/**
 * Copyright 2024 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import { createInterface } from 'readline/promises';
import { v4 as uuidV4 } from 'uuid';
import type { AnalyticsInfo } from '../types/analytics';
import { configstore, getUserSettings } from './configstore';
import { logger } from './logger';
import { toolsPackage } from './package';

// This code is largely adapted from
// https://github.com/firebase/firebase-tools/blob/master/src/track.ts

export const ANALYTICS_OPT_OUT_CONFIG_TAG = 'analyticsOptOut';

/**
 * The track function accepts this abstract class, but callers should use
 * one of the pre-defined events listed below this class. If you need to add a
 * new event type, add it with the others below.
 */
export abstract class GAEvent {
  // The event name as it will appear in GA.
  // This must be less than 40 characters
  abstract name: string;
  // Additional parameters.
  // ABSOLUTELY NO FREE-FORM OR PII FIELDS
  parameters?: Record<string, string | number | undefined>;
  // Sticky parameters that should be maintained for the duration of the
  // session.
  stickyParameters?: Record<string, string | number | undefined>;
  // Duration in milliseconds. Make sure this is always at least 1 so that the
  // metrics appear in realtime view.
  abstract duration: number;
}

// Add new events here; this way everything's centralized and auditable.

export class PageViewEvent extends GAEvent {
  name = 'page_view';
  duration = 1;

  constructor(page_title: string) {
    super();
    this.parameters = { page_title };
  }
}

export class FirstUsageEvent extends GAEvent {
  name = 'first_visit';
  duration = 1;

  constructor() {
    super();
  }
}

export class ToolsRequestEvent extends GAEvent {
  name = 'tools_request';
  duration = 1;

  constructor(route: string) {
    super();
    this.parameters = { route };
  }
}

export class RunCommandEvent extends GAEvent {
  name = 'run_command';
  duration = 1; // Should we actually track command duration?

  constructor(command: string, runtime_type: string) {
    super();
    this.stickyParameters = { command, runtime_type };
  }
}

export class InitEvent extends GAEvent {
  name = 'init';
  duration = 1;

  constructor(
    platform: 'firebase' | 'googlecloud' | 'nodejs' | 'nextjs' | 'go'
  ) {
    super();
    this.parameters = { platform };
  }
}

export class ConfigEvent extends GAEvent {
  name = 'config_set';
  duration = 1;

  constructor(key: 'analyticsOptOut') {
    super();
    this.parameters = { key };
  }
}

/**
 * Main function for recording analytics. This is a no-op if analyitcs are
 * disabled.
 */
export async function record(event: GAEvent): Promise<void> {
  if (!isAnalyticsEnabled()) return;
  await recordInternal(event, getSession());
}

/** Displays a notification that analytics are in use. */
export async function notifyAnalyticsIfFirstRun(): Promise<void> {
  if (!isAnalyticsEnabled()) return;

  if (configstore.get(NOTIFICATION_ACKED)) {
    return;
  }

  console.log(ANALYTICS_NOTIFICATION);

  const readline = createInterface({
    input: process.stdin,
    output: process.stdout,
  });
  await readline.question('Press "Enter" to continue');
  readline.close();

  configstore.set(NOTIFICATION_ACKED, true);

  await record(new FirstUsageEvent());
}

/** Gets session information for the UI. */
export function getAnalyticsSettings(): AnalyticsInfo {
  if (!isAnalyticsEnabled()) {
    return { enabled: false };
  }

  const session = getSession();

  return {
    enabled: true,
    property: GA_INFO.property,
    measurementId: GA_INFO.measurementId,
    apiSecret: GA_INFO.apiSecret,
    clientId: session.clientId,
    sessionId: session.sessionId,
    debug: {
      debugMode: isDebugMode(),
      validateOnly: isValidateOnly(),
    },
  };
}

// ===============================================================
// Start internal implementation

const ANALYTICS_NOTIFICATION =
  'Genkit CLI and Developer UI use cookies and ' +
  'similar technologies from Google\nto deliver and enhance the quality of its ' +
  'services and to analyze usage.\n' +
  'Learn more at https://policies.google.com/technologies/cookies';
const NOTIFICATION_ACKED = 'analytics_notification';
const CONFIGSTORE_CLIENT_KEY = 'genkit-tools-ga-id';

const GA_INFO = {
  property: 'genkit-tools',
  measurementId: 'G-2K1MPK763J',
  apiSecret: 'UccV7rIoTF6II6E9zYX5Ow',
};
const GA_USER_PROPS = {
  node_platform: {
    value: process.platform,
  },
  node_version: {
    value: process.version,
  },
  tools_version: {
    value: toolsPackage.version,
  },
};

interface AnalyticsSession {
  clientId: string;

  // https://support.google.com/analytics/answer/9191807
  // We treat each CLI invocation as a different session, including any CLI
  // events.
  sessionId: string;
  totalEngagementSeconds: number;
  stickyParameters: Record<string, string | number | undefined>;
}

// Whether the events sent should be tagged so that they are shown in GA Debug
// View in real time (for Googler to debug) and excluded from reports. To
// enable, set the env var GENKIT_GA_DEBUG.
function isDebugMode(): boolean {
  return !!process.env['GENKIT_GA_DEBUG'];
}

// Whether to validate events format instead of collecting them. Should only
// be used to debug the Firebase CLI / Emulator UI itself regarding issues
// with Analytics. To enable, set the env var GENKIT_GA_VALIDATE.
// In the CLI, this is implemented by sending events to the GA4 measurement
// validation API (which does not persist events) and printing the response.
function isValidateOnly(): boolean {
  return !!process.env['GENKIT_GA_VALIDATE'];
}

// For now, this is default false unless GENKIT_GA_DEBUG or GENKIT_GA_VALIDATE
// are set. Once we have opt-out and we're ready for public preview this will
// get updated.
function isAnalyticsEnabled(): boolean {
  return (
    !process.argv.includes('--non-interactive') &&
    !getUserSettings()[ANALYTICS_OPT_OUT_CONFIG_TAG]
  );
}

async function recordInternal(
  event: GAEvent,
  session: AnalyticsSession
): Promise<void> {
  Object.assign(session.stickyParameters, event.stickyParameters);
  const joinedParams = { ...session.stickyParameters, ...event.parameters };

  const validate = isValidateOnly();
  const search = `?api_secret=${GA_INFO.apiSecret}&measurement_id=${GA_INFO.measurementId}`;
  const validatePath = isValidateOnly() ? 'debug/' : '';
  const url = `https://www.google-analytics.com/${validatePath}mp/collect${search}`;
  const body = {
    // Get timestamp in millis and append '000' to get micros as string.
    // Not using multiplication due to JS number precision limit.
    timestamp_micros: `${Date.now()}000`,
    client_id: session.clientId,
    user_properties: {
      ...GA_USER_PROPS,
    },
    validationBehavior: validate ? 'ENFORCE_RECOMMENDATIONS' : undefined,
    events: [
      {
        name: event.name,
        params: {
          session_id: session.sessionId,

          // engagement_time_msec and session_id must be set for the activity
          // to display in standard reports like Realtime.
          // https://developers.google.com/analytics/devguides/collection/protocol/ga4/sending-events?client_type=gtag#optional_parameters_for_reports

          // https://support.google.com/analytics/answer/11109416?hl=en
          // Additional engagement time since last event, in microseconds.
          engagement_time_msec: event.duration
            .toFixed(3)
            .replace('.', '')
            .replace(/^0+/, ''), // trim leading zeros

          // https://support.google.com/analytics/answer/7201382?hl=en
          // To turn debug mode off, `debug_mode` must be left out not `false`.
          debug_mode: isDebugMode() ? true : undefined,
          ...joinedParams,
        },
      },
    ],
  };

  if (validate) {
    logger.debug(
      `Sending Analytics for event ${event.name}`,
      joinedParams,
      body
    );
  }
  try {
    const response = await fetch(url, {
      method: 'POST',
      headers: {
        'content-type': 'application/json;charset=UTF-8',
      },
      body: JSON.stringify(body),
    });
    if (validate) {
      // If the validation endpoint is used, response may contain errors.
      if (!response.ok) {
        logger.warn(`Analytics validation HTTP error: ${response.status}`);
      }
      const respBody = await response.text;
      logger.debug(`Analytics validation result: ${respBody}`);
    }
    // response.ok / response.status intentionally ignored, see comment below.
  } catch (e: unknown) {
    if (validate) {
      throw e;
    }
    // Otherwise, we will ignore the status / error for these reasons:
    // * the endpoint always return 2xx even if request is malformed
    // * non-2xx requests should _not_ be retried according to documentation
    // * analytics is non-critical and should not fail other operations.
    // https://developers.google.com/analytics/devguides/collection/protocol/ga4/reference?client_type=gtag#response_codes
    return;
  }
}

let currentSession: AnalyticsSession | undefined = undefined;
function getSession(): AnalyticsSession {
  if (currentSession) {
    return currentSession;
  }

  // ClientID is sticky
  let clientId: string | undefined = configstore.get(CONFIGSTORE_CLIENT_KEY);
  if (!clientId) {
    clientId = uuidV4();
    configstore.set(CONFIGSTORE_CLIENT_KEY, clientId);
  }

  currentSession = {
    clientId,
    // This must be an int64 string, but only ~50 bits are generated here
    // for simplicity. (AFAICT, they just need to be unique per clientId,
    // instead of globally. Revisit if that is not the case.)
    // https://help.analyticsedge.com/article/misunderstood-metrics-sessions-in-google-analytics-4/#:~:text=The%20Session%20ID%20Is%20Not%20Unique
    sessionId: (Math.random() * Number.MAX_SAFE_INTEGER).toFixed(0),
    totalEngagementSeconds: 0,
    stickyParameters: {},
  };

  return currentSession;
}