const fs = require('fs');
const path = require('path');

function parseHSQLDB(dbDir) {
  const scriptPath = path.join(dbDir, 'database.script');
  const dataPath = path.join(dbDir, 'database.data');

  if (!fs.existsSync(scriptPath) || !fs.existsSync(dataPath)) {
    throw new Error('Missing HSQLDB files (database.script or database.data)');
  }

  const dataBuffer = fs.readFileSync(dataPath);
  const script = fs.readFileSync(scriptPath, 'utf-8');

  // Parse table structure from script
  const entryTableMatch = script.match(
    /CREATE CACHED TABLE (ENTRY_TABLE_\d+)\((.*?)\)/
  );
  if (!entryTableMatch) throw new Error('Could not find ENTRY_TABLE in script');

  const tableName = entryTableMatch[1];
  const tableDefStr = entryTableMatch[2];
  const columns = tableDefStr
    .split(',')
    .map(col => col.trim().split(/\s+/)[0]);

  // Parse INDEX line (note: no space between INDEX and ')
  const indexMatch = script.match(
    new RegExp(`SET TABLE ${tableName} INDEX'(.*?)'`)
  );
  if (!indexMatch) throw new Error('Could not find INDEX for ENTRY_TABLE');

  const [pageIndex, rowCount] = indexMatch[1].split(' ').map(Number);

  // HSQLDB binary format parsing (simplified for common structure)
  // This is a basic extraction—HSQLDB uses a specific binary format
  const entries = [];
  const entries_raw = extractEntriesFromBinary(dataBuffer, pageIndex, rowCount);

  for (const raw of entries_raw) {
    if (raw && raw.length >= columns.length) {
      const entry = {};
      columns.forEach((col, idx) => {
        entry[col] = raw[idx];
      });
      entries.push(entry);
    }
  }

  return entries;
}

function extractEntriesFromBinary(buffer, pageIndex, rowCount) {
  // HSQLDB stores data in a binary format with page offsets
  // This is a simplified extraction—looking for text patterns in the binary data
  const entries = [];
  const textDecoder = new TextDecoder('utf-8', { ignoreBOM: true });

  // Convert buffer to text, extract null-terminated strings
  const bufStr = textDecoder.decode(buffer);
  const nullSeparated = bufStr.split('\0');

  // Group entries by looking for patterns (ID, timestamp, title, categories, entry, draft, modified, author)
  let currentEntry = [];
  for (const part of nullSeparated) {
    if (part.trim()) {
      currentEntry.push(part.trim());
      // Rough heuristic: HSQLDB entries typically have ~8 fields
      if (currentEntry.length === 8) {
        entries.push([...currentEntry]);
        currentEntry = [];
      }
    }
  }

  return entries;
}

module.exports = { parseHSQLDB };