// Figures for the two-dimensional labs: the computed field, and the pointwise
// error beside it on a logarithmic colour scale, which is the only way to see
// both the interior and the corners of an error that spans decades.
import Field from '../../plot/Field.tsx'
import type { Num } from '../../engine/types.ts'
import { fmtErr } from '../onedim/panels.tsx'

export interface Single2DOut {
  names: string[]
  ms: number
  maxerr: Num
  unknowns: number
  x: number[]
  y: number[]
  U: Num[][]
  Err: Num[][]
}

/** A signed field gets the diverging ramp; a one-signed field the sequential
 *  one, so that the whole colour range is used either way. */
function signOf(z: Num[][]): 'div' | 'seq' {
  let lo = Infinity
  let hi = -Infinity
  for (const row of z) {
    for (const v of row) {
      if (v == null || !isFinite(v)) continue
      if (v < lo) lo = v
      if (v > hi) hi = v
    }
  }
  return lo < 0 && hi > 0 ? 'div' : 'seq'
}

/** Decades to span in an error picture: what the data actually covers. */
function decadesOf(z: Num[][]): number {
  let lo = Infinity
  let hi = 0
  for (const row of z) {
    for (const v of row) {
      if (v == null || !isFinite(v) || v <= 0) continue
      if (v < lo) lo = v
      if (v > hi) hi = v
    }
  }
  if (!isFinite(lo) || hi <= 0) return 6
  return Math.min(14, Math.max(3, Math.ceil(Math.log10(hi / lo))))
}

export function Fields2D({
  data,
  xDomain = [0, 1],
  yDomain = [0, 1],
  curves,
}: {
  data: Single2DOut
  xDomain?: [number, number]
  yDomain?: [number, number]
  curves?: { x: number[]; y: number[]; color?: string }[]
}) {
  const emax = data.maxerr == null || !isFinite(data.maxerr) ? 1 : Math.log10(data.maxerr)
  return (
    <div className="figure-row">
      <Field
        z={data.U}
        xDomain={xDomain}
        yDomain={yDomain}
        kind={signOf(data.U)}
        title="computed solution"
        curves={curves}
      />
      <Field
        z={data.Err}
        xDomain={xDomain}
        yDomain={yDomain}
        kind="log"
        zmax={Math.ceil(emax)}
        decades={decadesOf(data.Err)}
        title={`|error|, largest ${fmtErr(data.maxerr)}`}
        curves={curves}
      />
    </div>
  )
}