import { execFileSync, spawnSync } from 'node:child_process'
import { existsSync, readFileSync } from 'node:fs'
import { createRequire } from 'node:module'
import path from 'node:path'
import process from 'node:process'
import { pathToFileURL } from 'node:url'
import { resolvePullRequestDiffBase } from './git-pull-request-diff-base.mjs'

const SOURCE_FILE_PATTERN = /\.(?:[cm]?[jt]sx?)$/
export const OXLINT_SCANS = [
  {
    // Why: no --config, so Oxlint keeps discovering nested configs. Pinning the root
    // config would apply root rules to mobile/, whose .oxlintrc.json turns them off.
    label: 'code quality',
    args: ['--report-unused-disable-directives-severity', 'warn']
  },
  {
    label: 'type-aware code quality',
    args: ['--type-aware', '--config', 'config/oxlint-code-quality-type-aware.json']
  },
  {
    label: 'React Doctor',
    args: ['--config', 'config/oxlint-react-doctor.json']
  }
]

export function parseAddedLineRanges(diff) {
  const ranges = []
  const hunkPattern = /^@@ -\d+(?:,\d+)? \+(\d+)(?:,(\d+))? @@/
  for (const line of diff.split(/\r?\n/)) {
    const match = hunkPattern.exec(line)
    if (!match) {
      continue
    }
    const start = Number.parseInt(match[1], 10)
    const count = match[2] === undefined ? 1 : Number.parseInt(match[2], 10)
    if (count > 0) {
      ranges.push({ start, end: start + count - 1 })
    }
  }
  return ranges
}

export function overlapsAddedLines(startLine, endLine, ranges) {
  return ranges.some((range) => startLine <= range.end && endLine >= range.start)
}

function runGit(root, args, options = {}) {
  return execFileSync('git', args, {
    cwd: root,
    encoding: options.encoding ?? 'utf8',
    maxBuffer: 64 * 1024 * 1024
  })
}

function splitNullDelimited(output) {
  return output.split('\0').filter(Boolean)
}

function resolveBase(root, requestedBase) {
  for (const candidate of [
    requestedBase,
    process.env.ORCA_CODE_QUALITY_BASE,
    'origin/main',
    'main'
  ]) {
    if (!candidate) {
      continue
    }
    const result = spawnSync('git', ['rev-parse', '--verify', `${candidate}^{commit}`], {
      cwd: root,
      stdio: 'ignore'
    })
    if (result.status === 0) {
      return candidate
    }
  }
  throw new Error('Pass the pull request base SHA or make origin/main available locally.')
}

export function collectAddedLineRanges(root, requestedBase) {
  const base = resolveBase(root, requestedBase)
  const mergeBase = runGit(root, ['merge-base', base, 'HEAD']).trim()
  const comparisonBase = resolvePullRequestDiffBase(root, mergeBase)
  const changedFiles = splitNullDelimited(
    runGit(root, ['diff', '--name-only', '-z', '--diff-filter=ACMRTUB', comparisonBase, '--'])
  )
  const untrackedFiles = splitNullDelimited(
    runGit(root, ['ls-files', '--others', '--exclude-standard', '-z'])
  )
  const rangesByFile = new Map()

  for (const file of changedFiles) {
    if (!SOURCE_FILE_PATTERN.test(file) || !existsSync(path.join(root, file))) {
      continue
    }
    const diff = runGit(root, ['diff', '--unified=0', '--no-color', comparisonBase, '--', file])
    const ranges = parseAddedLineRanges(diff)
    if (ranges.length > 0) {
      rangesByFile.set(file, ranges)
    }
  }

  for (const file of untrackedFiles) {
    const absolutePath = path.join(root, file)
    if (!SOURCE_FILE_PATTERN.test(file) || !existsSync(absolutePath)) {
      continue
    }
    const lineCount = readFileSync(absolutePath, 'utf8').split(/\r?\n/).length
    rangesByFile.set(file, [{ start: 1, end: lineCount }])
  }
  return { base, comparisonBase, rangesByFile }
}

function parseOxlintOutput(stdout, label) {
  const start = stdout.indexOf('{')
  const end = stdout.lastIndexOf('}')
  if (start !== -1 && end !== -1) {
    try {
      return JSON.parse(stdout.slice(start, end + 1))
    } catch {
      // Fall through so the caller sees what Oxlint actually printed.
    }
  }
  // Why echo it: Oxlint writes configuration failures to stdout, and a wrapper's own
  // warning can carry braces that this slice mistakes for the report, so discarding the
  // output leaves the gate dying with no reason anywhere in the log.
  throw new Error(
    `${label} did not return Oxlint JSON output. Oxlint printed:\n${stdout.trim().slice(0, 2000)}`
  )
}

function normalizedDiagnosticPath(root, filename) {
  const absolutePath = path.isAbsolute(filename) ? filename : path.join(root, filename)
  return path.relative(root, absolutePath).split(path.sep).join('/')
}

function diagnosticLineRange(root, filename, span) {
  const startLine = span.line
  if (!Number.isInteger(startLine)) {
    return null
  }
  if (!Number.isInteger(span.offset) || !Number.isInteger(span.length) || span.length === 0) {
    return { start: startLine, end: startLine }
  }
  const absolutePath = path.isAbsolute(filename) ? filename : path.join(root, filename)
  const source = readFileSync(absolutePath)
  const highlighted = source.subarray(span.offset, span.offset + span.length).toString('utf8')
  return { start: startLine, end: startLine + (highlighted.match(/\n/g)?.length ?? 0) }
}

// Why: a file-splitting refactor makes every line of the new module an "added"
// line, so pre-existing lint debt in code that merely MOVED starts failing the
// changed-lines gate. The only way to satisfy it is to edit the moved code,
// which is exactly what a behavior-preserving refactor must not do. So a
// diagnostic is exempt when its highlighted lines already existed, verbatim and
// contiguous, somewhere in the base revision of the files this change touches.
function normalizeSourceLine(line) {
  return line.replace(/\s+/g, ' ').trim()
}

export function collectBaseLineBlocks(root, comparisonBase, files = null) {
  // Why: in a split, the moved code's base text lives in the ORIGINAL file, which is
  // often deleted or renamed away. Deleted paths never reach the changed-file list
  // (it filters to ACMRTUB), so read every path the diff touches, deletions included.
  const paths =
    files ??
    splitNullDelimited(runGit(root, ['diff', '--name-only', '-z', comparisonBase, '--'])).filter(
      (file) => SOURCE_FILE_PATTERN.test(file)
    )
  const blocks = []
  for (const file of paths) {
    const result = spawnSync('git', ['show', `${comparisonBase}:${file}`], {
      cwd: root,
      encoding: 'utf8',
      maxBuffer: 64 * 1024 * 1024
    })
    if (result.status !== 0 || typeof result.stdout !== 'string') {
      continue
    }
    blocks.push(
      result.stdout
        .split(/\r?\n/)
        .map(normalizeSourceLine)
        .filter((line) => line !== '')
    )
  }
  return blocks
}

export function isMovedCode(highlightedLines, baseBlocks) {
  const needle = highlightedLines.map(normalizeSourceLine).filter((line) => line !== '')
  if (needle.length === 0) {
    return false
  }
  // Why a near-match rather than an exact contiguous one: a split moves a block
  // verbatim but a diagnostic's span often reaches past it — most commonly to a
  // hook dependency array, which legitimately grows when closure variables become
  // props. Requiring every line to match would report the moved body as new. So:
  // the block must still start at the same line in the base and appear IN ORDER,
  // and nearly all of it must be present. Genuinely new code shares neither the
  // anchor nor the ordering, so it stays reported.
  const MIN_COVERAGE = 0.9
  return baseBlocks.some((rawHaystack) => {
    const haystack = rawHaystack.map(normalizeSourceLine).filter((line) => line !== '')
    for (let start = 0; start < haystack.length; start += 1) {
      if (haystack[start] !== needle[0]) {
        continue
      }
      let matched = 1
      let cursor = start + 1
      for (let index = 1; index < needle.length && cursor < haystack.length; index += 1) {
        while (cursor < haystack.length && haystack[cursor] !== needle[index]) {
          cursor += 1
        }
        if (cursor < haystack.length) {
          matched += 1
          cursor += 1
        }
      }
      if (matched / needle.length >= MIN_COVERAGE) {
        return true
      }
    }
    return false
  })
}

function diagnosticHighlightedLines(root, filename, span) {
  const absolutePath = path.isAbsolute(filename) ? filename : path.join(root, filename)
  const source = readFileSync(absolutePath, 'utf8').split(/\r?\n/)
  const range = diagnosticLineRange(root, filename, span)
  if (range === null) {
    return []
  }
  return source.slice(range.start - 1, range.end)
}

export function diagnosticTouchesAddedLines(
  diagnostic,
  rangesByFile,
  root = process.cwd(),
  baseBlocks = []
) {
  const file = normalizedDiagnosticPath(root, diagnostic.filename)
  const ranges = rangesByFile.get(file)
  if (!ranges) {
    return false
  }
  return (diagnostic.labels ?? []).some((label) => {
    const lineRange = diagnosticLineRange(root, diagnostic.filename, label.span)
    if (lineRange === null || !overlapsAddedLines(lineRange.start, lineRange.end, ranges)) {
      return false
    }
    return !isMovedCode(
      diagnosticHighlightedLines(root, diagnostic.filename, label.span),
      baseBlocks
    )
  })
}

function annotationValue(value) {
  return String(value).replaceAll('%', '%25').replaceAll('\r', '%0D').replaceAll('\n', '%0A')
}

function printDiagnostic(diagnostic, root) {
  const file = normalizedDiagnosticPath(root, diagnostic.filename)
  const line = diagnostic.labels?.[0]?.span?.line ?? 1
  const code = diagnostic.code ?? 'oxlint'
  console.error(
    `::error file=${annotationValue(file)},line=${line},title=${annotationValue(code)}::${annotationValue(diagnostic.message)}`
  )
  console.error(`${file}:${line} ${code}: ${diagnostic.message}`)
}

// Why: Oxlint takes paths as positional arguments only — no stdin, no @file — so one
// oversized changed set makes the spawn itself fail with E2BIG and the gate never runs.
// The file list is only part of what the spawn carries, so budget against the whole of it.
//
// POSIX execve() charges argv strings, the inherited environment, AND one pointer per
// entry against a single ceiling: macOS caps that at kern.argmax (1 MiB), Linux at
// max(min(6 MiB, RLIMIT_STACK/4), 128 KiB) — 2 MiB at the default 8 MiB stack.
//
// Budgeting just under the kernel's own ceiling is not enough. macOS copies argv and the
// environment into the child's stack, and a Node child dies from the squeeze well before
// the kernel refuses the exec: measured here, a total near 970 KiB SIGSEGVs on Node 24 and
// throws a stack-overflow RangeError on Node 26, while E2BIG only starts around 1,048 KiB.
// Half of kern.argmax leaves that cliff ~450 KiB away.
//
// Windows is a different shape entirely: CreateProcess caps only the command line, at
// 32,767 UTF-16 units, and passes the environment in a separate block that does not count.
// Counting UTF-8 bytes against a UTF-16 ceiling over-estimates, which is the safe direction.
const POSIX_SPAWN_CEILING_BYTES = 512 * 1024
const WINDOWS_COMMAND_LINE_CEILING_BYTES = 32767
// Every entry costs a pointer beside its bytes, and libuv may wrap a Windows argument in
// quotes. Measured on macOS: 6,096 paths cost ~48 KiB in pointers alone.
const PER_ENTRY_OVERHEAD_BYTES = 12
// Slack for kernel padding and the exec path the kernel copies alongside argv.
const SPAWN_HEADROOM_BYTES = 8 * 1024
// A full ceiling's worth of paths would be a single enormous batch; hold the file list to
// what the gate already used so an ordinary changed set still spawns once per scan.
const MAX_BATCH_ARGUMENT_BYTES = 256 * 1024
// A pathological environment must not drive the budget to zero, which would spawn Oxlint
// once per path.
const MIN_BATCH_ARGUMENT_BYTES = 8 * 1024

function spawnEntryBytes(entries) {
  let total = 0
  for (const entry of entries) {
    total += Buffer.byteLength(entry, 'utf8') + PER_ENTRY_OVERHEAD_BYTES
  }
  return total
}

export function environmentEntries(env = process.env) {
  const entries = []
  for (const [key, value] of Object.entries(env)) {
    if (value !== undefined) {
      entries.push(`${key}=${value}`)
    }
  }
  return entries
}

export function maxBatchArgumentBytes({
  platform = process.platform,
  fixedArguments = [],
  env = process.env
} = {}) {
  const windows = platform === 'win32'
  const ceiling = windows ? WINDOWS_COMMAND_LINE_CEILING_BYTES : POSIX_SPAWN_CEILING_BYTES
  const carried =
    spawnEntryBytes(fixedArguments) + (windows ? 0 : spawnEntryBytes(environmentEntries(env)))
  return Math.min(
    MAX_BATCH_ARGUMENT_BYTES,
    Math.max(MIN_BATCH_ARGUMENT_BYTES, ceiling - SPAWN_HEADROOM_BYTES - carried)
  )
}

export function batchFilesByArgumentBytes(files, limit = maxBatchArgumentBytes()) {
  const batches = []
  let batch = []
  let bytes = 0
  for (const file of files) {
    // A single path over the limit still gets its own batch: an empty argument list
    // would make Oxlint lint the whole working directory instead.
    const cost = Buffer.byteLength(file, 'utf8') + PER_ENTRY_OVERHEAD_BYTES
    if (batch.length > 0 && bytes + cost > limit) {
      batches.push(batch)
      batch = []
      bytes = 0
    }
    batch.push(file)
    bytes += cost
  }
  if (batch.length > 0) {
    batches.push(batch)
  }
  return batches
}

// Why resolve the manifest rather than joining node_modules: pnpm's store is not a flat
// tree, and `bin` is the launcher the package itself declares. Not `pnpm exec`, which on
// Windows routes through pnpm.cmd and cmd.exe, whose command line caps at 8,191 characters
// instead of CreateProcess' 32,767.
let cachedOxlintCliPath = null
function oxlintCliPath() {
  if (cachedOxlintCliPath === null) {
    const manifestPath = createRequire(import.meta.url).resolve('oxlint/package.json')
    const manifest = JSON.parse(readFileSync(manifestPath, 'utf8'))
    cachedOxlintCliPath = path.join(path.dirname(manifestPath), manifest.bin.oxlint)
  }
  return cachedOxlintCliPath
}

function oxlintCommand(scan) {
  return {
    command: process.execPath,
    fixedArguments: [oxlintCliPath(), ...scan.args, '--format', 'json']
  }
}

function spawnOxlintBatch(root, scan, batch) {
  const { command, fixedArguments } = oxlintCommand(scan)
  const result = spawnSync(command, [...fixedArguments, ...batch], {
    cwd: root,
    encoding: 'utf8',
    maxBuffer: 128 * 1024 * 1024
  })
  if (result.error) {
    // Why restate it: a bare spawn error reads as a crash in the gate rather than a
    // failure to launch Oxlint over this batch.
    throw new Error(
      `${scan.label} could not run Oxlint over ${batch.length} file(s): ${result.error.message}`,
      { cause: result.error }
    )
  }
  if (!result.stdout.trim()) {
    process.stderr.write(result.stderr)
    throw new Error(`${scan.label} failed before producing diagnostics.`)
  }
  return result.stdout
}

export function runOxlintScan(root, scan, files, spawnBatch = spawnOxlintBatch) {
  const { command, fixedArguments } = oxlintCommand(scan)
  const limit = maxBatchArgumentBytes({ fixedArguments: [command, ...fixedArguments] })
  const diagnostics = []
  for (const batch of batchFilesByArgumentBytes(files, limit)) {
    diagnostics.push(
      ...(parseOxlintOutput(spawnBatch(root, scan, batch), scan.label).diagnostics ?? [])
    )
  }
  return diagnostics
}

export function main(
  root = process.cwd(),
  requestedBase = process.argv.slice(2).find((argument) => argument !== '--')
) {
  const { base, comparisonBase, rangesByFile } = collectAddedLineRanges(root, requestedBase)
  const files = [...rangesByFile.keys()]
  if (files.length === 0) {
    console.log(`Changed-code quality gate: no changed JavaScript or TypeScript since ${base}.`)
    return 0
  }

  const baseBlocks = collectBaseLineBlocks(root, comparisonBase)

  let failures = 0
  for (const scan of OXLINT_SCANS) {
    const diagnostics = runOxlintScan(root, scan, files).filter((diagnostic) =>
      diagnosticTouchesAddedLines(diagnostic, rangesByFile, root, baseBlocks)
    )
    for (const diagnostic of diagnostics) {
      printDiagnostic(diagnostic, root)
    }
    failures += diagnostics.length
    console.log(
      `${scan.label}: ${diagnostics.length} new finding(s) across ${files.length} changed file(s).`
    )
  }

  if (failures > 0) {
    console.error(
      `Changed-code quality gate failed with ${failures} finding(s) since ${comparisonBase.slice(0, 12)}.`
    )
    return 1
  }
  console.log(`Changed-code quality gate passed since ${comparisonBase.slice(0, 12)}.`)
  return 0
}

if (process.argv[1] && import.meta.url === pathToFileURL(process.argv[1]).href) {
  process.exit(main())
}