var dagre = require('dagre');
var _ = require('lodash');

var MAX_NODES = 100;

var doLayout = function(nodes, edges, width, height, scale, margins) {
    var offsetX = 0 + margins.left;
    var offsetY = 0 + margins.top;
    var g = new dagre.graphlib.Graph({});

    if (_.size(nodes) > MAX_NODES) {
        console.error('Too many nodes for graph layout engine. Limit: ' + MAX_NODES);
        return;
    }

    // configure node margins

    g.setGraph({
        nodesep: scale(2.5),
        ranksep: scale(2.5)
    });

    // add nodes and edges to layout engine

    _.each(nodes, function(node) {
        g.setNode(node.id, {id: node.id, width: scale(0.75), height: scale(0.75)});
    });

    _.each(edges, function(edge) {
        var virtualNodes = edge.source.id === edge.target.id ? 1 : 0;
        g.setEdge(edge.source.id, edge.target.id, {id: edge.id, minlen: virtualNodes});
    });

    dagre.layout(g);

    var graph = g.graph();

    // shifting graph coordinates to center

    if (graph.width < width) {
        offsetX = (width - graph.width) / 2 + margins.left;
    }
    if (graph.height < height) {
        offsetY = (height - graph.height) / 2 + margins.top;
    }

    // apply coordinates to nodes and edges

    g.nodes().forEach(function(id) {
        var node = nodes[id];
        var graphNode = g.node(id);
        node.x = graphNode.x + offsetX;
        node.y = graphNode.y + offsetY;
    });

    g.edges().forEach(function(id) {
        var graphEdge = g.edge(id);
        var edge = edges[graphEdge.id];
        _.each(graphEdge.points, function(point) {
            point.x += offsetX;
            point.y += offsetY;
        });
        edge.points = graphEdge.points;
    });

    // return object with width and height of layout

    return graph;
};

module.exports = {
    doLayout: doLayout
};