#include "pxl8_world.h"

#include <string.h>

#include "pxl8_hal.h"

#ifdef PXL8_ASYNC_THREADS
#include <stdatomic.h>
#include "pxl8_queue.h"
#endif

#include "pxl8_bsp_render.h"
#include "pxl8_io.h"
#include "pxl8_gfx3d.h"
#include "pxl8_log.h"
#include "pxl8_mem.h"
#include "pxl8_sim.h"

#define PXL8_WORLD_ENTITY_CAPACITY 256

struct pxl8_world {
    pxl8_world_chunk* active_chunk;
    pxl8_world_chunk_cache* chunk_cache;
    pxl8_entity_pool* entities;
    pxl8_bsp_render_state* bsp_render_state;

    pxl8_sim_entity local_player;
    u64 client_tick;

    pxl8_vec2 pointer_motion;
    pxl8_sim_config sim_config;

#ifdef PXL8_ASYNC_THREADS
    pxl8_sim_entity render_state[2];
    atomic_uint active_buffer;
    pxl8_thread* sim_thread;
    atomic_bool sim_running;
    atomic_bool sim_paused;
    pxl8_net* net;
    pxl8_queue input_queue;
    f32 sim_accumulator;
#endif
};

pxl8_world* pxl8_world_create(void) {
    pxl8_world* world = pxl8_calloc(1, sizeof(pxl8_world));
    if (!world) return NULL;

    world->chunk_cache = pxl8_world_chunk_cache_create();
    world->entities = pxl8_entity_pool_create(PXL8_WORLD_ENTITY_CAPACITY);
    world->sim_config = (pxl8_sim_config){
        .move_speed    = 180.0f,
        .ground_accel  = 10.0f,
        .air_accel     = 1.0f,
        .stop_speed    = 100.0f,
        .friction      = 6.0f,
        .gravity       = 800.0f,
        .jump_velocity = 200.0f,
        .player_radius = 16.0f,
        .player_height = 72.0f,
        .max_pitch     = 1.5f,
    };

    if (!world->chunk_cache || !world->entities) {
        pxl8_world_destroy(world);
        return NULL;
    }

    return world;
}

void pxl8_world_destroy(pxl8_world* world) {
    if (!world) return;

    pxl8_world_chunk_cache_destroy(world->chunk_cache);
    pxl8_entity_pool_destroy(world->entities);
    pxl8_bsp_render_state_destroy(world->bsp_render_state);
    pxl8_free(world);
}

pxl8_world_chunk_cache* pxl8_world_get_chunk_cache(pxl8_world* world) {
    if (!world) return NULL;
    return world->chunk_cache;
}

pxl8_world_chunk* pxl8_world_active_chunk(pxl8_world* world) {
    if (!world) return NULL;
    return world->active_chunk;
}

void pxl8_world_set_active_chunk(pxl8_world* world, pxl8_world_chunk* chunk) {
    if (!world) return;
    world->active_chunk = chunk;
}

pxl8_entity_pool* pxl8_world_entities(pxl8_world* world) {
    if (!world) return NULL;
    return world->entities;
}

pxl8_entity pxl8_world_spawn(pxl8_world* world) {
    if (!world || !world->entities) return PXL8_ENTITY_INVALID;
    return pxl8_entity_spawn(world->entities);
}

pxl8_sim_world pxl8_world_sim_world(const pxl8_world* world, pxl8_vec3 pos) {
    (void)pos;
    pxl8_sim_world sim = {0};
    if (world->active_chunk && world->active_chunk->bsp) {
        sim.bsp = world->active_chunk->bsp;
    }
    return sim;
}

static void entity_to_userdata(const pxl8_sim_entity* ent, u8* userdata) {
    u8* p = userdata;
    memcpy(p, &ent->pos.x, 4); p += 4;
    memcpy(p, &ent->pos.y, 4); p += 4;
    memcpy(p, &ent->pos.z, 4); p += 4;
    memcpy(p, &ent->yaw, 4); p += 4;
    memcpy(p, &ent->pitch, 4); p += 4;
    memcpy(p, &ent->vel.x, 4); p += 4;
    memcpy(p, &ent->vel.y, 4); p += 4;
    memcpy(p, &ent->vel.z, 4); p += 4;
    memcpy(p, &ent->flags, 4); p += 4;
    memcpy(p, &ent->kind, 2);
}

static void userdata_to_entity(const u8* userdata, pxl8_sim_entity* ent) {
    const u8* p = userdata;
    memcpy(&ent->pos.x, p, 4); p += 4;
    memcpy(&ent->pos.y, p, 4); p += 4;
    memcpy(&ent->pos.z, p, 4); p += 4;
    memcpy(&ent->yaw, p, 4); p += 4;
    memcpy(&ent->pitch, p, 4); p += 4;
    memcpy(&ent->vel.x, p, 4); p += 4;
    memcpy(&ent->vel.y, p, 4); p += 4;
    memcpy(&ent->vel.z, p, 4); p += 4;
    memcpy(&ent->flags, p, 4); p += 4;
    memcpy(&ent->kind, p, 2);
}

bool pxl8_world_point_solid(const pxl8_world* world, f32 x, f32 y, f32 z) {
    if (!world) return false;

    if (world->active_chunk && world->active_chunk->bsp) {
        return pxl8_bsp_point_solid(world->active_chunk->bsp, (pxl8_vec3){x, y, z});
    }

    return false;
}

pxl8_ray pxl8_world_ray(const pxl8_world* world, pxl8_vec3 from, pxl8_vec3 to) {
    pxl8_ray result = {0};

    if (!world) return result;

    pxl8_vec3 dir = pxl8_vec3_sub(to, from);
    f32 length = pxl8_vec3_length(dir);
    if (length < 0.001f) return result;

    f32 step_size = 1.0f;
    f32 traveled = 0.0f;

    while (traveled < length) {
        f32 t = traveled / length;
        pxl8_vec3 pos = {
            from.x + dir.x * t,
            from.y + dir.y * t,
            from.z + dir.z * t
        };

        if (pxl8_world_point_solid(world, pos.x, pos.y, pos.z)) {
            result.hit = true;
            result.fraction = t;
            result.point = pos;

            f32 eps = 0.1f;
            bool sx_neg = pxl8_world_point_solid(world, pos.x - eps, pos.y, pos.z);
            bool sx_pos = pxl8_world_point_solid(world, pos.x + eps, pos.y, pos.z);
            bool sy_neg = pxl8_world_point_solid(world, pos.x, pos.y - eps, pos.z);
            bool sy_pos = pxl8_world_point_solid(world, pos.x, pos.y + eps, pos.z);
            bool sz_neg = pxl8_world_point_solid(world, pos.x, pos.y, pos.z - eps);
            bool sz_pos = pxl8_world_point_solid(world, pos.x, pos.y, pos.z + eps);

            result.normal = (pxl8_vec3){
                (sx_neg && !sx_pos) ? 1.0f : (!sx_neg && sx_pos) ? -1.0f : 0.0f,
                (sy_neg && !sy_pos) ? 1.0f : (!sy_neg && sy_pos) ? -1.0f : 0.0f,
                (sz_neg && !sz_pos) ? 1.0f : (!sz_neg && sz_pos) ? -1.0f : 0.0f
            };

            f32 nl = pxl8_vec3_length(result.normal);
            if (nl > 0.001f) {
                result.normal = pxl8_vec3_scale(result.normal, 1.0f / nl);
            } else {
                result.normal = (pxl8_vec3){0, 1, 0};
            }

            return result;
        }

        traveled += step_size;
    }

    return result;
}

pxl8_ray pxl8_world_sweep(const pxl8_world* world, pxl8_vec3 from, pxl8_vec3 to, f32 radius) {
    pxl8_ray result = {0};

    if (!world) return result;

    f32 diag = radius * 0.707f;

    bool dest_blocked = pxl8_world_point_solid(world, to.x, to.y, to.z) ||
                        pxl8_world_point_solid(world, to.x + radius, to.y, to.z) ||
                        pxl8_world_point_solid(world, to.x - radius, to.y, to.z) ||
                        pxl8_world_point_solid(world, to.x, to.y, to.z + radius) ||
                        pxl8_world_point_solid(world, to.x, to.y, to.z - radius) ||
                        pxl8_world_point_solid(world, to.x + diag, to.y, to.z + diag) ||
                        pxl8_world_point_solid(world, to.x + diag, to.y, to.z - diag) ||
                        pxl8_world_point_solid(world, to.x - diag, to.y, to.z + diag) ||
                        pxl8_world_point_solid(world, to.x - diag, to.y, to.z - diag);

    if (dest_blocked) {
        result.hit = true;
        result.fraction = 0;
        result.point = from;
        pxl8_vec3 dir = pxl8_vec3_sub(to, from);
        f32 length = pxl8_vec3_length(dir);
        if (length > 0.001f) {
            result.normal = pxl8_vec3_scale(dir, -1.0f / length);
        } else {
            result.normal = (pxl8_vec3){0, 1, 0};
        }
    }

    return result;
}

void pxl8_world_update(pxl8_world* world, f32 dt) {
    (void)dt;
    if (!world) return;
    pxl8_world_chunk_cache_tick(world->chunk_cache);
}

void pxl8_world_render(pxl8_world* world, pxl8_gfx* gfx, pxl8_vec3 camera_pos) {
    if (!world || !gfx) return;

    if (world->active_chunk && world->active_chunk->bsp) {
        pxl8_3d_set_bsp(gfx, world->active_chunk->bsp);
        pxl8_bsp_render(gfx, world->active_chunk->bsp,
                       world->bsp_render_state, camera_pos);
    } else {
        pxl8_3d_set_bsp(gfx, NULL);
    }
}

void pxl8_world_sync(pxl8_world* world, pxl8_net* net) {
    if (!world || !net) return;

    u32 chunk_id = pxl8_net_chunk_id(net);

    if (chunk_id != 0) {
        pxl8_world_chunk* chunk = pxl8_world_chunk_cache_get_bsp(world->chunk_cache, chunk_id);
        if (chunk && chunk->bsp) {
            if (world->active_chunk != chunk) {
                world->active_chunk = chunk;
                pxl8_debug("[CLIENT] Synced BSP chunk id=%u as active (verts=%u faces=%u)",
                           chunk_id, chunk->bsp->num_vertices, chunk->bsp->num_faces);

                if (world->bsp_render_state) {
                    pxl8_bsp_render_state_destroy(world->bsp_render_state);
                    world->bsp_render_state = NULL;
                }
                world->bsp_render_state = pxl8_bsp_render_state_create(chunk->bsp->num_faces);
            }
        }
    } else if (world->active_chunk != NULL) {
        world->active_chunk = NULL;
        if (world->bsp_render_state) {
            pxl8_bsp_render_state_destroy(world->bsp_render_state);
            world->bsp_render_state = NULL;
        }
    }
}

static void ensure_bsp_render_state(pxl8_world* world) {
    if (!world || world->bsp_render_state) return;
    if (!world->active_chunk) return;
    if (!world->active_chunk->bsp) return;

    world->bsp_render_state = pxl8_bsp_render_state_create(world->active_chunk->bsp->num_faces);
}

void pxl8_world_set_bsp_material(pxl8_world* world, u16 material_id, const pxl8_gfx_material* material) {
    if (!world || !material) return;

    ensure_bsp_render_state(world);
    if (!world->bsp_render_state) return;

    pxl8_bsp_set_material(world->bsp_render_state, material_id, material);
}

void pxl8_world_set_sim_config(pxl8_world* world, const pxl8_sim_config* config) {
    if (!world || !config) return;
    world->sim_config = *config;
}

void pxl8_world_init_local_player(pxl8_world* world, f32 x, f32 y, f32 z) {
    if (!world) return;
    world->local_player.pos = (pxl8_vec3){x, y, z};
    world->local_player.vel = (pxl8_vec3){0, 0, 0};
    world->local_player.yaw = 0;
    world->local_player.pitch = 0;
    world->local_player.flags = PXL8_SIM_FLAG_ALIVE | PXL8_SIM_FLAG_PLAYER | PXL8_SIM_FLAG_GROUNDED;
    world->local_player.kind = 0;
    world->client_tick = 0;
    world->pointer_motion = (pxl8_vec2){0};

#ifdef PXL8_ASYNC_THREADS
    world->render_state[0] = world->local_player;
    world->render_state[1] = world->local_player;
#endif
}

void pxl8_world_set_look(pxl8_world* world, f32 yaw, f32 pitch) {
    if (!world) return;
    world->local_player.yaw = yaw;
    world->local_player.pitch = pitch;
    world->pointer_motion = (pxl8_vec2){.yaw = yaw, .pitch = pitch};

#ifdef PXL8_ASYNC_THREADS
    world->render_state[0].yaw = yaw;
    world->render_state[0].pitch = pitch;
    world->render_state[1].yaw = yaw;
    world->render_state[1].pitch = pitch;
#endif
}

pxl8_sim_entity* pxl8_world_local_player(pxl8_world* world) {
    if (!world) return NULL;
#ifdef PXL8_ASYNC_THREADS
    const pxl8_sim_entity* state = pxl8_world_get_render_state(world);
    if (!state) return NULL;
    if (!(state->flags & PXL8_SIM_FLAG_ALIVE)) return NULL;
    return (pxl8_sim_entity*)state;
#else
    if (!(world->local_player.flags & PXL8_SIM_FLAG_ALIVE)) return NULL;
    return &world->local_player;
#endif
}

void pxl8_world_predict(pxl8_world* world, pxl8_net* net, const pxl8_input_msg* input, f32 dt) {
    if (!world || !net || !input) return;
    if (!(world->local_player.flags & PXL8_SIM_FLAG_ALIVE)) return;

    pxl8_sim_world sim = pxl8_world_sim_world(world, world->local_player.pos);
    pxl8_sim_move_player(&world->local_player, input, &sim, &world->sim_config, dt);

    world->client_tick++;

    entity_to_userdata(&world->local_player, pxl8_net_predicted_state(net));
    pxl8_net_predicted_tick_set(net, world->client_tick);
}

void pxl8_world_reconcile(pxl8_world* world, pxl8_net* net, f32 dt) {
    if (!world || !net) return;
    if (!(world->local_player.flags & PXL8_SIM_FLAG_ALIVE)) return;
    if (!pxl8_net_needs_correction(net)) return;

    u64 player_id = pxl8_net_player_id(net);
    const u8* server_state = pxl8_net_entity_userdata(net, player_id);
    if (!server_state) return;

    pxl8_sim_entity server_player = {0};
    userdata_to_entity(server_state, &server_player);

    if (!(server_player.flags & PXL8_SIM_FLAG_ALIVE)) {
        return;
    }

    world->local_player = server_player;

    const pxl8_snapshot_header* snap = pxl8_net_snapshot(net);
    u64 server_tick = snap ? snap->tick : 0;

    for (u64 tick = server_tick + 1; tick <= world->client_tick; tick++) {
        const pxl8_input_msg* input = pxl8_net_input_at(net, tick);
        if (!input) continue;

        pxl8_sim_world sim = pxl8_world_sim_world(world, world->local_player.pos);
        pxl8_sim_move_player(&world->local_player, input, &sim, &world->sim_config, dt);
    }

    entity_to_userdata(&world->local_player, pxl8_net_predicted_state(net));
}

#ifdef PXL8_ASYNC_THREADS

#define SIM_TIMESTEP (1.0f / 60.0f)

static void pxl8_world_sim_tick(pxl8_world* world, f32 dt) {
    bool alive = (world->local_player.flags & PXL8_SIM_FLAG_ALIVE) != 0;
    pxl8_input_msg merged = {0};
    pxl8_input_msg* input = NULL;

    while ((input = pxl8_queue_pop(&world->input_queue))) {
        merged.look_dx += input->look_dx;
        merged.look_dy += input->look_dy;
        merged.move_x = input->move_x;
        merged.move_y = input->move_y;
        merged.buttons |= input->buttons;
        pxl8_free(input);
    }

    if (!alive) {
        return;
    }

    const f32 MAX_LOOK_DELTA = 100.0f;
    if (merged.look_dx > MAX_LOOK_DELTA) merged.look_dx = MAX_LOOK_DELTA;
    if (merged.look_dx < -MAX_LOOK_DELTA) merged.look_dx = -MAX_LOOK_DELTA;
    if (merged.look_dy > MAX_LOOK_DELTA) merged.look_dy = MAX_LOOK_DELTA;
    if (merged.look_dy < -MAX_LOOK_DELTA) merged.look_dy = -MAX_LOOK_DELTA;

    merged.tick = world->client_tick;
    merged.timestamp = pxl8_get_ticks_ns();
    merged.yaw = world->pointer_motion.yaw;
    if (world->net) {
        pxl8_net_send_input(world->net, &merged);
    }

    world->local_player.yaw = world->pointer_motion.yaw;
    world->local_player.pitch = world->pointer_motion.pitch;
    merged.look_dx = 0;
    merged.look_dy = 0;

    pxl8_sim_world sim = pxl8_world_sim_world(world, world->local_player.pos);
    pxl8_sim_move_player(&world->local_player, &merged, &sim, &world->sim_config, dt);

    if (world->net) {
        entity_to_userdata(&world->local_player, pxl8_net_predicted_state(world->net));
        pxl8_net_predicted_tick_set(world->net, world->client_tick);
    }

    world->client_tick++;
}

static void pxl8_world_swap_buffers(pxl8_world* world) {
    u32 back = atomic_load(&world->active_buffer) ^ 1;
    world->render_state[back] = world->local_player;
    atomic_store(&world->active_buffer, back);
}

static int pxl8_world_sim_thread(void* data) {
    pxl8_world* world = (pxl8_world*)data;
    u64 last_time = pxl8_get_ticks_ns();

    while (atomic_load(&world->sim_running)) {
        if (atomic_load(&world->sim_paused)) {
            last_time = pxl8_get_ticks_ns();
            pxl8_sleep_ms(1);
            continue;
        }

        u64 now = pxl8_get_ticks_ns();
        f32 dt = (f32)(now - last_time) / 1e9f;
        last_time = now;

        if (dt > 0.1f) dt = 0.1f;
        if (dt < 0.0001f) dt = 0.0001f;

        world->sim_accumulator += dt;

        while (world->sim_accumulator >= SIM_TIMESTEP) {
            pxl8_world_chunk_cache_tick(world->chunk_cache);

            if (world->net) {
                pxl8_packet* pkt;
                while ((pkt = pxl8_net_pop_packet(world->net))) {
                    pxl8_net_process_packet(world->net, pkt);
                    pxl8_net_packet_free(pkt);
                }

                pxl8_world_sync(world, world->net);
                pxl8_world_reconcile(world, world->net, SIM_TIMESTEP);
            }

            pxl8_world_sim_tick(world, SIM_TIMESTEP);
            world->sim_accumulator -= SIM_TIMESTEP;
        }

        pxl8_world_swap_buffers(world);
        pxl8_sleep_ms(1);
    }

    return 0;
}

void pxl8_world_start_sim_thread(pxl8_world* world, pxl8_net* net) {
    if (!world || world->sim_thread) return;

    world->net = net;
    pxl8_queue_init(&world->input_queue);
    atomic_store(&world->active_buffer, 0);
    atomic_store(&world->sim_running, true);
    world->sim_accumulator = 0.0f;

    world->render_state[0] = world->local_player;
    world->render_state[1] = world->local_player;

    world->sim_thread = pxl8_thread_create(pxl8_world_sim_thread, "pxl8_sim", world);
}

void pxl8_world_stop_sim_thread(pxl8_world* world) {
    if (!world || !world->sim_thread) return;

    atomic_store(&world->sim_running, false);
    pxl8_thread_wait(world->sim_thread, NULL);
    world->sim_thread = NULL;

    pxl8_input_msg* input;
    while ((input = pxl8_queue_pop(&world->input_queue))) {
        pxl8_free(input);
    }
}

void pxl8_world_pause_sim(pxl8_world* world, bool paused) {
    if (!world) return;

    if (paused) {
        atomic_store(&world->sim_paused, true);
    } else {
        pxl8_input_msg* input;
        while ((input = pxl8_queue_pop(&world->input_queue))) {
            pxl8_free(input);
        }
        world->sim_accumulator = 0.0f;
        atomic_store(&world->sim_paused, false);
    }
}

void pxl8_world_push_input(pxl8_world* world, const pxl8_input_msg* input) {
    if (!world || !input) return;

    world->pointer_motion.yaw -= input->look_dx * 0.008f;
    f32 pitch = world->pointer_motion.pitch - input->look_dy * 0.008f;
    if (pitch > world->sim_config.max_pitch) pitch = world->sim_config.max_pitch;
    if (pitch < -world->sim_config.max_pitch) pitch = -world->sim_config.max_pitch;
    world->pointer_motion.pitch = pitch;

    pxl8_input_msg* copy = pxl8_malloc(sizeof(pxl8_input_msg));
    if (copy) {
        *copy = *input;
        if (!pxl8_queue_push(&world->input_queue, copy)) {
            pxl8_free(copy);
        }
    }
}

const pxl8_sim_entity* pxl8_world_get_render_state(const pxl8_world* world) {
    if (!world) return NULL;
    u32 front = atomic_load(&((pxl8_world*)world)->active_buffer);
    return &world->render_state[front];
}

f32 pxl8_world_get_interp_alpha(const pxl8_world* world) {
    if (!world) return 1.0f;
    return world->sim_accumulator / SIM_TIMESTEP;
}

#endif