sift

-module(sift).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/sift.gleam").
-export([check/4, nested/4, ok/1, validate/1, 'and'/2, each/4, 'or'/2, 'not'/2, equals/2, check_all/4, 'when'/2, check_optional/4, check_parse/6, check_each/4, check2/5, refine/3, custom/1]).
-export_type([field_error/1]).

-if(?OTP_RELEASE >= 27).
-define(MODULEDOC(Str), -moduledoc(Str)).
-define(DOC(Str), -doc(Str)).
-else.
-define(MODULEDOC(Str), -compile([])).
-define(DOC(Str), -compile([])).
-endif.

?MODULEDOC(
    " Core validation functions — check fields, accumulate errors, compose validators.\n"
    "\n"
    " Build a validator for a struct by chaining `check` calls with `use`,\n"
    " then finish with `ok` and convert to a `Result` with `validate`. Every\n"
    " field runs, so a single call returns every error at once — not just the\n"
    " first.\n"
    "\n"
    " ```gleam\n"
    " import sift\n"
    " import sift/int as i\n"
    " import sift/string as s\n"
    "\n"
    " pub type User { User(name: String, email: String, age: Int) }\n"
    "\n"
    " pub fn validate_user(input: User) -> Result(User, List(sift.FieldError(String))) {\n"
    "   sift.validate({\n"
    "     use name <- sift.check(\"name\", input.name, s.non_empty(\"required\"))\n"
    "     use email <- sift.check(\"email\", input.email, s.email(\"invalid\"))\n"
    "     use age <- sift.check(\"age\", input.age, i.between(0, 150, \"out of range\"))\n"
    "     sift.ok(User(name:, email:, age:))\n"
    "   })\n"
    " }\n"
    " ```\n"
    "\n"
    " For nested structs use `nested`, for lists use `each`, for multiple\n"
    " constraints on one field use `check_all`, and for conditional\n"
    " constraints use `when`. See `example/contacts/` for a full walkthrough.\n"
).

-type field_error(DLN) :: {field_error, list(binary()), DLN}.

-file("src/sift.gleam", 62).
?DOC(
    " Run a validator on a field value, accumulate errors, feeds into `use`.\n"
    "\n"
    " ```gleam\n"
    " use name <- sift.check(\"name\", input.name, s.min_length(1, \"required\"))\n"
    " use email <- sift.check(\"email\", input.email, s.email(\"invalid\"))\n"
    " sift.ok(User(name:, email:))\n"
    " ```\n"
).
-spec check(
    binary(),
    DLW,
    fun((DLW) -> {ok, DLW} | {error, DLX}),
    fun((DLW) -> {DMA, list(field_error(DLX))})
) -> {DMA, list(field_error(DLX))}.
check(Field, Value, Validator, Next) ->
    case Validator(Value) of
        {ok, V} ->
            Next(V);

        {error, Msg} ->
            {Result, Errors} = Next(Value),
            {Result, [{field_error, [Field], Msg} | Errors]}
    end.

-file("src/sift.gleam", 83).
?DOC(
    " Run a sub-validator function, prefixing error paths with the field name.\n"
    "\n"
    " ```gleam\n"
    " use address <- sift.nested(\"address\", input.address, validate_address)\n"
    " // errors get paths like [\"address\", \"zip\"]\n"
    " ```\n"
).
-spec nested(
    binary(),
    DMF,
    fun((DMF) -> {DMG, list(field_error(DMH))}),
    fun((DMG) -> {DMK, list(field_error(DMH))})
) -> {DMK, list(field_error(DMH))}.
nested(Field, Value, Validator_fn, Next) ->
    {Inner_value, Inner_errors} = Validator_fn(Value),
    Prefixed_errors = gleam@list:map(
        Inner_errors,
        fun(Err) ->
            {field_error,
                [Field | erlang:element(2, Err)],
                erlang:element(3, Err)}
        end
    ),
    {Result, Outer_errors} = Next(Inner_value),
    {Result, lists:append(Prefixed_errors, Outer_errors)}.

-file("src/sift.gleam", 99).
?DOC(" Wrap a final value into a Validated tuple with no errors\n").
-spec ok(DMP) -> {DMP, list(field_error(any()))}.
ok(Value) ->
    {Value, []}.

-file("src/sift.gleam", 110).
?DOC(
    " Convert a Validated(a, e) to Result(a, List(FieldError(e))).\n"
    "\n"
    " ```gleam\n"
    " sift.ok(User(name: \"Jo\", email: \"jo@example.com\"))\n"
    " |> sift.validate\n"
    " // -> Ok(User(name: \"Jo\", email: \"jo@example.com\"))\n"
    " ```\n"
).
-spec validate({DMT, list(field_error(DMU))}) -> {ok, DMT} |
    {error, list(field_error(DMU))}.
validate(Validated) ->
    case Validated of
        {Value, []} ->
            {ok, Value};

        {_, Errors} ->
            {error, Errors}
    end.

-file("src/sift.gleam", 122).
?DOC(
    " Compose two validators — run both, accumulate errors from both.\n"
    "\n"
    " ```gleam\n"
    " let validator = s.min_length(1, \"required\") |> sift.and(s.email(\"invalid\"))\n"
    " ```\n"
).
-spec 'and'(
    fun((DNB) -> {ok, DNB} | {error, DNC}),
    fun((DNB) -> {ok, DNB} | {error, DNC})
) -> fun((DNB) -> {ok, DNB} | {error, DNC}).
'and'(V1, V2) ->
    fun(Value) -> case {V1(Value), V2(Value)} of
            {{ok, A}, {ok, _}} ->
                {ok, A};

            {{ok, _}, {error, Msg}} ->
                {error, Msg};

            {{error, Msg@1}, {ok, _}} ->
                {error, Msg@1};

            {{error, Msg@2}, _} ->
                {error, Msg@2}
        end end.

-file("src/sift.gleam", 141).
?DOC(
    " Validate every item in a list, accumulating indexed error paths.\n"
    " Produces paths like `[\"tags\", \"0\"]`, `[\"tags\", \"1\"]`, etc.\n"
    "\n"
    " ```gleam\n"
    " use tags <- sift.each(\"tags\", input.tags, s.non_empty(\"empty tag\"))\n"
    " // invalid items get paths like [\"tags\", \"2\"]\n"
    " ```\n"
).
-spec each(
    binary(),
    list(DNJ),
    fun((DNJ) -> {ok, DNJ} | {error, DNL}),
    fun((list(DNJ)) -> {DNP, list(field_error(DNL))})
) -> {DNP, list(field_error(DNL))}.
each(Field, Items, Validator, Next) ->
    Item_errors = begin
        _pipe = Items,
        _pipe@1 = gleam@list:index_map(
            _pipe,
            fun(Item, Idx) -> case Validator(Item) of
                    {ok, _} ->
                        [];

                    {error, Msg} ->
                        [{field_error,
                                [Field, erlang:integer_to_binary(Idx)],
                                Msg}]
                end end
        ),
        lists:append(_pipe@1)
    end,
    {Result, Outer_errors} = Next(Items),
    {Result, lists:append(Item_errors, Outer_errors)}.

-file("src/sift.gleam", 167).
?DOC(
    " Pass if either validator succeeds (try v1 first, then v2).\n"
    "\n"
    " ```gleam\n"
    " let validator = s.email(\"invalid\") |> sift.or(s.url(\"invalid\"))\n"
    " ```\n"
).
-spec 'or'(
    fun((DNU) -> {ok, DNU} | {error, DNV}),
    fun((DNU) -> {ok, DNU} | {error, DNV})
) -> fun((DNU) -> {ok, DNU} | {error, DNV}).
'or'(V1, V2) ->
    fun(Value) -> case V1(Value) of
            {ok, V} ->
                {ok, V};

            {error, _} ->
                V2(Value)
        end end.

-file("src/sift.gleam", 184).
?DOC(
    " Invert a validator — fail if it passes, pass if it fails.\n"
    "\n"
    " The inverted validator's own error is discarded, so its error type is\n"
    " independent of `msg`'s — pass any placeholder you like.\n"
    "\n"
    " ```gleam\n"
    " let not_admin = sift.not(s.one_of([\"admin\"], Nil), \"cannot be admin\")\n"
    " ```\n"
).
-spec 'not'(fun((DOC) -> {ok, DOC} | {error, any()}), DOG) -> fun((DOC) -> {ok,
        DOC} |
    {error, DOG}).
'not'(Validator, Msg) ->
    fun(Value) -> case Validator(Value) of
            {ok, _} ->
                {error, Msg};

            {error, _} ->
                {ok, Value}
        end end.

-file("src/sift.gleam", 200).
?DOC(
    " Value must equal the expected value.\n"
    "\n"
    " ```gleam\n"
    " let validator = sift.equals(\"yes\", \"must accept terms\")\n"
    " validator(\"yes\")  // -> Ok(\"yes\")\n"
    " validator(\"no\")   // -> Error(\"must accept terms\")\n"
    " ```\n"
).
-spec equals(DOJ, DOK) -> fun((DOJ) -> {ok, DOJ} | {error, DOK}).
equals(Expected, Msg) ->
    fun(Value) -> case Value =:= Expected of
            true ->
                {ok, Value};

            false ->
                {error, Msg}
        end end.

-file("src/sift.gleam", 219).
?DOC(
    " Run multiple validators on a field, accumulate all errors.\n"
    "\n"
    " ```gleam\n"
    " use name <- sift.check_all(\"name\", input.name, [\n"
    "   s.non_empty(\"required\"),\n"
    "   s.min_length(3, \"too short\"),\n"
    "   s.max_length(100, \"too long\"),\n"
    " ])\n"
    " sift.ok(name)\n"
    " ```\n"
).
-spec check_all(
    binary(),
    DON,
    list(fun((DON) -> {ok, DON} | {error, DOO})),
    fun((DON) -> {DOS, list(field_error(DOO))})
) -> {DOS, list(field_error(DOO))}.
check_all(Field, Value, Validators, Next) ->
    Field_errors = begin
        _pipe = Validators,
        gleam@list:filter_map(_pipe, fun(V) -> case V(Value) of
                    {ok, _} ->
                        {error, nil};

                    {error, Msg} ->
                        {ok, {field_error, [Field], Msg}}
                end end)
    end,
    {Result, Outer_errors} = Next(Value),
    {Result, lists:append(Field_errors, Outer_errors)}.

-file("src/sift.gleam", 243).
?DOC(
    " Conditional validator — runs the validator only when condition is True.\n"
    "\n"
    " ```gleam\n"
    " use state <- sift.check(\"state\", input.state,\n"
    "   sift.when(country == \"US\", s.non_empty(\"required\")))\n"
    " ```\n"
).
-spec 'when'(boolean(), fun((DOX) -> {ok, DOX} | {error, DOY})) -> fun((DOX) -> {ok,
        DOX} |
    {error, DOY}).
'when'(Condition, Validator) ->
    fun(Value) -> case Condition of
            true ->
                Validator(Value);

            false ->
                {ok, Value}
        end end.

-file("src/sift.gleam", 259).
?DOC(
    " Validate an Option value only when Some, skip when None.\n"
    "\n"
    " ```gleam\n"
    " use nickname <- sift.check_optional(\"nickname\", input.nickname,\n"
    "   s.min_length(2, \"too short\"))\n"
    " sift.ok(User(nickname:))\n"
    " ```\n"
).
-spec check_optional(
    binary(),
    gleam@option:option(DPD),
    fun((DPD) -> {ok, DPD} | {error, DPF}),
    fun((gleam@option:option(DPD)) -> {DPJ, list(field_error(DPF))})
) -> {DPJ, list(field_error(DPF))}.
check_optional(Field, Value, Validator, Next) ->
    case Value of
        none ->
            Next(none);

        {some, V} ->
            case Validator(V) of
                {ok, _} ->
                    Next({some, V});

                {error, Msg} ->
                    {Result, Errors} = Next({some, V}),
                    {Result, [{field_error, [Field], Msg} | Errors]}
            end
    end.

-file("src/sift.gleam", 288).
?DOC(
    " Parse a raw value and feed the result into the chain.\n"
    " On success, passes the parsed value to next.\n"
    " On failure, records a FieldError and passes the default to next\n"
    " so that subsequent fields still validate.\n"
    "\n"
    " ```gleam\n"
    " use age <- sift.check_parse(\"age\", \"42\", int.parse, 0, \"must be a number\")\n"
    " use age <- sift.check(\"age\", age, i.min(13, \"must be at least 13\"))\n"
    " sift.ok(age)\n"
    " ```\n"
).
-spec check_parse(
    binary(),
    DPO,
    fun((DPO) -> {ok, DPP} | {error, any()}),
    DPP,
    DPT,
    fun((DPP) -> {DPU, list(field_error(DPT))})
) -> {DPU, list(field_error(DPT))}.
check_parse(Field, Value, Parser, Default, Msg, Next) ->
    case Parser(Value) of
        {ok, Parsed} ->
            Next(Parsed);

        {error, _} ->
            {Result, Errors} = Next(Default),
            {Result, [{field_error, [Field], Msg} | Errors]}
    end.

-file("src/sift.gleam", 316).
?DOC(
    " Validate every item in a list with a sub-validator function, prefixing\n"
    " error paths with the field name and the item's index.\n"
    " Produces paths like `[\"tags\", \"0\", \"name\"]`.\n"
    "\n"
    " Use this when each item is itself a struct to validate. For a single\n"
    " `Validator(a, e)` per item, use `each` instead.\n"
    "\n"
    " ```gleam\n"
    " use tags <- sift.check_each(\"tags\", input.tags, validate_tag)\n"
    " // errors get paths like [\"tags\", \"2\", \"name\"]\n"
    " ```\n"
).
-spec check_each(
    binary(),
    list(DPZ),
    fun((DPZ) -> {DQB, list(field_error(DQC))}),
    fun((list(DQB)) -> {DQG, list(field_error(DQC))})
) -> {DQG, list(field_error(DQC))}.
check_each(Field, Values, Validator_fn, Next) ->
    {Validated_values, Item_errors} = begin
        _pipe = Values,
        _pipe@1 = gleam@list:index_map(
            _pipe,
            fun(Item, Idx) ->
                {Value, Errors} = Validator_fn(Item),
                Prefixed = gleam@list:map(
                    Errors,
                    fun(Err) ->
                        {field_error,
                            [Field,
                                erlang:integer_to_binary(Idx) |
                                erlang:element(2, Err)],
                            erlang:element(3, Err)}
                    end
                ),
                {Value, Prefixed}
            end
        ),
        gleam@list:fold(
            _pipe@1,
            {[], []},
            fun(Acc, Pair) ->
                {Values_acc, Errors_acc} = Acc,
                {Value@1, Errors@1} = Pair,
                {[Value@1 | Values_acc], lists:append(Errors_acc, Errors@1)}
            end
        )
    end,
    Validated_values@1 = lists:reverse(Validated_values),
    {Result, Outer_errors} = Next(Validated_values@1),
    {Result, lists:append(Item_errors, Outer_errors)}.

-file("src/sift.gleam", 358).
?DOC(
    " Cross-field validator comparing two already-validated values.\n"
    " On success, passes the (possibly transformed) first value to next.\n"
    " On failure, records a FieldError under `field` and passes `a` through\n"
    " so subsequent checks still run.\n"
    "\n"
    " ```gleam\n"
    " use name <- sift.check(\"name\", input.name, s.non_empty(\"required\"))\n"
    " use confirm <- sift.check(\"confirm\", input.confirm, s.non_empty(\"required\"))\n"
    " use name <- sift.check2(\"confirm\", name, confirm, fn(a, b) {\n"
    "   case a == b { True -> Ok(a) False -> Error(\"must match name\") }\n"
    " })\n"
    " sift.ok(name)\n"
    " ```\n"
).
-spec check2(
    binary(),
    DQL,
    DQM,
    fun((DQL, DQM) -> {ok, DQL} | {error, DQN}),
    fun((DQL) -> {DQQ, list(field_error(DQN))})
) -> {DQQ, list(field_error(DQN))}.
check2(Field, A, B, Validator, Next) ->
    case Validator(A, B) of
        {ok, V} ->
            Next(V);

        {error, Msg} ->
            {Result, Errors} = Next(A),
            {Result, [{field_error, [Field], Msg} | Errors]}
    end.

-file("src/sift.gleam", 388).
?DOC(
    " Post-assembly whole-object check. Runs on a `Validated(a, e)` produced by\n"
    " `ok(...)`, useful for cross-field constraints expressed in terms of the\n"
    " final struct.\n"
    "\n"
    " ```gleam\n"
    " sift.ok(Registration(role:, mfa:))\n"
    " |> sift.refine(\"mfa\", fn(r) {\n"
    "   case r.role == \"admin\" && r.mfa == None {\n"
    "     True -> Error(\"required for admins\")\n"
    "     False -> Ok(r)\n"
    "   }\n"
    " })\n"
    " |> sift.validate\n"
    " ```\n"
).
-spec refine(
    {DQV, list(field_error(DQW))},
    binary(),
    fun((DQV) -> {ok, DQV} | {error, DQW})
) -> {DQV, list(field_error(DQW))}.
refine(Validated, Field, Check) ->
    {Value, Errors} = Validated,
    case Check(Value) of
        {ok, V} ->
            {V, Errors};

        {error, Msg} ->
            {Value, lists:append(Errors, [{field_error, [Field], Msg}])}
    end.

-file("src/sift.gleam", 415).
?DOC(
    " Escape hatch for user-defined checks.\n"
    "\n"
    " ```gleam\n"
    " let even = sift.custom(fn(n: Int) {\n"
    "   case n % 2 == 0 {\n"
    "     True -> Ok(n)\n"
    "     False -> Error(\"must be even\")\n"
    "   }\n"
    " })\n"
    " even(4)  // -> Ok(4)\n"
    " even(3)  // -> Error(\"must be even\")\n"
    " ```\n"
).
-spec custom(fun((DRD) -> {ok, DRD} | {error, DRE})) -> fun((DRD) -> {ok, DRD} |
    {error, DRE}).
custom(F) ->
    F.