import fs from "fs-extra";
import path from "path";
import matter from "gray-matter";

let documentCache = null;

function levenshteinDistance(str1, str2) {
  const m = str1.length;
  const n = str2.length;
  const dp = Array(m + 1)
    .fill(0)
    .map(() => Array(n + 1).fill(0));

  for (let i = 0; i <= m; i++) dp[i][0] = i;
  for (let j = 0; j <= n; j++) dp[0][j] = j;

  for (let i = 1; i <= m; i++) {
    for (let j = 1; j <= n; j++) {
      if (str1[i - 1] === str2[j - 1]) {
        dp[i][j] = dp[i - 1][j - 1];
      } else {
        dp[i][j] = 1 + Math.min(dp[i - 1][j], dp[i][j - 1], dp[i - 1][j - 1]);
      }
    }
  }

  return dp[m][n];
}

export function calculateStringSimilarity(str1, str2) {
  if (!str1 || !str2) return 0;
  const maxLen = Math.max(str1.length, str2.length);
  if (maxLen === 0) return 1;
  const distance = levenshteinDistance(str1, str2);
  return 1 - distance / maxLen;
}

export async function loadContextTreeDocuments(dataDir = "/data") {
  if (documentCache !== null) return documentCache;

  const docs = [];
  const contextTreePath = path.join(dataDir, "context-tree");

  try {
    if (!fs.existsSync(contextTreePath)) {
      documentCache = [];
      return [];
    }

    const topics = fs.readdirSync(contextTreePath);

    for (const topic of topics) {
      const topicPath = path.join(contextTreePath, topic);
      const stat = fs.statSync(topicPath);

      if (!stat.isDirectory()) continue;

      const files = fs.readdirSync(topicPath);

      for (const file of files) {
        if (!file.endsWith(".md")) continue;

        const filePath = path.join(topicPath, file);
        const content = fs.readFileSync(filePath, "utf8");
        const { data, content: body } = matter(content);

        docs.push({
          id: data.id || file.replace(".md", ""),
          title: data.title || "Untitled",
          topic: data.topic || topic,
          type: data.type || "context",
          text: `${data.title || ""} ${body}`.trim(),
          importance: data.importance || 5,
          metadata: data,
          filePath,
        });
      }
    }

    documentCache = docs;
    return docs;
  } catch (error) {
    console.error("Error loading context-tree documents:", error.message);
    documentCache = [];
    return [];
  }
}

export function mergeSearchResults(vectorResults, fuzzyResults, nResults = 5) {
  const merged = new Map();

  if (vectorResults && vectorResults.ids && vectorResults.ids[0]) {
    vectorResults.ids[0].forEach((id, idx) => {
      if (!merged.has(id)) {
        const distance = vectorResults.distances?.[0]?.[idx] || 0;
        const similarity = 1 / (1 + distance);
        merged.set(id, {
          id,
          document: vectorResults.documents?.[0]?.[idx] || "",
          metadata: vectorResults.metadatas?.[0]?.[idx] || {},
          vectorScore: similarity,
          fuzzyScore: 0,
          importanceBonus: 1,
        });
      }
    });
  }

  if (fuzzyResults && Array.isArray(fuzzyResults)) {
    fuzzyResults.forEach((doc) => {
      const importanceBonus = (doc.importance || 5) / 10;
      if (merged.has(doc.id)) {
        const existing = merged.get(doc.id);
        existing.fuzzyScore = Math.max(existing.fuzzyScore, doc.score || 0);
        existing.importanceBonus = importanceBonus;
      } else {
        merged.set(doc.id, {
          id: doc.id,
          document: doc.text || "",
          metadata: doc.metadata || {},
          vectorScore: 0,
          fuzzyScore: doc.score || 0,
          importanceBonus,
        });
      }
    });
  }

  const results = Array.from(merged.values()).map((item) => ({
    ...item,
    combinedScore:
      item.vectorScore * 0.5 +
      item.fuzzyScore * 0.3 +
      item.importanceBonus * 0.2,
  }));

  results.sort((a, b) => b.combinedScore - a.combinedScore);

  return {
    ids: [results.slice(0, nResults).map((r) => r.id)],
    documents: [results.slice(0, nResults).map((r) => r.document)],
    metadatas: [results.slice(0, nResults).map((r) => r.metadata)],
    distances: [results.slice(0, nResults).map((r) => 1 - r.combinedScore)],
  };
}

export function clearDocumentCache() {
  documentCache = null;
}