const ORDINAL_REFERENCE_PATTERNS = [
  /(?:第一|第\s*1|图片\s*(?:1|一)|照片\s*(?:1|一)|图\s*(?:1|一)|first\s+(?:image|photo|reference)|1st\s+(?:image|photo|reference))[\s\S]{0,120}(?:第二|第\s*(?:2|二|两)|图片\s*(?:2|二|两)|照片\s*(?:2|二|两)|图\s*(?:2|二|两)|second\s+(?:image|photo|reference)|2nd\s+(?:image|photo|reference))/i,
  /(?:第二|第\s*(?:2|二|两)|图片\s*(?:2|二|两)|照片\s*(?:2|二|两)|图\s*(?:2|二|两)|second\s+(?:image|photo|reference)|2nd\s+(?:image|photo|reference))[\s\S]{0,120}(?:第一|第\s*1|图片\s*(?:1|一)|照片\s*(?:1|一)|图\s*(?:1|一)|first\s+(?:image|photo|reference)|1st\s+(?:image|photo|reference))/i,
  /(?:第三|第\s*(?:3|三)|图片\s*(?:3|三)|照片\s*(?:3|三)|图\s*(?:3|三)|third\s+(?:image|photo|reference)|3rd\s+(?:image|photo|reference))/i,
  /(?:第四|第\s*(?:4|四)|图片\s*(?:4|四)|照片\s*(?:4|四)|图\s*(?:4|四)|fourth\s+(?:image|photo|reference)|4th\s+(?:image|photo|reference))/i,
];

const MULTI_IMAGE_REFERENCE_PATTERNS = [
  ...ORDINAL_REFERENCE_PATTERNS,
  /(?:左图|右图|上图|下图|左侧图|右侧图|左边的图|右边的图|左侧图片|右侧图片)/i,
  /(?:这|这些|这几|上述|以上|下面|上传|给的|参考|选中|画布|原图|素材)[\s\S]{0,18}(?:两|俩|二|三|四|五|六|七|八|2|3|4|5|6|7|8|多|几)[\s\S]{0,12}(?:张|个)?(?:图|图片|照片|参考图|素材)/i,
  /(?:两|俩|二|三|四|五|六|七|八|2|3|4|5|6|7|8|多|几)[\s\S]{0,8}(?:张|个)?(?:参考图|素材图|输入图|源图|上传图|原图)/i,
  /(?:两|俩|二|三|四|五|六|七|八|2|3|4|5|6|7|8|多|几)[\s\S]{0,8}(?:张|个)?(?:图|图片|照片)[\s\S]{0,28}(?:合成|融合|拼接|对比|混合|组合|参考|编辑|处理|改)/i,
  /(?:合成|融合|拼接|对比|混合|组合|参考|编辑|增加|添加|放入|换成)[\s\S]{0,28}(?:两|俩|二|三|四|五|六|七|八|2|3|4|5|6|7|8|多|几|第二|第三|第四|图片\s*(?:2|3|4|二|三|四)|照片\s*(?:2|3|4|二|三|四)|图\s*(?:2|3|4|二|三|四))[\s\S]{0,12}(?:图|图片|照片|参考|素材)?/i,
  /(?:multi|multiple|two|several|many)[\s\S]{0,20}(?:reference|input|source)[\s\S]{0,16}(?:image|photo)s?/i,
  /(?:reference|use|combine|merge|blend|edit)[\s\S]{0,24}(?:first|1st)[\s\S]{0,80}(?:second|2nd)[\s\S]{0,32}(?:image|photo|reference)?/i,
];

const REQUESTED_COUNT_PATTERNS: Array<{ count: number; pattern: RegExp }> = [
  {
    count: 8,
    pattern: /(?:第\s*(?:八|8)\s*(?:张|个)?(?:图|图片|照片)|(?:图片|照片|图|image)\s*(?:8|八)\b|(?:八|8)\s*(?:张|个)?(?:参考图|素材图|输入图|源图|上传图|原图))/i,
  },
  {
    count: 7,
    pattern: /(?:第\s*(?:七|7)\s*(?:张|个)?(?:图|图片|照片)|(?:图片|照片|图|image)\s*(?:7|七)\b|(?:七|7)\s*(?:张|个)?(?:参考图|素材图|输入图|源图|上传图|原图))/i,
  },
  {
    count: 6,
    pattern: /(?:第\s*(?:六|6)\s*(?:张|个)?(?:图|图片|照片)|(?:图片|照片|图|image)\s*(?:6|六)\b|(?:六|6)\s*(?:张|个)?(?:参考图|素材图|输入图|源图|上传图|原图))/i,
  },
  {
    count: 5,
    pattern: /(?:第\s*(?:五|5)\s*(?:张|个)?(?:图|图片|照片)|(?:图片|照片|图|image)\s*(?:5|五)\b|(?:五|5)\s*(?:张|个)?(?:参考图|素材图|输入图|源图|上传图|原图))/i,
  },
  {
    count: 4,
    pattern: /(?:第\s*(?:四|4)\s*(?:张|个)?(?:图|图片|照片)|(?:图片|照片|图|image)\s*(?:4|四)\b|(?:四|4)\s*(?:张|个)?(?:图|图片|照片|参考图|素材图|输入图|源图|上传图|原图))/i,
  },
  {
    count: 3,
    pattern: /(?:第\s*(?:三|3)\s*(?:张|个)?(?:图|图片|照片)|(?:图片|照片|图|image)\s*(?:3|三)\b|(?:三|3)\s*(?:张|个)?(?:图|图片|照片|参考图|素材图|输入图|源图|上传图|原图))/i,
  },
  {
    count: 2,
    pattern: /(?:第\s*(?:二|两|2)\s*(?:张|个)?(?:图|图片|照片)|(?:图片|照片|图|image)\s*(?:2|二|两)\b|(?:两|俩|二|2)\s*(?:张|个)?(?:图|图片|照片|参考图|素材图|输入图|源图|上传图|原图))/i,
  },
];

function normalizeText(text: string) {
  return String(text || "").replace(/\s+/g, " ").trim();
}

function normalizeItemId(value: string | null | undefined) {
  return String(value || "").trim();
}

function clampMaxItems(value: number | undefined) {
  return Math.max(1, Math.min(8, Math.round(value || 4)));
}

function dedupeItemsById<T>(
  items: T[],
  getItemId: (item: T) => string | null | undefined,
) {
  const seen = new Set<string>();
  const result: T[] = [];

  for (const item of items) {
    const id = normalizeItemId(getItemId(item));
    if (!id || seen.has(id)) continue;
    seen.add(id);
    result.push(item);
  }

  return result;
}

function getItemIdSet<T>(
  items: T[],
  getItemId: (item: T) => string | null | undefined,
) {
  return new Set(
    items
      .map((item) => normalizeItemId(getItemId(item)))
      .filter(Boolean),
  );
}

function appendMissingItems<T>(params: {
  result: T[];
  candidates: T[];
  targetCount: number;
  getItemId: (item: T) => string | null | undefined;
}) {
  const seen = getItemIdSet(params.result, params.getItemId);
  for (const item of params.candidates) {
    if (params.result.length >= params.targetCount) break;
    const id = normalizeItemId(params.getItemId(item));
    if (!id || seen.has(id)) continue;
    seen.add(id);
    params.result.push(item);
  }
}

function getCandidateWindow<T>(params: {
  candidates: T[];
  selectedIds: Set<string>;
  targetCount: number;
  getItemId: (item: T) => string | null | undefined;
}) {
  if (params.candidates.length === 0) return [];
  if (params.selectedIds.size === 0) {
    return params.candidates.slice(-params.targetCount);
  }

  let selectedIndex = -1;
  params.candidates.forEach((item, index) => {
    const id = normalizeItemId(params.getItemId(item));
    if (id && params.selectedIds.has(id)) {
      selectedIndex = index;
    }
  });

  if (selectedIndex < 0) return params.candidates.slice(-params.targetCount);

  const start = Math.max(0, selectedIndex - params.targetCount + 1);
  const windowItems = params.candidates.slice(start, selectedIndex + 1);
  if (windowItems.length >= params.targetCount) return windowItems;

  return [
    ...windowItems,
    ...params.candidates.slice(
      selectedIndex + 1,
      selectedIndex + 1 + (params.targetCount - windowItems.length),
    ),
  ];
}

export function hasMultiImageReferenceIntent(text: string) {
  const normalized = normalizeText(text);
  if (!normalized) return false;
  return MULTI_IMAGE_REFERENCE_PATTERNS.some((pattern) => pattern.test(normalized));
}

export function getRequestedImageReferenceCount(text: string) {
  const normalized = normalizeText(text);
  if (!normalized) return 0;
  if (!hasMultiImageReferenceIntent(normalized)) return 0;
  if (/(?:多图|多张|多份|multiple|several|many)/i.test(normalized)) return 4;

  for (const item of REQUESTED_COUNT_PATTERNS) {
    if (item.pattern.test(normalized)) return item.count;
  }

  return 2;
}

export function resolveMultiImageReferenceContext<T>(params: {
  text: string;
  selectedItems: T[];
  candidateItems: T[];
  getItemId: (item: T) => string | null | undefined;
  maxItems?: number;
}) {
  const maxItems = clampMaxItems(params.maxItems);
  const selectedItems = dedupeItemsById(params.selectedItems || [], params.getItemId).slice(
    0,
    maxItems,
  );
  if (!hasMultiImageReferenceIntent(params.text)) return selectedItems;

  const candidateItems = dedupeItemsById(params.candidateItems || [], params.getItemId);
  const requestedCount = Math.min(
    maxItems,
    Math.max(2, selectedItems.length, getRequestedImageReferenceCount(params.text)),
  );

  if (selectedItems.length >= requestedCount) {
    return selectedItems.slice(0, maxItems);
  }

  const selectedIds = getItemIdSet(selectedItems, params.getItemId);
  const candidateWindow = getCandidateWindow({
    candidates: candidateItems,
    selectedIds,
    targetCount: requestedCount,
    getItemId: params.getItemId,
  });

  if (selectedItems.length >= 2) {
    const result = selectedItems.slice(0, requestedCount);
    appendMissingItems({
      result,
      candidates: candidateWindow,
      targetCount: requestedCount,
      getItemId: params.getItemId,
    });
    appendMissingItems({
      result,
      candidates: candidateItems,
      targetCount: requestedCount,
      getItemId: params.getItemId,
    });
    return result.slice(0, maxItems);
  }

  const result = candidateWindow.slice(0, requestedCount);
  appendMissingItems({
    result,
    candidates: selectedItems,
    targetCount: requestedCount,
    getItemId: params.getItemId,
  });
  appendMissingItems({
    result,
    candidates: candidateItems,
    targetCount: requestedCount,
    getItemId: params.getItemId,
  });
  return result.slice(0, maxItems);
}