// 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, ProgramInfoLoader, ProgramMetadata, TextureType} from '../types';
import {getCoordsDataType, getGlChannels} from '../utils';

import {ConcatAttributes} from './concat';
import {getChannels, unpackFromChannel} from './packing-utils';

const createPackedConcatProgramMetadata = (inputCount: number, cacheHint: string) => ({
  name: 'Concat (packed)',
  inputNames: Array.from({length: inputCount}, (v, i) => `X${i}`),
  inputTypes: Array(inputCount).fill(TextureType.packed),
  cacheHint
});

const createPackedConcatProgramInfo =
    (handler: WebGLInferenceHandler, metadata: ProgramMetadata, inputs: Tensor[], axis: number): ProgramInfo => {
      const inputShape = inputs[0].dims.slice();
      if (axis >= inputShape.length || axis < (-1 * inputShape.length)) {
        throw new Error('axis specified for concat doesn\'t match input dimensionality');
      }
      if (axis < 0) {
        axis = inputShape.length + axis;
      }
      // ensure all of the non-concatenated axes match each other
      // calculate the shape of the output tensor while we do that
      const outputShape = inputShape.slice(0);
      for (let i = 1; i < inputs.length; i++) {
        const dataNShape = inputs[i].dims.slice();
        for (let axisIndex = 0; axisIndex < inputShape.length; axisIndex++) {
          // add to the placeholder for computing output shape
          if (axisIndex === axis) {
            outputShape[axis] += dataNShape[axisIndex];
          }
          // ensure all non-cancatenated axes match each other
          else if (inputShape[axisIndex] !== dataNShape[axisIndex]) {
            throw new Error('non concat dimensions must match');
          }
        }
      }

      const rank = outputShape.length;
      const coords = getChannels('coords', rank);
      const dtype = getCoordsDataType(rank);
      const unpackChannel = unpackFromChannel();

      const shapes = inputs.map(i => i.dims);
      const channels = getGlChannels(rank);
      const offsets: number[] = new Array(shapes.length - 1);

      offsets[0] = shapes[0][axis];
      for (let i = 1; i < offsets.length; i++) {
        offsets[i] = offsets[i - 1] + shapes[i][axis];
      }

      const channel = channels[axis];
      const lastChannels = channels.slice(-2);
      const allChannels = channels.join();

      let getValueSnippet = `if (${channel} < ${offsets[0]}) {
        return getChannel(
            getX0(${allChannels}), vec2(${lastChannels.join()}));
        }`;
      for (let i = 1; i < offsets.length; i++) {
        const shift = offsets[i - 1];
        getValueSnippet += `
            if (${channel} < ${offsets[i]}  && ${channel} >= ${offsets[i - 1]}) {
              return getChannel(
                getX${i}(${getShiftedChannelsSnippet(channels, channel, shift)}),
                vec2(${getShiftedChannelsSnippet(lastChannels, channel, shift)}));
            }`;
      }
      const lastIndex = offsets.length;
      const shift = offsets[offsets.length - 1];
      getValueSnippet += `
            return getChannel(
              getX${lastIndex}(${getShiftedChannelsSnippet(channels, channel, shift)}),
              vec2(${getShiftedChannelsSnippet(lastChannels, channel, shift)}));`;

      const glsl = getGlsl(handler.session.backend.glContext.version);

      const shaderSource = `
          ${unpackChannel}
          float getValue(${channels.map(x => 'int ' + x)}) {
            ${getValueSnippet}
          }

          void main() {
            ${dtype} coords = getOutputCoords();
            int lastDim = coords.${channels[rank - 1]};
            coords.${channels[rank - 1]} = coords.${channels[rank - 2]};
            coords.${channels[rank - 2]} = lastDim;

            vec4 result = vec4(getValue(${coords}), 0., 0., 0.);

            ${coords[rank - 1]} = ${coords[rank - 1]} + 1;
            if (${coords[rank - 1]} < ${outputShape[rank - 1]}) {
              result.g = getValue(${coords});
            }

            ${coords[rank - 2]} = ${coords[rank - 2]} + 1;
            if (${coords[rank - 2]} < ${outputShape[rank - 2]}) {
              result.a = getValue(${coords});
            }

            ${coords[rank - 1]} = ${coords[rank - 1]} - 1;
            if (${coords[rank - 2]} < ${outputShape[rank - 2]} &&
                ${coords[rank - 1]} < ${outputShape[rank - 1]}) {
              result.b = getValue(${coords});
            }
            ${glsl.output} = result;
          }
        `;

      return {
        ...metadata,
        output: {dims: outputShape, type: inputs[0].type, textureType: TextureType.packed},
        shaderSource,
        hasMain: true,
      };
    };

export const createPackedConcatProgramInfoLoader =
    (handler: WebGLInferenceHandler, inputs: Tensor[], attributes: ConcatAttributes): ProgramInfoLoader => {
      const metadata = createPackedConcatProgramMetadata(inputs.length, attributes.cacheKey);
      return {...metadata, get: () => createPackedConcatProgramInfo(handler, metadata, inputs, attributes.axis)};
    };

const getShiftedChannelsSnippet = (channels: string[], channel: string, shift: number): string => {
  const channelIdx = channels.indexOf(channel);
  const res = channels.map((c, idx) => {
    if (idx === channelIdx) {
      return `${c} - ${shift}`;
    } else {
      return c;
    }
  });
  return res.join();
};