roadmap/assets/js/graph.js

async function drawGraph(url, baseUrl, pathColors, depth, enableDrag, enableLegend, enableZoom) {
    const { index, links, content } = await fetchData
    const curPage = url.replace(baseUrl, "")
  
    const parseIdsFromLinks = (links) => [...(new Set(links.flatMap(link => ([link.source, link.target]))))]
  
    const neighbours = new Set()
    const wl = [curPage || "/", "__SENTINEL"]
    if (depth >= 0) {
      while (depth >= 0 && wl.length > 0) {
        // compute neighbours
        const cur = wl.shift()
        if (cur === "__SENTINEL") {
          depth--
          wl.push("__SENTINEL")
        } else {
          neighbours.add(cur)
          const outgoing = index.links[cur] || []
          const incoming = index.backlinks[cur] || []
          wl.push(...outgoing.map(l => l.target), ...incoming.map(l => l.source))
        }
      }
    } else {
      parseIdsFromLinks(links).forEach(id => neighbours.add(id))
    }
  
    const data = {
      nodes: [...neighbours].map(id => ({id})),
      links: links.filter(l => neighbours.has(l.source) && neighbours.has(l.target)),
    }
  
    const color = (d) => {
      if (d.id === curPage || (d.id === "/" && curPage === "")) {
        return "var(--g-node-active)"
      }
  
      for (const pathColor of pathColors) {
        const path = Object.keys(pathColor)[0]
        const colour = pathColor[path]
        if (d.id.startsWith(path)) {
          return colour
        }
      }
  
      return "var(--g-node)"
    }
  
    const drag = simulation => {
      function dragstarted(event, d) {
        if (!event.active) simulation.alphaTarget(1).restart();
        d.fx = d.x;
        d.fy = d.y;
      }
  
      function dragged(event,d) {
        d.fx = event.x;
        d.fy = event.y;
      }
  
      function dragended(event,d) {
        if (!event.active) simulation.alphaTarget(0);
        d.fx = null;
        d.fy = null;
      }
  
      const noop = () => {}
      return d3.drag()
        .on("start", enableDrag ? dragstarted : noop)
        .on("drag", enableDrag ? dragged : noop)
        .on("end", enableDrag ? dragended : noop);
    }
  
    const height = 250
    const width = document.getElementById("graph-container").offsetWidth
  
    const simulation = d3.forceSimulation(data.nodes)
      .force("charge", d3.forceManyBody().strength(-30))
      .force("link", d3.forceLink(data.links).id(d => d.id))
      .force("center", d3.forceCenter());
  
    const svg = d3.select('#graph-container')
      .append('svg')
      .attr('width', width)
      .attr('height', height)
      .attr("viewBox", [-width / 2, -height / 2, width, height]);
  
    if (enableLegend) {
      const legend = [
        {"Current": "var(--g-node-active)"},
        {"Note": "var(--g-node)"},
        ...pathColors
      ]
      legend.forEach((legendEntry, i) => {
        const key = Object.keys(legendEntry)[0]
        const colour = legendEntry[key]
        svg.append("circle").attr("cx", -width/2 + 20).attr("cy", height/2 - 30 * (i+1)).attr("r", 6).style("fill", colour)
        svg.append("text").attr("x", -width/2 + 40).attr("y", height/2 - 30 * (i+1)).text(key).style("font-size", "15px").attr("alignment-baseline","middle")
      })
    }
  
    // draw links between nodes
    const link = svg.append("g")
      .selectAll("line")
      .data(data.links)
      .join("line")
      .attr("class", "link")
      .attr("stroke", "var(--g-link)")
      .attr("stroke-width", 2)
      .attr("data-source", d => d.source.id)
      .attr("data-target", d => d.target.id)
  
    // svg groups
    const graphNode = svg.append("g")
      .selectAll("g")
      .data(data.nodes)
      .enter().append("g")
  
    // draw individual nodes
    const node = graphNode.append("circle")
      .attr("class", "node")
      .attr("id", (d) => d.id)
      .attr("r", (d) => {
        const numOut = index.links[d.id]?.length || 0
        const numIn = index.backlinks[d.id]?.length || 0
        return 3 + (numOut + numIn) / 4
      })
      .attr("fill", color)
      .style("cursor", "pointer")
      .on("click", (_, d) => {
        window.location.href = baseUrl + '/' + decodeURI(d.id).replace(/\s+/g, '-')
      })
      .on("mouseover", function (_, d) {
        d3.selectAll(".node")
          .transition()
          .duration(100)
          .attr("fill", "var(--g-node-inactive)")
  
        const neighbours = parseIdsFromLinks([...(index.links[d.id] || []), ...(index.backlinks[d.id] || [])])
        const neighbourNodes = d3.selectAll(".node").filter(d => neighbours.includes(d.id))
        const currentId = d.id
        const linkNodes = d3.selectAll(".link").filter(d => d.source.id === currentId || d.target.id === currentId)
  
        // highlight neighbour nodes
        neighbourNodes
          .transition()
          .duration(200)
          .attr("fill", color)
  
        // highlight links
        linkNodes
          .transition()
          .duration(200)
          .attr("stroke", "var(--g-link-active)")
  
        // show text for self
        d3.select(this.parentNode)
          .select("text")
          .raise()
          .transition()
          .duration(200)
          .style("opacity", 1)
      }).on("mouseleave", function (_,d) {
        d3.selectAll(".node")
          .transition()
          .duration(200)
          .attr("fill", color)
  
        const currentId = d.id
        const linkNodes = d3.selectAll(".link").filter(d => d.source.id === currentId || d.target.id === currentId)
  
        linkNodes
          .transition()
          .duration(200)
          .attr("stroke", "var(--g-link)")
  
        d3.select(this.parentNode)
          .select("text")
          .transition()
          .duration(200)
          .style("opacity", 0)
      })
      .call(drag(simulation));
  
    // draw labels
    const labels = graphNode.append("text")
      .attr("dx", 12)
      .attr("dy", ".35em")
      .text((d) => content[decodeURI(d.id).replace(/\s+/g, '-')]?.title || "Untitled")
      .style("opacity", 0)
      .style("pointer-events", "none")
      .call(drag(simulation));
  
    // set panning
  
    if (enableZoom) {
      svg.call(d3.zoom()
        .extent([[0, 0], [width, height]])
        .scaleExtent([0.25, 4])
        .on("zoom", ({transform}) => {
          link.attr("transform", transform);
          node.attr("transform", transform);
          labels.attr("transform", transform);
        }));
    }
  
    // progress the simulation
    simulation.on("tick", () => {
      link
        .attr("x1", d => d.source.x)
        .attr("y1", d => d.source.y)
        .attr("x2", d => d.target.x)
        .attr("y2", d => d.target.y)
      node
        .attr("cx", d => d.x)
        .attr("cy", d => d.y)
      labels
        .attr("x", d => d.x)
        .attr("y", d => d.y)
    });
  }