#include "posix.h"

#include <blue/core/random.h>
#include <blue/io/directory.h>
#include <blue/io/file.h>
#include <blue/io/path.h>
#include <blue/object/string.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <sys/stat.h>
#include <unistd.h>

struct b_file {
	struct b_object base;
	enum b_file_mode mode;
	int fd;
	struct b_path *path;
};

static void file_release(struct b_object *obj);

static struct b_object_type file_type = {
	.t_name = "corelib::file",
	.t_flags = B_OBJECT_FUNDAMENTAL,
	.t_id = B_OBJECT_TYPE_FILE,
	.t_instance_size = sizeof(struct b_file),
	.t_release = file_release,
};

static unsigned int b_mode_to_unix_mode(enum b_file_mode mode)
{
	unsigned int result = 0;

	if (mode & B_FILE_READ_WRITE) {
		result |= O_RDWR;
	} else if (mode & B_FILE_READ_ONLY) {
		result |= O_RDONLY;
	} else if (mode & B_FILE_WRITE_ONLY) {
		result |= O_WRONLY;
	} else {
		return 0;
	}

	if (mode & B_FILE_TRUNCATE) {
		result |= O_TRUNC;
	}

	if (mode & B_FILE_CREATE) {
		result |= O_CREAT;
	}

	if ((mode & B_FILE_CREATE_ONLY) == B_FILE_CREATE_ONLY) {
		result |= O_EXCL;
	}

	return result;
}

enum b_status b_file_open(
	struct b_directory *root, const struct b_path *path,
	enum b_file_mode mode, struct b_file **out)
{
	struct b_path *file_path = b_path_retain((struct b_path *)path);
	unsigned int flags = b_mode_to_unix_mode(mode);

	if (flags == 0) {
		b_path_release(file_path);
		return B_ERR_INVALID_ARGUMENT;
	}

	struct b_path *root_path = NULL;
	if (root) {
		root_path = b_path_retain(
			(struct b_path *)b_directory_get_path(root));
	} else {
		root_path = b_path_create_cwd();
	}

	const struct b_path *parts[] = {
		root_path,
		file_path,
	};

	struct b_path *abs_path
		= b_path_join(parts, sizeof parts / sizeof parts[0]);
	b_path_release(root_path);
	b_path_release(file_path);

	if (!abs_path) {
		return B_ERR_NO_MEMORY;
	}

	int fd = open(b_path_ptr(abs_path), flags, 0644);
	if (fd == -1) {
		b_path_release(abs_path);
		return b_status_from_errno(errno, B_ERR_IO_FAILURE);
	}

	struct b_file *file
		= (struct b_file *)b_object_type_instantiate(&file_type);
	if (!file) {
		close(fd);
		b_path_release(abs_path);
		return B_ERR_NO_MEMORY;
	}

	file->fd = fd;
	file->path = abs_path;
	file->mode = mode;

	*out = file;
	return B_SUCCESS;
}

static void generate_tmp_filename(char *out, size_t len)
{
	static const char *alphabet
		= "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
		  "01234567"
		  "89+=-_.";
	static const size_t alphabet_len = 67;

	b_random_ctx *ctx = b_random_global_ctx();

	for (size_t i = 0; i < len; i++) {
		int v = b_random_next_int64(ctx) % alphabet_len;
		out[i] = alphabet[v];
	}

	out[len - 1] = 0;
}

enum b_status b_file_open_temp(enum b_file_mode mode, struct b_file **out)
{
	mode |= B_FILE_DELETE_ON_CLOSE;

	char name[16];
	char path[128];

	while (1) {
		generate_tmp_filename(name, sizeof name);
		snprintf(path, sizeof path, "/tmp/%s", name);
		struct b_path *rpath = b_path_create_from_cstr(path);

		enum b_status status = b_file_open(
			B_DIRECTORY_ROOT, rpath, mode | B_FILE_CREATE_ONLY, out);

		if (status == B_ERR_NAME_EXISTS) {
			b_path_release(rpath);
			continue;
		}

		b_path_unlink(rpath);
		b_path_release(rpath);

		return status;
	}
}

enum b_status b_file_open_shadow(
	struct b_file *original, enum b_file_mode mode, struct b_file **out)
{
	mode |= B_FILE_SHADOW | B_FILE_DELETE_ON_CLOSE | B_FILE_CREATE;

	struct b_path *dir;
	b_path_get_directory(original->path, &dir);

	struct b_string *filename = b_string_create();
	b_path_get_filename(original->path, filename);

	b_string_prepend_cstr(filename, ".~");

	struct b_path *shadow_filename
		= b_path_create_from_cstr(b_string_ptr(filename));
	b_string_release(filename);

	const struct b_path *parts[] = {
		dir,
		shadow_filename,
	};

	struct b_path *shadow_filepath
		= b_path_join(parts, sizeof parts / sizeof parts[0]);
	b_path_release(dir);
	b_path_release(shadow_filename);

	if (b_path_exists(shadow_filepath)) {
		b_path_unlink(shadow_filepath);
	}

	struct b_file *shadow_file;
	enum b_status status = b_file_open(
		B_DIRECTORY_ROOT, shadow_filepath, mode, &shadow_file);
	b_path_release(shadow_filepath);

	if (!B_OK(status)) {
		return status;
	}

	*out = shadow_file;
	return B_SUCCESS;
}

enum b_status b_file_stat(struct b_file *file, struct b_file_info *out)
{
	struct stat st;
	int err = fstat(file->fd, &st);

	if (err != 0) {
		return b_status_from_errno(errno, B_ERR_IO_FAILURE);
	}

	memset(out, 0x0, sizeof *out);

	return b_file_info_from_stat(&st, out);
}

enum b_status b_file_size(struct b_file *file, size_t *out_len)
{
	off_t cur = lseek(file->fd, 0, SEEK_CUR);
	if (cur == (off_t)-1) {
		return b_status_from_errno(errno, B_ERR_IO_FAILURE);
	}

	off_t len = lseek(file->fd, 0, SEEK_END);
	if (len == (off_t)-1) {
		return b_status_from_errno(errno, B_ERR_IO_FAILURE);
	}

	cur = lseek(file->fd, cur, SEEK_SET);
	if (cur == (off_t)-1) {
		return b_status_from_errno(errno, B_ERR_IO_FAILURE);
	}

	*out_len = (size_t)len;
	return B_SUCCESS;
}

enum b_status b_file_cursor(struct b_file *file, size_t *out_pos)
{
	off_t cur = lseek(file->fd, 0, SEEK_CUR);
	if (cur == (off_t)-1) {
		return b_status_from_errno(errno, B_ERR_IO_FAILURE);
	}

	*out_pos = (size_t)cur;
	return B_SUCCESS;
}

enum b_status b_file_resize(struct b_file *file, size_t len)
{
	int err = ftruncate(file->fd, len);
	if (err == 0) {
		return B_SUCCESS;
	}

	return b_status_from_errno(errno, B_ERR_IO_FAILURE);
}

enum b_status b_file_seek(
	struct b_file *file, long long offset, enum b_seek_basis basis)
{
	int whence;
	switch (basis) {
	case B_SEEK_BEGINNING:
		whence = SEEK_SET;
		break;
	case B_SEEK_CURRENT:
		whence = SEEK_CUR;
		break;
	case B_SEEK_END:
		whence = SEEK_END;
		break;
	default:
		return B_ERR_INVALID_ARGUMENT;
	}

	int err = lseek(file->fd, offset, whence);
	if (err == 0) {
		return B_SUCCESS;
	}

	return b_status_from_errno(errno, B_ERR_IO_FAILURE);
}

enum b_status b_file_swap_shadow(struct b_file *main_file, struct b_file *shadow_file)
{
	if (main_file->mode & B_FILE_SHADOW) {
		return B_ERR_NOT_SUPPORTED;
	}

	if (!(shadow_file->mode & B_FILE_SHADOW)) {
		return B_ERR_NOT_SUPPORTED;
	}

	struct b_path *dir_path;
	b_path_get_directory(main_file->path, &dir_path);

	struct b_path *tmp_path = NULL;

	while (1) {
		char tmp_name[16];
		generate_tmp_filename(tmp_name, sizeof tmp_name);
		struct b_path *tmp_name_p = b_path_create_from_cstr(tmp_name);

		const struct b_path *parts[] = {
			dir_path,
			tmp_name_p,
		};

		tmp_path = b_path_join(parts, sizeof parts / sizeof parts[0]);

		b_path_release(tmp_name_p);

		if (!b_path_exists(tmp_path)) {
			break;
		}

		b_path_release(tmp_path);
		tmp_path = NULL;
	}

	b_path_release(dir_path);

	int err;

	err = rename(b_path_ptr(main_file->path), b_path_ptr(tmp_path));
	err = rename(b_path_ptr(shadow_file->path), b_path_ptr(main_file->path));
	err = rename(b_path_ptr(tmp_path), b_path_ptr(shadow_file->path));

	b_path_release(tmp_path);

	int fd = main_file->fd;
	main_file->fd = shadow_file->fd;
	shadow_file->fd = fd;

	return B_SUCCESS;
}

enum b_status b_file_read(
	struct b_file *file, size_t offset, size_t len, void *buf, size_t *nr_read)
{
	if (offset != B_OFFSET_CURRENT) {
		lseek(file->fd, offset, SEEK_SET);
	}

	long r = read(file->fd, buf, len);

	enum b_status status = B_SUCCESS;

	if (r < 0) {
		status = b_status_from_errno(errno, B_ERR_IO_FAILURE);
	}

	*nr_read = r;
	return status;
}

enum b_status b_file_write(
	struct b_file *file, size_t offset, size_t len, const void *buf,
	size_t *nr_written)
{
	if (offset != B_OFFSET_CURRENT) {
		lseek(file->fd, offset, SEEK_SET);
	}

	long w = write(file->fd, buf, len);

	enum b_status status = B_SUCCESS;

	if (w < 0) {
		status = b_status_from_errno(errno, B_ERR_IO_FAILURE);
	}

	*nr_written = w;
	return status;
}

static void file_release(struct b_object *obj)
{
	struct b_file *file = (struct b_file *)obj;
	close(file->fd);

	if (file->mode & B_FILE_DELETE_ON_CLOSE) {
		b_path_unlink(file->path);
	}

	b_path_release(file->path);
}