Oath - Erlang term validation

Usage

Basic usage of oath:validate/3:

{error, invalid_length} = oath:validate(<<"aa">>, string, #{
    max_length => 1
}).

Validate deep terms:

Rules = [
    {<<"name">>, string, #{ min_length = 1 }},
    {<<"gender">>, string, #{
        required => true,
        max_length => 1,
        in => ["m", "f", "x"]
    }}
].

{error, Errors} = oath:validate([
    {<<"name">>, <<"Gurra">>},
    {<<"gender">>, <<"x">>}
], proplist, #{ rules => Rules }).

Concept

The basic concept is that a value is sent in alongside a type. The type
determines which validators are available. A validator is a function with
an arity of two that is invoked with the value and a configuration.

Value: the value to be validated

Types

The most commonly used fun is validate/3. It takes three arguments: a value,
a type and an optional configuration.

The value is the raw data to be validated. The type is an atom defining the
type of value to be validated (string, for example), and configuration is
specified as a map containing settings for different validators (a max length
for example).

What to configure depends on the validators available for a specific type.

String

Type: string.

Configuration:

#{
    max_length => N,
    min_length => N,

Ideas

Figure out how to coerce types
Add/replace/extend validators
Add context (protocol, credentials, host, port, path etc to url validator
for example.
Option to append or remove last slash of url
Option to add default protocol to url
New URL validator
Validate internal ip addresses

Validators

Decimal
Date
Time
DateTime
IP (4 and 6)

Coercion

<<"string">> -> "string" | <<"string">>
"string" -> "string" | <<"string">>
undefined -> undefined | "" | <<>>

binary -> binary
undefined -> undefined | <<>>

int -> int
"int" -> int
<<"int">> -> int
-> undefined | <<>> | ""

float -> float
"float" -> float
<<"float">> -> float
-> undefined | <<>> | ""

"date" -> {Date}
{Date} -> {Date}
-> undefined | <<>> | ""

[] -> []

[{}] -> [{}]

#{} -> #{}

strange/oath