script.js

document.addEventListener('DOMContentLoaded', () => {
    // Components data structure
    const components = {
        magnets: [],
        coils: [],
        cores: [],
        wires: [],
        batteries: [],
        switches: []
    };

    let selectedComponent = null;
    let isDrawingWire = false;
    let wireStartPoint = null;
    let currentWirePoints = [];
    const canvas = document.getElementById('fieldCanvas');
    if (!canvas) return;
    
    const ctx = canvas.getContext('2d');
    const overlay = document.getElementById('component-overlay');
    
    // Set canvas to full size of container
    function resizeCanvas() {
const container = document.getElementById('visualization-container');
        canvas.width = container.clientWidth;
        canvas.height = container.clientHeight;
        drawField();
    }
    
    // Initial resize
    resizeCanvas();
    window.addEventListener('resize', resizeCanvas);
    // Draw magnetic field lines and components
    function drawField() {
        ctx.clearRect(0, 0, canvas.width, canvas.height);
        // Draw wires first (background)
        components.wires.forEach(wire => {
if (wire.points.length < 2) return;
            
            ctx.strokeStyle = '#3b82f6';
            ctx.lineWidth = 3;
            ctx.beginPath();
            ctx.moveTo(wire.points[0].x, wire.points[0].y);
            
            for (let i = 1; i < wire.points.length; i++) {
                ctx.lineTo(wire.points[i].x, wire.points[i].y);
            }
            
            ctx.stroke();
        });

        // Draw other components
        [...components.magnets, ...components.coils, ...components.cores, 
         ...components.batteries, ...components.switches].forEach(comp => {
            const x = comp.x * canvas.width;
            const y = comp.y * canvas.height;
            const radius = 20 + (comp.strength || 0.5) * 30;
            
            // Highlight selected component
            if (selectedComponent === comp) {
                ctx.strokeStyle = '#f59e0b';
                ctx.lineWidth = 3;
                ctx.beginPath();
                ctx.arc(x, y, radius + 5, 0, Math.PI * 2);
                ctx.stroke();
            }

            // Component body
            ctx.fillStyle = getComponentColor(comp.type, comp);
            ctx.beginPath();
            
            if (comp.type === 'magnet') {
                ctx.arc(x, y, radius, 0, Math.PI * 2);
                // Polarity indicator
                ctx.fillStyle = '#ffffff';
                ctx.font = 'bold 16px Arial';
                ctx.textAlign = 'center';
                ctx.textBaseline = 'middle';
                ctx.fillText(comp.polarity > 0 ? 'N' : 'S', x, y);
            } else if (comp.type === 'coil') {
                // Draw coil as concentric circles
                for (let i = 0; i < 3; i++) {
                    ctx.beginPath();
                    ctx.arc(x, y, radius - i*5, 0, Math.PI * 2);
                    ctx.stroke();
                }
            } else {
                // Default rectangular component
                ctx.roundRect(x - radius, y - radius, radius*2, radius*2, 5);
            }
            
            ctx.fill();
        });
// Draw field lines
        ctx.strokeStyle = 'rgba(16, 185, 129, 0.7)';
        ctx.lineWidth = 2;
        
        const steps = 36;
        const lineSteps = 100;
        const stepSize = 5;
        
        for (let i = 0; i < steps; i++) {
            const angle = (i / steps) * Math.PI * 2;
        components.magnets.forEach(magnet => {
let x = magnet.x * canvas.width + Math.cos(angle) * 30;
                let y = magnet.y * canvas.height + Math.sin(angle) * 30;
                
                ctx.beginPath();
                ctx.moveTo(x, y);
                
                for (let j = 0; j < lineSteps; j++) {
                    // Calculate field direction at this point
                    let fx = 0, fy = 0;
            components.magnets.forEach(m => {
const dx = x - m.x * canvas.width;
                        const dy = y - m.y * canvas.height;
                        const distSq = dx * dx + dy * dy;
                        const dist = Math.sqrt(distSq);
                        const force = m.strength * 1000 * m.polarity / (distSq + 100);
                        
                        fx += force * dx / dist;
                        fy += force * dy / dist;
                    });
                    
                    // Normalize direction
                    const len = Math.sqrt(fx * fx + fy * fy);
                    if (len > 0) {
                        fx = fx / len * stepSize;
                        fy = fy / len * stepSize;
                    }
                    
                    x += fx;
                    y += fy;
                    
                    ctx.lineTo(x, y);
                    
                    // Stop if out of bounds
                    if (x < 0 || x > canvas.width || y < 0 || y > canvas.height) break;
                }
                
                ctx.stroke();
            });
        }
    }
    // Initial draw
    window.requestAnimationFrame(drawField);
    function getComponentColor(type, component) {
        const colors = {
            magnet: component.polarity > 0 ? '#ef4444' : '#3b82f6',
            coil: '#f59e0b',
            core: '#6b7280',
            battery: '#10b981',
            switch: '#8b5cf6'
        };
        return colors[type] || '#ffffff';
    }
    // Handle component creation from palette
    document.addEventListener('component-selected', (e) => {
        if (e.detail.type === 'wire') {
            isDrawingWire = true;
            overlay.style.cursor = 'crosshair';
            return;
        }
        
        const newComponent = {
            type: e.detail.type,
            x: 0.5, // Center of canvas
            y: 0.5,
            strength: 0.5,
            polarity: 1,
            turns: e.detail.type === 'coil' ? 5 : 0,
            isBeingDragged: true // Flag for new component being dragged
        };
        
        components[e.detail.type + 's'].push(newComponent);
        selectedComponent = newComponent;
        drawField();
        updateComponentDetails();
        
        // Set up initial drag for newly created component
        const handleMouseMove = (moveEvent) => {
            const rect = canvas.getBoundingClientRect();
            const x = moveEvent.clientX - rect.left;
            const y = moveEvent.clientY - rect.top;
            
            selectedComponent.x = x / canvas.width;
            selectedComponent.y = y / canvas.height;
            drawField();
            updateComponentDetails();
        };

        const handleMouseUp = () => {
            document.removeEventListener('mousemove', handleMouseMove);
            document.removeEventListener('mouseup', handleMouseUp);
            selectedComponent.isBeingDragged = false;
        };

        document.addEventListener('mousemove', handleMouseMove);
        document.addEventListener('mouseup', handleMouseUp);
    });
// Handle component deletion
    document.addEventListener('delete-selected', () => {
        if (selectedComponent) {
            const type = selectedComponent.type;
            const arr = components[type + 's'];
            const index = arr.indexOf(selectedComponent);
            if (index > -1) {
                arr.splice(index, 1);
                selectedComponent = null;
                drawField();
                updateComponentDetails();
            }
        }
    });
// Canvas interaction handlers
    canvas.addEventListener('mousedown', (e) => {
        const rect = canvas.getBoundingClientRect();
        const x = e.clientX - rect.left;
        const y = e.clientY - rect.top;
        
        if (isDrawingWire) {
            wireStartPoint = { x, y };
            currentWirePoints = [{ x, y }];
            return;
        }

        // Check if clicking on a component
        const allComponents = [
            ...components.magnets,
            ...components.coils,
            ...components.cores,
            ...components.batteries,
            ...components.switches
        ];
        
        selectedComponent = null;
        
        for (const comp of allComponents) {
            const compX = comp.x * canvas.width;
            const compY = comp.y * canvas.height;
            const radius = 20 + (comp.strength || 0.5) * 30;
            
            if (Math.sqrt((x - compX) ** 2 + (y - compY) ** 2) < radius) {
                selectedComponent = comp;
                break;
            }
        }
        
        if (selectedComponent) {
            // Prevent text selection during drag
            e.preventDefault();
            
            // Set up drag handlers
            const handleMouseMove = (moveEvent) => {
                const newX = moveEvent.clientX - rect.left;
                const newY = moveEvent.clientY - rect.top;
                
                selectedComponent.x = newX / canvas.width;
                selectedComponent.y = newY / canvas.height;
                drawField();
                updateComponentDetails();
            };

            const handleMouseUp = () => {
                document.removeEventListener('mousemove', handleMouseMove);
                document.removeEventListener('mouseup', handleMouseUp);
            };

            document.addEventListener('mousemove', handleMouseMove);
            document.addEventListener('mouseup', handleMouseUp);
        }
        
        drawField();
        updateComponentDetails();
    });
canvas.addEventListener('mousemove', (e) => {
        if (!isDrawingWire && !selectedComponent) return;
        
        const rect = canvas.getBoundingClientRect();
        const x = e.clientX - rect.left;
        const y = e.clientY - rect.top;
        
        if (isDrawingWire && wireStartPoint) {
            currentWirePoints.push({ x, y });
            drawField();
            return;
        }
        
        if (selectedComponent) {
            selectedComponent.x = x / canvas.width;
            selectedComponent.y = y / canvas.height;
            drawField();
            updateComponentDetails();
        }
    });
    canvas.addEventListener('mouseup', () => {
        if (isDrawingWire && wireStartPoint && currentWirePoints.length > 1) {
            components.wires.push({
                type: 'wire',
                points: [...currentWirePoints],
                current: 0.5
            });
            isDrawingWire = false;
            overlay.style.cursor = 'default';
            wireStartPoint = null;
            currentWirePoints = [];
            drawField();
        }
    });
function updateComponentDetails() {
        const detailsPanel = document.getElementById('component-details');
        if (!detailsPanel) return;
        
        if (!selectedComponent) {
            detailsPanel.innerHTML = '<p class="text-gray-400">No component selected</p>';
            return;
        }
        
        detailsPanel.innerHTML = `
            <h3 class="font-medium mb-2">${selectedComponent.type.toUpperCase()}</h3>
            <div class="grid grid-cols-2 gap-2">
                <div>X:</div>
                <div>${selectedComponent.x.toFixed(2)}</div>
                <div>Y:</div>
                <div>${selectedComponent.y.toFixed(2)}</div>
                ${selectedComponent.strength ? `
                    <div>Strength:</div>
                    <div>${selectedComponent.strength.toFixed(2)}</div>
                ` : ''}
                ${selectedComponent.polarity ? `
                    <div>Polarity:</div>
                    <div>${selectedComponent.polarity > 0 ? 'North' : 'South'}</div>
                ` : ''}
            </div>
        `;
    }
});