#!/usr/bin/env node
// Cuts the approved shot clips into one text-free teaser with ffmpeg: trims, cuts or dissolves,
// one grade preset over every shot, optional bloom, grain and vignette, an optional centre crop
// (e.g. 9:16 to 4:5 for a feed post), a short fade-out, then H.264 MP4 with +faststart.
// No text is added: the user puts their own captions on in the app they post from.
//
// Usage:
//   node scripts/assemble-teaser.mjs --teaser teaser.json --out teaser.mp4
//     [--grade teal-amber|warm-kodak|cool-fuji|blue-hour|natural|none]
//     [--grain 0-20] [--bloom 0-0.4] [--vignette 0-1] [--dissolve 0.2-1.5] [--fade-out 0-1.5]
//     [--crop none|9:16|4:5|1:1|16:9] [--audio none|clips] [--music track.mp3] [--music-volume 0-1]
//     [--only 1,2,5] [--max-shot 3.5] [--crf 10-30] [--max-mb 8] [--dry-run]
//
// Requires ffmpeg and ffprobe on PATH. Node 18 or newer. No npm packages.

import { spawnSync } from 'node:child_process'
import { existsSync, mkdtempSync, readFileSync, rmSync, statSync, writeFileSync } from 'node:fs'
import { tmpdir } from 'node:os'
import { dirname, isAbsolute, join, resolve } from 'node:path'

const FLAGS = new Set(['teaser', 'out', 'grade', 'grain', 'bloom', 'vignette', 'dissolve', 'fade-out', 'crop', 'audio', 'music', 'music-volume', 'only', 'max-shot', 'crf', 'max-mb', 'dry-run'])
const SWITCHES = new Set(['dry-run'])

// Grade presets: plain ffmpeg filter chains. See references/look-and-light.md.
const GRADES = {
  'teal-amber': "colorbalance=rs=-0.06:gs=0.01:bs=0.06:rm=0.03:gm=-0.01:bm=-0.03:rh=0.05:gh=-0.01:bh=-0.05,curves=master='0/0.035 0.25/0.21 0.5/0.5 0.78/0.80 1/0.95',eq=saturation=0.9",
  'warm-kodak': "colorbalance=rs=0.03:gs=0:bs=-0.03:rm=0.04:gm=0.01:bm=-0.04:rh=0.03:gh=0.01:bh=-0.04,curves=master='0/0.03 0.3/0.28 0.7/0.74 1/0.96',eq=saturation=1.03",
  'cool-fuji': "colorbalance=rs=-0.03:gs=0.02:bs=0.04:rm=-0.02:gm=0.02:bm=0.01:rh=0.01:gh=0.01:bh=0.02,curves=master='0/0.04 0.3/0.29 0.7/0.72 1/0.95',eq=saturation=0.88",
  'blue-hour': "colorbalance=rs=-0.04:gs=0:bs=0.05:rm=-0.01:gm=0:bm=0.02:rh=0.06:gh=0.02:bh=-0.05,curves=master='0/0.03 0.25/0.22 0.6/0.6 1/0.96',eq=saturation=0.95",
  natural: "curves=master='0/0.02 0.25/0.23 0.75/0.77 1/0.98'",
  none: 'null',
}

function fail(message) {
  console.error(message)
  process.exit(1)
}

function parseFlags(argv) {
  const out = {}
  for (let i = 0; i < argv.length; i++) {
    const a = argv[i]
    if (!a.startsWith('--')) fail(`Unexpected argument "${a}". Flags look like --name value.`)
    const key = a.slice(2)
    if (!FLAGS.has(key)) fail(`Unknown flag --${key}. Allowed: ${[...FLAGS].map((f) => `--${f}`).join(', ')}`)
    if (SWITCHES.has(key)) { out[key] = true; continue }
    const value = argv[i + 1]
    if (value === undefined || value.startsWith('--')) fail(`--${key} needs a value.`)
    out[key] = value
    i++
  }
  return out
}

function num(value, name, min, max, fallback) {
  if (value === undefined || value === null) return fallback
  const n = Number(value)
  if (!Number.isFinite(n) || n < min || n > max) fail(`${name} must be a number from ${min} to ${max}, got "${value}".`)
  return n
}

function run(cmd, args, label) {
  const r = spawnSync(cmd, args, { encoding: 'utf8', maxBuffer: 64 * 1024 * 1024 })
  if (r.error?.code === 'ENOENT') fail(`${cmd} is not installed or not on PATH. Install ffmpeg (it includes ffprobe) and try again.`)
  if (r.status !== 0) fail(`${label} failed:\n${(r.stderr || '').split('\n').slice(-15).join('\n')}`)
  return r.stdout
}

function probe(path) {
  const j = JSON.parse(run('ffprobe', ['-v', 'error', '-print_format', 'json', '-show_streams', '-show_format', path], `ffprobe ${path}`))
  const v = j.streams.find((s) => s.codec_type === 'video')
  if (!v) fail(`${path} has no video stream. Pass the MP4 clips Seedance returned, not stills.`)
  return { width: v.width, height: v.height, duration: Number(j.format.duration), hasAudio: j.streams.some((s) => s.codec_type === 'audio') }
}

const even = (n) => Math.max(2, Math.floor(n / 2) * 2)
const f3 = (n) => Number(n).toFixed(3)

const opts = parseFlags(process.argv.slice(2))
if (!opts.teaser || !opts.out) fail('Usage: node scripts/assemble-teaser.mjs --teaser teaser.json --out teaser.mp4 [options]. See the header of this file for every option.')
if (!existsSync(opts.teaser)) fail(`Shot list not found: ${opts.teaser}. Create it with scripts/build-shot-list.mjs.`)
let teaser
try {
  teaser = JSON.parse(readFileSync(opts.teaser, 'utf8'))
} catch {
  fail(`${opts.teaser} is not valid JSON.`)
}
const base = dirname(resolve(opts.teaser))
const rel = (p) => (isAbsolute(p) ? p : join(base, p))
const look = teaser.look ?? {}

const grade = opts.grade ?? look.grade ?? 'natural'
if (!(grade in GRADES)) fail(`--grade must be one of ${Object.keys(GRADES).join(', ')}, not "${grade}".`)
const grain = num(opts.grain ?? look.grain, '--grain', 0, 20, 6)
const bloom = num(opts.bloom ?? look.bloom, '--bloom', 0, 0.4, 0.1)
const vignette = num(opts.vignette ?? look.vignette, '--vignette', 0, 1, 0.3)
const dissolve = num(opts.dissolve ?? look.dissolve, '--dissolve', 0.2, 1.5, 0.5)
const fadeOut = num(opts['fade-out'] ?? look.fade_out, '--fade-out', 0, 1.5, 0.5)
const crf = num(opts.crf, '--crf', 10, 30, 20)
const maxMb = opts['max-mb'] === undefined ? null : num(opts['max-mb'], '--max-mb', 1, 500)
const maxShot = opts['max-shot'] === undefined ? null : num(opts['max-shot'], '--max-shot', 1, 30)
const musicVolume = num(opts['music-volume'], '--music-volume', 0, 1, 0.8)
const crop = opts.crop ?? 'none'
if (!['none', '9:16', '4:5', '1:1', '16:9'].includes(crop)) fail(`--crop must be none, 9:16, 4:5, 1:1 or 16:9, not "${crop}".`)
const audioMode = opts.audio ?? 'none'
if (!['none', 'clips'].includes(audioMode)) fail(`--audio must be none or clips, not "${audioMode}".`)
if (opts.music && !existsSync(opts.music)) fail(`Music file not found: ${opts.music}. Use an MP3 or WAV you have the rights to.`)
if (opts.music && !/\.(mp3|wav|m4a|aac|flac)$/i.test(opts.music)) fail(`--music must be an audio file (.mp3, .wav, .m4a, .aac or .flac) that you own or licensed, not ${opts.music}.`)

if (!Array.isArray(teaser.shots) || !teaser.shots.length) fail('The shot list has no shots.')
let shots = teaser.shots.filter((s) => s.clip && !s.skip)
if (opts.only) {
  const wanted = opts.only.split(',').map((x) => Number(x.trim()))
  if (wanted.some((n) => !Number.isInteger(n))) fail(`--only takes shot numbers like 1,2,5, not "${opts.only}".`)
  shots = wanted.map((n) => {
    const s = teaser.shots.find((x) => x.n === n)
    if (!s) fail(`--only: there is no shot number ${n}.`)
    if (!s.clip) fail(`--only: shot ${n} has no clip yet.`)
    return s
  })
}
if (!shots.length) fail('No shot has a "clip" path yet. Add the approved Seedance MP4 paths to the shot list first.')

const clips = shots.map((s) => {
  const path = rel(s.clip)
  if (!existsSync(path)) fail(`Shot ${s.n}: clip not found at ${path}.`)
  if (!/\.(mp4|mov|webm)$/i.test(path)) fail(`Shot ${s.n}: "${s.clip}" is not a video. Use the MP4 that Seedance returned.`)
  const info = probe(path)
  const inT = Number(s.in ?? 0)
  let outT = Number(s.out ?? info.duration)
  if (!Number.isFinite(inT) || !Number.isFinite(outT) || inT < 0 || outT <= inT) fail(`Shot ${s.n}: "in" and "out" must be seconds with in < out.`)
  if (outT > info.duration + 0.05) fail(`Shot ${s.n}: "out" (${outT}s) is past the end of the clip (${info.duration.toFixed(2)}s).`)
  outT = Math.min(outT, info.duration)
  if (maxShot && outT - inT > maxShot) outT = inT + maxShot
  return { shot: s, path, info, inT, outT, len: outT - inT }
})

const W = Math.min(...clips.map((c) => c.info.width))
const H = Math.min(...clips.map((c) => c.info.height))
if (new Set(clips.map((c) => (c.info.width / c.info.height).toFixed(2))).size > 1) fail('The clips have different aspect ratios. Generate every shot at the same aspect (all 9:16 or all 16:9).')
if (audioMode === 'clips') for (const c of clips) if (!c.info.hasAudio) fail(`Shot ${c.shot.n} has no audio. Use --audio none, or regenerate with generate_audio: true.`)

let outW = W
let outH = H
if (crop !== 'none') {
  const [a, b] = crop.split(':').map(Number)
  if (W / H > a / b) { outH = even(H); outW = even((H * a) / b) } else { outW = even(W); outH = even((W * b) / a) }
}

const tmp = mkdtempSync(join(tmpdir(), 'assemble-teaser-'))
const inputs = []
const graph = []
clips.forEach((c, i) => {
  inputs.push('-i', c.path)
  graph.push(`[${i}:v]trim=start=${f3(c.inT)}:end=${f3(c.outT)},setpts=PTS-STARTPTS,fps=24,scale=${W}:${H}:flags=lanczos,setsar=1,format=yuv420p,settb=1/24[s${i}]`)
})

const starts = [0]
const joins = []
let acc = 's0'
let total = clips[0].len
for (let i = 1; i < clips.length; i++) {
  const next = `j${i}`
  if (clips[i].shot.transition_in === 'dissolve') {
    const d = Math.min(dissolve, clips[i].len / 2, clips[i - 1].len / 2)
    graph.push(`[${acc}][s${i}]xfade=transition=fade:duration=${f3(d)}:offset=${f3(total - d)},settb=1/24[${next}]`)
    starts.push(total - d)
    joins.push({ at: total - d, type: 'dissolve', d })
    total += clips[i].len - d
  } else {
    graph.push(`[${acc}][s${i}]concat=n=2:v=1:a=0,settb=1/24[${next}]`)
    starts.push(total)
    joins.push({ at: total, type: 'cut', d: 0 })
    total += clips[i].len
  }
  acc = next
}

let chain = acc
if (bloom > 0) {
  graph.push(`[${chain}]split[bm0][bm1];[bm1]format=gbrp,curves=all='0/0 0.62/0 1/1',gblur=sigma=${Math.round(Math.min(W, H) / 36)}[bm2];[bm0]format=gbrp[bm3];[bm3][bm2]blend=all_mode=screen:all_opacity=${bloom},format=yuv420p[bloomed]`)
  chain = 'bloomed'
}
const post = [GRADES[grade]]
if (crop !== 'none') post.push(`crop=${outW}:${outH}:(iw-${outW})/2:(ih-${outH})/2`)
if (grain > 0) post.push(`noise=c0s=${grain}:c0f=t+u`)
if (vignette > 0) post.push(`vignette=angle=${(0.15 + 0.5 * vignette).toFixed(3)}`)
if (fadeOut > 0) post.push(`fade=t=out:st=${f3(total - fadeOut)}:d=${f3(fadeOut)}`)
post.push('format=yuv420p')
graph.push(`[${chain}]${post.join(',')}[vout]`)

let audioLabel = null
const inputIndex = clips.length
if (audioMode === 'clips') {
  clips.forEach((c, i) => graph.push(`[${i}:a]atrim=start=${f3(c.inT)}:end=${f3(c.outT)},asetpts=PTS-STARTPTS,aresample=48000,aformat=sample_fmts=fltp:channel_layouts=stereo,afade=t=in:d=0.04,afade=t=out:st=${f3(Math.max(0, c.len - 0.04))}:d=0.04[ca${i}]`))
  let a = 'ca0'
  for (let i = 1; i < clips.length; i++) {
    const j = joins[i - 1]
    graph.push(j.type === 'dissolve' ? `[${a}][ca${i}]acrossfade=d=${f3(j.d)}[aj${i}]` : `[${a}][ca${i}]concat=n=2:v=0:a=1[aj${i}]`)
    a = `aj${i}`
  }
  graph.push(`[${a}]apad=whole_dur=${f3(total)},atrim=0:${f3(total)},afade=t=out:st=${f3(Math.max(0, total - 1))}:d=1,volume=${opts.music ? 0.55 : 1}[clipaudio]`)
  audioLabel = 'clipaudio'
}
if (opts.music) {
  inputs.push('-stream_loop', '-1', '-i', opts.music)
  graph.push(`[${inputIndex}:a]atrim=0:${f3(total)},asetpts=PTS-STARTPTS,aresample=48000,aformat=sample_fmts=fltp:channel_layouts=stereo,volume=${musicVolume},afade=t=in:d=0.5,afade=t=out:st=${f3(Math.max(0, total - 1.5))}:d=1.5[music]`)
  if (audioLabel) {
    graph.push(`[${audioLabel}][music]amix=inputs=2:duration=first:normalize=0[aout]`)
    audioLabel = 'aout'
  } else audioLabel = 'music'
}

const common = ['-y', '-hide_banner', '-v', 'error', ...inputs, '-filter_complex', graph.join(';'), '-map', '[vout]']
const video = ['-c:v', 'libx264', '-preset', 'slow', '-tune', 'grain', '-profile:v', 'high', '-pix_fmt', 'yuv420p', '-r', '24']
const audio = audioLabel ? ['-map', `[${audioLabel}]`, '-c:a', 'aac', '-b:a', '160k'] : ['-an']
const tail = ['-t', f3(total), '-movflags', '+faststart']

if (opts['dry-run']) {
  console.log(`Filter graph:\n${graph.join(';\n')}\n\nDuration: ${total.toFixed(2)} s, ${outW}x${outH}`)
  rmSync(tmp, { recursive: true, force: true })
  process.exit(0)
}

if (maxMb) {
  const audioKbps = audioLabel ? 160 : 0
  const videoKbps = Math.floor((maxMb * 8 * 1024 * 0.94) / total - audioKbps)
  if (videoKbps < 600) fail(`--max-mb ${maxMb} is too small for ${total.toFixed(1)} s. Raise it or cut a shorter version.`)
  const passlog = join(tmp, 'pass')
  run('ffmpeg', [...common, ...video, '-b:v', `${videoKbps}k`, '-pass', '1', '-passlogfile', passlog, '-an', '-t', f3(total), '-f', 'mp4', process.platform === 'win32' ? 'NUL' : '/dev/null'], 'ffmpeg pass 1')
  run('ffmpeg', [...common, ...video, '-b:v', `${videoKbps}k`, '-maxrate', `${Math.round(videoKbps * 1.5)}k`, '-bufsize', `${videoKbps * 2}k`, '-pass', '2', '-passlogfile', passlog, ...audio, ...tail, opts.out], 'ffmpeg pass 2')
} else {
  run('ffmpeg', [...common, ...video, '-crf', String(crf), ...audio, ...tail, opts.out], 'ffmpeg')
}
rmSync(tmp, { recursive: true, force: true })

const edl = { file: opts.out, width: outW, height: outH, duration: Number(total.toFixed(3)), grade, grain, bloom, vignette, crop, shots: clips.map((c, i) => ({ n: c.shot.n, start: Number(starts[i].toFixed(3)), length: Number(c.len.toFixed(3)), in: c.inT, out: Number(c.outT.toFixed(3)) })), joins: [...joins.map((j) => ({ ...j, at: Number(j.at.toFixed(3)), d: Number(j.d.toFixed(3)) })), ...(fadeOut > 0 ? [{ at: Number((total - fadeOut).toFixed(3)), type: 'fade-out', d: fadeOut }] : [])] }
writeFileSync(`${opts.out}.edl.json`, JSON.stringify(edl, null, 2))
const mb = statSync(opts.out).size / 1024 / 1024
console.log(`${opts.out}  ${outW}x${outH}  ${total.toFixed(2)} s  ${mb.toFixed(2)} MB  grade=${grade}\nEdit list: ${opts.out}.edl.json\nNext: node scripts/check-teaser.mjs --file ${opts.out} --edl ${opts.out}.edl.json`)