/******************************************************************************
 *
 *                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 "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;
				}
				else
					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;
}