import "server-only";

import type {
  PreparedStoryboardShot,
  StoryboardModelCandidate,
  StoryboardProgressEvent,
} from "@/lib/video-agent/types";

const sleep = (ms: number) => new Promise((resolve) => setTimeout(resolve, ms));

function normalizeErrorMessage(error: unknown) {
  if (!error) return "unknown_error";
  if (typeof error === "string") return error;
  if (error instanceof Error) return error.message || String(error);
  try {
    return JSON.stringify(error);
  } catch {
    return String(error);
  }
}

export type SequencerShotResult = {
  shotIndex: number;
  success: boolean;
  videoUrl?: string;
  modelId?: string;
  text?: string;
  error?: string;
};

export async function runVideoSequencerSkill(params: {
  provider: string;
  taskId: string;
  shots: PreparedStoryboardShot[];
  modelCandidates: StoryboardModelCandidate[];
  maxRetry: number;
  dispatchIntervalSec: number;
  enableFallback: boolean;
  onProgress?: (event: StoryboardProgressEvent) => void | Promise<void>;
  generateOneShot: (input: {
    shot: PreparedStoryboardShot;
    model: StoryboardModelCandidate;
  }) => Promise<{ videoUrl: string; text: string }>;
}): Promise<{
  results: SequencerShotResult[];
  successCount: number;
  failedCount: number;
}> {
  const {
    provider,
    taskId,
    shots,
    modelCandidates,
    maxRetry,
    dispatchIntervalSec,
    enableFallback,
    onProgress,
    generateOneShot,
  } = params;

  const candidateList =
    enableFallback && modelCandidates.length > 0
      ? modelCandidates
      : modelCandidates.slice(0, 1);

  const results: SequencerShotResult[] = [];

  for (let index = 0; index < shots.length; index += 1) {
    const shot = shots[index]!;
    let shotSuccess = false;
    let lastError = "";
    let resultText = "";
    let resultUrl = "";
    let usedModelId = "";

    for (const model of candidateList) {
      const retries = Math.max(0, Math.round(maxRetry));
      for (let attempt = 1; attempt <= retries + 1; attempt += 1) {
        try {
          const output = await generateOneShot({ shot, model });
          resultText = output.text;
          resultUrl = output.videoUrl;
          usedModelId = model.modelId;
          shotSuccess = true;
          break;
        } catch (error) {
          lastError = normalizeErrorMessage(error);
          if (attempt <= retries) {
            await onProgress?.({
              stage: "shot_retry",
              provider,
              taskId,
              shotIndex: shot.shotIndex,
              attempt,
              modelId: model.modelId,
              error: lastError,
            });
            const backoffSec = Math.min(40, Math.pow(2, attempt - 1) * 10);
            await sleep(backoffSec * 1000);
          }
        }
      }

      if (shotSuccess) {
        break;
      }
    }

    if (shotSuccess) {
      results.push({
        shotIndex: shot.shotIndex,
        success: true,
        modelId: usedModelId,
        videoUrl: resultUrl,
        text: resultText,
      });
      await onProgress?.({
        stage: "shot_completed",
        provider,
        taskId,
        shotIndex: shot.shotIndex,
        modelId: usedModelId,
        videoUrl: resultUrl,
        text: resultText,
      });
    } else {
      results.push({
        shotIndex: shot.shotIndex,
        success: false,
        error: lastError || "video_generation_failed",
      });
      await onProgress?.({
        stage: "shot_failed",
        provider,
        taskId,
        shotIndex: shot.shotIndex,
        error: lastError || "video_generation_failed",
      });
    }

    if (index < shots.length - 1 && dispatchIntervalSec > 0) {
      await sleep(Math.round(dispatchIntervalSec * 1000));
    }
  }

  const successCount = results.filter((item) => item.success).length;
  const failedCount = results.length - successCount;
  return { results, successCount, failedCount };
}