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

const SHADER_AVG = fs.readFileSync('shader/avg.wgsl').toString();
const SHADER_TOT = fs.readFileSync('shader/tot.wgsl').toString();

export class ScalarBatch<
  L extends number,
  A extends Uint32Array | Int32Array | Float32Array,
  T extends NonNullable<ReturnType<A['at']>> = NonNullable<ReturnType<A['at']>>,
> extends GPUStruct<A> {
  public get layers(): L {
    return this.size[2] as L;
  }

  protected override workgroups(): [number, number, number] {
    return [1, 1, this.layers / GPUStruct.lunit];
  }

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

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

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

    ScalarBatch.assertPackable(1, this);

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

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

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

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

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

      let l = ol;
      for (const v of data ?? []) {
        if (l >= this.layers) {
          break;
        }
        this.data[l] = v;
        l++;
      }
      this._dirty = 'front';
    } else {
      const [batch] = args as [ScalarBatch<L, A, T>];
      const copy = this._device.createCommandEncoder();
      copy.copyBufferToBuffer(batch.buffer(), 0, this.buffer(), 0, this.byteLength);
      this._device.queue.submit([copy.finish()]);
      this._dirty = 'back';
    }
  }

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

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

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

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

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

  public static div<
    L extends number,
    A extends Uint32Array | Int32Array | Float32Array,
    T extends NonNullable<ReturnType<A['at']>> = NonNullable<ReturnType<A['at']>>,
  >(l: ScalarBatch<L, A, T>, r: ScalarBatch<L, A, T>, result: ScalarBatch<L, A, T> = new ScalarBatch(l._device, l._array, l.layers)): ScalarBatch<L, A, T> {
    return GPUStruct.cdiv(l, r, result);
  }

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

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

    return result.calculate('avg', SHADER_AVG, [m], false, 4);
  }

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

    return result.calculate('tot', SHADER_TOT, [m], false, 4);
  }
}