tmp

Data ===> Render
 ^----------|

  * - Syntax separation. i.e. JSON + Mustache Template
  * - No high order logic support between data and rendering languages. i.e:
    the text to be rendered depends on the output format or page size.
  * + swap out rendering format
  * + logic support for data layer

Data <===> Render

  * + marry the data and render syntaxes
  * i.e auto link generation
  * + non-turring complete
  * + types lots of 'em and inference.
  * extensible "markup language" syntax
  * keep all provanence information for output files / derivations (for any
    build system)
    - the most general information is the file system heirarchy of the final
      produced derivation

Nix 

1. Write Text <--|-- Content
1. Create data <-|
1. Create outputs (derivations)

  |-------------------------|
  v--------------|          |
datastructure ~ text ~ (derivation - fs. Hierarchy)

Final Encoding

Module = { text : Text; drvs = ???; a = { text = ???; drvs = ???; } }

text :: Lens Module Text

list :: [Module] -> Module

Text is the language provided by the rendering system.

Conix 

Initial
DhallAeson a -> Text

Final 
type Doc = (Text, Text)

render :: (Text -> a) -> Content2 a -> Content2 a
render r (Markup t) = Rendered (r t)
render _ x = x

data ListType = Enum | Bullet | Ordered
data ListItem = 

final encode
mdList :: [Text] -> Text

  mdList [ (f a) (g b) ... ]

mdList' :: [[Text]] -> [Text]
mdList = pure . mdList . fmap mconcat


1. a derivation at the top of the tree 
  (not needed because not fixing this gives the user more power)
1. 


````````
conix: dir "bar" [(mdFile "foo") (htmlFile "baz")] ()

`````

type Pandoc a
  = TextLit Text
  | BulletList [a]
  | EnumList [a]
  | Table (Map Text [a])
  | Heading Natural a
  | HRule
  | Paragraph [a]
  deriving Functor

type MarkupCodeF a = FreeF a PandocF

type MarkupCode a = Fix (MarkupCodeF a)

label :: Name -> MarkupCode -> MarkupCode
label = Labeled

labelHidden :: Name -> MarkupCode a -> MarkupCode a
labelHidden name = Labeled name . pure

        a             b      
Dir -> (Name, Dir -> (Name, File -> Paragraph [a]
"conix.a.b.c"

data FileHierarchyF a b
  = File RenderType (MarkupCode a)
  | LocalPath FilePath
  | Dir (Map Name b)
  deriving Functor

type FileHierarchy a = Fix (FileHierarchyF a)

type RenderType
  = Html HtmlPandocArgs
  | PDF PDFPandocArgs
  | Markdown

type PureData = NixValue

type LabelledDataF a = FreeF a (Map Name)

type LabelledData = Fix (LabelledDataF a)

type LabeledDataPath = [Name]

-- Good API design: avoid parsing / patching things.

--                   md
-- linkTo "a.b.c.d" ======> "a/b/c.md"
--                  ======> "a/b/c#d"
--                   html

renderCode :: MarkupCode -> FileHierarchy
renderCode = File

Markdown/RST/LaTeX Formatted Text
          |
          V
code :: MarkupCode -> FileHierarchy
code = drv . renderCode

modifyCode :: (MarkupCode -> MarkupCode) -> FileHierarchy -> FileHierarchy
modifyCode = over mds

mds :: Traversal FileHierarchy MarkupCode

toText :: PureData -> MarkupCode

instance Monoid FileHierarchy

instance Monoid Page

-- LabeledDataPath -> Lens FileHierarchy a
get :: LabeledDataPath -> FileHierarchy -> a
set :: LabeledDataPath -> a -> FileHierarchy -> FileHierarchy

(Monoid s) => StateF s a        (In Nix)
  = Get (s -> a) ==========> s -> a (in Nix)
  | Set s a      ==========> { x = a }

evalMarkdown :: Alg MarkupCodeF a r -> MarkupCode a -> r

evalFileHierarchy :: Alg FileHierarchyF a d -> FileHierarchy a -> d

linkTo :: LabeledDataPath -> FileHierarchy -> MarkupCode
linkTo = ???

dir :: DirPath -> [ FileHierarchy ] -> FileHierarchy

file :: Name -> Text -> FileHierarchy

-- r ~ (Derivation, LabelledData)
run :: Alg (FileHierarchyF a) (r -> r) -> (r -> FileHierarchy a) -> r
run alg f = fix (cata alg . f)

      |-------------------------------------|--> Derivation | NixValue
      |                                     |
Evaluated to Create                         |
      |                                     |
---------------------                       v
File System Tree                       |------------|
---------------------                  | Data Tree  |
Content Tree   <--Consumed To Create---|------------|
---------------------