'use strict';

const https = require('node:https');

const LATEST_RELEASE_URL = 'https://git.pejicorp.com/api/v1/repos/peji/Alta-Proxy-Tool/releases/latest';
const RELEASES_PAGE_URL = 'https://git.pejicorp.com/peji/Alta-Proxy-Tool/releases';
const REQUEST_TIMEOUT_MS = 5000;
const MAX_BODY_BYTES = 64 * 1024;
const MAX_RELEASE_NAME_LENGTH = 200;

// Strict SemVer 2.0.0 without loose forms such as omitted fields.
const SEMVER_PATTERN = /^(0|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)(?:-((?:0|[1-9]\d*|\d*[A-Za-z-][0-9A-Za-z-]*)(?:\.(?:0|[1-9]\d*|\d*[A-Za-z-][0-9A-Za-z-]*))*))?(?:\+([0-9A-Za-z-]+(?:\.[0-9A-Za-z-]+)*))?$/;

class UpdatePolicyError extends Error {
  constructor(code, message, options) {
    super(message, options);
    this.name = 'UpdatePolicyError';
    this.code = code;
  }
}

function policyError(code, message, cause) {
  return new UpdatePolicyError(code, message, cause ? { cause } : undefined);
}

function parseSemver(version, errorCode = 'INVALID_VERSION') {
  if (typeof version !== 'string') {
    throw policyError(errorCode, 'Version must be a strict semantic version string');
  }

  const match = SEMVER_PATTERN.exec(version);
  if (!match) {
    throw policyError(errorCode, 'Version must use strict SemVer 2.0.0 syntax');
  }

  return {
    major: BigInt(match[1]),
    minor: BigInt(match[2]),
    patch: BigInt(match[3]),
    prerelease: match[4] === undefined ? null : match[4].split('.'),
  };
}

function normalizeReleaseTag(tag) {
  const version = tag.startsWith('v') ? tag.slice(1) : tag;
  parseSemver(version, 'INVALID_RELEASE_VERSION');
  return version;
}

function compareIdentifier(left, right) {
  const leftNumeric = /^\d+$/.test(left);
  const rightNumeric = /^\d+$/.test(right);

  if (leftNumeric && rightNumeric) {
    const leftNumber = BigInt(left);
    const rightNumber = BigInt(right);
    return leftNumber < rightNumber ? -1 : leftNumber > rightNumber ? 1 : 0;
  }
  if (leftNumeric !== rightNumeric) {
    return leftNumeric ? -1 : 1;
  }
  return left < right ? -1 : left > right ? 1 : 0;
}

function compareSemver(leftVersion, rightVersion) {
  const left = parseSemver(leftVersion);
  const right = parseSemver(rightVersion);

  for (const key of ['major', 'minor', 'patch']) {
    if (left[key] < right[key]) return -1;
    if (left[key] > right[key]) return 1;
  }

  if (left.prerelease === null && right.prerelease === null) return 0;
  if (left.prerelease === null) return 1;
  if (right.prerelease === null) return -1;

  const count = Math.max(left.prerelease.length, right.prerelease.length);
  for (let index = 0; index < count; index += 1) {
    if (left.prerelease[index] === undefined) return -1;
    if (right.prerelease[index] === undefined) return 1;
    const comparison = compareIdentifier(left.prerelease[index], right.prerelease[index]);
    if (comparison !== 0) return comparison;
  }
  return 0;
}

function sanitizeText(value) {
  return value
    .trim()
    .slice(0, MAX_RELEASE_NAME_LENGTH)
    .replaceAll('&', '&amp;')
    .replaceAll('<', '&lt;')
    .replaceAll('>', '&gt;')
    .replaceAll('"', '&quot;')
    .replaceAll("'", '&#39;');
}

function validateRuntimeValue(value, field) {
  if (typeof value !== 'string' || value.length === 0 || value.length > 64 || !/^[a-zA-Z0-9_-]+$/.test(value)) {
    throw policyError('INVALID_RUNTIME_METADATA', `Invalid ${field} metadata`);
  }
  return value;
}

function parseRelease(body) {
  let release;
  try {
    release = JSON.parse(body.toString('utf8'));
  } catch (error) {
    throw policyError('INVALID_RESPONSE', 'Release response was not valid JSON', error);
  }

  if (!release || typeof release !== 'object' || Array.isArray(release)) {
    throw policyError('INVALID_RESPONSE', 'Release response must be an object');
  }
  if (typeof release.tag_name !== 'string' || release.tag_name.length > 128) {
    throw policyError('INVALID_RESPONSE', 'Release tag_name must be a bounded string');
  }
  if (release.name !== undefined && release.name !== null && typeof release.name !== 'string') {
    throw policyError('INVALID_RESPONSE', 'Release name must be a string when provided');
  }
  if (typeof release.name === 'string' && release.name.length > 1000) {
    throw policyError('INVALID_RESPONSE', 'Release name exceeds the schema limit');
  }
  if (release.published_at !== undefined && release.published_at !== null && typeof release.published_at !== 'string') {
    throw policyError('INVALID_RESPONSE', 'Release published_at must be a string when provided');
  }

  let publishedAt;
  if (typeof release.published_at === 'string') {
    if (release.published_at.length > 64) {
      throw policyError('INVALID_RESPONSE', 'Release published_at exceeds the schema limit');
    }
    const timestamp = new Date(release.published_at);
    if (Number.isNaN(timestamp.getTime())) {
      throw policyError('INVALID_RESPONSE', 'Release published_at must be a valid timestamp');
    }
    publishedAt = timestamp.toISOString();
  }

  return {
    latestVersion: release.tag_name,
    releaseName: sanitizeText(release.name || release.tag_name),
    publishedAt,
  };
}

function defaultRequest({
  url,
  timeoutMs,
  maxBodyBytes,
  httpsGet = https.get,
  setTimer = setTimeout,
  clearTimer = clearTimeout,
}) {
  if (url !== LATEST_RELEASE_URL) {
    return Promise.reject(policyError('UNTRUSTED_REQUEST_URL', 'Update checks are restricted to GitPeji'));
  }

  return new Promise((resolve, reject) => {
    let settled = false;
    let responseStream = null;
    let deadlineTimer = null;
    const clearDeadline = () => {
      if (deadlineTimer !== null) {
        clearTimer(deadlineTimer);
        deadlineTimer = null;
      }
    };
    const finishReject = (error) => {
      if (!settled) {
        settled = true;
        clearDeadline();
        reject(error);
      }
    };

    const request = httpsGet(url, {
      headers: {
        accept: 'application/json',
        'user-agent': 'Alta-Proxy-Tool-update-check',
      },
      agent: false,
    }, (response) => {
      responseStream = response;
      const chunks = [];
      let receivedBytes = 0;
      const contentLength = Number(response.headers['content-length']);

      if (Number.isFinite(contentLength) && contentLength > maxBodyBytes) {
        response.destroy();
        finishReject(policyError('RESPONSE_TOO_LARGE', 'Release response exceeded the size limit'));
        return;
      }

      response.on('data', (chunk) => {
        receivedBytes += chunk.length;
        if (receivedBytes > maxBodyBytes) {
          response.destroy();
          finishReject(policyError('RESPONSE_TOO_LARGE', 'Release response exceeded the size limit'));
          return;
        }
        chunks.push(chunk);
      });
      response.on('end', () => {
        if (settled) return;
        settled = true;
        clearDeadline();
        resolve({
          statusCode: response.statusCode,
          headers: response.headers,
          body: Buffer.concat(chunks),
          url,
        });
      });
      response.on('error', finishReject);
    });

    deadlineTimer = setTimer(() => {
      const timeoutError = policyError('REQUEST_TIMEOUT', 'Release check timed out');
      if (responseStream && typeof responseStream.destroy === 'function') responseStream.destroy();
      request.destroy(timeoutError);
      finishReject(timeoutError);
    }, timeoutMs);
    request.on('error', (error) => {
      if (error instanceof UpdatePolicyError) {
        finishReject(error);
      } else {
        finishReject(policyError('REQUEST_FAILED', 'Release check failed', error));
      }
    });
  });
}

async function checkForUpdate({
  currentVersion,
  request = defaultRequest,
  platform = process.platform,
  arch = process.arch,
} = {}) {
  parseSemver(currentVersion, 'INVALID_CURRENT_VERSION');
  if (typeof request !== 'function') {
    throw policyError('INVALID_REQUEST_ADAPTER', 'Request adapter must be a function');
  }

  const safePlatform = validateRuntimeValue(platform, 'platform');
  const safeArch = validateRuntimeValue(arch, 'architecture');
  const baseMetadata = {
    currentVersion,
    releasesPageUrl: RELEASES_PAGE_URL,
    platform: safePlatform,
    arch: safeArch,
  };

  const response = await request({
    url: LATEST_RELEASE_URL,
    timeoutMs: REQUEST_TIMEOUT_MS,
    maxBodyBytes: MAX_BODY_BYTES,
    redirects: 'error',
  });

  if (!response || typeof response !== 'object') {
    throw policyError('INVALID_RESPONSE', 'Request adapter returned an invalid response');
  }
  if (response.url !== LATEST_RELEASE_URL) {
    throw policyError('UNTRUSTED_RESPONSE_URL', 'Release response did not come from the exact GitPeji endpoint');
  }

  const statusCode = Number(response.statusCode);
  if (statusCode >= 300 && statusCode < 400) {
    throw policyError('REDIRECT_REJECTED', 'Release endpoint redirects are not allowed');
  }
  if (statusCode === 404) {
    return { status: 'no-release', ...baseMetadata };
  }
  if (statusCode !== 200) {
    throw policyError('HTTP_ERROR', `Release endpoint returned HTTP ${statusCode}`);
  }

  const contentType = response.headers && response.headers['content-type'];
  if (typeof contentType !== 'string' || !/^application\/json(?:\s*;|$)/i.test(contentType)) {
    throw policyError('INVALID_CONTENT_TYPE', 'Release endpoint did not return JSON');
  }

  const body = Buffer.isBuffer(response.body)
    ? response.body
    : typeof response.body === 'string'
      ? Buffer.from(response.body)
      : null;
  if (!body) {
    throw policyError('INVALID_RESPONSE', 'Release response body must be bytes or text');
  }
  if (body.length > MAX_BODY_BYTES) {
    throw policyError('RESPONSE_TOO_LARGE', 'Release response exceeded the size limit');
  }

  const release = parseRelease(body);
  const latestVersion = normalizeReleaseTag(release.latestVersion);

  const metadata = {
    status: compareSemver(latestVersion, currentVersion) > 0
      ? 'update-available'
      : 'up-to-date',
    ...baseMetadata,
    latestVersion,
    releaseName: release.releaseName,
  };
  if (release.publishedAt !== undefined) {
    metadata.publishedAt = release.publishedAt;
  }
  return metadata;
}

module.exports = {
  LATEST_RELEASE_URL,
  RELEASES_PAGE_URL,
  REQUEST_TIMEOUT_MS,
  MAX_BODY_BYTES,
  UpdatePolicyError,
  checkForUpdate,
  compareSemver,
  defaultRequest,
};