package ui

import (
	"image/color"

	rl "github.com/gen2brain/raylib-go/raylib"
)

var defaultGridPadding float32 = 0
var defaultGridRoundness float32 = 0

var defaultGridStyle = &Style {
	BacgroundColor:	&color.RGBA{0, 0, 0, 0},
	FontColor:		&rl.DarkGray,
	Padding:		&defaultGridPadding,
	Roundness:		&defaultGridRoundness,
}

// A dynamically shrinking element that contains other elements
type flexElement interface {
	GetElements() []UIElement
	GetSpacing() float32
	RecalculateCache(*rl.Rectangle)
}

// Calculates the element weight to pixel ratio
func getWeightToPixelsRatio(base flexElement, totalSpace float32) float32 { 
	var elements = base.GetElements()
	var totalWeights float32 = 0
	for _, v := range elements {
		totalWeights += v.GetOccupationWeight()
	}
	var spacingPx = totalSpace * base.GetSpacing()
	var totalSpacing = float32(len(elements) - 1) * spacingPx
	if totalSpace < 0 {
		totalSpace = 0
	}
	return (totalSpace - totalSpacing) / totalWeights
}


type layoutCache struct {
	// The screen resolution the cache was calculated for
	ScreenResolution rl.Vector2
	// The resolution the cache was calculated for
	SpanResolution rl.Vector2
	// Horizontal offset in pixels
	OffsetX float32
	// Vertical offset in pixels
	OffsetY float32
	// The X size of a row
	Width float32
	// The Y size of a row
	Height float32
	// The horizontal start and end of each row. 
	// Index of an array is representive with row index
	RowLocations []rl.Vector2
}

func (base layoutCache) IsValid() bool {
	return base.ScreenResolution.X == float32(rl.GetScreenWidth()) && 
		base.ScreenResolution.Y == float32(rl.GetScreenHeight())
}

func (base *layoutCache) CalculateOffsets(X float32, Y float32, paddingX float32, paddingY float32) {
	base.OffsetX = (X * paddingX)
	base.OffsetY = (Y * paddingY)
	base.Width = X - base.OffsetX * 2
	base.Height = Y - base.OffsetY * 2
}

func (base *layoutCache) CalculateRowsLocations (rows []UIElement, WeightToPixels float32, spacing float32, baseOffset float32) {
	base.RowLocations = make([]rl.Vector2, len(rows))
	var ptr float32 = baseOffset
	for i, v := range rows {
		// The spacing should be accounted for in the WeightToPixels param
		var elemSpace = (WeightToPixels * v.GetOccupationWeight())
		base.RowLocations[i] = rl.Vector2 {
			X: ptr,
			Y: elemSpace,
		}
		ptr += elemSpace + spacing
	}
}