// graph.js

document.addEventListener('DOMContentLoaded', function() {
    const data = {
        nodes: [
            { id: "Force", label: "Force" },
            { id: "Mass", label: "Mass" },
            { id: "Acceleration", label: "Acceleration" },
            { id: "Gravity", label: "Gravity" },
            { id: "Friction", label: "Friction" },
            { id: "Motion", label: "Motion" }
        ],
        links: [
            { source: "Force", target: "Mass", relationship: "is_applied_on" },
            { source: "Force", target: "Acceleration", relationship: "causes" },
            { source: "Gravity", target: "Mass", relationship: "acts_on" },
            { source: "Friction", target: "Motion", relationship: "opposes" },
            { source: "Force", target: "Friction", relationship: "overcomes" }
        ]
    };

    const width = 800;
    const height = 600;

    const svg = d3.select("#graph").append("svg")
        .attr("width", width)
        .attr("height", height);

    const simulation = d3.forceSimulation(data.nodes)
        .force("link", d3.forceLink(data.links).id(d => d.id).distance(200))
        .force("charge", d3.forceManyBody().strength(-500))
        .force("center", d3.forceCenter(width / 2, height / 2));

    const link = svg.append("g")
        .attr("stroke", "#999")
        .attr("stroke-opacity", 0.6)
        .selectAll("line")
        .data(data.links)
        .enter().append("line")
        .attr("stroke-width", d => Math.sqrt(d.value));

    const node = svg.append("g")
        .attr("stroke", "#fff")
        .attr("stroke-width", 1.5)
        .selectAll("circle")
        .data(data.nodes)
        .enter().append("circle")
        .attr("r", 10)
        .attr("fill", "red")
        .call(d3.drag()
            .on("start", dragstarted)
            .on("drag", dragged)
            .on("end", dragended));

    node.append("title")
        .text(d => d.id);

    // Add labels
    const labels = svg.append("g")
        .selectAll("text")
        .data(data.nodes)
        .enter().append("text")
        .attr("x", d => d.x)
        .attr("y", d => d.y)
        .attr("dy", -3)
        .attr("text-anchor", "middle")
        .text(d => d.label);

    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);
    });

    function dragstarted(event, d) {
        if (!event.active) simulation.alphaTarget(0.3).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;
    }
});