typed-encoding-0.2.0.0: Type safe string transformations

Safe HaskellSafe
LanguageHaskell2010

Examples.TypedEncoding.Overview

Contents

Description

type-encoding overview examples.

This library is concerned with 3 main operations done on strings: encoding, decoding, and recovery. Examples in this module cover all of these base cases.

This module uses encoding instances found in

Synopsis

Documentation

>>> :set -XOverloadedStrings -XMultiParamTypeClasses -XDataKinds -XTypeApplications

This module contains some ghci friendly values to play with.

Each value is documented in a doctest style by including an equivalent ghci ready expression. These documents generate a test suite for this library as well.

Basics

helloB64 :: Enc '["enc-B64"] () ByteString Source #

"Hello World" encoded as Base64

>>> helloB64
MkEnc Proxy () "SGVsbG8gV29ybGQ="
>>> displ helloB64
"MkEnc '[enc-B64] () (ByteString SGVsbG8gV29ybGQ=)"
>>> encodeAll . toEncoding () $ "Hello World" :: Enc '["enc-B64"] () B.ByteString
MkEnc Proxy () "SGVsbG8gV29ybGQ="

helloB64Decoded :: ByteString Source #

Previous text decoded from Base64

>>> fromEncoding . decodeAll $ helloB64
"Hello World"

helloB64Recovered :: Either RecreateEx (Enc '["enc-B64"] () ByteString) Source #

recreateFAll allows for recovering data at program boundaries (for example, when parsing JSON input). It makes sure that the content satisfies specified encodings.

>>> recreateFAll . toEncoding () $ "SGVsbG8gV29ybGQ=" :: Either RecreateEx (Enc '["enc-B64"] () B.ByteString)
Right (MkEnc Proxy () "SGVsbG8gV29ybGQ=")
>>> recreateFAll . toEncoding () $ "SGVsbG8gV29ybGQ" :: Either RecreateEx (Enc '["enc-B64"] () B.ByteString)
Left (RecreateEx "enc-B64" ("invalid padding"))

The above example start by placing payload in zero-encoded Enc '[] () type and then apply recreateFAll this is a good way to recreate encoded type if encoding is known.

If is it not, UncheckedEnc type can be used.

(See ToEncString for better example).

This module is concerned only with the first approach.

>>> let unchecked = toUncheckedEnc ["enc-B64"] () ("SGVsbG8gV29ybGQ=" :: T.Text)
>>> verifyUncheckedEnc' @'["enc-B64"] unchecked
Just (Right (MkEnc Proxy () "SGVsbG8gV29ybGQ="))

helloB64B64 :: Enc '["enc-B64", "enc-B64"] () ByteString Source #

"Hello World" double-Base64 encoded. Notice the same code used as in single encoding, the game is played at type level.

>>> encodeAll . toEncoding () $ "Hello World" :: Enc '["enc-B64","enc-B64"] () B.ByteString
MkEnc Proxy () "U0dWc2JHOGdWMjl5YkdRPQ=="
>>> displ helloB64B64
"MkEnc '[enc-B64,enc-B64] () (ByteString U0dWc2JHOGdWMjl5YkdRPQ==)"

helloB64B64PartDecode :: Enc '["enc-B64"] () ByteString Source #

Double Base64 encoded "Hello World" with one layer of encoding removed

>>> decodePart @'["enc-B64"] $ helloB64B64 :: Enc '["enc-B64"] () B.ByteString
MkEnc Proxy () "SGVsbG8gV29ybGQ="
>>> helloB64B64PartDecode == helloB64
True

helloB64B64Decoded :: ByteString Source #

helloB64B64 all the way to ByteString

Notice a similar polymorphism in decoding.

>>> fromEncoding . decodeAll $ helloB64B64 :: B.ByteString
"Hello World"

We can also decode all the parts:

>>> fromEncoding . decodePart @'["enc-B64","enc-B64"] $ helloB64B64
"Hello World"

helloB64B64RecoveredErr :: Either RecreateEx (Enc '["enc-B64", "enc-B64"] () ByteString) Source #

what happens when we try to recover encoded once text to Enc '["enc-B64", "enc-B64"].

Again, notice the same expression is used as in previous recovery.

>>> recreateFAll . toEncoding () $ "SGVsbG8gV29ybGQ=" :: Either RecreateEx (Enc '["enc-B64", "enc-B64"] () B.ByteString)
Left (RecreateEx "enc-B64" ("invalid padding"))

"do-" Encodings

helloUPP :: Enc '["do-UPPER"] () Text Source #

"do-UPPER" (from Sample module) encoding applied to "Hello World"

Notice a namespace thing going on, "enc-" is encoding, "do-" is some transformation. These are typically not reversible, some could be recoverable.

The same code is used as in "enc-" examples to encode (now transform).

>>> encodeAll . toEncoding () $ "Hello World" :: Enc '["do-UPPER"] () T.Text
MkEnc Proxy () "HELLO WORLD"

helloTitleRev :: Enc '["do-reverse", "do-Title"] () Text Source #

Sample compound transformation

>>> encodeAll . toEncoding () $ "HeLLo world" :: Enc '["do-reverse", "do-Title"] () T.Text
MkEnc Proxy () "dlroW olleH" 

Configuration

newtype Config Source #

Example configuration

Constructors

Config 

Fields

Instances
Show Config Source # 
Instance details

Defined in Examples.TypedEncoding.Overview

HasA SizeLimit Config Source # 
Instance details

Defined in Examples.TypedEncoding.Overview

Methods

has :: Config -> SizeLimit Source #

helloTitle :: Enc '["do-Title"] Config Text Source #

helloTitle is needed in following examples

helloRevLimit :: Enc '["do-size-limit", "do-reverse", "do-Title"] Config Text Source #

Configuration can be used to impact the encoding process.

So far we had used () as configuration of all encodings. But since both "do-reverse", "do-Title" are polymorphic in configuration we can also do this:

>>> encodeAll . toEncoding exampleConf $ "HeLLo world" :: Enc '["do-reverse", "do-Title"] Config T.Text
MkEnc Proxy (Config {sizeLimit = SizeLimit {unSizeLimit = 8}}) "dlroW olleH"
>>> encodeAll . toEncoding exampleConf $ "HeLlo world" :: Enc '["do-size-limit", "do-reverse", "do-Title"] Config T.Text
MkEnc Proxy (Config {sizeLimit = SizeLimit {unSizeLimit = 8}}) "dlroW ol"

Instead, encode previously defined helloTitle by reversing it and adding size limit

>>> encodePart @'["do-size-limit", "do-reverse"] helloTitle :: Enc '["do-size-limit", "do-reverse", "do-Title"] Config T.Text
MkEnc Proxy (Config {sizeLimit = SizeLimit {unSizeLimit = 8}}) "dlroW ol"

helloLimitB64 :: Enc '["enc-B64", "do-size-limit"] Config ByteString Source #

helloRevLimitParDec :: Enc '["do-size-limit"] Config ByteString Source #

... and we unwrap the B64 part only

>>> decodePart @'["enc-B64"] $ helloLimitB64
MkEnc Proxy (Config {sizeLimit = SizeLimit {unSizeLimit = 8}}) "HeLlo wo"

"r-" encodings section

helloAscii :: Either EncodeEx (Enc '["r-ASCII"] () ByteString) Source #

ASCII char set ByteStrings are sequences of Bytes (Word8). The type is very permissive, it may contain binary data such as jpeg picture.

"r-ASCII" encoding acts as partial identity function it does not change any bytes in bytestring but it fails if a byte is outside of ASCII range (in Either monad).

Note naming thing: "r-" is partial identity ("r-" is from restriction).

>>> encodeFAll . toEncoding () $ "HeLlo world" :: Either EncodeEx (Enc '["r-ASCII"] () B.ByteString)
Right (MkEnc Proxy () "HeLlo world")

helloAsciiB64 :: Either EncodeEx (Enc '["enc-B64", "r-ASCII"] () ByteString) Source #

Arguably the type we used for helloB64 was too permissive. a better version is here:

>>> encodeFAll . toEncoding () $ "Hello World" :: Either EncodeEx (Enc '["enc-B64", "r-ASCII"] () B.ByteString)
Right (MkEnc Proxy () "SGVsbG8gV29ybGQ=") 

helloAsciiB64PartDec :: Either EncodeEx (Enc '["r-ASCII"] () ByteString) Source #

>>> decodePart @'["enc-B64"] <$> helloAsciiB64
Right (MkEnc Proxy () "Hello World")