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

import {AttributeWithCacheKey, createAttributeWithCacheKey} from '../../../attribute-with-cache-key';
import {Graph} from '../../../graph';
import {OperatorImplementation, OperatorInitialization} from '../../../operators';
import {Tensor} from '../../../tensor';
import {ShapeUtil} from '../../../util';
import {getGlsl, Glsl} from '../glsl-source';
import {WebGLInferenceHandler} from '../inference-handler';
import {ProgramInfo, TextureType} from '../types';

export interface PadAttributes extends AttributeWithCacheKey {
  readonly mode: string;
  readonly pads: number[];
  readonly value: number;
}

const padProgramMetadata = {
  name: 'Pad',
  inputNames: ['A'],
  inputTypes: [TextureType.unpacked],
};

export const pad: OperatorImplementation<PadAttributes> =
    (inferenceHandler: WebGLInferenceHandler, inputs: Tensor[], attributes: PadAttributes): Tensor[] => {
      validateInputs(inputs);
      const output = inferenceHandler.run(
          {
            ...padProgramMetadata,
            cacheHint: attributes.cacheKey,
            get: () => createPadProgramInfo(inferenceHandler, inputs, attributes)
          },
          inputs);
      return [output];
    };

export const parsePadAttributes: OperatorInitialization<PadAttributes> = (node: Graph.Node): PadAttributes => {
  const mode = node.attributes.getString('mode', 'constant');
  const value = node.attributes.getFloat('value', 0.0);
  const pads = node.attributes.getInts('pads');
  return createAttributeWithCacheKey({mode, value, pads});
};

const createPadProgramInfo =
    (inferenceHandler: WebGLInferenceHandler, inputs: Tensor[], attributes: PadAttributes): ProgramInfo => {
      const outputShape = ShapeUtil.padShape(inputs[0].dims.slice(), attributes.pads);
      const rank = outputShape.length;
      const padFunction = getPadFunction(inferenceHandler, inputs[0], attributes);
      const shaderSource = `
      ${padFunction}
      float process(int[${rank}] indices) {
          return padA(indices);
      }`;
      return {
        name: 'Pad',
        inputNames: ['A'],
        inputTypes: [TextureType.unpacked],
        output: {dims: outputShape, type: inputs[0].type, textureType: TextureType.unpacked},
        shaderSource
      };
    };

const validateInputs = (inputs: Tensor[]): void => {
  if (!inputs || inputs.length !== 1) {
    throw new Error('Pad requires 1 input');
  }
  if (inputs[0].type !== 'float32' && inputs[0].type !== 'float64') {
    throw new Error('Invalid input type.');
  }
};

const getPadFunction = (inferenceHandler: WebGLInferenceHandler, input: Tensor, attributes: PadAttributes): string => {
  const glsl = getGlsl(inferenceHandler.session.backend.glContext.version);
  const [width, height] = inferenceHandler.calculateTextureWidthAndHeight(input.dims, TextureType.unpacked);
  const strides = ShapeUtil.computeStrides(input.dims);

  switch (attributes.mode) {
    case 'constant':
      return getPadConstant(glsl, input.dims, strides, width, height, attributes.pads, attributes.value);
    case 'reflect':
      return getPadReflect(glsl, input.dims, strides, width, height, attributes.pads);
    case 'edge':
      return getPadEdge(glsl, input.dims, strides, width, height, attributes.pads);
    default:
      throw new Error('Invalid mode');
  }
};

const getPadConstant =
    (glsl: Glsl, shape: readonly number[], strides: readonly number[], width: number, height: number, pads: number[],
     value: number): string => {
      const rank = shape.length;
      let block = '';
      for (let i = rank - 1; i >= 0; --i) {
        block += `
        k = m[${i}] - ${pads[i]};
        if (k < 0)  return constant;
        if (k >= ${shape[i]}) return constant;
        offset += k * ${strides[i]};
        `;
      }
      return `
      float padA(int m[${rank}]) {
        const float constant = float(${value});
        int offset = 0;
        int k = 0;
        ${block}
        vec2 coords = offsetToCoords(offset, ${width}, ${height});
        float value = getColorAsFloat(${glsl.texture2D}(A, coords));
        return value;
      }
      `;
    };

const getPadReflect =
    (glsl: Glsl, shape: readonly number[], strides: readonly number[], width: number, height: number, pads: number[]):
        string => {
          const rank = shape.length;

          let block = '';
          for (let i = rank - 1; i >= 0; --i) {
            block += `
        k = m[${i}] - ${pads[i]};
        if (k < 0) { k = -k; }
        {
          const int _2n_1 = ${2 * (shape[i] - 1)};
          k = int( mod( float(k), float(_2n_1) ) ) ;
          if(k >= ${shape[i]}) { k = _2n_1 - k; }
        }
        offset += k * ${strides[i]};
        `;
          }
          return `
      float padA(int m[${rank}]) {
        int offset = 0;
        int k = 0;
        ${block}
        vec2 coords = offsetToCoords(offset, ${width}, ${height});
        float value = getColorAsFloat(${glsl.texture2D}(A, coords));
        return value;
      }
      `;
        };

const getPadEdge =
    (glsl: Glsl, shape: readonly number[], strides: readonly number[], width: number, height: number, pads: number[]):
        string => {
          const rank = shape.length;

          let block = '';
          for (let i = rank - 1; i >= 0; --i) {
            block += `
        k = m[${i}] - ${pads[i]};
        if (k < 0)  k = 0;
        if (k >= ${shape[i]}) k = ${shape[i] - 1};
        offset += k * ${strides[i]};
      `;
          }
          return `
      float padA(int m[${rank}]) {
        int offset = 0;
        int k = 0;
        ${block}
        vec2 coords = offsetToCoords(offset, ${width}, ${height});
        float value = getColorAsFloat(${glsl.texture2D}(A, coords));
        return value;
      }
      `;
        };