Validates that all elements in a list are equal to each other.

Maybe Support

This validator supports Maybe types from Prism projections:

• Nothing - Passes validation (optional fields without values)
• Just(list) - Validates the list inside the Just

This makes the validator compatible with optional fields in the validation DSL.

Optional Options

• :message - Custom error message callback (value -> String.t())
• :eq - Custom equality comparator (defaults to Funx.Eq.Protocol)

Examples

iex> Funx.Validator.AllEqual.validate([1, 1, 1], [])
%Funx.Monad.Either.Right{right: [1, 1, 1]}

iex> Funx.Validator.AllEqual.validate([1, 2, 3], [])
%Funx.Monad.Either.Left{left: %Funx.Errors.ValidationError{errors: ["must be all matching"]}}

iex> Funx.Validator.AllEqual.validate("not a list", [])
%Funx.Monad.Either.Left{left: %Funx.Errors.ValidationError{errors: ["must be a list"]}}

iex> Funx.Validator.AllEqual.validate([1, 2], [message: fn _ -> "all items must match" end])
%Funx.Monad.Either.Left{left: %Funx.Errors.ValidationError{errors: ["all items must match"]}}

Using Custom Equality

You can provide a custom equality comparator via the :eq option:

iex> case_insensitive = %{
...>   eq?: fn a, b -> String.downcase(a) == String.downcase(b) end,
...>   not_eq?: fn a, b -> String.downcase(a) != String.downcase(b) end
...> }
iex> Funx.Validator.AllEqual.validate(["HELLO", "hello", "HeLLo"], [eq: case_insensitive])
%Funx.Monad.Either.Right{right: ["HELLO", "hello", "HeLLo"]}

Maybe Examples

iex> Funx.Validator.AllEqual.validate(%Funx.Monad.Maybe.Nothing{}, [])
%Funx.Monad.Either.Right{right: %Funx.Monad.Maybe.Nothing{}}

iex> Funx.Validator.AllEqual.validate(%Funx.Monad.Maybe.Just{value: [1, 1, 1]}, [])
%Funx.Monad.Either.Right{right: [1, 1, 1]}

iex> Funx.Validator.AllEqual.validate(%Funx.Monad.Maybe.Just{value: [1, 2]}, [])
%Funx.Monad.Either.Left{left: %Funx.Errors.ValidationError{errors: ["must be all matching"]}}