/**
 * Pure yt-dlp argv construction for a download.
 *
 * This module is deliberately free of any electron / node-runtime dependency
 * (it only imports types + the BEST_FORMAT_ID const from the shared contract)
 * so the argv it produces can be unit-tested without spinning up Electron.
 * `buildArgs` takes the ffmpeg/yt-dlp `binDir` as a parameter rather than
 * resolving it itself; the caller in download.ts passes `getBinDir()`.
 */

import { join } from 'path'
import {
  BEST_FORMAT_ID,
  type StartDownloadOptions,
  type DownloadOptions,
  type CollectionContext,
  type CookieBrowser,
  type CommandTemplate
} from '@shared/ipc'

// --- Quality → yt-dlp selector mapping --------------------------------------

function videoFormat(quality: string): string {
  switch (quality) {
    case '1080p':
      return 'bv*[height<=1080]+ba/b[height<=1080]'
    case '720p':
      return 'bv*[height<=720]+ba/b[height<=720]'
    case '480p':
      return 'bv*[height<=480]+ba/b[height<=480]'
    case '360p':
      return 'bv*[height<=360]+ba/b[height<=360]'
    default:
      return 'bv*+ba/b' // Best available
  }
}

/**
 * The video format selector. A specific probed format_id wins; otherwise fall
 * back to the height-based preset. Video-only formats get +bestaudio so the
 * merge produces a file with sound (with a video-only fallback if no audio).
 */
function videoSelector(opts: StartDownloadOptions): string {
  if (opts.formatId && opts.formatId !== BEST_FORMAT_ID) {
    return opts.formatHasAudio
      ? opts.formatId
      : `${opts.formatId}+bestaudio/${opts.formatId}`
  }
  return videoFormat(opts.quality)
}

function audioQuality(quality: string): string {
  switch (quality) {
    case '320 kbps':
      return '320K'
    case '192 kbps':
      return '192K'
    case '128 kbps':
      return '128K'
    default:
      return '0' // Best
  }
}

// The progress line yt-dlp emits (one per --newline tick). Note the leading
// `download:` is the progress-template TYPE selector and is consumed by yt-dlp
// (it does NOT appear in the output). The literal `prog|` that follows is our
// own marker, so we can tell progress lines apart from the after-move filepath
// print on the same stdout stream.
export const PROGRESS_TEMPLATE =
  'download:prog|%(progress.status)s|%(progress.downloaded_bytes)s|' +
  '%(progress.total_bytes)s|%(progress.total_bytes_estimate)s|' +
  '%(progress.speed)s|%(progress.eta)s'

// Crop embedded audio artwork to a centred square. The double-quote/single-quote
// dance is deliberate: yt-dlp shlex-splits the `--ppa` value, consuming the outer
// double quotes and leaving ffmpeg single-quoted crop expressions whose commas are
// protected from ffmpeg's filtergraph separator. Side = min(width, height).
export const CROP_SQUARE_PPA =
  'EmbedThumbnail+ffmpeg_o:-c:v mjpeg -vf ' +
  'crop="\'if(gt(ih,iw),iw,ih)\':\'if(gt(iw,ih),ih,iw)\'"'

/**
 * Phase B "Access & networking" settings — not per-download options, always
 * applied from the global settings (there's no per-download override for
 * these, unlike DownloadOptions).
 */
export interface AccessOptions {
  /** yt-dlp --proxy value; empty disables it */
  proxy: string
  /** yt-dlp --limit-rate value, e.g. '2M'; empty means unlimited */
  rateLimit: string
  /** absolute path to aria2c.exe; omit to use yt-dlp's built-in downloader */
  aria2cPath?: string
  /** read auth cookies from an installed browser's own cookie store */
  cookiesFromBrowser?: CookieBrowser
  /** absolute path to a Netscape-format cookie file (the sign-in window's export) */
  cookiesFile?: string
  /** sanitize output filenames to a portable ASCII-only subset */
  restrictFilenames: boolean
  /** absolute path to a --download-archive file; omit to disable archive tracking */
  downloadArchivePath?: string
}

// Tuned for typical CDN-served video: 16 connections split across 16 segments,
// each at least 1MB so tiny files don't get split pointlessly.
export const ARIA2C_ARGS = 'aria2c:-x 16 -s 16 -k 1M'

/**
 * Shell-like split of a raw "extra yt-dlp args" string (Phase C custom-command
 * templates) into argv tokens. Supports single- and double-quoted spans so a
 * flag value containing spaces (e.g. a --ppa recipe) can be typed as one token.
 *
 * LIMITATIONS (audit M2): there is no escape-sequence support (`\"`, `\'`) and
 * quotes cannot nest — a literal quote inside a value can't be expressed, and an
 * unterminated quote falls through to the `\S+` branch and captures the quote
 * char itself. For the yt-dlp use cases this targets (proxy URLs, filename
 * patterns, ffmpeg recipes), that's sufficient. If a future template needs
 * nested or escaped quotes, redesign this to a proper shlex or JSON-based format.
 */
export function parseExtraArgs(raw: string): string[] {
  const args: string[] = []
  const re = /"([^"]*)"|'([^']*)'|(\S+)/g
  let m: RegExpExecArray | null
  while ((m = re.exec(raw)) !== null) {
    args.push(m[1] ?? m[2] ?? m[3])
  }
  return args
}

/**
 * Resolve the extra yt-dlp args for a download, enforcing the custom-command
 * consent gate (audit F2).
 *
 * Extra args are powerful enough to run arbitrary code (e.g. `--exec`), so they
 * are honoured ONLY when custom commands are explicitly enabled in settings —
 * the same persisted flag the Settings UI and backup-import treat as consent. A
 * per-download override wins over the persisted default template, but NEITHER is
 * applied while the gate is off. This keeps a compromised renderer from smuggling
 * code-exec flags through a lone `startDownload({ extraArgs })` call: it would
 * first have to flip the visible `customCommandEnabled` setting, leaving a trace
 * (the same defence-in-depth posture as the main-side maxConcurrent cap).
 *
 *  - customCommandEnabled off               → [] (always)
 *  - perDownloadExtraArgs defined (even '')  → those args
 *  - else a matching defaultTemplateId       → that template's args
 *  - else                                    → []
 */
export function selectExtraArgs(params: {
  customCommandEnabled: boolean
  perDownloadExtraArgs: string | undefined
  defaultTemplateId: string | null
  templates: Pick<CommandTemplate, 'id' | 'args'>[]
}): string[] {
  if (!params.customCommandEnabled) return []
  if (params.perDownloadExtraArgs !== undefined) return parseExtraArgs(params.perDownloadExtraArgs)
  if (params.defaultTemplateId) {
    const tpl = params.templates.find((t) => t.id === params.defaultTemplateId)
    if (tpl) return parseExtraArgs(tpl.args)
  }
  return []
}

// Wrap a single argv token for human-readable display only (Phase C command
// preview) — never used to build the real argv that gets spawned.
function quoteForDisplay(arg: string): string {
  if (arg === '') return '""'
  if (/[\s"]/.test(arg)) return `"${arg.replace(/"/g, '\\"')}"`
  return arg
}

/** Render a binary + argv as a single copy-pasteable command line. */
export function formatCommandLine(exe: string, args: string[]): string {
  return [exe, ...args].map(quoteForDisplay).join(' ')
}

// --- Collection (media-manager) folder paths --------------------------------

/**
 * Sanitize one path segment (a channel or playlist name) into a Windows-safe
 * directory name. This matters because, unlike the filename yt-dlp itself writes
 * (which `--restrict-filenames` can clean), these directory segments are built by
 * AeroFetch from untrusted channel/playlist titles and joined onto the output
 * dir — so they must be neutered for both illegal characters AND path traversal.
 *
 *  - illegal chars (`< > : " / \ | ? *`) and control chars → space
 *  - leading/trailing dots and spaces stripped (illegal / invisible on Windows),
 *    which also turns a bare `..` traversal segment into nothing
 *  - reserved device names (CON, PRN, NUL, COM1…) get an underscore prefix
 *  - length-capped so the full path stays well under MAX_PATH
 *  - empty result falls back to 'Untitled'
 */
export function sanitizeDirSegment(name: string): string {
  // C0 control chars (charCode < 0x20) and Windows-illegal chars both become a
  // space. The control-char filter is done by char code so no literal control
  // byte ever appears in this source file.
  let s = Array.from(name ?? '', (ch) => (ch.charCodeAt(0) < 0x20 ? ' ' : ch)).join('')
  s = s.replace(/[<>:"/\\|?*]/g, ' ')
  s = s.replace(/\s+/g, ' ').trim().replace(/[. ]+$/, '').replace(/^[. ]+/, '')
  // Reserved device names are reserved even WITH an extension ('CON.txt' is still
  // the CON device), so match an optional trailing '.<ext>' too (audit T3).
  if (/^(con|prn|aux|nul|com[1-9]|lpt[1-9])(\..*)?$/i.test(s)) s = `_${s}`
  s = s.slice(0, 80).trim()
  return s || 'Untitled'
}

/**
 * Build the `-o` output template for a collection download:
 *   <outDir>/<Channel>/<Playlist>/<NNN> - <baseFilename>
 * where NNN is the 1-based playlist index zero-padded to three digits and
 * baseFilename keeps its yt-dlp field tokens (e.g. '%(title)s.%(ext)s') so they
 * still expand. Channel/playlist are sanitized via sanitizeDirSegment.
 */
export function collectionOutputTemplate(
  outDir: string,
  c: CollectionContext,
  baseFilename: string
): string {
  const n = Number.isFinite(c.index) && c.index > 0 ? Math.floor(c.index) : 1
  const nnn = String(n).padStart(3, '0')
  const segments = [sanitizeDirSegment(c.channel), sanitizeDirSegment(c.playlist)]
  return join(outDir, ...segments, `${nnn} - ${baseFilename}`)
}

function accessArgs(a: AccessOptions): string[] {
  const args: string[] = []
  if (a.proxy.trim()) args.push('--proxy', a.proxy.trim())
  if (a.rateLimit.trim()) args.push('--limit-rate', a.rateLimit.trim())
  if (a.aria2cPath) args.push('--downloader', a.aria2cPath, '--downloader-args', ARIA2C_ARGS)
  // cookiesFromBrowser and cookiesFile are mutually exclusive sources — the UI
  // only ever sets one (driven by Settings.cookieSource), but browser wins if
  // a caller somehow sets both.
  if (a.cookiesFromBrowser) args.push('--cookies-from-browser', a.cookiesFromBrowser)
  else if (a.cookiesFile) args.push('--cookies', a.cookiesFile)
  if (a.restrictFilenames) args.push('--restrict-filenames')
  if (a.downloadArchivePath) args.push('--download-archive', a.downloadArchivePath)
  return args
}

/** Subtitle / SponsorBlock / chapter / metadata flags shared by both kinds. */
function postProcessArgs(opts: StartDownloadOptions, o: DownloadOptions): string[] {
  const args: string[] = []

  // Subtitles — video only; audio extraction has nowhere to embed them.
  if (opts.kind === 'video' && o.embedSubtitles) {
    args.push('--write-subs', '--embed-subs', '--sub-langs', o.subtitleLanguages || 'en')
    if (o.autoSubtitles) args.push('--write-auto-subs')
    // Normalise to srt first so embedding works across containers (mp4 → mov_text).
    args.push('--convert-subs', 'srt')
  }

  // SponsorBlock.
  if (o.sponsorBlock && o.sponsorBlockCategories.length > 0) {
    const cats = o.sponsorBlockCategories.join(',')
    if (o.sponsorBlockMode === 'remove') {
      // Force keyframes at the cut points so segment boundaries are frame-accurate.
      args.push('--sponsorblock-remove', cats, '--force-keyframes-at-cuts')
    } else {
      args.push('--sponsorblock-mark', cats)
    }
  }

  if (o.embedChapters) args.push('--embed-chapters')
  if (o.embedMetadata) args.push('--embed-metadata')

  // Media-server sidecar files (Phase K) — written next to the output file so
  // Jellyfin/Plex/Kodi can ingest metadata, poster art, and the description.
  if (o.writeInfoJson) args.push('--write-info-json')
  if (o.writeThumbnailFile) args.push('--write-thumbnail')
  if (o.writeDescription) args.push('--write-description')

  return args
}

export function buildArgs(
  opts: StartDownloadOptions,
  outputTemplate: string,
  o: DownloadOptions,
  binDir: string,
  access: AccessOptions,
  extraArgs: string[] = []
): string[] {
  const args = [
    '--newline',
    '--no-color',
    '--no-playlist',
    // --print (below) implies --quiet, which would suppress progress; --progress
    // forces the progress template to emit anyway.
    '--progress',
    '--ffmpeg-location',
    binDir,
    '-o',
    outputTemplate,
    '--progress-template',
    PROGRESS_TEMPLATE,
    // Print the final path after post-processing/move so we can open it later.
    '--print',
    'after_move:path|%(filepath)s',
    '--no-simulate'
  ]

  args.push(...accessArgs(access))
  args.push(...postProcessArgs(opts, o))

  if (opts.kind === 'audio') {
    args.push('-x', '--audio-format', o.audioFormat, '--audio-quality', audioQuality(opts.quality))
    if (o.embedThumbnail) {
      args.push('--embed-thumbnail')
      if (o.cropThumbnail) args.push('--ppa', CROP_SQUARE_PPA)
    }
  } else {
    args.push('-f', videoSelector(opts), '--merge-output-format', o.videoContainer)
    // Codec preference is a sort tiebreaker AFTER resolution/fps, so it nudges the
    // pick toward the chosen codec without overriding the requested quality.
    if (o.preferredVideoCodec !== 'any') {
      const token = o.preferredVideoCodec === 'av1' ? 'av01' : o.preferredVideoCodec
      args.push('-S', `res,fps,vcodec:${token}`)
    }
    // mp4/mkv carry a cover image; webm has no reliable way to embed one.
    if (o.embedThumbnail && o.videoContainer !== 'webm') args.push('--embed-thumbnail')
  }

  // Custom-command extra args go last, immediately before the `--` URL
  // terminator, so a user-supplied flag can override anything chosen above
  // (yt-dlp takes the last occurrence of most options).
  if (extraArgs.length > 0) args.push(...extraArgs)

  // `--` terminates option parsing so the URL can never be read as a flag.
  args.push('--', opts.url)
  return args
}