package render

import (
	"symph/game"
	"symph/parameter"
)

// GridScan caches one frame of per-position lookahead and resolves the
// grid-wide nearest distances. Blink membership is a grid-scope property, so
// every position is scanned before any tile is drawn. Allocation-free: fixed
// arrays refilled in place, shared by both frontends
type GridScan struct {
	Tiles   [parameter.GamePlayIndexYMax][parameter.GamePlayIndexXMax]game.TileLookahead
	NearPos int // grid-wide nearest positive distance; -1 when none
	NearNeg int // grid-wide nearest negative distance; -1 when none
}

func (g *GridScan) Refresh(s *game.GameState) {
	g.NearPos, g.NearNeg = -1, -1
	for y := range parameter.GamePlayIndexYMax {
		for x := range parameter.GamePlayIndexXMax {
			tl := s.ScanTile(y, x, parameter.PositionLookaheadWindow)
			g.Tiles[y][x] = tl
			if d := tl.Positive.Distance; d >= 0 && (g.NearPos < 0 || d < g.NearPos) {
				g.NearPos = d
			}
			if d := tl.Negative.Distance; d >= 0 && (g.NearNeg < 0 || d < g.NearNeg) {
				g.NearNeg = d
			}
		}
	}
}