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+{- a simple graphviz / dot(1) digraph description generator library
+ -
+ - Copyright 2010 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Dot where -- import qualified
+
+{- generates a graph description from a list of lines -}
+graph :: [String] -> String
+graph s = unlines $ [header] ++ s ++ [footer]
+	where
+		header = "digraph map {"
+		footer= "}"
+
+{- a node in the graph -}
+graphNode :: String -> String -> String
+graphNode nodeid desc = lineLabeled desc $ quote nodeid
+
+{- an edge between two nodes -}
+graphEdge :: String -> String -> Maybe String -> String
+graphEdge fromid toid d =
+	case d of
+		Nothing -> line edge
+		Just desc -> lineLabeled desc edge
+	where
+		edge = quote fromid ++ " -> " ++ quote toid
+
+quote :: String -> String
+quote s = "\"" ++ s ++ "\""
+
+line :: String -> String
+line s = "\t" ++ s ++ ";"
+
+{- a line with a label -}
+lineLabeled :: String -> String -> String
+lineLabeled label s = line $ s ++ " [ label=" ++ quote label ++ " ]"
+
+{- apply to graphNode to put the node in a labeled box -}
+subGraph :: String -> String -> String -> String
+subGraph subid label s = line $
+	"subgraph " ++ name ++ "{\n" ++ setlabel ++ "\n" ++ s ++ "\n}"
+	where
+		-- the "cluster_" makes dot draw a box
+		name = quote ("cluster_" ++ subid)
+		setlabel = line $ "label=" ++ quote label