/**
 * test/http/diff.test.ts (N-diff-be, B1) — read-only git diff parsing + getDiff.
 *
 * Two layers:
 *  1. Pure parsers (parseNumstat / parseUnifiedDiff) fed canned git output — the
 *     deterministic core (AC-B1.5: rename/new/delete/binary/empty/untracked, +/-
 *     consistent with `git diff --numstat`; never throws; <script> stays text).
 *  2. getDiff against a REAL throwaway git repo in os.tmpdir (AC-B1.1, L3).
 */

import { describe, it, expect, beforeAll, afterAll } from 'vitest'
import os from 'node:os'
import path from 'node:path'
import fs from 'node:fs/promises'
import { execFile } from 'node:child_process'
import { promisify } from 'node:util'
import {
  parseNumstat,
  parseUnifiedDiff,
  getDiff,
  type NumstatEntry,
  type GetDiffOptions,
} from '../../src/http/diff.js'

const execFileAsync = promisify(execFile)

const LIMITS: GetDiffOptions['cfg'] = {
  diffTimeoutMs: 5000,
  diffMaxBytes: 2 * 1024 * 1024,
  diffMaxFiles: 300,
}

// ── parseNumstat ──────────────────────────────────────────────────────────────

describe('parseNumstat', () => {
  it('parses a basic added/removed line', () => {
    const m = parseNumstat('2\t1\tfoo.txt\n')
    expect(m.get('foo.txt')).toEqual<NumstatEntry>({ added: 2, removed: 1, binary: false })
  })

  it('flags binary files (-\\t-) with zero counts', () => {
    const m = parseNumstat('-\t-\timg.png\n')
    expect(m.get('img.png')).toEqual<NumstatEntry>({ added: 0, removed: 0, binary: true })
  })

  it('keys a plain-arrow rename under both old and new paths', () => {
    const m = parseNumstat('1\t1\told.txt => new.txt\n')
    const entry = { added: 1, removed: 1, binary: false }
    expect(m.get('old.txt')).toEqual(entry)
    expect(m.get('new.txt')).toEqual(entry)
  })

  it('expands a braced rename path (common prefix/suffix)', () => {
    const m = parseNumstat('3\t4\tsrc/{a => b}/file.js\n')
    expect(m.has('src/a/file.js')).toBe(true)
    expect(m.has('src/b/file.js')).toBe(true)
    expect(m.get('src/b/file.js')).toEqual({ added: 3, removed: 4, binary: false })
  })

  it('collapses double slashes when a brace side is empty', () => {
    const m = parseNumstat('1\t0\tsrc/{ => sub}/file.txt\n')
    expect(m.has('src/file.txt')).toBe(true)
    expect(m.has('src/sub/file.txt')).toBe(true)
  })

  it('returns an empty map for empty input', () => {
    expect(parseNumstat('').size).toBe(0)
  })

  it('skips malformed lines without throwing', () => {
    const m = parseNumstat('garbage\n2\t1\tok.txt\n\n')
    expect(m.size).toBe(1)
    expect(m.get('ok.txt')).toEqual({ added: 2, removed: 1, binary: false })
  })
})

// ── parseUnifiedDiff ─────────────────────────────────────────────────────────

const MODIFIED = [
  'diff --git a/foo.txt b/foo.txt',
  'index e69de29..d95f3ad 100644',
  '--- a/foo.txt',
  '+++ b/foo.txt',
  '@@ -1,2 +1,3 @@',
  ' keep',
  '-old',
  '+new',
  '+added',
  '',
].join('\n')

describe('parseUnifiedDiff', () => {
  it('returns [] for empty / non-diff input', () => {
    expect(parseUnifiedDiff('')).toEqual([])
    expect(parseUnifiedDiff('not a diff at all')).toEqual([])
  })

  it('parses a modified file into one hunk with typed lines', () => {
    const [file] = parseUnifiedDiff(MODIFIED)
    expect(file).toBeDefined()
    expect(file?.oldPath).toBe('foo.txt')
    expect(file?.newPath).toBe('foo.txt')
    expect(file?.status).toBe('modified')
    expect(file?.binary).toBe(false)
    expect(file?.hunks).toHaveLength(1)
    expect(file?.hunks[0]?.header).toBe('@@ -1,2 +1,3 @@')
    expect(file?.hunks[0]?.lines).toEqual([
      { kind: 'context', text: 'keep' },
      { kind: 'removed', text: 'old' },
      { kind: 'added', text: 'new' },
      { kind: 'added', text: 'added' },
    ])
  })

  it('counts +/- from the hunk when no numstat is supplied', () => {
    const [file] = parseUnifiedDiff(MODIFIED)
    expect(file?.added).toBe(2)
    expect(file?.removed).toBe(1)
  })

  it('prefers numstat counts over hunk counts', () => {
    const numstat = parseNumstat('99\t88\tfoo.txt\n')
    const [file] = parseUnifiedDiff(MODIFIED, numstat)
    expect(file?.added).toBe(99)
    expect(file?.removed).toBe(88)
  })

  it('detects an added file via /dev/null source', () => {
    const patch = [
      'diff --git a/new.txt b/new.txt',
      'new file mode 100644',
      'index 0000000..1234567',
      '--- /dev/null',
      '+++ b/new.txt',
      '@@ -0,0 +1,2 @@',
      '+line one',
      '+line two',
      '',
    ].join('\n')
    const [file] = parseUnifiedDiff(patch)
    expect(file?.status).toBe('added')
    expect(file?.newPath).toBe('new.txt')
    expect(file?.added).toBe(2)
    expect(file?.removed).toBe(0)
  })

  it('detects a deleted file via /dev/null target', () => {
    const patch = [
      'diff --git a/del.txt b/del.txt',
      'deleted file mode 100644',
      'index 1234567..0000000',
      '--- a/del.txt',
      '+++ /dev/null',
      '@@ -1,2 +0,0 @@',
      '-line one',
      '-line two',
      '',
    ].join('\n')
    const [file] = parseUnifiedDiff(patch)
    expect(file?.status).toBe('deleted')
    expect(file?.oldPath).toBe('del.txt')
    expect(file?.removed).toBe(2)
  })

  it('detects a rename and maps numstat by the new path', () => {
    const patch = [
      'diff --git a/old/name.txt b/new/name.txt',
      'similarity index 95%',
      'rename from old/name.txt',
      'rename to new/name.txt',
      'index 111..222 100644',
      '--- a/old/name.txt',
      '+++ b/new/name.txt',
      '@@ -1 +1 @@',
      '-hello',
      '+hello world',
      '',
    ].join('\n')
    const numstat = parseNumstat('1\t1\t{old => new}/name.txt\n')
    const [file] = parseUnifiedDiff(patch, numstat)
    expect(file?.status).toBe('renamed')
    expect(file?.oldPath).toBe('old/name.txt')
    expect(file?.newPath).toBe('new/name.txt')
    expect(file?.added).toBe(1)
    expect(file?.removed).toBe(1)
  })

  it('detects a binary file (Binary files … differ + numstat -\\t-)', () => {
    const patch = [
      'diff --git a/img.png b/img.png',
      'index 111..222 100644',
      'Binary files a/img.png and b/img.png differ',
      '',
    ].join('\n')
    const numstat = parseNumstat('-\t-\timg.png\n')
    const [file] = parseUnifiedDiff(patch, numstat)
    expect(file?.status).toBe('binary')
    expect(file?.binary).toBe(true)
    expect(file?.hunks).toEqual([])
    expect(file?.added).toBe(0)
    expect(file?.removed).toBe(0)
  })

  it('parses multiple hunks and a no-newline meta marker', () => {
    const patch = [
      'diff --git a/m.txt b/m.txt',
      'index 111..222 100644',
      '--- a/m.txt',
      '+++ b/m.txt',
      '@@ -1,2 +1,2 @@',
      ' a',
      '-b',
      '+B',
      '@@ -10,2 +10,3 @@',
      ' x',
      '+y',
      '\\ No newline at end of file',
      '',
    ].join('\n')
    const [file] = parseUnifiedDiff(patch)
    expect(file?.hunks).toHaveLength(2)
    const meta = file?.hunks[1]?.lines.find((l) => l.kind === 'meta')
    expect(meta?.text).toContain('No newline')
  })

  it('classifies an unrecognised hunk line as context (never throws)', () => {
    const patch = [
      'diff --git a/x.txt b/x.txt',
      '--- a/x.txt',
      '+++ b/x.txt',
      '@@ -1 +1 @@',
      '?weird line',
      '',
    ].join('\n')
    const [file] = parseUnifiedDiff(patch)
    expect(file?.hunks[0]?.lines[0]).toEqual({ kind: 'context', text: '?weird line' })
  })

  it('preserves <script>/ANSI/backtick content verbatim as text (AC-B1.4)', () => {
    const payload = '<script>alert(1)</script> `cmd` red'
    const patch = [
      'diff --git a/x.txt b/x.txt',
      '--- a/x.txt',
      '+++ b/x.txt',
      '@@ -0,0 +1 @@',
      '+' + payload,
      '',
    ].join('\n')
    const [file] = parseUnifiedDiff(patch)
    expect(file?.hunks[0]?.lines[0]).toEqual({ kind: 'added', text: payload })
  })

  it('parses several files in one patch', () => {
    const patch = MODIFIED + [
      'diff --git a/bar.txt b/bar.txt',
      '--- a/bar.txt',
      '+++ b/bar.txt',
      '@@ -1 +1 @@',
      '-one',
      '+two',
      '',
    ].join('\n')
    const files = parseUnifiedDiff(patch)
    expect(files.map((f) => f.newPath)).toEqual(['foo.txt', 'bar.txt'])
  })
})

// ── getDiff (integration against a real git repo) ────────────────────────────

async function git(cwd: string, ...args: string[]): Promise<void> {
  await execFileAsync('git', args, { cwd })
}

describe('getDiff (real git repo)', () => {
  let repo: string

  beforeAll(async () => {
    repo = await fs.mkdtemp(path.join(os.tmpdir(), 'webterm-diff-'))
    await git(repo, 'init', '-q', '-b', 'main')
    await git(repo, 'config', 'user.email', 'test@example.com')
    await git(repo, 'config', 'user.name', 'Test')
    await git(repo, 'config', 'commit.gpgsign', 'false')
    await fs.writeFile(path.join(repo, 'tracked.txt'), 'one\ntwo\nthree\n')
    await git(repo, 'add', '.')
    await git(repo, 'commit', '-q', '-m', 'init')
  })

  afterAll(async () => {
    await fs.rm(repo, { recursive: true, force: true })
  })

  it('returns structured working-tree diff with numstat-consistent counts', async () => {
    await fs.writeFile(path.join(repo, 'tracked.txt'), 'one\nTWO\nthree\nfour\n')
    const result = await getDiff(repo, { staged: false, cfg: LIMITS })
    expect(result.staged).toBe(false)
    expect(result.truncated).toBe(false)
    const file = result.files.find((f) => f.newPath === 'tracked.txt')
    expect(file).toBeDefined()
    expect(file?.status).toBe('modified')
    // changed line two + added line four = 2 added, 1 removed
    expect(file?.added).toBe(2)
    expect(file?.removed).toBe(1)
    // revert for later tests
    await fs.writeFile(path.join(repo, 'tracked.txt'), 'one\ntwo\nthree\n')
  })

  it('lists untracked files via porcelain (L3, working tree only)', async () => {
    await fs.writeFile(path.join(repo, 'fresh.txt'), 'brand new\n')
    const result = await getDiff(repo, { staged: false, cfg: LIMITS })
    const untracked = result.files.find((f) => f.newPath === 'fresh.txt')
    expect(untracked?.status).toBe('untracked')
    await fs.rm(path.join(repo, 'fresh.txt'))
  })

  it('does not include untracked files in the staged diff', async () => {
    await fs.writeFile(path.join(repo, 'staged-only.txt'), 'queued\n')
    await git(repo, 'add', 'staged-only.txt')
    const result = await getDiff(repo, { staged: true, cfg: LIMITS })
    expect(result.staged).toBe(true)
    const file = result.files.find((f) => f.newPath === 'staged-only.txt')
    expect(file?.status).toBe('added')
    expect(result.files.every((f) => f.status !== 'untracked')).toBe(true)
    await git(repo, 'reset', '-q')
    await fs.rm(path.join(repo, 'staged-only.txt'))
  })

  it('marks truncated when the file count exceeds diffMaxFiles', async () => {
    for (let i = 0; i < 5; i++) {
      await fs.writeFile(path.join(repo, `gen-${i}.txt`), `content ${i}\n`)
    }
    const result = await getDiff(repo, {
      staged: false,
      cfg: { ...LIMITS, diffMaxFiles: 2 },
    })
    expect(result.truncated).toBe(true)
    expect(result.files.length).toBeLessThanOrEqual(2)
    for (let i = 0; i < 5; i++) await fs.rm(path.join(repo, `gen-${i}.txt`))
  })

  it('never throws for a non-existent / non-git path (returns empty)', async () => {
    const result = await getDiff(path.join(os.tmpdir(), 'definitely-not-here-xyz'), {
      staged: false,
      cfg: LIMITS,
    })
    expect(result.files).toEqual([])
    expect(result.truncated).toBe(false)
  })
})