// Copyright 2018 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 {StackdriverFormat} from '@opencensus/propagation-stackdriver';
import * as path from 'path';

import {cls, TraceCLSConfig} from './cls';
import {OpenCensusPropagation, TracePolicy} from './config';
import {LEVELS, Logger} from './logger';
import {StackdriverTracer} from './trace-api';
import {pluginLoader, PluginLoaderConfig} from './trace-plugin-loader';
import {traceWriter, TraceWriterConfig} from './trace-writer';
import {BuiltinTracePolicy, TracePolicyConfig} from './tracing-policy';
import {Component, Forceable, packageNameFromPath, Singleton} from './util';

export type TopLevelConfig =
  | Forceable<{
      enabled: boolean;
      logLevel: number;
      disableUntracedModulesWarning: boolean;
      clsConfig: Forceable<TraceCLSConfig>;
      writerConfig: Forceable<TraceWriterConfig>;
      pluginLoaderConfig: Forceable<PluginLoaderConfig>;
      tracePolicyConfig: TracePolicyConfig;
      overrides: {
        tracePolicy?: TracePolicy;
        propagation?: OpenCensusPropagation;
      };
    }>
  | {
      enabled: false;
    };

/**
 * A class that represents automatic tracing.
 */
export class Tracing implements Component {
  /** A logger. */
  private readonly logger: Logger;
  /** The configuration object for this instance. */
  private readonly config: Forceable<TopLevelConfig>;

  /**
   * Constructs a new Tracing instance.
   * @param config The configuration for this instance.
   * @param traceAgent An object representing the custom tracing API.
   */
  constructor(
    config: TopLevelConfig,
    private readonly traceAgent: StackdriverTracer
  ) {
    this.config = config;
    let logLevel = config.enabled ? config.logLevel : 0;
    // Clamp the logger level.
    const defaultLevels = LEVELS;
    if (logLevel < 0) {
      logLevel = 0;
    } else if (logLevel >= defaultLevels.length) {
      logLevel = defaultLevels.length - 1;
    }
    this.logger = new Logger({
      level: defaultLevels[logLevel],
      tag: '@google-cloud/trace-agent',
    });
  }

  /**
   * Logs an warning message detailing the list of modules that were loaded
   * before the Trace Agent. Loading these modules before the Trace Agent may
   * prevent us from monkeypatching those modules for automatic tracing.
   * @param filesLoadedBeforeTrace The list of files that were loaded using
   * require() before the Stackdriver Trace Agent was required.
   */
  logModulesLoadedBeforeTrace(filesLoadedBeforeTrace: string[]) {
    const modulesLoadedBeforeTrace: string[] = [];
    const traceModuleName = path.join('@google-cloud', 'trace-agent');
    for (let i = 0; i < filesLoadedBeforeTrace.length; i++) {
      const moduleName = packageNameFromPath(filesLoadedBeforeTrace[i]);
      if (
        moduleName &&
        moduleName !== traceModuleName &&
        modulesLoadedBeforeTrace.indexOf(moduleName) === -1
      ) {
        modulesLoadedBeforeTrace.push(moduleName);
      }
    }
    if (modulesLoadedBeforeTrace.length > 0) {
      this.logger.warn(
        'StackdriverTracer#start: Tracing might not work as the following modules',
        'were loaded before the trace agent was initialized:',
        `[${modulesLoadedBeforeTrace.sort().join(', ')}]`
      );
    }
  }

  /**
   * Enables automatic tracing support and the custom span API.
   */
  enable(): void {
    if (!this.config.enabled) {
      return;
    }

    // Initialize context propagation mechanism configuration.
    try {
      traceWriter.create(this.config.writerConfig, this.logger);
      cls.create(this.config.clsConfig, this.logger);
    } catch (e) {
      this.logger.error(
        'StackdriverTracer#start: Disabling the Trace Agent for the',
        `following reason: ${(e as Error).message}`
      );
      this.disable();
      return;
    }
    traceWriter
      .get()
      .initialize()
      .catch(err => {
        this.logger.error(
          'StackdriverTracer#start: Disabling the Trace Agent for the',
          `following reason: ${err.message}`
        );
        this.disable();
      });
    cls.get().enable();

    const tracePolicy =
      this.config.overrides.tracePolicy ||
      new BuiltinTracePolicy(this.config.tracePolicyConfig);
    const propagation =
      this.config.overrides.propagation || new StackdriverFormat();

    const tracerComponents = {logger: this.logger, tracePolicy, propagation};

    this.traceAgent.enable(
      this.config.pluginLoaderConfig.tracerConfig,
      tracerComponents
    );
    pluginLoader
      .create(this.config.pluginLoaderConfig, tracerComponents)
      .activate();

    // Require http and https again, now that the plugin loader is activated.
    // This forces them to be patched.
    require('http');
    require('https');

    if (
      typeof this.config.writerConfig.authOptions.projectId !== 'string' &&
      typeof this.config.writerConfig.authOptions.projectId !== 'undefined'
    ) {
      this.logger.error(
        'StackdriverTracer#start: config.projectId, if provided, must be a string.',
        'Disabling trace agent.'
      );
      this.disable();
      return;
    }

    // Make trace agent available globally without requiring package
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    (global as any)._google_trace_agent = this.traceAgent;

    this.logger.info('StackdriverTracer#start: Trace Agent activated.');
  }

  /**
   * Disables automatic tracing support. This disables the publicly exposed
   * custom span API, as well as any instances passed to plugins. This also
   * prevents the Trace Writer from publishing additional traces.
   */
  disable() {
    if (pluginLoader.exists()) {
      pluginLoader.get().deactivate();
    }
    if (this.traceAgent.isActive()) {
      this.traceAgent.disable();
    }
    if (cls.exists()) {
      cls.get().disable();
    }
    if (traceWriter.exists()) {
      traceWriter.get().stop();
    }
  }
}

export const tracing = new Singleton(Tracing);