package main

import "fmt"

// Brush applies terrain to a block centered at p. Each cell gets independent random color.
func Brush(m *Map, center Point, terrain int, size int, palette []Terrain) {
	half := size / 2
	for dy := -half; dy <= half; dy++ {
		for dx := -half; dx <= half; dx++ {
			color := ""
			if terrain >= 0 && terrain < len(palette) {
				color = palette[terrain].PickColor()
			}
			m.SetCell(Point{center.X + dx, center.Y + dy}, terrain, color)
		}
	}
}

// ThickenPoints expands a set of points by the given brush size, returning deduplicated points.
func ThickenPoints(pts []Point, size int) []Point {
	if size <= 1 {
		return pts
	}
	half := size / 2
	seen := make(map[Point]bool)
	var result []Point
	for _, p := range pts {
		for dy := -half; dy <= half; dy++ {
			for dx := -half; dx <= half; dx++ {
				np := Point{p.X + dx, p.Y + dy}
				if !seen[np] {
					seen[np] = true
					result = append(result, np)
				}
			}
		}
	}
	return result
}

// FloodFill fills a contiguous area from start with terrain.
func FloodFill(m *Map, start Point, terrain int, palette []Terrain) {
	if !m.InBounds(start) {
		return
	}
	target := m.CellAt(start).Terrain
	if target == terrain {
		return
	}
	color := ""
	if terrain >= 0 && terrain < len(palette) {
		color = palette[terrain].PickColor()
	}
	type pt struct{ x, y int }
	stack := []pt{{start.X, start.Y}}
	visited := make([][]bool, m.Height)
	for i := range visited {
		visited[i] = make([]bool, m.Width)
	}
	for len(stack) > 0 {
		p := stack[len(stack)-1]
		stack = stack[:len(stack)-1]
		if !m.InBounds(Point{p.x, p.y}) || visited[p.y][p.x] {
			continue
		}
		if m.Grid[p.y][p.x].Terrain != target {
			continue
		}
		visited[p.y][p.x] = true
		m.SetCell(Point{p.x, p.y}, terrain, color)
		stack = append(stack, pt{p.x + 1, p.y}, pt{p.x - 1, p.y}, pt{p.x, p.y + 1}, pt{p.x, p.y - 1})
	}
}

// BresenhamLine returns points along a line from a to b.
func BresenhamLine(a, b Point) []Point {
	var pts []Point
	x0, y0 := a.X, a.Y
	x1, y1 := b.X, b.Y
	dx := abs(x1 - x0)
	dy := -abs(y1 - y0)
	sx, sy := 1, 1
	if x0 > x1 {
		sx = -1
	}
	if y0 > y1 {
		sy = -1
	}
	err := dx + dy
	for {
		pts = append(pts, Point{x0, y0})
		if x0 == x1 && y0 == y1 {
			break
		}
		e2 := 2 * err
		if e2 >= dy {
			err += dy
			x0 += sx
		}
		if e2 <= dx {
			err += dx
			y0 += sy
		}
	}
	return pts
}

func abs(x int) int {
	if x < 0 {
		return -x
	}
	return x
}

// DrawRect returns points for the outline (or fill) of a rectangle.
func DrawRect(a, b Point, filled bool) []Point {
	x0, x1 := a.X, b.X
	y0, y1 := a.Y, b.Y
	if x0 > x1 {
		x0, x1 = x1, x0
	}
	if y0 > y1 {
		y0, y1 = y1, y0
	}
	var pts []Point
	if filled {
		for y := y0; y <= y1; y++ {
			for x := x0; x <= x1; x++ {
				pts = append(pts, Point{x, y})
			}
		}
		return pts
	}
	for x := x0; x <= x1; x++ {
		pts = append(pts, Point{x, y0}, Point{x, y1})
	}
	for y := y0 + 1; y < y1; y++ {
		pts = append(pts, Point{x0, y}, Point{x1, y})
	}
	return pts
}

// DrawCircle returns points for the outline (or fill) of a circle.
func DrawCircle(center, edge Point, filled bool) []Point {
	r2 := (edge.X-center.X)*(edge.X-center.X) + (edge.Y-center.Y)*(edge.Y-center.Y)
	r := r2
	if r < 0 {
		return nil
	}
	// integer sqrt approximation, good enough for grid
	radius := intSqrt(r)
	var pts []Point
	for dy := -radius; dy <= radius; dy++ {
		for dx := -radius; dx <= radius; dx++ {
			dist2 := dx*dx + dy*dy
			if filled {
				if dist2 <= r {
					pts = append(pts, Point{center.X + dx, center.Y + dy})
				}
			} else {
				// outline: approximate ring
				if dist2 <= r && dist2 > (radius-1)*(radius-1) {
					pts = append(pts, Point{center.X + dx, center.Y + dy})
				}
			}
		}
	}
	return pts
}

// DrawOval returns points for the outline (or fill) of an ellipse with two foci.
func DrawOval(f1, f2 Point, filled bool) []Point {
	// semi-major axis: enough to pass through f2 from f1, plus a bit
	dx := f2.X - f1.X
	dy := f2.Y - f1.Y
	// Use distance between foci as 2c, major axis 2a = 2c * 1.5 (so oval extends)
	dist := intSqrt(dx*dx + dy*dy)
	if dist == 0 {
		return nil
	}
	a := dist * 3 / 2 // major semi-axis (oval extends beyond both foci)
	if a < 1 {
		a = 1
	}
	a2 := a * a
	c2 := dist * dist / 4 // c = half distance between foci
	b2 := a2 - c2        // b² = a² - c²
	if b2 < 0 {
		b2 = 0
	}

	// Center of ellipse
	cx := (f1.X + f2.X) / 2
	cy := (f1.Y + f2.Y) / 2

	// Bounding box
	minX := cx - a - 1
	maxX := cx + a + 1
	minY := cy - a - 1
	maxY := cy + a + 1

	var pts []Point
	for py := minY; py <= maxY; py++ {
		for px := minX; px <= maxX; px++ {
			// Distances to foci
			d1 := distSq(px, py, f1.X, f1.Y)
			d2 := distSq(px, py, f2.X, f2.Y)
			sum := intSqrt(d1) + intSqrt(d2)

			if filled {
				if sum <= 2*a {
					pts = append(pts, Point{px, py})
				}
			} else {
				// Outline: near the ellipse boundary
				if sum >= 2*a-1 && sum <= 2*a+1 {
					pts = append(pts, Point{px, py})
				}
			}
		}
	}
	return pts
}

func distSq(x1, y1, x2, y2 int) int {
	dx := x1 - x2
	dy := y1 - y2
	return dx*dx + dy*dy
}

func intSqrt(n int) int {
	if n <= 0 {
		return 0
	}
	lo, hi := 0, n
	for lo < hi {
		mid := (lo + hi + 1) / 2
		if mid*mid <= n {
			lo = mid
		} else {
			hi = mid - 1
		}
	}
	return lo
}

// ApplyPoints writes terrain to all given points.
func ApplyPoints(m *Map, pts []Point, terrain int, palette []Terrain) {
	color := ""
	if terrain >= 0 && terrain < len(palette) {
		color = palette[terrain].PickColor()
	}
	for _, p := range pts {
		m.SetCell(p, terrain, color)
	}
}

// PlaceTextLabel adds a text label at start, clearing any prior text in those cells.
func PlaceTextLabel(m *Map, start Point, text string, color string) {
	// Remove any existing label starting at the same point
	RemoveTextLabel(m, start)
	tl := TextLabel{Text: text, Start: start, Color: color}
	m.TextLabels = append(m.TextLabels, tl)
	runes := []rune(text)
	for i, r := range runes {
		p := Point{start.X + i, start.Y}
		if m.InBounds(p) {
			m.Grid[p.Y][p.X].Text = string(r)
		}
	}
}

// RemoveTextLabel removes the text label starting at start.
func RemoveTextLabel(m *Map, start Point) {
	for i, tl := range m.TextLabels {
		if tl.Start == start {
			m.TextLabels = append(m.TextLabels[:i], m.TextLabels[i+1:]...)
			break
		}
	}
	// Also clear from grid cells
	for y := range m.Grid {
		for x := range m.Grid[y] {
			if m.Grid[y][x].Text == "" {
				continue
			}
			// Check if this cell belongs to a label
			found := false
			for _, tl := range m.TextLabels {
				runes := []rune(tl.Text)
				for i := range runes {
					if tl.Start.X+i == x && tl.Start.Y == y {
						found = true
						break
					}
				}
				if found {
					break
				}
			}
			if !found {
				m.Grid[y][x].Text = ""
			}
		}
	}
}

// FindTextLabelAt returns the label index that covers point p, or -1.
func FindTextLabelAt(m *Map, p Point) int {
	for i, tl := range m.TextLabels {
		runes := []rune(tl.Text)
		for j := range runes {
			if tl.Start.X+j == p.X && tl.Start.Y == p.Y {
				return i
			}
		}
	}
	return -1
}

// MoveTextLabel moves label at oldStart to newStart.
func MoveTextLabel(m *Map, oldStart, newStart Point) {
	for i, tl := range m.TextLabels {
		if tl.Start == oldStart {
			// Clear old cells
			for _, p := range LabelPositions(tl) {
				if m.InBounds(p) {
					m.Grid[p.Y][p.X].Text = ""
				}
			}
			m.TextLabels[i].Start = newStart
			// Set new cells
			runes := []rune(tl.Text)
			for j, r := range runes {
				p := Point{newStart.X + j, newStart.Y}
				if m.InBounds(p) {
					m.Grid[p.Y][p.X].Text = string(r)
				}
			}
			return
		}
	}
}

func LabelPositions(tl TextLabel) []Point {
	var pts []Point
	runes := []rune(tl.Text)
	for i := range runes {
		pts = append(pts, Point{tl.Start.X + i, tl.Start.Y})
	}
	return pts
}

func DemoTools() {
	m := NewMap("test", 10, 10, nil)
	Brush(m, Point{5, 5}, 0, 3, nil)
	if m.Grid[5][5].Terrain != 0 {
		panic("Brush failed")
	}
	pts := BresenhamLine(Point{0, 0}, Point{3, 0})
	if len(pts) != 4 || pts[0] != (Point{0, 0}) || pts[3] != (Point{3, 0}) {
		panic(fmt.Sprintf("Line failed: %v", pts))
	}
	// intSqrt sanity
	if intSqrt(25) != 5 || intSqrt(26) != 5 || intSqrt(0) != 0 {
		panic("intSqrt failed")
	}
	// Color picking
	t := Terrain{Colors: []TerrainColor{{Color: "22", Weight: 100}}}
	if t.PickColor() != "22" {
		panic("PickColor failed")
	}
	// Text labels — Grid[y][x]
	PlaceTextLabel(m, Point{2, 2}, "ABC", "")
	if m.Grid[2][2].Text != "A" || m.Grid[2][3].Text != "B" {
		panic("TextLabel: " + m.Grid[2][2].Text + "," + m.Grid[2][3].Text)
	}
	RemoveTextLabel(m, Point{2, 2})
	if m.Grid[2][2].Text != "" {
		panic("TextLabel remove failed")
	}
	fmt.Println("tools: ok")
}