#include <hashtbl.h>
#include <mutex.h>
#include <string.h>
#include <debug.h>

#include <nullfs.h>

// nullfs driver
static bool nullfs_fs_make(fs_handle_t *source, const char* opts, fs_t *d);

// nullfs fs_t
static void nullfs_fs_shutdown(fs_ptr fs);

// nullfs directory node
static bool nullfs_d_open(fs_node_ptr n, int mode);
static bool nullfs_d_stat(fs_node_ptr n, stat_t *st);
static bool nullfs_d_walk(fs_node_ptr n, const char* file, struct fs_node *node_d);
static bool nullfs_d_delete(fs_node_ptr n, const char* file);
static bool nullfs_d_move(fs_node_ptr n, const char* old_name, fs_node_t *new_parent, const char *new_name);
static bool nullfs_d_create(fs_node_ptr n, const char* file, int type);
static void nullfs_d_dispose(fs_node_ptr n);
static bool nullfs_d_readdir(fs_handle_t *f, size_t ent_no, dirent_t *d);
static void nullfs_d_close(fs_handle_t *f);

// nullfs ram file node
static bool nullfs_f_open(fs_node_ptr n, int mode);
static bool nullfs_f_stat(fs_node_ptr n, stat_t *st);
static void nullfs_f_dispose(fs_node_ptr n);
static size_t nullfs_f_read(fs_handle_t *f, size_t offset, size_t len, char* buf);
static size_t nullfs_f_write(fs_handle_t *f, size_t offset, size_t len, const char* buf);
static void nullfs_f_close(fs_handle_t *f);

// VTables that go with it
static fs_driver_ops_t nullfs_driver_ops = {
	.make = nullfs_fs_make,
};

static fs_ops_t nullfs_ops = {
	.shutdown = nullfs_fs_shutdown,
	.add_source = 0,
};

static fs_node_ops_t nullfs_d_ops = {
	.open = nullfs_d_open,
	.stat = nullfs_d_stat,
	.walk = nullfs_d_walk,
	.delete = nullfs_d_delete,
	.move = nullfs_d_move,
	.create = nullfs_d_create,
	.dispose = nullfs_d_dispose,
	.readdir = nullfs_d_readdir,
	.close = nullfs_d_close,
	.read = 0,
	.write = 0,
	.ioctl = 0,
	.poll = 0,
};

static fs_node_ops_t nullfs_f_ops = {
	.open = nullfs_f_open,
	.stat = nullfs_f_stat,
	.dispose = nullfs_f_dispose,
	.walk = 0,
	.create = 0,
	.delete = 0,
	.move = 0,
	.read = nullfs_f_read,
	.write = nullfs_f_write,
	.close = nullfs_f_close,
	.readdir = 0,
	.ioctl =0,
	.poll = 0,
};


// ====================== //
// NULLFS DATA STRUCTURES //
// ====================== //

typedef struct {
	bool can_create, can_move, can_delete;
} nullfs_t;

typedef struct nullfs_item {
	char* name;
	fs_node_ptr data;
	fs_node_ops_t *ops;

	struct nullfs_item *next;
} nullfs_item_t;

typedef struct {
	nullfs_item_t *items_list;
	hashtbl_t *items_idx;

	mutex_t lock;

	nullfs_t *fs;

	fs_node_t *vfs_node;
} nullfs_dir_t;

typedef struct {
	char* data;
	size_t size;
	bool own_data;
	int ok_modes;
	
	mutex_t lock;		// locked on open

	fs_node_t *vfs_node;
} nullfs_file_t;

// No nullfs_file_handle_t struct, we don't need it. The handle's data
// pointer is simply a pointer to the file node.

// ===================== //
// NULLFS IMPLEMENTATION //
// ===================== //

void register_nullfs_driver() {
	register_fs_driver("nullfs", &nullfs_driver_ops);
}

bool nullfs_fs_make(fs_handle_t *source, const char* opts, fs_t *fs_s) {
	if (source != 0) return false;

	nullfs_t *fs = (nullfs_t*)malloc(sizeof(nullfs_t));
	if (fs == 0) return false;

	fs->can_create = (strchr(opts, 'c') != 0);
	fs->can_move = (strchr(opts, 'm') != 0);
	fs->can_delete = (strchr(opts, 'd') != 0);

	nullfs_dir_t *root = (nullfs_dir_t*)malloc(sizeof(nullfs_dir_t));
	if (root == 0) {
		free(fs);
		return false;
	}

	root->fs = fs;
	root->items_list = 0;
	root->lock = MUTEX_UNLOCKED;
	root->items_idx = create_hashtbl(str_key_eq_fun, str_hash_fun, 0);
	if (root->items_idx == 0) {
		free(root);
		free(fs);
		return false;
	}

	fs_s->ops = &nullfs_ops;
	fs_s->data = fs;
	fs_s->root->ops = &nullfs_d_ops;
	fs_s->root->data = root;

	return true;
}

void nullfs_fs_shutdown(fs_ptr fs) {
	dbg_printf("Not implemented: nullfs_fs_shutdown. Memory is leaking.\n");
	// TODO free all
}

bool nullfs_add_node(fs_t *fs, const char* name, fs_node_ptr data, fs_node_ops_t *ops) {
	char file_name[DIR_MAX];

	fs_node_t *n = fs_walk_path_except_last(fs->root, name, file_name);
	if (n == 0) return false;
	if (n->ops != &nullfs_d_ops) return false;

	nullfs_dir_t *d = (nullfs_dir_t*)n->data;
	mutex_lock(&d->lock);

	nullfs_item_t *i = (nullfs_item_t*)malloc(sizeof(nullfs_item_t));
	if (i == 0) goto error;
	
	i->name = strdup(file_name);
	if (i->name == 0) goto error;

	i->data = data;
	i->ops = ops;

	bool add_ok = hashtbl_add(d->items_idx, i->name, i);
	if (!add_ok) goto error;

	i->next = d->items_list;
	d->items_list = i;

	mutex_unlock(&d->lock);
	return true;

error:
	if (i && i->name) free(i->name);
	if (i) free(i);
	mutex_unlock(&d->lock);
	return false;
}

bool nullfs_add_ram_file(fs_t *fs, const char* name, char* data, size_t init_sz, bool copy, int ok_modes) {
	nullfs_file_t *f = (nullfs_file_t*)malloc(sizeof(nullfs_file_t));
	if (f == 0) return false;

	f->size = init_sz;
	if (copy) {
		f->data = malloc(init_sz);
		memcpy(f->data, data, init_sz);
		f->own_data = true;
	} else {
		f->data = data;
		f->own_data = false;
	}
	f->ok_modes = ok_modes &
		(FM_TRUNC | FM_READ | FM_WRITE);	// no MMAP support
	f->lock = MUTEX_UNLOCKED;

	bool add_ok = nullfs_add_node(fs, name, f, &nullfs_f_ops);
	if (!add_ok) {
		if (f->own_data) free(f->data);
		free(f);
		return false;
	}

	return true;
}

//   -- Directory node --

bool nullfs_d_open(fs_node_ptr n, int mode) {
	if (mode != FM_READDIR) return false;

	return true;
}

bool nullfs_d_stat(fs_node_ptr n, stat_t *st) {
	nullfs_dir_t* d = (nullfs_dir_t*)n;

	mutex_lock(&d->lock);

	st->type = FT_DIR;
	st->access = FM_READDIR
		| (d->fs->can_create ? FM_DCREATE : 0)
		| (d->fs->can_move ? FM_DMOVE : 0)
		| (d->fs->can_delete ? FM_DDELETE : 0);

	st->size = hashtbl_count(d->items_idx);

	mutex_unlock(&d->lock);

	return true;
}

bool nullfs_d_walk(fs_node_ptr n, const char* file, struct fs_node *node_d) {
	nullfs_dir_t* d = (nullfs_dir_t*)n;

	mutex_lock(&d->lock);

	nullfs_item_t* x = (nullfs_item_t*)hashtbl_find(d->items_idx, file);
	if (x == 0) {
		mutex_unlock(&d->lock);
		return false;
	}

	node_d->ops = x->ops;
	node_d->data = x->data;

	mutex_unlock(&d->lock);

	return true;
}

bool nullfs_d_delete(fs_node_ptr n, const char* file) {
	nullfs_dir_t* d = (nullfs_dir_t*)n;

	mutex_lock(&d->lock);

	if (!d->fs->can_delete) goto error;

	nullfs_item_t *i = hashtbl_find(d->items_idx, file);
	if (i == 0) goto error;

	if (i->ops == &nullfs_d_ops) {
		// if it is a subdirectory, check it is empty
		nullfs_dir_t* sd = (nullfs_dir_t*)i->data;
		if (!mutex_try_lock(&sd->lock)) goto error;	// in use
		if (sd->items_list != 0) goto error;		// cannot delete non-empty directory

		delete_hashtbl(sd->items_idx);
		free(sd);
	} else if (i->ops == &nullfs_f_ops) {
		nullfs_file_t* f = (nullfs_file_t*)i->data;
		if (!mutex_try_lock(&f->lock)) goto error;	// in use

		if (f->own_data) free(f->data);
		free(f);
	} else {
		goto error;		// special nodes (devices, ...) may not be deleted
	}

	hashtbl_remove(d->items_idx, i->name);

	if (d->items_list == i) {
		d->items_list = i->next;
	} else {
		for (nullfs_item_t* it = d->items_list; it != 0; it++) {
			if (it->next == i) {
				it->next = i->next;
				break;
			}
		}
	}

	free(i->name);
	free(i);
	mutex_unlock(&d->lock);
	return true;

error:
	mutex_unlock(&d->lock);
	return false;
}

bool nullfs_d_move(fs_node_ptr n, const char* old_name, fs_node_t *new_parent, const char *new_name) {
	dbg_printf("Not implemented: move in nullfs. Failing potentially valid move request.\n");

	return false; //TODO
}

bool nullfs_d_create(fs_node_ptr n, const char* file, int type) {
	nullfs_dir_t *d = (nullfs_dir_t*)n;
	nullfs_item_t *i = 0;

	if (type == FT_REGULAR) {
		mutex_lock(&d->lock);

		nullfs_file_t *f = (nullfs_file_t*)malloc(sizeof(nullfs_file_t));
		if (f == 0) goto f_error;

		f->ok_modes = FM_READ | FM_WRITE | FM_TRUNC | FM_APPEND;
		f->data = 0;
		f->size = 0;
		f->own_data = false;
		f->lock = MUTEX_UNLOCKED;

		i = (nullfs_item_t*)malloc(sizeof(nullfs_item_t));
		if (i == 0) goto f_error;

		i->name = strdup(file);
		if (i->name == 0) goto f_error;

		i->ops = &nullfs_f_ops;
		i->data = f;

		bool add_ok = hashtbl_add(d->items_idx, i->name, i);
		if (!add_ok) goto f_error;

		i->next = d->items_list;
		d->items_list = i;

		mutex_unlock(&d->lock);
		return true;

	f_error:
		if (i != 0 && i->name != 0) free(i->name);
		if (i != 0) free(i);
		if (f != 0) free(f);
		mutex_unlock(&d->lock);
		return false;
	} else if (type == FT_DIR) {
		mutex_lock(&d->lock);

		nullfs_dir_t *x = (nullfs_dir_t*)malloc(sizeof(nullfs_dir_t));
		if (x == 0) goto d_error;

		x->items_idx = create_hashtbl(str_key_eq_fun, str_hash_fun, 0);
		if (x->items_idx == 0) goto d_error;

		x->items_list = 0;
		x->lock = MUTEX_UNLOCKED;
		x->fs = d->fs;

		i = (nullfs_item_t*)malloc(sizeof(nullfs_item_t));
		if (i == 0) goto d_error;

		i->name = strdup(file);
		if (i->name == 0) goto d_error;

		i->ops = &nullfs_d_ops;
		i->data = x;

		bool add_ok = hashtbl_add(d->items_idx, i->name, i);
		if (!add_ok) goto d_error;

		i->next = d->items_list;
		d->items_list = i;

		mutex_unlock(&d->lock);
		return true;

	d_error:
		if (i != 0 && i->name != 0) free(i->name);
		if (i != 0) free(i);
		if (x != 0 && x->items_idx != 0) delete_hashtbl(x->items_idx);
		if (x != 0) free(x);
		mutex_unlock(&d->lock);
		return false;
	} else {
		return false;
	}
}

void nullfs_d_dispose(fs_node_ptr n) {
	// nothing to do
}

bool nullfs_d_readdir(fs_handle_t *f, size_t ent_no, dirent_t *d) {
	// Very nonefficient !!

	nullfs_dir_t *h = (nullfs_dir_t*)f->data;

	mutex_lock(&h->lock);

	bool ok = false;
	size_t idx = 0;
	for (nullfs_item_t *i = h->items_list; i != 0; i = i->next) {
		if (idx == ent_no) {
			ok = true;

			strncpy(d->name, i->name, DIR_MAX);
			d->name[DIR_MAX-1] = 0;
			if (i->ops->stat) {
				i->ops->stat(i->data, &d->st);
			} else {
				// no stat operation : should we do something else ?
				memset(&d->st, 0, sizeof(stat_t));
			}

			break;
		}
		idx++;
	}

	mutex_unlock(&h->lock);

	return ok;
}

void nullfs_d_close(fs_handle_t *f) {
	// Nothing to do
}

//   -- File node --

bool nullfs_f_open(fs_node_ptr n, int mode) {
	nullfs_file_t *f = (nullfs_file_t*)n;

	if (mode & ~f->ok_modes) return false;

	if (mode & FM_TRUNC) {
		// truncate file
		mutex_lock(&f->lock);

		if (f->own_data) free(f->data);
		f->size = 0;
		f->own_data = false;
		f->data = 0;

		mutex_unlock(&f->lock);
	}

	return true;
}

bool nullfs_f_stat(fs_node_ptr n, stat_t *st) {
	nullfs_file_t *f = (nullfs_file_t*)n;
	mutex_lock(&f->lock);

	st->type = FT_REGULAR;
	st->access = f->ok_modes;
	st->size = f->size;

	mutex_unlock(&f->lock);
	return true;
}

void nullfs_f_dispose(fs_node_ptr n) {
	// nothing to do
}

//   -- File handle --

static size_t nullfs_f_read(fs_handle_t *h, size_t offset, size_t len, char* buf) {
	nullfs_file_t *f = (nullfs_file_t*)h->data;
	mutex_lock(&f->lock);

	size_t ret = 0;
	
	if (offset >= f->size) goto end_read;
	if (offset + len > f->size) len = f->size - offset;

	memcpy(buf, f->data + offset, len);
	ret = len;

end_read:
	mutex_unlock(&f->lock);
	return ret;
}

static size_t nullfs_f_write(fs_handle_t *h, size_t offset, size_t len, const char* buf) {
	nullfs_file_t *f = (nullfs_file_t*)h->data;
	mutex_lock(&f->lock);

	size_t ret = 0;

	if (offset + len > f->size) {
		// resize buffer (zero out new portion)
		void* new_buffer = malloc(offset + len);
		if (new_buffer == 0) goto end_write;

		memcpy(new_buffer, f->data, f->size);
		if (offset > f->size)
			memset(new_buffer + f->size, 0, offset - f->size);

		if (f->own_data) free(f->data);
		f->data = new_buffer;
		f->own_data = true;
		f->size = offset + len;
	}

	memcpy(f->data + offset, buf, len);
	ret = len;

end_write:
	mutex_unlock(&f->lock);
	return ret;
}

static void nullfs_f_close(fs_handle_t *h) {
	// nothing to do
}

/* vim: set ts=4 sw=4 tw=0 noet :*/