/* quad vertex shader */
@vs vs
const vec2 positions[4] = { vec2(0, 1), vec2(1, 1), vec2(1, 0), vec2(0, 0) };
const vec2 uvs[4] = { vec2(0, 0), vec2(1, 0), vec2(1, 1), vec2(0, 1) };
const int indices[6] = { 0, 1, 2, 0, 2, 3 };

layout(binding=0) uniform Game
{
    vec2 screen;
    vec2 cam;
};

in vec2 inst_pos;
in ivec2 inst_size;
out vec2 uv;

void main() {
    int idx = indices[gl_VertexIndex];
    vec2 pos = positions[idx];
    uv = uvs[idx];

    vec2 inst_pos_abs = inst_pos + inst_size * pos - cam - screen / 2;
    gl_Position = vec4(inst_pos_abs / screen * 2, 1, 1);
}
@end

/* quad fragment shader */
@fs fs
layout(binding=0) uniform texture2D tex;
layout(binding=0) uniform sampler smp;

in vec2 uv;
out vec4 frag_color;

void main() {
    vec4 tex_color = texture(sampler2D(tex, smp), uv);
    if (tex_color.a < 1)
        discard;
    frag_color = tex_color;
}
@end

/* quad shader program */
@program quad vs fs





@vs vs_shadow
const vec2 positions[4] = { vec2(0, 1), vec2(1, 1), vec2(1, 0), vec2(0, 0) };
const vec2 uvs[4] = { vec2(0, 0), vec2(1, 0), vec2(1, 1), vec2(0, 1) };
const int indices[6] = { 0, 1, 2, 0, 2, 3 };

layout(binding=0) uniform Game
{
    vec2 screen;
    vec2 cam;
};

layout(binding=1) uniform Light
{
    vec2 light_pos;
};

in vec2 inst_pos;
in ivec2 inst_size;
out vec2 uv;

vec2 rotate(vec2 v, float a) {
	float s = sin(a);
	float c = cos(a);
	mat2 m = mat2(c, s, -s, c);
	return m * v;
}

void main() {
    int idx = indices[gl_VertexIndex];
    vec2 pos = positions[idx];
    uv = uvs[idx];

    if (idx == 2 || idx == 3) { // keep pos for lower vertices (base)
        vec2 inst_pos_abs = inst_pos + inst_size * pos - cam - screen / 2;
        gl_Position = vec4(inst_pos_abs / screen * 2, 1, 1);
    }
    else {
        vec2 anchor = vec2(0.5, 0);
        vec2 anchor_abs = inst_pos + inst_size * anchor - cam - screen / 2;
        vec2 light_pos_abs = light_pos - cam - screen / 2;
        vec2 dir = anchor_abs - light_pos_abs;

        vec2 left_right[] = {
            rotate(dir, 1.5708),
            rotate(dir, -1.5708),
        };

        vec2 inst_pos_abs = anchor_abs + dir + left_right[idx] / 2;
        gl_Position = vec4(inst_pos_abs / screen * 2, 1, 1);
    }
}
@end

@fs fs_shadow
layout(binding=0) uniform texture2D tex;
layout(binding=0) uniform sampler smp;

in vec2 uv;
out vec4 frag_color;

void main() {
    vec4 tex_color = texture(sampler2D(tex, smp), uv);
    // if (tex_color.a < 1)
    //     discard;
    frag_color = vec4(0, 0, 0, 1);
}
@end

@program shadow vs_shadow fs_shadow



@vs vs_light
const vec2 positions[4] = { vec2(-0.5, 0.5), vec2(0.5, 0.5), vec2(0.5, -0.5), vec2(-0.5, -0.5) };
const int indices[6] = { 0, 1, 2, 0, 2, 3 };

layout(binding=0) uniform Game
{
    vec2 screen;
    vec2 cam;
};

in vec2 light_pos;

void main() {
    int idx = indices[gl_VertexIndex];
    vec2 pos = positions[idx];

    vec2 light_size = vec2(10, 10);

    vec2 inst_pos_abs = light_pos + light_size * pos - cam - screen / 2;
    gl_Position = vec4(inst_pos_abs / screen * 2, 1, 1);
}
@end

@fs fs_light
out vec4 frag_color;

void main() {
    frag_color = vec4(1, 0, 0, 1);
}
@end

@program light vs_light fs_light