/**
 * Copyright 2022 The MediaPipe Authors.
 *
 * 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 {InferenceCalculatorOptions} from '../../../calculators/tensor/inference_calculator_pb';
import {CalculatorGraphConfig} from '../../../framework/calculator_pb';
import {Acceleration} from '../../../tasks/cc/core/proto/acceleration_pb';
import {BaseOptions as BaseOptionsProto} from '../../../tasks/cc/core/proto/base_options_pb';
import {ExternalFile} from '../../../tasks/cc/core/proto/external_file_pb';
import {BaseOptions, TaskRunnerOptions} from '../../../tasks/web/core/task_runner_options';
import {createMediaPipeLib, FileLocator, GraphRunner, WasmMediaPipeConstructor} from '../../../web/graph_runner/graph_runner';
import {SupportModelResourcesGraphService} from '../../../web/graph_runner/register_model_resources_graph_service';

import {WasmFileset} from './wasm_fileset';

// Internal stream names for temporarily keeping memory alive, then freeing it.
const FREE_MEMORY_STREAM = 'free_memory';
const UNUSED_STREAM_SUFFIX = '_unused_out';

// tslint:disable-next-line:enforce-name-casing
const CachedGraphRunnerType = SupportModelResourcesGraphService(GraphRunner);

// The OSS JS API does not support the builder pattern.
// tslint:disable:jspb-use-builder-pattern

/**
 * An implementation of the GraphRunner that exposes the resource graph
 * service.
 */
export class CachedGraphRunner extends CachedGraphRunnerType {}

/**
 * Creates a new instance of a Mediapipe Task. Determines if SIMD is
 * supported and loads the relevant WASM binary.
 * @return A fully instantiated instance of `T`.
 */
export async function createTaskRunner<T extends TaskRunner>(
    type: WasmMediaPipeConstructor<T>,
    canvas: HTMLCanvasElement|OffscreenCanvas|null|undefined,
    fileset: WasmFileset, options: TaskRunnerOptions): Promise<T> {
  const fileLocator: FileLocator = {
    locateFile() {
      // The only file loaded with this mechanism is the Wasm binary
      return fileset.wasmBinaryPath.toString();
    }
  };

  const instance = await createMediaPipeLib(
      type, fileset.wasmLoaderPath, fileset.assetLoaderPath, canvas,
      fileLocator);
  await instance.setOptions(options);
  return instance;
}

/** Base class for all MediaPipe Tasks. */
export abstract class TaskRunner {
  protected abstract baseOptions: BaseOptionsProto;
  private processingErrors: Error[] = [];
  private latestOutputTimestamp = 0;
  private keepaliveNode?: CalculatorGraphConfig.Node;

  /**
   * Creates a new instance of a Mediapipe Task. Determines if SIMD is
   * supported and loads the relevant WASM binary.
   * @return A fully instantiated instance of `T`.
   */
  protected static async createInstance<T extends TaskRunner>(
      type: WasmMediaPipeConstructor<T>,
      canvas: HTMLCanvasElement|OffscreenCanvas|null|undefined,
      fileset: WasmFileset, options: TaskRunnerOptions): Promise<T> {
    return createTaskRunner(type, canvas, fileset, options);
  }

  /** @hideconstructor protected */
  constructor(protected readonly graphRunner: CachedGraphRunner) {
    // Disables the automatic render-to-screen code, which allows for pure
    // CPU processing.
    this.graphRunner.setAutoRenderToScreen(false);
  }

  /** Configures the task with custom options. */
  abstract setOptions(options: TaskRunnerOptions): Promise<void>;

  /**
   * Applies the current set of options, including optionally any base options
   * that have not been processed by the task implementation. The options are
   * applied synchronously unless a `modelAssetPath` is provided. This ensures
   * that for most use cases options are applied directly and immediately affect
   * the next inference.
   *
   * @param options The options for the task.
   * @param loadTfliteModel Whether to load the model specified in
   *     `options.baseOptions`.
   */
  protected applyOptions(options: TaskRunnerOptions, loadTfliteModel = true):
      Promise<void> {
    if (loadTfliteModel) {
      const baseOptions: BaseOptions = options.baseOptions || {};

      // Validate that exactly one model is configured
      if (options.baseOptions?.modelAssetBuffer &&
          options.baseOptions?.modelAssetPath) {
        throw new Error(
            'Cannot set both baseOptions.modelAssetPath and baseOptions.modelAssetBuffer');
      } else if (!(this.baseOptions.getModelAsset()?.hasFileContent() ||
                   this.baseOptions.getModelAsset()?.hasFileName() ||
                   options.baseOptions?.modelAssetBuffer ||
                   options.baseOptions?.modelAssetPath)) {
        throw new Error(
            'Either baseOptions.modelAssetPath or baseOptions.modelAssetBuffer must be set');
      }

      this.setAcceleration(baseOptions);
      if (baseOptions.modelAssetPath) {
        // We don't use `await` here since we want to apply most settings
        // synchronously.
        return fetch(baseOptions.modelAssetPath.toString())
            .then(response => {
              if (!response.ok) {
                throw new Error(`Failed to fetch model: ${
                    baseOptions.modelAssetPath} (${response.status})`);
              } else {
                return response.arrayBuffer();
              }
            })
            .then(buffer => {
              try {
                // Try to delete file as we cannot overwite an existing file
                // using our current API.
                this.graphRunner.wasmModule.FS_unlink('/model.dat');
              } catch {
              }
              // TODO: Consider passing the model to the graph as an
              // input side packet as this might reduce copies.
              this.graphRunner.wasmModule.FS_createDataFile(
                  '/', 'model.dat', new Uint8Array(buffer),
                  /* canRead= */ true, /* canWrite= */ false,
                  /* canOwn= */ false);
              this.setExternalFile('/model.dat');
              this.refreshGraph();
              this.onGraphRefreshed();
            });
      } else {
        this.setExternalFile(baseOptions.modelAssetBuffer);
      }
    }

    // If there is no model to download, we can apply the setting synchronously.
    this.refreshGraph();
    this.onGraphRefreshed();
    return Promise.resolve();
  }

  /** Appliest the current options to the MediaPipe graph. */
  protected abstract refreshGraph(): void;

  /**
   * Callback that gets invoked once a new graph configuration has been
   * applied.
   */
  protected onGraphRefreshed(): void {}

  /** Returns the current CalculatorGraphConfig. */
  protected getCalculatorGraphConfig(): CalculatorGraphConfig {
    let config: CalculatorGraphConfig|undefined;
    this.graphRunner.getCalculatorGraphConfig(binaryData => {
      config = CalculatorGraphConfig.deserializeBinary(binaryData);
    });
    if (!config) {
      throw new Error('Failed to retrieve CalculatorGraphConfig');
    }
    return config;
  }

  /**
   * Takes the raw data from a MediaPipe graph, and passes it to C++ to be run
   * over the video stream. Will replace the previously running MediaPipe graph,
   * if there is one.
   * @param graphData The raw MediaPipe graph data, either in binary
   *     protobuffer format (.binarypb), or else in raw text format (.pbtxt or
   *     .textproto).
   * @param isBinary This should be set to true if the graph is in
   *     binary format, and false if it is in human-readable text format.
   */
  protected setGraph(graphData: Uint8Array, isBinary: boolean): void {
    this.graphRunner.attachErrorListener((code, message) => {
      this.processingErrors.push(new Error(message));
    });

    // Enables use of our model resource caching graph service; we apply this to
    // every MediaPipe graph we run.
    this.graphRunner.registerModelResourcesGraphService();

    this.graphRunner.setGraph(graphData, isBinary);
    this.keepaliveNode = undefined;
    this.handleErrors();
  }

  /**
   * Forces all queued-up packets to be pushed through the MediaPipe graph as
   * far as possible, performing all processing until no more processing can be
   * done.
   */
  protected finishProcessing(): void {
    this.graphRunner.finishProcessing();
    this.handleErrors();
  }

  /*
   * Sets the latest output timestamp received from the graph (in ms).
   * Timestamps that are smaller than the currently latest output timestamp are
   * ignored.
   */
  protected setLatestOutputTimestamp(timestamp: number): void {
    this.latestOutputTimestamp =
        Math.max(this.latestOutputTimestamp, timestamp);
  }

  /**
   * Gets a syncthethic timestamp in ms that can be used to send data to the
   * next packet. The timestamp is one millisecond past the last timestamp
   * received from the graph.
   */
  protected getSynctheticTimestamp(): number {
    return this.latestOutputTimestamp + 1;
  }

  /** Throws the error from the error listener if an error was raised. */
  private handleErrors() {
    try {
      const errorCount = this.processingErrors.length;
      if (errorCount === 1) {
        // Re-throw error to get a more meaningful stacktrace
        throw new Error(this.processingErrors[0].message);
      } else if (errorCount > 1) {
        throw new Error(
            'Encountered multiple errors: ' +
            this.processingErrors.map(e => e.message).join(', '));
      }
    } finally {
      this.processingErrors = [];
    }
  }

  /** Configures the `externalFile` option */
  private setExternalFile(modelAssetPath?: string): void;
  private setExternalFile(modelAssetBuffer?: Uint8Array): void;
  private setExternalFile(modelAssetPathOrBuffer?: Uint8Array|string): void {
    const externalFile = this.baseOptions.getModelAsset() || new ExternalFile();
    if (typeof modelAssetPathOrBuffer === 'string') {
      externalFile.setFileName(modelAssetPathOrBuffer);
      externalFile.clearFileContent();
    } else if (modelAssetPathOrBuffer instanceof Uint8Array) {
      externalFile.setFileContent(modelAssetPathOrBuffer);
      externalFile.clearFileName();
    }
    this.baseOptions.setModelAsset(externalFile);
  }

  /** Configures the `acceleration` option. */
  private setAcceleration(options: BaseOptions) {
    let acceleration = this.baseOptions.getAcceleration();

    if (!acceleration) {
      // Create default instance for the initial configuration.
      acceleration = new Acceleration();
      acceleration.setTflite(new InferenceCalculatorOptions.Delegate.TfLite());
    }

    if ('delegate' in options) {
      if (options.delegate === 'GPU') {
        acceleration.setGpu(new InferenceCalculatorOptions.Delegate.Gpu());
      } else {
        acceleration.setTflite(
            new InferenceCalculatorOptions.Delegate.TfLite());
      }
    }

    this.baseOptions.setAcceleration(acceleration);
  }

  /**
   * Adds a node to the graph to temporarily keep certain streams alive.
   * NOTE: To use this call, PassThroughCalculator must be included in your wasm
   *     dependencies.
   */
  protected addKeepaliveNode(graphConfig: CalculatorGraphConfig) {
    this.keepaliveNode = new CalculatorGraphConfig.Node();
    this.keepaliveNode.setCalculator('PassThroughCalculator');
    this.keepaliveNode.addInputStream(FREE_MEMORY_STREAM);
    this.keepaliveNode.addOutputStream(
        FREE_MEMORY_STREAM + UNUSED_STREAM_SUFFIX);
    graphConfig.addInputStream(FREE_MEMORY_STREAM);
    graphConfig.addNode(this.keepaliveNode);
  }

  /** Adds streams to the keepalive node to be kept alive until callback. */
  protected keepStreamAlive(streamName: string) {
    this.keepaliveNode!.addInputStream(streamName);
    this.keepaliveNode!.addOutputStream(streamName + UNUSED_STREAM_SUFFIX);
  }

  /** Frees any streams being kept alive by the keepStreamAlive callback. */
  protected freeKeepaliveStreams() {
    this.graphRunner.addBoolToStream(
        true, FREE_MEMORY_STREAM, this.latestOutputTimestamp);
  }

  /** Closes and cleans up the resources held by this task. */
  close(): void {
    this.keepaliveNode = undefined;
    this.graphRunner.closeGraph();
  }
}