import fs from 'node:fs';
import { Vector as CPUVector } from '../math';
import { GPUStruct } from './gpu-struct';
import { Scalar } from './scalar';
import { VectorBatch } from './vector-batch';

const SHADER_UNAVG = fs.readFileSync('shader/unavg.wgsl').toString();

const SHADER_DOT = fs.readFileSync('shader/mul.wgsl').toString();

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

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

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

  public constructor(device: GPUDevice, array: new (size: number) => A, data: CPUVector<D, T>);
  public constructor(device: GPUDevice, array: new (size: number) => A, d: D, data?: CPUVector<D, T>);
  public constructor(device: GPUDevice, array: new (size: number) => A, ...args: unknown[]) {
    const d: number = typeof args[0] === 'number'
      ? args[0] as D
      : (args[0] as CPUVector<D, T>).length;

    super(device, array, `${d}`, [d, 1, 1, 1]);

    Vector.assertPackable(1, this);

    const data = (typeof args[0] === 'number' ? args[1] : args[0]) as CPUVector<D, T> | undefined;
    if (data) {
      this.set(data);
    }
  }

  public async set(i: number, v: T): Promise<void>;
  public async set(data: CPUVector<D, T>): Promise<void>;
  public async set(slice: T[], oi?: number): Promise<void>;
  public async set(b: Vector<D, A, T>): Promise<void>;
  public async set(...args: unknown[]): Promise<void> {
    if (typeof args[0] === 'number') {
      const [i, v]: number[] = args as number[];

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

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

      if (this._dirty === 'back' && (oi || data.length < this.dims)) {
        await this.read();
      }

      let i = oi;
      for (const v of data ?? []) {
        if (i >= this.dims) {
          break;
        }
        this.data[i] = v;
        i++;
      }
      this._dirty = 'front';
    } else {
      const [vector] = args as [Vector<D, A, T>];
      const copy = this._device.createCommandEncoder();
      copy.copyBufferToBuffer(vector.buffer(), 0, this.buffer(), 0, this.byteLength);
      this._device.queue.submit([copy.finish()]);
      this._dirty = 'back';
    }
  }

  public async get(i: number): Promise<T>;
  public async get(): Promise<CPUVector<D, T>>;
  public async get(i?: number): Promise<T | CPUVector<D, T>> {
    if (this._dirty === 'back') {
      await this.read();
    }
    if (typeof i === 'number') {
      return this.data[i] as T;
    } else {
      const result: CPUVector<D, T> = [] as unknown as CPUVector<D, T>;
      for (let i: number = 0; i < this.dims; i++) {
        result.push(this.data[i] as T);
      }
      return result;
    }
  }

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

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

  public static sub<
    D extends number,
    A extends Uint32Array | Int32Array | Float32Array,
    T extends NonNullable<ReturnType<A['at']>> = NonNullable<ReturnType<A['at']>>,
  >(l: Vector<D, A, T>, r: Vector<D, A, T>, result: Vector<D, A, T> = new Vector(l._device, l._array, l.dims)): Vector<D, A, T> {
    return GPUStruct.csub(l, r, result);
  }

  public static mul<
    D extends number,
    A extends Uint32Array | Int32Array | Float32Array,
    T extends NonNullable<ReturnType<A['at']>> = NonNullable<ReturnType<A['at']>>,
  >(l: Scalar<A, T>, r: Vector<D, A, T>, result: Vector<D, A, T> = new Vector(r._device, r._array, r.dims)): Vector<D, A, T> {
    return GPUStruct.cscale(l, r, result);
  }

  public static dot<
    D extends number,
    A extends Uint32Array | Int32Array | Float32Array,
    T extends NonNullable<ReturnType<A['at']>> = NonNullable<ReturnType<A['at']>>,
  >(l: Vector<D, A, T>, r: Vector<D, A, T>, result: Scalar<A, T> = new Scalar(l._device, l._array)): Scalar<A, T> {
    throw new Error('Not implemented.');

    this.assertUnique(l, r);
    this.assertUnique(l, result);
    this.assertColocated(l, r, result);
    // this.assertPackable(4, r, result);

    return result.calculate('dot', SHADER_DOT, [l, r]);
  }

  public static unavg<
    L extends number,
    D extends number,
    A extends Uint32Array | Int32Array | Float32Array,
    T extends NonNullable<ReturnType<A['at']>>,
  >(
    l: L,
    m: Vector<D, A, T>,
    result: VectorBatch<L, D, A, T> = new VectorBatch(m._device, m._array, l, m.dims),
  ): VectorBatch<L, D, A, T> {
    this.assertUnique(m, result);
    this.assertColocated(m, result);
    this.assertPackable(4, m);

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