gl_gtin/validation

Validation module for GTIN codes.

Implements core validation logic for GTIN codes including format detection, check digit verification, and GTIN normalization.

Types

GtinFormat

</>

GTIN format type

pub type GtinFormat {
  Gtin8
  Gtin12
  Gtin13
  Gtin14
}

Constructors

```
Gtin8
```
```
Gtin12
```
```
Gtin13
```
```
Gtin14
```

ValidationError

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Error type for validation operations

pub type ValidationError {
  InvalidLength(got: Int)
  InvalidCheckDigit
  InvalidCharacters
  InvalidFormat
}

Constructors

```
InvalidLength(got: Int)
```
```
InvalidCheckDigit
```
```
InvalidCharacters
```
```
InvalidFormat
```

Values

normalize

</>

pub fn normalize(code: String) -> Result(String, ValidationError)

Convert a GTIN-13 to GTIN-14 format.

Prepends the indicator digit “1” and recalculates the check digit. Only works with GTIN-13 codes; other formats return an error. This is equivalent to normalize_with_indicator(code, 1).

Arguments

code - GTIN-13 string to normalize

Returns

Ok(gtin_14) if successful, Error otherwise.

Examples

normalize("6291041500213")
// -> Ok("16291041500210")

normalize("012345678905")
// -> Error(InvalidFormat)

normalize_with_indicator

</>

pub fn normalize_with_indicator(
  code: String,
  indicator: Int,
) -> Result(String, ValidationError)

Convert a GTIN-13 to GTIN-14 format using a configurable indicator digit.

Prepends the supplied indicator digit (0 through 9) to the 12 data digits of the GTIN-13 and recalculates the check digit. Leading and trailing whitespace is trimmed before validation. Only works with GTIN-13 codes; other formats return an error, and an indicator outside 0 through 9 returns Error(InvalidFormat).

Arguments

code - GTIN-13 string to normalize
indicator - Indicator digit for the GTIN-14 packaging level (0 through 9)

Returns

Ok(gtin_14) if successful, Error otherwise.

Examples

normalize_with_indicator("6291041500213", 1)
// -> Ok("16291041500210")

normalize_with_indicator("6291041500213", 2)
// -> Ok("26291041500217")

normalize_with_indicator("6291041500213", 10)
// -> Error(InvalidFormat)

to_gtin12

</>

pub fn to_gtin12(code: String) -> Result(String, ValidationError)

Convert a GTIN-14 with indicator digit 0 to its base GTIN-12 (UPC-A).

Requires a valid GTIN-14 (14 digits, correct check digit). The indicator digit (first digit) must be 0; a non-zero indicator returns Error(InvalidFormat). When the indicator is 0, the base 13-digit code (after dropping the indicator) must itself be a UPC-A padded with an implicit leading zero — that is, the second digit of the GTIN-14 must also be 0. In that case both leading zeros are dropped to yield the 12-digit UPC-A, preserving the existing check digit without recomputation. When the base code cannot be represented as a GTIN-12, Error(InvalidFormat) is returned. Leading and trailing whitespace is trimmed before validation, and the invalid-input error ordering matches validate.

Arguments

code - GTIN-14 string to down-convert

Returns

Ok(gtin_12) if the indicator digit is 0 and the base code is a UPC-A with an implicit leading zero, Error otherwise.

Examples

to_gtin12("00042100005264")
// -> Ok("042100005264")

to_gtin12("00629104150021") // base is EAN-13, not a UPC-A
// -> Error(InvalidFormat)

to_gtin13

</>

pub fn to_gtin13(code: String) -> Result(String, ValidationError)

Convert a GTIN-14 with indicator digit 0 to its base GTIN-13.

Requires a valid GTIN-14 (14 digits, correct check digit). When the leading indicator digit is 0, the leading 0 is dropped and the existing check digit is preserved without recomputation, yielding a 13-digit string. A non-zero indicator returns Error(InvalidFormat). Leading and trailing whitespace is trimmed before validation, and the invalid-input error ordering matches validate.

Arguments

code - GTIN-14 string to down-convert

Returns

Ok(gtin_13) if the indicator digit is 0, Error otherwise.

Examples

to_gtin13("06291041500213")
// -> Ok("6291041500213")

to_gtin13("16291041500210")
// -> Error(InvalidFormat)

validate

</>

pub fn validate(
  code: String,
) -> Result(GtinFormat, ValidationError)

Validate a GTIN code string.

Checks that the input is a valid GTIN (8, 12, 13, or 14 digits) with a correct check digit. Automatically trims leading and trailing whitespace before validation.

Arguments

code - GTIN string to validate

Returns

Ok(GtinFormat) if valid, Error otherwise.

Examples

validate("6291041500213")
// -> Ok(Gtin13)

validate("012345678905")
// -> Ok(Gtin12)

validate("invalid")
// -> Error(InvalidCharacters)