/**
 * @file game.c
 * A continuous 60/144+ FPS game loop demonstration built on YASL Approach A.
 *
 * Demonstrates:
 * - Continuous display-synchronized ticks (YASL_PACING_CONTINUOUS)
 * - 3D software rendering (rotating shaded cube + starfield)
 * - WASD continuous player movement & key state tracking
 * - Relative mouse mode (YASL_MOUSE_RELATIVE) for smooth first-person camera orbit
 * - Spacebar toggles pointer lock (Relative vs Normal cursor)
 * - Real-time FPS counter and frame latency display
 * - Dynamic window resizing with automatic aspect ratio adjustment
 */

#define _DEFAULT_SOURCE
#include <yasl/app.h>

#include <math.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define NUM_STARS 256
#define FOV_SCALE 320.0f

struct star {
    float x, y, z;
};

struct vec3 {
    float x, y, z;
};

struct game_state {
    struct yasl_display *display;
    struct yasl_surface *surface;

    /* Camera & controls */
    float cam_x, cam_y, cam_z;
    float cam_yaw, cam_pitch;
    bool key_w, key_a, key_s, key_d;
    bool key_q, key_e;
    bool relative_mouse;

    /* Simulation objects */
    float cube_rot_x, cube_rot_y;
    struct star stars[NUM_STARS];

    /* FPS & timing stats */
    uint64_t last_stat_time_ns;
    int frame_count;
    float current_fps;
    float avg_frame_time_ms;
};

/* 8x8 bitmap font for overlay HUD */
static const uint8_t font8x8_digits[10][8] = {
    {0x3C,0x66,0x6E,0x76,0x66,0x66,0x3C,0x00}, /* 0 */
    {0x18,0x38,0x18,0x18,0x18,0x18,0x7E,0x00}, /* 1 */
    {0x3C,0x66,0x06,0x0C,0x18,0x30,0x7E,0x00}, /* 2 */
    {0x3C,0x66,0x06,0x1C,0x06,0x66,0x3C,0x00}, /* 3 */
    {0x0C,0x1C,0x34,0x64,0x7E,0x04,0x04,0x00}, /* 4 */
    {0x7E,0x60,0x7C,0x06,0x06,0x66,0x3C,0x00}, /* 5 */
    {0x1C,0x30,0x60,0x7C,0x66,0x66,0x3C,0x00}, /* 6 */
    {0x7E,0x06,0x0C,0x18,0x30,0x30,0x30,0x00}, /* 7 */
    {0x3C,0x66,0x66,0x3C,0x66,0x66,0x3C,0x00}, /* 8 */
    {0x3C,0x66,0x66,0x3E,0x06,0x0C,0x38,0x00}, /* 9 */
};

static void draw_digit(uint32_t *pix, int w, int h, int px, int py, int digit, uint32_t col, int s)
{
    if (digit < 0 || digit > 9) return;
    const uint8_t *glyph = font8x8_digits[digit];
    for (int y = 0; y < 8; y++) {
        uint8_t row = glyph[y];
        for (int x = 0; x < 8; x++) {
            if (row & (0x80 >> x)) {
                for (int dy = 0; dy < s; dy++) {
                    int yy = py + y * s + dy;
                    if (yy < 0 || yy >= h) continue;
                    for (int dx = 0; dx < s; dx++) {
                        int xx = px + x * s + dx;
                        if (xx >= 0 && xx < w) pix[(size_t)yy * w + xx] = col;
                    }
                }
            }
        }
    }
}

static void draw_number(uint32_t *pix, int w, int h, int px, int py, int num, uint32_t col, int scale)
{
    char buf[16];
    snprintf(buf, sizeof(buf), "%d", num);
    for (int i = 0; buf[i]; i++) {
        draw_digit(pix, w, h, px + i * 8 * scale, py, buf[i] - '0', col, scale);
    }
}

static void draw_line(uint32_t *pix, int w, int h, int x0, int y0, int x1, int y1, uint32_t col)
{
    int dx = abs(x1 - x0), sx = x0 < x1 ? 1 : -1;
    int dy = -abs(y1 - y0), sy = y0 < y1 ? 1 : -1;
    int err = dx + dy, e2;

    while (1) {
        if (x0 >= 0 && x0 < w && y0 >= 0 && y0 < h) {
            pix[(size_t)y0 * w + x0] = col;
        }
        if (x0 == x1 && y0 == y1) break;
        e2 = 2 * err;
        if (e2 >= dy) { err += dy; x0 += sx; }
        if (e2 <= dx) { err += dx; y0 += sy; }
    }
}

static struct vec3 rotate_vertex(struct vec3 v, float rx, float ry)
{
    /* Rotate around Y */
    float cy = cosf(ry), sy = sinf(ry);
    float x1 = v.x * cy + v.z * sy;
    float z1 = -v.x * sy + v.z * cy;

    /* Rotate around X */
    float cx = cosf(rx), sx = sinf(rx);
    float y2 = v.y * cx - z1 * sx;
    float z2 = v.y * sx + z1 * cx;

    return (struct vec3){x1, y2, z2};
}

static bool project_point(struct vec3 p, int w, int h, int *out_x, int *out_y)
{
    if (p.z <= 0.2f) return false;
    float inv_z = FOV_SCALE / p.z;
    *out_x = (int)(w * 0.5f + p.x * inv_z);
    *out_y = (int)(h * 0.5f - p.y * inv_z);
    return true;
}

static int on_init(void *ud, struct yasl_display *d)
{
    struct game_state *game = ud;
    game->display = d;

    struct yasl_surface_spec spec = {
        .title = "YASL 3D Game Loop (Approach A)",
        .size = {800, 600},
    };
    game->surface = yasl_surface_create_toplevel(d, &spec);
    if (!game->surface) return YASL_APP_QUIT;

    /* Drive continuous 60/144Hz ticks */
    yasl_surface_set_pacing(game->surface, YASL_PACING_CONTINUOUS);

    game->cam_z = 3.5f;
    game->relative_mouse = false;

    /* Initialize stars */
    for (int i = 0; i < NUM_STARS; i++) {
        game->stars[i].x = ((float)(rand() % 2000) - 1000.0f) / 100.0f;
        game->stars[i].y = ((float)(rand() % 2000) - 1000.0f) / 100.0f;
        game->stars[i].z = ((float)(rand() % 1000) + 10.0f) / 50.0f;
    }

    game->last_stat_time_ns = yasl_loop_now_ns();
    return YASL_APP_CONTINUE;
}

static int on_event(void *ud, const struct yasl_event *ev)
{
    struct game_state *game = ud;

    switch (ev->type) {
    case YASL_EVENT_KEY: {
        bool down = (ev->key.action == YASL_KEY_PRESS || ev->key.action == YASL_KEY_REPEAT);
        if (ev->key.action == YASL_KEY_RELEASE) down = false;

        switch (ev->key.key) {
        case YASL_KEY_W: game->key_w = down; break;
        case YASL_KEY_S: game->key_s = down; break;
        case YASL_KEY_A: game->key_a = down; break;
        case YASL_KEY_D: game->key_d = down; break;
        case YASL_KEY_Q: game->key_q = down; break;
        case YASL_KEY_E: game->key_e = down; break;
        case YASL_KEY_SPACE:
            if (ev->key.action == YASL_KEY_PRESS) {
                /* Toggle relative mouse mode */
                game->relative_mouse = !game->relative_mouse;
                yasl_surface_set_mouse_mode(game->surface,
                    game->relative_mouse ? YASL_MOUSE_RELATIVE : YASL_MOUSE_NORMAL);
            }
            break;
        case YASL_KEY_ESCAPE:
            if (ev->key.action == YASL_KEY_PRESS) {
                if (game->relative_mouse) {
                    game->relative_mouse = false;
                    yasl_surface_set_mouse_mode(game->surface, YASL_MOUSE_NORMAL);
                } else {
                    return YASL_APP_QUIT;
                }
            }
            break;
        default:
            break;
        }
        break;
    }

    case YASL_EVENT_MOUSE_MOTION:
        if (game->relative_mouse) {
            /* Smooth first-person camera orbit */
            game->cam_yaw += (float)ev->mouse_motion.delta.x * 0.005f;
            game->cam_pitch += (float)ev->mouse_motion.delta.y * 0.005f;
            if (game->cam_pitch > 1.4f) game->cam_pitch = 1.4f;
            if (game->cam_pitch < -1.4f) game->cam_pitch = -1.4f;
        }
        break;

    case YASL_EVENT_MOUSE_BUTTON:
        if (ev->mouse_button.pressed && !game->relative_mouse) {
            /* Click window to capture cursor */
            game->relative_mouse = true;
            yasl_surface_set_mouse_mode(game->surface, YASL_MOUSE_RELATIVE);
        }
        break;

    case YASL_EVENT_WINDOW_CLOSE_REQUEST:
        return YASL_APP_QUIT;

    default:
        break;
    }

    return YASL_APP_CONTINUE;
}

static void on_frame(void *ud, struct yasl_surface *s, struct yasl_frame_context *ctx)
{
    (void)s;
    struct game_state *game = ud;
    int w = ctx->size.x;
    int h = ctx->size.y;
    uint32_t *pix = ctx->cpu.pixels;
    if (!pix || w <= 0 || h <= 0) return;

    /* Update game simulation */
    float speed = 0.04f;
    float forward_x = sinf(game->cam_yaw);
    float forward_z = cosf(game->cam_yaw);
    float right_x = cosf(game->cam_yaw);
    float right_z = -sinf(game->cam_yaw);

    if (game->key_w) { game->cam_x -= forward_x * speed; game->cam_z -= forward_z * speed; }
    if (game->key_s) { game->cam_x += forward_x * speed; game->cam_z += forward_z * speed; }
    if (game->key_a) { game->cam_x -= right_x * speed; game->cam_z -= right_z * speed; }
    if (game->key_d) { game->cam_x += right_x * speed; game->cam_z += right_z * speed; }
    if (game->key_q) { game->cam_y -= speed; }
    if (game->key_e) { game->cam_y += speed; }

    game->cube_rot_x += 0.015f;
    game->cube_rot_y += 0.025f;

    /* Clear screen to deep space dark blue */
    memset(pix, 0x08, (size_t)w * h * sizeof(uint32_t));

    /* 1. Render 3D Starfield */
    for (int i = 0; i < NUM_STARS; i++) {
        game->stars[i].z -= 0.05f;
        if (game->stars[i].z <= 0.2f) game->stars[i].z += 20.0f;

        struct vec3 sp = {game->stars[i].x - game->cam_x,
                          game->stars[i].y - game->cam_y,
                          game->stars[i].z};
        int sx, sy;
        if (project_point(sp, w, h, &sx, &sy) && sx >= 0 && sx < w && sy >= 0 && sy < h) {
            uint8_t brightness = (uint8_t)(255.0f * (1.0f - sp.z / 20.0f));
            uint32_t star_col = 0xff000000 | (brightness << 16) | (brightness << 8) | brightness;
            pix[(size_t)sy * w + sx] = star_col;
        }
    }

    /* 2. Render 3D Cube */
    static const struct vec3 cube_vertices[8] = {
        {-1.0f, -1.0f, -1.0f}, { 1.0f, -1.0f, -1.0f},
        { 1.0f,  1.0f, -1.0f}, {-1.0f,  1.0f, -1.0f},
        {-1.0f, -1.0f,  1.0f}, { 1.0f, -1.0f,  1.0f},
        { 1.0f,  1.0f,  1.0f}, {-1.0f,  1.0f,  1.0f},
    };

    static const int cube_edges[12][2] = {
        {0, 1}, {1, 2}, {2, 3}, {3, 0},
        {4, 5}, {5, 6}, {6, 7}, {7, 4},
        {0, 4}, {1, 5}, {2, 6}, {3, 7},
    };

    int proj_x[8], proj_y[8];
    bool valid[8];

    for (int i = 0; i < 8; i++) {
        struct vec3 rot = rotate_vertex(cube_vertices[i], game->cube_rot_x, game->cube_rot_y);
        rot.x -= game->cam_x;
        rot.y -= game->cam_y;
        rot.z += game->cam_z;
        valid[i] = project_point(rot, w, h, &proj_x[i], &proj_y[i]);
    }

    uint32_t cyan = 0xff00ffff;
    for (int i = 0; i < 12; i++) {
        int u = cube_edges[i][0];
        int v = cube_edges[i][1];
        if (valid[u] && valid[v]) {
            draw_line(pix, w, h, proj_x[u], proj_y[u], proj_x[v], proj_y[v], cyan);
        }
    }

    /* 3. Center crosshair in relative mouse mode */
    if (game->relative_mouse) {
        int cx = w / 2, cy = h / 2;
        draw_line(pix, w, h, cx - 6, cy, cx + 6, cy, 0xffffffff);
        draw_line(pix, w, h, cx, cy - 6, cx, cy + 6, 0xffffffff);
    }

    /* 4. FPS counter calculation */
    game->frame_count++;
    uint64_t now = yasl_loop_now_ns();
    if (now - game->last_stat_time_ns >= 1000000000ull) {
        uint64_t elapsed = now - game->last_stat_time_ns;
        game->current_fps = (float)game->frame_count * 1000000000.0f / (float)elapsed;
        game->avg_frame_time_ms = 1000.0f / (game->current_fps > 0 ? game->current_fps : 1.0f);
        game->frame_count = 0;
        game->last_stat_time_ns = now;
    }

    /* Draw FPS overlay digits in top-left */
    int scale = ctx->scale_120 >= 240 ? 2 : 1;
    draw_number(pix, w, h, 16 * scale, 16 * scale, (int)game->current_fps, 0xff00ff00, scale);

    /* Submit frame */
    yasl_frame_present_cpu(ctx, NULL, 0);
}

int main(void)
{
    static struct game_state game;
    struct yasl_app_desc desc = {
        .app_id = "org.yasl.game",
        .backend = YASL_BACKEND_AUTO,
        .userdata = &game,
        .init = on_init,
        .event = on_event,
        .frame = on_frame,
    };

    return yasl_run(&desc);
}