const fs = require('fs');
const path = require('path');
const { CONFIG } = require('../config');

const ENV_PATH = process.env.ENV_FILE
  ? path.resolve(process.env.ENV_FILE)
  : path.resolve(process.cwd(), '.env');

/**
 * Read the current .env file and parse into a key->value Map.
 */
function readEnvFile() {
  if (!fs.existsSync(ENV_PATH)) return new Map();
  const lines = fs.readFileSync(ENV_PATH, 'utf8').split('\n');
  const map = new Map();
  for (const line of lines) {
    const trimmed = line.trim();
    if (!trimmed || trimmed.startsWith('#')) continue;
    const idx = line.indexOf('=');
    if (idx === -1) continue;
    const key = line.slice(0, idx).trim();
    const value = line.slice(idx + 1).trim();
    map.set(key, value);
  }
  return map;
}

/**
 * Write a Map of key->value back to the .env file,
 * preserving comments and blank lines.
 */
function writeEnvFile(updates) {
  if (!fs.existsSync(ENV_PATH)) {
    const lines = [];
    for (const [k, v] of updates) lines.push(`${k}=${v}`);
    fs.writeFileSync(ENV_PATH, lines.join('\n') + '\n', 'utf8');
    return;
  }

  const raw = fs.readFileSync(ENV_PATH, 'utf8');
  const lines = raw.split('\n');
  const written = new Set();

  const result = lines.map(line => {
    const trimmed = line.trim();
    if (!trimmed || trimmed.startsWith('#')) return line;
    const idx = line.indexOf('=');
    if (idx === -1) return line;
    const key = line.slice(0, idx).trim();
    if (updates.has(key)) {
      written.add(key);
      return `${key}=${updates.get(key)}`;
    }
    return line;
  });

  // Append any new keys not already in the file
  for (const [k, v] of updates) {
    if (!written.has(k)) result.push(`${k}=${v}`);
  }

  fs.writeFileSync(ENV_PATH, result.join('\n'), 'utf8');
}

/**
 * Apply a flat object of { KEY: value } to both CONFIG and .env.
 * Returns { applied: string[], errors: string[] }
 */
function applyConfigUpdates(updates) {
  const applied = [];
  const errors = [];

  for (const [key, rawValue] of Object.entries(updates)) {
    try {
      if (rawValue === 'true' || rawValue === 'false') {
        CONFIG[key] = rawValue === 'true';
      } else if (!isNaN(rawValue) && rawValue !== '') {
        CONFIG[key] = Number(rawValue);
      } else {
        CONFIG[key] = rawValue;
      }
      applied.push(key);
    } catch (err) {
      errors.push(`${key}: ${err.message}`);
    }
  }

  // Write to .env
  const envMap = readEnvFile();
  for (const [key, value] of Object.entries(updates)) {
    envMap.set(key, String(value));
  }
  writeEnvFile(envMap);

  return { applied, errors };
}

/**
 * Read all current env values for the settings UI.
 */
function readAllConfig() {
  return readEnvFile();
}

module.exports = { applyConfigUpdates, readAllConfig, readEnvFile, writeEnvFile };