const Transform = @This();

const math = @import("math.zig");

base: math.Mat4x4,
translation: math.Mat4x4,
scale: math.Mat4x4,

pub fn init() Transform {
    return .{
        .base = .id,
        .translation = .id,
        .scale = .id,
    };
}

const TransformType = enum {
    orthographic,
    translation,
    scale,
};

pub fn set(transform: *Transform, tag: TransformType, transformation: math.Mat4x4) void {
    switch (tag) {
        .orthographic => transform.base        = transformation,
        .translation  => transform.translation = transformation,
        .scale        => transform.scale       = transformation,
    }
}

pub fn add(transform: *Transform, tag: TransformType, transformation: math.Mat4x4) void {
    switch (tag) {
        .orthographic => @compileError("you shouldn't add to orthographic transformation, use `.set` instead!"),
        .translation  => transform.translation.mult(transformation),
        .scale        => transform.scale.mult(transformation),
    }
}

pub fn get(transform: *Transform) math.Mat4x4 {
    const width: f32 = 2.0 / transform.base.data[0][0];
    const height: f32 = 2.0 / transform.base.data[1][1];

    var result = transform.base;
    result.mult(math.Mat4x4.translation(math.Vec2 { width/2.0, height/2.0 }));
    result.mult(transform.scale);
    result.mult(math.Mat4x4.translation(math.Vec2 { -width/2.0, -height/2.0 }));

    result.mult(transform.translation);

    return result;
}