writeFileSync(
  'CHANGELOG.md',
  `${changelog.substr(0, breakPos)}\n\n${line}${changelog.substr(breakPos)}`,
  'utf8'
)
console.log(`Changelog updated for v${version}.`)