/**
 * Column-major 2-D fields matching numbl's layout: rows index y, columns index x,
 * element (i, j) at data[i + j*ny].
 */
export interface Field2D {
  nx: number;
  ny: number;
  data: Float64Array;
}

/** A stack of frames: element (i, j, k) at data[i + j*ny + k*ny*nx]. */
export interface FieldFrames {
  nx: number;
  ny: number;
  nf: number;
  data: Float64Array;
}

export function frameOf(frames: FieldFrames, k: number): Field2D {
  const n = frames.nx * frames.ny;
  return { nx: frames.nx, ny: frames.ny, data: frames.data.subarray(k * n, (k + 1) * n) };
}

export function fieldAt(f: Field2D, i: number, j: number): number {
  return f.data[i + j * f.ny];
}

export interface Range {
  min: number;
  max: number;
}

export function rangeOf(data: ArrayLike<number>): Range {
  let min = Infinity;
  let max = -Infinity;
  for (let k = 0; k < data.length; k++) {
    const v = data[k];
    if (v < min) min = v;
    if (v > max) max = v;
  }
  if (!Number.isFinite(min)) return { min: 0, max: 0 };
  return { min, max };
}

/** Symmetric range about zero, for signed fields drawn with a diverging colormap. */
export function symmetricRange(r: Range): Range {
  const a = Math.max(Math.abs(r.min), Math.abs(r.max));
  return { min: -a, max: a };
}