package org.openrndr.extra.shadestyles

import org.openrndr.color.ColorRGBa
import org.openrndr.draw.ShadeStyle
import org.openrndr.draw.shadeStyle
import org.openrndr.extra.parameters.ColorParameter
import org.openrndr.extra.parameters.Description
import org.openrndr.extra.parameters.DoubleParameter
import org.openrndr.math.Vector2

@Description("Linear gradient")
class LinearGradient(
        color0: ColorRGBa,
        color1: ColorRGBa,
        offset: Vector2,
        rotation: Double) : ShadeStyle() {

    @ColorParameter("start color", order = 0)
    var color0: ColorRGBa by Parameter()
    @ColorParameter("end color", order = 1)
    var color1: ColorRGBa by Parameter()
    var offset: Vector2 by Parameter()
    @DoubleParameter("rotation", -180.0, 180.0, order = 2)
    var rotation: Double by Parameter()

    init {
        this.color0 = color0
        this.color1 = color1
        this.offset = offset
        this.rotation = rotation

        fragmentTransform = """
            vec2 coord = (c_boundsPosition.xy - vec2(0.5) + p_offset);
            float cr = cos(radians(p_rotation));
            float sr = sin(radians(p_rotation));
            mat2 rm = mat2(cr, -sr, sr, cr);
            float f = clamp((rm * coord).y + 0.5, 0.0, 1.0);            
                
            vec4 color0 = p_color0 * vec4(p_color0.aaa, 1.0);
            vec4 color1 = p_color1 * vec4(p_color1.aaa, 1.0);

            vec4 gradient = color0 * (1.0-f) + color1 * f;
            
            vec4 fn = vec4(x_fill.rgb, 1.0) * x_fill.a;            
            
            x_fill = fn * gradient;
            if (x_fill.a !=0) {
                x_fill.rgb /= x_fill.a;
            }
        """
    }
}

fun linearGradient(color0: ColorRGBa, color1: ColorRGBa, offset: Vector2 = Vector2.ZERO, rotation: Double = 0.0) =
        LinearGradient(color0, color1, offset, rotation)