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

import {Tensor} from '../../../tensor';
import {getGlsl} from '../glsl-source';
import {WebGLInferenceHandler} from '../inference-handler';
import {ProgramInfo, ProgramMetadata, TextureType} from '../types';

export const sum = (inferenceHandler: WebGLInferenceHandler, inputs: Tensor[]): Tensor[] => {
  validateInputs(inputs);

  const sumProgramMetadata = {
    name: 'Sum',
    inputNames: inputs.map((_v, i) => `X${i}`),
    inputTypes: new Array(inputs.length).fill(TextureType.unpacked)
  };

  const output = inferenceHandler.run(
      {...sumProgramMetadata, get: () => createSumProgramInfo(inferenceHandler, inputs, sumProgramMetadata)}, inputs);
  return [output];
};

const createSumProgramInfo =
    (inferenceHandler: WebGLInferenceHandler, inputs: Tensor[], sumProgramMetadata: ProgramMetadata): ProgramInfo => {
      const glsl = getGlsl(inferenceHandler.session.backend.glContext.version);
      const outputShape = inputs[0].dims.slice();
      const sumLine = inputs.map((_v, i) => `${glsl.texture2D}(X${i},TexCoords)`).join(' + ');
      const shaderSource = `
      void main() {
        vec4 result = ${sumLine};
        ${glsl.output} = result;
      }
    `;
      return {
        ...sumProgramMetadata,
        output: {dims: outputShape, type: inputs[0].type, textureType: TextureType.unpacked},
        hasMain: true,
        shaderSource
      };
    };

const validateInputs = (inputs: Tensor[]): void => {
  if (!inputs || inputs.length === 0) {
    throw new Error('Sum requires inputs.');
  }

  const length = inputs[0].dims.length;
  for (let i = 1; i < inputs.length; i++) {
    if (length !== inputs[i].dims.length) {
      throw new Error('Input shapes are mismatched.');
    }

    for (let j = 0; j < length; j++) {
      if (inputs[0].dims[j] !== inputs[i].dims[j]) {
        throw new Error('Input shapes are not matched.');
      }
    }
  }

  if (inputs[0].type !== 'float32' && inputs[0].type !== 'float64') {
    throw new Error('Invalid input type.');
  }
  for (let i = 1; i < inputs.length; i++) {
    if (inputs[0].type !== inputs[i].type) {
      throw new Error('Input types are not matched.');
    }
  }
};