import type { ClipMetadata, SegmentsPayload, StreamEvent, VeoSegment } from '@/types';

/**
 * In dev, use same-origin `/api` so the Vite proxy handles SSE (EventSource) without CORS.
 * Ngrok and other tunnels often omit Access-Control-Allow-Origin on streamed responses.
 * Set `VITE_PUBLIC_API_IN_DEV=true` only if your API sends proper CORS for localhost.
 * Production: set `VITE_API_BASE_URL` to your deployed API origin.
 */
const API_BASE =
  import.meta.env.DEV && import.meta.env.VITE_PUBLIC_API_IN_DEV !== 'true'
    ? ''
    : (import.meta.env.VITE_API_BASE_URL || '');

/**
 * Hero preview in the UI: prefer the storefront CDN URL when we have it (always a real image).
 * Otherwise use blob/data URLs as-is. For hosted /api/images/... URLs, use a path-only URL in dev
 * so the Vite proxy loads pixels (ngrok-free and some tunnels return HTML for absolute image GETs).
 */
export function imageSrcForHeroPreview(
  heroRemoteUrl: string | null,
  imagePreview: string | null
): string | null {
  if (heroRemoteUrl) return heroRemoteUrl;
  if (!imagePreview) return null;
  if (imagePreview.startsWith('blob:') || imagePreview.startsWith('data:')) return imagePreview;

  if (imagePreview.includes('/api/images/') && import.meta.env.DEV) {
    try {
      return new URL(imagePreview).pathname;
    } catch {
      return imagePreview.startsWith('/') ? imagePreview : null;
    }
  }

  return imagePreview;
}

const GPT_IMAGE_EDIT_MAX_REFS = 4;

/**
 * Build 2–4 distinct product image URLs for GPT Image `edits` (e.g. gpt-image-2).
 * Merges the hosted hero (this run), storefront hero, and scraped gallery so models
 * see multiple angles when available — not just a single frame.
 */
export function pickProductReferenceUrlsForGpt(options: {
  hostedUrl: string | null;
  heroRemoteUrl: string | null;
  scrapedImageUrls: string[];
  max?: number;
}): string[] {
  const max = Math.min(GPT_IMAGE_EDIT_MAX_REFS, Math.max(1, options.max ?? GPT_IMAGE_EDIT_MAX_REFS));
  const out: string[] = [];
  const seen = new Set<string>();

  const push = (u: string | null | undefined): boolean => {
    const s = (u ?? '').trim();
    if (!s || seen.has(s)) return false;
    seen.add(s);
    out.push(s);
    return out.length >= max;
  };

  if (push(options.hostedUrl)) return out;
  if (push(options.heroRemoteUrl)) return out;
  for (const u of options.scrapedImageUrls) {
    if (push(u)) break;
  }

  return out;
}

async function parseError(res: Response, fallback: string): Promise<string> {
  const ct = res.headers.get('content-type');
  try {
    if (ct?.includes('application/json')) {
      const j = await res.json();
      return j.detail || j.message || fallback;
    }
    const t = await res.text();
    return t?.trim() || fallback;
  } catch {
    return fallback;
  }
}

export interface HealthStatus {
  status: string;
  service?: string;
  kie_configured: boolean;
  /** Seedance can fall back to Replicate when KIE fails if this is true */
  replicate_configured?: boolean;
  openai_configured: boolean;
  gpt_image_model?: string;
  ffmpeg_available?: boolean;
  ffprobe_available?: boolean;
  public_base_url?: string;
  server_port?: number;
}

export async function checkHealth(): Promise<HealthStatus> {
  const url = `${API_BASE}/health`;
  const res = await fetch(url);
  if (!res.ok) throw new Error(await parseError(res, 'Health check failed'));
  return res.json();
}

export async function uploadImage(file: File): Promise<{ url: string }> {
  const fd = new FormData();
  fd.append('file', file);
  const res = await fetch(`${API_BASE}/api/upload-image`, { method: 'POST', body: fd });
  if (!res.ok) throw new Error(await parseError(res, 'Upload failed'));
  return res.json();
}

export interface ScrapeProductResponse {
  product_name: string;
  description: string;
  price: string;
  offers: string;
  target_audience: string;
  product_images: string;
  brand: string;
  category: string;
  image_urls: string[];
  source_url: string;
  [key: string]: unknown;
}

export async function scrapeProductPage(url: string): Promise<ScrapeProductResponse> {
  const res = await fetch(`${API_BASE}/api/showcase/scrape`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ url }),
  });
  if (!res.ok) throw new Error(await parseError(res, 'Scrape failed'));
  return res.json();
}

export async function hostImageFromUrl(url: string): Promise<{ url: string; source_url: string }> {
  const res = await fetch(`${API_BASE}/api/host-image-url`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ url }),
  });
  if (!res.ok) throw new Error(await parseError(res, 'Could not host image'));
  return res.json();
}

export async function generateDirectConcepts(params: {
  productName: string;
  description?: string;
  price?: string;
  targetAudience?: string;
  count?: number;
  ugcCount?: number;
  modelShowcaseCount?: number;
  featureHighlightCount?: number;
}): Promise<{
  concepts: string[];
  concept_groups?: {
    ugc: string[];
    model_showcase: string[];
    feature_highlight: string[];
  };
  concept_execution_plans?: Record<
    string,
    {
      duration_seconds: number;
      render_mode: 'direct_seedance' | 'segmented';
      reference_frame_prompts: string[];
    }
  >;
}> {
  const res = await fetch(`${API_BASE}/api/showcase/direct-concepts`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
      product_name: params.productName,
      tagline: params.description ?? '',
      mood: params.price ? `price: ${params.price}` : '',
      target_audience: params.targetAudience ?? '',
      count: params.count ?? 10,
      ugc_count: params.ugcCount ?? 4,
      model_showcase_count: params.modelShowcaseCount ?? 3,
      feature_highlight_count: params.featureHighlightCount ?? 3,
    }),
  });
  if (!res.ok) throw new Error(await parseError(res, 'Concept generation failed'));
  return res.json();
}

export async function regenerateDirectConcept(params: {
  productName: string;
  description?: string;
  price?: string;
  targetAudience?: string;
  exclude?: string[];
  index?: number;
}): Promise<{ concept: string }> {
  const res = await fetch(`${API_BASE}/api/showcase/direct-concept-one`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
      product_name: params.productName,
      tagline: params.description ?? '',
      mood: params.price ? `price: ${params.price}` : '',
      target_audience: params.targetAudience ?? '',
      exclude: params.exclude ?? [],
      index: params.index ?? 1,
    }),
  });
  if (!res.ok) throw new Error(await parseError(res, 'Concept regeneration failed'));
  return res.json();
}

/** Must match backend `showcase_prompts._CONCEPTS` keys. */
export const SHOWCASE_CONCEPT_OPTIONS = [
  {
    id: 'luxury_studio',
    label: 'Luxury studio launch',
    description: 'Slow dolly, pedestal, whisper VO — flagship packshot grammar.',
    category: 'Commercial',
  },
  {
    id: 'ugc_authentic',
    label: 'UGC / social authentic',
    description: 'Handheld, desk or counter, creator energy — short-form hooks.',
    category: 'Social',
  },
  {
    id: 'tech_minimal',
    label: 'Tech / minimal',
    description: 'Void set, hard edge light, precise motion — device-film calm.',
    category: 'Commercial',
  },
  {
    id: 'lifestyle_natural',
    label: 'Lifestyle / natural light',
    description: 'Real rooms, sun paths, slow living — editorial home story.',
    category: 'Commercial',
  },
  {
    id: 'bold_editorial',
    label: 'Bold / color editorial',
    description: 'Gels, graphic shadows, campaign-poster energy.',
    category: 'Experimental',
  },
  {
    id: 'unboxing_asmr',
    label: 'Unboxing / desk ASMR',
    description: 'Top-down peel, satisfying motion, whisper pacing.',
    category: 'Social',
  },
  {
    id: 'high_energy_sports',
    label: 'High-energy sports',
    description: 'Kinetic camera, impact cuts, performance-first momentum.',
    category: 'Commercial',
  },
  {
    id: 'moody_cinematic_noir',
    label: 'Moody cinematic noir',
    description: 'Chiaroscuro lighting, suspense pacing, dramatic reveals.',
    category: 'Experimental',
  },
  {
    id: 'playful_stopmotion_style',
    label: 'Playful stop-motion style',
    description: 'Tabletop whimsy, snappy object beats, colorful transitions.',
    category: 'Experimental',
  },
  {
    id: 'nature_outdoor_adventure',
    label: 'Nature / outdoor adventure',
    description: 'Golden trails, outdoor scale, utility-forward storytelling.',
    category: 'Commercial',
  },
] as const;

export type ShowcaseConceptId = (typeof SHOWCASE_CONCEPT_OPTIONS)[number]['id'];

export async function showcasePlanStream(
  params: {
    productName: string;
    description?: string;
    price?: string;
    targetAudience: string;
    shotCount: number;
    /** Optional override; when omitted backend chooses 4/6/8 from concept + product brief. */
    secondsPerSegment?: number;
    /** Creative arc for shot planning (template + GPT). */
    creativeConcept?: ShowcaseConceptId;
    image?: File | null;
    /** Original CDN URL for vision (optional); file upload takes precedence when present. */
    heroImageUrl?: string;
  },
  onEvent: (e: StreamEvent) => void,
  signal?: AbortSignal
): Promise<SegmentsPayload> {
  const fd = new FormData();
  fd.append('productName', params.productName);
  fd.append('tagline', params.description ?? '');
  fd.append('mood', params.price ? `price: ${params.price}` : '');
  fd.append('targetAudience', params.targetAudience);
  fd.append('shotCount', String(params.shotCount));
  if (params.secondsPerSegment != null) {
    fd.append('secondsPerSegment', String(params.secondsPerSegment));
  }
  fd.append('creativeConcept', params.creativeConcept ?? 'luxury_studio');
  if (params.image) fd.append('image', params.image);
  if (params.heroImageUrl) fd.append('heroImageUrl', params.heroImageUrl);

  const res = await fetch(`${API_BASE}/api/showcase/plan-stream`, {
    method: 'POST',
    body: fd,
    signal,
  });
  if (!res.ok) throw new Error(await parseError(res, 'Shot plan failed'));
  if (!res.body) throw new Error('No response body');

  const reader = res.body.getReader();
  const dec = new TextDecoder();
  let buf = '';
  let final: SegmentsPayload | null = null;

  try {
    while (true) {
      const { done, value } = await reader.read();
      if (done) break;
      buf += dec.decode(value, { stream: true });
      const lines = buf.split('\n');
      buf = lines.pop() || '';
      for (const line of lines) {
        if (!line.trim()) continue;
        const ev = JSON.parse(line) as StreamEvent;
        onEvent(ev);
        if (ev.event === 'complete') final = ev.payload;
        if (ev.event === 'error') throw new Error(ev.message);
      }
    }
  } finally {
    reader.releaseLock();
  }

  if (!final) throw new Error('Stream ended without complete payload');
  return final;
}

export interface KlingGenerateResponse {
  taskId: string;
  status: string;
}

/** Parse segment_info.duration ("4s", "8s") for Veo / trim. */
export function segmentClipSeconds(segment: { segment_info?: { duration?: string } }): 4 | 6 | 8 {
  const raw = segment.segment_info?.duration ?? '';
  const m = String(raw).match(/^(\d+)/);
  if (m) {
    const n = parseInt(m[1], 10);
    if (n === 4 || n === 6 || n === 8) return n;
  }
  return 8;
}

export type SegmentVideoModel = 'veo3_fast' | 'seedance-2' | 'seedance-2-fast';

export type SeedanceSegmentModel = 'seedance-2' | 'seedance-2-fast';

/** UI segment model → KIE `jobs/createTask` model id. */
export function kieSeedanceModelId(model: SeedanceSegmentModel): string {
  return model === 'seedance-2-fast' ? 'bytedance/seedance-2-fast' : 'bytedance/seedance-2';
}

export function isSeedanceSegmentModel(model: SegmentVideoModel): model is SeedanceSegmentModel {
  return model === 'seedance-2' || model === 'seedance-2-fast';
}

/** Replicate model page (pricing tiers documented there). */
export const REPLICATE_SEEDANCE_20_URL = 'https://replicate.com/bytedance/seedance-2.0';

/**
 * Replicate bills by **output video seconds**. Image / reference inputs use the `non_video_in` column
 * on the Seedance 2.0 pricing grid (as of early 2026 on the model page).
 */
export const REPLICATE_SEEDANCE_20_NON_VIDEO_IN_USD_PER_SEC: Record<'480p' | '720p' | '1080p', number> = {
  '480p': 0.08,
  '720p': 0.18,
  '1080p': 0.45,
};

export function replicateSeedance20NonVideoInUsdPerSec(
  resolution: '480p' | '720p' | '1080p'
): number {
  return REPLICATE_SEEDANCE_20_NON_VIDEO_IN_USD_PER_SEC[resolution];
}

/** Total USD estimate for Replicate Seedance 2.0 (non–video-in) at a given resolution and output seconds. */
export function estimateReplicateSeedance20Usd(params: {
  resolution: '480p' | '720p' | '1080p';
  totalOutputSeconds: number;
}): { usdPerSecond: number; estimatedUsd: number } {
  const usdPerSecond = replicateSeedance20NonVideoInUsdPerSec(params.resolution);
  const estimatedUsd = usdPerSecond * Math.max(0, params.totalOutputSeconds);
  return { usdPerSecond, estimatedUsd };
}

/** Heuristic: product or shot text is likely wearable jewelry (rings, earrings, etc.). */
export function textSuggestsJewelry(...parts: (string | undefined | null)[]): boolean {
  const t = parts.map((p) => String(p || '').toLowerCase()).join(' ');
  if (!t.trim()) return false;
  if (/\bring\s+light\b/.test(t)) return false;
  return /\b(?:rings?|necklaces?|bracelets?|earrings?|pendants?|bangles?|anklets?|chokers?|lockets?|studs?|hoops?|cartilage|lobe|jewelry|jewellery|mangalsutra|nose\s*pin|925|14k|18k|karat|carat|sterling)\b/.test(
    t
  );
}

/** Seedance / video instructions when jewelry appears on a person. */
export function jewelryWearPlacementPromptBlock(): string {
  return (
    '[WEAR_PLACEMENT — jewelry on body] ' +
      'When a person wears the hero piece it must rest on real anatomy with believable contact—no floating, no metal clipping through skin, no z-fighting. ' +
      'Scale must match the references (band width, stone size vs finger or ear). ' +
      'Rings: default to the ring finger (fourth digit) of the visible hand unless a reference clearly shows another finger; band sits between knuckles with consistent top-facing stone orientation. ' +
      'Earrings: pierced placement at lobe or cartilage as the SKU implies; symmetric pair when the product is a pair. ' +
      'Necklaces: natural gravity drape at collarbone/sternum; clasp hidden at nape when appropriate. ' +
      'Bracelets / anklets: centered on wrist or ankle joint, not mid-forearm or calf. ' +
      'Keep the exact same SKU silhouette and metal color as the reference set—no resized cartoon prop or mirrored design error on the body.'
  );
}

/** Flatten structured segment JSON into a Seedance text prompt (max 20k on API). */
export function segmentToSeedancePrompt(segment: VeoSegment, productName?: string): string {
  const ch = segment.character_description;
  const sc = segment.scene_continuity;
  const at = segment.action_timeline;
  const lines: string[] = [];
  if (productName?.trim()) lines.push(`Product: ${productName.trim()}.`);
  if (ch?.current_state) lines.push(ch.current_state);
  if (sc?.environment) lines.push(sc.environment);
  if (sc?.camera_position) lines.push(`Camera: ${sc.camera_position}`);
  if (sc?.camera_movement) lines.push(`Motion: ${sc.camera_movement}`);
  if (sc?.lighting_state) lines.push(`Lighting: ${sc.lighting_state}`);
  if (sc?.background_elements) lines.push(`Background: ${sc.background_elements}`);
  if (at?.dialogue) lines.push(`VO: ${at.dialogue}`);
  const sync = at?.synchronized_actions;
  const syncLines: string[] = [];
  if (sync && typeof sync === 'object') {
    for (const [k, v] of Object.entries(sync)) {
      if (v) syncLines.push(`${k}: ${v}`);
    }
  }
  for (const s of syncLines) lines.push(s);
  let text = lines.filter(Boolean).join('\n').trim();
  if (!text) {
    text =
      'Cinematic premium product showcase, photoreal, smooth camera, shallow depth of field.';
  }
  const jewelryCtx = [
    productName,
    ch?.current_state,
    sc?.environment,
    sc?.background_elements,
    at?.dialogue,
    ...syncLines,
  ];
  if (textSuggestsJewelry(...jewelryCtx)) {
    text = `${text}\n\n${jewelryWearPlacementPromptBlock()}`;
  }
  if (text.length > 20000) text = text.slice(0, 20000);
  return text;
}

/** Max prompt length accepted by `/api/seedance/create` (matches backend). */
export const SEEDANCE_PROMPT_MAX_CHARS = 20000;

export type DirectSeedancePromptParams = {
  productName: string;
  description: string;
  price: string;
  targetAudience: string;
  aspectRatio: string;
  durationSeconds: number;
  conceptText: string;
  frameHints?: string[];
  /** When false, model should favor clean ambience over heavy VO. */
  generateAudio?: boolean;
};

/**
 * Parse grouped direct-concept strings from the backend:
 * `core idea. Angle: ... . Trigger: ...`
 */
export function parseDirectConceptLine(conceptText: string): {
  core: string;
  angle?: string;
  trigger?: string;
} {
  let rest = conceptText.trim();
  let trigger: string | undefined;
  const tri = rest.match(/\.\s*Trigger:\s*(.+)$/i);
  if (tri && tri.index !== undefined) {
    trigger = tri[1].trim();
    rest = rest.slice(0, tri.index).trim();
  }
  let core = rest;
  let angle: string | undefined;
  const ang = rest.match(/\.\s*Angle:\s*(.+)$/i);
  if (ang && ang.index !== undefined) {
    angle = ang[1].trim();
    core = rest.slice(0, ang.index).trim();
  }
  if (!core && (angle || trigger)) {
    core = [angle, trigger].filter(Boolean).join(' — ') || conceptText.trim();
  }
  return { core: core || conceptText.trim(), angle, trigger };
}

function _beatLabels(durationSeconds: number, hintCount: number): string[] {
  const d = Math.max(4, Math.min(15, Math.floor(durationSeconds)));
  if (hintCount <= 0) return [];
  if (hintCount === 1) return [`0–${d}s`];
  if (hintCount === 2) return [`0–${Math.round(d / 2)}s`, `${Math.round(d / 2)}–${d}s`];
  const out: string[] = [];
  for (let i = 0; i < hintCount; i++) {
    const start = Math.round((i * d) / hintCount);
    const end = i === hintCount - 1 ? d : Math.round(((i + 1) * d) / hintCount);
    out.push(`${start}–${end}s`);
  }
  return out;
}

/**
 * Structured Seedance prompt for single-clip “direct concept” ads.
 * De-duplicates angle/trigger when already present in `conceptText`, adds chronological beats, and trims safely.
 */
export function buildDirectSeedancePrompt(p: DirectSeedancePromptParams): string {
  const name = p.productName.trim();
  const ar = p.aspectRatio.trim() || '9:16';
  const dur = Math.max(4, Math.min(15, Math.floor(p.durationSeconds)));
  const parsed = parseDirectConceptLine(p.conceptText);
  const hints = (p.frameHints ?? []).map((h) => h.trim()).filter(Boolean).slice(0, 4);
  const labels = _beatLabels(dur, hints.length);

  const sections: string[] = [];

  sections.push(
    `[TASK] One continuous ${dur}s ${ar} photoreal product commercial for ${name ? `"${name}"` : 'this product'}. ` +
      'Single storyline with smooth transitions—avoid unrelated stock montage cuts.'
  );

  sections.push(`[CREATIVE] ${parsed.core}`);
  if (parsed.angle) sections.push(`[ANGLE] ${parsed.angle}`);
  if (parsed.trigger) sections.push(`[PSYCHOLOGY_TRIGGER] ${parsed.trigger}`);

  if (hints.length > 0) {
    const beats = hints.map((h, i) => `${labels[i]}: ${h}`).join('\n');
    sections.push(
      `[SHOT_BEATS — chronological, one flowing take]\n${beats}\n` +
        'Blend these beats without jarring jumps; keep the product readable in every beat.'
    );
  }

  const facts: string[] = [];
  const rawDesc = p.description.trim();
  const desc =
    rawDesc.length > 2800 ? `${rawDesc.slice(0, 2800).trim()}…` : rawDesc;
  if (desc) facts.push(`Description: ${desc}`);
  if (p.price.trim()) facts.push(`Price (optional supers / tone only): ${p.price.trim()}`);
  if (p.targetAudience.trim()) facts.push(`Audience / tone: ${p.targetAudience.trim()}`);
  if (facts.length) sections.push(`[PRODUCT_CONTEXT]\n${facts.join('\n')}`);

  const jewelryLike = textSuggestsJewelry(name, desc, parsed.core, p.conceptText, ...hints);

  sections.push(
    '[REFERENCE_IMAGES] Multiple angles may be provided—treat them as one SKU. ' +
      'Match silhouette, metal tone, stone layout, and proportions exactly; do not invent a different design.'
  );

  if (jewelryLike) {
    sections.push(jewelryWearPlacementPromptBlock());
  }

  sections.push(
    '[LOOK] Soft commercial key + gentle fill, natural skin where people appear, shallow depth when it helps legibility, ' +
      'smooth gimbal or slow dolly—no handheld shake unless the creative clearly asks for UGC.'
  );

  const negBase =
    'Extra fingers, warped hands, melting metal, duplicated bands, unreadable text walls, fake logos, harsh unrelated location jumps.';
  const negJewelry =
    'wrong-finger ring placement, floating or hovering jewelry, metal intersecting palm or ear, mirrored asymmetric design, novelty oversized prop scale on body.';
  sections.push(`[NEGATIVE] ${negBase}${jewelryLike ? ` ${negJewelry}` : ''}`);

  if (p.generateAudio !== false) {
    sections.push(
      '[AUDIO] Light tasteful ambience; optional short VO that supports the angle—avoid overpowering music unless the brief implies it.'
    );
  } else {
    sections.push('[AUDIO] No voiceover; subtle room tone or silence is fine.');
  }

  let text = sections.join('\n\n').trim();
  if (text.length > SEEDANCE_PROMPT_MAX_CHARS) {
    text = text.slice(0, SEEDANCE_PROMPT_MAX_CHARS);
  }
  return text;
}

export async function seedanceCreate(body: {
  prompt: string;
  reference_image_urls: string[];
  aspect_ratio: string;
  duration: number;
  resolution?: string;
  generate_audio?: boolean;
  /** KIE model, e.g. `bytedance/seedance-2` or `bytedance/seedance-2-fast`. */
  model?: string;
}): Promise<{ taskId: string }> {
  const res = await fetch(`${API_BASE}/api/seedance/create`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify(body),
  });
  if (!res.ok) throw new Error(await parseError(res, 'Seedance task failed'));
  return res.json();
}

export function createSeedanceEventSource(taskId: string): EventSource {
  return new EventSource(`${API_BASE}/api/seedance/events/${encodeURIComponent(taskId)}`);
}

export async function seedanceStatus(taskId: string): Promise<{
  state?: string;
  url?: string | null;
  failMsg?: string | null;
}> {
  const res = await fetch(`${API_BASE}/api/seedance/status/${encodeURIComponent(taskId)}`);
  if (!res.ok) throw new Error(await parseError(res, 'Seedance status check failed'));
  return res.json();
}

export function waitForSeedanceVideo(taskId: string, timeoutMs = 600000): Promise<string> {
  return new Promise((resolve, reject) => {
    let settled = false;
    const es = createSeedanceEventSource(taskId);
    let poller: number | null = null;
    const pollEveryMs = 10000;

    const settleSuccess = (url: string) => {
      if (settled) return;
      settled = true;
      if (poller !== null) window.clearInterval(poller);
      clearTimeout(t);
      es.close();
      resolve(url);
    };

    const settleFail = (msg?: string | null) => {
      if (settled) return;
      settled = true;
      if (poller !== null) window.clearInterval(poller);
      clearTimeout(t);
      es.close();
      reject(new Error(msg || 'Seedance generation failed'));
    };

    const inspect = (data: { state?: string; url?: string | null; failMsg?: string | null }) => {
      if (data.state === 'success' && data.url) {
        settleSuccess(data.url);
      } else if (data.state === 'fail') {
        settleFail(data.failMsg);
      }
    };

    const startFallbackPolling = () => {
      if (poller !== null || settled) return;
      poller = window.setInterval(async () => {
        if (settled) return;
        try {
          const data = await seedanceStatus(taskId);
          inspect(data);
        } catch {
          /* ignore transient poll errors; timeout handles terminal failure */
        }
      }, pollEveryMs);
    };

    // Fast path: handle already-finished tasks without waiting for callback/SSE.
    void seedanceStatus(taskId).then(inspect).catch(() => {
      /* ignore transient status errors; SSE path remains active */
    });

    const t = setTimeout(() => {
      if (settled) return;
      settled = true;
      if (poller !== null) window.clearInterval(poller);
      es.close();
      reject(new Error('Seedance generation timed out'));
    }, timeoutMs);
    es.onmessage = (ev) => {
      if (settled) return;
      try {
        const data = JSON.parse(ev.data) as {
          state?: string;
          url?: string | null;
          failMsg?: string | null;
        };
        inspect(data);
      } catch {
        /* ignore malformed SSE payloads */
      }
    };
    es.onerror = () => {
      // EventSource retries automatically; poll only as a degraded-path fallback.
      startFallbackPolling();
    };
  });
}

export async function klingGenerate(body: {
  prompt: string | object;
  imageUrls?: string[];
  model?: string;
  aspectRatio?: string;
  generationType?: string;
  seeds?: number;
  voiceType?: string;
  /** 4, 6, or 8 — forwarded to the API so the provider can honor shot length */
  durationSeconds?: number;
}): Promise<KlingGenerateResponse> {
  const res = await fetch(`${API_BASE}/api/veo/generate`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify(body),
  });
  if (!res.ok) throw new Error(await parseError(res, 'Video start failed'));
  return res.json();
}

export function createKlingEventSource(taskId: string): EventSource {
  return new EventSource(`${API_BASE}/api/veo/events/${taskId}`);
}

export async function klingStatus(taskId: string): Promise<{
  status?: string;
  url?: string | null;
  error?: string | null;
  message?: string | null;
}> {
  const res = await fetch(`${API_BASE}/api/veo/status/${encodeURIComponent(taskId)}`);
  if (!res.ok) throw new Error(await parseError(res, 'Video status check failed'));
  return res.json();
}

export function waitForKlingVideo(taskId: string, timeoutMs = 420000): Promise<string> {
  return new Promise((resolve, reject) => {
    let settled = false;
    const es = createKlingEventSource(taskId);
    let poller: number | null = null;
    const pollEveryMs = 10000;

    const settleSuccess = (url: string) => {
      if (settled) return;
      settled = true;
      if (poller !== null) window.clearInterval(poller);
      clearTimeout(t);
      es.close();
      resolve(url);
    };

    const settleFail = (msg?: string | null) => {
      if (settled) return;
      settled = true;
      if (poller !== null) window.clearInterval(poller);
      clearTimeout(t);
      es.close();
      reject(new Error(msg || 'Generation failed'));
    };

    const inspect = (data: {
      status?: string;
      url?: string | null;
      error?: string | null;
      message?: string | null;
    }) => {
      if (data.status === 'succeeded' && data.url) {
        settleSuccess(data.url);
      } else if (data.status === 'failed' || data.status === 'cancelled') {
        settleFail(data.error || data.message);
      }
    };

    const startFallbackPolling = () => {
      if (poller !== null || settled) return;
      poller = window.setInterval(async () => {
        if (settled) return;
        try {
          const data = await klingStatus(taskId);
          inspect(data);
        } catch {
          /* ignore transient poll errors; timeout handles terminal failure */
        }
      }, pollEveryMs);
    };

    // Fast path for already-finished tasks.
    void klingStatus(taskId).then(inspect).catch(() => {
      /* ignore transient status errors; SSE path remains active */
    });

    const t = setTimeout(() => {
      if (settled) return;
      settled = true;
      if (poller !== null) window.clearInterval(poller);
      es.close();
      reject(new Error('Video generation timed out'));
    }, timeoutMs);
    es.onmessage = (ev) => {
      if (settled) return;
      try {
        const data = JSON.parse(ev.data);
        inspect(data);
      } catch {
        /* ignore */
      }
    };
    es.onerror = () => {
      // EventSource retries automatically; poll only as a degraded-path fallback.
      startFallbackPolling();
    };
  });
}

export async function downloadVideo(
  url: string,
  opts?: { trimSeconds?: 4 | 6 | 8 }
): Promise<Blob> {
  const q = new URLSearchParams({ url });
  if (opts?.trimSeconds != null) q.set('trimSeconds', String(opts.trimSeconds));
  const res = await fetch(`${API_BASE}/api/veo/download?${q}`);
  if (!res.ok) throw new Error('Download failed');
  return res.blob();
}

function loadVideoFromFile(file: File): Promise<HTMLVideoElement> {
  return new Promise((resolve, reject) => {
    const v = document.createElement('video');
    v.preload = 'metadata';
    v.src = URL.createObjectURL(file);
    v.onloadedmetadata = () => resolve(v);
    v.onerror = () => {
      URL.revokeObjectURL(v.src);
      reject(new Error('Could not read video'));
    };
  });
}

export async function getVideoDuration(file: File): Promise<number> {
  const v = await loadVideoFromFile(file);
  try {
    return v.duration;
  } finally {
    URL.revokeObjectURL(v.src);
  }
}

export async function mergeVideos(blobs: Blob[], clips: ClipMetadata[]): Promise<Blob> {
  const fd = new FormData();
  fd.append('clips_data', JSON.stringify(clips));
  blobs.forEach((b, i) => fd.append('files', b, `clip_${i}.mp4`));
  const res = await fetch(`${API_BASE}/api/export/merge`, { method: 'POST', body: fd });
  if (!res.ok) throw new Error(await parseError(res, 'Merge failed'));
  return res.blob();
}

/**
 * Run async work on `items` with at most `concurrency` in flight. Results are in original order.
 * Use for I/O-bound pipelines (e.g. several segment renders) without unbounded provider load.
 */
export async function mapWithConcurrency<T, R>(
  items: T[],
  concurrency: number,
  mapper: (item: T, index: number) => Promise<R>,
  onProgress?: (completed: number, total: number) => void
): Promise<R[]> {
  const n = items.length;
  if (n === 0) return [];
  const cap = Math.max(1, Math.min(concurrency, n));
  const results: R[] = new Array(n);
  let next = 0;
  let finished = 0;

  async function worker(): Promise<void> {
    while (true) {
      const i = next++;
      if (i >= n) return;
      results[i] = await mapper(items[i], i);
      finished++;
      onProgress?.(finished, n);
    }
  }

  await Promise.all(Array.from({ length: cap }, () => worker()));
  return results;
}

/** Default parallel segment pipelines (GPT keyframe + Veo/Seedance). Reduce if providers rate-limit. */
export const SEGMENT_RENDER_CONCURRENCY = 3;

/** Build merge metadata for full-length clips in order. */
export async function clipsFromBlobs(blobs: Blob[]): Promise<ClipMetadata[]> {
  return Promise.all(
    blobs.map(async (b, i) => {
      const file = new File([b], `c${i}.mp4`, { type: 'video/mp4' });
      const dur = await getVideoDuration(file);
      return {
        index: i,
        startTime: 0,
        endTime: dur,
        type: 'video' as const,
      };
    })
  );
}

export async function generateSegmentFirstFrame(params: {
  segment: VeoSegment;
  referenceImageUrls: string[];
  aspectRatio: string;
  productName: string;
}): Promise<{ url: string; model: string; size: string }> {
  const candidateRefs = Array.from(
    new Set(
      params.referenceImageUrls
        .map((u) => (u || '').trim())
        .filter(Boolean)
    )
  ).slice(0, GPT_IMAGE_EDIT_MAX_REFS);

  const vettedRefs: string[] = [];
  for (const url of candidateRefs) {
    // Preflight only our hosted image URLs to avoid CORS false negatives on third-party CDNs.
    if (!url.includes('/api/images/')) {
      vettedRefs.push(url);
      continue;
    }
    try {
      const probe = await fetch(url, { method: 'GET' });
      if (probe.ok) vettedRefs.push(url);
    } catch {
      // Network/CORS error on probe: keep URL and let backend decide.
      vettedRefs.push(url);
    }
  }

  const referenceImageUrls = vettedRefs.length > 0 ? vettedRefs : candidateRefs;
  const res = await fetch(`${API_BASE}/api/showcase/segment-first-frame`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
      segment: params.segment,
      reference_image_urls: referenceImageUrls,
      aspect_ratio: params.aspectRatio,
      product_name: params.productName,
    }),
  });
  if (!res.ok) throw new Error(await parseError(res, 'GPT Image first frame failed'));
  return res.json();
}

export async function generateSegmentVideo(
  segment: VeoSegment,
  imageUrl: string,
  aspectRatio: string,
  seed: number,
  voiceType: string,
  opts: {
    model?: SegmentVideoModel;
    productName?: string;
    seedanceResolution?: '480p' | '720p' | '1080p';
    promptOverride?: string;
    referenceImageUrls?: string[];
  } = {}
): Promise<Blob> {
  const clipSec = segmentClipSeconds(segment);
  const model = opts.model ?? 'seedance-2-fast';

  if (isSeedanceSegmentModel(model)) {
    const prompt =
      opts.promptOverride?.trim() || segmentToSeedancePrompt(segment, opts.productName);
    const { taskId } = await seedanceCreate({
      prompt,
      reference_image_urls:
        opts.referenceImageUrls && opts.referenceImageUrls.length > 0
          ? opts.referenceImageUrls
          : [imageUrl],
      aspect_ratio: aspectRatio,
      duration: clipSec,
      resolution: opts.seedanceResolution ?? '480p',
      generate_audio: voiceType.trim().toLowerCase() !== 'none',
      model: kieSeedanceModelId(model),
    });
    const url = await waitForSeedanceVideo(taskId);
    return downloadVideo(url, { trimSeconds: clipSec });
  }

  const { taskId } = await klingGenerate({
    prompt: opts.promptOverride?.trim() || segment,
    imageUrls: [imageUrl],
    model: 'veo3_fast',
    aspectRatio,
    generationType: 'FIRST_AND_LAST_FRAMES_2_VIDEO',
    seeds: seed,
    voiceType,
    durationSeconds: clipSec,
  });
  const url = await waitForKlingVideo(taskId);
  return downloadVideo(url, { trimSeconds: clipSec });
}