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hydra-0.15.0: src/main/haskell/Hydra/Sources/Json/Decode.hs

module Hydra.Sources.Json.Decode where

-- Standard imports for term-level sources outside of the kernel
import Hydra.Kernel
import Hydra.Sources.Libraries
import           Hydra.Dsl.Meta.Lib.Strings                as Strings
import           Hydra.Dsl.Meta.Phantoms                   as Phantoms
import qualified Hydra.Dsl.Annotations                     as Annotations
import qualified Hydra.Dsl.Bootstrap                       as Bootstrap
import qualified Hydra.Dsl.LiteralTypes                    as LiteralTypes
import qualified Hydra.Dsl.Literals                        as Literals
import qualified Hydra.Dsl.Paths                  as Paths
import qualified Hydra.Dsl.Ast                        as Ast
import qualified Hydra.Dsl.Meta.Base                       as MetaBase
import qualified Hydra.Dsl.Coders                     as Coders
import qualified Hydra.Dsl.Util                    as Util
import qualified Hydra.Dsl.Meta.Core                       as Core
import qualified Hydra.Dsl.Meta.Graph                      as Graph
import qualified Hydra.Dsl.Json.Model                       as Json
import qualified Hydra.Dsl.Meta.Lib.Chars                  as Chars
import qualified Hydra.Dsl.Meta.Lib.Eithers                as Eithers
import qualified Hydra.Dsl.Meta.Lib.Equality               as Equality
import qualified Hydra.Dsl.Meta.Lib.Lists                  as Lists
import qualified Hydra.Dsl.Meta.Lib.Literals               as Literals
import qualified Hydra.Dsl.Meta.Lib.Logic                  as Logic
import qualified Hydra.Dsl.Meta.Lib.Maps                   as Maps
import qualified Hydra.Dsl.Meta.Lib.Math                   as Math
import qualified Hydra.Dsl.Meta.Lib.Maybes                 as Maybes
import qualified Hydra.Dsl.Meta.Lib.Pairs                  as Pairs
import qualified Hydra.Dsl.Meta.Lib.Sets                   as Sets
import qualified Hydra.Dsl.Packaging                     as Packaging
import qualified Hydra.Dsl.Meta.Terms                      as MetaTerms
import qualified Hydra.Dsl.Meta.Testing                    as Testing
import qualified Hydra.Dsl.Topology                   as Topology
import qualified Hydra.Dsl.Meta.Types                      as MetaTypes
import qualified Hydra.Dsl.Typing                     as Typing
import qualified Hydra.Dsl.Util                       as Util
import qualified Hydra.Dsl.Meta.Variants                   as Variants
import qualified Hydra.Dsl.Prims                           as Prims
import qualified Hydra.Dsl.Meta.Tabular                         as Tabular
import qualified Hydra.Dsl.Terms                           as Terms
import qualified Hydra.Dsl.Tests                           as Tests
import qualified Hydra.Dsl.Types                           as Types
import qualified Hydra.Sources.Decode.Core                 as DecodeCore
import qualified Hydra.Sources.Encode.Core                 as EncodeCore
import qualified Hydra.Sources.Kernel.Terms.Adapt           as Adapt
--import qualified Hydra.Sources.Kernel.Terms.All            as KernelTerms
import qualified Hydra.Sources.Kernel.Terms.Annotations    as Annotations
import qualified Hydra.Sources.Kernel.Terms.Arity          as Arity
import qualified Hydra.Sources.Kernel.Terms.Checking       as Checking
import qualified Hydra.Sources.Kernel.Terms.Constants      as Constants
import qualified Hydra.Sources.Kernel.Terms.Extract.Core   as ExtractCore
import qualified Hydra.Sources.Kernel.Terms.Extract.Util   as ExtractUtil
import qualified Hydra.Sources.Kernel.Terms.Formatting     as Formatting
import qualified Hydra.Sources.Kernel.Terms.Inference      as Inference
import qualified Hydra.Sources.Kernel.Terms.Languages      as Languages
import qualified Hydra.Sources.Kernel.Terms.Lexical        as Lexical
import qualified Hydra.Sources.Kernel.Terms.Literals       as Literals
import qualified Hydra.Sources.Kernel.Terms.Names          as Names
import qualified Hydra.Sources.Kernel.Terms.Reduction      as Reduction
import qualified Hydra.Sources.Kernel.Terms.Reflect        as Reflect
import qualified Hydra.Sources.Kernel.Terms.Strip          as Strip
import qualified Hydra.Sources.Kernel.Terms.Serialization  as Serialization
import qualified Hydra.Sources.Kernel.Terms.Show.Paths as ShowPaths
import qualified Hydra.Sources.Kernel.Terms.Show.Core      as ShowCore
import qualified Hydra.Sources.Kernel.Terms.Show.Graph     as ShowGraph
import qualified Hydra.Sources.Kernel.Terms.Show.Variants      as ShowVariants
import qualified Hydra.Sources.Kernel.Terms.Show.Typing    as ShowTyping
import qualified Hydra.Sources.Kernel.Terms.Sorting        as Sorting
import qualified Hydra.Sources.Kernel.Terms.Substitution   as Substitution
import qualified Hydra.Sources.Kernel.Terms.Templates      as Templates
import qualified Hydra.Sources.Kernel.Terms.Unification    as Unification
import qualified Hydra.Sources.Kernel.Types.All            as KernelTypes
import           Prelude hiding ((++), decodeFloat)
import qualified Data.Int                                  as I
import qualified Data.List                                 as L
import qualified Data.Map                                  as M
import qualified Data.Scientific                           as Sci
import qualified Data.Set                                  as S
import qualified Data.Maybe                                as Y

-- Additional imports
import Hydra.Json.Model


ns :: Namespace
ns = Namespace "hydra.json.decode"

define :: String -> TTerm a -> TTermDefinition a
define = definitionInNamespace ns

module_ :: Module
module_ = Module {
            moduleNamespace = ns,
            moduleDefinitions = definitions,
            moduleTermDependencies = [Strip.ns, moduleNamespace Literals.module_, moduleNamespace ExtractCore.module_],
            moduleTypeDependencies = KernelTypes.kernelTypesNamespaces,
            moduleDescription = Just "JSON decoding for Hydra terms. Converts JSON Values to Terms using Either for error handling."}
  where
    definitions = [
      toDefinition fromJson,
      toDefinition decodeLiteral,
      toDefinition decodeFloat,
      toDefinition decodeInteger,
      toDefinition parseSpecialFloat,
      toDefinition parseSpecialFloat32,
      toDefinition expectString,
      toDefinition expectArray,
      toDefinition expectObject,
      toDefinition expectNumber]

-- | Decode a JSON Value to a Term given a Type and type lookup table.
-- Returns Left with an error message for type mismatches or invalid JSON.
fromJson :: TTermDefinition (M.Map Name Type -> Name -> Type -> Value -> Either String Term)
fromJson = define "fromJson" $
  doc "Decode a JSON value to a Hydra term given a type and type name. Returns Left for type mismatches." $
  "types" ~> "tname" ~> "typ" ~> "value" ~>
  "stripped" <~ (Strip.deannotateType @@ var "typ") $
  cases _Type (var "stripped")
    (Just $ left $ Strings.cat $ list [
      string "unsupported type for JSON decoding: ",
      ShowCore.type_ @@ var "typ"]) [

    -- Literals
    _Type_literal>>: "lt" ~> decodeLiteral @@ var "lt" @@ var "value",

    -- Lists
    _Type_list>>: "elemType" ~>
      "decodeElem" <~ ("v" ~> fromJson @@ var "types" @@ var "tname" @@ var "elemType" @@ var "v") $
      "arrResult" <~ (expectArray @@ var "value") $
      Eithers.either_
        ("err" ~> left $ var "err")
        ("arr" ~>
          "decoded" <~ (Eithers.mapList (var "decodeElem") (var "arr")) $
          Eithers.map ("ts" ~> Core.termList $ var "ts") (var "decoded"))
        (var "arrResult"),

    -- Sets
    _Type_set>>: "elemType" ~>
      "decodeElem" <~ ("v" ~> fromJson @@ var "types" @@ var "tname" @@ var "elemType" @@ var "v") $
      "arrResult" <~ (expectArray @@ var "value") $
      Eithers.either_
        ("err" ~> left $ var "err")
        ("arr" ~>
          "decoded" <~ (Eithers.mapList (var "decodeElem") (var "arr")) $
          Eithers.map ("elems" ~> Core.termSet $ Sets.fromList $ var "elems") (var "decoded"))
        (var "arrResult"),

    -- Maybe: decoding depends on whether the inner type is itself Maybe
    --   Simple Maybe(T): null -> Nothing, any other value -> Just (decoded as T)
    --   Nested Maybe(Maybe(T)): null -> Nothing, [v] -> Just v (array-wrapped)
    _Type_maybe>>: "innerType" ~>
      "innerStripped" <~ (Strip.deannotateType @@ var "innerType") $
      "isNestedMaybe" <~ (cases _Type (var "innerStripped") (Just false) [
        _Type_maybe>>: constant true]) $
      Logic.ifElse (var "isNestedMaybe")
        -- Nested Maybe: use array-wrapped encoding (null -> Nothing, [v] -> Just v)
        ("decodeJust" <~ ("arr" ~>
          Maybes.maybe
            (left $ string "expected single-element array for Just")
            ("firstVal" ~>
              Eithers.map ("v" ~> Core.termMaybe $ just $ var "v")
                (fromJson @@ var "types" @@ var "tname" @@ var "innerType" @@ var "firstVal"))
            (Lists.maybeHead $ var "arr")) $
        "decodeMaybeArray" <~ ("arr" ~>
          "len" <~ (Lists.length $ var "arr") $
          Logic.ifElse (Equality.equal (var "len") (int32 0))
            (right $ Core.termMaybe nothing)
            (Logic.ifElse (Equality.equal (var "len") (int32 1))
              (var "decodeJust" @@ var "arr")
              (left $ string "expected single-element array for Just"))) $
        cases _Value (var "value")
          (Just $ left $ string "expected null or single-element array for nested Maybe") [
          _Value_null>>: constant $ right $ Core.termMaybe nothing,
          _Value_array>>: "arr" ~> var "decodeMaybeArray" @@ var "arr"])
        -- Simple Maybe: idiomatic encoding (null -> Nothing, value -> Just)
        (cases _Value (var "value")
          (Just $
            Eithers.map ("v" ~> Core.termMaybe $ just $ var "v")
              (fromJson @@ var "types" @@ var "tname" @@ var "innerType" @@ var "value")) [
          _Value_null>>: constant $ right $ Core.termMaybe nothing]),

    -- Records
    _Type_record>>: "rt" ~>
      "objResult" <~ (expectObject @@ var "value") $
      Eithers.either_
        ("err" ~> left $ var "err")
        ("obj" ~>
          "decodeField" <~ ("ft" ~>
            "fname" <~ (Core.fieldTypeName $ var "ft") $
            "ftype" <~ (Core.fieldTypeType $ var "ft") $
            "mval" <~ (Maps.lookup (Core.unName $ var "fname") (var "obj")) $
            -- Use empty object as default for missing optional fields
            "defaultVal" <~ Json.valueNull $
            "jsonVal" <~ (Maybes.fromMaybe (var "defaultVal") (var "mval")) $
            "decoded" <~ (fromJson @@ var "types" @@ var "tname" @@ var "ftype" @@ var "jsonVal") $
            Eithers.map ("v" ~> Core.field (var "fname") (var "v")) (var "decoded")) $
          "decodedFields" <~ (Eithers.mapList (var "decodeField") (var "rt")) $
          Eithers.map
            ("fs" ~> Core.termRecord $ Core.record (var "tname") (var "fs"))
            (var "decodedFields"))
        (var "objResult"),

    -- Unions (single-key object)
    _Type_union>>: "rt" ~>
      -- Helper to decode a field once found
      "decodeVariant" <~ ("key" ~> "val" ~> "ftype" ~>
        "jsonVal" <~ (Maybes.fromMaybe Json.valueNull (var "val")) $
        "decoded" <~ (fromJson @@ var "types" @@ var "tname" @@ var "ftype" @@ var "jsonVal") $
        Eithers.map
          ("v" ~> Core.termInject $ Core.injection
            (var "tname")
            (Core.field (Core.name $ var "key") (var "v")))
          (var "decoded")) $
      -- Find matching field and decode (finds the field whose name matches `key`,
      -- then decodes its value; returns an error if no matching variant is present).
      "findAndDecode" <~ ("key" ~> "val" ~> "fts" ~>
        Maybes.maybe
          (left $ Strings.cat $ list [string "unknown variant: ", var "key"])
          ("ft" ~> var "decodeVariant" @@ var "key" @@ var "val" @@ (Core.fieldTypeType $ var "ft"))
          (Lists.find
            ("ft" ~> Equality.equal (Core.unName $ Core.fieldTypeName $ var "ft") (var "key"))
            (var "fts"))) $
      -- Helper to decode a single-key object
      "decodeSingleKey" <~ ("obj" ~>
        Maybes.maybe
          (left $ string "expected single-key object for union")
          ("k" ~> var "findAndDecode"
            @@ var "k"
            @@ (Maps.lookup (var "k") (var "obj"))
            @@ var "rt")
          (Lists.maybeHead $ Maps.keys $ var "obj")) $
      -- Process the union object
      "processUnion" <~ ("obj" ~>
        Logic.ifElse (Equality.equal (Lists.length $ Maps.keys $ var "obj") (int32 1))
          (var "decodeSingleKey" @@ var "obj")
          (left $ string "expected single-key object for union")) $
      "objResult" <~ (expectObject @@ var "value") $
      Eithers.either_
        ("err" ~> left $ var "err")
        ("obj" ~> var "processUnion" @@ var "obj")
        (var "objResult"),

    -- Unit (empty object)
    _Type_unit>>: constant $
      "objResult" <~ (expectObject @@ var "value") $
      Eithers.map (constant Core.termUnit) (var "objResult"),

    -- Wrapped types (look up in type table and extract inner type if needed)
    _Type_wrap>>: "wn" ~>
      -- TypeWrap now directly holds the inner Type; decode with it and wrap the result
      "decoded" <~ (fromJson @@ var "types" @@ var "tname" @@ var "wn" @@ var "value") $
      Eithers.map
        ("v" ~> Core.termWrap $ Core.wrappedTerm (var "tname") (var "v"))
        (var "decoded"),

    -- Map -> array of {key, value}
    _Type_map>>: "mt" ~>
      "keyType" <~ (Core.mapTypeKeys $ var "mt") $
      "valType" <~ (Core.mapTypeValues $ var "mt") $
      "arrResult" <~ (expectArray @@ var "value") $
      Eithers.either_
        ("err" ~> left $ var "err")
        ("arr" ~>
          "decodeEntry" <~ ("entryJson" ~>
            "objResult" <~ (expectObject @@ var "entryJson") $
            Eithers.either_
              ("err" ~> left $ var "err")
              ("entryObj" ~>
                "keyJson" <~ (Maps.lookup (string "key") (var "entryObj")) $
                "valJson" <~ (Maps.lookup (string "value") (var "entryObj")) $
                Maybes.maybe
                  (left $ string "missing key in map entry")
                  ("kj" ~> Maybes.maybe
                    (left $ string "missing value in map entry")
                    ("vj" ~>
                      "decodedKey" <~ (fromJson @@ var "types" @@ var "tname" @@ var "keyType" @@ var "kj") $
                      "decodedVal" <~ (fromJson @@ var "types" @@ var "tname" @@ var "valType" @@ var "vj") $
                      Eithers.either_
                        ("err" ~> left $ var "err")
                        ("k" ~> Eithers.map ("v" ~> pair (var "k") (var "v")) (var "decodedVal"))
                        (var "decodedKey"))
                    (var "valJson"))
                  (var "keyJson"))
              (var "objResult")) $
          "entries" <~ (Eithers.mapList (var "decodeEntry") (var "arr")) $
          Eithers.map ("es" ~> Core.termMap $ Maps.fromList $ var "es") (var "entries"))
        (var "arrResult"),

    -- Pair -> {first, second}
    _Type_pair>>: "pt" ~>
      "firstType" <~ (Core.pairTypeFirst $ var "pt") $
      "secondType" <~ (Core.pairTypeSecond $ var "pt") $
      "objResult" <~ (expectObject @@ var "value") $
      Eithers.either_
        ("err" ~> left $ var "err")
        ("obj" ~>
          "firstJson" <~ (Maps.lookup (string "first") (var "obj")) $
          "secondJson" <~ (Maps.lookup (string "second") (var "obj")) $
          Maybes.maybe
            (left $ string "missing first in pair")
            ("fj" ~> Maybes.maybe
              (left $ string "missing second in pair")
              ("sj" ~>
                "decodedFirst" <~ (fromJson @@ var "types" @@ var "tname" @@ var "firstType" @@ var "fj") $
                "decodedSecond" <~ (fromJson @@ var "types" @@ var "tname" @@ var "secondType" @@ var "sj") $
                Eithers.either_
                  ("err" ~> left $ var "err")
                  ("f" ~> Eithers.map ("s" ~> Core.termPair $ pair (var "f") (var "s")) (var "decodedSecond"))
                  (var "decodedFirst"))
              (var "secondJson"))
            (var "firstJson"))
        (var "objResult"),

    -- Either -> {left} or {right}
    _Type_either>>: "et" ~>
      "leftType" <~ (Core.eitherTypeLeft $ var "et") $
      "rightType" <~ (Core.eitherTypeRight $ var "et") $
      "objResult" <~ (expectObject @@ var "value") $
      Eithers.either_
        ("err" ~> left $ var "err")
        ("obj" ~>
          "leftJson" <~ (Maps.lookup (string "left") (var "obj")) $
          "rightJson" <~ (Maps.lookup (string "right") (var "obj")) $
          Maybes.maybe
            (Maybes.maybe
              (left $ string "expected left or right in Either")
              ("rj" ~>
                "decoded" <~ (fromJson @@ var "types" @@ var "tname" @@ var "rightType" @@ var "rj") $
                Eithers.map ("v" ~> Core.termEither $ right $ var "v") (var "decoded"))
              (var "rightJson"))
            ("lj" ~>
              "decoded" <~ (fromJson @@ var "types" @@ var "tname" @@ var "leftType" @@ var "lj") $
              Eithers.map ("v" ~> Core.termEither $ left $ var "v") (var "decoded"))
            (var "leftJson"))
        (var "objResult"),

    -- Type variables (look up in type table and recurse)
    _Type_variable>>: "name" ~>
      "lookedUp" <~ (Maps.lookup (var "name") (var "types")) $
      Maybes.maybe
        (left $ Strings.cat $ list [
          string "unknown type variable: ",
          Core.unName $ var "name"])
        ("resolvedType" ~> fromJson @@ var "types" @@ var "name" @@ var "resolvedType" @@ var "value")
        (var "lookedUp")]

-- | Decode a JSON value to a literal term given a literal type
decodeLiteral :: TTermDefinition (LiteralType -> Value -> Either String Term)
decodeLiteral = define "decodeLiteral" $
  doc "Decode a JSON value to a literal term" $
  "lt" ~> "value" ~>
  cases _LiteralType (var "lt") Nothing [
    _LiteralType_binary>>: constant $
      "strResult" <~ (expectString @@ var "value") $
      Eithers.map ("s" ~> Core.termLiteral $ Core.literalBinary $ Literals.stringToBinary $ var "s") (var "strResult"),

    _LiteralType_boolean>>: constant $
      cases _Value (var "value")
        (Just $ left $ string "expected boolean") [
        _Value_boolean>>: "b" ~> right $ Core.termLiteral $ Core.literalBoolean $ var "b"],

    _LiteralType_decimal>>: constant $
      cases _Value (var "value")
        (Just $ left $ string "expected number for decimal") [
        _Value_number>>: "n" ~> right $ Core.termLiteral $ Core.literalDecimal $ var "n"],

    _LiteralType_float>>: "ft" ~> decodeFloat @@ var "ft" @@ var "value",

    _LiteralType_integer>>: "it" ~> decodeInteger @@ var "it" @@ var "value",

    _LiteralType_string>>: constant $
      "strResult" <~ (expectString @@ var "value") $
      Eithers.map ("s" ~> Core.termLiteral $ Core.literalString $ var "s") (var "strResult")]

-- | Decode a JSON value to a float term
-- Float32, Float64, and Bigfloat all accept finite values as JSON numbers
-- Special values (NaN, Infinity, -Infinity, -0.0) are accepted as JSON string sentinels for all float types
decodeFloat :: TTermDefinition (FloatType -> Value -> Either String Term)
decodeFloat = define "decodeFloat" $
  doc "Decode a JSON value to a float term. Finite values arrive as JSON numbers; NaN/Inf/-0.0 arrive as JSON string sentinels. Float32 and Float64 are symmetric." $
  "ft" ~> "value" ~>
  cases _FloatType (var "ft") Nothing [
    -- Bigfloat: JSON number (Scientific) -> decimal -> float64 -> bigfloat. NaN/Inf are not
    -- representable in JSON's grammar, so they can only arrive via the string sentinel path below.
    _FloatType_bigfloat>>: constant $
      cases _Value (var "value")
        (Just $ left $ string "expected number or special float string for bigfloat") [
        _Value_number>>: "n" ~> right $ Core.termLiteral $ Core.literalFloat $ Core.floatValueBigfloat $
          Literals.float64ToBigfloat $ Literals.decimalToFloat64 $ var "n",
        _Value_string>>: "s" ~>
          Maybes.maybe
            (left $ Strings.cat $ list [string "invalid bigfloat sentinel: ", var "s"])
            ("v" ~> right $ Core.termLiteral $ Core.literalFloat $ Core.floatValueBigfloat $
              Literals.float64ToBigfloat $ var "v")
            (parseSpecialFloat @@ var "s")],
    -- Float32: JSON number (Scientific) -> float32, or special sentinel string
    _FloatType_float32>>: constant $
      cases _Value (var "value")
        (Just $ left $ string "expected number or special float string for float32") [
        _Value_number>>: "n" ~> right $ Core.termLiteral $ Core.literalFloat $ Core.floatValueFloat32 $ Literals.decimalToFloat32 $ var "n",
        _Value_string>>: "s" ~>
          Maybes.maybe
            (left $ Strings.cat $ list [string "invalid float32 sentinel: ", var "s"])
            ("v" ~> right $ Core.termLiteral $ Core.literalFloat $ Core.floatValueFloat32 $ var "v")
            (parseSpecialFloat32 @@ var "s")],
    -- Float64: JSON number (Scientific) -> float64, or special sentinel string
    _FloatType_float64>>: constant $
      cases _Value (var "value")
        (Just $ left $ string "expected number or special float string for float64") [
        _Value_number>>: "n" ~> right $ Core.termLiteral $ Core.literalFloat $ Core.floatValueFloat64 $ Literals.decimalToFloat64 $ var "n",
        _Value_string>>: "s" ~>
          Maybes.maybe
            (left $ Strings.cat $ list [string "invalid float64 sentinel: ", var "s"])
            ("v" ~> right $ Core.termLiteral $ Core.literalFloat $ Core.floatValueFloat64 $ var "v")
            (parseSpecialFloat @@ var "s")]]

-- | Parse a string as an IEEE sentinel float that the JSON number grammar cannot express:
-- "NaN", "Infinity", "-Infinity", or "-0.0". Returns Nothing for unrecognized strings.
-- The -0.0 case is here so that IEEE negative zero survives a round trip through JSON via
-- the encoder's string-escape path; Scientific-backed number decoding would normalize it to 0.
parseSpecialFloat :: TTermDefinition (String -> Maybe Double)
parseSpecialFloat = define "parseSpecialFloat" $
  doc "Parse an IEEE sentinel string (NaN, Infinity, -Infinity, -0.0) to a float64. Returns Nothing for unrecognized strings." $
  "s" ~>
    Logic.ifElse
      (Logic.or (Equality.equal (var "s") (string "NaN")) $
       Logic.or (Equality.equal (var "s") (string "Infinity")) $
       Logic.or (Equality.equal (var "s") (string "-Infinity"))
                (Equality.equal (var "s") (string "-0.0")))
      (Literals.readFloat64 $ var "s")
      Phantoms.nothing

-- | Parse a string as an IEEE sentinel float32. Same accepted strings as 'parseSpecialFloat',
-- but returns a float32 value.
parseSpecialFloat32 :: TTermDefinition (String -> Maybe Float)
parseSpecialFloat32 = define "parseSpecialFloat32" $
  doc "Parse an IEEE sentinel string (NaN, Infinity, -Infinity, -0.0) to a float32. Returns Nothing for unrecognized strings." $
  "s" ~>
    Logic.ifElse
      (Logic.or (Equality.equal (var "s") (string "NaN")) $
       Logic.or (Equality.equal (var "s") (string "Infinity")) $
       Logic.or (Equality.equal (var "s") (string "-Infinity"))
                (Equality.equal (var "s") (string "-0.0")))
      (Literals.readFloat32 $ var "s")
      Phantoms.nothing

-- | Decode a JSON value to an integer term
-- Small integers (int8, int16, int32, uint8, uint16) are decoded from JSON numbers
-- Large integers (int64, uint32, uint64, bigint) are decoded from JSON strings
decodeInteger :: TTermDefinition (IntegerType -> Value -> Either String Term)
decodeInteger = define "decodeInteger" $
  doc "Decode a JSON value to an integer term. Small ints from numbers; large ints from strings." $
  "it" ~> "value" ~>
  cases _IntegerType (var "it") Nothing [
    -- Large integers: decode from JSON string
    _IntegerType_bigint>>: constant $
      "strResult" <~ (expectString @@ var "value") $
      Eithers.either_
        ("err" ~> left $ var "err")
        ("s" ~>
          "parsed" <~ (Literals.readBigint $ var "s") $
          Maybes.maybe
            (left $ Strings.cat $ list [string "invalid bigint: ", var "s"])
            ("v" ~> right $ Core.termLiteral $ Core.literalInteger $ Core.integerValueBigint $ var "v")
            (var "parsed"))
        (var "strResult"),
    _IntegerType_int64>>: constant $
      "strResult" <~ (expectString @@ var "value") $
      Eithers.either_
        ("err" ~> left $ var "err")
        ("s" ~>
          "parsed" <~ (Literals.readInt64 $ var "s") $
          Maybes.maybe
            (left $ Strings.cat $ list [string "invalid int64: ", var "s"])
            ("v" ~> right $ Core.termLiteral $ Core.literalInteger $ Core.integerValueInt64 $ var "v")
            (var "parsed"))
        (var "strResult"),
    _IntegerType_uint32>>: constant $
      "strResult" <~ (expectString @@ var "value") $
      Eithers.either_
        ("err" ~> left $ var "err")
        ("s" ~>
          "parsed" <~ (Literals.readUint32 $ var "s") $
          Maybes.maybe
            (left $ Strings.cat $ list [string "invalid uint32: ", var "s"])
            ("v" ~> right $ Core.termLiteral $ Core.literalInteger $ Core.integerValueUint32 $ var "v")
            (var "parsed"))
        (var "strResult"),
    _IntegerType_uint64>>: constant $
      "strResult" <~ (expectString @@ var "value") $
      Eithers.either_
        ("err" ~> left $ var "err")
        ("s" ~>
          "parsed" <~ (Literals.readUint64 $ var "s") $
          Maybes.maybe
            (left $ Strings.cat $ list [string "invalid uint64: ", var "s"])
            ("v" ~> right $ Core.termLiteral $ Core.literalInteger $ Core.integerValueUint64 $ var "v")
            (var "parsed"))
        (var "strResult"),
    -- Small integers: decode from JSON number
    _IntegerType_int8>>: constant $
      "numResult" <~ (expectNumber @@ var "value") $
      Eithers.map
        ("n" ~> Core.termLiteral $ Core.literalInteger $ Core.integerValueInt8 $
          Literals.bigintToInt8 $ Literals.decimalToBigint $ var "n")
        (var "numResult"),
    _IntegerType_int16>>: constant $
      "numResult" <~ (expectNumber @@ var "value") $
      Eithers.map
        ("n" ~> Core.termLiteral $ Core.literalInteger $ Core.integerValueInt16 $
          Literals.bigintToInt16 $ Literals.decimalToBigint $ var "n")
        (var "numResult"),
    _IntegerType_int32>>: constant $
      "numResult" <~ (expectNumber @@ var "value") $
      Eithers.map
        ("n" ~> Core.termLiteral $ Core.literalInteger $ Core.integerValueInt32 $
          Literals.bigintToInt32 $ Literals.decimalToBigint $ var "n")
        (var "numResult"),
    _IntegerType_uint8>>: constant $
      "numResult" <~ (expectNumber @@ var "value") $
      Eithers.map
        ("n" ~> Core.termLiteral $ Core.literalInteger $ Core.integerValueUint8 $
          Literals.bigintToUint8 $ Literals.decimalToBigint $ var "n")
        (var "numResult"),
    _IntegerType_uint16>>: constant $
      "numResult" <~ (expectNumber @@ var "value") $
      Eithers.map
        ("n" ~> Core.termLiteral $ Core.literalInteger $ Core.integerValueUint16 $
          Literals.bigintToUint16 $ Literals.decimalToBigint $ var "n")
        (var "numResult")]

-- | Extract a string from a JSON value
expectString :: TTermDefinition (Value -> Either String String)
expectString = define "expectString" $
  doc "Extract a string from a JSON value" $
  "value" ~> cases _Value (var "value")
    (Just $ left $ string "expected string") [
    _Value_string>>: "s" ~> right $ var "s"]

-- | Extract an array from a JSON value
expectArray :: TTermDefinition (Value -> Either String [Value])
expectArray = define "expectArray" $
  doc "Extract an array from a JSON value" $
  "value" ~> cases _Value (var "value")
    (Just $ left $ string "expected array") [
    _Value_array>>: "arr" ~> right $ var "arr"]

-- | Extract an object from a JSON value
expectObject :: TTermDefinition (Value -> Either String (M.Map String Value))
expectObject = define "expectObject" $
  doc "Extract an object from a JSON value" $
  "value" ~> cases _Value (var "value")
    (Just $ left $ string "expected object") [
    _Value_object>>: "obj" ~> right $ var "obj"]

-- | Extract a number from a JSON value
expectNumber :: TTermDefinition (Value -> Either String Sci.Scientific)
expectNumber = define "expectNumber" $
  doc "Extract a number from a JSON value" $
  "value" ~> cases _Value (var "value")
    (Just $ left $ string "expected number") [
    _Value_number>>: "n" ~> right $ var "n"]