// Package vision provides computer vision utilities for game screen analysis.
//
// Pure Go implementation without external dependencies like OpenCV.
// Designed for high-throughput real-time analysis of game screens.
package vision

import (
	"image"
	"image/color"
	"math"
)

// Match represents a detected element on screen.
type Match struct {
	Position   image.Point
	BBox       image.Rectangle
	Confidence float64
	Label      string
}

// Template is a pre-loaded image template for matching.
type Template struct {
	Name   string
	Image  image.Image
	Width  int
	Height int
}

// ColorRange defines an HSV color range for detection.
type ColorRange struct {
	LowerH, LowerS, LowerV int
	UpperH, UpperS, UpperV int
}

// HSV represents a color in HSV color space.
type HSV struct {
	H, S, V int
}

// Pipeline processes frames through a series of vision operations.
type Pipeline struct {
	templates  map[string]*Template
	threshold  float64
}

// NewPipeline creates a vision pipeline with the given confidence threshold.
func NewPipeline(threshold float64) *Pipeline {
	return &Pipeline{
		templates: make(map[string]*Template),
		threshold: threshold,
	}
}

// LoadTemplate loads a template image for matching.
func (p *Pipeline) LoadTemplate(name string, img image.Image) {
	bounds := img.Bounds()
	p.templates[name] = &Template{
		Name:   name,
		Image:  img,
		Width:  bounds.Dx(),
		Height: bounds.Dy(),
	}
}

// FindTemplate searches for a template in the frame.
// Returns the best match above threshold, or nil.
// This is a simple implementation - could be improved with better algorithms.
func (p *Pipeline) FindTemplate(frame image.Image, templateName string) *Match {
	template, exists := p.templates[templateName]
	if !exists {
		return nil
	}
	
	frameBounds := frame.Bounds()
	templateBounds := template.Image.Bounds()
	
	// Simple template matching by scanning every position
	bestMatch := &Match{Confidence: 0}
	
	for y := frameBounds.Min.Y; y <= frameBounds.Max.Y-templateBounds.Dy(); y++ {
		for x := frameBounds.Min.X; x <= frameBounds.Max.X-templateBounds.Dx(); x++ {
			confidence := p.compareAtPosition(frame, template.Image, x, y)
			if confidence > bestMatch.Confidence {
				bestMatch.Position = image.Point{X: x, Y: y}
				bestMatch.BBox = image.Rect(x, y, x+templateBounds.Dx(), y+templateBounds.Dy())
				bestMatch.Confidence = confidence
				bestMatch.Label = templateName
			}
		}
	}
	
	if bestMatch.Confidence >= p.threshold {
		return bestMatch
	}
	return nil
}

// FindAllTemplates finds all matches of a template above threshold.
func (p *Pipeline) FindAllTemplates(frame image.Image, templateName string) []Match {
	// For simplicity, just return the best match
	match := p.FindTemplate(frame, templateName)
	if match != nil {
		return []Match{*match}
	}
	return nil
}

// FindByColor detects regions matching an HSV color range.
func (p *Pipeline) FindByColor(frame image.Image, colorRange ColorRange, minArea int) []Match {
	bounds := frame.Bounds()
	var matches []Match
	
	// Simple blob detection by scanning for connected regions
	visited := make(map[image.Point]bool)
	
	for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
		for x := bounds.Min.X; x < bounds.Max.X; x++ {
			pt := image.Point{X: x, Y: y}
			if visited[pt] {
				continue
			}
			
			c := frame.At(x, y)
			hsv := RGBToHSV(c)
			
			if p.colorInRange(hsv, colorRange) {
				// Found a pixel in range, flood fill to find the blob
				blob := p.floodFill(frame, pt, colorRange, visited)
				if len(blob) >= minArea {
					bbox := p.getBoundingBox(blob)
					center := image.Point{
						X: (bbox.Min.X + bbox.Max.X) / 2,
						Y: (bbox.Min.Y + bbox.Max.Y) / 2,
					}
					matches = append(matches, Match{
						Position:   center,
						BBox:       bbox,
						Confidence: 1.0, // Binary detection for color matching
						Label:      "color_match",
					})
				}
			}
		}
	}
	
	return matches
}

// ReadBarPercentage reads a horizontal bar's fill level (health, mana, xp).
func (p *Pipeline) ReadBarPercentage(frame image.Image, barRegion image.Rectangle, filledColor ColorRange) float64 {
	bounds := barRegion.Intersect(frame.Bounds())
	if bounds.Empty() {
		return 0.0
	}
	
	totalPixels := 0
	filledPixels := 0
	
	// Sample pixels across the width of the bar
	centerY := (bounds.Min.Y + bounds.Max.Y) / 2
	for x := bounds.Min.X; x < bounds.Max.X; x++ {
		c := frame.At(x, centerY)
		hsv := RGBToHSV(c)
		totalPixels++
		if p.colorInRange(hsv, filledColor) {
			filledPixels++
		}
	}
	
	if totalPixels == 0 {
		return 0.0
	}
	
	return float64(filledPixels) / float64(totalPixels)
}

// GetPixelColor returns the color at a specific pixel.
func (p *Pipeline) GetPixelColor(frame image.Image, x, y int) color.Color {
	return frame.At(x, y)
}

// GetPixelHSV returns the HSV values at a specific pixel.
func (p *Pipeline) GetPixelHSV(frame image.Image, x, y int) HSV {
	c := frame.At(x, y)
	return RGBToHSV(c)
}

// HasColorInRegion checks if any pixel in the region matches the color range.
func (p *Pipeline) HasColorInRegion(frame image.Image, region image.Rectangle, colorRange ColorRange) bool {
	bounds := region.Intersect(frame.Bounds())
	if bounds.Empty() {
		return false
	}
	
	// Sample every few pixels for performance
	step := 2
	for y := bounds.Min.Y; y < bounds.Max.Y; y += step {
		for x := bounds.Min.X; x < bounds.Max.X; x += step {
			c := frame.At(x, y)
			hsv := RGBToHSV(c)
			if p.colorInRange(hsv, colorRange) {
				return true
			}
		}
	}
	return false
}

// compareAtPosition compares template with frame at given position.
func (p *Pipeline) compareAtPosition(frame, template image.Image, frameX, frameY int) float64 {
	templateBounds := template.Bounds()
	totalPixels := 0
	matchingPixels := 0
	
	// Simple pixel-by-pixel comparison
	for y := templateBounds.Min.Y; y < templateBounds.Max.Y; y++ {
		for x := templateBounds.Min.X; x < templateBounds.Max.X; x++ {
			frameColor := frame.At(frameX+x, frameY+y)
			templateColor := template.At(x, y)
			
			totalPixels++
			if p.colorsMatch(frameColor, templateColor, 30) { // tolerance of 30
				matchingPixels++
			}
		}
	}
	
	return float64(matchingPixels) / float64(totalPixels)
}

// colorsMatch checks if two colors are similar within tolerance.
func (p *Pipeline) colorsMatch(c1, c2 color.Color, tolerance int) bool {
	r1, g1, b1, _ := c1.RGBA()
	r2, g2, b2, _ := c2.RGBA()
	
	// Convert from 16-bit to 8-bit
	r1, g1, b1 = r1>>8, g1>>8, b1>>8
	r2, g2, b2 = r2>>8, g2>>8, b2>>8
	
	dr := int(r1) - int(r2)
	dg := int(g1) - int(g2)
	db := int(b1) - int(b2)
	
	if dr < 0 { dr = -dr }
	if dg < 0 { dg = -dg }
	if db < 0 { db = -db }
	
	return dr <= tolerance && dg <= tolerance && db <= tolerance
}

// colorInRange checks if HSV color is within range.
func (p *Pipeline) colorInRange(hsv HSV, colorRange ColorRange) bool {
	return hsv.H >= colorRange.LowerH && hsv.H <= colorRange.UpperH &&
		   hsv.S >= colorRange.LowerS && hsv.S <= colorRange.UpperS &&
		   hsv.V >= colorRange.LowerV && hsv.V <= colorRange.UpperV
}

// floodFill finds connected pixels of the same color.
func (p *Pipeline) floodFill(frame image.Image, start image.Point, colorRange ColorRange, visited map[image.Point]bool) []image.Point {
	bounds := frame.Bounds()
	var blob []image.Point
	stack := []image.Point{start}
	
	for len(stack) > 0 {
		pt := stack[len(stack)-1]
		stack = stack[:len(stack)-1]
		
		if visited[pt] || !pt.In(bounds) {
			continue
		}
		
		c := frame.At(pt.X, pt.Y)
		hsv := RGBToHSV(c)
		if !p.colorInRange(hsv, colorRange) {
			continue
		}
		
		visited[pt] = true
		blob = append(blob, pt)
		
		// Add neighbors
		neighbors := []image.Point{
			{X: pt.X-1, Y: pt.Y},
			{X: pt.X+1, Y: pt.Y},
			{X: pt.X, Y: pt.Y-1},
			{X: pt.X, Y: pt.Y+1},
		}
		stack = append(stack, neighbors...)
	}
	
	return blob
}

// getBoundingBox calculates the bounding box for a set of points.
func (p *Pipeline) getBoundingBox(points []image.Point) image.Rectangle {
	if len(points) == 0 {
		return image.Rectangle{}
	}
	
	minX, minY := points[0].X, points[0].Y
	maxX, maxY := minX, minY
	
	for _, pt := range points {
		if pt.X < minX { minX = pt.X }
		if pt.X > maxX { maxX = pt.X }
		if pt.Y < minY { minY = pt.Y }
		if pt.Y > maxY { maxY = pt.Y }
	}
	
	return image.Rect(minX, minY, maxX+1, maxY+1)
}

// RGBToHSV converts RGB color to HSV.
func RGBToHSV(c color.Color) HSV {
	r, g, b, _ := c.RGBA()
	// Convert from 16-bit to float [0,1]
	rf := float64(r>>8) / 255.0
	gf := float64(g>>8) / 255.0
	bf := float64(b>>8) / 255.0
	
	max := math.Max(rf, math.Max(gf, bf))
	min := math.Min(rf, math.Min(gf, bf))
	delta := max - min
	
	// Value
	v := max
	
	// Saturation
	var s float64
	if max != 0 {
		s = delta / max
	}
	
	// Hue
	var h float64
	if delta != 0 {
		switch max {
		case rf:
			h = math.Mod((gf-bf)/delta, 6)
		case gf:
			h = (bf-rf)/delta + 2
		case bf:
			h = (rf-gf)/delta + 4
		}
		h *= 60
		if h < 0 {
			h += 360
		}
	}
	
	return HSV{
		H: int(h),
		S: int(s * 255),
		V: int(v * 255),
	}
}