B9.Content.AST

B9 produces not only VM-Images but also text documents such as configuration files required by virtual machines. This module is about creating and merging files containing parsable syntactic structures, such as most configuration files do.

Imagine you would want to create a cloud-init 'user-data' file from a set of 'user-data' snippets which each are valid 'user-data' files in yaml syntax and e.g. a writefiles section. Now the goal is, for b9 to be able to merge these snippets into one, such that all writefiles sections are combined into a single writefile section. Another example is OTP/Erlang sys.config files. This type class is the greatest commonon denominator of types describing a syntax that can be parsed, concatenated e.g. like in the above example and rendered. The actual concatenation operation is the append from Monoid, i.e. like monoid but without the need for an empty element.

Documentation

class Semigroup a => ConcatableSyntax a where

Types of values that can be parsedrendered fromto ByteStrings. This class is used as basis for the ASTish class.

Methods

decodeSyntax

Arguments

:: FilePath

An arbitrary string for error messages that corresponds to a possible input file.

-> ByteString

The raw input to parse

-> Either String a

encodeSyntax :: a -> ByteString

Instances

ConcatableSyntax ByteString

ConcatableSyntax ErlangPropList

ConcatableSyntax YamlObject

class ConcatableSyntax a => ASTish a where

Types of values that describe content, that can be created from an AST.

Methods

fromAST :: (CanRender c, Applicative m, Monad m, MonadIO m, MonadReader Environment m) => AST c a -> m a

Instances

ASTish ErlangPropList

ASTish YamlObject

data AST c a

Describe how to create structured content that has a tree-like syntactic structure, e.g. yaml, JSON and erlang-proplists. The first parameter defines a context into which the AST is embeded, e.g. B9.Content.Generator.Content'. The second parameter defines a specifix syntax, e.g ErlangPropList that the AST value generates.

Constructors

ASTObj [(String, AST c a)]

Create an object similar to a Json object.

ASTArr [AST c a]

An array.

ASTMerge [AST c a]

Merge the nested elements, this is a very powerful tool that allows to combine several inputs in a smart and safe way, e.g. by merging the values of the same fields in yaml objects.

ASTEmbed c

ASTString String

ASTParse SourceFile

AST a

Instances

(Eq c, Eq a) => Eq (AST c a)

(Data c, Data a) => Data (AST c a)

(Read c, Read a) => Read (AST c a)

(Show c, Show a) => Show (AST c a)

(Arbitrary c, Arbitrary a) => Arbitrary (AST c a)

Typeable (* -> * -> *) AST

class CanRender c where

Types of values that can be rendered into a ByteString

Methods

render :: (Functor m, Applicative m, MonadIO m, MonadReader Environment m) => c -> m ByteString

Instances

CanRender Content