/**
 * 发布分支管理的纯 git 逻辑：切发布点、统计未发布提交、cherry-pick 修复到发布分支。
 * 不依赖 VS Code API；所有写操作只碰远端引用和临时 worktree，不改用户工作区。
 */
import { execFile } from 'node:child_process'
import { mkdtemp, rm } from 'node:fs/promises'
import * as os from 'node:os'
import * as path from 'node:path'

const DEFAULT_PREFIX = 'release/'

export interface ReleaseStatus {
  devBranch: string
  /** 当期发布分支全名（含前缀）；远端没有任何发布分支时为 undefined */
  current: string | undefined
  /** 未发布提交数；current 为 undefined 时为 0 */
  unreleased: number
  /** 结构性不可用（fetch 失败 / devBranch 远端不存在），带原因 */
  unavailable?: string
}

export interface UnreleasedCommit {
  sha: string
  subject: string
  author: string
  date: string
  body: string
  /** Gitea 查到的所属 PR；没有就不分组。 */
  pr?: number
  prTitle?: string
}

export interface ReleaseCommitGroup {
  pr?: number
  title: string
  authors: string[]
  commits: UnreleasedCommit[]
}

export class ReleaseError extends Error {
  constructor(message: string, public readonly detail?: string) {
    super(message)
    this.name = 'ReleaseError'
  }
}

interface Run { ok: boolean, stdout: string, stderr: string }

function runGit(cwd: string, args: string[], timeoutMs = 30_000): Promise<Run> {
  return new Promise((resolve) => {
    execFile('git', ['-C', cwd, ...args], { timeout: timeoutMs, encoding: 'utf8' }, (err, stdout, stderr) => {
      resolve({ ok: !err, stdout: stdout ?? '', stderr: stderr ?? '' })
    })
  })
}

const tail = (s: string, n = 400): string => s.trim().slice(-n)

async function mustGit(cwd: string, args: string[], failLabel: string): Promise<string> {
  const r = await runGit(cwd, args)
  if (!r.ok)
    throw new ReleaseError(`${failLabel}：${tail(r.stderr)}`, r.stderr)
  return r.stdout.trim()
}

export function normalizeReleasePrefix(raw: string): string {
  const t = raw.trim()
  if (!t)
    return DEFAULT_PREFIX
  return t.endsWith('/') ? t : `${t}/`
}

export function todayReleaseBranch(prefix: string, now = new Date()): string {
  const y = now.getFullYear()
  const m = String(now.getMonth() + 1).padStart(2, '0')
  const d = String(now.getDate()).padStart(2, '0')
  return `${prefix}${y}-${m}-${d}`
}

/** 发布分支名是 ISO 日期，字典序即时间序，不解析日期 */
export function pickCurrentRelease(prefix: string, remoteBranches: string[]): string | undefined {
  return remoteBranches.filter(b => b.startsWith(prefix)).sort().at(-1)
}

/** Gitea 默认合并说明：Merge pull request '标题' (#260) from … */
export function parseGiteaMergeSubject(subject: string): { number: number, title: string } | undefined {
  const m = /^Merge pull request '(.+)' \(#(\d+)\)/.exec(subject)
  if (!m)
    return undefined
  return { title: m[1], number: Number(m[2]) }
}

/** 同 PR 收一组（新→旧首次出现顺序）。pr 号来自合并记录，不是扫提交说明。 */
export function groupCommitsByPr(commits: UnreleasedCommit[]): ReleaseCommitGroup[] {
  const prGroups = new Map<number, ReleaseCommitGroup>()
  const prOrder: number[] = []
  const ungrouped: UnreleasedCommit[] = []
  for (const c of commits) {
    const pr = c.pr
    if (pr === undefined) {
      ungrouped.push(c)
      continue
    }
    let g = prGroups.get(pr)
    if (!g) {
      g = { pr, title: c.prTitle?.trim() || c.subject, authors: [], commits: [] }
      prGroups.set(pr, g)
      prOrder.push(pr)
    }
    g.commits.push(c)
    if (!g.authors.includes(c.author))
      g.authors.push(c.author)
  }
  const out = prOrder.map(n => prGroups.get(n)!)
  if (ungrouped.length > 0) {
    const authors: string[] = []
    for (const c of ungrouped) {
      if (!authors.includes(c.author))
        authors.push(c.author)
    }
    out.push({ title: '未关联 PR', authors, commits: ungrouped })
  }
  return out
}

async function remoteBranchNames(cwd: string, prefix: string): Promise<string[]> {
  const out = await mustGit(cwd, ['for-each-ref', '--format=%(refname:strip=3)', `refs/remotes/origin/${prefix}`], '读取远端发布分支失败')
  return out ? out.split('\n') : []
}

async function remoteRefExists(cwd: string, branch: string): Promise<boolean> {
  return (await runGit(cwd, ['show-ref', '--verify', '--quiet', `refs/remotes/origin/${branch}`])).ok
}

/** 左边是发布分支、右边是开发分支：只数右边独有、且补丁内容没被 cherry-pick 过去的提交 */
const unreleasedRange = (current: string, devBranch: string): string => `origin/${current}...origin/${devBranch}`

export async function getReleaseStatus(o: { cwd: string, devBranch: string, prefix: string }): Promise<ReleaseStatus> {
  const base = { devBranch: o.devBranch, current: undefined, unreleased: 0 }
  const fetched = await runGit(o.cwd, ['fetch', 'origin', '--prune'])
  if (!fetched.ok)
    return { ...base, unavailable: `拉取远端失败：${tail(fetched.stderr)}` }
  if (!await remoteRefExists(o.cwd, o.devBranch))
    return { ...base, unavailable: `远端没有 ${o.devBranch}` }
  const current = pickCurrentRelease(o.prefix, await remoteBranchNames(o.cwd, o.prefix))
  if (!current)
    return base
  const count = await mustGit(
    o.cwd,
    ['rev-list', '--count', '--right-only', '--cherry-pick', '--no-merges', unreleasedRange(current, o.devBranch)],
    '统计未发布提交失败',
  )
  return { devBranch: o.devBranch, current, unreleased: Number(count) }
}

/** 新→旧；不 fetch，调用方自己决定何时刷新远端 */
export async function listReleaseBranches(o: { cwd: string, prefix: string }): Promise<string[]> {
  const names = await remoteBranchNames(o.cwd, o.prefix)
  return names.filter(b => b.startsWith(o.prefix)).sort().reverse()
}

/** 用本地 merge 记录把未发布 sha 对上 PR。不打 Gitea。 */
export async function indexUnreleasedByMergePr(o: {
  cwd: string
  current: string
  devBranch: string
  shas: readonly string[]
}): Promise<Map<string, { number: number, title: string }>> {
  const needed = new Set(o.shas)
  const out = new Map<string, { number: number, title: string }>()
  if (needed.size === 0)
    return out
  const raw = await mustGit(
    o.cwd,
    ['log', '--right-only', '--cherry-pick', '--merges', '--format=%H%x00%s', unreleasedRange(o.current, o.devBranch)],
    '读取合并记录失败',
  )
  if (!raw)
    return out
  for (const line of raw.split('\n')) {
    const [sha, subject] = line.split('\0')
    if (!sha || !subject)
      continue
    const parsed = parseGiteaMergeSubject(subject)
    if (!parsed)
      continue
    const members = await mustGit(
      o.cwd,
      ['rev-list', '--no-merges', `${sha}^1..${sha}^2`],
      `读取 PR #${parsed.number} 提交失败`,
    )
    for (const member of members ? members.split('\n') : []) {
      if (needed.has(member))
        out.set(member, parsed)
    }
    if (out.size === needed.size)
      return out
  }
  return out
}

export function attachPulls<T extends { sha: string }>(
  commits: T[],
  index: Map<string, { number: number, title: string }>,
): Array<T & { pr?: number, prTitle?: string }> {
  return commits.map((c) => {
    const hit = index.get(c.sha)
    return hit ? { ...c, pr: hit.number, prTitle: hit.title } : c
  })
}

export async function listUnreleasedCommits(o: { cwd: string, devBranch: string, current: string }): Promise<UnreleasedCommit[]> {
  const out = await mustGit(
    o.cwd,
    ['log', '--right-only', '--cherry-pick', '--no-merges', '--format=%H%x00%s%x00%an%x00%as%x00%b%x1e', unreleasedRange(o.current, o.devBranch)],
    '读取未发布提交失败',
  )
  if (!out)
    return []
  return out.split('\x1e').flatMap((chunk) => {
    const trimmed = chunk.replace(/^\n+/, '').trimEnd()
    if (!trimmed)
      return []
    const [sha, subject, author, date, body = ''] = trimmed.split('\0')
    return [{ sha, subject, author, date, body: body.trim() }]
  })
}

/** 纯远端切分支；返回该分支相对上一个发布点的提交数（无上一个则为 0） */
export async function cutRelease(o: { cwd: string, devBranch: string, branch: string }): Promise<number> {
  await mustGit(o.cwd, ['fetch', 'origin', '--prune'], '拉取远端失败')
  if (await remoteRefExists(o.cwd, o.branch))
    throw new ReleaseError(`发布分支 ${o.branch} 已存在`)
  const prefix = o.branch.slice(0, o.branch.lastIndexOf('/') + 1)
  const prev = pickCurrentRelease(prefix, await remoteBranchNames(o.cwd, prefix))
  await mustGit(o.cwd, ['push', 'origin', `origin/${o.devBranch}:refs/heads/${o.branch}`], `推送 ${o.branch} 失败`)
  if (!prev)
    return 0
  const count = await mustGit(o.cwd, ['rev-list', '--count', `origin/${prev}..origin/${o.devBranch}`], '统计提交数失败')
  return Number(count)
}

/** 在临时 worktree 里按给定顺序（旧→新）cherry-pick，成功才推远端；无论成败都清理 worktree */
export async function cherryPickToRelease(o: { cwd: string, branch: string, shas: string[] }): Promise<void> {
  await mustGit(o.cwd, ['fetch', 'origin', '--prune'], '拉取远端失败')
  const tmp = await mkdtemp(path.join(os.tmpdir(), 'sw-release-'))
  try {
    await mustGit(o.cwd, ['worktree', 'add', '--detach', tmp, `origin/${o.branch}`], '创建临时 worktree 失败')
    for (const sha of o.shas) {
      const picked = await runGit(tmp, ['cherry-pick', '-x', sha])
      if (!picked.ok) {
        await runGit(tmp, ['cherry-pick', '--abort'])
        const subject = (await runGit(tmp, ['log', '-1', '--format=%s', sha])).stdout.trim()
        throw new ReleaseError(`${sha.slice(0, 7)} ${subject} 冲突，请手动处理`, picked.stderr)
      }
    }
    await mustGit(tmp, ['push', 'origin', `HEAD:refs/heads/${o.branch}`], `推送 ${o.branch} 失败`)
  }
  finally {
    await runGit(o.cwd, ['worktree', 'remove', '--force', tmp])
    await rm(tmp, { recursive: true, force: true })
    await runGit(o.cwd, ['worktree', 'prune'])
  }
}