import { EventEmitter, ListenerFn } from "eventemitter3";

import { engineWorkerBlob } from "./workers/engineWorker";

import { deviceId, scanditEngineLocation, userLicenseKey } from "../index";
import { Barcode, BarcodeWASMResult } from "./barcode";
import { BrowserCompatibility } from "./browserCompatibility";
import { BrowserHelper } from "./browserHelper";
import { CustomError } from "./customError";
import { ImageSettings } from "./imageSettings";
import { Parser } from "./parser";
import { ParserField } from "./parserField";
import { ParserResult } from "./parserResult";
import { ScanResult } from "./scanResult";
import { ScanSettings } from "./scanSettings";
import { UnsupportedBrowserError } from "./unsupportedBrowserError";

/**
 * @hidden
 */
type EventName = "ready" | "licenseFeaturesReady" | "newScanSettings";

/**
 * @hidden
 */
class ScannerEventEmitter extends EventEmitter<string> {}

/**
 * A low-level scanner interacting with the external Scandit Engine library.
 * Used to set up scan / image settings and to process single image frames.
 *
 * The loading of the external Scandit Engine library which takes place on creation can take some time,
 * the [[on]] method targeting the [[ready]] event can be used to set up a listener function to be called when the
 * library is loaded and the [[isReady]] method can return the current status. The scanner will be ready to start
 * scanning when the library is fully loaded.
 *
 * In the special case where a single [[Scanner]] instance is shared between multiple active [[BarcodePicker]]
 * instances, the fairness in resource allocation for processing images between the different pickers is not guaranteed.
 */
export class Scanner {
  private readonly engineWorker: Worker;
  private readonly eventEmitter: ScannerEventEmitter;

  private scanSettings: ScanSettings;
  private imageSettings?: ImageSettings;
  private workerParseRequestId: number;
  private workerScanRequestId: number;
  private workerScanQueueLength: number;
  private isReadyToWork: boolean;
  private licenseFeatures?: object;
  private imageDataConversionContext?: CanvasRenderingContext2D;

  /**
   * Create a Scanner instance.
   *
   * It is required to having configured the library via [[configure]] before this object can be created.
   *
   * Before processing an image the relative settings must also have been set.
   *
   * If the library has not been correctly configured yet a `LibraryNotConfiguredError` error is thrown.
   *
   * If a browser is incompatible a `UnsupportedBrowserError` error is thrown.
   *
   * @param scanSettings <div class="tsd-signature-symbol">Default =&nbsp;new ScanSettings()</div>
   * The configuration object for scanning options.
   * @param imageSettings <div class="tsd-signature-symbol">Default =&nbsp;undefined</div>
   * The configuration object to define the properties of an image to be scanned.
   */
  constructor({
    scanSettings = new ScanSettings(),
    imageSettings
  }: {
    scanSettings?: ScanSettings;
    imageSettings?: ImageSettings;
  } = {}) {
    const browserCompatibility: BrowserCompatibility = BrowserHelper.checkBrowserCompatibility();
    if (!browserCompatibility.scannerSupport) {
      throw new UnsupportedBrowserError(browserCompatibility);
    }
    if (userLicenseKey == null) {
      throw new CustomError({
        name: "LibraryNotConfiguredError",
        message: "The library has not correctly been configured yet, please call 'configure' with valid parameters"
      });
    }

    this.isReadyToWork = false;
    this.workerScanQueueLength = 0;

    this.engineWorker = new Worker(URL.createObjectURL(engineWorkerBlob));
    this.engineWorker.onmessage = this.engineWorkerOnMessage.bind(this);
    this.engineWorker.postMessage({
      type: "load-library",
      deviceId,
      libraryLocation: scanditEngineLocation,
      path: self.location.pathname,
      deviceModelName: BrowserHelper.userAgentInfo.getDevice().model,
      uaBrowserName: BrowserHelper.userAgentInfo.getBrowser().name
    });

    this.eventEmitter = new EventEmitter();
    this.workerParseRequestId = 0;
    this.workerScanRequestId = 0;

    this.applyLicenseKey(userLicenseKey);
    this.applyScanSettings(scanSettings);
    if (imageSettings != null) {
      this.applyImageSettings(imageSettings);
    }
  }

  /**
   * Stop the internal `WebWorker` and destroy the scanner itself; ensuring complete cleanup.
   *
   * This method should be called after you don't plan to use the scanner anymore,
   * before the object is automatically cleaned up by JavaScript.
   * The barcode picker must not be used in any way after this call.
   */
  public destroy(): void {
    if (this.engineWorker != null) {
      this.engineWorker.terminate();
    }
    this.eventEmitter.removeAllListeners();
  }

  /**
   * Apply a new set of scan settings to the scanner (replacing old settings).
   *
   * @param scanSettings The scan configuration object to be applied to the scanner.
   * @returns The updated [[Scanner]] object.
   */
  public applyScanSettings(scanSettings: ScanSettings): Scanner {
    this.scanSettings = scanSettings;
    this.engineWorker.postMessage({
      type: "settings",
      settings: this.scanSettings.toJSONString()
    });
    this.eventEmitter.emit("newScanSettings", this.scanSettings);

    return this;
  }

  /**
   * Apply a new set of image settings to the scanner (replacing old settings).
   *
   * @param imageSettings The image configuration object to be applied to the scanner.
   * @returns The updated [[Scanner]] object.
   */
  public applyImageSettings(imageSettings: ImageSettings): Scanner {
    this.imageSettings = imageSettings;
    this.engineWorker.postMessage({
      type: "image-settings",
      imageSettings
    });

    return this;
  }

  /**
   * Clear the scanner session.
   *
   * This removes all recognized barcodes from the scanner session and allows them to be scanned again in case a custom
   * *codeDuplicateFilter* was set in the [[ScanSettings]].
   *
   * @returns The updated [[Scanner]] object.
   */
  public clearSession(): Scanner {
    this.engineWorker.postMessage({
      type: "clear-session"
    });

    return this;
  }

  /**
   * Process a given image using the previously set scanner and image settings,
   * recognizing codes and retrieving the result as a list of barcodes (if any).
   *
   * Multiple requests done without waiting for previous results will be queued and handled in order.
   *
   * If *highQualitySingleFrameMode* is enabled the image will be processed with really accurate internal settings,
   * resulting in much slower but more precise scanning results. This should be used only for single images not part
   * of a continuous video stream.
   *
   * Passing image data as a *Uint8ClampedArray* is the fastest option, passing a *HTMLImageElement* will incur
   * in additional operations.
   *
   * Depending on the current image settings, given *imageData* and scanning execution, any of the following errors
   * could be the rejected result of the returned promise:
   * - `NoImageSettings`
   * - `ImageSettingsDataMismatch`
   * - `ScanditEngineError`
   *
   * @param imageData The image data given as byte array or image element, complying with the previously set
   * image settings.
   * @param highQualitySingleFrameMode Whether to process the image as a high quality single frame.
   * @returns A promise resolving to the [[ScanResult]] object.
   */
  public processImage(
    imageData: Uint8ClampedArray | HTMLImageElement,
    highQualitySingleFrameMode: boolean = false
  ): Promise<ScanResult> {
    if (this.imageSettings == null) {
      return Promise.reject(
        new CustomError({ name: "NoImageSettings", message: "No image settings set up in the scanner" })
      );
    }

    if (imageData instanceof HTMLImageElement) {
      if (this.imageDataConversionContext == null) {
        this.imageDataConversionContext = <CanvasRenderingContext2D>document.createElement("canvas").getContext("2d");
      }
      this.imageDataConversionContext.canvas.width = imageData.naturalWidth;
      this.imageDataConversionContext.canvas.height = imageData.naturalHeight;
      this.imageDataConversionContext.drawImage(imageData, 0, 0, imageData.naturalWidth, imageData.naturalHeight);
      imageData = this.imageDataConversionContext.getImageData(0, 0, imageData.naturalWidth, imageData.naturalHeight)
        .data;
    }

    let channels: number;
    switch (this.imageSettings.format.valueOf()) {
      case ImageSettings.Format.GRAY_8U:
        channels = 1;
        break;
      case ImageSettings.Format.RGB_8U:
        channels = 3;
        break;
      case ImageSettings.Format.RGBA_8U:
        channels = 4;
        break;
      default:
        channels = 1;
        break;
    }

    if (this.imageSettings.width * this.imageSettings.height * channels !== imageData.length) {
      return Promise.reject(
        new CustomError({
          name: "ImageSettingsDataMismatch",
          message: "The provided image data doesn't match the previously set image settings"
        })
      );
    }

    this.workerScanRequestId++;
    this.workerScanQueueLength++;

    const originalImageData: Uint8ClampedArray = imageData.slice();

    return new Promise<ScanResult>((resolve, reject) => {
      const workResultEvent: string = `workResult-${this.workerScanRequestId}`;
      const workErrorEvent: string = `workError-${this.workerScanRequestId}`;
      this.eventEmitter.once(workResultEvent, (workResult: { scanResult: BarcodeWASMResult[] }) => {
        this.eventEmitter.removeAllListeners(workErrorEvent);
        resolve(
          new ScanResult(workResult.scanResult.map(Barcode.createFromWASMResult), originalImageData, <ImageSettings>(
            this.imageSettings
          ))
        );
      });
      this.eventEmitter.once(workErrorEvent, (error: { errorCode: number; errorMessage: string }) => {
        console.error(`Scandit Engine error (${error.errorCode}):`, error.errorMessage);
        this.eventEmitter.removeAllListeners(workResultEvent);
        const errorObject: Error = new CustomError({
          name: "ScanditEngineError",
          message: `${error.errorMessage} (${error.errorCode})`
        });
        reject(errorObject);
      });
      this.engineWorker.postMessage(
        {
          type: "work",
          requestId: this.workerScanRequestId,
          data: <Uint8ClampedArray>imageData,
          highQualitySingleFrameMode
        },
        [(<Uint8ClampedArray>imageData).buffer]
      );
    });
  }

  /**
   * @returns Whether the scanner is currently busy processing an image.
   */
  public isBusyProcessing(): boolean {
    return this.workerScanQueueLength !== 0;
  }

  /**
   * @returns Whether the scanner has loaded the external Scandit Engine library and is ready to scan.
   */
  public isReady(): boolean {
    return this.isReadyToWork;
  }

  /**
   * Add the listener function to the listeners array for an event.
   *
   * No checks are made to see if the listener has already been added.
   * Multiple calls passing the same listener will result in the listener being added, and called, multiple times.
   *
   * @param eventName The name of the event to listen to.
   * @param listener The listener function.
   * @returns The updated [[Scanner]] object.
   */
  // tslint:disable-next-line:bool-param-default
  public on(eventName: EventName, listener: ListenerFn): Scanner;
  /**
   * Add the listener function to the listeners array for the [[ready]] event, fired only once when the external
   * Scandit Engine library has been loaded and the scanner can thus start to scan barcodes.
   * If the external Scandit Engine library has already been loaded the listener is called immediately.
   *
   * No checks are made to see if the listener has already been added.
   * Multiple calls passing the same listener will result in the listener being added, and called, multiple times.
   *
   * @param eventName The name of the event to listen to.
   * @param listener The listener function.
   * @returns The updated [[Scanner]] object.
   */
  public on(eventName: "ready", listener: () => void): Scanner;
  public on(eventName: EventName, listener: ListenerFn): Scanner {
    if (eventName === "ready") {
      if (this.isReadyToWork) {
        listener();
      } else {
        this.eventEmitter.once(eventName, listener, this);
      }
    } else if (eventName === "licenseFeaturesReady") {
      if (this.licenseFeatures != null) {
        listener(this.licenseFeatures);
      } else {
        this.eventEmitter.once(eventName, listener, this);
      }
    } else {
      this.eventEmitter.on(eventName, listener, this);
    }

    return this;
  }

  /**
   * Add the listener function to the listeners array for the [[ready]] event, fired only once when the external
   * Scandit Engine library has been loaded and the scanner can thus start to scan barcodes.
   * If the external Scandit Engine library has already been loaded the listener is called immediately.
   *
   * No checks are made to see if the listener has already been added.
   * Multiple calls passing the same listener will result in the listener being added, and called, multiple times.
   *
   * @deprecated Use the [[on]] method instead.
   *
   * @param listener The listener function.
   * @returns The updated [[Scanner]] object.
   */
  public onReady(listener: () => void): Scanner {
    console.warn(
      "The onReady(<listener>) method is deprecated and will be removed in the next major library version." +
        'Please use on("ready", <listener>) instead.'
    );

    return this.on("ready", listener);
  }

  /**
   * *See the [[on]] method.*
   *
   * @param eventName The name of the event to listen to.
   * @param listener The listener function.
   * @returns The updated [[Scanner]] object.
   */
  public addListener(eventName: EventName, listener: ListenerFn): Scanner {
    return this.on(eventName, listener);
  }

  /**
   * Create a new parser object.
   *
   * @param dataFormat The format of the input data for the parser.
   * @returns The newly created parser.
   */
  public createParserForFormat(dataFormat: Parser.DataFormat): Parser {
    return new Parser(this, dataFormat);
  }

  /**
   * Return the current image settings.
   *
   * Note that modifying this object won't directly apply these settings: the [[applyImageSettings]] method must be
   * called with the updated object.
   *
   * @returns The current image settings.
   */
  public getImageSettings(): ImageSettings | undefined {
    return this.imageSettings;
  }

  /**
   * Return the current scan settings.
   *
   * Note that modifying this object won't directly apply these settings: the [[applyScanSettings]] method must be
   * called with the updated object.
   *
   * @returns The current scan settings.
   */
  public getScanSettings(): ScanSettings {
    return this.scanSettings;
  }

  /**
   * @hidden
   *
   * Process a given string using the Scandit Parser library,
   * parsing the data in the given format and retrieving the result as a [[ParserResult]] object.
   *
   * Multiple requests done without waiting for previous results will be queued and handled in order.
   *
   * If parsing of the data fails the returned promise is rejected with a `ScanditEngineError` error.
   *
   * @param dataFormat The format of the given data.
   * @param dataString The string containing the data to be parsed.
   * @param options Options for the specific data format parser.
   * @returns A promise resolving to the [[ParserResult]] object.
   */
  public parseString(dataFormat: Parser.DataFormat, dataString: string, options?: object): Promise<ParserResult> {
    this.workerParseRequestId++;

    return new Promise<ParserResult>((resolve, reject) => {
      const parseStringResultEvent: string = `parseStringResult-${this.workerParseRequestId}`;
      const parseStringErrorEvent: string = `parseStringError-${this.workerParseRequestId}`;
      this.eventEmitter.once(parseStringResultEvent, (result: string) => {
        this.eventEmitter.removeAllListeners(parseStringErrorEvent);
        const parserResult: ParserResult = {
          jsonString: result,
          fields: [],
          fieldsByName: {}
        };
        (<ParserField[]>JSON.parse(result)).forEach(parserField => {
          parserResult.fields.push(parserField);
          parserResult.fieldsByName[parserField.name] = parserField;
        });
        resolve(parserResult);
      });
      this.eventEmitter.once(parseStringErrorEvent, (error: { errorCode: number; errorMessage: string }) => {
        console.error(`Scandit Engine error (${error.errorCode}):`, error.errorMessage);
        this.eventEmitter.removeAllListeners(parseStringResultEvent);
        const errorObject: Error = new CustomError({
          name: "ScanditEngineError",
          message: `${error.errorMessage} (${error.errorCode})`
        });
        reject(errorObject);
      });
      this.engineWorker.postMessage({
        type: "parse-string",
        requestId: this.workerParseRequestId,
        dataFormat,
        dataString,
        options: options == null ? "{}" : JSON.stringify(options)
      });
    });
  }

  /**
   * @hidden
   *
   * Add the listener function to the listeners array for the "licenseFeaturesReady" event, fired only once
   * when the external Scandit Engine library has verified and loaded the license key and parsed its features.
   * If the license features are already available the listener is called immediately.
   *
   * No checks are made to see if the listener has already been added.
   * Multiple calls passing the same listener will result in the listener being added, and called, multiple times.
   *
   * @param listener The listener function, which will be invoked with a *licenseFeatures* object.
   * @returns The updated [[Scanner]] object.
   */
  public onLicenseFeaturesReady(listener: (licenseFeatures: object) => void): Scanner {
    return this.on("licenseFeaturesReady", listener);
  }

  /**
   * @hidden
   *
   * Add the listener function to the listeners array for the "newScanSettings" event, fired when new a new
   * [[ScanSettings]] object is applied via the [[applyScanSettings]] method.
   *
   * No checks are made to see if the listener has already been added.
   * Multiple calls passing the same listener will result in the listener being added, and called, multiple times.
   *
   * @param listener The listener function, which will be invoked with a [[ScanSettings]] object.
   * @returns The updated [[Scanner]] object.
   */
  public onNewScanSettings(listener: (scanSettings: ScanSettings) => void): Scanner {
    return this.on("newScanSettings", listener);
  }

  /**
   * @hidden
   *
   * Remove the specified listener from the given event's listener array.
   *
   * @param eventName The name of the event from which to remove the listener.
   * @param listener The listener function to be removed.
   * @returns The updated [[Scanner]] object.
   */
  public removeListener(eventName: string, listener: ListenerFn): Scanner {
    this.eventEmitter.removeListener(eventName, listener);

    return this;
  }

  private applyLicenseKey(licenseKey: string): Scanner {
    this.engineWorker.postMessage({
      type: "license-key",
      licenseKey
    });

    return this;
  }

  private engineWorkerOnMessage(ev: MessageEvent): void {
    // tslint:disable:max-union-size
    const data:
      | ["status", string]
      | ["license-features", object]
      | ["work-result", { requestId: number; result: { scanResult: BarcodeWASMResult[] } }]
      | ["work-error", { requestId: number; error: { errorCode: number; errorMessage: string } }]
      | ["parse-string-result", { requestId: number; result: string }]
      | ["parse-string-error", { requestId: number; error: { errorCode: number; errorMessage: string } }] = ev.data;
    // tslint:enable:max-union-size

    if (data[0] === "status" && data[1] === "ready") {
      this.isReadyToWork = true;
      this.eventEmitter.emit("ready");
    } else if (data[1] != null) {
      if (data[0] === "license-features") {
        this.licenseFeatures = data[1];
        this.eventEmitter.emit("licenseFeaturesReady", this.licenseFeatures);
      } else if (data[0] === "work-result") {
        this.eventEmitter.emit(`workResult-${data[1].requestId}`, data[1].result);
        this.workerScanQueueLength--;
      } else if (data[0] === "work-error") {
        this.eventEmitter.emit(`workError-${data[1].requestId}`, data[1].error);
        this.workerScanQueueLength--;
      } else if (data[0] === "parse-string-result") {
        this.eventEmitter.emit(`parseStringResult-${data[1].requestId}`, data[1].result);
      } else if (data[0] === "parse-string-error") {
        this.eventEmitter.emit(`parseStringError-${data[1].requestId}`, data[1].error);
      }
    }
  }
}

// istanbul ignore next
export namespace Scanner {
  /**
   * Fired when the external Scandit Engine library has been loaded and the scanner can thus start to scan barcodes.
   *
   * @asMemberOf Scanner
   * @event
   */
  // @ts-ignore
  declare function ready(): void;
  /**
   * @hidden
   *
   * Fired when the external Scandit Engine library has verified and loaded the license key and parsed its features.
   *
   * @asMemberOf Scanner
   * @event
   * @param licenseFeatures The features of the used license key.
   */
  // @ts-ignore
  // declare function licenseFeaturesReady(licenseFeatures: any): void;
  /**
   * @hidden
   *
   * Fired when new a new [[ScanSettings]] object is applied via the [[applyScanSettings]] method.
   *
   * @asMemberOf Scanner
   * @event
   * @param newScanSettings The features of the used license key.
   */
  // @ts-ignore
  // declare function newScanSettings(newScanSettings: any): void;
}