/**
 * Plain, structured-clone-friendly mirror of the numbl values the lab uses.
 * Tensors keep numbl's column-major layout: element (i, j) of an [m, n] array is
 * data[i + j*m], and (i, j, k) of an [m, n, p] array is data[i + j*m + k*m*n].
 */
export interface PlainTensor {
  kind: "tensor";
  shape: number[];
  data: Float64Array;
  imag?: Float64Array;
}
export interface PlainStruct {
  kind: "struct";
  fields: Record<string, PlainValue>;
}
export interface PlainCell {
  kind: "cell";
  shape: number[];
  items: PlainValue[];
}
export interface PlainUnsupported {
  kind: "unsupported";
  description: string;
}
export type PlainValue = number | boolean | string | PlainTensor | PlainStruct | PlainCell | PlainUnsupported;

export function isPlainTensor(v: PlainValue | undefined): v is PlainTensor {
  return typeof v === "object" && v !== null && v.kind === "tensor";
}
export function isPlainStruct(v: PlainValue | undefined): v is PlainStruct {
  return typeof v === "object" && v !== null && v.kind === "struct";
}
export function isPlainCell(v: PlainValue | undefined): v is PlainCell {
  return typeof v === "object" && v !== null && v.kind === "cell";
}

/** All ArrayBuffers inside a value, for zero-copy transfer out of a worker. */
export function collectBuffers(v: PlainValue, out: ArrayBuffer[] = []): ArrayBuffer[] {
  if (isPlainTensor(v)) {
    out.push(v.data.buffer as ArrayBuffer);
    if (v.imag) out.push(v.imag.buffer as ArrayBuffer);
  } else if (isPlainStruct(v)) {
    for (const f of Object.values(v.fields)) collectBuffers(f, out);
  } else if (isPlainCell(v)) {
    for (const item of v.items) collectBuffers(item, out);
  }
  return out;
}