#!/usr/bin/env node

/**
 * Detects telemetry-event additions/modifications in a pull request and
 * posts (or updates) a PR comment when telemetry-related changes are found.
 *
 * This script is executed by .github/workflows/telemetry-pr-check.yml.
 * Keep both files aligned when changing trigger behavior, env usage, or messaging.
 */

const fs = require('node:fs');
const REVIEWER_LOGIN = 'chatasweetie';
const REVIEWER_MENTION = `@${REVIEWER_LOGIN}`;

const COMMENT_MARKER = '<!-- telemetry-event-check -->';
const COMMENT_BODY_WITH_PRIVACY_UPDATE = `${COMMENT_MARKER}
Thank you for contributing to PowerToys. We've detected that this PR might include a new or modified telemetry event. After this PR is merged, please follow these next steps:

- [ ] Reach out to Jessica (${REVIEWER_MENTION}) to follow up on the next steps: https://aka.ms/pt-telemetry-process
`;

const COMMENT_BODY_WITHOUT_PRIVACY_UPDATE = `${COMMENT_MARKER}
Thank you for contributing to PowerToys. We've detected that this PR might include a new or modified telemetry event. Please ensure the following before merging:

- [ ] Add your telemetry events to [DATA_AND_PRIVACY](https://github.com/microsoft/PowerToys/blob/main/DATA_AND_PRIVACY.md).md within this PR.

- [ ] Reach out to Jessica (${REVIEWER_MENTION}) to follow up on the next steps: https://aka.ms/pt-telemetry-process`;

const TELEMETRY_PATH_PATTERNS = [
  /(^|\/)trace\.(h|hpp|cpp|cs)$/i,
  /(^|\/)telemetry\//i,
  /(^|\/)events\/.+event\.cs$/i,
  /^src\/common\/Telemetry\//i,
  /^src\/common\/ManagedTelemetry\//i,
  /^src\/runner\/trace\.(h|cpp)$/i,
  /^src\/settings-ui\/.+\/Telemetry\//i,
];

const TELEMETRY_LINE_PATTERNS = [
  /TraceLoggingWriteWrapper\s*\(/,
  /\bTraceLoggingWrite\s*\(/,
  /\bTRACELOGGING_DEFINE_PROVIDER\b/,
  /\bTraceLoggingOptionProjectTelemetry\b/,
  /\bProjectTelemetryPrivacyDataTag\b/,
  /\bPROJECT_KEYWORD_MEASURE\b/,
  /\bRegisterProvider\s*\(/,
  /\bUnregisterProvider\s*\(/,
  /\bPowerToysTelemetry\.Log\.WriteEvent\s*\(/,
  /\bclass\s+\w+\s*:\s*EventBase\s*,\s*IEvent\b/,
  /\bclass\s+\w+\s*:\s*TelemetryBase\b/,
  /\bPartA_PrivTags\b/,
  /\[EventData\]/,
  /\bEventName\b/,
];

function requireEnv(name) {
  const value = process.env[name];
  if (!value) {
    throw new Error(`Missing required environment variable: ${name}`);
  }
  return value;
}

function validateRepository(repository) {
  if (!/^[^/]+\/[^/]+$/.test(repository)) {
    throw new Error(
      `GITHUB_REPOSITORY must be in owner/repo format, received: ${JSON.stringify(repository)}`
    );
  }
}

function readEventPayload(eventPath) {
  let raw;
  try {
    raw = fs.readFileSync(eventPath, 'utf8');
  } catch (error) {
    throw new Error(`Failed to read event payload at ${eventPath}: ${error.message}`);
  }

  try {
    return JSON.parse(raw);
  } catch (error) {
    throw new Error(`Failed to parse JSON from ${eventPath}: ${error.message}`);
  }
}

function resolvePullNumber(event) {
  const fromPullRequest = event?.pull_request?.number;
  const fromWorkflowDispatch = event?.inputs?.pr_number;
  const rawPullNumber = fromPullRequest ?? fromWorkflowDispatch;

  if (rawPullNumber === undefined || rawPullNumber === null || rawPullNumber === '') {
    throw new Error(
      'Unable to determine pull request number from event payload. Expected pull_request.number or inputs.pr_number.'
    );
  }

  const pullNumber = Number.parseInt(String(rawPullNumber), 10);
  if (!Number.isInteger(pullNumber) || pullNumber <= 0) {
    throw new Error(`Invalid pull request number: ${JSON.stringify(rawPullNumber)}`);
  }

  return pullNumber;
}

function isTelemetryPath(filePath) {
  return TELEMETRY_PATH_PATTERNS.some((pattern) => pattern.test(filePath));
}

function changedLinesFromPatch(patch) {
  if (!patch) {
    return [];
  }

  return patch
    .split('\n')
    .filter((line) => {
      if (line.startsWith('+++') || line.startsWith('---')) {
        return false;
      }
      return line.startsWith('+') || line.startsWith('-');
    })
    .map((line) => line.slice(1));
}

function hasTelemetryLineSignal(lines) {
  return lines.some((line) => TELEMETRY_LINE_PATTERNS.some((pattern) => pattern.test(line)));
}

async function apiRequest(url, method = 'GET', body) {
  const token = requireEnv('GITHUB_TOKEN');
  let response;
  try {
    response = await fetch(url, {
      method,
      headers: {
        Authorization: `Bearer ${token}`,
        Accept: 'application/vnd.github+json',
        'Content-Type': 'application/json',
      },
      body: body ? JSON.stringify(body) : undefined,
    });
  } catch (error) {
    throw new Error(`Network error during ${method} ${url}: ${error.message}`);
  }

  if (!response.ok) {
    const text = await response.text();
    const rateLimitReset = response.headers.get('x-ratelimit-reset');
    const rateLimitHint =
      response.status === 403 && rateLimitReset
        ? ` (rate limit reset at epoch ${rateLimitReset})`
        : '';
    throw new Error(`${method} ${url} failed (${response.status})${rateLimitHint}: ${text}`);
  }

  if (response.status === 204) {
    return null;
  }

  try {
    return await response.json();
  } catch (error) {
    throw new Error(`Failed to parse JSON response for ${method} ${url}: ${error.message}`);
  }
}

async function getAllPullFiles(apiBaseUrl, repository, pullNumber) {
  const files = [];
  let page = 1;

  while (true) {
    const url = `${apiBaseUrl}/repos/${repository}/pulls/${pullNumber}/files?per_page=100&page=${page}`;
    const batch = await apiRequest(url);
    if (!Array.isArray(batch)) {
      throw new Error(`Unexpected response while listing PR files on page ${page}.`);
    }

    if (batch.length === 0) {
      break;
    }

    files.push(...batch);

    if (batch.length < 100) {
      break;
    }

    page += 1;
  }

  return files;
}

async function getPullRequest(apiBaseUrl, repository, pullNumber) {
  const url = `${apiBaseUrl}/repos/${repository}/pulls/${pullNumber}`;
  const pullRequest = await apiRequest(url);
  if (!pullRequest || typeof pullRequest !== 'object') {
    throw new Error('Unexpected response while fetching pull request details.');
  }
  return pullRequest;
}

async function ensureReviewerRequested(apiBaseUrl, repository, pullNumber, pullRequest) {
  const authorLogin = String(pullRequest?.user?.login || '').toLowerCase();
  const targetReviewer = REVIEWER_LOGIN.toLowerCase();

  if (authorLogin === targetReviewer) {
    console.log(`Skipping reviewer request: ${REVIEWER_LOGIN} is the PR author.`);
    return;
  }

  const requestedReviewers = Array.isArray(pullRequest?.requested_reviewers)
    ? pullRequest.requested_reviewers
    : [];
  const alreadyRequested = requestedReviewers.some(
    (reviewer) => String(reviewer?.login || '').toLowerCase() === targetReviewer
  );

  if (alreadyRequested) {
    console.log(`Reviewer ${REVIEWER_LOGIN} is already requested.`);
    return;
  }

  const url = `${apiBaseUrl}/repos/${repository}/pulls/${pullNumber}/requested_reviewers`;
  try {
    await apiRequest(url, 'POST', { reviewers: [REVIEWER_LOGIN] });
    console.log(`Requested reviewer ${REVIEWER_LOGIN}.`);
  } catch (error) {
    // Reviewer request should not fail the telemetry guidance workflow.
    console.warn(
      `Unable to request reviewer ${REVIEWER_LOGIN}: ${error instanceof Error ? error.message : String(error)}`
    );
  }
}

async function findExistingTelemetryComment(apiBaseUrl, repository, pullNumber) {
  let page = 1;

  while (true) {
    const commentsUrl = `${apiBaseUrl}/repos/${repository}/issues/${pullNumber}/comments?per_page=100&page=${page}`;
    const comments = await apiRequest(commentsUrl);

    if (!Array.isArray(comments)) {
      throw new Error(`Unexpected response while listing issue comments on page ${page}.`);
    }

    const existing = comments.find(
      (comment) => typeof comment.body === 'string' && comment.body.includes(COMMENT_MARKER)
    );
    if (existing) {
      return existing;
    }

    if (comments.length < 100) {
      return null;
    }

    page += 1;
  }
}

function detectTelemetryChanges(files) {
  const matches = [];

  for (const file of files) {
    const filename = file.filename || '';
    const telemetryPath = isTelemetryPath(filename);
    const changedLines = changedLinesFromPatch(file.patch);
    const telemetryLineSignal = hasTelemetryLineSignal(changedLines);

    // Some large diffs omit patch content. If the file path is telemetry-centric,
    // treat it as a telemetry modification to avoid false negatives.
    const patchUnavailable = !file.patch && telemetryPath;

    if (telemetryPath || telemetryLineSignal || patchUnavailable) {
      matches.push({
        filename,
        telemetryPath,
        telemetryLineSignal,
        patchUnavailable,
      });
    }
  }

  return matches;
}

function hasDataAndPrivacyChange(files) {
  return files.some((file) => {
    const filename = (file.filename || '').toLowerCase();
    return filename === 'data_and_privacy.md';
  });
}

async function upsertPrComment(apiBaseUrl, repository, pullNumber, body) {
  const existing = await findExistingTelemetryComment(apiBaseUrl, repository, pullNumber);

  if (existing) {
    const updateUrl = `${apiBaseUrl}/repos/${repository}/issues/comments/${existing.id}`;
    await apiRequest(updateUrl, 'PATCH', { body });
    console.log(`Updated existing telemetry comment (id: ${existing.id}).`);
    return;
  }

  const createUrl = `${apiBaseUrl}/repos/${repository}/issues/${pullNumber}/comments`;
  await apiRequest(createUrl, 'POST', { body });
  console.log('Created telemetry comment on PR.');
}

async function main() {
  const eventPath = requireEnv('GITHUB_EVENT_PATH');
  const repository = requireEnv('GITHUB_REPOSITORY');
  const apiBaseUrl = process.env.GITHUB_API_URL || 'https://api.github.com';
  validateRepository(repository);

  let parsedApiBaseUrl;
  try {
    parsedApiBaseUrl = new URL(apiBaseUrl);
  } catch {
    throw new Error(`Invalid GITHUB_API_URL: ${JSON.stringify(apiBaseUrl)}`);
  }

  const event = readEventPayload(eventPath);
  const pullNumber = resolvePullNumber(event);

  console.log(`Event name: ${process.env.GITHUB_EVENT_NAME || 'unknown'}`);
  console.log(`Repository: ${repository}`);
  console.log(`PR number: ${pullNumber}`);

  const files = await getAllPullFiles(parsedApiBaseUrl.origin, repository, pullNumber);

  if (files.length === 0) {
    console.log('No changed files found for PR; skipping telemetry comment update.');
    return;
  }

  const matches = detectTelemetryChanges(files);
  const dataAndPrivacyChanged = hasDataAndPrivacyChange(files);

  console.log(`Scanned ${files.length} changed files.`);
  console.log(`Telemetry matches found: ${matches.length}.`);
  console.log(`DATA_AND_PRIVACY.md changed: ${dataAndPrivacyChanged}.`);

  if (matches.length === 0) {
    console.log('No telemetry-related additions/modifications detected.');
    return;
  }

  for (const match of matches) {
    console.log(
      `- ${match.filename} (telemetryPath=${match.telemetryPath}, telemetryLineSignal=${match.telemetryLineSignal}, patchUnavailable=${match.patchUnavailable})`
    );
  }

  try {
    const pullRequest = await getPullRequest(parsedApiBaseUrl.origin, repository, pullNumber);
    await ensureReviewerRequested(parsedApiBaseUrl.origin, repository, pullNumber, pullRequest);
  } catch (error) {
    console.warn(
      'Failed to fetch PR details or request reviewer; continuing to post telemetry guidance comment.'
    );
    console.warn(error instanceof Error ? error.stack || error.message : error);
  }

  const commentBody = dataAndPrivacyChanged
    ? COMMENT_BODY_WITH_PRIVACY_UPDATE
    : COMMENT_BODY_WITHOUT_PRIVACY_UPDATE;

  await upsertPrComment(apiBaseUrl, repository, pullNumber, commentBody);
}

main().catch((error) => {
  console.error('Telemetry PR check failed.');
  console.error(error instanceof Error ? error.stack || error.message : error);
  process.exit(1);
});