import fs from 'node:fs';
import { Matrix as CPUMatrix, Vector as CPUVector } from '../math';
import { GPUStruct } from './gpu-struct';
import { MatrixBatch } from './matrix-batch';
import { Scalar } from './scalar';
import { Vector } from './vector';

const SHADER_ISUM = fs.readFileSync('shader/isum.wgsl').toString();
const SHADER_MUL = fs.readFileSync('shader/mul.wgsl').toString();
const SHADER_TRANS = fs.readFileSync('shader/transpose.wgsl').toString();
const SHADER_UNAVG = fs.readFileSync('shader/unavg.wgsl').toString();

export class Matrix<
  H extends number,
  W extends number,
  A extends Uint32Array | Int32Array | Float32Array,
  T extends NonNullable<ReturnType<A['at']>> = NonNullable<ReturnType<A['at']>>,
> extends GPUStruct<A> {
  public get width(): W {
    return this.size[0] as W;
  }

  public get height(): H {
    return this.size[1] as H;
  }

  protected override workgroups(pm: number = 1): [number, number, number] {
    return [this.width / GPUStruct.dunit / pm, this.height / GPUStruct.dunit, 1];
  }

  protected override workgroup(): [number, number, number] {
    return [GPUStruct.dunit, GPUStruct.dunit, 1];
  }

  public constructor(device: GPUDevice, array: new (size: number) => A, data: CPUMatrix<H, W, T>);
  public constructor(device: GPUDevice, array: new (size: number) => A, h: H, w: W, data?: CPUMatrix<H, W, T>);
  public constructor(device: GPUDevice, array: new (size: number) => A, ...args: unknown[]) {
    let [h, w]: [number, number] = [1, 1];
    if (typeof args[0] === 'number') {
      [h, w] = args as [H, W];
    } else {
      const [data] = args as [CPUMatrix<H, W, T>];
      [h, w] = [data.length, data[0].length];
    }

    super(device, array, `${h}x${w}`, [w, h, 1, 1]);

    Matrix.assertPackable(1, this);

    const data = (typeof args[0] === 'number' ? args[2] : args[0]) as CPUMatrix<H, W, T> | undefined;
    if (data) {
      this.set(data);
    }
  }

  public index(y: number, x: number): number {
    return y * this.width + x;
  }

  public async set(y: number, x: number, v: T): Promise<void>;
  public async set(data: CPUMatrix<H, W, T>): Promise<void>;
  public async set(slice: T[][], oy?: number, ox?: number): Promise<void>;
  public async set(m: Matrix<H, W, A, T>): Promise<void>;
  public async set(...args: unknown[]): Promise<void> {
    if (typeof args[0] === 'number') {
      const [y, x, v]: number[] = args as number[];

      if (this._dirty === 'back') {
        await this.read();
      }

      this.data[this.index(y, x)] = v;
      this._dirty = 'front';
    } else if (Array.isArray(args[0])) {
      const [data, oy = 0, ox = 0] = args as [T[][], number | undefined, number | undefined];

      if (this._dirty === 'back' && (oy || ox || data.length < this.height || data[0].length < this.width)) {
        await this.read();
      }

      let y = oy;
      let x = ox;
      for (const row of data ?? []) {
        if (y >= this.height) {
          break;
        }
        for (const v of row) {
          if (x >= this.width) {
            break;
          }
          this.data[this.index(y, x)] = v;
          x++;
        }
        x = ox;
        y++;
      }
      this._dirty = 'front';
    } else {
      const [matrix] = args as [Matrix<H, W, A, T>];
      const copy = this._device.createCommandEncoder();
      copy.copyBufferToBuffer(matrix.buffer(), 0, this.buffer(), 0, this.byteLength);
      this._device.queue.submit([copy.finish()]);
      this._dirty = 'back';
    }
  }

  public async get(y: number, x: number): Promise<T>;
  public async get(): Promise<CPUMatrix<H, W, T>>;
  public async get(y?: number, x?: number): Promise<T | CPUMatrix<H, W, T>> {
    if (this._dirty === 'back') {
      await this.read();
    }
    if (typeof x === 'number') {
      return this.data[this.index(y!, x!)] as T;
    } else {
      const result: CPUMatrix<H, W, T> = [] as unknown as CPUMatrix<H, W, T>;
      for (let y: number = 0; y < this.height; y++) {
        const row: CPUVector<W, T> = [] as unknown as CPUVector<W, T>;
        for (let x: number = 0; x < this.width; x++) {
          row.push(this.data[this.index(y, x)] as T);
        }
        result.push(row);
      }
      return result;
    }
  }

  protected static override assertPackable(pm: number, ...ms: Matrix<number, number, Uint32Array | Int32Array | Float32Array>[]): void {
    for (const m of ms) {
      if (m.height % Matrix.dunit !== 0 || m.width % (Matrix.dunit * pm) !== 0) {
        throw new Error(`Matrix size ${m.height}x${m.width} must be divisible by ${Matrix.dunit}x${Matrix.dunit * pm}.`);
      }
    }
  }

  public static sum<
    H extends number,
    W extends number,
    A extends Uint32Array | Int32Array | Float32Array,
    T extends NonNullable<ReturnType<A['at']>> = NonNullable<ReturnType<A['at']>>,
  >(l: Matrix<H, W, A, T>, r: Matrix<H, W, A, T>, result: Matrix<H, W, A, T> = new Matrix(l._device, l._array, l.height, l.width)): Matrix<H, W, A, T> {
    return GPUStruct.csum(l, r, result);
  }

  public static sub<
    H extends number,
    W extends number,

    A extends Uint32Array | Int32Array | Float32Array,
    T extends NonNullable<ReturnType<A['at']>> = NonNullable<ReturnType<A['at']>>,
  >(l: Matrix<H, W, A, T>, r: Matrix<H, W, A, T>, result: Matrix<H, W, A, T> = new Matrix(l._device, l._array, l.height, l.width)): Matrix<H, W, A, T> {
    return GPUStruct.csub(l, r, result);
  }

  public static isum<
    H extends number,
    I extends number,
    W extends number,
    A extends Uint32Array | Int32Array | Float32Array,
    T extends NonNullable<ReturnType<A['at']>>,
  >(
    lis: Vector<I, Int32Array>,
    m: Matrix<H, W, A, T>,
    result: Matrix<H, W, A, T> = new Matrix(m._device, m._array, m.height, m.width),
  ): Matrix<H, W, A, T> {
    this.assertUnique(m, result);
    this.assertColocated(m, result);
    this.assertPackable(4, m, result);

    return result.calculate('isum', SHADER_ISUM, [lis, m], false, 4);
  }

  public static scale<
    H extends number,
    W extends number,
    A extends Uint32Array | Int32Array | Float32Array,
    T extends NonNullable<ReturnType<A['at']>> = NonNullable<ReturnType<A['at']>>,
  >(l: Scalar<A, T>, r: Matrix<H, W, A, T>, result: Matrix<H, W, A, T> = new Matrix(r._device, r._array, r.height, r.width)): Matrix<H, W, A, T> {
    return GPUStruct.cscale(l, r, result);
  }

  public static mul<
    H extends number,
    S extends number,
    W extends number,
    A extends Uint32Array | Int32Array | Float32Array,
    T extends NonNullable<ReturnType<A['at']>>,
  >(
    l: Matrix<H, S, A, T>,
    r: Matrix<S, W, A, T>,
    result: Matrix<H, W, A, T> = new Matrix(l._device, l._array, l.height, r.width),
  ): Matrix<H, W, A, T> {
    this.assertUnique(l, r, result);
    this.assertColocated(l, r, result);
    this.assertPackable(1, l, r, result);

    return result.calculate('mul', SHADER_MUL, [l, r]);
  }

  public static transpose<
    H extends number,
    W extends number,
    A extends Uint32Array | Int32Array | Float32Array,
    T extends NonNullable<ReturnType<A['at']>>,
  >(
    m: Matrix<H, W, A, T>,
    result: Matrix<W, H, A, T> = new Matrix(m._device, m._array, m.width, m.height),
  ): Matrix<W, H, A, T> {
    this.assertUnique(m, result);
    this.assertColocated(m, result);
    this.assertPackable(1, m, result);

    return result.calculate('transpose', SHADER_TRANS, [m]);
  }

  public static unavg<
    L extends number,
    H extends number,
    W extends number,
    A extends Uint32Array | Int32Array | Float32Array,
    T extends NonNullable<ReturnType<A['at']>>,
  >(
    l: L,
    m: Matrix<H, W, A, T>,
    result: MatrixBatch<L, H, W, A, T> = new MatrixBatch(m._device, m._array, l, m.height, m.width),
  ): MatrixBatch<L, H, W, A, T> {
    this.assertUnique(m, result);
    this.assertColocated(m, result);
    this.assertPackable(4, m);

    return result.calculate('unavg', SHADER_UNAVG, [m], false, 4);
  }
}