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

import {WebGpuBackend} from '../backend-webgpu';
import {LOG_DEBUG} from '../log';

import {GpuData, GpuDataId, GpuDataType} from './types';

/**
 * manages GpuDataId -> GpuBuffer
 */
export interface GpuDataManager {
  /**
   * copy data from CPU to GPU.
   */
  upload(id: GpuDataId, data: Uint8Array): void;
  /**
   * copy data from GPU to GPU.
   */
  memcpy(sourceId: GpuDataId, destinationId: GpuDataId): void;
  /**
   * create new data on GPU.
   */
  create(size: number, usage?: number): GpuData;
  /**
   * get GPU data by ID.
   */
  get(id: GpuDataId): GpuData|undefined;
  /**
   * release the data on GPU by ID.
   *
   * @return size of the data released
   */
  release(id: GpuDataId): number;
  /**
   * copy data from GPU to CPU.
   */
  download(id: GpuDataId, getTargetBuffer: () => Uint8Array): Promise<void>;

  /**
   * refresh the buffers that marked for release.
   *
   * when release() is called, the buffer is not released immediately. this is because we need to wait for the commands
   * to be submitted to the GPU. this function is called after the commands are submitted so that the buffers can be
   * actually released.
   */
  refreshPendingBuffers(): void;

  /**
   * register an external buffer for IO Binding. If the buffer is already registered, return the existing GPU data ID.
   *
   * GPU data manager only manages a mapping between the buffer and the GPU data ID. It will not manage the lifecycle of
   * the external buffer.
   */
  registerExternalBuffer(buffer: GPUBuffer, originalSize: number, previousBuffer?: GPUBuffer): number;

  /**
   * unregister an external buffer for IO Binding.
   */
  unregisterExternalBuffer(buffer: GPUBuffer): void;

  /**
   * destroy all gpu buffers.
   */
  dispose(): void;

  /**
   * release session related data.
   * @param sessionId - specify the session ID.
   */
  onReleaseSession(sessionId: number): void;
}

interface StorageCacheValue {
  gpuData: GpuData;
  originalSize: number;
}

/**
 * normalize the buffer size so that it fits the 128-bits (16 bytes) alignment.
 */
const calcNormalizedBufferSize = (size: number) => Math.ceil(size / 16) * 16;

let guid = 1;
const createNewGpuDataId = () => guid++;

/**
 * exported standard download function. This function is used by the session to download the data from GPU, and also by
 * factory to create GPU tensors with the capacity of downloading data from GPU.
 *
 * @param backend - the WebGPU backend
 * @param gpuBuffer - the GPU buffer to download
 * @param originalSize - the original size of the data
 * @param getTargetBuffer - optional. If provided, the data will be copied to the target buffer. Otherwise, a new buffer
 * will be created and returned.
 */
export const downloadGpuData =
    async(backend: WebGpuBackend, gpuBuffer: GPUBuffer, originalSize: number, getTargetBuffer?: () => Uint8Array):
        Promise<Uint8Array> => {
          const bufferSize = calcNormalizedBufferSize(originalSize);
          const gpuReadBuffer = backend.device.createBuffer(
              // eslint-disable-next-line no-bitwise
              {size: bufferSize, usage: GPUBufferUsage.COPY_DST | GPUBufferUsage.MAP_READ});
          try {
            const commandEncoder = backend.getCommandEncoder();
            backend.endComputePass();
            commandEncoder.copyBufferToBuffer(
                gpuBuffer /* source buffer */, 0 /* source offset */, gpuReadBuffer /* destination buffer */,
                0 /* destination offset */, bufferSize /* size */
            );
            backend.flush();

            await gpuReadBuffer.mapAsync(GPUMapMode.READ);

            const arrayBuffer = gpuReadBuffer.getMappedRange();
            if (getTargetBuffer) {
              // if we already have a CPU buffer to accept the data, no need to clone the ArrayBuffer.
              const targetBuffer = getTargetBuffer();
              targetBuffer.set(new Uint8Array(arrayBuffer, 0, originalSize));
              return targetBuffer;
            } else {
              // the mapped ArrayBuffer will be released when the GPU buffer is destroyed. Need to clone the
              // ArrayBuffer.
              return new Uint8Array(arrayBuffer.slice(0, originalSize));
            }
          } finally {
            gpuReadBuffer.destroy();
          }
        };

class GpuDataManagerImpl implements GpuDataManager {
  // GPU Data ID => GPU Data ( storage buffer )
  private storageCache: Map<GpuDataId, StorageCacheValue>;

  // pending buffers for uploading ( data is unmapped )
  private buffersForUploadingPending: GPUBuffer[];
  // pending buffers for computing
  private buffersPending: GPUBuffer[];

  // The reusable storage buffers for computing.
  private freeBuffers: Map<number, GPUBuffer[]>;
  // The reusable uniform buffers
  private freeUniformBuffers: Map<number, GPUBuffer[]>;

  // The external buffers registered users for IO Binding.
  private externalBuffers: Map<GPUBuffer, GpuDataId>;

  // The pendingBuffers for capture graph.
  // a SessionID -> GPUBuffer[] mapping.
  private capturedPendingBuffers: Map<number, GPUBuffer[]>;

  constructor(private backend: WebGpuBackend) {
    this.storageCache = new Map();
    this.freeBuffers = new Map();
    this.freeUniformBuffers = new Map();
    this.buffersForUploadingPending = [];
    this.buffersPending = [];
    this.externalBuffers = new Map();
    this.capturedPendingBuffers = new Map();
  }

  upload(id: GpuDataId, data: Uint8Array): void {
    const srcArrayBuffer = data.buffer;
    const srcOffset = data.byteOffset;
    const srcLength = data.byteLength;
    const size = calcNormalizedBufferSize(srcLength);

    // get destination gpu buffer
    const gpuDataCache = this.storageCache.get(id);
    if (!gpuDataCache) {
      throw new Error('gpu data for uploading does not exist');
    }
    if (gpuDataCache.originalSize !== srcLength) {
      throw new Error(`inconsistent data size. gpu data size=${gpuDataCache.originalSize}, data size=${srcLength}`);
    }

    // create gpu buffer
    const gpuBufferForUploading = this.backend.device.createBuffer(
        // eslint-disable-next-line no-bitwise
        {mappedAtCreation: true, size, usage: GPUBufferUsage.MAP_WRITE | GPUBufferUsage.COPY_SRC});

    // copy (upload) data
    const arrayBuffer = gpuBufferForUploading.getMappedRange();
    new Uint8Array(arrayBuffer).set(new Uint8Array(srcArrayBuffer, srcOffset, srcLength));
    gpuBufferForUploading.unmap();


    // GPU copy
    const commandEncoder = this.backend.getCommandEncoder();
    this.backend.endComputePass();
    commandEncoder.copyBufferToBuffer(gpuBufferForUploading, 0, gpuDataCache.gpuData.buffer, 0, size);

    LOG_DEBUG('verbose', () => `[WebGPU] GpuDataManager.upload(id=${id})`);

    this.buffersForUploadingPending.push(gpuBufferForUploading);
  }

  memcpy(sourceId: GpuDataId, destinationId: GpuDataId): void {
    // get source gpu buffer
    const sourceGpuDataCache = this.storageCache.get(sourceId);
    if (!sourceGpuDataCache) {
      throw new Error('source gpu data for memcpy does not exist');
    }
    // get destination gpu buffer
    const destinationGpuDataCache = this.storageCache.get(destinationId);
    if (!destinationGpuDataCache) {
      throw new Error('destination gpu data for memcpy does not exist');
    }
    if (sourceGpuDataCache.originalSize !== destinationGpuDataCache.originalSize) {
      throw new Error('inconsistent source and destination gpu data size');
    }
    const size = calcNormalizedBufferSize(sourceGpuDataCache.originalSize);

    // GPU copy
    const commandEncoder = this.backend.getCommandEncoder();
    this.backend.endComputePass();
    commandEncoder.copyBufferToBuffer(
        sourceGpuDataCache.gpuData.buffer, 0, destinationGpuDataCache.gpuData.buffer, 0, size);
  }

  registerExternalBuffer(buffer: GPUBuffer, originalSize: number, previousBuffer?: GPUBuffer): number {
    let id: number|undefined;
    if (previousBuffer) {
      id = this.externalBuffers.get(previousBuffer);
      if (id === undefined) {
        throw new Error('previous buffer is not registered');
      }
      if (buffer === previousBuffer) {
        LOG_DEBUG(
            'verbose',
            () => `[WebGPU] GpuDataManager.registerExternalBuffer(size=${originalSize}) => id=${
                id}, buffer is the same, skip.`);
        return id;
      } else if (this.backend.capturedCommandList.has(this.backend.currentSessionId!)) {
        throw new Error(`Registering a different external buffer under graph capture mode is not supported yet.
             Please use the previous external buffer!`);
      }
      this.externalBuffers.delete(previousBuffer);
    } else {
      id = createNewGpuDataId();
    }

    this.storageCache.set(id, {gpuData: {id, type: GpuDataType.default, buffer}, originalSize});
    this.externalBuffers.set(buffer, id);
    LOG_DEBUG(
        'verbose',
        () => `[WebGPU] GpuDataManager.registerExternalBuffer(size=${originalSize}) => id=${id}, registered.`);
    return id;
  }

  unregisterExternalBuffer(buffer: GPUBuffer): void {
    const id = this.externalBuffers.get(buffer);
    if (id !== undefined) {
      this.storageCache.delete(id);
      this.externalBuffers.delete(buffer);
      LOG_DEBUG('verbose', () => `[WebGPU] GpuDataManager.unregisterExternalBuffer() => id=${id}`);
    }
  }

  // eslint-disable-next-line no-bitwise
  create(size: number, usage = GPUBufferUsage.STORAGE | GPUBufferUsage.COPY_SRC | GPUBufferUsage.COPY_DST): GpuData {
    const bufferSize = calcNormalizedBufferSize(size);

    let gpuBuffer;
    // Currently, only storage buffers are reused.
    // eslint-disable-next-line no-bitwise
    const isStorage = (usage & GPUBufferUsage.STORAGE) === GPUBufferUsage.STORAGE;
    // eslint-disable-next-line no-bitwise
    const isUniform = (usage & GPUBufferUsage.UNIFORM) === GPUBufferUsage.UNIFORM;
    if (isStorage || isUniform) {
      const freeBuffers = isStorage ? this.freeBuffers : this.freeUniformBuffers;
      let buffers = freeBuffers.get(bufferSize);
      if (!buffers) {
        buffers = [];
        freeBuffers.set(bufferSize, buffers);
      }
      if (buffers.length > 0) {
        gpuBuffer = buffers.pop() as GPUBuffer;
      } else {
        // create gpu buffer
        gpuBuffer = this.backend.device.createBuffer({size: bufferSize, usage});
      }
    } else {
      // create gpu buffer
      gpuBuffer = this.backend.device.createBuffer({size: bufferSize, usage});
    }

    const gpuData = {id: createNewGpuDataId(), type: GpuDataType.default, buffer: gpuBuffer};
    this.storageCache.set(gpuData.id, {gpuData, originalSize: size});

    LOG_DEBUG('verbose', () => `[WebGPU] GpuDataManager.create(size=${size}) => id=${gpuData.id}`);
    return gpuData;
  }

  get(id: GpuDataId): GpuData|undefined {
    return this.storageCache.get(id)?.gpuData;
  }

  release(id: GpuDataId): number {
    const cachedData = this.storageCache.get(id);
    if (!cachedData) {
      throw new Error('releasing data does not exist');
    }

    LOG_DEBUG('verbose', () => `[WebGPU] GpuDataManager.release(id=${id}), gpuDataId=${cachedData.gpuData.id}`);

    this.storageCache.delete(id);
    this.buffersPending.push(cachedData.gpuData.buffer);
    // cachedData.gpuData.buffer.destroy();

    return cachedData.originalSize;
  }

  async download(id: GpuDataId, getTargetBuffer: () => Uint8Array): Promise<void> {
    const cachedData = this.storageCache.get(id);
    if (!cachedData) {
      throw new Error('data does not exist');
    }

    await downloadGpuData(this.backend, cachedData.gpuData.buffer, cachedData.originalSize, getTargetBuffer);
  }

  refreshPendingBuffers(): void {
    for (const buffer of this.buffersForUploadingPending) {
      // upload buffer is only useful in the session creation time. So we don't need to reuse them in session running.
      buffer.destroy();
    }
    this.buffersForUploadingPending = [];

    if (this.buffersPending.length === 0) {
      return;
    }

    if (this.backend.sessionStatus === 'default') {
      for (const buffer of this.buffersPending) {
        // eslint-disable-next-line no-bitwise
        if ((buffer.usage & GPUBufferUsage.STORAGE) === GPUBufferUsage.STORAGE) {
          // Put the pending buffer to freeBuffers list instead of really destroying it for buffer reusing.
          this.freeBuffers.get(buffer.size)!.push(buffer);
          // eslint-disable-next-line no-bitwise
        } else if ((buffer.usage & GPUBufferUsage.UNIFORM) === GPUBufferUsage.UNIFORM) {
          // Put the pending buffer to freeUniformBuffers list instead of really destroying it for buffer reusing.
          this.freeUniformBuffers.get(buffer.size)!.push(buffer);
        } else {
          buffer.destroy();
        }
      }
      this.buffersPending = [];
    } else {
      // Don't release intermediate tensors in non-default mode.
      // TODO: reuse the storage buffers in non-default mode.
      let capturedBuffers = this.capturedPendingBuffers.get(this.backend.currentSessionId!);
      if (!capturedBuffers) {
        capturedBuffers = [];
        this.capturedPendingBuffers.set(this.backend.currentSessionId!, capturedBuffers);
      }
      for (const buffer of this.buffersPending) {
        capturedBuffers.push(buffer);
      }
      this.buffersPending = [];
    }
  }

  dispose() {
    this.freeBuffers.forEach((buffers) => {
      buffers.forEach(buffer => {
        buffer.destroy();
      });
    });
    this.freeUniformBuffers.forEach((buffers) => {
      buffers.forEach(buffer => {
        buffer.destroy();
      });
    });

    this.storageCache.forEach((storage) => {
      storage.gpuData.buffer.destroy();
    });

    this.capturedPendingBuffers.forEach((buffers) => {
      buffers.forEach(buffer => {
        buffer.destroy();
      });
    });
    this.storageCache = new Map();
    this.freeBuffers = new Map();
    this.freeUniformBuffers = new Map();
    this.capturedPendingBuffers = new Map();
  }

  onReleaseSession(sessionId: number) {
    // release the captured pending buffers.
    const pendingBuffers = this.capturedPendingBuffers.get(sessionId);
    if (pendingBuffers) {
      pendingBuffers.forEach(buffer => {
        buffer.destroy();
      });
      this.capturedPendingBuffers.delete(sessionId);
    }
  }
}

export const createGpuDataManager = (...args: ConstructorParameters<typeof GpuDataManagerImpl>): GpuDataManager =>
    new GpuDataManagerImpl(...args);