#include "ingame.h"
#include "title.h"
#include "scene.h"

#include "twn_game_api.h"
#include "twn_vec.h"

#define STB_PERLIN_IMPLEMENTATION
#include <stb_perlin.h>
#include <SDL2/SDL.h>

#include <stdlib.h>


#define TERRAIN_FREQUENCY 0.1f
#define TERRAIN_DISTANCE 32
#define HALF_TERRAIN_DISTANCE ((float)TERRAIN_DISTANCE / 2)
#define PLAYER_HEIGHT 0.7f

static float heightmap[TERRAIN_DISTANCE][TERRAIN_DISTANCE];


static void process_fly_mode(State *state) {
    SceneIngame *scn = (SceneIngame *)state->scene;

    DrawCameraFromPrincipalAxesResult dir_and_up =
        draw_camera_from_principal_axes(scn->pos, (float)M_PI_2, scn->roll, scn->pitch, scn->yaw);

    const Vec3 right = m_vec_norm(m_vec_cross(dir_and_up.direction, dir_and_up.up));
    const float speed = 0.04f; /* TODO: put this in a better place */
    if (input_action_pressed("player_left"))
        scn->pos = vec3_sub(scn->pos, m_vec_scale(right, speed));

    if (input_action_pressed("player_right"))
        scn->pos = vec3_add(scn->pos, m_vec_scale(right, speed));

    if (input_action_pressed("player_forward"))
        scn->pos = vec3_add(scn->pos, m_vec_scale(dir_and_up.direction, speed));

    if (input_action_pressed("player_backward"))
        scn->pos = vec3_sub(scn->pos, m_vec_scale(dir_and_up.direction, speed));

    if (input_action_pressed("player_jump"))
        scn->pos.y += speed;

    if (input_action_pressed("player_run"))
        scn->pos.y -= speed;
}


static void process_ground_mode(State *state) {
    SceneIngame *scn = (SceneIngame *)state->scene;

    DrawCameraFromPrincipalAxesResult dir_and_up =
        draw_camera_from_principal_axes(scn->pos, (float)M_PI_2, scn->roll, scn->pitch, scn->yaw);

    const Vec3 right = m_vec_norm(m_vec_cross(dir_and_up.direction, dir_and_up.up));
    const float speed = 0.18f; /* TODO: put this in a better place */

    Vec3 target = scn->pos;

    /* gravity */
    {
        float height0, height1, height2, weight0, weight1, weight2;

        height0 = heightmap[(int)HALF_TERRAIN_DISTANCE][(int)HALF_TERRAIN_DISTANCE];
        height1 = heightmap[(int)HALF_TERRAIN_DISTANCE + 1][(int)HALF_TERRAIN_DISTANCE + 1];

        Vec2 incell = { scn->pos.x - floorf(scn->pos.x), scn->pos.z - floorf(scn->pos.z) };

        /* who needs barycentric coordinates, am i right? */
        weight0 = 1 / sqrtf(powf(incell.x, 2) + powf(incell.y, 2));
        weight1 = 1 / sqrtf(powf(1 - incell.x, 2) + powf(1 - incell.y, 2));

        /* find which triangle we're directly under */
        /* for this manhattan distance is sufficient */
        if (incell.x + (1 - incell.y) < (1 - incell.x) + incell.y) {
            height2 = heightmap[(int)HALF_TERRAIN_DISTANCE][(int)HALF_TERRAIN_DISTANCE + 1];
            weight2 = 1 / sqrtf(powf(incell.x, 2) + powf(1 - incell.y, 2));
        } else {
            height2 = heightmap[(int)HALF_TERRAIN_DISTANCE + 1][(int)HALF_TERRAIN_DISTANCE];
            weight2 = 1 / sqrtf(powf(1 - incell.x, 2) + powf(incell.y, 2));
        }

        float height = (height0 * weight0 + height1 * weight1 + height2 * weight2) / (weight0 + weight1 + weight2);

        if (target.y > height + PLAYER_HEIGHT)
            target.y = target.y - 0.4f;

        if (target.y < height + PLAYER_HEIGHT)
            target.y = height + PLAYER_HEIGHT;

    }

    /* movement */
    {
        Vec3 direction = {0, 0, 0};

        if (input_action_pressed("player_left"))
           direction = m_vec_sub(direction, m_vec_scale(right, speed));

        if (input_action_pressed("player_right"))
           direction = m_vec_add(direction, m_vec_scale(right, speed));

        if (input_action_pressed("player_forward"))
            direction = m_vec_add(direction, m_vec_scale(dir_and_up.direction, speed));

        if (input_action_pressed("player_backward"))
            direction = m_vec_sub(direction, m_vec_scale(dir_and_up.direction, speed));

        target = m_vec_add(target, direction);
    }

    /* interpolate */
    scn->pos.x = (target.x - scn->pos.x) * (0.13f / 0.9f) + scn->pos.x;
    scn->pos.y = (target.y - scn->pos.y) * (0.13f / 0.9f) + scn->pos.y;
    scn->pos.z = (target.z - scn->pos.z) * (0.13f / 0.9f) + scn->pos.z;
}


static void generate_terrain(SceneIngame *scn) {
    for (int ly = 0; ly < TERRAIN_DISTANCE; ly++) {
        for (int lx = 0; lx < TERRAIN_DISTANCE; lx++) {
            float x = floorf(scn->pos.x - HALF_TERRAIN_DISTANCE + (float)lx);
            float y = floorf(scn->pos.z - HALF_TERRAIN_DISTANCE + (float)ly);

            float height = stb_perlin_noise3((float)x * TERRAIN_FREQUENCY, (float)y * TERRAIN_FREQUENCY, 0, 0, 0, 0) * 3 - 1;

            heightmap[lx][ly] = height;
        }
    }
}


static void draw_terrain(SceneIngame *scn) {
    for (int ly = TERRAIN_DISTANCE - 1; ly > 0; ly--) {
        for (int lx = 0; lx < TERRAIN_DISTANCE - 1; lx++) {
            int32_t x = (int32_t)(floorf(scn->pos.x - HALF_TERRAIN_DISTANCE + (float)lx));
            int32_t y = (int32_t)(floorf(scn->pos.z - HALF_TERRAIN_DISTANCE + (float)ly));

            float d0 = heightmap[lx][ly];
            float d1 = heightmap[lx + 1][ly];
            float d2 = heightmap[lx + 1][ly - 1];
            float d3 = heightmap[lx][ly - 1];

            draw_triangle("/assets/grass.png",
                            (Vec3){ (float)x,     d0, (float)y },
                            (Vec3){ (float)x + 1, d1, (float)y },
                            (Vec3){ (float)x,     d3, (float)y - 1 },
                            (Vec2){ 128, 128 },
                            (Vec2){ 128, 0 },
                            (Vec2){ 0, 128 });

            draw_triangle("/assets/grass.png",
                            (Vec3){ (float)x + 1, d1, (float)y },
                            (Vec3){ (float)x + 1, d2, (float)y - 1 },
                            (Vec3){ (float)x,     d3, (float)y - 1 },
                            (Vec2){ 128, 0 },
                            (Vec2){ 0, 0 },
                            (Vec2){ 0, 128 });

            draw_billboard("/assets/grasses/10.png", (Vec3){ (float)x, d1 + 0.1f, (float)y }, (Vec2){0.3f, 0.3f}, (Color){255, 255, 255, 255}, true);
        }
    }
}


static void ingame_tick(State *state) {
    SceneIngame *scn = (SceneIngame *)state->scene;

    input_action("player_left", CONTROL_A);
    input_action("player_right", CONTROL_D);
    input_action("player_forward", CONTROL_W);
    input_action("player_backward", CONTROL_S);
    input_action("player_jump", CONTROL_SPACE);
    input_action("player_run", CONTROL_LSHIFT);
    input_action("mouse_capture_toggle", CONTROL_ESCAPE);
    input_action("toggle_camera_mode", CONTROL_C);

    if (scn->mouse_captured) {
        const float sensitivity = 0.4f * (float)DEG2RAD; /* TODO: put this in a better place */
        scn->yaw += (float)ctx.mouse_movement.x * sensitivity;
        scn->pitch -= (float)ctx.mouse_movement.y * sensitivity;
        scn->pitch = clampf(scn->pitch, (float)-M_PI * 0.49f, (float)M_PI * 0.49f);
    }

    if (input_action_just_pressed("toggle_camera_mode"))
        scn->flying_camera = !scn->flying_camera;

    if (scn->flying_camera) {
        process_fly_mode(state);
    } else {
        process_ground_mode(state);
    }

    /* toggle mouse capture with end key */
    if (input_action_just_pressed("mouse_capture_toggle"))
        scn->mouse_captured = !scn->mouse_captured;

    input_mouse_captured(scn->mouse_captured);

    generate_terrain(scn);
    draw_terrain(scn);

    // draw_skybox("/assets/miramar/miramar_*.tga");
    draw_fog(0.9f, 1.0f, 0.05f, (Color){ 140, 147, 160, 255 });
}


static void ingame_end(State *state) {
    free(state->scene);
}


Scene *ingame_scene(State *state) {
    (void)state;

    SceneIngame *new_scene = ccalloc(1, sizeof *new_scene);
    new_scene->base.tick = ingame_tick;
    new_scene->base.end = ingame_end;

    new_scene->mouse_captured = true;

    m_audio(m_set(path, "music/mod65.xm"),
            m_opt(channel, "soundtrack"),
            m_opt(repeat, true));

    new_scene->pos = (Vec3){ 0.1f, 0.0, 0.1f };

    return (Scene *)new_scene;
}