-- Hoogle documentation, generated by Haddock
-- See Hoogle, http://www.haskell.org/hoogle/

-- | Fast JSON parsing and encoding
--   
--   A JSON parsing and encoding library optimized for ease of use and high
--   performance.
--   
--   To get started, see the documentation for the Data.Aeson
--   module below.
--   
--   Parsing performance on a late 2013 MacBook Pro (2.6GHz Core i7),
--   running 64-bit GHC 7.10.1, for mostly-English tweets from Twitter's
--   JSON search API:
--   
--   
--   
- 6.4 KB payloads, English: 7570 msg/sec (47.6 MB/sec)
--   
- 14.6 KB payloads, Japanese: 3261 msg/sec (46.6 MB/sec)
--   
--   
--   Encoding performance on the same machine and data:
--   
--   
--   
- 6.4 KB payloads, English: 22738 msg/sec (142.9 MB/sec)
--   
- 14.6 KB payloads, Japanese: 15911 msg/sec (227.4 MB/sec)
--   
--   
--   (A note on naming: in Greek mythology, Aeson was the father of Jason.)
@package aeson
@version 0.10.0.0

module Data.Aeson.Internal.Time

-- | Like TimeOfDay, but using a fixed-width integer for seconds.
data TimeOfDay64
TOD :: {-# UNPACK #-} !Int -> {-# UNPACK #-} !Int -> {-# UNPACK #-} !Int64 -> TimeOfDay64
fromPico :: Pico -> Integer
toPico :: Integer -> Pico
diffTimeOfDay64 :: DiffTime -> TimeOfDay64
toTimeOfDay64 :: TimeOfDay -> TimeOfDay64

-- | Internal types and functions.
--   
--   Note: all declarations in this module are unstable, and prone
--   to being changed at any time.
module Data.Aeson.Internal

-- | The internal result of running a Parser.
data IResult a
IError :: JSONPath -> String -> IResult a
ISuccess :: a -> IResult a

-- | Elements of a JSON path used to describe the location of an error.
data JSONPathElement
type JSONPath = [JSONPathElement]

-- | Annotate an error message with a JSONPath error location.
formatError :: JSONPath -> String -> String

-- | Convert a value from JSON, failing if the types do not match.
ifromJSON :: (FromJSON a) => Value -> IResult a

-- | Run a Parser.
iparse :: (a -> Parser b) -> a -> IResult b

-- | Types for working with JSON data.
module Data.Aeson.Types

-- | A JSON value represented as a Haskell value.
data Value
Object :: !Object -> Value
Array :: !Array -> Value
String :: !Text -> Value
Number :: !Scientific -> Value
Bool :: !Bool -> Value
Null :: Value

-- | An encoding of a JSON value.
data Encoding

-- | Acquire the underlying bytestring builder.
fromEncoding :: Encoding -> Builder

-- | A series of values that, when encoded, should be separated by commas.
data Series

-- | A JSON "array" (sequence).
type Array = Vector Value

-- | The empty array.
emptyArray :: Value

-- | A key/value pair for an Object.
type Pair = (Text, Value)

-- | A JSON "object" (key/value map).
type Object = HashMap Text Value

-- | The empty object.
emptyObject :: Value

-- | A newtype wrapper for UTCTime that uses the same non-standard
--   serialization format as Microsoft .NET, whose System.DateTime
--   type is by default serialized to JSON as in the following example:
--   
--   
--   /Date(1302547608878)/
--   
--   
--   The number represents milliseconds since the Unix epoch.
newtype DotNetTime
DotNetTime :: UTCTime -> DotNetTime

-- | Acquire the underlying value.
[fromDotNetTime] :: DotNetTime -> UTCTime

-- | Fail parsing due to a type mismatch, with a descriptive message.
--   
--   Example usage:
--   
--   
--   instance FromJSON Coord where
--     parseJSON (Object v) = {- type matches, life is good -}
--     parseJSON wat        = typeMismatch "Coord" wat
--   
typeMismatch :: String -> Value -> Parser a

-- | A JSON parser.
data Parser a

-- | The result of running a Parser.
data Result a
Error :: String -> Result a
Success :: a -> Result a

-- | A type that can be converted from JSON, with the possibility of
--   failure.
--   
--   In many cases, you can get the compiler to generate parsing code for
--   you (see below). To begin, let's cover writing an instance by hand.
--   
--   There are various reasons a conversion could fail. For example, an
--   Object could be missing a required key, an Array could
--   be of the wrong size, or a value could be of an incompatible type.
--   
--   The basic ways to signal a failed conversion are as follows:
--   
--   
--   
- empty and mzero work, but are terse and
--   uninformative
--   
- fail yields a custom error message
--   
- typeMismatch produces an informative message for cases when
--   the value encountered is not of the expected type
--   
--   
--   An example type and instance:
--   
--   
--   -- Allow ourselves to write Text literals.
--   {-# LANGUAGE OverloadedStrings #-}
--   
--   data Coord = Coord { x :: Double, y :: Double }
--   
--   instance FromJSON Coord where
--     parseJSON (Object v) = Coord    <$>
--                            v .: "x" <*>
--                            v .: "y"
--   
--     -- We do not expect a non-Object value here.
--     -- We could use mzero to fail, but typeMismatch
--     -- gives a much more informative error message.
--     parseJSON invalid    = typeMismatch "Coord" invalid
--   
--   
--   Instead of manually writing your FromJSON instance, there are
--   two options to do it automatically:
--   
--   
--   
- Data.Aeson.TH provides Template Haskell functions which
--   will derive an instance at compile time. The generated instance is
--   optimized for your type so will probably be more efficient than the
--   following two options:
--   
- The compiler can provide a default generic implementation for
--   parseJSON.
--   
--   
--   To use the second, simply add a deriving Generic
--   clause to your datatype and declare a FromJSON instance for
--   your datatype without giving a definition for parseJSON.
--   
--   For example, the previous example can be simplified to just:
--   
--   
--   {-# LANGUAGE DeriveGeneric #-}
--   
--   import GHC.Generics
--   
--   data Coord = Coord { x :: Double, y :: Double } deriving Generic
--   
--   instance FromJSON Coord
--   
--   
--   If DefaultSignatures doesn't give exactly the results you
--   want, you can customize the generic decoding with only a tiny amount
--   of effort, using genericParseJSON with your preferred
--   Options:
--   
--   
--   instance FromJSON Coord where
--       parseJSON = genericParseJSON defaultOptions
--   
class FromJSON a where parseJSON = genericParseJSON defaultOptions
parseJSON :: FromJSON a => Value -> Parser a

-- | Convert a value from JSON, failing if the types do not match.
fromJSON :: (FromJSON a) => Value -> Result a

-- | Run a Parser.
parse :: (a -> Parser b) -> a -> Result b

-- | Run a Parser with an Either result type. If the parse
--   fails, the Left payload will contain an error message.
parseEither :: (a -> Parser b) -> a -> Either String b

-- | Run a Parser with a Maybe result type.
parseMaybe :: (a -> Parser b) -> a -> Maybe b

-- | A type that can be converted to JSON.
--   
--   An example type and instance:
--   
--   
--   -- Allow ourselves to write Text literals.
--   {-# LANGUAGE OverloadedStrings #-}
--   
--   data Coord = Coord { x :: Double, y :: Double }
--   
--   instance ToJSON Coord where
--     toJSON (Coord x y) = object ["x" .= x, "y" .= y]
--   
--     toEncoding (Coord x y) = pairs ("x" .= x <> "y" .= y)
--   
--   
--   Instead of manually writing your ToJSON instance, there are two
--   options to do it automatically:
--   
--   
--   
- Data.Aeson.TH provides Template Haskell functions which
--   will derive an instance at compile time. The generated instance is
--   optimized for your type so will probably be more efficient than the
--   following two options:
--   
- The compiler can provide a default generic implementation for
--   toJSON.
--   
--   
--   To use the second, simply add a deriving Generic
--   clause to your datatype and declare a ToJSON instance for your
--   datatype without giving definitions for toJSON or
--   toEncoding.
--   
--   For example, the previous example can be simplified to a more minimal
--   instance:
--   
--   
--   {-# LANGUAGE DeriveGeneric #-}
--   
--   import GHC.Generics
--   
--   data Coord = Coord { x :: Double, y :: Double } deriving Generic
--   
--   instance ToJSON Coord where
--       toEncoding = genericToEncoding defaultOptions
--   
--   
--   Why do we provide an implementation for toEncoding here? The
--   toEncoding function is a relatively new addition to this class.
--   To allow users of older versions of this library to upgrade without
--   having to edit all of their instances or encounter surprising
--   incompatibilities, the default implementation of toEncoding
--   uses toJSON. This produces correct results, but since it
--   performs an intermediate conversion to a Value, it will be less
--   efficient than directly emitting an Encoding. Our one-liner
--   definition of toEncoding above bypasses the intermediate
--   Value.
--   
--   If DefaultSignatures doesn't give exactly the results you
--   want, you can customize the generic encoding with only a tiny amount
--   of effort, using genericToJSON and genericToEncoding
--   with your preferred Options:
--   
--   
--   instance ToJSON Coord where
--       toJSON     = genericToJSON defaultOptions
--       toEncoding = genericToEncoding defaultOptions
--   
class ToJSON a where toJSON = genericToJSON defaultOptions toEncoding = Encoding . encodeToBuilder . toJSON

-- | Convert a Haskell value to a JSON-friendly intermediate type.
toJSON :: ToJSON a => a -> Value

-- | Encode a Haskell value as JSON.
--   
--   The default implementation of this method creates an intermediate
--   Value using toJSON. This provides source-level
--   compatibility for people upgrading from older versions of this
--   library, but obviously offers no performance advantage.
--   
--   To benefit from direct encoding, you must provide an
--   implementation for this method. The easiest way to do so is by having
--   your types implement Generic using the DeriveGeneric
--   extension, and then have GHC generate a method body as follows.
--   
--   
--   instance ToJSON Coord where
--       toEncoding = genericToEncoding defaultOptions
--   
toEncoding :: ToJSON a => a -> Encoding

-- | A key-value pair for encoding a JSON object.
class KeyValue kv
(.=) :: (KeyValue kv, ToJSON v) => Text -> v -> kv

-- | If the inner Parser failed, modify the failure message using
--   the provided function. This allows you to create more descriptive
--   error messages. For example:
--   
--   
--   parseJSON (Object o) = modifyFailure
--       ("Parsing of the Foo value failed: " ++)
--       (Foo <$> o .: "someField")
--   
--   
--   Since 0.6.2.0
modifyFailure :: (String -> String) -> Parser a -> Parser a

-- | Class of generic representation types (Rep) that can be
--   converted from JSON.
class GFromJSON f

-- | This method (applied to defaultOptions) is used as the default
--   generic implementation of parseJSON.
gParseJSON :: GFromJSON f => Options -> Value -> Parser (f a)

-- | Class of generic representation types (Rep) that can be
--   converted to JSON.
class GToJSON f

-- | This method (applied to defaultOptions) is used as the default
--   generic implementation of toJSON.
gToJSON :: GToJSON f => Options -> f a -> Value

-- | This method (applied to defaultOptions) can be used as the
--   default generic implementation of toEncoding.
gToEncoding :: GToJSON f => Options -> f a -> Encoding

-- | A configurable generic JSON creator. This function applied to
--   defaultOptions is used as the default for toJSON when
--   the type is an instance of Generic.
genericToJSON :: (Generic a, GToJSON (Rep a)) => Options -> a -> Value

-- | A configurable generic JSON encoder. This function applied to
--   defaultOptions is used as the default for toEncoding
--   when the type is an instance of Generic.
genericToEncoding :: (Generic a, GToJSON (Rep a)) => Options -> a -> Encoding

-- | A configurable generic JSON decoder. This function applied to
--   defaultOptions is used as the default for parseJSON when
--   the type is an instance of Generic.
genericParseJSON :: (Generic a, GFromJSON (Rep a)) => Options -> Value -> Parser a

-- | withObject expected f value applies f to the
--   Object when value is an Object and fails
--   using typeMismatch expected otherwise.
withObject :: String -> (Object -> Parser a) -> Value -> Parser a

-- | withText expected f value applies f to the
--   Text when value is a String and fails using
--   typeMismatch expected otherwise.
withText :: String -> (Text -> Parser a) -> Value -> Parser a

-- | withArray expected f value applies f to the
--   Array when value is an Array and fails using
--   typeMismatch expected otherwise.
withArray :: String -> (Array -> Parser a) -> Value -> Parser a

-- | withNumber expected f value applies f to the
--   Number when value is a Number. and fails using
--   typeMismatch expected otherwise.

-- | Deprecated: Use withScientific instead
withNumber :: String -> (Number -> Parser a) -> Value -> Parser a

-- | withScientific expected f value applies f to the
--   Scientific number when value is a Number. and
--   fails using typeMismatch expected otherwise.
withScientific :: String -> (Scientific -> Parser a) -> Value -> Parser a

-- | withBool expected f value applies f to the
--   Bool when value is a Bool and fails using
--   typeMismatch expected otherwise.
withBool :: String -> (Bool -> Parser a) -> Value -> Parser a

-- | Encode a series of key/value pairs, separated by commas.
pairs :: Series -> Encoding

-- | Encode a Foldable as a JSON array.
foldable :: (Foldable t, ToJSON a) => t a -> Encoding

-- | Retrieve the value associated with the given key of an Object.
--   The result is empty if the key is not present or the value
--   cannot be converted to the desired type.
--   
--   This accessor is appropriate if the key and value must be
--   present in an object for it to be valid. If the key and value are
--   optional, use '(.:?)' instead.
(.:) :: (FromJSON a) => Object -> Text -> Parser a

-- | Retrieve the value associated with the given key of an Object.
--   The result is Nothing if the key is not present, or
--   empty if the value cannot be converted to the desired type.
--   
--   This accessor is most useful if the key and value can be absent from
--   an object without affecting its validity. If the key and value are
--   mandatory, use '(.:)' instead.
(.:?) :: (FromJSON a) => Object -> Text -> Parser (Maybe a)

-- | Helper for use in combination with .:? to provide default
--   values for optional JSON object fields.
--   
--   This combinator is most useful if the key and value can be absent from
--   an object without affecting its validity and we know a default value
--   to assign in that case. If the key and value are mandatory, use '(.:)'
--   instead.
--   
--   Example usage:
--   
--   
--   v1 <- o .:? "opt_field_with_dfl" .!= "default_val"
--   v2 <- o .:  "mandatory_field"
--   v3 <- o .:? "opt_field2"
--   
(.!=) :: Parser (Maybe a) -> a -> Parser a

-- | Create a Value from a list of name/value Pairs. If
--   duplicate keys arise, earlier keys and their associated values win.
object :: [Pair] -> Value

-- | Options that specify how to encode/decode your datatype to/from JSON.
data Options
Options :: (String -> String) -> (String -> String) -> Bool -> Bool -> SumEncoding -> Bool -> Options

-- | Function applied to field labels. Handy for removing common record
--   prefixes for example.
[fieldLabelModifier] :: Options -> String -> String

-- | Function applied to constructor tags which could be handy for
--   lower-casing them for example.
[constructorTagModifier] :: Options -> String -> String

-- | If True the constructors of a datatype, with all nullary
--   constructors, will be encoded to just a string with the constructor
--   tag. If False the encoding will always follow the
--   sumEncoding.
[allNullaryToStringTag] :: Options -> Bool

-- | If True record fields with a Nothing value will be
--   omitted from the resulting object. If False the resulting
--   object will include those fields mapping to null.
[omitNothingFields] :: Options -> Bool

-- | Specifies how to encode constructors of a sum datatype.
[sumEncoding] :: Options -> SumEncoding

-- | Hide the field name when a record constructor has only one field, like
--   a newtype.
[unwrapUnaryRecords] :: Options -> Bool

-- | Specifies how to encode constructors of a sum datatype.
data SumEncoding

-- | A constructor will be encoded to an object with a field
--   tagFieldName which specifies the constructor tag (modified by
--   the constructorTagModifier). If the constructor is a record the
--   encoded record fields will be unpacked into this object. So make sure
--   that your record doesn't have a field with the same label as the
--   tagFieldName. Otherwise the tag gets overwritten by the encoded
--   value of that field! If the constructor is not a record the encoded
--   constructor contents will be stored under the contentsFieldName
--   field.
TaggedObject :: String -> String -> SumEncoding
[tagFieldName] :: SumEncoding -> String
[contentsFieldName] :: SumEncoding -> String

-- | A constructor will be encoded to an object with a single field named
--   after the constructor tag (modified by the
--   constructorTagModifier) which maps to the encoded contents of
--   the constructor.
ObjectWithSingleField :: SumEncoding

-- | A constructor will be encoded to a 2-element array where the first
--   element is the tag of the constructor (modified by the
--   constructorTagModifier) and the second element the encoded
--   contents of the constructor.
TwoElemArray :: SumEncoding

-- | Converts from CamelCase to another lower case, interspersing the
--   character between all capital letters and their previous entries,
--   except those capital letters that appear together, like API.
--   
--   For use by Aeson template haskell calls.
--   
--   
--   camelTo '_' 'CamelCaseAPI' == "camel_case_api"
--   

-- | Deprecated: Use camelTo2 for better results
camelTo :: Char -> String -> String

-- | Better version of camelTo. Example where it works better:
--   
--   
--   camelTo '_' 'CamelAPICase' == "camel_apicase"
--   camelTo2 '_' 'CamelAPICase' == "camel_api_case"
--   
camelTo2 :: Char -> String -> String

-- | Default encoding Options:
--   
--   
--   Options
--   { fieldLabelModifier      = id
--   , constructorTagModifier  = id
--   , allNullaryToStringTag   = True
--   , omitNothingFields       = False
--   , sumEncoding             = defaultTaggedObject
--   }
--   
defaultOptions :: Options

-- | Default TaggedObject SumEncoding options:
--   
--   
--   defaultTaggedObject = TaggedObject
--                         { tagFieldName      = "tag"
--                         , contentsFieldName = "contents"
--                         }
--   
defaultTaggedObject :: SumEncoding

-- | Efficiently and correctly parse a JSON string. The string must be
--   encoded as UTF-8.
--   
--   It can be useful to think of parsing as occurring in two phases:
--   
--   
--   
- Identification of the textual boundaries of a JSON value. This is
--   always strict, so that an invalid JSON document can be rejected as
--   soon as possible.
--   
- Conversion of a JSON value to a Haskell value. This may be either
--   immediate (strict) or deferred (lazy); see below for details.
--   
--   
--   The question of whether to choose a lazy or strict parser is subtle,
--   but it can have significant performance implications, resulting in
--   changes in CPU use and memory footprint of 30% to 50%, or occasionally
--   more. Measure the performance of your application with each!
module Data.Aeson.Parser

-- | Parse a top-level JSON value.
--   
--   The conversion of a parsed value to a Haskell value is deferred until
--   the Haskell value is needed. This may improve performance if only a
--   subset of the results of conversions are needed, but at a cost in
--   thunk allocation.
--   
--   This function is an alias for value. In aeson 0.8 and earlier,
--   it parsed only object or array types, in conformance with the
--   now-obsolete RFC 4627.
json :: Parser Value

-- | Parse any JSON value. You should usually json in preference to
--   this function, as this function relaxes the object-or-array
--   requirement of RFC 4627.
--   
--   In particular, be careful in using this function if you think your
--   code might interoperate with Javascript. A naïve Javascript library
--   that parses JSON data using eval is vulnerable to attack
--   unless the encoded data represents an object or an array. JSON
--   implementations in other languages conform to that same restriction to
--   preserve interoperability and security.
value :: Parser Value

-- | Parse a quoted JSON string.
jstring :: Parser Text

-- | Parse a top-level JSON value.
--   
--   This is a strict version of json which avoids building up
--   thunks during parsing; it performs all conversions immediately. Prefer
--   this version if most of the JSON data needs to be accessed.
--   
--   This function is an alias for value'. In aeson 0.8 and earlier,
--   it parsed only object or array types, in conformance with the
--   now-obsolete RFC 4627.
json' :: Parser Value

-- | Strict version of value. See also json'.
value' :: Parser Value

-- | Efficiently serialize a JSON value.
--   
--   Most frequently, you'll probably want to encode straight to UTF-8 (the
--   standard JSON encoding) using encode.
--   
--   You can use the conversions to Builders when embedding JSON
--   messages as parts of a protocol.
module Data.Aeson.Encode

-- | Efficiently serialize a JSON value as a lazy ByteString.
--   
--   This is implemented in terms of the ToJSON class's
--   toEncoding method.
encode :: ToJSON a => a -> ByteString

-- | Encode a JSON value to a Data.ByteString Builder.
--   
--   Use this function if you are encoding over the wire, or need to
--   prepend or append further bytes to the encoded JSON value.
encodeToBuilder :: Value -> Builder

-- | Encode a JSON Value to a Data.Text Builder, which
--   can be embedded efficiently in a text-based protocol.
--   
--   If you are going to immediately encode straight to a
--   ByteString, it is more efficient to use encodeToBuilder
--   instead.
encodeToTextBuilder :: Value -> Builder

-- | Deprecated: Use encodeToTextBuilder instead
fromValue :: Value -> Builder

-- | Types and functions for working efficiently with JSON data.
--   
--   (A note on naming: in Greek mythology, Aeson was the father of Jason.)
module Data.Aeson

-- | Efficiently deserialize a JSON value from a lazy ByteString. If
--   this fails due to incomplete or invalid input, Nothing is
--   returned.
--   
--   The input must consist solely of a JSON document, with no trailing
--   data except for whitespace.
--   
--   This function parses immediately, but defers conversion. See
--   json for details.
decode :: (FromJSON a) => ByteString -> Maybe a

-- | Efficiently deserialize a JSON value from a lazy ByteString. If
--   this fails due to incomplete or invalid input, Nothing is
--   returned.
--   
--   The input must consist solely of a JSON document, with no trailing
--   data except for whitespace.
--   
--   This function parses and performs conversion immediately. See
--   json' for details.
decode' :: (FromJSON a) => ByteString -> Maybe a

-- | Like decode but returns an error message when decoding fails.
eitherDecode :: (FromJSON a) => ByteString -> Either String a

-- | Like decode' but returns an error message when decoding fails.
eitherDecode' :: (FromJSON a) => ByteString -> Either String a

-- | Efficiently serialize a JSON value as a lazy ByteString.
--   
--   This is implemented in terms of the ToJSON class's
--   toEncoding method.
encode :: ToJSON a => a -> ByteString

-- | Efficiently deserialize a JSON value from a strict ByteString.
--   If this fails due to incomplete or invalid input, Nothing is
--   returned.
--   
--   The input must consist solely of a JSON document, with no trailing
--   data except for whitespace.
--   
--   This function parses immediately, but defers conversion. See
--   json for details.
decodeStrict :: (FromJSON a) => ByteString -> Maybe a

-- | Efficiently deserialize a JSON value from a lazy ByteString. If
--   this fails due to incomplete or invalid input, Nothing is
--   returned.
--   
--   The input must consist solely of a JSON document, with no trailing
--   data except for whitespace.
--   
--   This function parses and performs conversion immediately. See
--   json' for details.
decodeStrict' :: (FromJSON a) => ByteString -> Maybe a

-- | Like decodeStrict but returns an error message when decoding
--   fails.
eitherDecodeStrict :: (FromJSON a) => ByteString -> Either String a

-- | Like decodeStrict' but returns an error message when decoding
--   fails.
eitherDecodeStrict' :: (FromJSON a) => ByteString -> Either String a

-- | A JSON value represented as a Haskell value.
data Value
Object :: !Object -> Value
Array :: !Array -> Value
String :: !Text -> Value
Number :: !Scientific -> Value
Bool :: !Bool -> Value
Null :: Value

-- | An encoding of a JSON value.
data Encoding

-- | Acquire the underlying bytestring builder.
fromEncoding :: Encoding -> Builder

-- | A JSON "array" (sequence).
type Array = Vector Value

-- | A JSON "object" (key/value map).
type Object = HashMap Text Value

-- | A newtype wrapper for UTCTime that uses the same non-standard
--   serialization format as Microsoft .NET, whose System.DateTime
--   type is by default serialized to JSON as in the following example:
--   
--   
--   /Date(1302547608878)/
--   
--   
--   The number represents milliseconds since the Unix epoch.
newtype DotNetTime
DotNetTime :: UTCTime -> DotNetTime

-- | Acquire the underlying value.
[fromDotNetTime] :: DotNetTime -> UTCTime

-- | A type that can be converted from JSON, with the possibility of
--   failure.
--   
--   In many cases, you can get the compiler to generate parsing code for
--   you (see below). To begin, let's cover writing an instance by hand.
--   
--   There are various reasons a conversion could fail. For example, an
--   Object could be missing a required key, an Array could
--   be of the wrong size, or a value could be of an incompatible type.
--   
--   The basic ways to signal a failed conversion are as follows:
--   
--   
--   
- empty and mzero work, but are terse and
--   uninformative
--   
- fail yields a custom error message
--   
- typeMismatch produces an informative message for cases when
--   the value encountered is not of the expected type
--   
--   
--   An example type and instance:
--   
--   
--   -- Allow ourselves to write Text literals.
--   {-# LANGUAGE OverloadedStrings #-}
--   
--   data Coord = Coord { x :: Double, y :: Double }
--   
--   instance FromJSON Coord where
--     parseJSON (Object v) = Coord    <$>
--                            v .: "x" <*>
--                            v .: "y"
--   
--     -- We do not expect a non-Object value here.
--     -- We could use mzero to fail, but typeMismatch
--     -- gives a much more informative error message.
--     parseJSON invalid    = typeMismatch "Coord" invalid
--   
--   
--   Instead of manually writing your FromJSON instance, there are
--   two options to do it automatically:
--   
--   
--   
- Data.Aeson.TH provides Template Haskell functions which
--   will derive an instance at compile time. The generated instance is
--   optimized for your type so will probably be more efficient than the
--   following two options:
--   
- The compiler can provide a default generic implementation for
--   parseJSON.
--   
--   
--   To use the second, simply add a deriving Generic
--   clause to your datatype and declare a FromJSON instance for
--   your datatype without giving a definition for parseJSON.
--   
--   For example, the previous example can be simplified to just:
--   
--   
--   {-# LANGUAGE DeriveGeneric #-}
--   
--   import GHC.Generics
--   
--   data Coord = Coord { x :: Double, y :: Double } deriving Generic
--   
--   instance FromJSON Coord
--   
--   
--   If DefaultSignatures doesn't give exactly the results you
--   want, you can customize the generic decoding with only a tiny amount
--   of effort, using genericParseJSON with your preferred
--   Options:
--   
--   
--   instance FromJSON Coord where
--       parseJSON = genericParseJSON defaultOptions
--   
class FromJSON a where parseJSON = genericParseJSON defaultOptions
parseJSON :: FromJSON a => Value -> Parser a

-- | The result of running a Parser.
data Result a
Error :: String -> Result a
Success :: a -> Result a

-- | Convert a value from JSON, failing if the types do not match.
fromJSON :: (FromJSON a) => Value -> Result a

-- | A type that can be converted to JSON.
--   
--   An example type and instance:
--   
--   
--   -- Allow ourselves to write Text literals.
--   {-# LANGUAGE OverloadedStrings #-}
--   
--   data Coord = Coord { x :: Double, y :: Double }
--   
--   instance ToJSON Coord where
--     toJSON (Coord x y) = object ["x" .= x, "y" .= y]
--   
--     toEncoding (Coord x y) = pairs ("x" .= x <> "y" .= y)
--   
--   
--   Instead of manually writing your ToJSON instance, there are two
--   options to do it automatically:
--   
--   
--   
- Data.Aeson.TH provides Template Haskell functions which
--   will derive an instance at compile time. The generated instance is
--   optimized for your type so will probably be more efficient than the
--   following two options:
--   
- The compiler can provide a default generic implementation for
--   toJSON.
--   
--   
--   To use the second, simply add a deriving Generic
--   clause to your datatype and declare a ToJSON instance for your
--   datatype without giving definitions for toJSON or
--   toEncoding.
--   
--   For example, the previous example can be simplified to a more minimal
--   instance:
--   
--   
--   {-# LANGUAGE DeriveGeneric #-}
--   
--   import GHC.Generics
--   
--   data Coord = Coord { x :: Double, y :: Double } deriving Generic
--   
--   instance ToJSON Coord where
--       toEncoding = genericToEncoding defaultOptions
--   
--   
--   Why do we provide an implementation for toEncoding here? The
--   toEncoding function is a relatively new addition to this class.
--   To allow users of older versions of this library to upgrade without
--   having to edit all of their instances or encounter surprising
--   incompatibilities, the default implementation of toEncoding
--   uses toJSON. This produces correct results, but since it
--   performs an intermediate conversion to a Value, it will be less
--   efficient than directly emitting an Encoding. Our one-liner
--   definition of toEncoding above bypasses the intermediate
--   Value.
--   
--   If DefaultSignatures doesn't give exactly the results you
--   want, you can customize the generic encoding with only a tiny amount
--   of effort, using genericToJSON and genericToEncoding
--   with your preferred Options:
--   
--   
--   instance ToJSON Coord where
--       toJSON     = genericToJSON defaultOptions
--       toEncoding = genericToEncoding defaultOptions
--   
class ToJSON a where toJSON = genericToJSON defaultOptions toEncoding = Encoding . encodeToBuilder . toJSON

-- | Convert a Haskell value to a JSON-friendly intermediate type.
toJSON :: ToJSON a => a -> Value

-- | Encode a Haskell value as JSON.
--   
--   The default implementation of this method creates an intermediate
--   Value using toJSON. This provides source-level
--   compatibility for people upgrading from older versions of this
--   library, but obviously offers no performance advantage.
--   
--   To benefit from direct encoding, you must provide an
--   implementation for this method. The easiest way to do so is by having
--   your types implement Generic using the DeriveGeneric
--   extension, and then have GHC generate a method body as follows.
--   
--   
--   instance ToJSON Coord where
--       toEncoding = genericToEncoding defaultOptions
--   
toEncoding :: ToJSON a => a -> Encoding

-- | A key-value pair for encoding a JSON object.
class KeyValue kv
(.=) :: (KeyValue kv, ToJSON v) => Text -> v -> kv

-- | Class of generic representation types (Rep) that can be
--   converted from JSON.
class GFromJSON f

-- | This method (applied to defaultOptions) is used as the default
--   generic implementation of parseJSON.
gParseJSON :: GFromJSON f => Options -> Value -> Parser (f a)

-- | Class of generic representation types (Rep) that can be
--   converted to JSON.
class GToJSON f

-- | This method (applied to defaultOptions) is used as the default
--   generic implementation of toJSON.
gToJSON :: GToJSON f => Options -> f a -> Value

-- | This method (applied to defaultOptions) can be used as the
--   default generic implementation of toEncoding.
gToEncoding :: GToJSON f => Options -> f a -> Encoding

-- | A configurable generic JSON creator. This function applied to
--   defaultOptions is used as the default for toJSON when
--   the type is an instance of Generic.
genericToJSON :: (Generic a, GToJSON (Rep a)) => Options -> a -> Value

-- | A configurable generic JSON encoder. This function applied to
--   defaultOptions is used as the default for toEncoding
--   when the type is an instance of Generic.
genericToEncoding :: (Generic a, GToJSON (Rep a)) => Options -> a -> Encoding

-- | A configurable generic JSON decoder. This function applied to
--   defaultOptions is used as the default for parseJSON when
--   the type is an instance of Generic.
genericParseJSON :: (Generic a, GFromJSON (Rep a)) => Options -> Value -> Parser a

-- | Default encoding Options:
--   
--   
--   Options
--   { fieldLabelModifier      = id
--   , constructorTagModifier  = id
--   , allNullaryToStringTag   = True
--   , omitNothingFields       = False
--   , sumEncoding             = defaultTaggedObject
--   }
--   
defaultOptions :: Options

-- | withObject expected f value applies f to the
--   Object when value is an Object and fails
--   using typeMismatch expected otherwise.
withObject :: String -> (Object -> Parser a) -> Value -> Parser a

-- | withText expected f value applies f to the
--   Text when value is a String and fails using
--   typeMismatch expected otherwise.
withText :: String -> (Text -> Parser a) -> Value -> Parser a

-- | withArray expected f value applies f to the
--   Array when value is an Array and fails using
--   typeMismatch expected otherwise.
withArray :: String -> (Array -> Parser a) -> Value -> Parser a

-- | withNumber expected f value applies f to the
--   Number when value is a Number. and fails using
--   typeMismatch expected otherwise.

-- | Deprecated: Use withScientific instead
withNumber :: String -> (Number -> Parser a) -> Value -> Parser a

-- | withScientific expected f value applies f to the
--   Scientific number when value is a Number. and
--   fails using typeMismatch expected otherwise.
withScientific :: String -> (Scientific -> Parser a) -> Value -> Parser a

-- | withBool expected f value applies f to the
--   Bool when value is a Bool and fails using
--   typeMismatch expected otherwise.
withBool :: String -> (Bool -> Parser a) -> Value -> Parser a

-- | A series of values that, when encoded, should be separated by commas.
data Series

-- | Encode a series of key/value pairs, separated by commas.
pairs :: Series -> Encoding

-- | Encode a Foldable as a JSON array.
foldable :: (Foldable t, ToJSON a) => t a -> Encoding

-- | Retrieve the value associated with the given key of an Object.
--   The result is empty if the key is not present or the value
--   cannot be converted to the desired type.
--   
--   This accessor is appropriate if the key and value must be
--   present in an object for it to be valid. If the key and value are
--   optional, use '(.:?)' instead.
(.:) :: (FromJSON a) => Object -> Text -> Parser a

-- | Retrieve the value associated with the given key of an Object.
--   The result is Nothing if the key is not present, or
--   empty if the value cannot be converted to the desired type.
--   
--   This accessor is most useful if the key and value can be absent from
--   an object without affecting its validity. If the key and value are
--   mandatory, use '(.:)' instead.
(.:?) :: (FromJSON a) => Object -> Text -> Parser (Maybe a)

-- | Helper for use in combination with .:? to provide default
--   values for optional JSON object fields.
--   
--   This combinator is most useful if the key and value can be absent from
--   an object without affecting its validity and we know a default value
--   to assign in that case. If the key and value are mandatory, use '(.:)'
--   instead.
--   
--   Example usage:
--   
--   
--   v1 <- o .:? "opt_field_with_dfl" .!= "default_val"
--   v2 <- o .:  "mandatory_field"
--   v3 <- o .:? "opt_field2"
--   
(.!=) :: Parser (Maybe a) -> a -> Parser a

-- | Create a Value from a list of name/value Pairs. If
--   duplicate keys arise, earlier keys and their associated values win.
object :: [Pair] -> Value

-- | Parse a top-level JSON value.
--   
--   The conversion of a parsed value to a Haskell value is deferred until
--   the Haskell value is needed. This may improve performance if only a
--   subset of the results of conversions are needed, but at a cost in
--   thunk allocation.
--   
--   This function is an alias for value. In aeson 0.8 and earlier,
--   it parsed only object or array types, in conformance with the
--   now-obsolete RFC 4627.
json :: Parser Value

-- | Parse a top-level JSON value.
--   
--   This is a strict version of json which avoids building up
--   thunks during parsing; it performs all conversions immediately. Prefer
--   this version if most of the JSON data needs to be accessed.
--   
--   This function is an alias for value'. In aeson 0.8 and earlier,
--   it parsed only object or array types, in conformance with the
--   now-obsolete RFC 4627.
json' :: Parser Value

-- | Functions to mechanically derive ToJSON and FromJSON
--   instances. Note that you need to enable the TemplateHaskell
--   language extension in order to use this module.
--   
--   An example shows how instances are generated for arbitrary data types.
--   First we define a data type:
--   
--   
--   data D a = Nullary
--            | Unary Int
--            | Product String Char a
--            | Record { testOne   :: Double
--                     , testTwo   :: Bool
--                     , testThree :: D a
--                     } deriving Eq
--   
--   
--   Next we derive the necessary instances. Note that we make use of the
--   feature to change record field names. In this case we drop the first 4
--   characters of every field name. We also modify constructor names by
--   lower-casing them:
--   
--   
--   $(deriveJSON defaultOptions{fieldLabelModifier = drop 4, constructorTagModifier = map toLower} ''D)
--   
--   
--   Now we can use the newly created instances.
--   
--   
--   d :: D Int
--   d = Record { testOne = 3.14159
--              , testTwo = True
--              , testThree = Product "test" 'A' 123
--              }
--   
--   
--   
--   >>> fromJSON (toJSON d) == Success d
--   > True
--   
--   
--   This also works for data family instances, but instead of passing in
--   the data family name (with double quotes), we pass in a data family
--   instance constructor (with a single quote):
--   
--   
--   data family DF a
--   data instance DF Int = DF1 Int
--                        | DF2 Int Int
--                        deriving Eq
--   
--   $(deriveJSON defaultOptions 'DF1)
--   -- Alternatively, one could pass 'DF2 instead
--   
--   
--   Please note that you can derive instances for tuples using the
--   following syntax:
--   
--   
--   -- FromJSON and ToJSON instances for 4-tuples.
--   $(deriveJSON defaultOptions ''(,,,))
--   
module Data.Aeson.TH

-- | Options that specify how to encode/decode your datatype to/from JSON.
data Options
Options :: (String -> String) -> (String -> String) -> Bool -> Bool -> SumEncoding -> Bool -> Options

-- | Function applied to field labels. Handy for removing common record
--   prefixes for example.
[fieldLabelModifier] :: Options -> String -> String

-- | Function applied to constructor tags which could be handy for
--   lower-casing them for example.
[constructorTagModifier] :: Options -> String -> String

-- | If True the constructors of a datatype, with all nullary
--   constructors, will be encoded to just a string with the constructor
--   tag. If False the encoding will always follow the
--   sumEncoding.
[allNullaryToStringTag] :: Options -> Bool

-- | If True record fields with a Nothing value will be
--   omitted from the resulting object. If False the resulting
--   object will include those fields mapping to null.
[omitNothingFields] :: Options -> Bool

-- | Specifies how to encode constructors of a sum datatype.
[sumEncoding] :: Options -> SumEncoding

-- | Hide the field name when a record constructor has only one field, like
--   a newtype.
[unwrapUnaryRecords] :: Options -> Bool

-- | Specifies how to encode constructors of a sum datatype.
data SumEncoding

-- | A constructor will be encoded to an object with a field
--   tagFieldName which specifies the constructor tag (modified by
--   the constructorTagModifier). If the constructor is a record the
--   encoded record fields will be unpacked into this object. So make sure
--   that your record doesn't have a field with the same label as the
--   tagFieldName. Otherwise the tag gets overwritten by the encoded
--   value of that field! If the constructor is not a record the encoded
--   constructor contents will be stored under the contentsFieldName
--   field.
TaggedObject :: String -> String -> SumEncoding
[tagFieldName] :: SumEncoding -> String
[contentsFieldName] :: SumEncoding -> String

-- | A constructor will be encoded to an object with a single field named
--   after the constructor tag (modified by the
--   constructorTagModifier) which maps to the encoded contents of
--   the constructor.
ObjectWithSingleField :: SumEncoding

-- | A constructor will be encoded to a 2-element array where the first
--   element is the tag of the constructor (modified by the
--   constructorTagModifier) and the second element the encoded
--   contents of the constructor.
TwoElemArray :: SumEncoding

-- | Default encoding Options:
--   
--   
--   Options
--   { fieldLabelModifier      = id
--   , constructorTagModifier  = id
--   , allNullaryToStringTag   = True
--   , omitNothingFields       = False
--   , sumEncoding             = defaultTaggedObject
--   }
--   
defaultOptions :: Options

-- | Default TaggedObject SumEncoding options:
--   
--   
--   defaultTaggedObject = TaggedObject
--                         { tagFieldName      = "tag"
--                         , contentsFieldName = "contents"
--                         }
--   
defaultTaggedObject :: SumEncoding

-- | Generates both ToJSON and FromJSON instance declarations
--   for the given data type or data family instance constructor.
--   
--   This is a convienience function which is equivalent to calling both
--   deriveToJSON and deriveFromJSON.
deriveJSON :: Options -> Name -> Q [Dec]

-- | Generates a ToJSON instance declaration for the given data type
--   or data family instance constructor.
deriveToJSON :: Options -> Name -> Q [Dec]

-- | Generates a FromJSON instance declaration for the given data
--   type or data family instance constructor.
deriveFromJSON :: Options -> Name -> Q [Dec]

-- | Generates a lambda expression which encodes the given data type or
--   data family instance constructor as a Value.
mkToJSON :: Options -> Name -> Q Exp

-- | Generates a lambda expression which encodes the given data type or
--   data family instance constructor as a JSON string.
mkToEncoding :: Options -> Name -> Q Exp

-- | Generates a lambda expression which parses the JSON encoding of the
--   given data type or data family instance constructor.
mkParseJSON :: Options -> Name -> Q Exp
instance Data.Aeson.Types.Class.FromJSON a => Data.Aeson.TH.LookupField a
instance Data.Aeson.Types.Class.FromJSON a => Data.Aeson.TH.LookupField (GHC.Base.Maybe a)
