/**
 * Status and conflict-detection operations extracted from git-handler.ts.
 * Why: split to satisfy oxlint max-lines (300); pure data ops on git state, no class coupling.
 */
import * as path from 'node:path'
import { existsSync } from 'node:fs'
import { readFile } from 'node:fs/promises'
import { parseUnmergedEntry } from './git-handler-utils'
import type { GitExec } from './git-handler-ops'
import type { RelayGitStreamExec } from './git-stdout-stream'
import type { GitUpstreamStatus } from '../shared/git-status-types'
import { StatusPorcelainParser } from '../shared/git-status-porcelain-parser'
import { splitRemoteBranchName } from '../shared/git-effective-upstream'
import { collectGitStatusLineStatInputs } from '../shared/git-status-line-stat-inputs'
import { readOrProbeNoEffectiveUpstreamStatus } from './git-status-upstream-negative-cache'
import {
  applyLineStats,
  collectUntrackedAdditions,
  parseNumstat,
  type GitLineStats
} from '../shared/git-uncommitted-line-stats'
import { resolveGitStatusLimit } from '../shared/git-status-limit'
import {
  beginGitStatusLineStatsCacheWrite,
  clearGitStatusLineStatsCacheKey,
  reuseOrRecomputeGitStatusLineStats
} from '../shared/git-status-line-stats-cache'
import {
  readGitBranchLineTotalMergeBaseParam,
  type GitBranchLineTotal
} from '../shared/git-branch-line-total'
import { buildBranchLineTotalInput } from './git-status-branch-line-total'

export async function resolveGitDir(worktreePath: string): Promise<string> {
  const dotGitPath = path.join(worktreePath, '.git')
  try {
    const contents = await readFile(dotGitPath, 'utf-8')
    const match = contents.match(/^gitdir:\s*(.+)\s*$/m)
    if (match) {
      return path.resolve(worktreePath, match[1])
    }
  } catch {
    // .git is a directory, not a file
  }
  return dotGitPath
}

export async function detectConflictOperation(worktreePath: string): Promise<string> {
  const gitDir = await resolveGitDir(worktreePath)
  try {
    if (existsSync(path.join(gitDir, 'MERGE_HEAD'))) {
      return 'merge'
    }
    if (
      existsSync(path.join(gitDir, 'rebase-merge')) ||
      existsSync(path.join(gitDir, 'rebase-apply'))
    ) {
      return 'rebase'
    }
    if (existsSync(path.join(gitDir, 'CHERRY_PICK_HEAD'))) {
      return 'cherry-pick'
    }
  } catch {
    // fs error — treat as no conflict operation
  }
  return 'unknown'
}

export async function getStatusOp(
  git: GitExec,
  streamGit: RelayGitStreamExec,
  params: Record<string, unknown>,
  options: { signal?: AbortSignal } = {}
): Promise<{
  entries: Record<string, unknown>[]
  conflictOperation: string
  head?: string
  branch?: string
  upstreamStatus?: GitUpstreamStatus
  ignoredPaths?: string[]
  didHitLimit?: boolean
  statusLength?: number
  branchLineTotal?: GitBranchLineTotal
}> {
  const worktreePath = params.worktreePath as string
  const lineStatsCacheKey = `relay\0${worktreePath}`
  const lineStatsWriteToken =
    params.includeLineStats === false ? null : beginGitStatusLineStatsCacheWrite(lineStatsCacheKey)
  const includeIgnored = params.includeIgnored === true
  // Why: untrusted RPC input spliced into a git argv — only an OID shape may pass.
  const branchLineTotalMergeBase = readGitBranchLineTotalMergeBaseParam(
    params.branchLineTotalMergeBase
  )
  // Why: reject NaN/negative limits — NaN would silently disable capping, negatives would over-truncate.
  const limit = resolveGitStatusLimit(params.limit)
  const conflictPromise = detectConflictOperation(worktreePath)
  // Why: core.quotePath=false keeps non-ASCII filenames as raw UTF-8 instead of octal escapes that render as gibberish.
  const statusArgs = [
    '-c',
    'core.quotePath=false',
    'status',
    '--porcelain=v2',
    '--branch',
    '--untracked-files=all'
  ]
  if (includeIgnored) {
    statusArgs.push('--ignored=matching')
  }
  // Why: attach rejection ownership before awaiting marker I/O, so a fast Git failure cannot become unhandled.
  const statusSettlementPromise = Promise.allSettled([
    (async () => {
      const parser = new StatusPorcelainParser()
      const result = await streamGit(statusArgs, worktreePath, {
        // Why: status polling is read-like; avoid racing terminal Git on .git/worktrees/*/index.lock.
        disableOptionalLocks: true,
        signal: options.signal,
        onStdout: (chunk) => parser.update(chunk, limit)
      })
      if (!result.stoppedEarly) {
        parser.finish()
      }
      return { parser, stoppedEarly: result.stoppedEarly }
    })()
  ])
  const conflictOperation = await conflictPromise
  const entries: Record<string, unknown>[] = []
  let head: string | undefined
  let branch: string | undefined
  let upstreamStatus: GitUpstreamStatus | undefined
  let ignoredPaths: string[] = []
  let didHitLimit = false
  let statusLength = 0
  let statusSucceeded = false
  let branchLineTotal: GitBranchLineTotal | undefined

  try {
    const [statusResult] = await statusSettlementPromise
    if (statusResult.status === 'rejected') {
      throw statusResult.reason
    }
    const { parser, stoppedEarly } = statusResult.value
    head = parser.branch.head
    branch = parser.branch.branch
    ignoredPaths = parser.ignoredPaths
    statusLength = parser.statusLength
    didHitLimit = stoppedEarly
    statusSucceeded = true
    const { upstreamName, upstreamAheadBehind } = parser.branch
    upstreamStatus = upstreamName
      ? {
          hasUpstream: true,
          upstreamName,
          ahead: upstreamAheadBehind?.ahead ?? 0,
          behind: upstreamAheadBehind?.behind ?? 0
        }
      : { hasUpstream: false, ahead: 0, behind: 0 }

    if (!didHitLimit) {
      if (shouldProbeEffectiveUpstreamStatus(branch, upstreamStatus?.upstreamName)) {
        const branchName = getShortBranchName(branch)
        if (branchName) {
          try {
            // Why: one request's abort must not reject this shared status probe.
            upstreamStatus = await readOrProbeNoEffectiveUpstreamStatus(
              { worktreePath, branchName, upstreamName: upstreamStatus?.upstreamName },
              (args) => git(args, worktreePath),
              {
                bypassCache: params.bypassEffectiveUpstreamNegativeCache === true
              }
            )
          } catch {
            // Why: keep returning working-tree entries even if the upstream probe hits a transient SSH/git ref error.
          }
        }
      }
    }

    // Why: resolve deferred conflicts in Git's output order so the cap cannot hide
    // an early conflict behind ordinary rows that appeared later in the stream.
    for (const record of parser.statusRecords) {
      if (didHitLimit && entries.length >= limit) {
        break
      }
      if (record.type === 'entry') {
        entries.push(record.entry as Record<string, unknown>)
      } else {
        const entry = parseUnmergedEntry(worktreePath, record.line)
        if (entry) {
          entries.push(entry)
        }
      }
    }
  } catch (error) {
    // Why: an aborted scan must reject, not resolve as a completed (empty) status result.
    if (options.signal?.aborted) {
      throw error
    }
    // not a git repo or git not available
  }

  // Why: skip numstat after the limit to avoid reintroducing its cost.
  if (!didHitLimit && lineStatsWriteToken !== null) {
    const branchLineTotalInput = buildBranchLineTotalInput(
      git,
      worktreePath,
      entries,
      // Why: a failed scan leaves the untracked list untrustworthy, so the total
      // would under-count — omit it rather than publish a confident wrong number.
      statusSucceeded ? branchLineTotalMergeBase : undefined,
      options.signal
    )
    // Why: passed in so the ranged diff runs alongside the per-area numstats, not after them.
    ;({ branchLineTotal } = await reuseOrRecomputeGitStatusLineStats({
      cacheKey: lineStatsCacheKey,
      head,
      entries,
      writeToken: lineStatsWriteToken,
      reuse: params.reuseLineStats === true,
      isAborted: () => options.signal?.aborted === true,
      recompute: () => attachLineStats(git, worktreePath, entries, options.signal),
      ...(branchLineTotalInput ? { branchLineTotal: branchLineTotalInput } : {})
    }))
  } else if (lineStatsWriteToken !== null) {
    clearGitStatusLineStatsCacheKey(lineStatsCacheKey, lineStatsWriteToken)
  }

  // Why: a late abort (during unmerged/upstream/line-stats work) must still reject, not resolve as completed.
  if (options.signal?.aborted) {
    const error = new Error('The operation was aborted.')
    error.name = 'AbortError'
    throw error
  }

  return {
    entries,
    conflictOperation,
    head,
    branch,
    upstreamStatus,
    ...(includeIgnored ? { ignoredPaths } : {}),
    ...(didHitLimit ? { didHitLimit: true, statusLength } : {}),
    ...(branchLineTotal ? { branchLineTotal } : {})
  }
}

async function runNumstat(
  git: GitExec,
  worktreePath: string,
  cached: boolean,
  signal?: AbortSignal
): Promise<Map<string, GitLineStats> | null> {
  try {
    const { stdout } = await git(
      ['-c', 'core.quotePath=false', 'diff', ...(cached ? ['--cached'] : []), '--numstat', '-M'],
      worktreePath,
      { disableOptionalLocks: true, signal }
    )
    return parseNumstat(stdout)
  } catch (error) {
    // Why: an aborted pass must reject so a cancelled scan is never treated as completed.
    if (signal?.aborted) {
      throw error
    }
    // Why: null (vs an empty map) tells the caller the pass is incomplete and must not be cached.
    return null
  }
}

/** Returns false when a numstat pass failed, so callers skip caching it. */
async function attachLineStats(
  git: GitExec,
  worktreePath: string,
  entries: Record<string, unknown>[],
  signal?: AbortSignal
): Promise<boolean> {
  if (entries.length === 0) {
    return true
  }
  const { hasStaged, hasUnstaged, untrackedPaths } = collectGitStatusLineStatInputs(entries)
  const emptyStats = new Map<string, GitLineStats>()
  const [stagedStats, unstagedStats, untrackedStats] = await Promise.all([
    hasStaged ? runNumstat(git, worktreePath, true, signal) : Promise.resolve(emptyStats),
    hasUnstaged ? runNumstat(git, worktreePath, false, signal) : Promise.resolve(emptyStats),
    collectUntrackedAdditions(worktreePath, untrackedPaths, signal)
  ])
  for (const entry of entries) {
    const filePath = entry.path as string
    const area = entry.area
    applyLineStats(
      entry as { added?: number; removed?: number },
      area === 'staged'
        ? (stagedStats ?? emptyStats).get(filePath)
        : area === 'unstaged'
          ? (unstagedStats ?? emptyStats).get(filePath)
          : untrackedStats.get(filePath)
    )
  }
  return stagedStats !== null && unstagedStats !== null
}

function getShortBranchName(branch: string | undefined): string | null {
  const prefix = 'refs/heads/'
  return branch?.startsWith(prefix) ? branch.slice(prefix.length) : null
}

function shouldProbeEffectiveUpstreamStatus(
  branch: string | undefined,
  upstreamName: string | undefined
): boolean {
  const branchName = getShortBranchName(branch)
  if (!branchName) {
    return false
  }
  if (!upstreamName) {
    return true
  }
  const parsed = splitRemoteBranchName(upstreamName)
  return parsed?.remoteName === 'origin' && parsed.branchName !== branchName
}