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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,73 @@ | ||
| import gleam/list | ||
| import gleam/result | ||
| import gleam/set | ||
| import gleam/string | ||
| import snag | ||
|
|
||
| /// Constraint type for verifying flag values | ||
| /// | ||
| pub type Constraint(a) = | ||
| fn(a) -> snag.Result(a) | ||
|
|
||
| /// returns a Constraint that ensures the parsed flag value is one of the allowed values. | ||
| /// | ||
| pub fn one_of(allowed: List(a)) -> Constraint(a) { | ||
| let allowed_set = set.from_list(allowed) | ||
| fn(val: a) -> snag.Result(a) { | ||
| case set.contains(allowed_set, val) { | ||
| True -> Ok(val) | ||
| False -> | ||
| snag.error( | ||
| "invalid value '" | ||
| <> string.inspect(val) | ||
| <> "', must be one of: [" | ||
| <> { | ||
| allowed | ||
| |> list.map(fn(a) { "'" <> string.inspect(a) <> "'" }) | ||
| |> string.join(", ") | ||
| } | ||
| <> "]", | ||
| ) | ||
| } | ||
| } | ||
| } | ||
|
|
||
| /// returns a Constraint that ensures the parsed flag value is not one of the disallowed values. | ||
| /// | ||
| pub fn none_of(disallowed: List(a)) -> Constraint(a) { | ||
| let disallowed_set = set.from_list(disallowed) | ||
| fn(val: a) -> snag.Result(a) { | ||
| case set.contains(disallowed_set, val) { | ||
| False -> Ok(val) | ||
| True -> | ||
| snag.error( | ||
| "invalid value '" | ||
| <> string.inspect(val) | ||
| <> "', must not be one of: [" | ||
| <> { | ||
| { | ||
| disallowed | ||
| |> list.map(fn(a) { "'" <> string.inspect(a) <> "'" }) | ||
| |> string.join(", ") | ||
| <> "]" | ||
| } | ||
| }, | ||
| ) | ||
| } | ||
| } | ||
| } | ||
|
|
||
| /// each is a convenience function for applying a Constraint(a) to a List(a). | ||
| /// This is useful because the default behaviour for constraints on lists is that they will apply to the list as a whole. | ||
| /// | ||
| /// For example, to apply one_of to all items in a `List(Int)`: | ||
| /// ```gleam | ||
| /// [1, 2, 3, 4] |> one_of |> each | ||
| /// ``` | ||
| pub fn each(constraint: Constraint(a)) -> Constraint(List(a)) { | ||
| fn(l: List(a)) -> snag.Result(List(a)) { | ||
| l | ||
| |> list.try_map(constraint) | ||
| |> result.replace(l) | ||
| } | ||
| } |
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