#include "kknd.h"

/* =========================================================================
 * projectiles.c - Bullets, missiles and particle effects.
 * ========================================================================= */

static RNG g_prng;
static int g_prng_init = 0;

void bullet_spawn(Game *g, float x, float y, int target_unit, int target_bld,
                  float dmg, Faction f, int kind) {
    if (g->bullet_count >= MAX_BULLETS) return;
    Bullet *b = &g->bullets[g->bullet_count++];
    b->x = x; b->y = y;
    b->target_unit = target_unit;
    b->target_bld = target_bld;
    b->damage = dmg;
    b->faction = f;
    b->kind = kind;
    b->speed = (kind == 3) ? 320 : (kind == 1 ? 420 : 520);
    b->life = 3.0f;
    if (target_unit >= 0) {
        Unit *t = unit_by_id(g, target_unit);
        if (t) { b->tx = t->x; b->ty = t->y; }
    } else if (target_bld >= 0) {
        Building *t = bld_by_id(g, target_bld);
        if (t) { b->tx = (float)(t->tx*TILE + t->w*TILE/2);
                 b->ty = (float)(t->ty*TILE + t->h*TILE/2); }
    }
}

void bullet_update(Game *g, float dt) {
    for (int i = g->bullet_count - 1; i >= 0; i--) {
        Bullet *b = &g->bullets[i];
        b->life -= dt;
        /* home onto target if still alive */
        if (b->target_unit >= 0) {
            Unit *t = unit_by_id(g, b->target_unit);
            if (t) { b->tx = t->x; b->ty = t->y; }
            else b->target_unit = -1;
        } else if (b->target_bld >= 0) {
            Building *t = bld_by_id(g, b->target_bld);
            if (t) { b->tx = (float)(t->tx*TILE+t->w*TILE/2);
                     b->ty = (float)(t->ty*TILE+t->h*TILE/2); }
            else b->target_bld = -1;
        }

        float dx = b->tx - b->x, dy = b->ty - b->y;
        float d = (float)sqrtf(dx*dx + dy*dy);
        float step = b->speed * dt;
        if (d <= step + 4 || b->life <= 0) {
            /* impact */
            if (b->target_unit >= 0) {
                Unit *t = unit_by_id(g, b->target_unit);
                if (t) unit_apply_damage(g, t, b->damage);
            } else if (b->target_bld >= 0) {
                Building *t = bld_by_id(g, b->target_bld);
                if (t) bld_apply_damage(g, t, b->damage);
            }
            /* denser impact: fire/laser core + smoke ring + debris */
            int hit_kind = (b->kind == 2) ? 2 : 1;
            particle_burst(g, b->tx, b->ty, 12, hit_kind, 255, 200, 80);
            particle_burst(g, b->tx, b->ty, 8, 0, 90, 80, 60);
            particle_burst(g, b->tx, b->ty, 5, 1, 255, 120, 35);
            if (b->kind == 1 || b->kind == 3)
                particle_burst(g, b->tx, b->ty, 6, 3, 255, 140, 40);
            /* swap-remove */
            g->bullets[i] = g->bullets[g->bullet_count - 1];
            g->bullet_count--;
            continue;
        }
        b->x += dx/d * step;
        b->y += dy/d * step;
        /* trail — denser muzzle streak for non-ballistic shells */
        if (b->kind != 0)
            particle_spawn(g, b->x, b->y, 2, 255, 180, 60);
        if (b->kind == 1 || b->kind == 3) {
            particle_spawn(g, b->x - dx / d * 3.0f, b->y - dy / d * 3.0f,
                           3, 255, 160, 50);
            particle_spawn(g, b->x - dx / d * 6.0f, b->y - dy / d * 6.0f,
                           1, 255, 140, 40);
        }
        if (b->kind == 2)
            particle_spawn(g, b->x, b->y, 2, 180, 120, 255);
    }
}

void particle_spawn(Game *g, float x, float y, int kind, uint8_t cr, uint8_t cg, uint8_t cb) {
    if (g->particle_count >= MAX_PARTICLES) return;
    if (!g_prng_init) { rng_seed(&g_prng, 0x1234ABCDULL); g_prng_init = 1; }
    Particle *p = &g->particles[g->particle_count++];
    p->x = x; p->y = y;
    float ang = rng_frange(&g_prng, 0, 6.283f);
    float sp = rng_frange(&g_prng, 10, 60);
    p->vx = (float)cosf(ang) * sp;
    p->vy = (float)sinf(ang) * sp;
    /* lingering columns: smoke / fire / spark|debris (KKND2 clash plate) */
    if (kind == 0)      p->life = p->max_life = 3.6f;
    else if (kind == 1) p->life = p->max_life = 2.6f;
    else                p->life = p->max_life = 1.4f;
    p->r = cr; p->g = cg; p->b = cb;
    p->kind = kind;
}

void particle_burst(Game *g, float x, float y, int n, int kind, uint8_t cr, uint8_t cg, uint8_t cb) {
    for (int i = 0; i < n; i++) particle_spawn(g, x, y, kind, cr, cg, cb);
}

void particle_update(Game *g, float dt) {
    for (int i = g->particle_count - 1; i >= 0; i--) {
        Particle *p = &g->particles[i];
        p->life -= dt;
        p->x += p->vx * dt;
        p->y += p->vy * dt;
        p->vx *= 0.92f; p->vy *= 0.92f;
        /* screen-y grows downward: subtract to rise (fire + smoke columns) */
        if (p->kind == 1) p->vy -= 42 * dt;
        if (p->kind == 0) p->vy -= 22 * dt;
        if (p->life <= 0) {
            g->particles[i] = g->particles[g->particle_count - 1];
            g->particle_count--;
        }
    }
}