// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License.

import {InferenceSession, InferenceSessionHandler, SessionHandler, Tensor, TRACE_FUNC_BEGIN, TRACE_FUNC_END} from 'onnxruntime-common';

import {SerializableInternalBuffer, TensorMetadata} from './proxy-messages';
import {copyFromExternalBuffer, createSession, endProfiling, releaseSession, run} from './proxy-wrapper';
import {isGpuBufferSupportedType} from './wasm-common';
import {loadFile} from './wasm-utils-load-file';

export const encodeTensorMetadata = (tensor: Tensor, getName: () => string): TensorMetadata => {
  switch (tensor.location) {
    case 'cpu':
      return [tensor.type, tensor.dims, tensor.data, 'cpu'];
    case 'gpu-buffer':
      return [tensor.type, tensor.dims, {gpuBuffer: tensor.gpuBuffer}, 'gpu-buffer'];
    default:
      throw new Error(`invalid data location: ${tensor.location} for ${getName()}`);
  }
};

export const decodeTensorMetadata = (tensor: TensorMetadata): Tensor => {
  switch (tensor[3]) {
    case 'cpu':
      return new Tensor(tensor[0], tensor[2], tensor[1]);
    case 'gpu-buffer': {
      const dataType = tensor[0];
      if (!isGpuBufferSupportedType(dataType)) {
        throw new Error(`not supported data type: ${dataType} for deserializing GPU tensor`);
      }
      const {gpuBuffer, download, dispose} = tensor[2];
      return Tensor.fromGpuBuffer(gpuBuffer, {dataType, dims: tensor[1], download, dispose});
    }
    default:
      throw new Error(`invalid data location: ${tensor[3]}`);
  }
};

export class OnnxruntimeWebAssemblySessionHandler implements InferenceSessionHandler {
  private sessionId: number;

  inputNames: string[];
  outputNames: string[];

  async fetchModelAndCopyToWasmMemory(path: string): Promise<SerializableInternalBuffer> {
    // fetch model from url and move to wasm heap.
    return copyFromExternalBuffer(await loadFile(path));
  }

  async loadModel(pathOrBuffer: string|Uint8Array, options?: InferenceSession.SessionOptions): Promise<void> {
    TRACE_FUNC_BEGIN();
    let model: Parameters<typeof createSession>[0];

    if (typeof pathOrBuffer === 'string') {
      if (typeof process !== 'undefined' && process.versions && process.versions.node) {
        // node
        model = await loadFile(pathOrBuffer);
      } else {
        // browser
        // fetch model and copy to wasm heap.
        model = await this.fetchModelAndCopyToWasmMemory(pathOrBuffer);
      }
    } else {
      model = pathOrBuffer;
    }

    [this.sessionId, this.inputNames, this.outputNames] = await createSession(model, options);
    TRACE_FUNC_END();
  }

  async dispose(): Promise<void> {
    return releaseSession(this.sessionId);
  }

  async run(feeds: SessionHandler.FeedsType, fetches: SessionHandler.FetchesType, options: InferenceSession.RunOptions):
      Promise<SessionHandler.ReturnType> {
    TRACE_FUNC_BEGIN();
    const inputArray: Tensor[] = [];
    const inputIndices: number[] = [];
    Object.entries(feeds).forEach(kvp => {
      const name = kvp[0];
      const tensor = kvp[1];
      const index = this.inputNames.indexOf(name);
      if (index === -1) {
        throw new Error(`invalid input '${name}'`);
      }
      inputArray.push(tensor);
      inputIndices.push(index);
    });

    const outputArray: Array<Tensor|null> = [];
    const outputIndices: number[] = [];
    Object.entries(fetches).forEach(kvp => {
      const name = kvp[0];
      const tensor = kvp[1];
      const index = this.outputNames.indexOf(name);
      if (index === -1) {
        throw new Error(`invalid output '${name}'`);
      }
      outputArray.push(tensor);
      outputIndices.push(index);
    });

    const inputs =
        inputArray.map((t, i) => encodeTensorMetadata(t, () => `input "${this.inputNames[inputIndices[i]]}"`));
    const outputs = outputArray.map(
        (t, i) => t ? encodeTensorMetadata(t, () => `output "${this.outputNames[outputIndices[i]]}"`) : null);

    const results = await run(this.sessionId, inputIndices, inputs, outputIndices, outputs, options);

    const resultMap: SessionHandler.ReturnType = {};
    for (let i = 0; i < results.length; i++) {
      resultMap[this.outputNames[outputIndices[i]]] = outputArray[i] ?? decodeTensorMetadata(results[i]);
    }
    TRACE_FUNC_END();
    return resultMap;
  }

  startProfiling(): void {
    // TODO: implement profiling
  }

  endProfiling(): void {
    void endProfiling(this.sessionId);
  }
}