package octree

import (
	"math"
)

type Tree struct {
	EPSG uint32

	vertices  []Vertex
	triangles [][]int32
	index     []int32

	Min Vertex
	Max Vertex
}

type box2d struct {
	x1 float64
	y1 float64
	x2 float64
	y2 float64
}

func (a box2d) intersects(b box2d) bool {
	return !(a.x2 < a.x1 || a.x2 < b.x1 ||
		a.y2 < a.y1 || a.y2 < b.y1)
}

func (a box2d) mid() (float64, float64) {
	return (a.x2-a.x1)*0.5 + a.x1, (a.y2-a.y1)*0.5 + a.y1
}

func (a box2d) xi(i int) float64 {
	if i == 0 {
		return a.x1
	}
	return a.x2
}

func (a box2d) yi(i int) float64 {
	if i == 0 {
		return a.y1
	}
	return a.y2
}

var scale = [][]float64{
	{0.0, 0.0, 0.5, 0.5},
	{0.5, 0.0, 1.0, 0.5},
	{0.0, 0.5, 0.5, 1.0},
	{0.5, 0.5, 1.0, 1.0},
}

func (ot *Tree) Vertical(x1, y1, x2, y2 float64, fn func(*Triangle)) {

	box := box2d{
		x1: math.Min(x1, x2),
		y1: math.Min(y1, y2),
		x2: math.Max(x1, x2),
		y2: math.Max(y1, y2),
	}

	// out of bounding box
	if box.x2 < ot.Min.X || ot.Max.X < box.x1 ||
		box.y2 < ot.Min.Y || ot.Max.Y < box.y1 {
		return
	}

	type frame struct {
		pos int32
		box2d
	}

	stack := []frame{{1, box2d{ot.Min.X, ot.Min.Y, ot.Max.X, ot.Max.Y}}}

	for len(stack) > 0 {
		top := stack[len(stack)-1]
		stack = stack[:len(stack)-1]

		if top.pos > 0 { // node
			midx, midy := top.mid()

			var all uint
			for i := 0; i < 2; i++ {
				for j := 0; j < 2; j++ {
					x, y := box.xi(i), box.yi(j)
					var code uint
					if x > midx {
						code |= 1
					}
					if y > midy {
						code |= 2
					}
					all |= 1 << code
				}
			}

			dx := top.x2 - top.x1
			dy := top.y2 - top.y1
			for i := 0; all != 0; i++ {
				if all&1 == 1 {
					s := scale[i]
					nbox := box2d{
						dx*s[0] + top.x1,
						dy*s[1] + top.y1,
						dx*s[2] + top.x1,
						dy*s[3] + top.y1,
					}
					// TODO: Push two frames to stack.
					_ = nbox
				}
				all >>= 1
			}

		} else { // leaf
		}
	}
}

func (ot *Tree) Horizontal(h float64, fn func(*Triangle)) {

	if h < ot.Min.Z || ot.Max.Z < h {
		return
	}

	type frame struct {
		pos int32
		min float64
		max float64
	}

	stack := []frame{{1, ot.Min.Z, ot.Max.Z}}

	dupes := map[int32]struct{}{}

	for len(stack) > 0 {
		top := stack[len(stack)-1]
		stack = stack[:len(stack)-1]

		pos := top.pos
		if pos == 0 {
			continue
		}
		min, max := top.min, top.max

		if pos > 0 { // node
			if mid := (max-min)*0.5 + min; h >= mid {
				pos += 4 // nodes with z-bit set
				min = mid
			} else {
				max = mid
			}
			stack = append(stack,
				frame{ot.index[pos+0], min, max},
				frame{ot.index[pos+1], min, max},
				frame{ot.index[pos+2], min, max},
				frame{ot.index[pos+3], min, max})
		} else { // leaf
			pos = -pos - 1
			n := ot.index[pos]
			//log.Printf("%d %d %d\n", pos, n, len(ot.index))
			indices := ot.index[pos+1 : pos+1+n]

			for _, idx := range indices {
				if _, found := dupes[idx]; found {
					continue
				}
				tri := ot.triangles[idx]
				t := Triangle{
					ot.vertices[tri[0]],
					ot.vertices[tri[1]],
					ot.vertices[tri[2]],
				}

				if !(math.Min(t[0].Z, math.Min(t[1].Z, t[2].Z)) > h ||
					math.Max(t[0].Z, math.Max(t[1].Z, t[2].Z)) < h) {
					dupes[idx] = struct{}{}
					fn(&t)
				}
			}
		}
	}
}