#version 330 core

#include <globals.glsl>

in vec3 f_pos;
flat in vec3 f_norm;
in vec3 f_col;
in float f_ao;
// in float f_light;

out vec4 tgt_color;

#include <sky.glsl>
#include <light.glsl>
#include <lod.glsl>

const float FADE_DIST = 32.0;

void main() {
    vec3 cam_to_frag = normalize(f_pos - cam_pos.xyz);
    // vec4 vert_pos4 = view_mat * vec4(f_pos, 1.0);
    // vec3 view_dir = normalize(-vec3(vert_pos4)/* / vert_pos4.w*/);
    vec3 view_dir = -cam_to_frag;

    vec3 sun_dir = get_sun_dir(time_of_day.x);
    vec3 moon_dir = get_moon_dir(time_of_day.x);
    // float sun_light = get_sun_brightness(sun_dir);
	// float moon_light = get_moon_brightness(moon_dir);
    float f_alt = alt_at(f_pos.xy);
    vec4 f_shadow = textureBicubic(t_horizon, pos_to_tex(f_pos.xy));
    float sun_shade_frac = horizon_at2(f_shadow, f_alt, f_pos, sun_dir);
    float moon_shade_frac = horizon_at2(f_shadow, f_alt, f_pos, moon_dir);
    // float sun_shade_frac = horizon_at(f_pos, sun_dir);
    // float moon_shade_frac = horizon_at(f_pos, moon_dir);
    // Globbal illumination "estimate" used to light the faces of voxels which are parallel to the sun or moon (which is a very common occurrence).
    // Will be attenuated by k_d, which is assumed to carry any additional ambient occlusion information (e.g. about shadowing).
    // float ambient_sides = clamp(mix(0.5, 0.0, abs(dot(-f_norm, sun_dir)) * 10000.0), 0.0, 0.5);
    // NOTE: current assumption is that moon and sun shouldn't be out at the sae time.
    // This assumption is (or can at least easily be) wrong, but if we pretend it's true we avoids having to explicitly pass in a separate shadow
    // for the sun and moon (since they have different brightnesses / colors so the shadows shouldn't attenuate equally).
    float shade_frac = sun_shade_frac + moon_shade_frac;

	vec3 surf_color = /*srgb_to_linear*//*linear_to_srgb*/(f_col);
    float alpha = 1.0;
    const float n2 = 1.01;
    const float R_s2s0 = pow((1.0 - n2) / (1.0 + n2), 2);
    const float R_s1s0 = pow((1.3325 - n2) / (1.3325 + n2), 2);
    const float R_s2s1 = pow((1.0 - 1.3325) / (1.0 + 1.3325), 2);
    const float R_s1s2 = pow((1.3325 - 1.0) / (1.3325 + 1.0), 2);
    float R_s = (f_pos.z < f_alt) ? mix(R_s2s1 * R_s1s0, R_s1s0, medium.x) : mix(R_s2s0, R_s1s2 * R_s2s0, medium.x);

    vec3 k_a = vec3(1.0);
    vec3 k_d = vec3(1.0);
    vec3 k_s = vec3(R_s);

    vec3 emitted_light, reflected_light;

	float point_shadow = shadow_at(f_pos, f_norm);
    // To account for prior saturation.
    // float vert_light = pow(f_light, 1.5);
    // vec3 light_frac = light_reflection_factor(f_norm/*vec3(0, 0, 1.0)*/, view_dir, vec3(0, 0, -1.0), vec3(1.0), vec3(R_s), alpha);
    /* light_frac += light_reflection_factor(f_norm, view_dir, vec3(1.0, 0, 0.0), vec3(1.0), vec3(1.0), 2.0);
    light_frac += light_reflection_factor(f_norm, view_dir, vec3(-1.0, 0, 0.0), vec3(1.0), vec3(1.0), 2.0);
    light_frac += light_reflection_factor(f_norm, view_dir, vec3(0.0, -1.0, 0.0), vec3(1.0), vec3(1.0), 2.0);
    light_frac += light_reflection_factor(f_norm, view_dir, vec3(0.0, 1.0, 0.0), vec3(1.0), vec3(1.0), 2.0); */

	// vec3 light, diffuse_light, ambient_light;
    // vec3 emitted_light, reflected_light;
	// float point_shadow = shadow_at(f_pos,f_norm);
	// vec3 point_light = light_at(f_pos, f_norm);
	// vec3 surf_color = srgb_to_linear(vec3(0.2, 0.5, 1.0));
    // vec3 cam_to_frag = normalize(f_pos - cam_pos.xyz);
    float max_light = 0.0;
    max_light += get_sun_diffuse2(f_norm, /*time_of_day.x, */sun_dir, moon_dir, /*cam_to_frag*/view_dir, k_a/* * (shade_frac * 0.5 + light_frac * 0.5)*/, k_d, k_s, alpha, emitted_light, reflected_light);
    reflected_light *= /*vert_light * */point_shadow * shade_frac;
    emitted_light *= /*vert_light * */point_shadow * max(shade_frac, MIN_SHADOW);
    max_light *= /*vert_light * */point_shadow * shade_frac;
	// get_sun_diffuse(f_norm, time_of_day.x, light, diffuse_light, ambient_light, 1.0);
	// float point_shadow = shadow_at(f_pos, f_norm);
	// diffuse_light *= f_light * point_shadow;
	// ambient_light *= f_light * point_shadow;
	// light += point_light;
	// diffuse_light += point_light;
    // reflected_light += point_light;

    max_light += lights_at(f_pos, f_norm, view_dir, k_a, k_d, k_s, alpha, emitted_light, reflected_light);
    /* vec3 point_light = light_at(f_pos, f_norm);
    emitted_light += point_light;
    reflected_light += point_light; */

	float ao = /*pow(f_ao, 0.5)*/f_ao * 0.85 + 0.15;
	emitted_light *= ao;
	reflected_light *= ao;

	surf_color = illuminate(max_light, surf_color * emitted_light, surf_color * reflected_light);
	// vec3 surf_color = illuminate(f_col, light, diffuse_light, ambient_light);

	float fog_level = fog(f_pos.xyz, focus_pos.xyz, medium.x);
	vec4 clouds;
	vec3 fog_color = get_sky_color(cam_to_frag/*view_dir*/, time_of_day.x, cam_pos.xyz, f_pos, 0.5, true, clouds);
	vec3 color = mix(mix(surf_color, fog_color, fog_level), clouds.rgb, clouds.a);

	tgt_color = vec4(color, 1.0 - clamp((distance(focus_pos.xy, f_pos.xy) - (sprite_render_distance - FADE_DIST)) / FADE_DIST, 0, 1));
}