graphs.elm

import Html
import Svg exposing (..)
import Svg.Attributes exposing (..)
import Graphics.Element exposing (show)
import Dict


empty = {nodes = Dict.empty, nodeData = Dict.empty, edgeData = Dict.empty}
emptyNode = {from = [], to = []}
                  
addNode id g = {g | nodes = Dict.insert id emptyNode g.nodes}
addNodeData id data g =
  let g = addNode id g
  in {g | nodeData = Dict.insert id data g.nodeData}

addEdge id1 id2 g =
  let
    up from maybeNode =
      let node = Maybe.withDefault emptyNode maybeNode
      in Just {node |
        from = if from  then id1 :: node.from else node.from,
        to   = if from then node.to   else id2 :: node.to
      }
  in {g | nodes = Dict.update id1 (up True) <| Dict.update id2 (up False) g.nodes}

addEdgeData id1 id2 data g =
  let g = addEdge id1 id2 g
  in {g | edgeData = Dict.insert (id1,id2) data g.edgeData}

listNodes g = List.map (\n -> (n, Dict.get n g.nodeData)) <| Dict.keys g.nodes

graph = addEdgeData "Hello" "World" 2
        <| addNodeData "World" (900,15)
        <| addNodeData "Hello" (90,150)
        <| empty

point x y = let (x, y) = (toString x, toString y) in circle [cx x, cy y, r "10"] []

main = svg [width "1000", height "1000"]
  (List.map (\(c, d) -> let (x,y) = Maybe.withDefault (0,0) d in point x y) (listNodes graph))