#define _GNU_SOURCE /* Definition of AT_* constants */

#include "libacl-helper.h"
#include <acl/libacl.h>
#include <stdbool.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/acl.h>

enum hakurei_acl_status hakurei_update_acl(int fd, uid_t uid, acl_perm_t perms)
{
	enum hakurei_acl_status ret;

	bool v;
	int i;
	acl_t acl, acl_d = NULL;
	acl_entry_t entry;
	acl_tag_t tag_type;
	void *qualifier_p;
	acl_permset_t permset;
	acl_perm_t has_perms;

	ret = HAKUREI_ACL_GET_FILE;
	acl = acl_get_file_at(fd, "", AT_EMPTY_PATH, ACL_TYPE_ACCESS);
	if (acl == NULL)
		goto out;

	/* prune entries by uid */
	for (i = acl_get_entry(acl, ACL_FIRST_ENTRY, &entry); i == 1;
	     i = acl_get_entry(acl, ACL_NEXT_ENTRY, &entry)) {
		ret = HAKUREI_ACL_GET_TAG_TYPE;
		if (acl_get_tag_type(entry, &tag_type) != 0)
			goto out;
		if (tag_type != ACL_USER)
			continue;

		ret = HAKUREI_ACL_GET_QUALIFIER;
		qualifier_p = acl_get_qualifier(entry);
		if (qualifier_p == NULL)
			goto out;
		v = *(uid_t *)qualifier_p == uid;
		acl_free(qualifier_p);

		if (!v)
			continue;

		ret = HAKUREI_ACL_GET_PERMSET;
		if (acl_get_permset(entry, &permset) != 0)
			goto out;

		if (perms == 0)
			goto delete;

		/* this is quite ugly, but the standard makes it impossible to
		 * directly obtain these bits */
		has_perms = 0;
#define COPY_PERM_BIT(perm)                      \
	do {                                     \
		ret = HAKUREI_ACL_GET_PERM;      \
		i = acl_get_perm(permset, perm); \
		if (i < 0)                       \
			goto out;                \
		if (i > 0)                       \
			has_perms |= perm;       \
	} while (0)
		COPY_PERM_BIT(ACL_READ);
		COPY_PERM_BIT(ACL_WRITE);
		COPY_PERM_BIT(ACL_EXECUTE);

		if (perms == has_perms) {
			ret = HAKUREI_ACL_DUP;
			acl_d = acl_dup(acl);
			if (acl_d == NULL)
				goto out;

			ret = HAKUREI_ACL_CALC_MASK;
			if (acl_calc_mask(&acl_d) != 0)
				goto out;

			ret = HAKUREI_ACL_OK;
			if (acl_cmp(acl, acl_d) == 0)
				goto out;
		}

delete:
		ret = HAKUREI_ACL_DELETE_ENTRY;
		if (acl_delete_entry(acl, entry) != 0)
			goto out;
	}

	if (perms == 0)
		goto set;

	ret = HAKUREI_ACL_CREATE_ENTRY;
	if (acl_create_entry(&acl, &entry) != 0)
		goto out;

	ret = HAKUREI_ACL_GET_PERMSET;
	if (acl_get_permset(entry, &permset) != 0)
		goto out;

	ret = HAKUREI_ACL_ADD_PERM;
	if (acl_add_perm(permset, perms) != 0)
		goto out;

	ret = HAKUREI_ACL_SET_TAG_TYPE;
	if (acl_set_tag_type(entry, ACL_USER) != 0)
		goto out;

	ret = HAKUREI_ACL_SET_QUALIFIER;
	if (acl_set_qualifier(entry, (void *)&uid) != 0)
		goto out;

set:
	ret = HAKUREI_ACL_CALC_MASK;
	if (acl_calc_mask(&acl) != 0)
		goto out;

	ret = HAKUREI_ACL_VALID;
	if (acl_valid(acl) != 0)
		goto out;

	ret = HAKUREI_ACL_SET_FILE;
	if (acl_set_file_at(fd, "", AT_EMPTY_PATH, ACL_TYPE_ACCESS, acl) == 0)
		ret = HAKUREI_ACL_OK;

out:
	if (acl != NULL)
		acl_free((void *)acl);
	if (acl_d != NULL)
		acl_free((void *)acl_d);
	return ret;
}