/******************************************************************************
 *
 *                Copyright (c) 2017-2019 by Löwenware Ltd
 *             Please, refer LICENSE file for legal information
 *
 ******************************************************************************/

/**
 * @file validate.c
 * @author Ilja Kartašov <ik@lowenware.com>
 * @brief Validation component source file
 *
 * @see https://lowenware.com/aisl/
 */

#include <ctype.h>
#include <stddef.h>
#include <stdlib.h>
#include "validate.h"


int
aislx_validate_email(const char *value)
{
	const char *at = NULL,
             *dot = NULL,
             *i  = value;
	char c;

	while ( (c = *i) != 0 ) {
		switch(c) {
		case '@':
			if (at || i == value)
				break;

			at  = i++;
			dot = NULL;
			continue;

		case '"':
		case '(':
		case ')':
		case ',':
		case ';':
		case ':':
		case '<':
		case '>':
		case '[':
		case '\\':
		case ']':
		case ' ':
			/* These characters are allowed in double quotes only, but it is not
			 * implemented in this validator, so we count them as forbidden
			 */
			break;

		case '!':
		case '#':
		case '$':
		case '%':
		case '&':
		case '\'':
		case '*':
		case '+':
		case '/':
		case '=':
		case '?':
		case '^':
		case '_':
		case '`':
		case '{':
		case '|':
		case '}':
		case '~':
			/* Allowed special local-part characters */
			if (!at) {
				i++;
				continue;
			}
			break;

		case '-':
			/* Allowed characters */
			i++;
			continue;

		case '.':
			if (dot && i == dot+1)
				break;

			if (at) {
				if (i == at+1 || *(i+1) == 0)
					break;
			} else {
				if (i == value || *(i+1) == '@')
					break;
			}

			dot = i++;
			continue;

		default:
			if ( isalnum(c) == 0 )
				continue;
			break;
		}
		return (int)(i-value)+1;
	}

	if (!at || !dot)
		return -1;

	return 0;
}