Form.Validate

Form validation.

Combinators

type alias Validation customError output = Field -> Result (Error customError) output

A validation is a function that takes a form field and returns a result being either a validation error or the expected object.

field : String -> Validation e a -> Validation e a

Access the given field in the group.

field "name" string

map : (a -> b) -> Validation e a -> Validation e b

Map over the result of the validation.

field "myfield" (string |> map String.trim)

succeed : a -> Validation e a

A validation that always succeeds. Useful for contextual validation.

andThen : (a -> Validation e b) -> Validation e a -> Validation e b

Apply a new validation to the result of the validation.

field "myfield" (int |> andThen (minInt 10))

andMap : Validation e a -> Validation e (a -> b) -> Validation e b

Incremental form validation for records with more that 8 fields.

Form.Validate.succeed SomeRecord
  |> andMap (field "foo" string)
  |> andMap (field "bar" string)

customError : e -> Error e

Helper to create a CustomError.

defaultValue : a -> Validation e a -> Validation e a

Rescue a failed validation with the supplied value.

mapError : (Error e1 -> Error e2) -> Validation e1 a -> Validation e2 a

Call Result.mapError on validation result.

withCustomError : customErr -> Validation e a -> Validation customErr a

Arrange that if a validation fails, it has the given custom error.

field "customerId" (V.int
      |> andThen (minInt 1)
      |> andThen (maxInt 9999)
      |> withCustomError InvalidIdentity)

sequence : List (Validation e a) -> Validation e (List a)

Combine a list of validations into a validation producing a list of all results.

Fixed-size forms

map2 : (a -> b -> m) -> Validation e a -> Validation e b -> Validation e m

Validation a form with two fields.

map3 : (a -> b -> c -> m) -> Validation e a -> Validation e b -> Validation e c -> Validation e m

Validation a form with three fields.

map4 : (a -> b -> c -> d -> m) -> Validation e a -> Validation e b -> Validation e c -> Validation e d -> Validation e m

Validation a form with four fields.

map5 : (a -> b -> c -> d -> e -> m) -> Validation err a -> Validation err b -> Validation err c -> Validation err d -> Validation err e -> Validation err m

Validation a form with five fields.

map6 : (a -> b -> c -> d -> e -> f -> m) -> Validation err a -> Validation err b -> Validation err c -> Validation err d -> Validation err e -> Validation err f -> Validation err m

Validation a form with six fields.

map7 : (a -> b -> c -> d -> e -> f -> g -> m) -> Validation err a -> Validation err b -> Validation err c -> Validation err d -> Validation err e -> Validation err f -> Validation err g -> Validation err m

Validation a form with seven fields.

map8 : (a -> b -> c -> d -> e -> f -> g -> h -> m) -> Validation err a -> Validation err b -> Validation err c -> Validation err d -> Validation err e -> Validation err f -> Validation err g -> Validation err h -> Validation err m

Validation a form with eight fields.

Type extractors

list : Validation e a -> Validation e (List a)

Validate a list of fields.

string : Validation e String

Validation a String.

int : Validation e Int

Validation an integer using String.toInt.

float : Validation e Float

Validation a float using String.toFloat.

bool : Validation e Bool

Validation a Bool.

date : Validation e Date

Validation a Date using Date.fromString.

maybe : Validation e a -> Validation e (Maybe a)

Transform validation result to Maybe, using Result.toMaybe.

email : Validation e String

Check if the string is a valid email address.

emptyString : Validation e String

Validate an empty string, otherwise failing with InvalidString. Useful with oneOf for optional fields with format validation.

Common filters

minInt : Int -> Int -> Validation e Int

Min value for Int.

maxInt : Int -> Int -> Validation e Int

Max value for Int.

minFloat : Float -> Float -> Validation e Float

Min value for Float.

maxFloat : Float -> Float -> Validation e Float

Max value for Float.

minLength : Int -> String -> Validation e String

Min length for String.

maxLength : Int -> String -> Validation e String

Max length for String.

nonEmpty : String -> Validation e String

Fails if String.isEmpty.

format : Regex -> String -> Validation e String

Validates format of the string.

includedIn : List String -> String -> Validation e String

Check if the string is included in the given list.

Custom validations

fail : Error e -> Validation e a

A validation that always fails. Useful for contextual validation.

succeed : a -> Validation e a

A validation that always succeeds. Useful for contextual validation.

customValidation : Validation e a -> (a -> Result (Error e) b) -> Validation e b

Custom validation for your special cases.

oneOf : List (Validation e a) -> Validation e a

First successful validation wins, from left to right.

module Form.Validate exposing (Validation, field, map, andThen, andMap, customError, defaultValue, mapError, withCustomError, map2, map3, map4, map5, map6, map7, map8, list, string, int, float, bool, date, maybe, email, emptyString, minInt, maxInt, minFloat, maxFloat, minLength, maxLength, nonEmpty, format, includedIn, fail, succeed, customValidation, oneOf, sequence)

{-| Form validation.


# Combinators

@docs Validation, field, map, succeed, andThen, andMap, customError, defaultValue, mapError, withCustomError, sequence


# Fixed-size forms

@docs map2, map3, map4, map5, map6, map7, map8


# Type extractors

@docs list, string, int, float, bool, date, maybe, email, emptyString


# Common filters

@docs minInt, maxInt, minFloat, maxFloat, minLength, maxLength, nonEmpty, format, includedIn


# Custom validations

@docs fail, succeed, customValidation, oneOf

-}

import Result
import Date exposing (Date)
import Dict exposing (Dict)
import String
import Regex exposing (Regex)
import Form.Error as Error exposing (Error, ErrorValue(..))
import Form.Field as Field exposing (Field, FieldValue(..))
import Form.Tree as Tree


{-| A validation is a function that takes a form field and returns a result
being either a validation error or the expected object.
-}
type alias Validation customError output =
    Field -> Result (Error customError) output


{-| Map over the result of the validation.

    field "myfield" (string |> map String.trim)

-}
map : (a -> b) -> Validation e a -> Validation e b
map f validation field =
    Result.map f (validation field)


{-| Apply a new validation to the result of the validation.

    field "myfield" (int |> andThen (minInt 10))

-}
andThen : (a -> Validation e b) -> Validation e a -> Validation e b
andThen callback validation field =
    validation field |> Result.andThen (\next -> (callback next) field)


{-| Incremental form validation for records with more that 8 fields.

    Form.Validate.succeed SomeRecord
      |> andMap (field "foo" string)
      |> andMap (field "bar" string)

-}
andMap : Validation e a -> Validation e (a -> b) -> Validation e b
andMap aValidation partialValidation field =
    case ( partialValidation field, aValidation field ) of
        ( Ok partial, Ok a ) ->
            Ok (partial a)

        ( partialResult, aResult ) ->
            Err (mergeMany [ errMaybe partialResult, errMaybe aResult ])


{-| Rescue a failed validation with the supplied value.
-}
defaultValue : a -> Validation e a -> Validation e a
defaultValue a validation field =
    Ok (Result.withDefault a (validation field))


{-| Call Result.mapError on validation result.
-}
mapError : (Error e1 -> Error e2) -> Validation e1 a -> Validation e2 a
mapError f validation =
    \field -> Result.mapError f (validation field)


{-| Arrange that if a validation fails, it has the given custom error.

    field "customerId" (V.int
          |> andThen (minInt 1)
          |> andThen (maxInt 9999)
          |> withCustomError InvalidIdentity)

-}
withCustomError : customErr -> Validation e a -> Validation customErr a
withCustomError =
    mapError << always << customError


{-| Helper to create a CustomError.
-}
customError : e -> Error e
customError =
    CustomError >> Error.value


{-| Access the given field in the group.

    field "name" string

-}
field : String -> Validation e a -> Validation e a
field key validation field =
    Tree.getAtName key field
        |> Maybe.withDefault (Tree.Value EmptyField)
        |> validation
        |> Result.mapError
            (\e -> Tree.group [ ( key, e ) ])


{-| Validation a form with two fields.
-}
map2 : (a -> b -> m) -> Validation e a -> Validation e b -> Validation e m
map2 func v1 v2 =
    map func v1
        |> andMap v2



-- apply (form1 func v1) v2


{-| Validation a form with three fields.
-}
map3 : (a -> b -> c -> m) -> Validation e a -> Validation e b -> Validation e c -> Validation e m
map3 func v1 v2 v3 =
    map2 func v1 v2
        |> andMap v3


{-| Validation a form with four fields.
-}
map4 : (a -> b -> c -> d -> m) -> Validation e a -> Validation e b -> Validation e c -> Validation e d -> Validation e m
map4 func v1 v2 v3 v4 =
    map3 func v1 v2 v3
        |> andMap v4


{-| Validation a form with five fields.
-}
map5 : (a -> b -> c -> d -> e -> m) -> Validation err a -> Validation err b -> Validation err c -> Validation err d -> Validation err e -> Validation err m
map5 func v1 v2 v3 v4 v5 =
    map4 func v1 v2 v3 v4
        |> andMap v5


{-| Validation a form with six fields.
-}
map6 : (a -> b -> c -> d -> e -> f -> m) -> Validation err a -> Validation err b -> Validation err c -> Validation err d -> Validation err e -> Validation err f -> Validation err m
map6 func v1 v2 v3 v4 v5 v6 =
    map5 func v1 v2 v3 v4 v5
        |> andMap v6


{-| Validation a form with seven fields.
-}
map7 : (a -> b -> c -> d -> e -> f -> g -> m) -> Validation err a -> Validation err b -> Validation err c -> Validation err d -> Validation err e -> Validation err f -> Validation err g -> Validation err m
map7 func v1 v2 v3 v4 v5 v6 v7 =
    map6 func v1 v2 v3 v4 v5 v6
        |> andMap v7


{-| Validation a form with eight fields.
-}
map8 : (a -> b -> c -> d -> e -> f -> g -> h -> m) -> Validation err a -> Validation err b -> Validation err c -> Validation err d -> Validation err e -> Validation err f -> Validation err g -> Validation err h -> Validation err m
map8 func v1 v2 v3 v4 v5 v6 v7 v8 =
    map7 func v1 v2 v3 v4 v5 v6 v7
        |> andMap v8


{-| Private
-}
mergeMany : List (Maybe (Error e)) -> Error e
mergeMany errors =
    errors
        |> List.filterMap identity
        |> List.foldl groupErrorsUnion (Tree.group [])


{-| Private
-}
groupErrorsUnion : Error e -> Error e -> Error e
groupErrorsUnion e1 e2 =
    case ( e1, e2 ) of
        ( Tree.Group g1, Tree.Group g2 ) ->
            Tree.Group (Dict.union g1 g2)

        _ ->
            e2


{-| Private
-}
errMaybe : Result e a -> Maybe e
errMaybe res =
    case res of
        Ok _ ->
            Nothing

        Err e ->
            Just e


{-| Validation an integer using `String.toInt`.
-}
int : Validation e Int
int v =
    case Field.asString v of
        Just s ->
            String.toInt s
                |> Result.mapError (\_ -> Error.value InvalidInt)

        Nothing ->
            Err (Error.value InvalidInt)


{-| Validation a float using `String.toFloat`.
-}
float : Validation e Float
float v =
    case Field.asString v of
        Just s ->
            String.toFloat s
                |> Result.mapError (\_ -> Error.value InvalidFloat)

        Nothing ->
            Err (Error.value InvalidFloat)


{-| Validation a String.
-}
string : Validation e String
string v =
    case Field.asString v of
        Just s ->
            if String.isEmpty s then
                Err (Error.value Empty)
            else
                Ok s

        Nothing ->
            Err (Error.value InvalidString)


{-| Validate an empty string, otherwise failing with InvalidString.
Useful with `oneOf` for optional fields with format validation.
-}
emptyString : Validation e String
emptyString v =
    case Field.asString v of
        Just s ->
            if String.isEmpty s then
                Ok s
            else
                Err (Error.value InvalidString)

        Nothing ->
            Ok ""


{-| Validation a Bool.
-}
bool : Validation e Bool
bool v =
    case Field.asBool v of
        Just b ->
            Ok b

        Nothing ->
            Ok False


{-| Validation a Date using `Date.fromString`.
-}
date : Validation e Date
date v =
    case Field.asString v of
        Just s ->
            Date.fromString s
                |> Result.mapError (\_ -> Error.value InvalidDate)

        Nothing ->
            Err (Error.value InvalidDate)


{-| Transform validation result to `Maybe`, using `Result.toMaybe`.
-}
maybe : Validation e a -> Validation e (Maybe a)
maybe validation field =
    Ok (Result.toMaybe (validation field))


{-| Fails if `String.isEmpty`.
-}
nonEmpty : String -> Validation e String
nonEmpty s field =
    if String.isEmpty s then
        Err (Error.value Empty)
    else
        Ok s


{-| Min length for String.
-}
minLength : Int -> String -> Validation e String
minLength min s field =
    if String.length s >= min then
        Ok s
    else
        Err (Error.value (ShorterStringThan min))


{-| Max length for String.
-}
maxLength : Int -> String -> Validation e String
maxLength max s field =
    if String.length s <= max then
        Ok s
    else
        Err (Error.value (LongerStringThan max))


{-| Min value for Int.
-}
minInt : Int -> Int -> Validation e Int
minInt min i field =
    if i >= min then
        Ok i
    else
        Err (Error.value (SmallerIntThan min))


{-| Max value for Int.
-}
maxInt : Int -> Int -> Validation e Int
maxInt max i field =
    if i <= max then
        Ok i
    else
        Err (Error.value (GreaterIntThan max))


{-| Min value for Float.
-}
minFloat : Float -> Float -> Validation e Float
minFloat min i field =
    if i >= min then
        Ok i
    else
        Err (Error.value (SmallerFloatThan min))


{-| Max value for Float.
-}
maxFloat : Float -> Float -> Validation e Float
maxFloat max i field =
    if i <= max then
        Ok i
    else
        Err (Error.value (GreaterFloatThan max))


{-| Validates format of the string.
-}
format : Regex -> String -> Validation e String
format regex s field =
    if Regex.contains regex s then
        Ok s
    else
        Err (Error.value InvalidFormat)


{-| Stolen to elm-validate.
-}
validEmailPattern : Regex
validEmailPattern =
    Regex.regex "^[a-zA-Z0-9.!#$%&'*+\\/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$"
        |> Regex.caseInsensitive


{-| Check if the string is a valid email address.
-}
email : Validation e String
email =
    string
        |> andThen
            (\s ->
                format validEmailPattern s
                    |> mapError (\_ -> Error.value InvalidEmail)
            )


{-| Check if the string is included in the given list.
-}
includedIn : List String -> String -> Validation e String
includedIn items s field =
    if List.member s items then
        Ok s
    else
        Err (Error.value NotIncludedIn)


{-| A validation that always fails. Useful for contextual validation.
-}
fail : Error e -> Validation e a
fail error field =
    Err error


{-| A validation that always succeeds. Useful for contextual validation.
-}
succeed : a -> Validation e a
succeed a field =
    Ok a


{-| Custom validation for your special cases.
-}
customValidation : Validation e a -> (a -> Result (Error e) b) -> Validation e b
customValidation validation callback field =
    validation field |> Result.andThen callback


{-| First successful validation wins, from left to right.
-}
oneOf : List (Validation e a) -> Validation e a
oneOf validations field =
    let
        results =
            List.map (\v -> v field) validations

        walkResults result combined =
            case ( combined, result ) of
                ( Ok _, _ ) ->
                    combined

                _ ->
                    result
    in
        List.foldl walkResults (Err (Error.value Empty)) results


{-| Combine a list of validations into a validation producing a list of all
results.
-}
sequence : List (Validation e a) -> Validation e (List a)
sequence validations =
    List.foldr (map2 (::)) (succeed []) validations


{-| Validate a list of fields.
-}
list : Validation e a -> Validation e (List a)
list validation field =
    case field of
        Tree.List items ->
            let
                results =
                    List.map validation items

                indexedErrMaybe index res =
                    case res of
                        Ok _ ->
                            Nothing

                        Err e ->
                            Just ( toString index, e )

                errors =
                    results
                        |> List.indexedMap indexedErrMaybe
                        |> List.filterMap identity
            in
                if List.isEmpty errors then
                    Ok (List.filterMap Result.toMaybe results)
                else
                    Err (Tree.group errors)

        _ ->
            Ok []