#include "file.h"

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

enum mode {
	MODE_R = 0x01u,
	MODE_W = 0x02u,
	MODE_A = 0x04u,
	MODE_B = 0x08u,
	MODE_X = 0x10u,
	MODE_PLUS = 0x20u,
};

static int flags_from_mode(
	const char *mode_string,
	int *out_sysflags,
	enum file_flags *out_fflags)
{
	enum mode mode = 0;
	int sysflags = 0;
	enum file_flags fflags = 0;

	for (int i = 0; mode_string[i]; i++) {
		switch (mode_string[i]) {
		case 'r':
			if (mode & (MODE_R | MODE_W | MODE_A | MODE_X)) {
				return -1;
			}

			mode |= MODE_R;
			break;
		case 'w':
			if (mode & (MODE_R | MODE_W | MODE_A)) {
				return -1;
			}
			mode |= MODE_W;
			break;
		case 'a':
			if (mode & (MODE_R | MODE_W | MODE_A | MODE_X)) {
				return -1;
			}
			break;
		case '+':
			if (mode & MODE_PLUS) {
				return -1;
			}
			mode |= MODE_PLUS;
			break;
		case 'b':
			if (mode & MODE_B) {
				return -1;
			}
			mode |= MODE_B;
			break;
		case 'x':
			if (mode & (MODE_R | MODE_A | MODE_X)) {
				return -1;
			}
			mode |= MODE_X;
			break;

		default:
			return -1;
		}
	}

	switch ((int)mode) {
	case MODE_R | MODE_B:
		fflags = FILE_BIN;
	case MODE_R:
		sysflags = O_RDONLY;
		break;

	case MODE_W | MODE_B:
		fflags = FILE_BIN;
	case MODE_W:
		sysflags = O_WRONLY | O_TRUNC | O_CREAT;
		break;

	case MODE_A | MODE_B:
		fflags = FILE_BIN;
	case MODE_A:
		sysflags = O_WRONLY | O_APPEND | O_CREAT;
		break;

	case MODE_R | MODE_PLUS | MODE_B:
		fflags = FILE_BIN;
	case MODE_R | MODE_PLUS:
		sysflags = O_RDWR;
		break;

	case MODE_W | MODE_PLUS | MODE_B:
		fflags = FILE_BIN;
	case MODE_W | MODE_PLUS:
		sysflags = O_RDWR | O_TRUNC | O_CREAT;
		break;

	case MODE_W | MODE_PLUS | MODE_X | MODE_B:
		fflags = FILE_BIN;
	case MODE_W | MODE_PLUS | MODE_X:
		sysflags = O_RDWR | O_TRUNC | O_CREAT | O_EXCL;
		break;

	case MODE_A | MODE_PLUS | MODE_B:
		fflags = FILE_BIN;
	case MODE_A | MODE_PLUS:
		sysflags = O_RDWR | O_APPEND | O_CREAT;
		break;

	default:
		return -1;
	}

	return 0;
}

struct __opaque_file *fopen(const char *path, const char *mode)
{
	int sysflags = 0;
	enum file_flags fflags = 0;
	if (flags_from_mode(mode, &sysflags, &fflags) != 0) {
		__set_errno(EINVAL);
		return NULL;
	}

	struct __opaque_file *out = malloc(sizeof *out);
	if (!out) {
		__set_errno(ENOMEM);
		return NULL;
	}

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

	int fd = open(path, sysflags);
	if (fd < 0) {
		free(out);
		__set_errno(-fd);
		return NULL;
	}

	if (fflags & FILE_BIN) {
		out->f_buffer_mode = _IOFBF;
	} else {
		out->f_buffer_mode = _IOLBF;
	}

	out->f_fd = fd;
	out->f_flags = fflags;
	__set_errno(SUCCESS);

	return out;
}