// Simple FPS demo using FreeGLUT + legacy OpenGL (compat profile)
// - Move: WASD, Shift to sprint, Space to shoot, Esc to quit
// - Look: mouse
// - Targets: red cubes move toward you; shoot them before they reach you
// - Game over when a target reaches you; final score shown; press R to restart

#include <GL/freeglut_std.h>
#include <GL/gl.h>
#include <GL/glu.h>
#include <SDL2/SDL.h>
#include <SDL2/SDL_audio.h>
#include <SDL2/SDL_error.h>
#include <SDL2/SDL_stdinc.h>
#include <ctype.h>
#include <math.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif

// -------- Math helpers --------
typedef struct
{
    float x, y, z;
} vec3;

static inline vec3 v3(float x, float y, float z)
{
    vec3 v = {x, y, z};
    return v;
}
static inline vec3  v3_add(vec3 a, vec3 b) { return v3(a.x + b.x, a.y + b.y, a.z + b.z); }
static inline vec3  v3_sub(vec3 a, vec3 b) { return v3(a.x - b.x, a.y - b.y, a.z - b.z); }
static inline vec3  v3_scale(vec3 a, float s) { return v3(a.x * s, a.y * s, a.z * s); }
static inline float v3_dot(vec3 a, vec3 b) { return (a.x * b.x) + (a.y * b.y) + (a.z * b.z); }
static inline vec3  v3_cross(vec3 a, vec3 b)
{
    return v3((a.y * b.z) - (a.z * b.y), (a.z * b.x) - (a.x * b.z), (a.x * b.y) - (a.y * b.x));
}
static inline float v3_len(vec3 a) { return sqrtf(v3_dot(a, a)); }
static inline vec3  v3_norm(vec3 a)
{
    float l = v3_len(a);
    return l > 1e-6F ? v3_scale(a, 1.0F / l) : v3(0, 0, 0);
}

// -------- Global state --------
static int  g_win_w = 1280, g_win_h = 720;
static bool g_keys[256]      = {0};
static bool g_captured_mouse = true;
static int  g_last_mouse_x = -1, g_last_mouse_y = -1;
static bool g_ignore_next_passive = false; // avoid warp feedback loops

static vec3  g_cam_pos   = {0.0F, 1.6F, 5.0F};
static float g_yaw_deg   = -90.0F; // facing -Z initially
static float g_pitch_deg = 0.0F;

static float g_move_speed = 4.0F; // m/s
static float g_sprint_mul = 1.8F;
static float g_mouse_sens = 0.12F; // deg per pixel

typedef struct
{
    vec3  pos;
    float radius;
    float speed;
} Target;
static const int MAX_TARGETS = 128;
static Target    g_targets[128];
static int       g_target_count   = 0;
static float     g_spawn_timer    = 0.0F;
static float     g_spawn_interval = 1.2F; // seconds
static int       g_score          = 0;

typedef enum
{
    GAME_RUNNING = 0,
    GAME_OVER    = 1
} GameState;
static GameState g_state = GAME_RUNNING;

// Bullet visualization removed per request

// Timing
static int g_prev_ms = 0;

// -------- Utility --------
static float clampf(float v, float lo, float hi) { return v < lo ? lo : (v > hi ? hi : v); }
static float deg2rad(float d) { return d * (float)M_PI / 180.0F; }

static vec3 cam_front(void)
{
    float yaw   = deg2rad(g_yaw_deg);
    float pitch = deg2rad(g_pitch_deg);
    vec3  f     = {cosf(pitch) * cosf(yaw), sinf(pitch), cosf(pitch) * sinf(yaw)};
    return v3_norm(f);
}

static vec3 cam_right(void) { return v3_norm(v3_cross(cam_front(), v3(0, 1, 0))); }

// -------- Audio (SDL2) --------
static SDL_AudioDeviceID g_audio_dev = 0;
static SDL_AudioSpec     g_audio_have;
static bool              g_audio_ok = false;

static void audio_cleanup(void)
{
    if (g_audio_dev)
    {
        SDL_ClearQueuedAudio(g_audio_dev);
        SDL_CloseAudioDevice(g_audio_dev);
        g_audio_dev = 0;
    }
    if (g_audio_ok)
    {
        SDL_QuitSubSystem(SDL_INIT_AUDIO);
        g_audio_ok = false;
    }
}

static void audio_init(void)
{
    if (SDL_InitSubSystem(SDL_INIT_AUDIO) != 0)
    {
        fprintf(stderr, "SDL audio init failed: %s\n", SDL_GetError());
        return;
    }
    SDL_AudioSpec want;
    SDL_zero(want);
    want.freq     = 48000;
    want.format   = AUDIO_F32SYS;
    want.channels = 1;
    want.samples  = 1024;
    g_audio_dev   = SDL_OpenAudioDevice(NULL, 0, &want, &g_audio_have, 0);
    if (!g_audio_dev)
    {
        fprintf(stderr, "SDL_OpenAudioDevice failed: %s\n", SDL_GetError());
        SDL_QuitSubSystem(SDL_INIT_AUDIO);
        return;
    }
    SDL_PauseAudioDevice(g_audio_dev, 0);
    g_audio_ok = true;
    atexit(audio_cleanup);
}

static void audio_queue_samples(const float *data, int frames)
{
    if (!g_audio_ok)
    {
        return;
    }
    int bytes = frames * (int)sizeof(float);
    SDL_QueueAudio(g_audio_dev, data, bytes);
}

static void audio_play_tone(float freq, float duration, float vol)
{
    if (!g_audio_ok)
    {
        return;
    }
    int sr     = g_audio_have.freq ? g_audio_have.freq : 48000;
    int frames = (int)(duration * sr);
    if (frames <= 0)
    {
        return;
    }
    float *buf = (float *)malloc((size_t)frames * sizeof(float));
    if (!buf)
    {
        return;
    }
    float phase = 0.0F;
    float dp    = 2.0F * (float)M_PI * freq / (float)sr;
    for (int i = 0; i < frames; ++i)
    {
        float t = (float)i / (float)frames;
        // simple attack/decay envelope
        float env = t < 0.1F ? (t / 0.1F) : (1.0F - t);
        if (env < 0.0F)
        {
            env = 0.0F;
        }
        buf[i] = sinf(phase) * vol * env;
        phase += dp;
    }
    audio_queue_samples(buf, frames);
    free(buf);
}

static void audio_play_sweep(float f0, float f1, float duration, float vol)
{
    if (!g_audio_ok)
    {
        return;
    }
    int sr     = g_audio_have.freq ? g_audio_have.freq : 48000;
    int frames = (int)(duration * sr);
    if (frames <= 0)
    {
        return;
    }
    float *buf = (float *)malloc((size_t)frames * sizeof(float));
    if (!buf)
    {
        return;
    }
    float phase = 0.0F;
    for (int i = 0; i < frames; ++i)
    {
        float t   = (float)i / (float)frames; // 0..1
        float f   = f0 + ((f1 - f0) * t);
        float dp  = 2.0F * (float)M_PI * f / (float)sr;
        float env = 1.0F - t; // fade out
        buf[i]    = sinf(phase) * vol * env;
        phase += dp;
    }
    audio_queue_samples(buf, frames);
    free(buf);
}

static float frand(float a, float b) { return a + ((b - a) * (rand() / (float)RAND_MAX)); }

static void clear_targets(void) { g_target_count = 0; }

static void spawn_target(void)
{
    if (g_target_count >= MAX_TARGETS)
    {
        return;
    }
    float  radius_spawn = frand(22.0F, 34.0F);
    float  ang          = frand(0.0F, 2.0F * (float)M_PI);
    vec3   p            = v3(cosf(ang) * radius_spawn, 0.5F, sinf(ang) * radius_spawn);
    Target t;
    t.pos                       = p;
    t.radius                    = 0.6F;
    t.speed                     = frand(1.4F, 3.2F);
    g_targets[g_target_count++] = t;
}

static void reset_game(void)
{
    g_score          = 0;
    g_spawn_timer    = 0.0F;
    g_spawn_interval = 1.2F;
    clear_targets();
    // spawn a few to start
    for (int i = 0; i < 4; ++i)
    {
        spawn_target();
    }
    g_state = GAME_RUNNING;
    if (g_captured_mouse)
    {
        g_ignore_next_passive = true;
        glutWarpPointer(g_win_w / 2, g_win_h / 2);
    }
}

// Ray-sphere intersection: returns t >= 0 for first hit, or -1 if miss
static float ray_sphere(vec3 ro, vec3 rd, vec3 c, float r)
{
    vec3  oc    = v3_sub(ro, c);
    float b     = v3_dot(oc, rd);
    float cterm = v3_dot(oc, oc) - (r * r);
    float disc  = (b * b) - cterm;
    if (disc < 0.0F)
    {
        return -1.0F;
    }
    float t = -b - sqrtf(disc);
    return t >= 0.0F ? t : -1.0F;
}

static void shoot(void)
{
    if (g_state != GAME_RUNNING)
    {
        return;
    }
    vec3  dir    = cam_front();
    float best_t = 1e9F;
    int   best_i = -1;
    for (int i = 0; i < g_target_count; ++i)
    {
        float t = ray_sphere(g_cam_pos, dir, g_targets[i].pos, g_targets[i].radius);
        if (t >= 0.0F && t < best_t)
        {
            best_t = t;
            best_i = i;
        }
    }
    audio_play_tone(1600.0F, 0.05F, 0.25F); // shoot

    if (best_i >= 0)
    {
        // remove hit target (swap remove)
        g_targets[best_i] = g_targets[g_target_count - 1];
        g_target_count--;
        g_score++;
        audio_play_tone(600.0F, 0.08F, 0.35F); // hit
    }
}

// -------- Rendering --------
static void draw_grid(float half, float step)
{
    glColor3f(0.2F, 0.25F, 0.3F);
    glBegin(GL_LINES);
    for (float x = -half; x <= half + 1e-4F; x += step)
    {
        glVertex3f(x, 0.0F, -half);
        glVertex3f(x, 0.0F, half);
    }
    for (float z = -half; z <= half + 1e-4F; z += step)
    {
        glVertex3f(-half, 0.0F, z);
        glVertex3f(half, 0.0F, z);
    }
    glEnd();
}

static void draw_cube(void)
{
    // Simple colored cube (size 1)
    const float s = 0.5F;
    glBegin(GL_QUADS);
    // +X
    glColor3f(1, 0, 0);
    glVertex3f(s, -s, -s);
    glVertex3f(s, -s, s);
    glVertex3f(s, s, s);
    glVertex3f(s, s, -s);
    // -X
    glColor3f(0.8F, 0, 0);
    glVertex3f(-s, -s, -s);
    glVertex3f(-s, s, -s);
    glVertex3f(-s, s, s);
    glVertex3f(-s, -s, s);
    // +Y
    glColor3f(0.9F, 0.1F, 0.1F);
    glVertex3f(-s, s, -s);
    glVertex3f(s, s, -s);
    glVertex3f(s, s, s);
    glVertex3f(-s, s, s);
    // -Y
    glColor3f(0.6F, 0.05F, 0.05F);
    glVertex3f(-s, -s, -s);
    glVertex3f(-s, -s, s);
    glVertex3f(s, -s, s);
    glVertex3f(s, -s, -s);
    // +Z
    glColor3f(1, 0.2F, 0.2F);
    glVertex3f(-s, -s, s);
    glVertex3f(-s, s, s);
    glVertex3f(s, s, s);
    glVertex3f(s, -s, s);
    // -Z
    glColor3f(0.7F, 0.1F, 0.1F);
    glVertex3f(-s, -s, -s);
    glVertex3f(s, -s, -s);
    glVertex3f(s, s, -s);
    glVertex3f(-s, s, -s);
    glEnd();
}

static void draw_crosshair(void)
{
    glMatrixMode(GL_PROJECTION);
    glPushMatrix();
    glLoadIdentity();
    gluOrtho2D(0, g_win_w, g_win_h, 0);
    glMatrixMode(GL_MODELVIEW);
    glPushMatrix();
    glLoadIdentity();

    glDisable(GL_DEPTH_TEST);
    glColor3f(0.95F, 0.95F, 0.95F);
    int cx = g_win_w / 2;
    int cy = g_win_h / 2;
    int s  = 8;
    glBegin(GL_LINES);
    glVertex2i(cx - s, cy);
    glVertex2i(cx + s, cy);
    glVertex2i(cx, cy - s);
    glVertex2i(cx, cy + s);
    glEnd();
    glEnable(GL_DEPTH_TEST);

    glMatrixMode(GL_MODELVIEW);
    glPopMatrix();
    glMatrixMode(GL_PROJECTION);
    glPopMatrix();
}

static void display(void)
{
    glClearColor(0.05F, 0.06F, 0.08F, 1.0F);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    vec3 front = cam_front();
    vec3 at    = v3_add(g_cam_pos, front);
    gluLookAt(g_cam_pos.x, g_cam_pos.y, g_cam_pos.z, at.x, at.y, at.z, 0, 1, 0);

    // Ground grid
    draw_grid(40.0F, 1.0F);

    // Target cubes
    for (int i = 0; i < g_target_count; ++i)
    {
        glPushMatrix();
        glTranslatef(g_targets[i].pos.x, g_targets[i].pos.y, g_targets[i].pos.z);
        draw_cube();
        glPopMatrix();
    }

    // Bullet line removed

    // Crosshair overlay (only during gameplay)
    if (g_state == GAME_RUNNING)
    {
        draw_crosshair();
    }

    // Game over overlay text
    if (g_state == GAME_OVER)
    {
        // Switch to 2D for text
        glMatrixMode(GL_PROJECTION);
        glPushMatrix();
        glLoadIdentity();
        gluOrtho2D(0, g_win_w, g_win_h, 0);
        glMatrixMode(GL_MODELVIEW);
        glPushMatrix();
        glLoadIdentity();
        glDisable(GL_DEPTH_TEST);

        const char *line1 = "GAME OVER";
        char        line2[64];
        snprintf(line2, sizeof(line2), "Score: %d", g_score);
        const char *line3 = "Press R to restart or Esc to quit";

        void *font = GLUT_BITMAP_HELVETICA_18;
        int   cx   = g_win_w / 2;
        int   cy   = g_win_h / 2;
        glColor3f(1, 1, 1);
        // naive center: estimate width by char count * 9 px
        int w1 = (int)(9 * strlen(line1));
        int w2 = (int)(9 * strlen(line2));
        int w3 = (int)(9 * strlen(line3));

        glRasterPos2i(cx - (w1 / 2), cy - 30);
        for (const char *p = line1; *p; ++p)
        {
            glutBitmapCharacter(font, *p);
        }
        glRasterPos2i(cx - (w2 / 2), cy - 8);
        for (const char *p = line2; *p; ++p)
        {
            glutBitmapCharacter(font, *p);
        }
        glRasterPos2i(cx - (w3 / 2), cy + 18);
        for (const char *p = line3; *p; ++p)
        {
            glutBitmapCharacter(font, *p);
        }

        glEnable(GL_DEPTH_TEST);
        glMatrixMode(GL_MODELVIEW);
        glPopMatrix();
        glMatrixMode(GL_PROJECTION);
        glPopMatrix();
    }

    glutSwapBuffers();
}

// -------- Update/Input --------
static void update(float dt)
{
    if (g_state == GAME_RUNNING)
    {
        float speed =
            g_move_speed * ((g_keys['\t'] || g_keys['q']) ? g_sprint_mul : 1.0F); // Tab/q to sprint
        vec3 f = cam_front();
        f.y    = 0.0F;
        f      = v3_norm(f);
        vec3 r = cam_right();
        r.y    = 0.0F;
        r      = v3_norm(r);
        // Accumulate movement and apply once to avoid drift artifacts
        vec3 mv = v3(0, 0, 0);
        if (g_keys['w'])
        {
            mv = v3_add(mv, f);
        }
        if (g_keys['s'])
        {
            mv = v3_sub(mv, f);
        }
        if (g_keys['a'])
        {
            mv = v3_sub(mv, r);
        }
        if (g_keys['d'])
        {
            mv = v3_add(mv, r);
        }
        if (v3_len(mv) > 0.0F)
        {
            mv        = v3_norm(mv);
            g_cam_pos = v3_add(g_cam_pos, v3_scale(mv, speed * dt));
        }

        // Keep feet on ground
        g_cam_pos.y = 1.6F;

        // Move targets toward player and check collision
        for (int i = 0; i < g_target_count; ++i)
        {
            vec3 to_player     = v3_sub(g_cam_pos, g_targets[i].pos);
            to_player.y        = 0.0F;
            vec3 dir           = v3_norm(to_player);
            g_targets[i].pos   = v3_add(g_targets[i].pos, v3_scale(dir, g_targets[i].speed * dt));
            g_targets[i].pos.y = 0.5F;

            float dist2 = (to_player.x * to_player.x) + (to_player.z * to_player.z);
            float reach = (0.6F + g_targets[i].radius);
            if (dist2 <= reach * reach)
            {
                g_state = GAME_OVER;
                glutSetCursor(GLUT_CURSOR_LEFT_ARROW);
                audio_play_sweep(400.0F, 120.0F, 0.5F, 0.5F); // game over
                break;
            }
        }

        // Spawn new targets over time (slightly accelerate spawn rate)
        g_spawn_timer += dt;
        if (g_spawn_timer >= g_spawn_interval)
        {
            g_spawn_timer = 0.0F;
            spawn_target();
            g_spawn_interval = fmaxf(0.4F, g_spawn_interval * 0.98F);
        }
    }

    // No bullet tracer timer
}

static void idle(void)
{
    int now = glutGet(GLUT_ELAPSED_TIME);
    if (g_prev_ms == 0)
    {
        g_prev_ms = now;
    }
    float dt  = (now - g_prev_ms) / 1000.0F;
    g_prev_ms = now;

    update(dt);
    glutPostRedisplay();
}

static void reshape(int w, int h)
{
    g_win_w = w > 1 ? w : 1;
    g_win_h = h > 1 ? h : 1;
    glViewport(0, 0, g_win_w, g_win_h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(75.0, (double)g_win_w / (double)g_win_h, 0.05, 500.0);
    glMatrixMode(GL_MODELVIEW);

    if (g_captured_mouse && g_state == GAME_RUNNING)
    {
        g_ignore_next_passive = true;
        glutWarpPointer(g_win_w / 2, g_win_h / 2);
    }
}

static void keyboard_down(unsigned char key, int x, int y)
{
    (void)x;
    (void)y;
    unsigned char k = (unsigned char)tolower(key);
    g_keys[k]       = true;
    if (key == 27)
    { // Esc
        exit(0);
    }
    else if (key == ' ')
    {
        shoot();
    }
    else if (key == 'm' || key == 'M')
    {
        g_captured_mouse = !g_captured_mouse;
        glutSetCursor(g_captured_mouse ? GLUT_CURSOR_NONE : GLUT_CURSOR_LEFT_ARROW);
        if (g_captured_mouse && g_state == GAME_RUNNING)
        {
            g_ignore_next_passive = true;
            glutWarpPointer(g_win_w / 2, g_win_h / 2);
        }
    }
    else if (key == 'r' || key == 'R')
    {
        if (g_state == GAME_OVER)
        {
            glutSetCursor(g_captured_mouse ? GLUT_CURSOR_NONE : GLUT_CURSOR_LEFT_ARROW);
            reset_game();
        }
    }
}

static void keyboard_up(unsigned char key, int x, int y)
{
    (void)x;
    (void)y;
    unsigned char k = (unsigned char)tolower(key);
    g_keys[k]       = false;
}

static void mouse_button(int button, int state, int x, int y)
{
    (void)x;
    (void)y;
    if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
    {
        shoot();
    }
}

static void passive_motion(int x, int y)
{
    if (!g_captured_mouse || g_state != GAME_RUNNING)
    {
        return;
    }

    if (g_ignore_next_passive)
    { // ignore event caused by warp
        g_ignore_next_passive = false;
        return;
    }

    if (g_last_mouse_x < 0)
    {
        g_last_mouse_x = x;
        g_last_mouse_y = y;
    }
    int dx = x - (g_win_w / 2);
    int dy = y - (g_win_h / 2);

    g_yaw_deg += dx * g_mouse_sens;
    g_pitch_deg -= dy * g_mouse_sens;
    g_pitch_deg = clampf(g_pitch_deg, -89.0F, 89.0F);

    g_ignore_next_passive = true;
    glutWarpPointer(g_win_w / 2, g_win_h / 2);
}

// -------- Init --------
static void init_gl(void)
{
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_CULL_FACE);
    glCullFace(GL_BACK);
    glLineWidth(1.0F);
}

static void on_entry(int state)
{
    if (state != GLUT_ENTERED)
    {
        for (int i = 0; i < 256; ++i)
        {
            g_keys[i] = false;
        }
    }
}

int main(int argc, char **argv)
{
    (void)argv;
    srand((unsigned)time(NULL));

    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
    glutInitWindowSize(g_win_w, g_win_h);
    glutCreateWindow("FPS Demo");

    init_gl();
    audio_init();

    glutDisplayFunc(display);
    glutIdleFunc(idle);
    glutReshapeFunc(reshape);
    glutKeyboardFunc(keyboard_down);
    glutKeyboardUpFunc(keyboard_up);
    // Clear keys on focus leave to avoid stuck inputs
    glutEntryFunc(on_entry);
    glutPassiveMotionFunc(passive_motion);
    glutMouseFunc(mouse_button);

    // Start with mouse captured
    glutSetCursor(GLUT_CURSOR_NONE);
    g_ignore_next_passive = true;
    glutWarpPointer(g_win_w / 2, g_win_h / 2);

    reset_game();

    glutMainLoop();
    return 0;
}