#version 330 core

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

in vec3 f_pos;
in vec3 f_norm;
in vec2 v_pos_orig;
// in vec4 f_shadow;
// in vec4 f_square;

out vec4 tgt_color;

#include <sky.glsl>

void main() {
    // vec3 f_pos = lod_pos(f_pos.xy);
	// vec3 f_col = lod_col(f_pos.xy);

    // vec4 vert_pos4 = view_mat * vec4(f_pos, 1.0);
    // vec3 view_dir = normalize(-vec3(vert_pos4)/* / vert_pos4.w*/);

    float my_alt = /*f_pos.z;*/alt_at_real(f_pos.xy);
    // vec3 f_pos = vec3(f_pos.xy, max(my_alt, f_pos.z));
	/* gl_Position =
		proj_mat *
		view_mat *
		vec4(f_pos, 1);
	gl_Position.z = -1000.0 / (gl_Position.z + 10000.0); */
    vec3 my_pos = vec3(f_pos.xy, my_alt);
	vec3 my_norm = lod_norm(f_pos.xy/*, f_square*/);

    float which_norm = dot(my_norm, normalize(cam_pos.xyz - my_pos));
    // which_norm = 0.5 + which_norm * 0.5;
    which_norm = pow(max(0.0, which_norm), /*0.03125*/1 / 8.0);// * 0.5;
    // which_norm = mix(0.0, 1.0, which_norm > 0.0);
	// vec3 normals[6] = vec3[](vec3(-1,0,0), vec3(1,0,0), vec3(0,-1,0), vec3(0,1,0), vec3(0,0,-1), vec3(0,0,1));
    vec3 f_norm = mix(faceforward(f_norm, cam_pos.xyz - f_pos, -f_norm), my_norm, which_norm);
    vec3 f_pos = mix(f_pos, my_pos, which_norm);
    // vec3 fract_pos = fract(f_pos);
    /* if (length(f_pos - cam_pos.xyz) <= view_distance.x + 32.0) {
        vec4 new_f_pos;
        float depth = 10000000.0;
        vec4 old_coord = all_mat * vec4(f_pos.xyz, 1.0);
        for (int i = 0; i < 6; i ++) {
            // vec4 square = focus_pos.xy + vec4(splay(pos - vec2(1.0, 1.0), splay(pos + vec2(1.0, 1.0))));
            vec3 my_f_norm = normals[i];
            vec3 my_f_tan = normals[(i + 2) % 6];
            vec3 my_f_bitan = normals[(i + 4) % 6];
            mat4 foo = mat4(vec4(my_f_tan, 0), vec4(my_f_bitan, 0), vec4(my_f_norm, 0), vec4(0, 0, 0, 1));
            mat4 invfoo = foo * inverse(foo * all_mat);
            vec4 my_f_pos = invfoo * (old_coord);//vec4(f_pos, 1.0);
            vec4 my_f_proj = all_mat * my_f_pos;
            if (my_f_proj.z <= depth) {
                new_f_pos = my_f_pos;
                f_norm = my_f_norm;
                depth = my_f_proj.z;
            }
	    }
        // f_pos = new_f_pos.xyz;
    } */

    // Test for distance to all 6 sides of the enclosing cube.
    // if (/*any(lessThan(fract(f_pos.xy), 0.01))*/fract_pos.x <= 0.1) {
    //     f_norm = faceforward(vec3(-1, 0, 0), f_norm, vec3(1, 0, 0));
    //     f_tan = vec3(0, 1, 0);
    // } else if (fract_pos.y <= 0.1) {
    //     f_norm = faceforward(vec3(0, -1, 0), f_norm, vec3(0, 1, 0));
    //     f_tan = vec3(0, 0, 1);
    // } else {
    //     f_norm = faceforward(vec3(0, 0, -1), f_norm, vec3(0, 0, 1));
    //     f_tan = vec3(1, 0, 0);
    // }
    // vec3 f_bitan = cross(f_norm, f_tan);

    // mat4 foo = mat4(vec4(f_tan, 0), vec4(f_bitan, 0), vec4(f_norm, 0), vec4(0, 0, 0, 1));
    // mat4 invfoo = foo * inverse(foo * all_mat);
    // vec3 old_coord = all_mat * vec4(f_pos.xyz, 1.0);
    // vec4 new_f_pos = invfoo * (old_coord);//vec4(f_pos, 1.0);
	vec3 f_col = lod_col(f_pos.xy);
    // vec3 f_norm = faceforward(f_norm, cam_pos.xyz - f_pos, -f_norm);
    // vec3 f_up = faceforward(cam_pos.xyz - f_pos, vec3(0.0, 0.0, -1.0), cam_pos.xyz - f_pos);
    // vec3 f_norm = faceforward(f_norm, /*vec3(cam_pos.xyz - f_pos.xyz)*/vec3(0.0, 0.0, -1.0), f_norm);

    vec3 cam_to_frag = normalize(f_pos - cam_pos.xyz);
    vec3 view_dir = -cam_to_frag;
    // vec3 view_dir = normalize(f_pos - cam_pos.xyz);

    // const vec3 normals[3] = vec3[](vec3(1,0,0), vec3(0,1,0), vec3(0,0,1));//, vec3(-1,0,0), vec3(0,-1,0), vec3(0,0,-1));
    // const mat3 side_norms = vec3(1, 0, 0), vec3(0, 1, 0), vec3(0, 0, 1);
    // mat3 sides = mat3(
    //     /*vec3(1, 0, 0),
    //     vec3(0, 1, 0),
    //     vec3(0, 0, 1)*/
    //     vec3(1, 0, 0),
    //     // faceforward(vec3(1, 0, 0), -f_norm, vec3(1, 0, 0)),
    //     vec3(0, 1, 0),
    //     // faceforward(vec3(0, 1, 0), -f_norm, vec3(0, 1, 0)),
    //     vec3(0, 0, 1)
    //     // faceforward(vec3(0, 0, 1), -f_norm, vec3(0, 0, 1))
    // );

    // This vector is shorthand for a diagonal matrix, which works because:
    // (1) our voxel normal vectors are exactly the basis vectors in worldspace;
    // (2) only 3 of them can be in the direction of the actual normal anyway.
    // (NOTE: This normal should always be pointing up, so implicitly sides.z = 1.0).
    // vec3 sides = sign(f_norm);
    // // NOTE: Should really be sides * f_norm, i.e. abs(f_norm), but voxel_norm would then re-multiply by sides so it cancels out.
    // vec3 cos_sides_i = sides * f_norm;
    // vec3 cos_sides_o = sides * view_dir;
    // // vec3 side_factor_i = cos_sides_i;
    // // vec3 side_factor_i = f_norm;
    // // vec3 side_factor_i = cos_sides_o;
    // vec3 side_factor_i = 1.0 - pow(1.0 - 0.5 * cos_sides_i, vec3(5));
    // // vec3 side_factor_i = /*abs*/sign(f_norm) * cos_sides_i;//max(cos_sides_i, 0.0);// 1.0 - pow(1.0 - 0.5 * cos_sides_i, vec3(5.0)); // max(sides * f_norm, vec3(0.0));//
    // // vec3 side_factor_i = /*abs*/sign(f_norm) * cos_sides_i;//max(cos_sides_i, 0.0);// 1.0 - pow(1.0 - 0.5 * cos_sides_i, vec3(5.0)); // max(sides * f_norm, vec3(0.0));//
    // // vec3 side_factor_o = max(cos_sides_o, 0.0);// 1.0 - pow(1.0 - 0.5 * max(cos_sides_o, 0.0), vec3(5));
    // vec3 side_factor_o = 1.0 - pow(1.0 - 0.5 * max(cos_sides_o, 0.0), vec3(5));
    // // vec3 side_factor_o = max(cos_sides_o, 0.0);// 1.0 - pow(1.0 - 0.5 * max(cos_sides_o, vec3(0.0)), vec3(5.0));//max(sides * view_dir/* * sign(cos_sides_i) */, vec3(0.0));
    // // vec3 side_factor_o = max(sides * view_dir/* * cos_sides_o*/, 0.0);// 1.0 - pow(1.0 - 0.5 * max(cos_sides_o, vec3(0.0)), vec3(5.0));//max(sides * view_dir/* * sign(cos_sides_i) */, vec3(0.0));
    // // NOTE: side = transpose(sides), so we avoid the extra operatin.
    // // We multply the vector by the matrix from the *left*, so each normal gets multiplied by the corresponding factor.
    // // vec3 voxel_norm = normalize(/*sides * *//*sqrt(1.0 - cos_sides_i * cos_sides_i)*/(side_factor_i * side_factor_o));
    // vec3 voxel_norm = normalize(/*sides * *//*sqrt(1.0 - cos_sides_i * cos_sides_i)*/((28.0 / (23.0 * PI)) * side_factor_i * side_factor_o * sides));
    // vec3 voxel_norm = normalize(sign(f_norm) * sqrt(abs(f_norm)) * max(sign(f_norm) * view_dir, 0.0));
    float f_ao = 1.0;//1.0;//sqrt(dot(cos_sides_i, cos_sides_i) / 3.0);
    // float f_ao = 0.2;
    // sqrt(dot(sqrt(1.0 - cos_sides_i * cos_sides_i)), 1.0 - cos_sides_o/* * cos_sides_o*/);// length(sqrt(1.0 - cos_sides_o * cos_sides_o) / cos_sides_i * cos_sides_o);
    // f_ao = f_ao * f_ao;

    // /* vec3 voxel_norm = vec3(0.0);
    // for (int i = 0; i < 3; i ++) {
    //     // Light reflecting off the half-angle can shine on up to three sides.
    //     // So, the idea here is to figure out the ratio of visibility of each of these
    //     // three sides such that their sum adds to 1, then computing a Beckmann Distribution for each side times
    //     // the this ratio.
    //     //
    //     // The ratio of these normals in each direction should be the sum of their cosines with the light over π,
    //     // I think.
    //     //
    //     // cos (wh, theta)
    //     //
    //     // - one normal
    //     //
    //     // The ratio of each of the three exposed sides should just be the slope.
    //     vec3 side = normals[i];
    //     side = faceforward(side, -f_norm, side);
    //     float cos_wi = max(dot(f_norm, side), 0.0);
    //     float cos_wo = max(dot(view_dir, side), 0.0);
    //     float share = cos_wi * cos_wo;
    //     // float share = (1.0 - pow5(1.0 - 0.5 * cos_wi)) * (1.0 - pow5(1.0 - 0.5 * cos_wo));
    //     voxel_norm += share * side;
    //     // voxel_norm += normals[i] * side_visible * max(dot(-cam_dir, normals[i]), 0.0);
    //     // voxel_norm += normals[i] * side_visible * max(dot(-cam_dir, normals[i]), 0.0);
    // }
    // voxel_norm = normalize(voxel_norm); */

    float dist_lerp = clamp(pow(max(distance(focus_pos.xy, f_pos.xy) - view_distance.x, 0.0) / 1024.0, 2.0), 0, 1);
    // dist_lerp = 0.0;
    // voxel_norm = normalize(mix(voxel_norm, f_norm, /*pow(dist_lerp, 1.0)*/dist_lerp));

    vec3 voxel_norm = f_norm;
    // voxel_norm = f_norm;

    // Note: because voxels, we reduce the normal for reflections to just its z component, dpendng on distance to camera.
    // Idea: the closer we are to facing top-down, the more the norm should tend towards up-z.
    // vec3 l_norm; // = vec3(0.0, 0.0, 1.0);
    // vec3 l_norm = normalize(vec3(f_norm.x / max(abs(f_norm.x), 0.001), f_norm.y / max(abs(f_norm.y), 0.001), f_norm.z / max(abs(f_norm.z), 0.001)));
    // vec3 l_factor = 1.0 / (1.0 + max(abs(/*f_pos - cam_pos.xyz*//*-vec3(vert_pos4) / vert_pos4.w*/vec3(f_pos.xy, 0.0) - vec3(/*cam_pos*/focus_pos.xy, cam_to_frag)) - vec3(view_distance.x, view_distance.x, 0.0), 0.0) / vec3(32.0 * 2.0, 32.0 * 2.0, 1.0));
    // l_factor.z =
    // vec4 focus_pos4 = view_mat * vec4(focus_pos.xyz, 1.0);
    // vec3 focus_dir = normalize(-vec3(focus_pos4) / focus_pos4.w);

    // float l_factor = 1.0 - pow(clamp(0.5 + 0.5 * dot(/*-view_dir*/-cam_to_frag, l_norm), 0.0, 1.0), 2.0);//1.0 / (1.0 + 0.5 * pow(max(distance(/*focus_pos.xy*/vec3(focus_pos.xy, /*vert_pos4.z / vert_pos4.w*/f_pos.z), vec3(f_pos.xy, f_pos.z))/* - view_distance.x*/ - 32.0, 0.0) / (32.0 * 1.0), /*0.5*/1.0));
    // l_factor = 1.0;
    // l_norm = normalize(mix(l_norm, f_norm, l_factor));
    // l_norm = f_norm;

    /* l_norm = normalize(vec3(
            mix(l_norm.x, f_norm.x, clamp(pow(f_norm.x * 0.5, 64), 0, 1)),
            mix(-1.0, 1.0, clamp(pow(f_norm.y * 0.5, 64), 0, 1)),
            mix(-1.0, 1.0, clamp(pow(f_norm.z * 0.5, 64), 0, 1))
        )); */
    // f_norm = mix(l_norm, f_norm, min(1.0 / max(cam_to_frag, 0.001), 1.0));
    /* vec3 l_norm = normalize(vec3(
            mix(-1.0, 1.0, clamp(pow(f_norm.x * 0.5, 64), 0, 1)),
            mix(-1.0, 1.0, clamp(pow(f_norm.y * 0.5, 64), 0, 1)),
            mix(-1.0, 1.0, clamp(pow(f_norm.z * 0.5, 64), 0, 1))
        )); */

    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 my_alt = f_pos.z;//alt_at_real(f_pos.xy);
    // vec3 f_norm = my_norm;
    vec4 f_shadow = textureBicubic(t_horizon, pos_to_tex(f_pos.xy));
    // float my_alt = alt_at(f_pos.xy);
    float shadow_alt = /*f_pos.z;*/alt_at(f_pos.xy);
    float sun_shade_frac = horizon_at2(f_shadow, shadow_alt, f_pos, sun_dir);
    float moon_shade_frac = horizon_at2(f_shadow, shadow_alt, f_pos, moon_dir);
    // float sun_shade_frac = horizon_at(/*f_shadow, f_pos.z, */f_pos, sun_dir);
    // float moon_shade_frac = horizon_at(/*f_shadow, f_pos.z, */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;
    // float brightness_denominator = (ambient_sides + vec3(SUN_AMBIANCE * sun_light + moon_light);

    float alpha = 1.0;//0.1;//0.2;///1.0;//sqrt(2.0);
    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 < my_alt) ? mix(R_s2s1 * R_s1s0, R_s1s0, medium.x) : mix(R_s2s0, R_s1s2 * R_s2s0, medium.x);

	vec3 emitted_light, reflected_light;
    // Use f_norm here for better shadows.
    // vec3 light_frac = light_reflection_factor(f_norm/*l_norm*/, view_dir, vec3(0, 0, -1.0), vec3(1.0), vec3(/*1.0*/R_s), alpha);

	// vec3 light, diffuse_light, ambient_light;
    // get_sun_diffuse(f_norm, time_of_day.x, cam_to_frag, (0.25 * shade_frac + 0.25 * light_frac) * f_col, 0.5 * shade_frac * f_col, 0.5 * shade_frac * /*vec3(1.0)*/f_col, 2.0, emitted_light, reflected_light);
    float max_light = 0.0;
    max_light += get_sun_diffuse2(/*f_norm*/voxel_norm/*l_norm*/, sun_dir, moon_dir, view_dir, vec3(1.0)/* * (0.5 * light_frac + vec3(0.5 * shade_frac))*/, vec3(1.0), /*0.5 * shade_frac * *//*vec3(1.0)*//*f_col*/vec3(R_s), alpha, dist_lerp/*max(distance(focus_pos.xy, f_pos.xyz) - view_distance.x, 0.0) / 1000 < 1.0*/, emitted_light, reflected_light);
    // emitted_light = vec3(1.0);
    emitted_light *= max(shade_frac, MIN_SHADOW);
    reflected_light *= shade_frac;
    max_light *= shade_frac;
    // reflected_light = vec3(0.0);

	float ao = /*pow(f_ao, 0.5)*/f_ao * 0.9 + 0.1;
	emitted_light *= ao;
	reflected_light *= ao;

    // emitted_light += 0.5 * vec3(SUN_AMBIANCE * sun_shade_frac * sun_light + moon_shade_frac * moon_light) * f_col * (ambient_sides + 1.0);

    // Ambient lighting attempt: vertical light.
    // reflected_light += /*0.0125*/0.15 * 0.25 * _col * light_reflection_factor(f_norm, cam_to_frag, vec3(0, 0, -1.0), 0.5 * f_col, 0.5 * f_col, 2.0);
    // emitted_light += /*0.0125*/0.25 * f_col * ;
	// vec3 light, diffuse_light, ambient_light;
	// get_sun_diffuse(f_norm, time_of_day.x, light, diffuse_light, ambient_light, 1.0);
	// vec3 surf_color = illuminate(f_col, light, diffuse_light, ambient_light);
	// f_col = f_col + (hash(vec4(floor(vec3(focus_pos.xy + splay(v_pos_orig), f_pos.z)) * 3.0 - round(f_norm) * 0.5, 0)) - 0.5) * 0.05; // Small-scale noise
    vec3 surf_color = /*illuminate(emitted_light, reflected_light)*/illuminate(max_light, f_col * emitted_light, f_col * reflected_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, 1.0, true, clouds);
	vec3 color = mix(mix(surf_color, fog_color, fog_level), clouds.rgb, clouds.a);
    // vec3 color = surf_color;

	// float mist_factor = max(1 - (f_pos.z + (texture(t_noise, f_pos.xy * 0.0005 + time_of_day.x * 0.0003).x - 0.5) * 128.0) / 400.0, 0.0);
	// //float mist_factor = f_norm.z * 2.0;
	// color = mix(color, vec3(1.0) * /*diffuse_light*/reflected_light, clamp(mist_factor * 0.00005 * distance(f_pos.xy, focus_pos.xy), 0, 0.3));
    // color = surf_color;

	tgt_color = vec4(color, 1.0);
}