import "server-only";

import type {
  MappedStoryboardShot,
  StoryboardTile,
  NormalizedStoryboardScript,
} from "@/lib/video-agent/types";

function clampIndex(value: number, length: number) {
  if (length <= 0) return 0;
  const rounded = Math.max(1, Math.round(value));
  return Math.min(length, rounded) - 1;
}

function buildShotPrompt(params: {
  style: string;
  action: string;
  camera: string;
  mood: string;
  language: "zh" | "en" | "mixed";
}) {
  const { style, action, camera, mood, language } = params;
  if (language === "en") {
    return [
      "Animate this still image into a coherent short scene.",
      `Action: ${action}.`,
      `Camera: ${camera}.`,
      `Mood: ${mood}.`,
      `Style: ${style}.`,
      "Keep identity and key structure stable.",
    ].join(" ");
  }

  return [
    "请基于当前输入图片生成连贯的视频镜头。",
    `动作：${action}。`,
    `镜头：${camera}。`,
    `氛围：${mood}。`,
    `风格：${style}。`,
    "保持主体身份、构图和关键细节稳定。",
  ].join("");
}

export function runStoryboardMapperSkill(params: {
  script: NormalizedStoryboardScript;
  tiles: StoryboardTile[];
}): MappedStoryboardShot[] {
  const { script, tiles } = params;
  if (!tiles.length) return [];

  const usedTileIndexes = new Set<number>();
  const nextAvailableTile = (startIndex = 1) => {
    for (let index = Math.max(1, startIndex); index <= tiles.length; index += 1) {
      if (!usedTileIndexes.has(index)) return index;
    }
    for (let index = 1; index <= tiles.length; index += 1) {
      if (!usedTileIndexes.has(index)) return index;
    }
    return Math.max(1, Math.min(tiles.length, startIndex));
  };

  return script.shots.map((shot, index) => {
    const preferredTileIndex =
      shot.preferredTileIndex && shot.preferredTileIndex >= 1 && shot.preferredTileIndex <= tiles.length
        ? shot.preferredTileIndex
        : shot.index || index + 1;
    const pickedTileIndex = usedTileIndexes.has(preferredTileIndex)
      ? nextAvailableTile(index + 1)
      : preferredTileIndex;
    usedTileIndexes.add(pickedTileIndex);
    const tile =
      tiles[clampIndex(pickedTileIndex, tiles.length)] || tiles[index] || tiles[0];
    const prompt = buildShotPrompt({
      style: script.globalStyle,
      action: shot.action,
      camera: shot.camera,
      mood: shot.mood,
      language: script.language,
    });

    return {
      shotIndex: shot.index,
      tileIndex: tile.index,
      tileImageUrl: tile.imageUrl,
      durationSec: shot.durationSec,
      prompt,
      negativePrompt: shot.negativePrompt,
      action: shot.action,
      camera: shot.camera,
      mood: shot.mood,
    };
  });
}