#include "game.h"
#include "sys.h"
#include "util.h"
#include "world.h"
#include "sprite.h"
#include "sound.h"
#include "mixer.h"
#include "math.h"
#include "scratch.h"
#include "atomic.h"
#include "app.h"
#include "log.h"

GLOBAL struct {
    struct atomic_i32 game_thread_shutdown;
    struct sys_thread game_thread;

    /* Double buffered game state */
    struct world prev_world;  /* Last tick */
    struct world world;

    /* Game thread input */
    struct sys_mutex game_cmds_mutex;
    struct arena game_cmds_arena;

    /* Game thread output */
    struct sys_mutex published_tick_mutex;
    struct world published_tick;
    struct atomic_u64 published_tick_id;
} G = { 0 }, DEBUG_ALIAS(G, G_game);

/* ========================== *
 * Startup
 * ========================== */

INTERNAL APP_EXIT_CALLBACK_FUNC_DEF(game_shutdown);
INTERNAL SYS_THREAD_ENTRY_POINT_FUNC_DEF(game_thread_entry_point, arg);

struct game_startup_receipt game_startup(struct mixer_startup_receipt *mixer_sr,
                                         struct sprite_startup_receipt *sheet_sr,
                                         struct sound_startup_receipt *sound_sr)
{
    (UNUSED)mixer_sr;
    (UNUSED)sheet_sr;
    (UNUSED)sound_sr;

    /* Initialize game cmd storage */
    G.game_cmds_mutex = sys_mutex_alloc();
    G.game_cmds_arena = arena_alloc(GIGABYTE(64));

    /* Initialize world */
    world_alloc(&G.world);

    /* Initialize tick transmission */
    world_alloc(&G.published_tick);
    arena_set_readonly(&G.published_tick.entity_store->arena);
    G.published_tick_mutex = sys_mutex_alloc();

    G.world.timescale = GAME_TIMESCALE;
    G.game_thread = sys_thread_alloc(&game_thread_entry_point, NULL, STR("[P2] Game thread"));
    app_register_exit_callback(&game_shutdown);

    return (struct game_startup_receipt) { 0 };
}

INTERNAL APP_EXIT_CALLBACK_FUNC_DEF(game_shutdown)
{
    __prof;
    atomic_i32_eval_exchange(&G.game_thread_shutdown, true);
    sys_thread_wait_release(&G.game_thread);
}

/* ========================== *
 * Game cmd
 * ========================== */

INTERNAL void push_cmds(struct game_cmd_array cmd_array)
{
    struct sys_lock lock = sys_mutex_lock_e(&G.game_cmds_mutex);
    struct game_cmd *cmds = arena_push_array(&G.game_cmds_arena, struct game_cmd, cmd_array.count);
    MEMCPY(cmds, cmd_array.cmds, cmd_array.count * sizeof(*cmds));
    sys_mutex_unlock(&lock);
}

INTERNAL struct game_cmd_array pop_cmds(struct arena *arena)
{
    struct game_cmd_array array = { 0 };
    if (G.game_cmds_arena.pos > 0) {
        struct sys_lock lock = sys_mutex_lock_e(&G.game_cmds_mutex);
        struct buffer game_cmds_buff = arena_to_buffer(&G.game_cmds_arena);
        arena_align(arena, alignof(struct game_cmd));
        array.cmds = (struct game_cmd *)arena_push_array(arena, u8, game_cmds_buff.size);
        array.count = game_cmds_buff.size / sizeof(struct game_cmd);
        MEMCPY(array.cmds, game_cmds_buff.data, game_cmds_buff.size);
        arena_reset(&G.game_cmds_arena);
        sys_mutex_unlock(&lock);
    }
    return array;
}

/* ========================== *
 * Test
 * ========================== */

/* TODO: Remove this */

INTERNAL void spawn_test_entities(void)
{
    /* Player ent */
    struct entity *player_ent;
    {
        struct v2 pos = V2(1, 1);
        struct v2 size = V2(1, 1);
        f32 r = 0;

        struct entity *e = entity_alloc_top(G.world.entity_store);
        entity_set_xform(e, XFORM_TRS(.t = pos, .r = r, .s = size));

        e->sprite = sprite_tag_from_path(STR("res/graphics/tim.ase"));
        e->sprite_span_name = STR("idle.unarmed");
        //e->sprite_span_name = STR("idle.one_handed");
        //e->sprite_span_name = STR("idle.two_handed");

        entity_enable_prop(e, ENTITY_PROP_PLAYER_CONTROLLED);
        e->player_max_speed = 4.f;
        e->player_acceleration = 20.0f;
        e->control.focus = V2(0, -1);

        entity_enable_prop(e, ENTITY_PROP_ANIMATING);

        player_ent = e;

        //entity_enable_prop(e, ENTITY_PROP_TEST);
    }

    /* Child 1 */
    {
        struct v2 pos = V2(1, 0);
        struct v2 size = V2(1, 1);
        f32 r = PI / 4;

        struct xform xf = XFORM_TRS(.t = pos, .r = r, .s = size);

        struct entity *e = entity_alloc_top(G.world.entity_store);
        entity_set_local_xform(e, xf);

        e->sprite = sprite_tag_from_path(STR("res/graphics/gun.ase"));

        entity_enable_prop(e, ENTITY_PROP_ANIMATING);
        entity_enable_prop(e, ENTITY_PROP_WEAPON);

        player_ent->equipped = e->handle;
    }

    /* Camera ent */
    {
        struct entity *e = entity_alloc_top(G.world.entity_store);
        entity_set_xform(e, XFORM_IDENT);

        entity_enable_prop(e, ENTITY_PROP_CAMERA);
        entity_enable_prop(e, ENTITY_PROP_CAMERA_ACTIVE);
        e->camera_follow = player_ent->handle;

        f32 width = (f32)DEFAULT_CAMERA_WIDTH;
        f32 height = (f32)DEFAULT_CAMERA_HEIGHT;
        e->camera_quad_xform = XFORM_TRS(.s = V2(width, height));
    }
}

/* ========================== *
 * Update
 * ========================== */

INTERNAL void publish_game_tick(void)
{
    __prof;
    struct sys_lock lock = sys_mutex_lock_e(&G.published_tick_mutex);
    arena_set_readwrite(&G.published_tick.entity_store->arena);
    {
        world_copy_replace(&G.published_tick, &G.world);
    }
    arena_set_readonly(&G.published_tick.entity_store->arena);
    atomic_u64_eval_exchange(&G.published_tick_id, G.published_tick.tick_id);
    sys_mutex_unlock(&lock);
}

INTERNAL void game_update(void)
{
    __prof;

    struct temp_arena scratch = scratch_begin_no_conflict();

    /* ========================== *
     * Begin frame
     * ========================== */

    ++G.world.tick_id;
    G.world.tick_ts = sys_timestamp();
    G.world.dt = max_f64(0.0, (1.0 / GAME_FPS) * G.world.timescale);
    G.world.time += G.world.dt;

    struct game_cmd_array game_cmds = pop_cmds(scratch.arena);
    struct entity_store *store = G.world.entity_store;
    struct entity *root = entity_from_handle(store, store->root);
    struct sprite_scope *sprite_frame_scope = sprite_scope_begin();

    /* ========================== *
     * Spawn test entities
     * ========================== */

    /* TODO: remove this (testing) */
    /* Initialize entities */
    static b32 run = 0;
    if (!run) {
        run = 1;
        spawn_test_entities();
    }

    /* ========================== *
     * Process global game cmds
     * ========================== */

    for (u64 cmd_index = 0; cmd_index < game_cmds.count; ++cmd_index) {
        struct game_cmd cmd = game_cmds.cmds[cmd_index];

        switch (cmd.kind) {
            /* Clear level */
            case GAME_CMD_KIND_CLEAR_ALL: {
                logf_info("Clearing level");
                for (u64 i = 0; i < store->count; ++i) {
                    struct entity *ent = &store->entities[i];
                    if (ent->valid && !ent->is_root) {
                        entity_release(store, ent);
                    }
                }
            } break;

            /* Spawn test */
            case GAME_CMD_KIND_SPAWN_TEST: {
                logf_info("Spawning (test)");
                spawn_test_entities();
            } break;

            default: break;
        };
    }

    /* ========================== *
     * Update sprite from animation
     * ========================== */

    for (u64 entity_index = 0; entity_index < store->count; ++entity_index) {
        struct entity *ent = &store->entities[entity_index];
        if (!ent->valid) continue;
        if (sprite_tag_is_nil(ent->sprite)) continue;

        /* ========================== *
         * Update sprite animation
         * ========================== */

        if (entity_has_prop(ent, ENTITY_PROP_ANIMATING)) {
            struct sprite_sheet *sheet = sprite_sheet_from_tag_await(sprite_frame_scope, ent->sprite);
            struct sprite_sheet_span span = sprite_sheet_get_span(sheet, ent->sprite_span_name);

            f64 time_in_frame = ent->animation_time_in_frame + G.world.dt;
            u64 frame_index = ent->animation_frame;
            if (frame_index < span.start || frame_index > span.end) {
                frame_index = span.start;
            }

            struct sprite_sheet_frame frame = sprite_sheet_get_frame(sheet, frame_index);
            while (time_in_frame > frame.duration) {
                time_in_frame -= frame.duration;
                ++frame_index;
                if (frame_index > span.end) {
                    /* Loop animation */
                    frame_index = span.start;
                }
                frame = sprite_sheet_get_frame(sheet, frame_index);
            }

            ent->animation_time_in_frame = time_in_frame;
            ent->animation_frame = frame_index;
        }

        /* ========================== *
         * Update sprite xform
         * ========================== */

        struct sprite_sheet *sheet = sprite_sheet_from_tag_await(sprite_frame_scope, ent->sprite);
        struct sprite_sheet_slice slice = sprite_sheet_get_slice(sheet, STR("pivot"), ent->animation_frame);
        struct v2 sprite_size = v2_div(sheet->frame_size, (f32)PIXELS_PER_UNIT);

        struct v2 dir = v2_mul_v2(sprite_size, slice.dir);
        f32 rot = v2_angle(dir) + PI / 2;

        struct xform xf = XFORM_IDENT;
        xf = xform_rotate(xf, -rot);
        xf = xform_scale(xf, sprite_size);
        xf = xform_translate(xf, v2_neg(slice.center));
        ent->sprite_local_xform = xf;
    }

    /* ========================== *
     * Update entities from cmds
     * ========================== */

    for (u64 entity_index = 0; entity_index < store->count; ++entity_index) {
        struct entity *ent = &store->entities[entity_index];
        if (!ent->valid) continue;

        /* ========================== *
         * Initialize test
         * ========================== */

        /* ENTITY_PROP_TEST */
        if (entity_has_prop(ent, ENTITY_PROP_TEST) && !ent->test_initialized) {
            ent->test_initialized = true;
            ent->test_start_local_xform = entity_get_local_xform(ent);
            ent->test_start_sprite_xform = ent->sprite_local_xform;
        }

        /* ========================== *
         * Update control from player cmds
         * ========================== */

        if (entity_has_prop(ent, ENTITY_PROP_PLAYER_CONTROLLED)) {
            /* Process cmds */
            struct v2 move = ent->control.move;
            struct v2 focus = ent->control.focus;
            b32 firing = entity_has_prop(ent, ENTITY_PROP_TRIGGERING_EQUIPPED);

            for (u64 i = 0; i < game_cmds.count; ++i) {
                struct game_cmd cmd = game_cmds.cmds[i];
                b32 start = cmd.state == GAME_CMD_STATE_START;
                b32 stop = cmd.state == GAME_CMD_STATE_STOP;
                (UNUSED)start;
                (UNUSED)stop;

                /* TODO: Combine movement from multiple inputs? E.G. a sudden
                 * start and immediate stop cmd should still move the player a
                 * tad. */
                switch (cmd.kind) {
                    case GAME_CMD_KIND_PLAYER_MOVE: {
                        move = cmd.move_dir;
                        focus = v2_sub(cmd.aim_pos, entity_get_xform(ent).og);
                    } break;

                    case GAME_CMD_KIND_PLAYER_FIRE: {
                        if (start) {
                            firing = true;
                        } else if (stop) {
                            firing = false;
                        }
                    } break;

                    default: break;
                }
            }

            /* Movement */
            if (v2_len_squared(move) > 1) {
                /* Cap movement vector magnitude at 1 */
                move = v2_norm(move);
            }
            ent->control.move = move;
            ent->control.focus = focus;

            /* Firing */
            if (firing) {
                entity_enable_prop(ent, ENTITY_PROP_TRIGGERING_EQUIPPED);
            } else {
                entity_disable_prop(ent, ENTITY_PROP_TRIGGERING_EQUIPPED);
            }
        }

        /* ========================== *
         * Test
         * ========================== */

        /* ENTITY_PROP_TEST */
        if (entity_has_prop(ent, ENTITY_PROP_TEST)) {
            f32 t = ((f32)G.world.time);
            struct v2 og = v2_mul(V2(math_cos(t), math_sin(t)), 3);
            f32 r = t * 3;
            struct v2 s = V2(1 + (math_fabs(math_sin(t * 5)) * 3), 1);
            (UNUSED)og;
            (UNUSED)r;
            (UNUSED)s;

            og = v2_add(og, ent->test_start_local_xform.og);
            r += xform_get_rotation(ent->test_start_local_xform);
            s = v2_add(s, xform_get_scale(ent->test_start_local_xform));


            struct xform xf = entity_get_local_xform(ent);
            xf.og = og;
            xf= xform_with_rotation(xf, r);
            xf= xform_with_scale(xf, s);
            entity_set_local_xform(ent, xf);
        }
    }

    /* ========================== *
     * Activate triggers
     * ========================== */

    for (u64 entity_index = 0; entity_index < store->count; ++entity_index) {
        struct entity *ent = &store->entities[entity_index];
        if (!ent->valid) continue;

        /* Trigger equipped */
        if (entity_has_prop(ent, ENTITY_PROP_TRIGGERING_EQUIPPED)) {
            struct entity *eq = entity_from_handle(store, ent->equipped);
            if (eq->valid) {
                entity_enable_prop(eq, ENTITY_PROP_TRIGGERED_THIS_TICK);
            }
        }

    }

    /* ========================== *
     * Simulate entity physics
     * ========================== */

    for (u64 entity_index = 0; entity_index < store->count; ++entity_index) {
        struct entity *ent = &store->entities[entity_index];
        if (!ent->valid) continue;

        /* ========================== *
         * Weapon firing
         * ========================== */

        if (entity_has_prop(ent, ENTITY_PROP_WEAPON)) {
            if (entity_has_prop(ent, ENTITY_PROP_TRIGGERED_THIS_TICK)) {
                ent->sprite_tint = RGBA_32_F(1, 0, 0, 1);
            } else {
                ent->sprite_tint = RGBA_32_F(1, 1, 1, 1);
            }
        }

        /* ========================== *
         * Player angle
         * ========================== */

        if (entity_has_prop(ent, ENTITY_PROP_PLAYER_CONTROLLED)) {
            struct xform xf = entity_get_xform(ent);

            /* Solve for final angle using law of sines */
            f32 final_xf_angle;
            {
                struct sprite_sheet *sheet = sprite_sheet_from_tag_await(sprite_frame_scope, ent->sprite);
                struct sprite_sheet_slice slice = sprite_sheet_get_slice(sheet, STR("hold"), ent->animation_frame);

                f32 forward_hold_angle_offset;
                {
                    struct xform xf_unrotated = xform_with_rotation(xf, 0);
                    struct v2 hold_pos_unrotated = xform_mul_v2(xf_unrotated, xform_mul_v2(ent->sprite_local_xform, slice.center));
                    forward_hold_angle_offset = v2_angle_from_dirs(V2(0, -1), v2_sub(hold_pos_unrotated, xf_unrotated.og));
                }

                struct v2 ent_pos = xf.og;
                struct v2 focus_pos = v2_add(ent_pos, ent->control.focus);

                struct v2 hold_pos;
                {
                    struct xform hold_pos_xf = xform_translate(ent->sprite_local_xform, slice.center);
                    hold_pos_xf = xform_mul(xf, hold_pos_xf);

                    struct v2 hold_pos_xf_dir = xform_basis_mul_v2(hold_pos_xf, slice.dir);
                    hold_pos_xf = xform_with_rotation(hold_pos_xf, v2_angle(hold_pos_xf_dir) + PI / 2);

                    if (v2_eq(hold_pos_xf.og, ent_pos)) {
                        /* If hold pos is same as origin (E.G if pivot is being used as hold pos), then move hold pos forward a tad to avoid issue */
                        hold_pos_xf = xform_translate(hold_pos_xf, V2(0, -1));
                    }
                    hold_pos = hold_pos_xf.og;
                }

                struct v2 hold_dir = xform_basis_mul_v2(xf, xform_basis_mul_v2(ent->sprite_local_xform, slice.dir));
                struct v2 hold_ent_dir = v2_sub(ent_pos, hold_pos);
                struct v2 focus_ent_dir = v2_sub(ent_pos, focus_pos);

                f32 hold_ent_len = v2_len(hold_ent_dir);
                f32 focus_ent_len = v2_len(focus_ent_dir);

                f32 final_hold_angle_btw_ent_and_focus = v2_angle_from_dirs(hold_ent_dir, hold_dir);
                f32 final_focus_angle_btw_ent_and_hold = math_asin((math_sin(final_hold_angle_btw_ent_and_focus) * hold_ent_len) / focus_ent_len);
                f32 final_ent_angle_btw_focus_and_hold = PI - (final_focus_angle_btw_ent_and_hold + final_hold_angle_btw_ent_and_focus);

                final_xf_angle = v2_angle_from_dirs(V2(0, -1), v2_sub(focus_pos, ent_pos)) + final_ent_angle_btw_focus_and_hold - forward_hold_angle_offset;
            }

            if (!F32_IS_NAN(final_xf_angle)) {
                entity_set_xform(ent, xform_with_rotation(xf, final_xf_angle));
            }
        }

        /* ========================== *
         * Player movement
         * ========================== */

        if (entity_has_prop(ent, ENTITY_PROP_PLAYER_CONTROLLED)) {
            f32 max_speed = ent->player_max_speed;
            f32 acceleration_rate = ent->player_acceleration;
            acceleration_rate = clamp_f32(acceleration_rate, 0, GAME_FPS);  /* Can't integrate acceleration rate higher than FPS */
            struct v2 target_velocity = v2_mul(ent->control.move, max_speed);
            struct v2 target_acceleration = v2_sub(target_velocity, ent->velocity);
            ent->acceleration = v2_mul(target_acceleration, acceleration_rate);
        }

        /* ========================== *
         * Integrate acceleration & velocity
         * ========================== */

        {
            f32 dt = (f32)G.world.dt;

            /* Apply acceleration to velocity */
            struct v2 a = v2_mul(ent->acceleration, dt);
            ent->velocity = v2_add(ent->velocity, a);

            /* Apply velocity to position */
            struct xform xf = entity_get_xform(ent);
            xf.og = v2_add(xf.og, v2_mul(ent->velocity, dt));
            entity_set_xform(ent, xf);
        }
    }

    /* ========================== *
     * Update entities post-simulation
     * ========================== */

    for (u64 entity_index = 0; entity_index < store->count; ++entity_index) {
        struct entity *ent = &store->entities[entity_index];
        if (!ent->valid) continue;

        /* ========================== *
         * Update camera position
         * ========================== */

        /* Camera follow */
        if (entity_has_prop(ent, ENTITY_PROP_CAMERA)) {
            struct entity *follow = entity_from_handle(store, ent->camera_follow);

            struct xform xf = entity_get_xform(ent);

            if (entity_has_prop(follow, ENTITY_PROP_PLAYER_CONTROLLED)) {
                f32 aspect_ratio = 1.0;
                {
                    struct xform quad_xf = xform_mul(entity_get_xform(ent), ent->camera_quad_xform);
                    struct v2 camera_size = xform_get_scale(quad_xf);
                    if (!v2_eq(camera_size, V2(0, 0))) {
                        aspect_ratio = camera_size.x / camera_size.y;
                    }
                }
                f32 ratio_y = 0.33f;
                f32 ratio_x = ratio_y / aspect_ratio;
                struct v2 camera_focus_dir = v2_mul_v2(follow->control.focus, V2(ratio_x, ratio_y));
                struct v2 camera_focus_pos = v2_add(entity_get_xform(follow).og, camera_focus_dir);
                ent->camera_xform_target = xf;
                ent->camera_xform_target.og = camera_focus_pos;
            }

            /* Lerp camera */
            if (ent->camera_applied_lerp_continuity_gen_plus_one == ent->camera_lerp_continuity_gen + 1) {
                f32 t = 1 - math_pow(2.f, -20.f * (f32)G.world.dt);
                xf = xform_lerp(xf, ent->camera_xform_target, t);
            } else {
                /* Skip lerp */
                xf = ent->camera_xform_target;
            }
            ent->camera_applied_lerp_continuity_gen_plus_one = ent->camera_lerp_continuity_gen + 1;
            entity_set_xform(ent, xf);
        }

        /* ========================== *
         *  Update sound emitters
         * ========================== */

        if (entity_has_prop(ent, ENTITY_PROP_TEST_SOUND_EMITTER)) {
            struct mixer_desc desc = ent->sound_desc;
            desc.speed = G.world.timescale;

            desc.pos = entity_get_xform(ent).og;
            struct sound *sound = sound_load_async(ent->sound_name, 0);
            b32 played = ent->sound_handle.gen != 0;
            if (sound) {
                if (!played) {
                    ent->sound_handle = mixer_play_ex(sound, desc);
                } else {
                    mixer_track_set(ent->sound_handle, desc);
                }
            }
        }
    }

    /* ========================== *
     * Publish tick
     * ========================== */

    /* Update cached global xforms to ensure they're accurate in published tick */
    {
        struct temp_arena temp = arena_temp_begin(scratch.arena);

        struct stack_node {
            struct entity *entity;
            struct xform parent_global_xform;
        };

        /* Depth first iteration */
        *arena_push(temp.arena, struct stack_node) = (struct stack_node) { .entity = root, .parent_global_xform = XFORM_IDENT };
        u64 stack_count = 1;
        while (stack_count > 0) {
            /* Pull from top of stack */
            struct stack_node node;
            arena_pop(temp.arena, struct stack_node, &node);
            --stack_count;

            struct entity *child = node.entity;

            /* Calculate world xform */
            struct xform xf;
            if (child->cached_global_xform_dirty) {
                xf = xform_mul(node.parent_global_xform, child->local_xform);
                child->cached_global_xform = xf;
                child->cached_global_xform_dirty = false;
            } else {
                xf = child->cached_global_xform;
            }

            /* Append sub-children to stack */
            struct entity *subchild = entity_from_handle(store, child->last);
            while (subchild->valid) {
                *arena_push(temp.arena, struct stack_node) = (struct stack_node) { .entity = subchild, .parent_global_xform = xf };
                ++stack_count;
                subchild = entity_from_handle(store, subchild->prev);
            }
        }

        arena_temp_end(temp);
    }

    /* Publish tick */
    publish_game_tick();
    __profframe("Game");

    /* ========================== *
     * Reset triggered entities
     * ========================== */

    for (u64 entity_index = 0; entity_index < store->count; ++entity_index) {
        struct entity *ent = &store->entities[entity_index];
        if (!ent->valid) continue;

        if (entity_has_prop(ent, ENTITY_PROP_TRIGGERED_THIS_TICK)) {
            entity_disable_prop(ent, ENTITY_PROP_TRIGGERED_THIS_TICK);
        }
    }

    /* ========================== *
     * End frame cache scopes
     * ========================== */

    sprite_scope_end(sprite_frame_scope);

    scratch_end(scratch);
}

/* ========================== *
 * Game thread
 * ========================== */

INTERNAL SYS_THREAD_ENTRY_POINT_FUNC_DEF(game_thread_entry_point, arg)
{
    (UNUSED)arg;
    sys_timestamp_t last_frame_ts = 0;
    f64 target_dt = GAME_FPS > (0) ? (1.0 / GAME_FPS) : 0;
    while (!atomic_i32_eval(&G.game_thread_shutdown)) {
        __profscope(game_update_w_sleep);
        sleep_frame(last_frame_ts, target_dt);
        last_frame_ts = sys_timestamp();
        game_update();
    }
}

/* ========================== *
 * Interface
 * ========================== */

void game_get_latest_tick(struct world *dest)
{
    __prof;
    struct sys_lock lock = sys_mutex_lock_e(&G.published_tick_mutex);
    world_copy_replace(dest, &G.published_tick);
    sys_mutex_unlock(&lock);
}

u64 game_get_latest_tick_id(void)
{
    return atomic_u64_eval(&G.published_tick_id);
}

void game_push_cmds(struct game_cmd_array cmd_array)
{
    push_cmds(cmd_array);
}