townengine/src/twn_filewatch.c

#include "twn_filewatch_c.h"
#include "twn_util.h"
#include "twn_engine_context_c.h"

#include <x-watcher.h>
#include <stb_ds.h>
#include <SDL2/SDL.h>


struct FilewatchPathToCallback {
    char *path;
    FileatchCallback callback;
    float tick_last_reported;
    enum FilewatchAction action_pending : 3;
    bool action_processed : 1;
};

static struct FilewatchPathToCallback *filewatch_directories;
static struct FilewatchPathToCallback *filewatch_files;
/* note: it gets rebuilt on every addition, as api is such */
/* TODO: test whether it's possible to miss on update while watcher is being rebuilt */
/*       we might have to enumerate things, just to make sure */
static x_watcher *filewatcher;
static SDL_mutex *filewatcher_lock;

/* TODO: check whether path and p->path match? */
static void filewatch_dispatch(XWATCHER_FILE_EVENT event,
                               const char *path,
                               int context,
                               void *additional_data
) {
    (void)additional_data; (void)path;

    enum FilewatchAction action;

    switch (event) {
    case XWATCHER_FILE_CREATED:
        action = FILEWATCH_ACTION_FILE_CREATED;
        break;
    case XWATCHER_FILE_REMOVED:
        action = FILEWATCH_ACTION_FILE_DELETED;
        break;
    case XWATCHER_FILE_MODIFIED:
        action = FILEWATCH_ACTION_FILE_MODIFIED;
        break;
    case XWATCHER_FILE_NONE:
    case XWATCHER_FILE_OPENED:
    case XWATCHER_FILE_RENAMED:
    case XWATCHER_FILE_UNSPECIFIED:
    case XWATCHER_FILE_ATTRIBUTES_CHANGED:
    default:
        return;
    }

    SDL_LockMutex(filewatcher_lock);

    struct FilewatchPathToCallback *p;

    if (context < 0)
        p = &filewatch_files[-context - 1];
    else
        p = &filewatch_directories[context];

    p->tick_last_reported = ctx.game.frame_number;
    p->action_processed = false;
    p->action_pending = action;

    SDL_UnlockMutex(filewatcher_lock);
}


static bool filewatcher_rebuild(void) {
    if (filewatcher)
        xWatcher_destroy(filewatcher);

    filewatcher = xWatcher_create();
    if (!filewatcher) {
        log_warn("Error creating xWatcher instance, no file watching is done");
        return false;
    }

    int const filewatch_directories_len = arrlen(filewatch_directories);
    for (int i = 0; i < filewatch_directories_len; ++i) {
        xWatcher_reference ref = {
            .path = filewatch_directories[i].path,
            .callback_func = filewatch_dispatch,
            .context = i,
        };
        if (!xWatcher_appendDir(filewatcher, &ref))
            log_warn("Error watching dir contents: %s", filewatch_directories[i].path);
    }

    int const filewatch_files_len = arrlen(filewatch_files);
    for (int i = 0; i < filewatch_files_len; ++i) {
        xWatcher_reference ref = {
            .path = filewatch_files[i].path,
            .callback_func = filewatch_dispatch,
            .context = -(i + 1), /* in negative range to allow inrefence */
        };
        if (!xWatcher_appendDir(filewatcher, &ref))
            log_warn("Error watching file: %s", filewatch_files[i].path);
    }

    if (!xWatcher_start(filewatcher)) {
        log_warn("Error creating xWatcher instance, no file watching is done");
        xWatcher_destroy(filewatcher);
        filewatcher = NULL;
        return false;
    }

    return true;
}


bool filewatch_add_directory(char *dir, FileatchCallback callback) {
    SDL_assert(dir && callback);

    struct FilewatchPathToCallback const w = {
        .callback = callback,
        .path = SDL_strdup(dir),
        .action_processed = true,
        .tick_last_reported = ctx.game.frame_number,
    };
    arrpush(filewatch_directories, w);

    return filewatcher_rebuild();
}


bool filewatch_add_file(char *filepath, FileatchCallback callback) {
    SDL_assert(filepath && callback);

    struct FilewatchPathToCallback const f = {
        .callback = callback,
        .path = SDL_strdup(filepath),
        .action_processed = true,
        .tick_last_reported = ctx.game.frame_number,
    };
    arrpush(filewatch_files, f);

    return filewatcher_rebuild();
}


void filewatch_poll(void) {
    SDL_LockMutex(filewatcher_lock);

    int const filewatch_directories_len = arrlen(filewatch_directories);
    for (int i = 0; i < filewatch_directories_len; ++i) {
        if (!filewatch_directories[i].action_processed
                && (ctx.game.frame_number - filewatch_directories[i].tick_last_reported > FILEWATCH_MODIFIED_TICKS_MERGED)) {
            SDL_assert(filewatch_directories[i].action_pending != FILEWATCH_ACTION_FILE_NONE);
            filewatch_directories[i].callback(filewatch_directories[i].path, filewatch_directories[i].action_pending);
            filewatch_directories[i].action_pending = FILEWATCH_ACTION_FILE_NONE;
            filewatch_directories[i].action_processed = true;
        }
    }

    int const filewatch_files_len = arrlen(filewatch_files);
    for (int i = 0; i < filewatch_files_len; ++i) {
        if (!filewatch_files[i].action_processed
                && (ctx.game.frame_number - filewatch_files[i].tick_last_reported > FILEWATCH_MODIFIED_TICKS_MERGED)) {
            SDL_assert(filewatch_files[i].action_pending != FILEWATCH_ACTION_FILE_NONE);
            filewatch_files[i].callback(filewatch_files[i].path, filewatch_files[i].action_pending);
            filewatch_files[i].action_pending = FILEWATCH_ACTION_FILE_NONE;
            filewatch_files[i].action_processed = true;
        }
    }

    SDL_UnlockMutex(filewatcher_lock);
}