//! ----------------------------------------------------
//! ----------------------------------------------------

const std = @import("std");
const Vec = @import("vec.zig").Vec;

/// ----------------------------------------------------
/// ----------------------------------------------------
pub const Color = extern struct {
    const Self = @This();

    //
    // FIELDS
    //

    r: f32 = 0,
    g: f32 = 0,
    b: f32 = 0,
    a: f32 = 1,

    //
    // CONSTRUCTORS
    //

    /// ----------------------------------------------------
    /// ----------------------------------------------------
    pub inline fn rgb(r: f32, g: f32, b: f32) Self {
        return .{ .r = r, .g = g, .b = b, .a = 1 };
    }

    /// ----------------------------------------------------
    /// ----------------------------------------------------
    pub inline fn rgba(r: f32, g: f32, b: f32, a: f32) Self {
        return .{ .r = r, .g = g, .b = b, .a = a };
    }

    /// ----------------------------------------------------
    /// ----------------------------------------------------
    pub inline fn hex(comptime value: u32) Self {
        const r = @as(f32, @as(u8, @truncate(value >> 16))) / 255.0;
        const g = @as(f32, @as(u8, @truncate(value >> 8))) / 255.0;
        const b = @as(f32, @as(u8, @truncate(value >> 0))) / 255.0;
        const a = if (value > 0xFFFFFF)
            @as(f32, @as(u8, @truncate(value >> 24))) / 255.0
        else
            1.0;
        return .{ .r = r, .g = g, .b = b, .a = a };
    }

    /// ----------------------------------------------------
    /// ----------------------------------------------------
    pub inline fn fromVec4(v: Vec(f32, 4)) Self {
        return .{ .r = v.value[0], .g = v.value[1], .b = v.value[2], .a = v.value[3] };
    }

    /// ----------------------------------------------------
    /// ----------------------------------------------------
    pub inline fn toVec4(self: Self) Vec(f32, 4) {
        return Vec(f32, 4).new(.{ self.r, self.g, self.b, self.a });
    }

    //
    // ARITHMETIC
    //

    /// ----------------------------------------------------
    /// ----------------------------------------------------
    pub inline fn add(self: Self, other: Self) Self {
        return .{
            .r = self.r + other.r,
            .g = self.g + other.g,
            .b = self.b + other.b,
            .a = self.a + other.a,
        };
    }

    /// ----------------------------------------------------
    /// ----------------------------------------------------
    pub inline fn sub(self: Self, other: Self) Self {
        return .{
            .r = self.r - other.r,
            .g = self.g - other.g,
            .b = self.b - other.b,
            .a = self.a - other.a,
        };
    }

    /// ----------------------------------------------------
    /// ----------------------------------------------------
    pub inline fn mul(self: Self, other: Self) Self {
        return .{
            .r = self.r * other.r,
            .g = self.g * other.g,
            .b = self.b * other.b,
            .a = self.a * other.a,
        };
    }

    /// ----------------------------------------------------
    /// ----------------------------------------------------
    pub inline fn div(self: Self, other: Self) Self {
        return .{
            .r = self.r / other.r,
            .g = self.g / other.g,
            .b = self.b / other.b,
            .a = self.a / other.a,
        };
    }

    /// ----------------------------------------------------
    /// ----------------------------------------------------
    pub inline fn scale(self: Self, scalar: f32) Self {
        return .{
            .r = self.r * scalar,
            .g = self.g * scalar,
            .b = self.b * scalar,
            .a = self.a * scalar,
        };
    }

    //
    // COLOR OPERATIONS
    //

    /// ----------------------------------------------------
    /// ----------------------------------------------------
    pub inline fn lerp(self: Self, other: Self, t: f32) Self {
        return .{
            .r = self.r + (other.r - self.r) * t,
            .g = self.g + (other.g - self.g) * t,
            .b = self.b + (other.b - self.b) * t,
            .a = self.a + (other.a - self.a) * t,
        };
    }

    /// ----------------------------------------------------
    /// ----------------------------------------------------
    pub inline fn blend(self: Self, other: Self) Self {
        const out_a = other.a + self.a * (1.0 - other.a);
        if (out_a == 0) return .{ .r = 0, .g = 0, .b = 0, .a = 0 };
        return .{
            .r = (other.r * other.a + self.r * self.a * (1.0 - other.a)) / out_a,
            .g = (other.g * other.a + self.g * self.a * (1.0 - other.a)) / out_a,
            .b = (other.b * other.a + self.b * self.a * (1.0 - other.a)) / out_a,
            .a = out_a,
        };
    }

    /// ----------------------------------------------------
    /// ----------------------------------------------------
    pub inline fn premultiply(self: Self) Self {
        return .{
            .r = self.r * self.a,
            .g = self.g * self.a,
            .b = self.b * self.a,
            .a = self.a,
        };
    }

    /// ----------------------------------------------------
    /// ----------------------------------------------------
    pub inline fn luminance(self: Self) f32 {
        return self.r * 0.2126 + self.g * 0.7152 + self.b * 0.0722;
    }

    /// ----------------------------------------------------
    /// ----------------------------------------------------
    pub inline fn toLinear(self: Self) Self {
        const srgb_to_linear = struct {
            inline fn map(c: f32) f32 {
                if (c <= 0.04045) return c / 12.92;
                return std.math.pow(f32, (c + 0.055) / 1.055, 2.4);
            }
        };
        return .{
            .r = srgb_to_linear.map(self.r),
            .g = srgb_to_linear.map(self.g),
            .b = srgb_to_linear.map(self.b),
            .a = self.a,
        };
    }

    /// ----------------------------------------------------
    /// ----------------------------------------------------
    pub inline fn toSRGB(self: Self) Self {
        const linear_to_srgb = struct {
            inline fn map(c: f32) f32 {
                if (c <= 0.0031308) return c * 12.92;
                return 1.055 * std.math.pow(f32, c, 1.0 / 2.4) - 0.055;
            }
        };
        return .{
            .r = linear_to_srgb.map(self.r),
            .g = linear_to_srgb.map(self.g),
            .b = linear_to_srgb.map(self.b),
            .a = self.a,
        };
    }

    /// ----------------------------------------------------
    /// ----------------------------------------------------
    pub inline fn toHSV(self: Self) struct { h: f32, s: f32, v: f32 } {
        const max = @max(self.r, @max(self.g, self.b));
        const min = @min(self.r, @min(self.g, self.b));
        const delta = max - min;

        const v = max;
        const s = if (max == 0) 0 else delta / max;

        var h: f32 = 0;
        if (delta != 0) {
            if (max == self.r) {
                h = 60.0 * @mod((self.g - self.b) / delta, 6.0);
            } else if (max == self.g) {
                h = 60.0 * ((self.b - self.r) / delta + 2.0);
            } else {
                h = 60.0 * ((self.r - self.g) / delta + 4.0);
            }
        }
        return .{ .h = h, .s = s, .v = v };
    }

    /// ----------------------------------------------------
    /// ----------------------------------------------------
    pub inline fn fromHSV(h: f32, s: f32, v: f32) Self {
        const c = v * s;
        const hp = h / 60.0;
        const x = c * (1.0 - @abs(@mod(hp, 2.0) - 1.0));
        const m = v - c;

        var r: f32 = 0;
        var g: f32 = 0;
        var b: f32 = 0;

        if (hp < 1) {
            r = c;
            g = x;
        } else if (hp < 2) {
            r = x;
            g = c;
        } else if (hp < 3) {
            g = c;
            b = x;
        } else if (hp < 4) {
            g = x;
            b = c;
        } else if (hp < 5) {
            r = x;
            b = c;
        } else {
            r = c;
            b = x;
        }

        return .{ .r = r + m, .g = g + m, .b = b + m, .a = 1 };
    }

    //
    // CONSTANTS
    //

    pub const white = Self{ .r = 1, .g = 1, .b = 1, .a = 1 };
    pub const black = Self{ .r = 0, .g = 0, .b = 0, .a = 1 };
    pub const transparent = Self{ .r = 0, .g = 0, .b = 0, .a = 0 };

    pub const red = Self{ .r = 1, .g = 0, .b = 0, .a = 1 };
    pub const green = Self{ .r = 0, .g = 1, .b = 0, .a = 1 };
    pub const blue = Self{ .r = 0, .g = 0, .b = 1, .a = 1 };

    pub const yellow = Self{ .r = 1, .g = 1, .b = 0, .a = 1 };
    pub const cyan = Self{ .r = 0, .g = 1, .b = 1, .a = 1 };
    pub const magenta = Self{ .r = 1, .g = 0, .b = 1, .a = 1 };

    pub const orange = Self{ .r = 1, .g = 0.55, .b = 0, .a = 1 };
    pub const purple = Self{ .r = 0.5, .g = 0, .b = 0.5, .a = 1 };
    pub const pink = Self{ .r = 1, .g = 0.75, .b = 0.8, .a = 1 };
    pub const brown = Self{ .r = 0.6, .g = 0.3, .b = 0.1, .a = 1 };
    pub const gray = Self{ .r = 0.5, .g = 0.5, .b = 0.5, .a = 1 };
};