package viz

import (
	"bspviz/internal/bsp"
	"bspviz/internal/geom"
	"bspviz/internal/mapfmt"
	"image"
	"image/color"
	"image/png"
	"math"
	"math/rand"
	"os"
	"time"
)

// worldToScreen transformiert Doom-Koordinaten in Bildkoordinaten
type worldToScreen struct {
	minX, minY float64
	scale      float64
	W, H       int
	margin     float64
}

func makeTransform(verts []mapfmt.Vertex, W, H int) worldToScreen {
	minX, minY := math.MaxFloat64, math.MaxFloat64
	maxX, maxY := -math.MaxFloat64, -math.MaxFloat64
	for _, v := range verts {
		x, y := float64(v.X), float64(v.Y)
		if x < minX {
			minX = x
		}
		if y < minY {
			minY = y
		}
		if x > maxX {
			maxX = x
		}
		if y > maxY {
			maxY = y
		}
	}
	margin := 20.0
	w := maxX - minX
	h := maxY - minY
	if w < 1 {
		w = 1
	}
	if h < 1 {
		h = 1
	}
	scale := math.Min((float64(W)-2*margin)/w, (float64(H)-2*margin)/h)
	return worldToScreen{minX, minY, scale, W, H, margin}
}

func (t worldToScreen) P(p geom.Vec) (int, int) {
	x := t.margin + (p.X-t.minX)*t.scale
	y := t.margin + (p.Y-t.minY)*t.scale
	// Y-Achse flippen (Doom: +Y nach oben, Bild: +Y nach unten)
	yy := float64(t.H) - y
	return int(x + 0.5), int(yy + 0.5)
}

// einfache Bresenham-Linie
func drawLine(img *image.RGBA, x0, y0, x1, y1 int, c color.Color) {
	dx := int(math.Abs(float64(x1 - x0)))
	dy := -int(math.Abs(float64(y1 - y0)))
	sx := -1
	if x0 < x1 {
		sx = 1
	}
	sy := -1
	if y0 < y1 {
		sy = 1
	}
	err := dx + dy
	for {
		if x0 >= 0 && y0 >= 0 && x0 < img.Bounds().Dx() && y0 < img.Bounds().Dy() {
			img.Set(x0, y0, c)
		}
		if x0 == x1 && y0 == y1 {
			break
		}
		e2 := 2 * err
		if e2 >= dy {
			err += dy
			x0 += sx
		}
		if e2 <= dx {
			err += dx
			y0 += sy
		}
	}
}

// RenderPNG zeichnet die Map und den BSP-Baum
func RenderPNG(m *mapfmt.MapData, root *bsp.Node, outPath string) error {
	W, H := 1200, 900
	img := image.NewRGBA(image.Rect(0, 0, W, H))

	// Hintergrund
	bg := color.RGBA{20, 20, 24, 255}
	for y := 0; y < H; y++ {
		for x := 0; x < W; x++ {
			img.Set(x, y, bg)
		}
	}

	tr := makeTransform(m.Vertices, W, H)

	// 1) Linedefs grau
	gray := color.RGBA{180, 180, 180, 255}
	for _, L := range m.Linedefs {
		a := m.Vertices[L.V1]
		b := m.Vertices[L.V2]
		x0, y0 := tr.P(geom.V(float64(a.X), float64(a.Y)))
		x1, y1 := tr.P(geom.V(float64(b.X), float64(b.Y)))
		drawLine(img, x0, y0, x1, y1, gray)
	}

	// 2) Split-Linien (gelb)
	yellow := color.RGBA{240, 210, 40, 255}
	var drawSplits func(*bsp.Node)
	drawSplits = func(n *bsp.Node) {
		if n == nil || n.Leaf != nil {
			return
		}
		D := n.D
		L := geom.Len(D)
		if L < 1e-9 {
			return
		}
		dx, dy := D.X/L, D.Y/L
		k := 1e6 // "lange" Linie
		p0 := geom.V(n.O.X-k*dx, n.O.Y-k*dy)
		p1 := geom.V(n.O.X+k*dx, n.O.Y+k*dy)
		x0, y0 := tr.P(p0)
		x1, y1 := tr.P(p1)
		drawLine(img, x0, y0, x1, y1, yellow)
		drawSplits(n.Left)
		drawSplits(n.Right)
	}
	drawSplits(root)

	// 3) Leaves farbig
	rng := rand.New(rand.NewSource(time.Now().UnixNano()))
	var paintLeaves func(*bsp.Node)
	paintLeaves = func(n *bsp.Node) {
		if n == nil {
			return
		}
		if n.Leaf != nil {
			col := color.RGBA{
				uint8(100 + rng.Intn(100)),
				uint8(100 + rng.Intn(100)),
				uint8(100 + rng.Intn(100)),
				255,
			}
			for _, s := range n.Leaf.Segs {
				x0, y0 := tr.P(s.A)
				x1, y1 := tr.P(s.B)
				drawLine(img, x0, y0, x1, y1, col)
			}
			return
		}
		paintLeaves(n.Left)
		paintLeaves(n.Right)
	}
	paintLeaves(root)

	// speichern
	f, err := os.Create(outPath)
	if err != nil {
		return err
	}
	defer f.Close()
	return png.Encode(f, img)
}