import { WENFAN_HELP_ARTICLES, type HelpArticle } from './wenfan-help-articles';

export type HelpSearchResult = {
  article: HelpArticle;
  score: number;
  matchedKeywords: string[];
  relatedArticles: HelpArticle[];
};

const MIN_RESULT_SCORE = 15;

const FALLBACK_SUGGESTIONS = [
  '怎么新建产品？',
  '怎么把需求纳入版本？',
  '开发任务怎么提测？',
  '测试用例失败后怎么提 Bug？',
  'AI 拆解在哪里使用？',
  '日志记录会记录哪些行为？',
];

export function normalizeHelpQuery(input: string): string {
  return input
    .toLowerCase()
    .replace(/[，。！？、,.!?;；:："'“”‘’（）()【】[\]{}<>《》\s]/g, '')
    .trim();
}

function isSubsequence(needle: string, haystack: string): boolean {
  if (needle.length < 4) return false;

  let index = 0;
  for (const char of haystack) {
    if (char === needle[index]) index += 1;
    if (index === needle.length) return true;
  }
  return false;
}

function scoreText(query: string, text: string, exactScore: number, fuzzyScore: number): number {
  const normalized = normalizeHelpQuery(text);
  if (!normalized) return 0;
  if (normalized.includes(query) || query.includes(normalized)) return exactScore;
  if (isSubsequence(normalized, query) || isSubsequence(query, normalized)) return fuzzyScore;
  return 0;
}

function resolveRelatedArticles(article: HelpArticle, articles: HelpArticle[]): HelpArticle[] {
  return article.relatedIds
    .map((id) => articles.find((item) => item.id === id))
    .filter((item): item is HelpArticle => Boolean(item));
}

export function searchHelpArticles(
  query: string,
  articles: HelpArticle[] = WENFAN_HELP_ARTICLES,
): HelpSearchResult[] {
  const normalizedQuery = normalizeHelpQuery(query);
  if (normalizedQuery.length < 2) return [];

  return articles
    .map((article) => {
      let score = 0;
      const matchedKeywords: string[] = [];

      score += scoreText(normalizedQuery, article.title, 20, 10);
      score += scoreText(normalizedQuery, article.category, 12, 0);

      for (const keyword of article.keywords) {
        const keywordScore = scoreText(normalizedQuery, keyword, 10, 6);
        if (keywordScore > 0) {
          score += keywordScore;
          matchedKeywords.push(keyword);
        }
      }

      const secondaryTexts = [
        article.scenario,
        article.entry,
        ...article.steps,
        ...article.requiredFields,
        ...article.statusFlow,
        ...article.notes,
      ];

      for (const text of secondaryTexts) {
        score += scoreText(normalizedQuery, text, 3, 1);
      }

      return {
        article,
        score,
        matchedKeywords,
        relatedArticles: resolveRelatedArticles(article, articles),
      };
    })
    .filter((result) => result.score >= MIN_RESULT_SCORE)
    .sort((a, b) => {
      if (b.score !== a.score) return b.score - a.score;
      return a.article.title.localeCompare(b.article.title, 'zh-CN');
    });
}

export function getFallbackHelpSuggestions(): string[] {
  return FALLBACK_SUGGESTIONS;
}

export function getFallbackHelpMessage(showGenericSuggestions: boolean): string {
  if (showGenericSuggestions) {
    return '暂时没有找到对应的内置帮助内容。你可以换个关键词，或者从下面这些常见问题开始。';
  }
  return '暂时没有找到对应的内置帮助内容。你可以换个更具体的系统关键词，或继续描述你要操作的模块。';
}

export function shouldShowGenericHelpSuggestions(userQuestionCount: number): boolean {
  return userQuestionCount < 2;
}