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

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

/**
 * Serialize a runtime value for .env storage.
 *
 * Default container: backticks. Under dotenv v17, backtick-wrapped values are
 * preserved verbatim (literal newlines and inner quotes/backslashes all round-trip
 * without escape processing), which is the only container that survives quotes
 * AND newlines cleanly. Double-quoted values only decode `\n` / `\r`; `\"` and
 * `\\` stay literal, so quoted-with-escapes doesn't round-trip.
 *
 * Fallback for values that themselves contain a backtick (vanishingly rare in
 * env-style config): double-quote with escape-encoded `\\`, `\"`, `\n`, `\r`,
 * `\t`. Caveat — CONFIG will receive the still-escaped `\"` / `\\` after boot
 * because dotenv v17 won't reverse those. Flagged in the key-count verification
 * at the bottom of writeEnvFile; the combination is unreachable via the UI.
 */
function encodeEnvValue(v) {
  const s = String(v == null ? '' : v);
  if (!s.includes('`')) return '`' + s + '`';
  const escaped = s
    .replace(/\\/g, '\\\\')
    .replace(/"/g, '\\"')
    .replace(/\n/g, '\\n')
    .replace(/\r/g, '\\r')
    .replace(/\t/g, '\\t');
  return `"${escaped}"`;
}

/**
 * Decode a raw .env value. Backtick and double-quote containers supported;
 * unquoted values pass through (hand-edited .env back-compat).
 */
function decodeEnvValue(raw) {
  if (raw.length >= 2 && raw.startsWith('`') && raw.endsWith('`')) {
    return raw.slice(1, -1);
  }
  if (raw.length >= 2 && raw.startsWith('"') && raw.endsWith('"')) {
    const inner = raw.slice(1, -1);
    let out = '';
    for (let i = 0; i < inner.length; i++) {
      if (inner[i] === '\\' && i + 1 < inner.length) {
        const next = inner[i + 1];
        if (next === 'n') out += '\n';
        else if (next === 'r') out += '\r';
        else if (next === 't') out += '\t';
        else if (next === '"') out += '"';
        else if (next === '\\') out += '\\';
        else out += inner[i] + next;
        i++;
      } else {
        out += inner[i];
      }
    }
    return out;
  }
  return raw;
}

/**
 * Read the current .env file and parse into a key->value Map.
 * Backtick-wrapped values may span multiple physical lines (dotenv behavior);
 * this reader joins continuation lines until the closing backtick is found.
 * Double-quoted values are decoded (`\n`/`\r` escapes processed);
 * unquoted values pass through.
 */
function readEnvFile() {
  if (!fs.existsSync(ENV_PATH)) return new Map();
  const lines = fs.readFileSync(ENV_PATH, 'utf8').split('\n');
  const map = new Map();
  for (let i = 0; i < lines.length; i++) {
    const line = lines[i];
    const trimmed = line.trim();
    if (!trimmed || trimmed.startsWith('#')) continue;
    const idx = line.indexOf('=');
    if (idx === -1) continue;
    const key = line.slice(0, idx).trim();
    let value = line.slice(idx + 1);
    if (value.trimStart().startsWith('`')) {
      let btCount = (value.match(/`/g) || []).length;
      while (btCount < 2 && i + 1 < lines.length) {
        i++;
        value += '\n' + lines[i];
        btCount = (value.match(/`/g) || []).length;
      }
    }
    map.set(key, decodeEnvValue(value.trim()));
  }
  return map;
}

/**
 * Write a Map of key->value back to the .env file,
 * preserving comments and blank lines. Values are encoded via encodeEnvValue.
 *
 * After write, re-reads the file and throws if the key count doesn't match the
 * expected count — catches truncation or corrupted-quote escaping.
 */
function writeEnvFile(updates) {
  const expected = updates.size;

  if (!fs.existsSync(ENV_PATH)) {
    const lines = [];
    for (const [k, v] of updates) lines.push(`${k}=${encodeEnvValue(v)}`);
    fs.writeFileSync(ENV_PATH, lines.join('\n') + '\n', 'utf8');
  } else {
    const raw = fs.readFileSync(ENV_PATH, 'utf8');
    const lines = raw.split('\n');
    const written = new Set();
    const result = [];

    for (let i = 0; i < lines.length; i++) {
      const line = lines[i];
      const trimmed = line.trim();
      if (!trimmed || trimmed.startsWith('#')) { result.push(line); continue; }
      const idx = line.indexOf('=');
      if (idx === -1) { result.push(line); continue; }
      const key = line.slice(0, idx).trim();

      const spanStart = i;
      let valueSoFar = line.slice(idx + 1);
      if (valueSoFar.trimStart().startsWith('`')) {
        let btCount = (valueSoFar.match(/`/g) || []).length;
        while (btCount < 2 && i + 1 < lines.length) {
          i++;
          valueSoFar += '\n' + lines[i];
          btCount = (valueSoFar.match(/`/g) || []).length;
        }
      }

      if (updates.has(key)) {
        written.add(key);
        result.push(`${key}=${encodeEnvValue(updates.get(key))}`);
      } else {
        for (let j = spanStart; j <= i; j++) result.push(lines[j]);
      }
    }

    for (const [k, v] of updates) {
      if (!written.has(k)) result.push(`${k}=${encodeEnvValue(v)}`);
    }

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

  const roundtrip = readEnvFile();
  if (roundtrip.size !== expected) {
    const expectedKeys = new Set(updates.keys());
    const actualKeys = new Set(roundtrip.keys());
    const missing = [...expectedKeys].filter(k => !actualKeys.has(k));
    const extra = [...actualKeys].filter(k => !expectedKeys.has(k));
    throw new Error(
      `writeEnvFile: key count mismatch after write ` +
      `(expected ${expected}, got ${roundtrip.size})` +
      (missing.length ? `. Missing: [${missing.join(', ')}]` : '') +
      (extra.length ? `. Extra: [${extra.join(', ')}]` : '')
    );
  }
}

/**
 * Apply a flat object of { KEY: value } to both CONFIG and .env.
 * Returns { applied: string[], errors: Array<{ key, error }> }.
 *
 * Every value is routed through services/configSchema so invalid inputs are
 * rejected before being persisted. Valid values are typed via the validator's
 * coerced return (boolean/number/string) into CONFIG; .env always stores
 * String(coerced). Invalid values are reported and NEITHER written to .env NOR
 * applied to CONFIG — callers see them in the `errors` array.
 */
function applyConfigUpdates(updates) {
  const applied = [];
  const errors = [];
  const coercedForEnv = new Map();

  for (const [key, rawValue] of Object.entries(updates)) {
    const validator = getValidator(key);
    const result = validator.validate(rawValue);
    if (!result.ok) {
      errors.push({ key, error: result.error });
      continue;
    }
    CONFIG[key] = result.coerced;
    coercedForEnv.set(key, String(result.coerced));
    applied.push(key);
  }

  // Write only the valid entries to .env. Skip the disk write entirely when
  // nothing validated, so a fully-rejected save doesn't rewrite the file.
  if (applied.length > 0) {
    const envMap = readEnvFile();
    for (const [key, value] of coercedForEnv) {
      envMap.set(key, 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 };