rui/backgroundGradient.go

package rui

import "strings"

const (

	// ToTopGradient is value of the Direction property of a linear gradient. The value is equivalent to the 0deg angle
	ToTopGradient = 0
	// ToRightTopGradient is value of the Direction property of a linear gradient.
	ToRightTopGradient = 1
	// ToRightGradient is value of the Direction property of a linear gradient. The value is equivalent to the 90deg angle
	ToRightGradient = 2
	// ToRightBottomGradient is value of the Direction property of a linear gradient.
	ToRightBottomGradient = 3
	// ToBottomGradient is value of the Direction property of a linear gradient. The value is equivalent to the 180deg angle
	ToBottomGradient = 4
	// ToLeftBottomGradient is value of the Direction property of a linear gradient.
	ToLeftBottomGradient = 5
	// ToLeftGradient is value of the Direction property of a linear gradient. The value is equivalent to the 270deg angle
	ToLeftGradient = 6
	// ToLeftTopGradient is value of the Direction property of a linear gradient.
	ToLeftTopGradient = 7

	// EllipseGradient is value of the Shape property of a radial gradient background:
	// the shape is an axis-aligned ellipse
	EllipseGradient = 0
	// CircleGradient is value of the Shape property of a radial gradient background:
	// the gradient's shape is a circle with constant radius
	CircleGradient = 1

	// ClosestSideGradient is value of the Radius property of a radial gradient background:
	// The gradient's ending shape meets the side of the box closest to its center (for circles)
	// or meets both the vertical and horizontal sides closest to the center (for ellipses).
	ClosestSideGradient = 0
	// ClosestCornerGradient is value of the Radius property of a radial gradient background:
	// The gradient's ending shape is sized so that it exactly meets the closest corner
	// of the box from its center.
	ClosestCornerGradient = 1
	// FarthestSideGradient is value of the Radius property of a radial gradient background:
	// Similar to closest-side, except the ending shape is sized to meet the side of the box
	// farthest from its center (or vertical and horizontal sides).
	FarthestSideGradient = 2
	// FarthestCornerGradient is value of the Radius property of a radial gradient background:
	// The default value, the gradient's ending shape is sized so that it exactly meets
	// the farthest corner of the box from its center.
	FarthestCornerGradient = 3
)

// BackgroundGradientPoint define point on gradient straight line
type BackgroundGradientPoint struct {
	// Color - the color of the point. Must not be nil.
	// Can take a value of Color type or string (color constant or textual description of the color)
	Color any
	// Pos - the distance from the start of the gradient straight line. Optional (may be nil).
	// Can take a value of SizeUnit type or string (angle constant or textual description of the SizeUnit)
	Pos any
}

type backgroundGradient struct {
	backgroundElement
}

type backgroundLinearGradient struct {
	backgroundGradient
}

type backgroundRadialGradient struct {
	backgroundGradient
}

// NewBackgroundLinearGradient creates the new background linear gradient
func NewBackgroundLinearGradient(params Params) BackgroundElement {
	result := new(backgroundLinearGradient)
	result.properties = map[string]any{}
	for tag, value := range params {
		result.Set(tag, value)
	}
	return result
}

// NewBackgroundRadialGradient creates the new background radial gradient
func NewBackgroundRadialGradient(params Params) BackgroundElement {
	result := new(backgroundRadialGradient)
	result.properties = map[string]any{}
	for tag, value := range params {
		result.Set(tag, value)
	}
	return result
}

func (gradient *backgroundGradient) parseGradientText(value string) []BackgroundGradientPoint {
	elements := strings.Split(value, ",")
	count := len(elements)
	if count < 2 {
		ErrorLog("The gradient must contain at least 2 points")
		return nil
	}

	points := make([]BackgroundGradientPoint, count)
	for i, element := range elements {
		if !points[i].setValue(element) {
			ErrorLogF(`Ivalid %d element of the conic gradient: "%s"`, i, element)
			return nil
		}
	}
	return points
}

func (gradient *backgroundGradient) Set(tag string, value any) bool {

	switch tag = strings.ToLower(tag); tag {
	case Repeating:
		return gradient.setBoolProperty(tag, value)

	case Gradient:
		switch value := value.(type) {
		case string:
			if value != "" {
				if strings.Contains(value, " ") || strings.Contains(value, ",") {
					if points := gradient.parseGradientText(value); len(points) >= 2 {
						gradient.properties[Gradient] = points
						return true
					}
				} else if value[0] == '@' {
					gradient.properties[Gradient] = value
					return true
				}
			}

		case []BackgroundGradientPoint:
			if len(value) >= 2 {
				gradient.properties[Gradient] = value
				return true
			}

		case []Color:
			count := len(value)
			if count >= 2 {
				points := make([]BackgroundGradientPoint, count)
				for i, color := range value {
					points[i].Color = color
				}
				gradient.properties[Gradient] = points
				return true
			}

		case []GradientPoint:
			count := len(value)
			if count >= 2 {
				points := make([]BackgroundGradientPoint, count)
				for i, point := range value {
					points[i].Color = point.Color
					points[i].Pos = Percent(point.Offset * 100)
				}
				gradient.properties[Gradient] = points
				return true
			}
		}

		ErrorLogF("Invalid gradient %v", value)
		return false
	}

	ErrorLogF("Property %s is not supported by a background gradient", tag)
	return false
}

func (point *BackgroundGradientPoint) setValue(text string) bool {
	text = strings.Trim(text, " ")

	colorText := text
	pointText := ""

	if index := strings.Index(text, " "); index > 0 {
		colorText = text[:index]
		pointText = strings.Trim(text[index+1:], " ")
	}

	if colorText == "" {
		return false
	}

	if colorText[0] == '@' {
		point.Color = colorText
	} else if color, ok := StringToColor(colorText); ok {
		point.Color = color
	} else {
		return false
	}

	if pointText == "" {
		point.Pos = nil
	} else if pointText[0] == '@' {
		point.Pos = pointText
	} else if pos, ok := StringToSizeUnit(pointText); ok {
		point.Pos = pos
	} else {
		return false
	}

	return true
}

func (point *BackgroundGradientPoint) color(session Session) (Color, bool) {
	if point.Color != nil {
		switch color := point.Color.(type) {
		case string:
			if color != "" {
				if color[0] == '@' {
					if clr, ok := session.Color(color[1:]); ok {
						return clr, true
					}
				} else {
					if clr, ok := StringToColor(color); ok {
						return clr, true
					}
				}
			}

		case Color:
			return color, true
		}
	}
	return 0, false
}

func (gradient *backgroundGradient) writeGradient(session Session, buffer *strings.Builder) bool {

	value, ok := gradient.properties[Gradient]
	if !ok {
		return false
	}

	var points []BackgroundGradientPoint = nil

	switch value := value.(type) {
	case string:
		if value != "" && value[0] == '@' {
			if text, ok := session.Constant(value[1:]); ok {
				points = gradient.parseGradientText(text)
			}
		}

	case []BackgroundGradientPoint:
		points = value
	}

	if len(points) > 0 {
		for i, point := range points {
			if i > 0 {
				buffer.WriteString(`, `)
			}

			if color, ok := point.color(session); ok {
				buffer.WriteString(color.cssString())
			} else {
				return false
			}

			if point.Pos != nil {
				switch value := point.Pos.(type) {
				case string:
					if value != "" {
						if value[0] == '@' {
							value, _ = session.Constant(value[1:])
						}
						if pos, ok := StringToSizeUnit(value); ok && pos.Type != Auto {
							buffer.WriteRune(' ')
							buffer.WriteString(pos.cssString(""))
						}
					}

				case SizeUnit:
					if value.Type != Auto {
						buffer.WriteRune(' ')
						buffer.WriteString(value.cssString(""))
					}
				}
			}
		}
		return true
	}

	return false
}

func (gradient *backgroundLinearGradient) Tag() string {
	return "linear-gradient"
}

func (image *backgroundLinearGradient) Clone() BackgroundElement {
	result := NewBackgroundLinearGradient(nil)
	for tag, value := range image.properties {
		result.setRaw(tag, value)
	}
	return result
}

func (gradient *backgroundLinearGradient) Set(tag string, value any) bool {
	if strings.ToLower(tag) == Direction {
		switch value := value.(type) {
		case AngleUnit:
			gradient.properties[Direction] = value
			return true

		case string:
			if gradient.setSimpleProperty(tag, value) {
				return true
			}
			if angle, ok := StringToAngleUnit(value); ok {
				gradient.properties[Direction] = angle
				return true
			}
		}
		return gradient.setEnumProperty(tag, value, enumProperties[Direction].values)
	}

	return gradient.backgroundGradient.Set(tag, value)
}

func (gradient *backgroundLinearGradient) cssStyle(session Session) string {
	buffer := allocStringBuilder()
	defer freeStringBuilder(buffer)

	if repeating, _ := boolProperty(gradient, Repeating, session); repeating {
		buffer.WriteString(`repeating-linear-gradient(`)
	} else {
		buffer.WriteString(`linear-gradient(`)
	}

	if value, ok := gradient.properties[Direction]; ok {
		switch value := value.(type) {
		case string:
			if text, ok := session.resolveConstants(value); ok {
				direction := enumProperties[Direction]
				if n, ok := enumStringToInt(text, direction.values, false); ok {
					buffer.WriteString(direction.cssValues[n])
					buffer.WriteString(", ")
				} else {
					if angle, ok := StringToAngleUnit(text); ok {
						buffer.WriteString(angle.cssString())
						buffer.WriteString(", ")
					} else {
						ErrorLog(`Invalid linear gradient direction: ` + text)
					}
				}
			} else {
				ErrorLog(`Invalid linear gradient direction: ` + value)
			}

		case int:
			values := enumProperties[Direction].cssValues
			if value >= 0 && value < len(values) {
				buffer.WriteString(values[value])
				buffer.WriteString(", ")
			} else {
				ErrorLogF(`Invalid linear gradient direction: %d`, value)
			}

		case AngleUnit:
			buffer.WriteString(value.cssString())
			buffer.WriteString(", ")
		}
	}

	if !gradient.writeGradient(session, buffer) {
		return ""
	}

	buffer.WriteString(") ")
	return buffer.String()
}

func (gradient *backgroundRadialGradient) Tag() string {
	return "radial-gradient"
}

func (image *backgroundRadialGradient) Clone() BackgroundElement {
	result := NewBackgroundRadialGradient(nil)
	for tag, value := range image.properties {
		result.setRaw(tag, value)
	}
	return result
}

func (gradient *backgroundRadialGradient) normalizeTag(tag string) string {
	tag = strings.ToLower(tag)
	switch tag {
	case Radius:
		tag = RadialGradientRadius

	case Shape:
		tag = RadialGradientShape

	case "x-center":
		tag = CenterX

	case "y-center":
		tag = CenterY
	}

	return tag
}

func (gradient *backgroundRadialGradient) Set(tag string, value any) bool {
	tag = gradient.normalizeTag(tag)
	switch tag {
	case RadialGradientRadius:
		switch value := value.(type) {
		case []SizeUnit:
			switch len(value) {
			case 0:
				delete(gradient.properties, RadialGradientRadius)
				return true

			case 1:
				if value[0].Type == Auto {
					delete(gradient.properties, RadialGradientRadius)
				} else {
					gradient.properties[RadialGradientRadius] = value[0]
				}
				return true

			default:
				gradient.properties[RadialGradientRadius] = value
				return true
			}

		case []any:
			switch len(value) {
			case 0:
				delete(gradient.properties, RadialGradientRadius)
				return true

			case 1:
				return gradient.Set(RadialGradientRadius, value[0])

			default:
				gradient.properties[RadialGradientRadius] = value
				return true
			}

		case string:
			if gradient.setSimpleProperty(RadialGradientRadius, value) {
				return true
			}
			if size, err := stringToSizeUnit(value); err == nil {
				if size.Type == Auto {
					delete(gradient.properties, RadialGradientRadius)
				} else {
					gradient.properties[RadialGradientRadius] = size
				}
				return true
			}
			return gradient.setEnumProperty(RadialGradientRadius, value, enumProperties[RadialGradientRadius].values)

		case SizeUnit:
			if value.Type == Auto {
				delete(gradient.properties, RadialGradientRadius)
			} else {
				gradient.properties[RadialGradientRadius] = value
			}
			return true

		case int:
			n := value
			if n >= 0 && n < len(enumProperties[RadialGradientRadius].values) {
				return gradient.propertyList.Set(RadialGradientRadius, value)
			}
		}
		ErrorLogF(`Invalid value of "%s" property: %v`, tag, value)

	case RadialGradientShape, CenterX, CenterY:
		return gradient.propertyList.Set(tag, value)
	}

	return gradient.backgroundGradient.Set(tag, value)
}

func (gradient *backgroundRadialGradient) Get(tag string) any {
	return gradient.backgroundGradient.Get(gradient.normalizeTag(tag))
}

func (gradient *backgroundRadialGradient) cssStyle(session Session) string {
	buffer := allocStringBuilder()
	defer freeStringBuilder(buffer)

	if repeating, _ := boolProperty(gradient, Repeating, session); repeating {
		buffer.WriteString(`repeating-radial-gradient(`)
	} else {
		buffer.WriteString(`radial-gradient(`)
	}

	var shapeText string
	if shape, ok := enumProperty(gradient, RadialGradientShape, session, EllipseGradient); ok && shape == CircleGradient {
		shapeText = `circle `
	} else {
		shapeText = `ellipse `
	}

	if value, ok := gradient.properties[RadialGradientRadius]; ok {
		switch value := value.(type) {
		case string:
			if text, ok := session.resolveConstants(value); ok {
				values := enumProperties[RadialGradientRadius]
				if n, ok := enumStringToInt(text, values.values, false); ok {
					buffer.WriteString(shapeText)
					shapeText = ""
					buffer.WriteString(values.cssValues[n])
					buffer.WriteString(" ")
				} else {
					if r, ok := StringToSizeUnit(text); ok && r.Type != Auto {
						buffer.WriteString("ellipse ")
						shapeText = ""
						buffer.WriteString(r.cssString(""))
						buffer.WriteString(" ")
						buffer.WriteString(r.cssString(""))
						buffer.WriteString(" ")
					} else {
						ErrorLog(`Invalid radial gradient radius: ` + text)
					}
				}
			} else {
				ErrorLog(`Invalid radial gradient radius: ` + value)
			}

		case int:
			values := enumProperties[RadialGradientRadius].cssValues
			if value >= 0 && value < len(values) {
				buffer.WriteString(shapeText)
				shapeText = ""
				buffer.WriteString(values[value])
				buffer.WriteString(" ")
			} else {
				ErrorLogF(`Invalid radial gradient radius: %d`, value)
			}

		case SizeUnit:
			if value.Type != Auto {
				buffer.WriteString("ellipse ")
				shapeText = ""
				buffer.WriteString(value.cssString(""))
				buffer.WriteString(" ")
				buffer.WriteString(value.cssString(""))
				buffer.WriteString(" ")
			}

		case []SizeUnit:
			count := len(value)
			if count > 2 {
				count = 2
			}
			buffer.WriteString("ellipse ")
			shapeText = ""
			for i := 0; i < count; i++ {
				buffer.WriteString(value[i].cssString("50%"))
				buffer.WriteString(" ")
			}

		case []any:
			count := len(value)
			if count > 2 {
				count = 2
			}
			buffer.WriteString("ellipse ")
			shapeText = ""
			for i := 0; i < count; i++ {
				if value[i] != nil {
					switch value := value[i].(type) {
					case SizeUnit:
						buffer.WriteString(value.cssString("50%"))
						buffer.WriteString(" ")

					case string:
						if text, ok := session.resolveConstants(value); ok {
							if size, err := stringToSizeUnit(text); err == nil {
								buffer.WriteString(size.cssString("50%"))
								buffer.WriteString(" ")
							} else {
								buffer.WriteString("50% ")
							}
						} else {
							buffer.WriteString("50% ")
						}
					}
				} else {
					buffer.WriteString("50% ")
				}
			}
		}
	}

	x, _ := sizeProperty(gradient, CenterX, session)
	y, _ := sizeProperty(gradient, CenterX, session)
	if x.Type != Auto || y.Type != Auto {
		if shapeText != "" {
			buffer.WriteString(shapeText)
		}
		buffer.WriteString("at ")
		buffer.WriteString(x.cssString("50%"))
		buffer.WriteString(" ")
		buffer.WriteString(y.cssString("50%"))
	}

	buffer.WriteString(", ")
	if !gradient.writeGradient(session, buffer) {
		return ""
	}

	buffer.WriteString(") ")

	return buffer.String()
}