const semver = require('semver')
const octokit = require('@octokit/rest')()
const changelog = require('pr-changelog')
const childProcess = require('child_process')

module.exports.getRelease = async function (releaseVersion, githubToken) {
  if (githubToken) {
    octokit.authenticate({
      type: 'oauth',
      token: githubToken
    })
  }

  const releases = await octokit.repos.getReleases({owner: 'atom', repo: 'atom'})
  const release = releases.data.find(r => semver.eq(r.name, releaseVersion))

  return {
    exists: release !== undefined,
    isDraft: release && release.draft,
    releaseNotes: release ? release.body : undefined
  }
}

module.exports.generateForVersion = async function (releaseVersion, githubToken, oldReleaseNotes) {
  let oldVersion = null
  let oldVersionName = null
  const parsedVersion = semver.parse(releaseVersion)
  const newVersionBranch = getBranchForVersion(parsedVersion)

  if (githubToken) {
    changelog.setGithubAccessToken(githubToken)
    octokit.authenticate({
      type: 'oauth',
      token: githubToken
    })
  }

  if (parsedVersion.prerelease && parsedVersion.prerelease[0] === 'beta0') {
    // For beta0 releases, stable hasn't been released yet so compare against
    // the stable version's release branch
    oldVersion = `${parsedVersion.major}.${parsedVersion.minor - 1}-releases`
    oldVersionName = `v${parsedVersion.major}.${parsedVersion.minor - 1}.0`
  } else {
    let releases = await octokit.repos.getReleases({owner: 'atom', repo: 'atom'})
    oldVersion = 'v' + getPreviousRelease(releaseVersion, releases.data).name
    oldVersionName = oldVersion
  }

  const allChangesText = await changelog.getChangelog({
    owner: 'atom',
    repo: 'atom',
    fromTag: oldVersion,
    toTag: newVersionBranch,
    dependencyKey: 'packageDependencies',
    changelogFormatter: function ({pullRequests, owner, repo, fromTag, toTag}) {
      let prString = changelog.pullRequestsToString(pullRequests)
      let title = repo
      if (repo === 'atom') {
        title = 'Atom Core'
        fromTag = oldVersionName
        toTag = releaseVersion
      }
      return `### [${title}](https://github.com/${owner}/${repo})\n\n${fromTag}...${toTag}\n\n${prString}`
    }
  })

  const writtenReleaseNotes =
    extractWrittenReleaseNotes(oldReleaseNotes) ||
    '**TODO**: Pull relevant changes here!'

  return `## Notable Changes\n
${writtenReleaseNotes}\n
<details>
<summary>All Changes</summary>\n
${allChangesText}
</details>
`
}

module.exports.generateForNightly = async function (releaseVersion, githubToken) {
  const releases = await octokit.repos.getReleases({owner: 'atom', repo: 'atom-nightly-releases'})
  const previousRelease = getPreviousRelease(releaseVersion, releases.data)
  const oldReleaseNotes = previousRelease ? previousRelease.body : undefined

  const latestCommitResult = childProcess.spawnSync('git', ['rev-parse', '--short', 'HEAD'])

  if (latestCommitResult && oldReleaseNotes) {
    const latestCommit = latestCommitResult.stdout.toString().trim()
    const extractMatch = oldReleaseNotes.match(/atom\/atom\/compare\/([0-9a-f]{5,40})\.\.\.([0-9a-f]{5,40})/)
    if (extractMatch) {
      return `### Click [here](https://github.com/atom/atom/compare/${extractMatch[2]}...${latestCommit}) to see the changes included with this release! :atom: :night_with_stars:`
    }
  }

  return undefined
}

function extractWrittenReleaseNotes (oldReleaseNotes) {
  if (oldReleaseNotes) {
    const extractMatch = oldReleaseNotes.match(/^## Notable Changes\r\n([\s\S]*)<details>/)
    if (extractMatch && extractMatch[1]) {
      return extractMatch[1].trim()
    }
  }

  return undefined
}

function getPreviousRelease (version, allReleases) {
  const versionIsStable = semver.prerelease(version) === null

  // Make sure versions are sorted before using them
  allReleases.sort((v1, v2) => semver.rcompare(v1.name, v2.name))

  for (let release of allReleases) {
    if (versionIsStable && semver.prerelease(release.name)) {
      continue
    }

    if (semver.lt(release.name, version)) {
      return release
    }
  }

  return null
}

function getBranchForVersion (version) {
  let parsedVersion = version
  if (!(version instanceof semver.SemVer)) {
    parsedVersion = semver.parse(version)
  }

  return `${parsedVersion.major}.${parsedVersion.minor}-releases`
}