--------------------------------------------------------------------
-- |
-- Module  : Language.Dot.Utils
-- License : GPL-3
--
-- Maintainer  : Marcelo Garlet Millani <marcelogmillani@gmail.com>
-- Stability   : experimental
-- Portability : portable
--
-- Convenience functions for working with DOT.
--------------------------------------------------------------------

module Language.Dot.Utils where

import Language.Dot.Graph
import Data.List
import Data.Maybe

-- | Representation of a graph as a list of nodes and a list of edges.
-- Nodes and edges may occur several times on each list.
adjacency (_,_,_, stmts) = adjacency' [] [] stmts
  where
    adjacency' _ _ [] = ([],[])
    adjacency' nodeAttr edgeAttr (stmt:ss) = 
      case stmt of
        (EdgeStatement subgraphs attributes) -> 
          let sgs = (map (subgraphAdjacency nodeAttr edgeAttr) subgraphs)
              edges = concatMap snd sgs
              nodes = map fst sgs
              pathEdges = makePath ((reverse attributes) ++ edgeAttr) nodes
              (ns, es) = adjacency' nodeAttr edgeAttr ss
          in ((concat nodes) ++ ns, (edges ++ pathEdges) ++ es)
        (NodeStatement name port attributes) -> 
          let (ns, es) = adjacency' nodeAttr edgeAttr ss
          in ((Node (show name) (nodeAttr ++ attributes)) : ns, es)
        (SubgraphStatement subgraph)     -> case subgraph of
          NodeRef name port -> 
            let (ns, es) = adjacency' nodeAttr edgeAttr ss
            in ((Node (show name) nodeAttr) : ns, es)
          Subgraph name stmts -> adjacency' nodeAttr edgeAttr stmts
        (AttributeStatement attribute)   -> adjacency' nodeAttr edgeAttr ss
        (EdgeAttribute attributes)  -> adjacency' nodeAttr ((reverse attributes) ++ edgeAttr) ss
        (NodeAttribute attributes)  -> adjacency' ((reverse attributes) ++ nodeAttr) edgeAttr ss
        (GraphAttribute attributes) -> adjacency' nodeAttr edgeAttr ss
    subgraphAdjacency nodeAttr edgeAttr (NodeRef name port) = ([Node (show name) []], [])
    subgraphAdjacency nodeAttr edgeAttr (Subgraph name stmts) = adjacency' nodeAttr edgeAttr stmts
    makePath edgeAttr [n1] = []
    makePath edgeAttr (n0:n1:ns) = [Edge v0 v1 (reverse edgeAttr) | (Node v0 _) <- n0, (Node v1 _) <- n1] ++ makePath edgeAttr (n1:ns)

-- | Converts a graph represented as a list of nodes and edges to the DOT format.
adjacencyToDot directed name elements = intercalate "\n" $
  [ (if directed then "digraph" else "graph") ++ " \"" ++ fromMaybe "" name ++ "\" {"]
  ++
  map outputElement elements
  ++ ["}"]
  where
    edge = if directed then "->" else "--"
    outputElement (Node name attributes) = " \"" ++ name ++ "\"" ++ if null attributes then ";" else " [" ++ intercalate ", " (map outputAttribute attributes) ++ "];"
    outputElement (Edge v u attributes) = " \"" ++ v ++ "\" " ++ edge ++" \"" ++ u ++ "\"" ++ if null attributes then ";" else " [" ++ intercalate ", " (map outputAttribute attributes) ++ "];"
    outputAttribute (attr, val) = "\"" ++ (show attr) ++ "\" = \"" ++ (show val) ++ "\""