mrzparser.h

#ifndef __mrzparser_h_
#define __mrzparser_h_

struct MRZ {
	char document_code[3];
	char issuing_state[4];
	char primary_identifier[46];
	char secondary_identifier[46];
	char nationality[4];
	char document_number[46];
	char date_of_birth[7];
	char sex[2];
	char date_of_expiry[7];
	const char *error;
};
typedef struct MRZ MRZ;

int parse_mrz(struct MRZ *, const char *);

#ifdef MRZ_PARSER_IMPLEMENTATION
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MRZ_CHARACTERS "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
#define MRZ_NUMBERS "0123456789"
#define MRZ_FILLER "<"
#define MRZ_SEXES "MFX" MRZ_FILLER
#define MRZ_ALL MRZ_CHARACTERS MRZ_NUMBERS MRZ_FILLER
#define MRZ_CHARACTERS_AND_NUMBERS MRZ_CHARACTERS MRZ_CHARACTERS
#define MRZ_CHARACTERS_AND_FILLER MRZ_CHARACTERS MRZ_FILLER
#define MRZ_NUMBERS_AND_FILLER MRZ_NUMBERS MRZ_FILLER
#define MRZ_CAPACITY(s) (sizeof(s) - 1)
#define MRZ_ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
#define MRZ_FILLER_SEPARATOR "<<"
#define MRZ_DOCUMENT_CODE "document code"
#define MRZ_ISSUING_STATE "issuing state"
#define MRZ_DOCUMENT_NUMBER "document number"
#define MRZ_DOCUMENT_NUMBER_CHECK_DIGIT "document number check digit"
#define MRZ_OPTIONAL_DATA1 "optional data1"
#define MRZ_DATE_OF_BIRTH "date of birth"
#define MRZ_DATE_OF_BIRTH_CHECK_DIGIT "date of birth check digit"
#define MRZ_SEX "sex"
#define MRZ_DATE_OF_EXPIRY "date of expiry"
#define MRZ_DATE_OF_EXPIRY_CHECK_DIGIT "date of expiry check digit"
#define MRZ_NATIONALITY "nationality"
#define MRZ_OPTIONAL_DATA2 "optional data2"
#define MRZ_PERSONAL_NUMBER "personal number"
#define MRZ_PERSONAL_NUMBER_CHECK_DIGIT "personal number check digit"
#define MRZ_COMBINED_CHECK_DIGIT "combined check digit"
#define MRZ_VISA "visa"
#define MRZ_NO_VISA "no visa"
#define MRZ_NOT_FRANCE "not france"
#define MRZ_DEPARTMENT_OF_ISSUANCE "department of issuance"
#define MRZ_OFFICE_OF_ISSUANCE "office of issuance"
#define MRZ_YEAR_OF_ISSUANCE "year of issuance"
#define MRZ_MONTH_OF_ISSUANCE "month of issuance"
#define MRZ_IDENTIFIERS "names"
#define MRZ_CSUM_DOCUMENT_NUMBER "checksum for document number"
#define MRZ_CSUM_DOB "checksum for date of birth"
#define MRZ_CSUM_DOE "checksum for date of expiry"
#define MRZ_CSUM_PERSONAL_NUMBER "checksum for personal number"
#define MRZ_CSUM_COMBINED "combined checksum"
#define MRZ_SWISS_LANGUAGE "invalid language code"
#define MRZ_SWISS_VERSION "invalid version"
#define MRZ_SWISS_FILLER "invalid filler characters"
#define MRZ_ASSERT_CSUM(x, m, e) if (!x && !m->error) { m->error = e; }

static int mrz_check_digit_weights[] = {7, 3, 1};
static int mrz_check(const char *digit, ...) {
	if (!digit) {
		return 0;
	}
	va_list ap;
	va_start(ap, digit);
	int sum = 0;
	int i = 0;
	for (;;) {
		const char *s = va_arg(ap, char *);
		if (!s) {
			break;
		}
		for (; *s; ++s, ++i) {
			char c = *s;
			if (c > 64 && c < 91) {
				c -= 55; // Map A-Z to 10-35.
			} else if (c > 47 && c < 58) {
				c -= 48; // Use number value.
			} else if (c == 60) {
				c = 0; // '<' is 0.
			} else {
				va_end(ap);
				return 0; // Invalid character.
			}
			sum += c * mrz_check_digit_weights[i % 3];
		}
	}
	sum %= 10;
	va_end(ap);
	return sum == (*digit == '<' ? 0 : *digit - 48);
}

static int mrz_check_extended(const char *digit, const char *s,
		const char *ext) {
	if (*digit == '<') {
		const char *p = strchr(ext, '<');
		size_t len = p - ext;
		if (p && len > 1) {
			char d[2] = {ext[--len], 0};
			// Unfortunately, Note j in ICAO 9303p5 doesn't specify
			// if the `<` shall be part of the checksum calculation
			// or not. This means some issuers include the `<` and
			// other don't so we need to accept both variants.
			char with[91] = {0};
			size_t cap_w = MRZ_CAPACITY(with);
			strncat(with, s, cap_w);
			strncat(with, MRZ_FILLER, cap_w - strlen(with));
			if (cap_w - strlen(with) < len) {
				return 0;
			}
			strncat(with, ext, len);
			char without[91] = {0};
			size_t cap_wo = MRZ_CAPACITY(without);
			strncat(without, s, cap_wo);
			if (cap_wo - strlen(without) < len) {
				return 0;
			}
			strncat(without, ext, len);
			return mrz_check(d, with, NULL) ||
					mrz_check(d, without, NULL);
		}
	}
	return mrz_check(digit, s, NULL);
}

static void mrz_rtrim(char *s) {
	char *end = s + strlen(s);
	for (; end > s && *(end - 1) == ' '; --end);
	*end = 0;
}

static void mrz_strrep(char *s, char find, char replacement) {
	char *p = s;
	while ((p = strchr(p, find))) {
		*p = replacement;
	}
}

static void mrz_parse_identifiers(MRZ *mrz, const char *identifiers) {
	const char *p = strstr(identifiers, MRZ_FILLER_SEPARATOR);
	size_t cap = MRZ_CAPACITY(mrz->primary_identifier);
	size_t len = p - identifiers;
	if (p && len < cap) {
		cap = len;
		strncpy(mrz->secondary_identifier, p + 2,
				MRZ_CAPACITY(mrz->secondary_identifier));
		mrz_strrep(mrz->secondary_identifier, '<', ' ');
		mrz_rtrim(mrz->secondary_identifier);
	}
	strncpy(mrz->primary_identifier, identifiers, cap);
	mrz_strrep(mrz->primary_identifier, '<', ' ');
	mrz_rtrim(mrz->primary_identifier);
}

static int mrz_parse_component(const char **src, size_t size, char *field,
		size_t len, const char *allowed,
		const char *description, const char **error) {
	if (!**src || size < len) {
		return 0;
	}
	int invalid = strspn(*src, allowed) < len;
	if (invalid) {
		if (!*error) {
			*error = description;
		}
		// Check premature end of input.
		if (strlen(*src) < len) {
			// Move to the end of the string to make sure all
			// subsequent calls to mrz_parse_component() will fail, too.
			for (; **src; ++*src);
			return 0;
		}
		// Otherwise take malformed component and keep parsing.
	}
	strncpy(field, *src, len);
	*src += len;
	return invalid ^ 1;
}

static int mrz_parse_td1(MRZ *mrz, const char *s) {
	mrz->error = NULL;
	const char **e = &mrz->error;
	int success = 1;

	// First line.
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->document_code), mrz->document_code,
			2, MRZ_ALL,
			MRZ_DOCUMENT_CODE, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->issuing_state), mrz->issuing_state,
			3, MRZ_CHARACTERS_AND_FILLER,
			MRZ_ISSUING_STATE, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->document_number), mrz->document_number,
			9, MRZ_ALL,
			MRZ_DOCUMENT_NUMBER, e);
	char document_number_check_digit[2] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(document_number_check_digit), document_number_check_digit,
			1, MRZ_NUMBERS_AND_FILLER,
			MRZ_DOCUMENT_NUMBER_CHECK_DIGIT, e);
	char optional_data1[16] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(optional_data1), optional_data1,
			15, MRZ_ALL,
			MRZ_OPTIONAL_DATA1, e);

	// Second line.
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->date_of_birth), mrz->date_of_birth,
			6, MRZ_NUMBERS_AND_FILLER,
			MRZ_DATE_OF_BIRTH, e);
	char date_of_birth_check_digit[2] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(date_of_birth_check_digit), date_of_birth_check_digit,
			1, MRZ_NUMBERS,
			MRZ_DATE_OF_BIRTH_CHECK_DIGIT, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->sex), mrz->sex,
			1, MRZ_SEXES,
			MRZ_SEX, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->date_of_expiry), mrz->date_of_expiry,
			6, MRZ_NUMBERS,
			MRZ_DATE_OF_EXPIRY, e);
	char date_of_expiry_check_digit[2] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(date_of_expiry_check_digit), date_of_expiry_check_digit,
			1, MRZ_NUMBERS,
			MRZ_DATE_OF_EXPIRY_CHECK_DIGIT, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->nationality), mrz->nationality,
			3, MRZ_CHARACTERS_AND_FILLER,
			MRZ_NATIONALITY, e);
	char optional_data2[12] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(optional_data2), optional_data2,
			11, MRZ_ALL,
			MRZ_OPTIONAL_DATA2, e);
	char check_digit[2] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(check_digit), check_digit,
			1, MRZ_NUMBERS,
			MRZ_COMBINED_CHECK_DIGIT, e);

	// Third line.
	char identifiers[31] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(identifiers), identifiers,
			30, MRZ_CHARACTERS_AND_FILLER,
			MRZ_IDENTIFIERS, e);
	mrz_parse_identifiers(mrz, identifiers);

	// Validate check sums.
	success &= mrz_check_extended(document_number_check_digit,
			mrz->document_number, optional_data1);
	MRZ_ASSERT_CSUM(success, mrz, MRZ_CSUM_DOCUMENT_NUMBER);
	success &= mrz_check(date_of_birth_check_digit,
			mrz->date_of_birth, NULL);
	MRZ_ASSERT_CSUM(success, mrz, MRZ_CSUM_DOB);
	success &= mrz_check(date_of_expiry_check_digit,
			mrz->date_of_expiry, NULL);
	MRZ_ASSERT_CSUM(success, mrz, MRZ_CSUM_DOE);
	success &= mrz_check(check_digit,
			mrz->document_number,
			document_number_check_digit,
			optional_data1,
			mrz->date_of_birth,
			date_of_birth_check_digit,
			mrz->date_of_expiry,
			date_of_expiry_check_digit,
			optional_data2,
			NULL);
	MRZ_ASSERT_CSUM(success, mrz, MRZ_CSUM_COMBINED);

	return success;
}

static int mrz_parse_td2(MRZ *mrz, const char *s) {
	if (*s == 'V') {
		mrz->error = MRZ_VISA;
		return 0;
	}
	mrz->error = NULL;
	const char **e = &mrz->error;
	int success = 1;

	// First line.
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->document_code), mrz->document_code,
			2, MRZ_ALL,
			MRZ_DOCUMENT_CODE, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->issuing_state), mrz->issuing_state,
			3, MRZ_CHARACTERS_AND_FILLER,
			MRZ_ISSUING_STATE, e);
	char identifiers[32] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(identifiers), identifiers,
			31, MRZ_CHARACTERS_AND_FILLER,
			MRZ_IDENTIFIERS, e);
	mrz_parse_identifiers(mrz, identifiers);

	// Second line.
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->document_number), mrz->document_number,
			9, MRZ_ALL,
			MRZ_DOCUMENT_NUMBER, e);
	char document_number_check_digit[2] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(document_number_check_digit), document_number_check_digit,
			1, MRZ_NUMBERS_AND_FILLER,
			MRZ_DOCUMENT_NUMBER_CHECK_DIGIT, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->nationality), mrz->nationality,
			3, MRZ_CHARACTERS_AND_FILLER,
			MRZ_NATIONALITY, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->date_of_birth), mrz->date_of_birth,
			6, MRZ_NUMBERS_AND_FILLER,
			MRZ_DATE_OF_BIRTH, e);
	char date_of_birth_check_digit[2] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(date_of_birth_check_digit), date_of_birth_check_digit,
			1, MRZ_NUMBERS,
			MRZ_DATE_OF_BIRTH_CHECK_DIGIT, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->sex), mrz->sex,
			1, MRZ_SEXES,
			MRZ_SEX, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->date_of_expiry), mrz->date_of_expiry,
			6, MRZ_NUMBERS,
			MRZ_DATE_OF_EXPIRY, e);
	char date_of_expiry_check_digit[2] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(date_of_expiry_check_digit), date_of_expiry_check_digit,
			1, MRZ_NUMBERS,
			MRZ_DATE_OF_EXPIRY_CHECK_DIGIT, e);
	char optional_data2[8] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(optional_data2), optional_data2,
			7, MRZ_ALL,
			MRZ_OPTIONAL_DATA2, e);
	char check_digit[2] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(check_digit), check_digit,
			1, MRZ_NUMBERS,
			MRZ_COMBINED_CHECK_DIGIT, e);

	// Validate check sums.
	success &= mrz_check_extended(document_number_check_digit,
			mrz->document_number, optional_data2);
	MRZ_ASSERT_CSUM(success, mrz, MRZ_CSUM_DOCUMENT_NUMBER);
	success &= mrz_check(date_of_birth_check_digit,
			mrz->date_of_birth, NULL);
	MRZ_ASSERT_CSUM(success, mrz, MRZ_CSUM_DOB);
	success &= mrz_check(date_of_expiry_check_digit,
			mrz->date_of_expiry, NULL);
	MRZ_ASSERT_CSUM(success, mrz, MRZ_CSUM_DOE);
	success &= mrz_check(check_digit,
			mrz->document_number,
			document_number_check_digit,
			mrz->date_of_birth,
			date_of_birth_check_digit,
			mrz->date_of_expiry,
			date_of_expiry_check_digit,
			optional_data2,
			NULL);
	MRZ_ASSERT_CSUM(success, mrz, MRZ_CSUM_COMBINED);

	return success;
}

static int mrz_parse_td3(MRZ *mrz, const char *s) {
	if (*s == 'V') {
		mrz->error = MRZ_VISA;
		return 0;
	}
	mrz->error = NULL;
	const char **e = &mrz->error;
	int success = 1;

	// First line.
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->document_code), mrz->document_code,
			2, MRZ_ALL,
			MRZ_DOCUMENT_CODE, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->issuing_state), mrz->issuing_state,
			3, MRZ_CHARACTERS_AND_FILLER,
			MRZ_ISSUING_STATE, e);
	char identifiers[40] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(identifiers), identifiers,
			39, MRZ_CHARACTERS_AND_FILLER,
			MRZ_IDENTIFIERS, e);
	mrz_parse_identifiers(mrz, identifiers);

	// Second line.
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->document_number), mrz->document_number,
			9, MRZ_ALL,
			MRZ_DOCUMENT_NUMBER, e);
	char document_number_check_digit[2] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(document_number_check_digit), document_number_check_digit,
			1, MRZ_NUMBERS_AND_FILLER,
			MRZ_DOCUMENT_NUMBER_CHECK_DIGIT, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->nationality), mrz->nationality,
			3, MRZ_CHARACTERS_AND_FILLER,
			MRZ_NATIONALITY, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->date_of_birth), mrz->date_of_birth,
			6, MRZ_NUMBERS_AND_FILLER,
			MRZ_DATE_OF_BIRTH, e);
	char date_of_birth_check_digit[2] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(date_of_birth_check_digit), date_of_birth_check_digit,
			1, MRZ_NUMBERS,
			MRZ_DATE_OF_BIRTH_CHECK_DIGIT, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->sex), mrz->sex,
			1, MRZ_SEXES,
			MRZ_SEX, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->date_of_expiry), mrz->date_of_expiry,
			6, MRZ_NUMBERS,
			MRZ_DATE_OF_EXPIRY, e);
	char date_of_expiry_check_digit[2] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(date_of_expiry_check_digit), date_of_expiry_check_digit,
			1, MRZ_NUMBERS,
			MRZ_DATE_OF_EXPIRY_CHECK_DIGIT, e);
	char personal_number[15] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(personal_number), personal_number,
			14, MRZ_ALL,
			MRZ_PERSONAL_NUMBER, e);
	char personal_number_check_digit[2] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(personal_number_check_digit), personal_number_check_digit,
			1, MRZ_NUMBERS_AND_FILLER,
			MRZ_PERSONAL_NUMBER_CHECK_DIGIT, e);
	char check_digit[2] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(check_digit), check_digit,
			1, MRZ_NUMBERS,
			MRZ_COMBINED_CHECK_DIGIT, e);

	// Validate check sums.
	success &= mrz_check(document_number_check_digit,
			mrz->document_number, NULL);
	MRZ_ASSERT_CSUM(success, mrz, MRZ_CSUM_DOCUMENT_NUMBER);
	success &= mrz_check(date_of_birth_check_digit,
			mrz->date_of_birth, NULL);
	MRZ_ASSERT_CSUM(success, mrz, MRZ_CSUM_DOB);
	success &= mrz_check(date_of_expiry_check_digit,
			mrz->date_of_expiry, NULL);
	MRZ_ASSERT_CSUM(success, mrz, MRZ_CSUM_DOE);
	success &= mrz_check(personal_number_check_digit,
			personal_number, NULL);
	MRZ_ASSERT_CSUM(success, mrz, MRZ_CSUM_PERSONAL_NUMBER);
	success &= mrz_check(check_digit,
			mrz->document_number,
			document_number_check_digit,
			mrz->date_of_birth,
			date_of_birth_check_digit,
			mrz->date_of_expiry,
			date_of_expiry_check_digit,
			personal_number,
			personal_number_check_digit,
			NULL);
	MRZ_ASSERT_CSUM(success, mrz, MRZ_CSUM_COMBINED);

	return success;
}

static int mrz_parse_mrva(MRZ *mrz, const char *s) {
	if (*s != 'V') {
		mrz->error = MRZ_NO_VISA;
		return 0;
	}
	mrz->error = NULL;
	const char **e = &mrz->error;
	int success = 1;

	// First line.
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->document_code), mrz->document_code,
			2, MRZ_ALL,
			MRZ_DOCUMENT_CODE, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->issuing_state), mrz->issuing_state,
			3, MRZ_CHARACTERS_AND_FILLER,
			MRZ_ISSUING_STATE, e);
	char identifiers[40] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(identifiers), identifiers,
			39, MRZ_CHARACTERS_AND_FILLER,
			MRZ_IDENTIFIERS, e);
	mrz_parse_identifiers(mrz, identifiers);

	// Second line.
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->document_number), mrz->document_number,
			9, MRZ_ALL,
			MRZ_DOCUMENT_NUMBER, e);
	char document_number_check_digit[2] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(document_number_check_digit), document_number_check_digit,
			1, MRZ_NUMBERS_AND_FILLER,
			MRZ_DOCUMENT_NUMBER_CHECK_DIGIT, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->nationality), mrz->nationality,
			3, MRZ_CHARACTERS_AND_FILLER,
			MRZ_NATIONALITY, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->date_of_birth), mrz->date_of_birth,
			6, MRZ_NUMBERS_AND_FILLER,
			MRZ_DATE_OF_BIRTH, e);
	char date_of_birth_check_digit[2] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(date_of_birth_check_digit), date_of_birth_check_digit,
			1, MRZ_NUMBERS,
			MRZ_DATE_OF_BIRTH_CHECK_DIGIT, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->sex), mrz->sex,
			1, MRZ_SEXES,
			MRZ_SEX, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->date_of_expiry), mrz->date_of_expiry,
			6, MRZ_NUMBERS,
			MRZ_DATE_OF_EXPIRY, e);
	char date_of_expiry_check_digit[2] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(date_of_expiry_check_digit), date_of_expiry_check_digit,
			1, MRZ_NUMBERS,
			MRZ_DATE_OF_EXPIRY_CHECK_DIGIT, e);
	char optional_data2[17] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(optional_data2), optional_data2,
			16, MRZ_ALL,
			MRZ_OPTIONAL_DATA2, e);

	// Validate check sums.
	success &= mrz_check(document_number_check_digit,
			mrz->document_number, NULL);
	MRZ_ASSERT_CSUM(success, mrz, MRZ_CSUM_DOCUMENT_NUMBER);
	success &= mrz_check(date_of_birth_check_digit,
			mrz->date_of_birth, NULL);
	MRZ_ASSERT_CSUM(success, mrz, MRZ_CSUM_DOB);
	success &= mrz_check(date_of_expiry_check_digit,
			mrz->date_of_expiry, NULL);
	MRZ_ASSERT_CSUM(success, mrz, MRZ_CSUM_DOE);

	return success;
}

static int mrz_parse_mrvb(MRZ *mrz, const char *s) {
	if (*s != 'V') {
		mrz->error = MRZ_NO_VISA;
		return 0;
	}
	mrz->error = NULL;
	const char **e = &mrz->error;
	int success = 1;

	// First line.
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->document_code), mrz->document_code,
			2, MRZ_ALL,
			MRZ_DOCUMENT_CODE, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->issuing_state), mrz->issuing_state,
			3, MRZ_CHARACTERS_AND_FILLER,
			MRZ_ISSUING_STATE, e);
	char identifiers[32] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(identifiers), identifiers,
			31, MRZ_CHARACTERS_AND_FILLER,
			MRZ_IDENTIFIERS, e);
	mrz_parse_identifiers(mrz, identifiers);

	// Second line.
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->document_number), mrz->document_number,
			9, MRZ_ALL,
			MRZ_DOCUMENT_NUMBER, e);
	char document_number_check_digit[2] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(document_number_check_digit), document_number_check_digit,
			1, MRZ_NUMBERS_AND_FILLER,
			MRZ_DOCUMENT_NUMBER_CHECK_DIGIT, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->nationality), mrz->nationality,
			3, MRZ_CHARACTERS_AND_FILLER,
			MRZ_NATIONALITY, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->date_of_birth), mrz->date_of_birth,
			6, MRZ_NUMBERS_AND_FILLER,
			MRZ_DATE_OF_BIRTH, e);
	char date_of_birth_check_digit[2] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(date_of_birth_check_digit), date_of_birth_check_digit,
			1, MRZ_NUMBERS,
			MRZ_DATE_OF_BIRTH_CHECK_DIGIT, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->sex), mrz->sex,
			1, MRZ_SEXES,
			MRZ_SEX, e);
	char date_of_expiry_check_digit[2] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->date_of_expiry), mrz->date_of_expiry,
			6, MRZ_NUMBERS,
			MRZ_DATE_OF_EXPIRY, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(date_of_expiry_check_digit), date_of_expiry_check_digit,
			1, MRZ_NUMBERS,
			MRZ_DATE_OF_EXPIRY_CHECK_DIGIT, e);
	char optional_data2[9] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(optional_data2), optional_data2,
			8, MRZ_ALL,
			MRZ_OPTIONAL_DATA2, e);

	// Validate check sums.
	success &= mrz_check(document_number_check_digit,
			mrz->document_number, NULL);
	MRZ_ASSERT_CSUM(success, mrz, MRZ_CSUM_DOCUMENT_NUMBER);
	success &= mrz_check(date_of_birth_check_digit,
			mrz->date_of_birth, NULL);
	MRZ_ASSERT_CSUM(success, mrz, MRZ_CSUM_DOB);
	success &= mrz_check(date_of_expiry_check_digit,
			mrz->date_of_expiry, NULL);
	MRZ_ASSERT_CSUM(success, mrz, MRZ_CSUM_DOE);

	return success;
}

static int mrz_parse_france(MRZ *mrz, const char *s) {
	// France got its very own MRZ on ID cards:
	// https://en.wikipedia.org/wiki/National_identity_card_(France)
	mrz->error = NULL;
	const char **e = &mrz->error;
	int success = 1;

	// First line.
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->document_code), mrz->document_code,
			2, MRZ_ALL,
			MRZ_DOCUMENT_CODE, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->nationality), mrz->nationality,
			3, MRZ_CHARACTERS_AND_FILLER,
			MRZ_NATIONALITY, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->primary_identifier), mrz->primary_identifier,
			25, MRZ_CHARACTERS_AND_FILLER,
			MRZ_IDENTIFIERS, e);
	char department_of_issuance1[4] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(department_of_issuance1), department_of_issuance1,
			3, MRZ_ALL,
			MRZ_DEPARTMENT_OF_ISSUANCE, e);
	char office_of_issuance[4] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(office_of_issuance), office_of_issuance,
			3, MRZ_NUMBERS_AND_FILLER,
			MRZ_OFFICE_OF_ISSUANCE, e);

	// Second line.
	char year_of_issuance[3] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(year_of_issuance), year_of_issuance,
			2, MRZ_NUMBERS,
			MRZ_YEAR_OF_ISSUANCE, e);
	char month_of_issuance[3] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(month_of_issuance), month_of_issuance,
			2, MRZ_NUMBERS,
			MRZ_MONTH_OF_ISSUANCE, e);
	char department_of_issuance2[4] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(department_of_issuance2), department_of_issuance2,
			3, MRZ_ALL,
			MRZ_DEPARTMENT_OF_ISSUANCE, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->document_number), mrz->document_number,
			5, MRZ_NUMBERS,
			MRZ_DOCUMENT_NUMBER, e);
	char document_number_check_digit[2] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(document_number_check_digit), document_number_check_digit,
			1, MRZ_NUMBERS,
			MRZ_DOCUMENT_NUMBER_CHECK_DIGIT, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->secondary_identifier), mrz->secondary_identifier,
			14, MRZ_CHARACTERS_AND_FILLER,
			MRZ_IDENTIFIERS, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->date_of_birth), mrz->date_of_birth,
			6, MRZ_NUMBERS_AND_FILLER,
			MRZ_DATE_OF_BIRTH, e);
	char date_of_birth_check_digit[2] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(date_of_birth_check_digit), date_of_birth_check_digit,
			1, MRZ_NUMBERS,
			MRZ_DATE_OF_BIRTH_CHECK_DIGIT, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->sex), mrz->sex,
			1, MRZ_SEXES,
			MRZ_SEX, e);
	char check_digit[2] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(check_digit), check_digit,
			1, MRZ_NUMBERS,
			MRZ_COMBINED_CHECK_DIGIT, e);

	// Validate check sums.
	success &= mrz_check(document_number_check_digit,
			year_of_issuance,
			month_of_issuance,
			department_of_issuance2,
			mrz->document_number,
			NULL);
	MRZ_ASSERT_CSUM(success, mrz, MRZ_CSUM_DOCUMENT_NUMBER);
	success &= mrz_check(date_of_birth_check_digit,
			mrz->date_of_birth, NULL);
	MRZ_ASSERT_CSUM(success, mrz, MRZ_CSUM_DOB);
	success &= mrz_check(check_digit,
			mrz->document_code,
			mrz->nationality,
			mrz->primary_identifier,
			department_of_issuance1,
			office_of_issuance,
			year_of_issuance,
			month_of_issuance,
			department_of_issuance2,
			mrz->document_number,
			document_number_check_digit,
			mrz->secondary_identifier,
			mrz->date_of_birth,
			date_of_birth_check_digit,
			mrz->sex,
			NULL);
	MRZ_ASSERT_CSUM(success, mrz, MRZ_CSUM_COMBINED);

	// Calculate expiry date.
	int year = atoi(year_of_issuance);
	// Add 10 years if the ID card was issued before 2014, but 15 if
	// it was issued in or after 2014. Unfortunately, only the last
	// two digits of a year are known, so we can't distiguish between
	// 1925 and 2025. Let's just say everything greater than 2050 is
	// a year of the past millenium.
	snprintf(mrz->date_of_expiry, sizeof(mrz->date_of_expiry), "%02d%2s01",
			(year + (year < 14 || year > 50 ? 10 : 15)) % 100,
			month_of_issuance);

	// Trim identifiers as we do this with other MRZs too. This cannot
	// be done before calculating the combined checksum, of course.
	mrz_rtrim(mrz->primary_identifier);
	mrz_rtrim(mrz->secondary_identifier);

	return success;
}

static int mrz_parse_dl_swiss(MRZ *mrz, const char *s,
		int ignore_first_line) {
	// Switzerland has something like an MRZ on its driver licenses:
	// https://www.sg.ch/content/dam/sgch/verkehr/strassenverkehr/fahreignungsabkl%C3%A4rungen/informationen/Kreisschreiben%20ASTRA%20Schweiz.%20FAK.pdf
	mrz->error = NULL;
	const char **e = &mrz->error;
	int success = 1;

	// First line, which is much shorter and contains just meta data.
	char fillers[7];
	if (!ignore_first_line) {
		char raw_card_number_alnum[4];
		success &= mrz_parse_component(&s,
				MRZ_CAPACITY(raw_card_number_alnum), raw_card_number_alnum,
				3, MRZ_CHARACTERS_AND_NUMBERS,
				MRZ_DOCUMENT_CODE, e);
		char raw_card_number_num[4];
		success &= mrz_parse_component(&s,
				MRZ_CAPACITY(raw_card_number_num), raw_card_number_num,
				3, MRZ_NUMBERS,
				MRZ_DOCUMENT_CODE, e);
		char lang[2];
		success &= mrz_parse_component(&s,
				MRZ_CAPACITY(lang), lang,
				1, MRZ_CHARACTERS,
				MRZ_DOCUMENT_CODE, e);
		if (!strchr("DFIR", *lang)) {
			*e = MRZ_SWISS_LANGUAGE;
			success = 0;
		}
		success &= mrz_parse_component(&s,
				MRZ_CAPACITY(fillers), fillers,
				2, MRZ_FILLER,
				MRZ_DOCUMENT_CODE, e);
	}

	// Second line.
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->document_code), mrz->document_code,
			2, MRZ_ALL,
			MRZ_DOCUMENT_CODE, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->issuing_state), mrz->issuing_state,
			3, "CHE",
			MRZ_ISSUING_STATE, e);
	if (strncmp("CHE", mrz->issuing_state, 3)) {
		*e = MRZ_ISSUING_STATE;
		success = 0;
	}

	// Calculate length of document number. Unfortunately, there are
	// (at least) two versions with a different length.
	const char *p = strstr(s, MRZ_FILLER_SEPARATOR);
	if (!p) {
		*e = MRZ_DOCUMENT_NUMBER;
		return 0;
	}
	int dnlen = p - s;
	int remaining;
	if (dnlen == 12) {
		dnlen = 9;
		remaining = 5;
	} else if (dnlen == 15) {
		dnlen = 12;
		remaining = 2;
	} else {
		*e = MRZ_DOCUMENT_NUMBER;
		return 0;
	}

	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->document_number), mrz->document_number,
			dnlen, MRZ_ALL,
			MRZ_DOCUMENT_NUMBER, e);
	char version[4];
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(version), version,
			3, MRZ_NUMBERS,
			MRZ_SWISS_VERSION, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(fillers), fillers,
			2, MRZ_FILLER,
			MRZ_SWISS_FILLER, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(mrz->date_of_birth), mrz->date_of_birth,
			6, MRZ_NUMBERS_AND_FILLER,
			MRZ_DATE_OF_BIRTH, e);
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(fillers), fillers,
			remaining, MRZ_FILLER,
			MRZ_SWISS_FILLER, e);

	// Third line.
	char identifiers[31] = {0};
	success &= mrz_parse_component(&s,
			MRZ_CAPACITY(identifiers), identifiers,
			30, MRZ_CHARACTERS_AND_FILLER,
			MRZ_IDENTIFIERS, e);
	mrz_parse_identifiers(mrz, identifiers);

	return success;
}

static char *mrz_purify(char *dst, const char *src, size_t len) {
	const char *end = dst + len;
	while (dst <= end) {
		src += strcspn(src, MRZ_ALL);
		size_t sl = strspn(src, MRZ_ALL);
		if (sl < 1) {
			break;
		}
		if (dst + sl > end) {
			return NULL;
		}
		strncpy(dst, src, sl);
		dst += sl;
		src += sl;
	}
	*dst = 0;
	return dst;
}

int parse_mrz(MRZ *mrz, const char *s) {
	if (!mrz || !s) {
		return 0;
	}
	memset(mrz, 0, sizeof(MRZ));
	char pure[91];
	if (!mrz_purify(pure, s, MRZ_CAPACITY(pure))) {
		return 0;
	}
	int is_visa = *pure == 'V';
	int result = -1;
	switch (strlen(pure)) {
		case 90:
			result = mrz_parse_td1(mrz, pure);
			break;
		case 60:
			result = mrz_parse_dl_swiss(mrz, pure, 1);
			break;
		case 69:
			result = mrz_parse_dl_swiss(mrz, pure, 0);
			break;
		case 72:
			result = !strncmp(pure, "IDFRA", 5)
				? mrz_parse_france(mrz, pure)
				: is_visa
				? mrz_parse_mrvb(mrz, pure)
				: mrz_parse_td2(mrz, pure);
			break;
		case 88:
			result = is_visa
				? mrz_parse_mrva(mrz, pure)
				: mrz_parse_td3(mrz, pure);
			break;
		default:
			return 0;
	}
	// Trim fillers.
	strtok(mrz->document_code, MRZ_FILLER);
	strtok(mrz->issuing_state, MRZ_FILLER);
	strtok(mrz->nationality, MRZ_FILLER);
	strtok(mrz->document_number, MRZ_FILLER);
	strtok(mrz->date_of_birth, MRZ_FILLER);
	strtok(mrz->date_of_expiry, MRZ_FILLER);
	return result;
}
#endif // MRZ_PARSER_IMPLEMENTATION

#endif