TU_Assignment/frontend/assets/js/canvas.js

const canvas = document.getElementById("canvas");

//-----------------------------------------------------------------------------
//-----------------------------Layouts-----------------------------------------
//-----------------------------------------------------------------------------
var width = canvas.offsetWidth;
var height = canvas.offsetHeight;

const node_size = 55;

var stage = new Konva.Stage({
    container: canvas,
    width: width,
    height: height
});

const node_layout = {
    radius: node_size,
    fill: 'white',
    stroke: 'black',
    strokeWidth: 2,
    shadowColor: 'black',
    shadowBlur: 10,
    shadowOffset: {
        x: 2,
        y: 2
    },
    shadowOpacity: 0.3,
};

const node_text_layout = {
    x: 1 - node_size,
    y: 2 - node_size,
    text: name,
    fontSize: 22,
    width: 2 * node_size - 1,
    height: 2 * node_size - 1,
    fontFamily: 'Roboto, Arial, Verdana, sans-serif',
    fill: 'black',
    verticalAlign: 'middle',
    align: 'center'
};

const edge_layout = {
    stroke: 'black',
    strokeWidth: 3,
}

const edge_text_layout = {
    fontSize: 22,
    width: 2 * node_size,
    height: 2 * node_size,
    fontFamily: 'Roboto, Arial, Verdana, sans-serif',
    fill: 'black',
    verticalAlign: 'middle',
    align: 'center'
};


//-----------------------------------------------------------------------------
//-------------------------------Init------------------------------------------
//-----------------------------------------------------------------------------
var edge_layer = new Konva.Layer();
var node_layer = new Konva.Layer();

var konva_edges = [];
var konva_nodes = [];

var graph_copy = {};

var state = "idle";

// selected nodes
var selected = [];
var path_elements = [];

// (additions) auto layout
var auto_layout = false;

function initialization() {
    stage.add(edge_layer);
    stage.add(node_layer);
    // avoid flickering
    edge_layer.hide();

    // draw initial graph
    for (id in nodes) {
      draw_new_node(nodes[id], node_size + Math.random() * (width - 2 * node_size), node_size + Math.random() * (height - 2 * node_size));
    }
    for (id in edges) {
      draw_new_edge(edges[id]);
    }

    // (additions) auto layout
    if (sessionStorage.getItem("auto_layout") !== null) {
      // Restore the contents of the text field
      auto_layout = (sessionStorage.getItem("auto_layout") == 'true');
      if (auto_layout) {
        document.querySelector("[data-activeon=auto_layout]").classList.add("active");
      }
    }
    // Precalculate a good graph presentation
    for (var i = 0; i < 1000; i++) {
      force_directed_graph();
    }
    edge_layer.show();
    node_layer.draw();
}



//-----------------------------------------------------------------------------
//------------------------------utils------------------------------------------
//-----------------------------------------------------------------------------
function sort(array) {
  return array.sort(function(a, b) {
    return a - b;
  })
}

function show_error(msg) {
  let infobar = document.querySelector("#infobar");
  infobar.innerHTML = msg;
  infobar.classList.add("active");
  window.setTimeout(function() {
    infobar.classList.remove("active");
  }, 4000);
}


//-----------------------------------------------------------------------------
//---------------------------draw methods--------------------------------------
//-----------------------------------------------------------------------------
function draw_new_node(name, x, y) {
  let group = new Konva.Group({
    x: x,
    y: y,
    dragDistance: 5,
    draggable: true,
    dragBoundFunc: function(pos) {
      return {
        x: sort([node_size, pos.x, width - node_size])[1],
        y: sort([node_size, pos.y, height - node_size])[1],
      };
    },
    id: name
  });
  let box = new Konva.Circle(node_layout);
  let simpleText = new Konva.Text({
    ...node_text_layout,
    text: name
  });
  group.add(box);
  group.add(simpleText);
  group.on("click", on_node_click);
  group.on('tap', on_node_click);
  group.on('dragstart', function() {
    group.attrs.dragging = true;
  });
  group.on('dragend', function() {
    group.attrs.dragging = false;
  });
  group.on('mouseover', function() {
    document.body.style.cursor = 'pointer';
  });
  group.on('mouseout', function() {
    document.body.style.cursor = 'default';
  });
  graph_copy[name] = [];
  konva_nodes.push(group);

  node_layer.add(group);
  node_layer.draw();
}


function draw_new_edge(edge) {
  let start_node = stage.findOne('#' + edge["start"]);
  let end_node = stage.findOne('#' + edge["end"]);
  let weight = edge["weight"];
  let group = new Konva.Group({
    start_node: start_node,
    end_node: end_node,
    weight: weight,
    id: edge["start"] + edge["end"]
  });
  let line = new Konva.Line(edge_layout);
  let simpleText = new Konva.Text({
    ...edge_text_layout,
    text: ""+weight
  });

  graph_copy[edge["start"]].push(edge["end"]);
  graph_copy[edge["end"]].push(edge["start"]);

  group.add(line);
  group.add(simpleText);
  konva_edges.push(group);
  update_edge(group);

  edge_layer.add(group);
  edge_layer.draw();

  return group;
}

function update_edge(konva_edge) {
  let line = konva_edge.children[0];
  let text = konva_edge.children[1];
  let start_node = konva_edge.attrs.start_node;
  let end_node = konva_edge.attrs.end_node;
  let size = 15 + text.text().length * 15;
  let line_length = Math.sqrt((start_node.getX() - end_node.getX()) ** 2 + (start_node.getY() - end_node.getY()) ** 2) - size;

  line.points([start_node.getX(), start_node.getY(), end_node.getX(), end_node.getY()]);
  line.dash([line_length / 2, size, line_length / 2]);
  text.x((start_node.getX() + end_node.getX()) / 2 - node_size);
  text.y((start_node.getY() + end_node.getY()) / 2 - node_size),

  edge_layer.draw();
}

function reset_node_style() {
  for (let id in konva_nodes) {
    konva_nodes[id].children[0].strokeWidth(node_layout.strokeWidth);
    konva_nodes[id].children[0].stroke("black");
  }
}

function reset_edge_style() {
  for (let id in konva_edges) {
    konva_edges[id].children[0].strokeWidth(edge_layout.strokeWidth);
    konva_edges[id].children[0].stroke("black");
  }
}

function draw_selected_nodes() {
  reset_node_style();
  reset_edge_style();
  for (let id in selected) {
    selected[id].children[0].strokeWidth(node_layout.strokeWidth+1);
    selected[id].children[0].stroke("rgb(240, 141, 25)");
  }
  node_layer.draw();
}

function draw_path(path) {
  let path_elements = [];
  for (let id in path) {
    path_elements.push(stage.findOne("#" + path[id]));
    if (id == 0) {
      continue
    }
    let current_edge = stage.findOne("#" + path[id - 1] + path[id]);
    if (current_edge) {
      path_elements.push(current_edge);
    } else {
      path_elements.push(stage.findOne("#" + path[id] + path[id - 1]));
    }
  }
  reset_node_style();
  reset_edge_style();
  for (let id in path_elements) {
    path_elements[id].children[0].strokeWidth(node_layout.strokeWidth + 1);
    path_elements[id].children[0].stroke("rgb(240, 141, 25)");
  }
}

function on_node_click(e) {
  e.cancelBubble = true;
  // let mousePos = stage.getPointerPosition();
  let idx = selected.indexOf(this);
  if (idx >= 0) {
    selected.splice(idx, 1);
  } else if (selected.length < 2) {
    selected.push(this);
  } else {
    selected.shift();
    selected.push(this);
  }
  draw_selected_nodes();
};

//-----------------------------------------------------------------------------
//---------------------------REST methods--------------------------------------
//-----------------------------------------------------------------------------
function post(endpoint, data) {
  return fetch(url + endpoint, {
    method: 'POST',
    body: JSON.stringify(data),
    headers: {
      'Content-Type': 'application/json'
    }
  }).then(res => res.json())
}

function create_node() {
  if (state != "create_node") {
    state = "create_node";
    // let mousePos = stage.getPointerPosition();
    let pos = {
      x: (Math.random()-0.5)*node_size*4+width / 2,
      y: (Math.random()-0.5)*node_size*4+height / 2
    };
    create_input(pos.x, pos.y).then(function(text) {
      post("nodes", {
          name: text
        })
        .then(function(res) {
          if (res["error"]) {
            show_error(res["error"])
          } else {
            draw_new_node(text, pos.x, pos.y);
          }
          state = "idle";
        })
        .catch(error => console.error('Error:', error));
    }, function() {state = "idle"});
  }
}

function create_edge() {
  if (selected.length < 2) {
    show_error("Select at least 2 nodes.");
    return;
  }
  let x = (selected[0].getX() + selected[1].getX()) / 2;
  let y = (selected[0].getY() + selected[1].getY()) / 2;
  create_input(x, y).then(function(text) {
    post("edges", {
        start: selected[0].id(),
        end: selected[1].id(),
        weight: text
      })
      .then(function(res) {
        if (res["error"]) {
          show_error(res["error"])
        } else {
          draw_new_edge({
            "start": selected[0].children[1].text(),
            "end": selected[1].children[1].text(),
            "weight": text
          });
          selected = [];
          draw_selected_nodes();
        }
      })
      .catch(error => console.error('Error:', error));

  }, function() {});
}

function create_input(x, y) {
  return new Promise(function(resolve, reject) {
    var container = document.createElement("div");
    container.classList.add("background");
    var input = document.createElement("input");
    var clear = function() {
      container.remove();
      stage.listening(true);
      focus = true;
    }
    input.setAttribute("type", "text");
    input.style.left = x + "px";
    input.style.top = y + "px";
    canvas.appendChild(container);
    container.appendChild(input);
    input.focus();
    stage.listening(false);
    focus = false;
    window.addEventListener("keyup", function(event) {
      if (event.key === "Escape") {
        reject();
        clear();
      }
    });
    input.addEventListener("keyup", function(event) {
      if (event.key === "Enter") {
        resolve(input.value);
        clear();
      }
    });
  });
}

function find_path(data) {
  if (data.length < 2) {
    show_error("Select at least 2 nodes.");
    return;
  }
  fetch(url + "paths/" + data[0].attrs.id + "/" + data[1].attrs.id).then(res => res.json())
    .then(function(res) {
      if (res["error"]) {
        show_error(res["error"]);
      } else {
        selected = [];
        draw_path(res["path"]);
      }
    })
    .catch(error => console.error('Error:', error));
}


//-----------------------------------------------------------------------------
//------------------------background methods-----------------------------------
//-----------------------------------------------------------------------------
function update_edges(edges) {
  for (id in edges) {
    update_edge(edges[id]);
  }
}

node_layer.on('beforeDraw', function() {
  update_edges(konva_edges);
});

// adapt the stage on any window resize
function fitStageIntoParentContainer() {
  width = canvas.offsetWidth;
  height = canvas.offsetHeight;
  stage.width(canvas.offsetWidth);
  stage.height(canvas.offsetHeight);
  stage.draw();
}
window.addEventListener('resize', fitStageIntoParentContainer);


//---------------------(additions) auto layout---------------------------------
function toggle_auto_layout() {
  auto_layout = !auto_layout;
  document.querySelector("[data-activeon=auto_layout]").classList.toggle("active");
  sessionStorage.setItem("auto_layout", auto_layout);
}

function normalize(vec) {
  let l = Math.sqrt(vec[0] ** 2 + vec[1] ** 2);
  if (l == 0){
    return [vec[0], vec[1]];
  }
  return [vec[0] / l, vec[1] / l];
}

function in_edges(start_node, end_node) {
  let idx = graph_copy[start_node.attrs.id].indexOf(end_node.attrs.id);
  if (idx < 0) {
    return false;
  }
  return true;
}

function force_directed_graph(spring_length = 300, step = 0.004) {
  for (var idx in konva_nodes) {
    if (konva_nodes[idx].attrs.dragging) {
      continue
    }
    var x1 = konva_nodes[idx].getX();
    var y1 = konva_nodes[idx].getY();

    var rep = [0, 0];
    var attr = [0, 0];
    for (let jdx in konva_nodes) {
      if (idx == jdx) {
        continue;
      }

      let x2 = konva_nodes[jdx].getX();
      let y2 = konva_nodes[jdx].getY();
      let dir = normalize([x2 - x1, y2 - y1]);
      let dist = Math.sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2);
      if (dist == 0){
        continue;
      }
      if (in_edges(konva_nodes[idx], konva_nodes[jdx])) {
        let f = (dist**2 / spring_length);
        attr[0] += f * dir[0];
        attr[1] += f * dir[1];
      }
      if (dist < width*0.4){
        let f = (spring_length ** 2 / dist);
        rep[0] -= f * dir[0];
        rep[1] -= f * dir[1];
      }
    }
    let new_x = x1 + step * (rep[0] + attr[0]);
    let new_y = y1 + step * (rep[1] + attr[1]);
    if (new_x < 2 * node_size) {
      new_x += 10 * step * ((2 * node_size - new_x));
    } else if (new_x > width - 2 * node_size) {
      new_x += 10 * step * ((width - 2 * node_size - new_x));
    }
    if (new_y < 2 * node_size) {
      new_y += 10 * step * ((2 * node_size - new_y));
    } else if (new_y > height - 2 * node_size) {
      new_y += 10 * step * ((height - 2 * node_size - new_y));
    }
    konva_nodes[idx].x(new_x);
    konva_nodes[idx].y(new_y);
  }
}

var anim = new Konva.Animation(function(frame) {
  if (auto_layout && focus) {
    const step = 0.00025 * frame.timeDiff;
    let spring_factor = Math.min((konva_edges.length+konva_nodes.length-3)/20, 1);
    force_directed_graph(150+(1-spring_factor)*180, step);
  }
}, node_layer);
anim.start();

initialization();

// bug: this avoids glitches
window.onfocus = function() {focus = true;};
window.onblur = function() {focus = false;};