#include "resource.h"
#include "app.h"
#include "arena.h"
#include "tar.h"
#include "incbin.h"
#include "util.h"

/* ========================== *
 * Global data
 * ========================== */

#if RESOURCES_EMBEDDED
# include "inc.h"
#endif

/* Add resource data to binary */

GLOBAL struct {
    struct arena arena;

#if RESOURCES_EMBEDDED
    struct tar_archive archive;
#endif

#if RESOURCE_RELOADING
    struct sys_thread resource_watch_monitor_thread;
    struct sys_thread resource_watch_dispatch_thread;

    struct sys_watch watch;
    struct atomic_i32 watch_shutdown;

    struct sys_mutex watch_dispatcher_mutex;
    struct arena watch_dispatcher_info_arena;
    struct sys_watch_info_list watch_dispatcher_info_list;
    struct sys_condition_variable watch_dispatcher_cv;

    struct sys_mutex watch_callbacks_mutex;
    resource_watch_callback *watch_callbacks[64];
    u64 num_watch_callbacks;
#endif
} G = ZI, DEBUG_ALIAS(G, G_resource);

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

#if RESOURCE_RELOADING
INTERNAL SYS_THREAD_ENTRY_POINT_FUNC_DEF(resource_watch_monitor_thread_entry_point, _);
INTERNAL SYS_THREAD_ENTRY_POINT_FUNC_DEF(resource_watch_dispatcher_thread_entry_point, _);
INTERNAL APP_EXIT_CALLBACK_FUNC_DEF(resource_shutdown);
#endif

struct resource_startup_receipt resource_startup(void)
{
    G.arena = arena_alloc(GIGABYTE(64));

#if RESOURCES_EMBEDDED
    struct string embedded_data = inc_res_tar();
    if (embedded_data.len <= 0) {
        sys_panic(LIT("No embedded resources found"));
    }
    G.archive = tar_parse(&G.arena, embedded_data, LIT(""));
#else
    /* Ensure we have the right working directory */
    if (!sys_is_dir(LIT("res"))) {
        sys_panic(LIT("Resource directory \"res\" not found. Make sure the executable is being launched from the correct working directory."));
    }
#endif

#if RESOURCE_RELOADING
    G.watch = sys_watch_alloc(LIT("res"));
    G.watch_callbacks_mutex = sys_mutex_alloc();

    G.watch_dispatcher_mutex = sys_mutex_alloc();
    G.watch_dispatcher_info_arena = arena_alloc(GIGABYTE(64));
    G.watch_dispatcher_cv = sys_condition_variable_alloc();

    app_register_exit_callback(&resource_shutdown);
    G.resource_watch_monitor_thread = sys_thread_alloc(resource_watch_monitor_thread_entry_point, NULL, LIT("[P2] Resource watch monitor"));
    G.resource_watch_dispatch_thread = sys_thread_alloc(resource_watch_dispatcher_thread_entry_point, NULL, LIT("[P2] Resource watch dispatcher"));
#endif


    return (struct resource_startup_receipt) { 0 };
}

/* ========================== *
 * Open / close
 * ========================== */

struct resource resource_open(struct string name)
{
    __prof;
#if RESOURCES_EMBEDDED
    struct resource res = ZI;
    struct tar_entry *entry = tar_get(&G.archive, name);
    if (entry) {
        res._data = entry->data;
        res._name = entry->file_name;
        res._exists = true;
    }
    return res;
#else
    struct resource res = ZI;
    if (name.len < ARRAY_COUNT(res._name_text)) {
        u8 path_text[RESOURCE_NAME_LEN_MAX + (sizeof("res/") - 1)];
        struct string path = ZI;
        {
            path_text[0] = 'r';
            path_text[1] = 'e';
            path_text[2] = 's';
            path_text[3] = '/';
            u64 path_text_len = 4;
            MEMCPY(path_text + path_text_len, name.text, name.len);
            path_text_len += name.len;
            path = STRING(path_text_len, path_text);
        }

        struct sys_file file = sys_file_open_read_wait(path);
        struct sys_file_map file_map = ZI;
        struct string data = ZI;
        if (file.valid) {
            file_map = sys_file_map_open_read(file);
            if (file_map.valid) {
                data = sys_file_map_data(file_map);
            } else {
                sys_file_map_close(file_map);
            }
        } else {
            sys_file_close(file);
        }

        res._exists = file.valid && file_map.valid;
        res._data = data;
        res._file = file;
        res._file_map = file_map;
        res._name_len = name.len;
        MEMCPY(res._name_text, name.text, name.len);
    } else {
        ASSERT(false);
    }
    return res;
#endif
}

#if !RESOURCES_EMBEDDED
void resource_close(struct resource *res_ptr)
{
    sys_file_map_close(res_ptr->_file_map);
    sys_file_close(res_ptr->_file);
}
#endif

/* ========================== *
 * Watch
 * ========================== */

#if RESOURCE_RELOADING

INTERNAL APP_EXIT_CALLBACK_FUNC_DEF(resource_shutdown)
{
    __prof;
    atomic_i32_eval_exchange(&G.watch_shutdown, 1);

    sys_condition_variable_broadcast(&G.watch_dispatcher_cv);
    sys_watch_wake(&G.watch);

    sys_thread_wait_release(&G.resource_watch_dispatch_thread);
    sys_thread_wait_release(&G.resource_watch_monitor_thread);
}

void resource_register_watch_callback(resource_watch_callback *callback)
{
    struct sys_lock lock = sys_mutex_lock_e(&G.watch_callbacks_mutex);
    {
        if (G.num_watch_callbacks < ARRAY_COUNT(G.watch_callbacks)) {
            G.watch_callbacks[G.num_watch_callbacks++] = callback;
        } else {
            sys_panic(LIT("Max resource watch callbacks reached"));
        }
    }
    sys_mutex_unlock(&lock);
}

INTERNAL SYS_THREAD_ENTRY_POINT_FUNC_DEF(resource_watch_monitor_thread_entry_point, _)
{
    (UNUSED)_;
    struct arena_temp scratch = scratch_begin_no_conflict();

    while (!atomic_i32_eval(&G.watch_shutdown)) {
        struct arena_temp temp = arena_temp_begin(scratch.arena);
        struct sys_watch_info_list res = sys_watch_wait(temp.arena, &G.watch);
        if (res.first && !atomic_i32_eval(&G.watch_shutdown)) {
            struct sys_lock lock = sys_mutex_lock_e(&G.watch_dispatcher_mutex);
            {
                struct sys_watch_info_list list_part = sys_watch_info_copy(&G.watch_dispatcher_info_arena, res);
                if (G.watch_dispatcher_info_list.last) {
                    G.watch_dispatcher_info_list.last->next = list_part.first;
                    list_part.first->prev = G.watch_dispatcher_info_list.last;
                    G.watch_dispatcher_info_list.last = list_part.last;
                } else {
                    G.watch_dispatcher_info_list = list_part;
                }
            }
            sys_mutex_unlock(&lock);
            sys_condition_variable_broadcast(&G.watch_dispatcher_cv);
        }
        arena_temp_end(temp);
    }

    scratch_end(scratch);
}

/* NOTE: We separate the responsibilities of monitoring directory changes
 * & dispatching watch callbacks into two separate threads so that we can delay
 * the dispatch of these callbacks, allowing for deduplication of file
 * modification notifications. */

#define WATCH_DISPATCHER_DELAY_SECONDS 0.050
#define WATCH_DISPATCHER_DEDUP_DICT_BINS 128

INTERNAL SYS_THREAD_ENTRY_POINT_FUNC_DEF(resource_watch_dispatcher_thread_entry_point, _)
{
    (UNUSED)_;
    struct arena_temp scratch = scratch_begin_no_conflict();

    struct sys_lock watch_dispatcher_lock = sys_mutex_lock_e(&G.watch_dispatcher_mutex);
    while (!atomic_i32_eval(&G.watch_shutdown)) {
        sys_condition_variable_wait(&G.watch_dispatcher_cv, &watch_dispatcher_lock);
        if (!atomic_i32_eval(&G.watch_shutdown) && G.watch_dispatcher_info_arena.pos > 0) {
            /* Unlock and sleep a bit so duplicate events pile up */
            {
                sys_mutex_unlock(&watch_dispatcher_lock);
                sys_sleep(WATCH_DISPATCHER_DELAY_SECONDS);
                watch_dispatcher_lock = sys_mutex_lock_e(&G.watch_dispatcher_mutex);
            }
            if (!atomic_i32_eval(&G.watch_shutdown)) {
                struct arena_temp temp = arena_temp_begin(scratch.arena);

                /* Pull watch info from queue */
                struct sys_watch_info_list watch_info_list = sys_watch_info_copy(temp.arena, G.watch_dispatcher_info_list);
                MEMZERO_STRUCT(&G.watch_dispatcher_info_list);
                arena_reset(&G.watch_dispatcher_info_arena);

                /* Unlock and run callbacks */
                sys_mutex_unlock(&watch_dispatcher_lock);
                {
                    __profscope(run_resource_watch_callbacks);
                    struct dict dedup_dict = dict_init(temp.arena, WATCH_DISPATCHER_DEDUP_DICT_BINS);
                    for (struct sys_watch_info *info = watch_info_list.first; info; info = info->next) {
                        /* Do not run callbacks for the same file more than once */
                        b32 skip = false;
                        u64 hash = hash_fnv64(HASH_FNV64_BASIS, info->name);
                        if (dict_get(&dedup_dict, hash) == 1) {
                            skip = true;
                        } else {
                            dict_set(temp.arena, &dedup_dict, hash, 1);
                        }
                        if (!skip) {
                            struct sys_lock callbacks_lock = sys_mutex_lock_s(&G.watch_callbacks_mutex);
                            for (u64 i = 0; i < G.num_watch_callbacks; ++i) {
                                resource_watch_callback *callback = G.watch_callbacks[i];
                                callback(info->name);
                            }
                            sys_mutex_unlock(&callbacks_lock);
                        }
                    }
                }
                watch_dispatcher_lock = sys_mutex_lock_e(&G.watch_dispatcher_mutex);

                arena_temp_end(temp);
            }
        }
    }

    scratch_end(scratch);
}

#endif