import { resolveBoundaryCondition, resolveBoundaryIndex } from '../caRuntime.js'
import type { Cells, SceneParams } from '../types.js'
import { emptyCellsLike } from './cellGrid.js'

function parseOuterTotalisticRule(ruleId: string) {
  const match = /^B([0-8]*)\/S([0-8]*)$/i.exec(ruleId)
  if (!match) return { birth: new Set([3]), survival: new Set([2, 3]) }

  return {
    birth: new Set(match[1].split('').map(Number)),
    survival: new Set(match[2].split('').map(Number))
  }
}

export function stepOuterTotalistic2d(cells: Cells, settings: SceneParams) {
  const rule = parseOuterTotalisticRule(settings.simulation?.ruleId ?? 'B3/S23')
  const next = emptyCellsLike(cells)
  const height = cells.length
  const width = cells[0]?.length ?? 0
  const boundary = resolveBoundaryCondition(settings.simulation?.grid)

  for (let y = 0; y < height; y += 1) {
    for (let x = 0; x < width; x += 1) {
      let neighbours = 0

      for (let dy = -1; dy <= 1; dy += 1) {
        for (let dx = -1; dx <= 1; dx += 1) {
          if (dx === 0 && dy === 0) continue

          const rawX = x + dx
          const rawY = y + dy
          const nx = resolveBoundaryIndex(rawX, width, boundary)
          const ny = resolveBoundaryIndex(rawY, height, boundary)

          if (nx === null || ny === null) continue
          if (cells[ny][nx]) neighbours += 1
        }
      }

      next[y][x] = cells[y][x] ? rule.survival.has(neighbours) : rule.birth.has(neighbours)
    }
  }

  return next
}