/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

import { createRequire } from 'node:module';
import path from 'node:path';
import { pathToFileURL } from 'node:url';
import createDebug from 'debug';
import { EventEmitter } from 'eventemitter3';
import _ from 'lodash';
import { v4 as uuidv4 } from 'uuid';
import { resolveBuiltinPackage } from '../builtin-packages.ts';
import { engine_util as engineUtil } from '../commons/index.ts';
import HttpEngine from './engine_http.ts';
import SocketIoEngine from './engine_socketio.ts';
import WSEngine from './engine_ws.ts';
import type { PhaseSpec } from './phases.ts';
import createPhaser from './phases.ts';
import createReader from './readers.ts';
import type { PeriodMetrics } from './ssms.ts';
import { SSMS } from './ssms.ts';
import wl from './weighted-pick.ts';

const debug = createDebug('runner');
const debugPerf = createDebug('perf');

const require = createRequire(import.meta.url);

// Minimal structural view of a runnable script.
type ScriptLike = { config: Record<string, any>; [key: string]: any };

// A compiled scenario: run a VU through the flow.
type ScenarioFn = (
  context: any,
  callback: (err: any, context: any) => void
) => unknown;

// Contract every engine (built-in or third-party) must satisfy:
export interface EngineInstance {
  createScenario(spec: Record<string, any>, ee: any): ScenarioFn;
  init?: () => Promise<void>;
  __name?: string;
}

type EngineConstructor = new (
  script: ScriptLike,
  ee?: any,
  helpers?: any
) => EngineInstance;

interface EngineWarnings {
  engines: Record<string, { message: string; error: unknown }>;
}

interface RunState {
  pendingScenarios: number;
  compiledScenarios: ScenarioFn[] | null;
  scenarioEvents: EventEmitter | null;
  picker: (() => [number, any]) | undefined;
  engines: Array<EngineInstance | undefined>;
  metrics: SSMS;
}

export interface RunnerInstance extends EventEmitter {
  run(contextVars?: Record<string, any> | null): void;
  stop(done?: unknown): Promise<void>;
  warnings: EngineWarnings;
}

const Engines: Record<string, EngineConstructor> = {
  http: HttpEngine,
  ws: WSEngine,
  socketio: SocketIoEngine
};

const contextFuncs = {
  $randomString,
  $randomNumber
};

const runnerFuncs = {
  handleScriptHook,
  prepareScript,
  loadProcessor
};

export { runner, contextFuncs, runnerFuncs };

async function loadEngines(
  script: ScriptLike,
  ee: any,
  warnings: EngineWarnings = {
    engines: {}
  }
) {
  const engineSpecs: Record<string, unknown> = Object.assign(
    {},
    Engines,
    script.config.engines
  );
  const loadedEngines: Array<EngineInstance | undefined> = [];

  for (const engineName of Object.keys(engineSpecs)) {
    const moduleName = `artillery-engine-${engineName}`;
    try {
      let Engine: EngineConstructor;
      if (typeof Engines[engineName] !== 'undefined') {
        Engine = Engines[engineName];
      } else {
        // Resolve with CJS semantics (bare specifiers, directories via
        // package.json "main"), load with import() - handles both CJS
        // and ESM engines, including ESM with top-level await.
        // Bare specifier first (user-installed copies win), bundled
        // built-in packages second (dist/builtin-packages)
        const enginePath = resolveBuiltinPackage(moduleName);
        const ns = await import(pathToFileURL(enginePath).href);
        Engine = ns.default ?? ns;
      }
      const engine = new Engine(script, ee, engineUtil);
      engine.__name = engineName;
      loadedEngines.push(engine);
    } catch (err) {
      console.log(
        'WARNING: engine %s specified but module %s could not be loaded',
        engineName,
        moduleName
      );
      console.log((err as Error).stack);
      warnings.engines[engineName] = {
        message: 'Could not load',
        error: err
      };
      loadedEngines.push(undefined);
    }
  }

  return { loadedEngines, warnings };
}

async function loadProcessor(
  script: ScriptLike,
  options: { scriptPath: string; [key: string]: any }
) {
  const absoluteScriptPath = path.resolve(process.cwd(), options.scriptPath);
  if (script.config.processor) {
    const processorPath = path.resolve(
      path.dirname(absoluteScriptPath),
      script.config.processor
    );

    // Resolve with CJS semantics first (handles extensionless paths and
    // directories); fall back to the path as-is
    let resolvedPath = processorPath;
    try {
      resolvedPath = require.resolve(processorPath);
    } catch (_err) {}

    // import() loads both CJS and ESM (including ESM with top-level
    // await). Normalize the result into a plain mutable object: module
    // namespace objects are frozen, and engines/plugins may attach
    // properties to the processor object later (e.g. $rewriteMetricName)
    const ns = await import(pathToFileURL(resolvedPath).href);
    script.config.processor = Object.assign({}, ns.default ?? {}, ns);
  }

  return script;
}

function prepareScript(script: ScriptLike, payload: any): ScriptLike {
  const runnableScript = _.cloneDeep(script);

  _.each(runnableScript.config.phases, (phaseSpec: Record<string, any>) => {
    phaseSpec.mode = phaseSpec.mode || runnableScript.config.mode;
  });

  if (payload) {
    if (_.isArray(payload[0])) {
      runnableScript.config.payload = [
        {
          fields: runnableScript.config.payload.fields,
          reader: createReader(
            runnableScript.config.payload.order,
            runnableScript.config.payload
          ),
          data: payload
        }
      ];
    } else {
      runnableScript.config.payload = payload;
      _.each(runnableScript.config.payload, (el: Record<string, any>) => {
        el.reader = createReader(el.order, el);
      });
    }
  } else {
    runnableScript.config.payload = null;
  }

  // Flatten flows (can have nested arrays of request specs with YAML references):
  _.each(runnableScript.scenarios, (scenarioSpec: Record<string, any>) => {
    scenarioSpec.flow = _.flatten(scenarioSpec.flow);
  });

  return runnableScript;
}

async function runner(
  script: ScriptLike,
  payload?: any,
  options?: Record<string, any>,
  callback?: (err: Error | null, runner?: RunnerInstance) => void
): Promise<RunnerInstance> {
  const opts = _.assign(
    {
      periodicStats: script.config.statsInterval || 30,
      mode: script.config.mode || 'uniform'
    },
    options
  );

  const metrics = new SSMS();

  const warnings: EngineWarnings = {
    engines: {}
  };

  const runnableScript = prepareScript(script, payload);

  const ee = new EventEmitter() as RunnerInstance;

  //
  // load engines:
  //
  const { loadedEngines: runnerEngines } = await loadEngines(
    runnableScript,
    ee,
    warnings
  );

  for (const e of runnerEngines) {
    if (
      e &&
      typeof e.init === 'function' &&
      e.init.constructor.name === 'AsyncFunction'
    ) {
      await e.init();
    }
  }

  const promise = new Promise<RunnerInstance>((resolve, _reject) => {
    ee.run = (contextVars) => {
      const runState: RunState = {
        pendingScenarios: 0,
        // pendingRequests: 0,
        compiledScenarios: null,
        scenarioEvents: null,
        picker: undefined,
        engines: runnerEngines,
        metrics: metrics
      };
      debug('run() with: %j', runnableScript);
      run(runnableScript, ee, opts, runState, contextVars);
    };

    ee.stop = async (_done: unknown) => {
      metrics.stop();
    };

    // FIXME: Warnings should be returned from this function instead along with
    // the event emitter. That will be a breaking change.
    ee.warnings = warnings;

    resolve(ee);
  });

  if (callback && typeof callback === 'function') {
    promise.then(callback.bind(null, null), callback);
  }

  return promise;
}

function run(
  script: Record<string, any>,
  ee: RunnerInstance,
  options: Record<string, any>,
  runState: RunState,
  contextVars?: Record<string, any> | null
) {
  const metrics = runState.metrics;
  const intermediates: PeriodMetrics[] = [];

  const phaser = createPhaser(script.config.phases);
  let _scenarioContext;

  phaser.on('arrival', (spec: PhaseSpec) => {
    if (runState.pendingScenarios >= (spec.maxVusers as number)) {
      metrics.counter('vusers.skipped', 1);
    } else {
      _scenarioContext = runScenario(
        script,
        metrics,
        runState,
        contextVars,
        options
      );
    }
  });
  phaser.on('phaseStarted', (spec) => {
    ee.emit('phaseStarted', spec);
  });
  phaser.on('phaseCompleted', (spec) => {
    ee.emit('phaseCompleted', spec);
  });
  phaser.on('done', () => {
    debug('All phases launched');

    const doneYet = setInterval(function checkIfDone() {
      if (runState.pendingScenarios === 0) {
        clearInterval(doneYet);

        metrics.aggregate(true);

        const totals = SSMS.pack(intermediates);

        ee.emit('done', totals);
      } else {
        debug('Pending scenarios: %s', runState.pendingScenarios);
      }
    }, 1000);
  });

  metrics.on('metricData', (_ts, periodData) => {
    const cloned = SSMS.deserializeMetrics(SSMS.serializeMetrics(periodData));
    intermediates.push(periodData);
    ee.emit('stats', cloned);
  });

  phaser.run();
}

function runScenario(
  script: Record<string, any>,
  metrics: SSMS,
  runState: RunState,
  contextVars: Record<string, any> | null | undefined,
  options: Record<string, any>
) {
  const start = process.hrtime();

  //
  // Compile scenarios if needed
  //
  if (!runState.compiledScenarios) {
    _.each(script.scenarios, (scenario: Record<string, any>) => {
      if (typeof scenario.weight === 'undefined') {
        scenario.weight = 1;
      } else {
        debug(`scenario ${scenario.name} weight = ${scenario.weight}`);
        const variableValues = Object.assign(
          datafileVariables(script),
          inlineVariables(script),
          { $processEnvironment: process.env }
        );

        const w = engineUtil.template(scenario.weight, {
          vars: variableValues
        });
        scenario.weight = Number.isNaN(parseInt(w, 10)) ? 0 : parseInt(w, 10);
        debug(
          `scenario ${scenario.name} weight has been set to ${scenario.weight}`
        );
      }
    });

    runState.picker = wl(script.scenarios);

    runState.scenarioEvents = new EventEmitter();
    runState.scenarioEvents.on('counter', (name: string, value: number) => {
      metrics.counter(name, value);
    });
    // TODO: Deprecate
    runState.scenarioEvents.on(
      'customStat',
      (stat: { stat: string; value: number }) => {
        metrics.summary(stat.stat, stat.value);
      }
    );
    runState.scenarioEvents.on('summary', (name: string, value: number) => {
      metrics.summary(name, value);
    });
    runState.scenarioEvents.on('histogram', (name: string, value: number) => {
      metrics.summary(name, value);
    });
    runState.scenarioEvents.on('rate', (name: string) => {
      metrics.rate(name);
    });
    runState.scenarioEvents.on('started', () => {
      runState.pendingScenarios++;
    });
    // TODO: Take an object so that it can have code, description etc
    runState.scenarioEvents.on('error', (errCode: string | number) => {
      metrics.counter(`errors.${errCode}`, 1);
    });

    runState.compiledScenarios = _.map(
      script.scenarios,
      (scenarioSpec: Record<string, any>, scenarioIndex: number) => {
        const name = scenarioSpec.engine || script.config.engine || 'http';
        // NOTE: pre-existing behavior: throws when an engine failed to
        // load (undefined entry in the engines list).
        const engine = runState.engines.find(
          (e) => (e as EngineInstance).__name === name
        );

        if (typeof engine === 'undefined') {
          const scenarioNameOrIndex = scenarioSpec.name || scenarioIndex;
          throw new Error(
            `Failed to run scenario "${scenarioNameOrIndex}": unknown engine "${name}". Did you forget to include it in "config.engines.${name}"?`
          );
        }

        return engine.createScenario(scenarioSpec, runState.scenarioEvents);
      }
    );
  }

  //default to weighted picked scenario
  // picker is always set by the compile block above on first arrival.
  let i = (runState.picker as () => [number, any])()[0];

  if (options.scenarioName) {
    let foundIndex: number | undefined;
    const foundScenario = script.scenarios.filter(
      (scenario: Record<string, any>, index: number) => {
        const hasScenarioByRegex = new RegExp(options.scenarioName).test(
          scenario.name
        );
        const hasScenarioByName = scenario.name === options.scenarioName;
        const hasScenario = hasScenarioByName || hasScenarioByRegex;

        if (hasScenario) {
          foundIndex = index;
        }

        return hasScenario;
      }
    );

    if (foundScenario?.length === 0) {
      throw new Error(
        `Scenario ${options.scenarioName} not found in script. Make sure your chosen scenario matches the one in your script exactly.`
      );
    } else if (foundScenario.length > 1) {
      throw new Error(
        `Multiple scenarios for ${options.scenarioName} found in script. Make sure you give unique names to your scenarios in your script.`
      );
    } else {
      debug(`Scenario ${options.scenarioName} found in script. running it!`);
      i = foundIndex as number;
    }
  }
  debug(
    'picking scenario %s (%s) weight = %s',
    i,
    script.scenarios[i].name,
    script.scenarios[i].weight
  );

  metrics.counter(`vusers.created_by_name.${script.scenarios[i].name || i}`, 1);
  metrics.counter('vusers.created', 1);

  const scenarioStartedAt = process.hrtime();
  const scenarioContext = createContext(script, contextVars, {
    scenario: script.scenarios[i]
  });

  const finish = process.hrtime(start);
  const runScenarioDelta = finish[0] * 1e9 + finish[1];
  debugPerf(
    'runScenarioDelta: %s',
    Math.round((runScenarioDelta / 1e6) * 100) / 100
  );
  (runState.compiledScenarios as ScenarioFn[])[i](
    scenarioContext,
    (err, _context) => {
      runState.pendingScenarios--;
      if (err) {
        debug(err);
        metrics.counter('vusers.failed', 1);
      } else {
        metrics.counter('vusers.failed', 0);
        metrics.counter('vusers.completed', 1);
        const scenarioFinishedAt = process.hrtime(scenarioStartedAt);
        const delta = scenarioFinishedAt[0] * 1e9 + scenarioFinishedAt[1];
        metrics.summary('vusers.session_length', delta / 1e6);
      }
    }
  );

  return scenarioContext;
}

function datafileVariables(
  script: Record<string, any>
): Record<string, unknown> {
  const result: Record<string, unknown> = {};
  if (script.config.payload) {
    _.each(script.config.payload, (el: Record<string, any>) => {
      if (!el.loadAll) {
        // Load individual fields from the CSV into VU context variables
        // If data = [] (i.e. the CSV file is empty, or only has headers and
        // skipHeaders = true), then row could = undefined
        const row = el.reader(el.data) || [];
        _.each(el.fields, (fieldName: string, j: number) => {
          result[fieldName] = row[j];
        });
      } else {
        if (typeof el.name !== 'undefined') {
          // Make the entire CSV available
          result[el.name] = el.reader(el.data);
        } else {
          console.log(
            'WARNING: loadAll is set to true but no name is provided for the CSV data'
          );
        }
      }
    });
  }

  return result;
}

function inlineVariables(script: Record<string, any>): Record<string, unknown> {
  const result: Record<string, unknown> = {};
  if (script.config.variables) {
    _.each(script.config.variables, (v: unknown, k: string) => {
      let val;
      if (_.isArray(v)) {
        val = _.sample(v);
      } else {
        val = v;
      }
      result[k] = val;
    });
  }
  return result;
}

/**
 * Create initial context for a scenario.
 */
function createContext(
  script: Record<string, any>,
  contextVars: Record<string, any> | null | undefined,
  additionalProperties: Record<string, any> = {}
) {
  //allow for additional properties to be passed in, but not override vars and funcs
  const additionalPropertiesWithoutOverride = _.omit(additionalProperties, [
    'vars',
    'funcs'
  ]);

  const INITIAL_CONTEXT: {
    vars: Record<string, any>;
    funcs: Record<string, (...args: any[]) => any>;
    [key: string]: any;
  } = {
    vars: Object.assign(
      {
        target: script.config.target,
        $environment: script._environment,
        $processEnvironment: process.env, // TODO: deprecate
        $env: process.env,
        $testId: global.artillery.testRunId
      },
      contextVars || {}
    ),
    funcs: {
      $randomNumber: $randomNumber,
      $randomString: $randomString,
      $template: (input: unknown) =>
        engineUtil.template(input, { vars: result.vars })
    },
    ...additionalPropertiesWithoutOverride
  };

  if (script._configPath) {
    INITIAL_CONTEXT.vars.$dirname = path.dirname(script._configPath);
  }
  if (script._scriptPath) {
    INITIAL_CONTEXT.vars.$scenarioFile = script._scriptPath;
  }
  const result = INITIAL_CONTEXT;

  // variables from payloads:
  const variableValues1 = datafileVariables(script);
  Object.assign(result.vars, variableValues1);
  // inline variables:
  const variableValues2 = inlineVariables(script);
  Object.assign(result.vars, variableValues2);

  result._uid = uuidv4();
  result.vars.$uuid = result._uid;

  return result;
}

//
// Generator functions for template strings:
//
function $randomNumber(min: number, max: number): number {
  return _.random(min, max);
}

function $randomString(length = 10) {
  let s = '';
  const alphabet =
    'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
  const alphabetLength = alphabet.length;

  while (s.length < length) {
    s += alphabet.charAt((Math.random() * alphabetLength) | 0);
  }

  return s;
}

async function handleScriptHook(
  hook: string,
  script: ScriptLike,
  hookEvents: { emit(event: string, ...args: any[]): unknown },
  contextVars: Record<string, any> = {}
) {
  if (!script[hook]) {
    return {};
  }

  const { loadedEngines: engines } = await loadEngines(script, hookEvents);

  for (const e of engines) {
    if (
      e &&
      typeof e.init === 'function' &&
      e.init.constructor.name === 'AsyncFunction'
    ) {
      await e.init();
    }
  }

  const ee = new EventEmitter();

  return new Promise((resolve, reject) => {
    ee.on('request', () => {
      hookEvents.emit(`${hook}TestRequest`);
    });
    ee.on('error', (error: unknown) => {
      hookEvents.emit(`${hook}TestError`, error);
    });

    const name = script[hook].engine || 'http';
    // NOTE: pre-existing behavior: throws when an engine failed to
    // load (undefined entry in the engines list).
    const engine = engines.find((e) => (e as EngineInstance).__name === name);

    if (typeof engine === 'undefined') {
      throw new Error(
        `Failed to run ${hook} hook: unknown engine "${name}". Did you forget to include it in "config.engines.${name}"?`
      );
    }
    const hookScenario = engine.createScenario(script[hook], ee);
    const hookContext = createContext(script, contextVars, {
      scenario: script[hook]
    });

    hookScenario(hookContext, (err, context) => {
      if (err) {
        debug(err);
        return reject(err);
      } else {
        return resolve(context.vars);
      }
    });
  });
}