d3-charts-viz-library/dist/index.js

A comprehensive D3-based chart library with customizable charts and graphs

'use strict';

var d3 = require('d3');

function _interopNamespaceDefault(e) {
  var n = Object.create(null);
  if (e) {
    Object.keys(e).forEach(function (k) {
      if (k !== 'default') {
        var d = Object.getOwnPropertyDescriptor(e, k);
        Object.defineProperty(n, k, d.get ? d : {
          enumerable: true,
          get: function () { return e[k]; }
        });
      }
    });
  }
  n.default = e;
  return Object.freeze(n);
}

var d3__namespace = /*#__PURE__*/_interopNamespaceDefault(d3);

/**
 * Base Chart class that provides common functionality for all chart types
 */
class BaseChart {
  constructor(container, options = {}) {
    this.container = container;
    this.options = {
      width: 800,
      height: 400,
      margin: { top: 20, right: 30, bottom: 40, left: 40 },
      backgroundColor: '#ffffff',
      ...options
    };
    
    this.data = null;
    this.svg = null;
    this.chartGroup = null;
    
    this.init();
  }

  /**
   * Initialize the SVG container and chart group
   */
  init() {
    // Clear existing content
    d3__namespace.select(this.container).selectAll('*').remove();
    
    // Create SVG
    this.svg = d3__namespace.select(this.container)
      .append('svg')
      .attr('width', this.options.width)
      .attr('height', this.options.height)
      .style('background-color', this.options.backgroundColor);
    
    // Create chart group with margins
    this.chartGroup = this.svg.append('g')
      .attr('transform', `translate(${this.options.margin.left}, ${this.options.margin.top})`);
    
    // Calculate inner dimensions
    this.innerWidth = this.options.width - this.options.margin.left - this.options.margin.right;
    this.innerHeight = this.options.height - this.options.margin.top - this.options.margin.bottom;
  }

  /**
   * Set data for the chart
   */
  setData(data) {
    this.data = data;
    return this;
  }

  /**
   * Update chart options
   */
  updateOptions(newOptions) {
    this.options = { ...this.options, ...newOptions };
    this.init();
    return this;
  }

  /**
   * Get chart dimensions
   */
  getDimensions() {
    return {
      width: this.innerWidth,
      height: this.innerHeight,
      margin: this.options.margin
    };
  }

  /**
   * Add title to the chart
   */
  addTitle(title, options = {}) {
    const titleOptions = {
      fontSize: '16px',
      fontWeight: 'bold',
      textAnchor: 'middle',
      fill: '#333',
      ...options
    };

    this.svg.append('text')
      .attr('x', this.options.width / 2)
      .attr('y', titleOptions.fontSize === '16px' ? 16 : parseInt(titleOptions.fontSize))
      .style('font-size', titleOptions.fontSize)
      .style('font-weight', titleOptions.fontWeight)
      .style('text-anchor', titleOptions.textAnchor)
      .style('fill', titleOptions.fill)
      .text(title);

    return this;
  }

  /**
   * Add legend to the chart
   */
  addLegend(items, options = {}) {
    const legendOptions = {
      x: this.options.width - 100,
      y: 30,
      itemHeight: 20,
      fontSize: '12px',
      ...options
    };

    const legend = this.svg.append('g')
      .attr('class', 'legend')
      .attr('transform', `translate(${legendOptions.x}, ${legendOptions.y})`);

    const legendItems = legend.selectAll('.legend-item')
      .data(items)
      .enter()
      .append('g')
      .attr('class', 'legend-item')
      .attr('transform', (d, i) => `translate(0, ${i * legendOptions.itemHeight})`);

    legendItems.append('rect')
      .attr('width', 12)
      .attr('height', 12)
      .attr('fill', d => d.color);

    legendItems.append('text')
      .attr('x', 16)
      .attr('y', 9)
      .style('font-size', legendOptions.fontSize)
      .style('alignment-baseline', 'middle')
      .text(d => d.label);

    return this;
  }

  /**
   * Add tooltip functionality
   */
  addTooltip() {
    this.tooltip = d3__namespace.select('body')
      .append('div')
      .attr('class', 'd3-tooltip')
      .style('position', 'absolute')
      .style('visibility', 'hidden')
      .style('background-color', 'rgba(0, 0, 0, 0.8)')
      .style('color', 'white')
      .style('padding', '8px')
      .style('border-radius', '4px')
      .style('font-size', '12px')
      .style('pointer-events', 'none')
      .style('z-index', '1000');

    return this;
  }

  /**
   * Show tooltip
   */
  showTooltip(content, event) {
    if (this.tooltip) {
      this.tooltip
        .style('visibility', 'visible')
        .html(content)
        .style('left', (event.pageX + 10) + 'px')
        .style('top', (event.pageY - 10) + 'px');
    }
  }

  /**
   * Hide tooltip
   */
  hideTooltip() {
    if (this.tooltip) {
      this.tooltip.style('visibility', 'hidden');
    }
  }

  /**
   * Render method to be implemented by subclasses
   */
  render() {
    throw new Error('render() method must be implemented by subclasses');
  }

  /**
   * Destroy the chart and clean up
   */
  destroy() {
    if (this.tooltip) {
      this.tooltip.remove();
    }
    d3__namespace.select(this.container).selectAll('*').remove();
  }
}

/**
 * Bar Chart implementation
 */
class BarChart extends BaseChart {
  constructor(container, options = {}) {
    const defaultOptions = {
      barPadding: 0.1,
      barColor: '#3498db',
      hoverColor: '#2980b9',
      showValues: false,
      orientation: 'vertical', // 'vertical' or 'horizontal'
      ...options
    };
    
    super(container, defaultOptions);
    this.addTooltip();
  }

  /**
   * Render the bar chart
   */
  render() {
    if (!this.data || this.data.length === 0) {
      console.warn('No data provided for BarChart');
      return this;
    }

    // Clear previous chart
    this.chartGroup.selectAll('*').remove();

    if (this.options.orientation === 'vertical') {
      this.renderVerticalBars();
    } else {
      this.renderHorizontalBars();
    }

    return this;
  }

  /**
   * Render vertical bars
   */
  renderVerticalBars() {
    // Create scales
    const xScale = d3__namespace.scaleBand()
      .domain(this.data.map(d => d.label))
      .range([0, this.innerWidth])
      .padding(this.options.barPadding);

    const yScale = d3__namespace.scaleLinear()
      .domain([0, d3__namespace.max(this.data, d => d.value)])
      .range([this.innerHeight, 0]);

    // Create axes
    const xAxis = d3__namespace.axisBottom(xScale);
    const yAxis = d3__namespace.axisLeft(yScale);

    // Add X axis
    this.chartGroup.append('g')
      .attr('class', 'x-axis')
      .attr('transform', `translate(0, ${this.innerHeight})`)
      .call(xAxis);

    // Add Y axis
    this.chartGroup.append('g')
      .attr('class', 'y-axis')
      .call(yAxis);

    // Create bars
    const bars = this.chartGroup.selectAll('.bar')
      .data(this.data)
      .enter()
      .append('rect')
      .attr('class', 'bar')
      .attr('x', d => xScale(d.label))
      .attr('width', xScale.bandwidth())
      .attr('y', this.innerHeight)
      .attr('height', 0)
      .attr('fill', this.options.barColor)
      .style('cursor', 'pointer');

    // Animate bars
    bars.transition()
      .duration(800)
      .attr('y', d => yScale(d.value))
      .attr('height', d => this.innerHeight - yScale(d.value));

    // Add interactivity
    this.addBarInteractivity(bars);

    // Add value labels if requested
    if (this.options.showValues) {
      this.addValueLabels(xScale, yScale);
    }
  }

  /**
   * Render horizontal bars
   */
  renderHorizontalBars() {
    // Create scales
    const yScale = d3__namespace.scaleBand()
      .domain(this.data.map(d => d.label))
      .range([0, this.innerHeight])
      .padding(this.options.barPadding);

    const xScale = d3__namespace.scaleLinear()
      .domain([0, d3__namespace.max(this.data, d => d.value)])
      .range([0, this.innerWidth]);

    // Create axes
    const xAxis = d3__namespace.axisBottom(xScale);
    const yAxis = d3__namespace.axisLeft(yScale);

    // Add X axis
    this.chartGroup.append('g')
      .attr('class', 'x-axis')
      .attr('transform', `translate(0, ${this.innerHeight})`)
      .call(xAxis);

    // Add Y axis
    this.chartGroup.append('g')
      .attr('class', 'y-axis')
      .call(yAxis);

    // Create bars
    const bars = this.chartGroup.selectAll('.bar')
      .data(this.data)
      .enter()
      .append('rect')
      .attr('class', 'bar')
      .attr('y', d => yScale(d.label))
      .attr('height', yScale.bandwidth())
      .attr('x', 0)
      .attr('width', 0)
      .attr('fill', this.options.barColor)
      .style('cursor', 'pointer');

    // Animate bars
    bars.transition()
      .duration(800)
      .attr('width', d => xScale(d.value));

    // Add interactivity
    this.addBarInteractivity(bars);
  }

  /**
   * Add interactivity to bars
   */
  addBarInteractivity(bars) {
    const self = this;

    bars
      .on('mouseover', function(event, d) {
        d3__namespace.select(this).attr('fill', self.options.hoverColor);
        self.showTooltip(`${d.label}: ${d.value}`, event);
      })
      .on('mouseout', function() {
        d3__namespace.select(this).attr('fill', self.options.barColor);
        self.hideTooltip();
      })
      .on('click', function(event, d) {
        if (self.options.onClick) {
          self.options.onClick(d, event);
        }
      });
  }

  /**
   * Add value labels on bars
   */
  addValueLabels(xScale, yScale) {
    if (this.options.orientation === 'vertical') {
      this.chartGroup.selectAll('.value-label')
        .data(this.data)
        .enter()
        .append('text')
        .attr('class', 'value-label')
        .attr('x', d => xScale(d.label) + xScale.bandwidth() / 2)
        .attr('y', d => yScale(d.value) - 5)
        .attr('text-anchor', 'middle')
        .style('font-size', '12px')
        .style('fill', '#333')
        .text(d => d.value);
    } else {
      this.chartGroup.selectAll('.value-label')
        .data(this.data)
        .enter()
        .append('text')
        .attr('class', 'value-label')
        .attr('x', d => xScale(d.value) + 5)
        .attr('y', d => yScale(d.label) + yScale.bandwidth() / 2)
        .attr('text-anchor', 'start')
        .attr('alignment-baseline', 'middle')
        .style('font-size', '12px')
        .style('fill', '#333')
        .text(d => d.value);
    }
  }

  /**
   * Update chart with new data
   */
  updateData(newData) {
    this.setData(newData);
    this.render();
    return this;
  }
}

/**
 * Line Chart implementation
 */
class LineChart extends BaseChart {
  constructor(container, options = {}) {
    const defaultOptions = {
      lineColor: '#3498db',
      lineWidth: 2,
      pointRadius: 4,
      pointColor: '#3498db',
      pointHoverRadius: 6,
      showPoints: true,
      showArea: false,
      areaColor: 'rgba(52, 152, 219, 0.3)',
      curve: d3__namespace.curveLinear,
      ...options
    };
    
    super(container, defaultOptions);
    this.addTooltip();
  }

  /**
   * Render the line chart
   */
  render() {
    if (!this.data || this.data.length === 0) {
      console.warn('No data provided for LineChart');
      return this;
    }

    // Clear previous chart
    this.chartGroup.selectAll('*').remove();

    // Create scales
    const xScale = d3__namespace.scaleLinear()
      .domain(d3__namespace.extent(this.data, d => d.x))
      .range([0, this.innerWidth]);

    const yScale = d3__namespace.scaleLinear()
      .domain(d3__namespace.extent(this.data, d => d.y))
      .range([this.innerHeight, 0]);

    // Create line generator
    const line = d3__namespace.line()
      .x(d => xScale(d.x))
      .y(d => yScale(d.y))
      .curve(this.options.curve);

    // Create area generator (if needed)
    let area;
    if (this.options.showArea) {
      area = d3__namespace.area()
        .x(d => xScale(d.x))
        .y0(this.innerHeight)
        .y1(d => yScale(d.y))
        .curve(this.options.curve);
    }

    // Create axes
    const xAxis = d3__namespace.axisBottom(xScale);
    const yAxis = d3__namespace.axisLeft(yScale);

    // Add X axis
    this.chartGroup.append('g')
      .attr('class', 'x-axis')
      .attr('transform', `translate(0, ${this.innerHeight})`)
      .call(xAxis);

    // Add Y axis
    this.chartGroup.append('g')
      .attr('class', 'y-axis')
      .call(yAxis);

    // Add area if requested
    if (this.options.showArea && area) {
      this.chartGroup.append('path')
        .datum(this.data)
        .attr('class', 'area')
        .attr('fill', this.options.areaColor)
        .attr('d', area);
    }

    // Add line
    const path = this.chartGroup.append('path')
      .datum(this.data)
      .attr('class', 'line')
      .attr('fill', 'none')
      .attr('stroke', this.options.lineColor)
      .attr('stroke-width', this.options.lineWidth)
      .attr('d', line);

    // Animate line drawing
    const totalLength = path.node().getTotalLength();
    path
      .attr('stroke-dasharray', totalLength + ' ' + totalLength)
      .attr('stroke-dashoffset', totalLength)
      .transition()
      .duration(1000)
      .attr('stroke-dashoffset', 0);

    // Add points if requested
    if (this.options.showPoints) {
      this.addPoints(xScale, yScale);
    }

    return this;
  }

  /**
   * Add interactive points to the line
   */
  addPoints(xScale, yScale) {
    const self = this;

    const points = this.chartGroup.selectAll('.point')
      .data(this.data)
      .enter()
      .append('circle')
      .attr('class', 'point')
      .attr('cx', d => xScale(d.x))
      .attr('cy', d => yScale(d.y))
      .attr('r', 0)
      .attr('fill', this.options.pointColor)
      .style('cursor', 'pointer');

    // Animate points
    points.transition()
      .delay((d, i) => i * 50)
      .duration(300)
      .attr('r', this.options.pointRadius);

    // Add interactivity
    points
      .on('mouseover', function(event, d) {
        d3__namespace.select(this)
          .transition()
          .duration(150)
          .attr('r', self.options.pointHoverRadius);
        
        self.showTooltip(`(${d.x}, ${d.y})`, event);
      })
      .on('mouseout', function() {
        d3__namespace.select(this)
          .transition()
          .duration(150)
          .attr('r', self.options.pointRadius);
        
        self.hideTooltip();
      })
      .on('click', function(event, d) {
        if (self.options.onClick) {
          self.options.onClick(d, event);
        }
      });
  }

  /**
   * Add multiple lines for multi-series data
   */
  renderMultiSeries(seriesData) {
    if (!seriesData || seriesData.length === 0) {
      console.warn('No series data provided for LineChart');
      return this;
    }

    // Clear previous chart
    this.chartGroup.selectAll('*').remove();

    // Get all data points for scaling
    const allData = seriesData.flatMap(series => series.data);

    // Create scales
    const xScale = d3__namespace.scaleLinear()
      .domain(d3__namespace.extent(allData, d => d.x))
      .range([0, this.innerWidth]);

    const yScale = d3__namespace.scaleLinear()
      .domain(d3__namespace.extent(allData, d => d.y))
      .range([this.innerHeight, 0]);

    // Color scale for different series
    const colorScale = d3__namespace.scaleOrdinal(d3__namespace.schemeCategory10);

    // Create line generator
    const line = d3__namespace.line()
      .x(d => xScale(d.x))
      .y(d => yScale(d.y))
      .curve(this.options.curve);

    // Create axes
    const xAxis = d3__namespace.axisBottom(xScale);
    const yAxis = d3__namespace.axisLeft(yScale);

    // Add axes
    this.chartGroup.append('g')
      .attr('class', 'x-axis')
      .attr('transform', `translate(0, ${this.innerHeight})`)
      .call(xAxis);

    this.chartGroup.append('g')
      .attr('class', 'y-axis')
      .call(yAxis);

    // Add lines for each series
    seriesData.forEach((series, index) => {
      const color = series.color || colorScale(index);

      // Add line
      const path = this.chartGroup.append('path')
        .datum(series.data)
        .attr('class', `line series-${index}`)
        .attr('fill', 'none')
        .attr('stroke', color)
        .attr('stroke-width', this.options.lineWidth)
        .attr('d', line);

      // Animate line drawing
      const totalLength = path.node().getTotalLength();
      path
        .attr('stroke-dasharray', totalLength + ' ' + totalLength)
        .attr('stroke-dashoffset', totalLength)
        .transition()
        .delay(index * 200)
        .duration(1000)
        .attr('stroke-dashoffset', 0);

      // Add points if requested
      if (this.options.showPoints) {
        this.addSeriesPoints(series.data, xScale, yScale, color, series.name);
      }
    });

    // Add legend
    const legendItems = seriesData.map((series, index) => ({
      label: series.name || `Series ${index + 1}`,
      color: series.color || colorScale(index)
    }));
    this.addLegend(legendItems);

    return this;
  }

  /**
   * Add points for a specific series
   */
  addSeriesPoints(data, xScale, yScale, color, seriesName) {
    const self = this;

    const points = this.chartGroup.selectAll(`.point-${seriesName}`)
      .data(data)
      .enter()
      .append('circle')
      .attr('class', `point point-${seriesName}`)
      .attr('cx', d => xScale(d.x))
      .attr('cy', d => yScale(d.y))
      .attr('r', 0)
      .attr('fill', color)
      .style('cursor', 'pointer');

    // Animate points
    points.transition()
      .delay((d, i) => i * 30)
      .duration(300)
      .attr('r', this.options.pointRadius);

    // Add interactivity
    points
      .on('mouseover', function(event, d) {
        d3__namespace.select(this)
          .transition()
          .duration(150)
          .attr('r', self.options.pointHoverRadius);
        
        self.showTooltip(`${seriesName}: (${d.x}, ${d.y})`, event);
      })
      .on('mouseout', function() {
        d3__namespace.select(this)
          .transition()
          .duration(150)
          .attr('r', self.options.pointRadius);
        
        self.hideTooltip();
      });
  }

  /**
   * Update chart with new data
   */
  updateData(newData) {
    this.setData(newData);
    this.render();
    return this;
  }
}

/**
 * Pie Chart implementation
 */
class PieChart extends BaseChart {
  constructor(container, options = {}) {
    const defaultOptions = {
      innerRadius: 0,
      outerRadius: null, // Will be calculated based on chart size
      padAngle: 0.02,
      cornerRadius: 0,
      colors: d3__namespace.schemeCategory10,
      showLabels: true,
      labelOffset: 20,
      showPercentages: true,
      ...options
    };
    
    super(container, defaultOptions);
    this.addTooltip();
  }

  /**
   * Render the pie chart
   */
  render() {
    if (!this.data || this.data.length === 0) {
      console.warn('No data provided for PieChart');
      return this;
    }

    // Clear previous chart
    this.chartGroup.selectAll('*').remove();

    // Calculate radius if not provided
    const radius = this.options.outerRadius || 
      Math.min(this.innerWidth, this.innerHeight) / 2 - 10;

    // Center the chart
    const centerX = this.innerWidth / 2;
    const centerY = this.innerHeight / 2;

    const chartCenter = this.chartGroup.append('g')
      .attr('transform', `translate(${centerX}, ${centerY})`);

    // Create pie layout
    const pie = d3__namespace.pie()
      .value(d => d.value)
      .sort(null)
      .padAngle(this.options.padAngle);

    // Create arc generator
    const arc = d3__namespace.arc()
      .innerRadius(this.options.innerRadius)
      .outerRadius(radius)
      .cornerRadius(this.options.cornerRadius);

    // Create arc generator for labels
    const labelArc = d3__namespace.arc()
      .innerRadius(radius + this.options.labelOffset)
      .outerRadius(radius + this.options.labelOffset);

    // Color scale
    const colorScale = d3__namespace.scaleOrdinal(this.options.colors);

    // Create pie slices
    const slices = chartCenter.selectAll('.slice')
      .data(pie(this.data))
      .enter()
      .append('g')
      .attr('class', 'slice');

    // Add paths
    const paths = slices.append('path')
      .attr('fill', (d, i) => colorScale(i))
      .attr('stroke', '#fff')
      .attr('stroke-width', 2)
      .style('cursor', 'pointer')
      .each(function(d) { this._current = { startAngle: 0, endAngle: 0 }; });

    // Animate slices
    paths.transition()
      .duration(1000)
      .attrTween('d', function(d) {
        const interpolate = d3__namespace.interpolate(this._current, d);
        this._current = interpolate(0);
        return function(t) {
          return arc(interpolate(t));
        };
      });

    // Add interactivity
    this.addSliceInteractivity(paths, arc);

    // Add labels if requested
    if (this.options.showLabels) {
      this.addLabels(slices, pie(this.data), labelArc);
    }

    return this;
  }

  /**
   * Add interactivity to pie slices
   */
  addSliceInteractivity(paths, arc) {
    const self = this;
    const hoverArc = d3__namespace.arc()
      .innerRadius(this.options.innerRadius)
      .outerRadius(arc.outerRadius()() + 10)
      .cornerRadius(this.options.cornerRadius);

    paths
      .on('mouseover', function(event, d) {
        // Expand slice
        d3__namespace.select(this)
          .transition()
          .duration(200)
          .attr('d', hoverArc);

        // Show tooltip
        const percentage = ((d.endAngle - d.startAngle) / (2 * Math.PI) * 100).toFixed(1);
        const tooltipContent = `${d.data.label}: ${d.data.value} (${percentage}%)`;
        self.showTooltip(tooltipContent, event);
      })
      .on('mouseout', function(event, d) {
        // Return to normal size
        d3__namespace.select(this)
          .transition()
          .duration(200)
          .attr('d', arc);

        self.hideTooltip();
      })
      .on('click', function(event, d) {
        if (self.options.onClick) {
          self.options.onClick(d.data, event);
        }
      });
  }

  /**
   * Add labels to pie slices
   */
  addLabels(slices, pieData, labelArc) {
    const labels = slices.append('text')
      .attr('transform', d => `translate(${labelArc.centroid(d)})`)
      .attr('text-anchor', 'middle')
      .attr('alignment-baseline', 'middle')
      .style('font-size', '12px')
      .style('fill', '#333')
      .style('opacity', 0);

    // Add label text
    labels.text(d => {
      if (this.options.showPercentages) {
        const percentage = ((d.endAngle - d.startAngle) / (2 * Math.PI) * 100).toFixed(1);
        return `${d.data.label} (${percentage}%)`;
      }
      return d.data.label;
    });

    // Animate labels
    labels.transition()
      .delay(500)
      .duration(500)
      .style('opacity', 1);

    // Add lines connecting labels to slices
    this.addLabelLines(slices, pieData, labelArc);
  }

  /**
   * Add lines connecting labels to slices
   */
  addLabelLines(slices, pieData, labelArc) {
    const arc = d3__namespace.arc()
      .innerRadius(this.options.innerRadius)
      .outerRadius(this.options.outerRadius || 
        Math.min(this.innerWidth, this.innerHeight) / 2 - 10);

    const lines = slices.append('polyline')
      .attr('fill', 'none')
      .attr('stroke', '#999')
      .attr('stroke-width', 1)
      .style('opacity', 0);

    lines.attr('points', d => {
      const pos = labelArc.centroid(d);
      const midPos = arc.centroid(d);
      return [midPos, pos];
    });

    // Animate lines
    lines.transition()
      .delay(500)
      .duration(500)
      .style('opacity', 0.7);
  }

  /**
   * Create a donut chart (pie chart with inner radius)
   */
  createDonut(innerRadiusRatio = 0.5) {
    const radius = this.options.outerRadius || 
      Math.min(this.innerWidth, this.innerHeight) / 2 - 10;
    
    this.options.innerRadius = radius * innerRadiusRatio;
    return this.render();
  }

  /**
   * Update chart with new data
   */
  updateData(newData) {
    this.setData(newData);
    this.render();
    return this;
  }

  /**
   * Animate slice explosion
   */
  explodeSlice(index, distance = 20) {
    const slice = this.chartGroup.select(`.slice:nth-child(${index + 1})`);
    const pieData = d3__namespace.pie().value(d => d.value)(this.data);
    const centroid = d3__namespace.arc()
      .innerRadius(this.options.innerRadius)
      .outerRadius(this.options.outerRadius || 
        Math.min(this.innerWidth, this.innerHeight) / 2 - 10)
      .centroid(pieData[index]);

    const x = centroid[0] * distance / 100;
    const y = centroid[1] * distance / 100;

    slice.transition()
      .duration(300)
      .attr('transform', `translate(${x}, ${y})`);

    return this;
  }

  /**
   * Reset all slice positions
   */
  resetSlices() {
    this.chartGroup.selectAll('.slice')
      .transition()
      .duration(300)
      .attr('transform', 'translate(0, 0)');

    return this;
  }
}

/**
 * Scatter Plot implementation
 */
class ScatterPlot extends BaseChart {
  constructor(container, options = {}) {
    const defaultOptions = {
      pointRadius: 4,
      pointColor: '#3498db',
      pointOpacity: 0.7,
      hoverRadius: 6,
      hoverOpacity: 1,
      showTrendLine: false,
      trendLineColor: '#e74c3c',
      trendLineWidth: 2,
      ...options
    };
    
    super(container, defaultOptions);
    this.addTooltip();
  }

  /**
   * Render the scatter plot
   */
  render() {
    if (!this.data || this.data.length === 0) {
      console.warn('No data provided for ScatterPlot');
      return this;
    }

    // Clear previous chart
    this.chartGroup.selectAll('*').remove();

    // Create scales
    const xScale = d3__namespace.scaleLinear()
      .domain(d3__namespace.extent(this.data, d => d.x))
      .range([0, this.innerWidth])
      .nice();

    const yScale = d3__namespace.scaleLinear()
      .domain(d3__namespace.extent(this.data, d => d.y))
      .range([this.innerHeight, 0])
      .nice();

    // Create axes
    const xAxis = d3__namespace.axisBottom(xScale);
    const yAxis = d3__namespace.axisLeft(yScale);

    // Add X axis
    this.chartGroup.append('g')
      .attr('class', 'x-axis')
      .attr('transform', `translate(0, ${this.innerHeight})`)
      .call(xAxis);

    // Add Y axis
    this.chartGroup.append('g')
      .attr('class', 'y-axis')
      .call(yAxis);

    // Add axis labels
    this.addAxisLabels();

    // Add trend line if requested
    if (this.options.showTrendLine) {
      this.addTrendLine(xScale, yScale);
    }

    // Create points
    this.addPoints(xScale, yScale);

    return this;
  }

  /**
   * Add scatter plot points
   */
  addPoints(xScale, yScale) {
    const self = this;

    const points = this.chartGroup.selectAll('.point')
      .data(this.data)
      .enter()
      .append('circle')
      .attr('class', 'point')
      .attr('cx', d => xScale(d.x))
      .attr('cy', d => yScale(d.y))
      .attr('r', 0)
      .attr('fill', d => d.color || this.options.pointColor)
      .attr('opacity', this.options.pointOpacity)
      .style('cursor', 'pointer');

    // Animate points
    points.transition()
      .delay((d, i) => i * 20)
      .duration(500)
      .attr('r', d => d.radius || this.options.pointRadius);

    // Add interactivity
    points
      .on('mouseover', function(event, d) {
        d3__namespace.select(this)
          .transition()
          .duration(150)
          .attr('r', self.options.hoverRadius)
          .attr('opacity', self.options.hoverOpacity);

        const tooltipContent = self.formatTooltip(d);
        self.showTooltip(tooltipContent, event);
      })
      .on('mouseout', function(event, d) {
        d3__namespace.select(this)
          .transition()
          .duration(150)
          .attr('r', d.radius || self.options.pointRadius)
          .attr('opacity', self.options.pointOpacity);

        self.hideTooltip();
      })
      .on('click', function(event, d) {
        if (self.options.onClick) {
          self.options.onClick(d, event);
        }
      });
  }

  /**
   * Format tooltip content
   */
  formatTooltip(d) {
    let content = `X: ${d.x}<br>Y: ${d.y}`;
    
    if (d.label) {
      content = `${d.label}<br>${content}`;
    }
    
    if (d.category) {
      content += `<br>Category: ${d.category}`;
    }
    
    return content;
  }

  /**
   * Add trend line using linear regression
   */
  addTrendLine(xScale, yScale) {
    const regression = this.calculateLinearRegression();
    
    if (!regression) return;

    const xDomain = xScale.domain();
    const trendData = [
      { x: xDomain[0], y: regression.slope * xDomain[0] + regression.intercept },
      { x: xDomain[1], y: regression.slope * xDomain[1] + regression.intercept }
    ];

    const line = d3__namespace.line()
      .x(d => xScale(d.x))
      .y(d => yScale(d.y));

    this.chartGroup.append('path')
      .datum(trendData)
      .attr('class', 'trend-line')
      .attr('fill', 'none')
      .attr('stroke', this.options.trendLineColor)
      .attr('stroke-width', this.options.trendLineWidth)
      .attr('stroke-dasharray', '5,5')
      .attr('d', line);

    // Add R² value
    this.chartGroup.append('text')
      .attr('x', this.innerWidth - 10)
      .attr('y', 20)
      .attr('text-anchor', 'end')
      .style('font-size', '12px')
      .style('fill', this.options.trendLineColor)
      .text(`R² = ${regression.rSquared.toFixed(3)}`);
  }

  /**
   * Calculate linear regression
   */
  calculateLinearRegression() {
    if (this.data.length < 2) return null;

    const n = this.data.length;
    const sumX = d3__namespace.sum(this.data, d => d.x);
    const sumY = d3__namespace.sum(this.data, d => d.y);
    const sumXY = d3__namespace.sum(this.data, d => d.x * d.y);
    const sumXX = d3__namespace.sum(this.data, d => d.x * d.x);
    d3__namespace.sum(this.data, d => d.y * d.y);

    const slope = (n * sumXY - sumX * sumY) / (n * sumXX - sumX * sumX);
    const intercept = (sumY - slope * sumX) / n;

    // Calculate R²
    const yMean = sumY / n;
    const ssRes = d3__namespace.sum(this.data, d => Math.pow(d.y - (slope * d.x + intercept), 2));
    const ssTot = d3__namespace.sum(this.data, d => Math.pow(d.y - yMean, 2));
    const rSquared = 1 - (ssRes / ssTot);

    return { slope, intercept, rSquared };
  }

  /**
   * Add axis labels
   */
  addAxisLabels() {
    // X axis label
    if (this.options.xLabel) {
      this.chartGroup.append('text')
        .attr('x', this.innerWidth / 2)
        .attr('y', this.innerHeight + 35)
        .attr('text-anchor', 'middle')
        .style('font-size', '14px')
        .style('fill', '#333')
        .text(this.options.xLabel);
    }

    // Y axis label
    if (this.options.yLabel) {
      this.chartGroup.append('text')
        .attr('transform', 'rotate(-90)')
        .attr('x', -this.innerHeight / 2)
        .attr('y', -35)
        .attr('text-anchor', 'middle')
        .style('font-size', '14px')
        .style('fill', '#333')
        .text(this.options.yLabel);
    }
  }

  /**
   * Render scatter plot with categories (different colors)
   */
  renderWithCategories(data, categoryField = 'category') {
    this.setData(data);

    // Get unique categories
    const categories = [...new Set(data.map(d => d[categoryField]))];
    const colorScale = d3__namespace.scaleOrdinal(d3__namespace.schemeCategory10)
      .domain(categories);

    // Assign colors based on category
    this.data.forEach(d => {
      d.color = colorScale(d[categoryField]);
    });

    this.render();

    // Add legend
    const legendItems = categories.map(category => ({
      label: category,
      color: colorScale(category)
    }));
    this.addLegend(legendItems);

    return this;
  }

  /**
   * Render bubble chart (scatter plot with varying point sizes)
   */
  renderBubbleChart(sizeField = 'size') {
    if (!this.data || this.data.length === 0) {
      console.warn('No data provided for BubbleChart');
      return this;
    }

    // Create size scale
    const sizeExtent = d3__namespace.extent(this.data, d => d[sizeField]);
    const sizeScale = d3__namespace.scaleSqrt()
      .domain(sizeExtent)
      .range([3, 20]);

    // Assign radius based on size field
    this.data.forEach(d => {
      d.radius = sizeScale(d[sizeField]);
    });

    this.render();

    return this;
  }

  /**
   * Update chart with new data
   */
  updateData(newData) {
    this.setData(newData);
    this.render();
    return this;
  }

  /**
   * Highlight points based on condition
   */
  highlightPoints(condition, highlightColor = '#e74c3c') {
    this.chartGroup.selectAll('.point')
      .attr('fill', d => condition(d) ? highlightColor : (d.color || this.options.pointColor));

    return this;
  }

  /**
   * Reset point colors
   */
  resetHighlight() {
    this.chartGroup.selectAll('.point')
      .attr('fill', d => d.color || this.options.pointColor);

    return this;
  }
}

/**
 * Area Chart implementation
 */
class AreaChart extends BaseChart {
  constructor(container, options = {}) {
    const defaultOptions = {
      areaColor: 'rgba(52, 152, 219, 0.6)',
      lineColor: '#3498db',
      lineWidth: 2,
      curve: d3__namespace.curveLinear,
      showLine: true,
      showPoints: false,
      pointRadius: 3,
      ...options
    };
    
    super(container, defaultOptions);
    this.addTooltip();
  }

  /**
   * Render the area chart
   */
  render() {
    if (!this.data || this.data.length === 0) {
      console.warn('No data provided for AreaChart');
      return this;
    }

    // Clear previous chart
    this.chartGroup.selectAll('*').remove();

    // Create scales
    const xScale = d3__namespace.scaleLinear()
      .domain(d3__namespace.extent(this.data, d => d.x))
      .range([0, this.innerWidth]);

    const yScale = d3__namespace.scaleLinear()
      .domain([0, d3__namespace.max(this.data, d => d.y)])
      .range([this.innerHeight, 0]);

    // Create area generator
    const area = d3__namespace.area()
      .x(d => xScale(d.x))
      .y0(this.innerHeight)
      .y1(d => yScale(d.y))
      .curve(this.options.curve);

    // Create line generator
    const line = d3__namespace.line()
      .x(d => xScale(d.x))
      .y(d => yScale(d.y))
      .curve(this.options.curve);

    // Create axes
    const xAxis = d3__namespace.axisBottom(xScale);
    const yAxis = d3__namespace.axisLeft(yScale);

    // Add X axis
    this.chartGroup.append('g')
      .attr('class', 'x-axis')
      .attr('transform', `translate(0, ${this.innerHeight})`)
      .call(xAxis);

    // Add Y axis
    this.chartGroup.append('g')
      .attr('class', 'y-axis')
      .call(yAxis);

    // Add area
    const areaPath = this.chartGroup.append('path')
      .datum(this.data)
      .attr('class', 'area')
      .attr('fill', this.options.areaColor)
      .attr('d', area);

    // Animate area
    this.animateArea(areaPath);

    // Add line if requested
    if (this.options.showLine) {
      const linePath = this.chartGroup.append('path')
        .datum(this.data)
        .attr('class', 'line')
        .attr('fill', 'none')
        .attr('stroke', this.options.lineColor)
        .attr('stroke-width', this.options.lineWidth)
        .attr('d', line);

      // Animate line
      this.animateLine(linePath);
    }

    // Add points if requested
    if (this.options.showPoints) {
      this.addPoints(xScale, yScale);
    }

    // Add interaction overlay
    this.addInteractionOverlay(xScale, yScale);

    return this;
  }

  /**
   * Animate area drawing
   */
  animateArea(areaPath) {
    const totalLength = areaPath.node().getTotalLength();
    
    areaPath
      .attr('stroke-dasharray', totalLength + ' ' + totalLength)
      .attr('stroke-dashoffset', totalLength)
      .attr('stroke', this.options.areaColor)
      .attr('stroke-width', 1)
      .transition()
      .duration(1500)
      .attr('stroke-dashoffset', 0)
      .on('end', function() {
        d3__namespace.select(this).attr('stroke', 'none');
      });
  }

  /**
   * Animate line drawing
   */
  animateLine(linePath) {
    const totalLength = linePath.node().getTotalLength();
    
    linePath
      .attr('stroke-dasharray', totalLength + ' ' + totalLength)
      .attr('stroke-dashoffset', totalLength)
      .transition()
      .duration(1500)
      .attr('stroke-dashoffset', 0);
  }

  /**
   * Add interactive points
   */
  addPoints(xScale, yScale) {
    const self = this;

    const points = this.chartGroup.selectAll('.point')
      .data(this.data)
      .enter()
      .append('circle')
      .attr('class', 'point')
      .attr('cx', d => xScale(d.x))
      .attr('cy', d => yScale(d.y))
      .attr('r', 0)
      .attr('fill', this.options.lineColor)
      .style('cursor', 'pointer');

    // Animate points
    points.transition()
      .delay((d, i) => i * 50)
      .duration(300)
      .attr('r', this.options.pointRadius);

    // Add interactivity
    points
      .on('mouseover', function(event, d) {
        d3__namespace.select(this)
          .transition()
          .duration(150)
          .attr('r', self.options.pointRadius * 1.5);
        
        self.showTooltip(`(${d.x}, ${d.y})`, event);
      })
      .on('mouseout', function() {
        d3__namespace.select(this)
          .transition()
          .duration(150)
          .attr('r', self.options.pointRadius);
        
        self.hideTooltip();
      });
  }

  /**
   * Add interaction overlay for hover effects
   */
  addInteractionOverlay(xScale, yScale) {
    const self = this;

    // Create bisector for finding closest data point
    const bisect = d3__namespace.bisector(d => d.x).left;

    // Add invisible overlay for mouse tracking
    const overlay = this.chartGroup.append('rect')
      .attr('class', 'overlay')
      .attr('width', this.innerWidth)
      .attr('height', this.innerHeight)
      .attr('fill', 'none')
      .attr('pointer-events', 'all')
      .style('cursor', 'crosshair');

    // Add focus elements
    const focus = this.chartGroup.append('g')
      .attr('class', 'focus')
      .style('display', 'none');

    focus.append('circle')
      .attr('r', 4)
      .attr('fill', this.options.lineColor)
      .attr('stroke', '#fff')
      .attr('stroke-width', 2);

    focus.append('line')
      .attr('class', 'x-hover-line')
      .attr('stroke', '#999')
      .attr('stroke-width', 1)
      .attr('stroke-dasharray', '3,3');

    focus.append('line')
      .attr('class', 'y-hover-line')
      .attr('stroke', '#999')
      .attr('stroke-width', 1)
      .attr('stroke-dasharray', '3,3');

    // Mouse events
    overlay
      .on('mouseover', () => focus.style('display', null))
      .on('mouseout', () => {
        focus.style('display', 'none');
        self.hideTooltip();
      })
      .on('mousemove', function(event) {
        const [mouseX] = d3__namespace.pointer(event, this);
        const x0 = xScale.invert(mouseX);
        const i = bisect(self.data, x0, 1);
        
        if (i >= self.data.length) return;
        
        const d0 = self.data[i - 1];
        const d1 = self.data[i];
        const d = x0 - d0.x > d1.x - x0 ? d1 : d0;

        focus.attr('transform', `translate(${xScale(d.x)}, ${yScale(d.y)})`);

        focus.select('.x-hover-line')
          .attr('y1', -yScale(d.y))
          .attr('y2', self.innerHeight - yScale(d.y));

        focus.select('.y-hover-line')
          .attr('x1', -xScale(d.x))
          .attr('x2', self.innerWidth - xScale(d.x));

        self.showTooltip(`(${d.x}, ${d.y})`, event);
      });
  }

  /**
   * Render stacked area chart
   */
  renderStacked(seriesData) {
    if (!seriesData || seriesData.length === 0) {
      console.warn('No series data provided for stacked AreaChart');
      return this;
    }

    // Clear previous chart
    this.chartGroup.selectAll('*').remove();

    // Prepare data for stacking
    const keys = seriesData.map(d => d.name);
    const stackData = this.prepareStackData(seriesData);

    // Create stack generator
    const stack = d3__namespace.stack()
      .keys(keys)
      .order(d3__namespace.stackOrderNone)
      .offset(d3__namespace.stackOffsetNone);

    const stackedData = stack(stackData);

    // Create scales
    const xScale = d3__namespace.scaleLinear()
      .domain(d3__namespace.extent(stackData, d => d.x))
      .range([0, this.innerWidth]);

    const yScale = d3__namespace.scaleLinear()
      .domain([0, d3__namespace.max(stackedData, d => d3__namespace.max(d, d => d[1]))])
      .range([this.innerHeight, 0]);

    // Color scale
    const colorScale = d3__namespace.scaleOrdinal(d3__namespace.schemeCategory10);

    // Create area generator
    const area = d3__namespace.area()
      .x(d => xScale(d.data.x))
      .y0(d => yScale(d[0]))
      .y1(d => yScale(d[1]))
      .curve(this.options.curve);

    // Create axes
    const xAxis = d3__namespace.axisBottom(xScale);
    const yAxis = d3__namespace.axisLeft(yScale);

    // Add axes
    this.chartGroup.append('g')
      .attr('class', 'x-axis')
      .attr('transform', `translate(0, ${this.innerHeight})`)
      .call(xAxis);

    this.chartGroup.append('g')
      .attr('class', 'y-axis')
      .call(yAxis);

    // Add areas
    this.chartGroup.selectAll('.area')
      .data(stackedData)
      .enter()
      .append('path')
      .attr('class', 'area')
      .attr('fill', (d, i) => colorScale(i))
      .attr('d', area)
      .style('opacity', 0.8);

    // Add legend
    const legendItems = keys.map((key, i) => ({
      label: key,
      color: colorScale(i)
    }));
    this.addLegend(legendItems);

    return this;
  }

  /**
   * Prepare data for stacking
   */
  prepareStackData(seriesData) {
    // Get all unique x values
    const allXValues = [...new Set(
      seriesData.flatMap(series => series.data.map(d => d.x))
    )].sort((a, b) => a - b);

    // Create combined data structure
    return allXValues.map(x => {
      const dataPoint = { x };
      
      seriesData.forEach(series => {
        const point = series.data.find(d => d.x === x);
        dataPoint[series.name] = point ? point.y : 0;
      });
      
      return dataPoint;
    });
  }

  /**
   * Update chart with new data
   */
  updateData(newData) {
    this.setData(newData);
    this.render();
    return this;
  }
}

/**
 * Donut Chart implementation (extends PieChart)
 */
class DonutChart extends PieChart {
  constructor(container, options = {}) {
    const defaultOptions = {
      innerRadius: 0.5, // Ratio of outer radius
      showCenterText: true,
      centerText: '',
      centerTextSize: '24px',
      centerTextColor: '#333',
      ...options
    };
    
    super(container, defaultOptions);
  }

  /**
   * Render the donut chart
   */
  render() {
    if (!this.data || this.data.length === 0) {
      console.warn('No data provided for DonutChart');
      return this;
    }

    // Calculate radius if not provided
    const outerRadius = this.options.outerRadius || 
      Math.min(this.innerWidth, this.innerHeight) / 2 - 10;
    
    // Set inner radius based on ratio
    if (typeof this.options.innerRadius === 'number' && this.options.innerRadius < 1) {
      this.options.innerRadius = outerRadius * this.options.innerRadius;
    }

    // Call parent render method
    super.render();

    // Add center text if requested
    if (this.options.showCenterText) {
      this.addCenterText();
    }

    return this;
  }

  /**
   * Add text in the center of the donut
   */
  addCenterText() {
    this.innerWidth / 2;
    this.innerHeight / 2;

    const centerGroup = this.chartGroup.select('g')
      .append('g')
      .attr('class', 'center-text');

    // Main center text
    const centerText = this.options.centerText || this.calculateTotal();
    
    centerGroup.append('text')
      .attr('class', 'center-main-text')
      .attr('text-anchor', 'middle')
      .attr('alignment-baseline', 'middle')
      .style('font-size', this.options.centerTextSize)
      .style('font-weight', 'bold')
      .style('fill', this.options.centerTextColor)
      .text(centerText);

    // Optional subtitle
    if (this.options.centerSubtext) {
      centerGroup.append('text')
        .attr('class', 'center-sub-text')
        .attr('text-anchor', 'middle')
        .attr('alignment-baseline', 'middle')
        .attr('dy', '1.5em')
        .style('font-size', '14px')
        .style('fill', '#666')
        .text(this.options.centerSubtext);
    }
  }

  /**
   * Calculate total value for center display
   */
  calculateTotal() {
    return d3__namespace.sum(this.data, d => d.value);
  }

  /**
   * Update center text
   */
  updateCenterText(text, subtext = null) {
    const centerGroup = this.chartGroup.select('.center-text');
    
    if (!centerGroup.empty()) {
      centerGroup.select('.center-main-text').text(text);
      
      if (subtext !== null) {
        let subtextElement = centerGroup.select('.center-sub-text');
        if (subtextElement.empty()) {
          subtextElement = centerGroup.append('text')
            .attr('class', 'center-sub-text')
            .attr('text-anchor', 'middle')
            .attr('alignment-baseline', 'middle')
            .attr('dy', '1.5em')
            .style('font-size', '14px')
            .style('fill', '#666');
        }
        subtextElement.text(subtext);
      }
    }

    return this;
  }

  /**
   * Create a progress donut (single value with remaining)
   */
  renderProgress(value, total, options = {}) {
    const progressOptions = {
      progressColor: '#3498db',
      remainingColor: '#ecf0f1',
      showPercentage: true,
      ...options
    };

    const percentage = (value / total) * 100;
    const remaining = total - value;

    const progressData = [
      { label: 'Progress', value: value, color: progressOptions.progressColor },
      { label: 'Remaining', value: remaining, color: progressOptions.remainingColor }
    ];

    this.setData(progressData);
    this.options.colors = [progressOptions.progressColor, progressOptions.remainingColor];
    this.options.showLabels = false;

    this.render();

    // Update center text with percentage
    if (progressOptions.showPercentage) {
      this.updateCenterText(`${percentage.toFixed(1)}%`, 'Complete');
    }

    return this;
  }

  /**
   * Create animated progress donut
   */
  animateProgress(targetValue, total, duration = 2000, options = {}) {
    const progressOptions = {
      progressColor: '#3498db',
      remainingColor: '#ecf0f1',
      ...options
    };

    // Start with 0 progress
    this.renderProgress(0, total, progressOptions);

    // Animate to target value
    const self = this;
    const startTime = Date.now();

    function animate() {
      const elapsed = Date.now() - startTime;
      const progress = Math.min(elapsed / duration, 1);
      const currentValue = targetValue * progress;

      self.renderProgress(currentValue, total, progressOptions);

      if (progress < 1) {
        requestAnimationFrame(animate);
      }
    }

    requestAnimationFrame(animate);
    return this;
  }

  /**
   * Add interactive hover effects for donut segments
   */
  addDonutInteractivity() {
    const self = this;
    const paths = this.chartGroup.selectAll('.slice path');

    paths
      .on('mouseover', function(event, d) {
        // Highlight segment
        d3__namespace.select(this)
          .transition()
          .duration(200)
          .style('opacity', 0.8);

        // Update center text with segment info
        const percentage = ((d.endAngle - d.startAngle) / (2 * Math.PI) * 100).toFixed(1);
        self.updateCenterText(d.data.value, `${d.data.label} (${percentage}%)`);

        // Show tooltip
        const tooltipContent = `${d.data.label}: ${d.data.value} (${percentage}%)`;
        self.showTooltip(tooltipContent, event);
      })
      .on('mouseout', function(event, d) {
        // Reset segment
        d3__namespace.select(this)
          .transition()
          .duration(200)
          .style('opacity', 1);

        // Reset center text
        const centerText = self.options.centerText || self.calculateTotal();
        self.updateCenterText(centerText, self.options.centerSubtext);

        self.hideTooltip();
      });

    return this;
  }

  /**
   * Create multi-level donut chart
   */
  renderMultiLevel(innerData, outerData) {
    // Clear previous chart
    this.chartGroup.selectAll('*').remove();

    const centerX = this.innerWidth / 2;
    const centerY = this.innerHeight / 2;
    const maxRadius = Math.min(this.innerWidth, this.innerHeight) / 2 - 10;

    const chartCenter = this.chartGroup.append('g')
      .attr('transform', `translate(${centerX}, ${centerY})`);

    // Inner donut
    this.renderDonutLevel(chartCenter, innerData, maxRadius * 0.3, maxRadius * 0.6, 'inner');

    // Outer donut
    this.renderDonutLevel(chartCenter, outerData, maxRadius * 0.7, maxRadius, 'outer');

    return this;
  }

  /**
   * Render a single level of multi-level donut
   */
  renderDonutLevel(container, data, innerRadius, outerRadius, className) {
    const pie = d3__namespace.pie()
      .value(d => d.value)
      .sort(null);

    const arc = d3__namespace.arc()
      .innerRadius(innerRadius)
      .outerRadius(outerRadius);

    const colorScale = d3__namespace.scaleOrdinal(d3__namespace.schemeCategory10);

    const slices = container.selectAll(`.${className}-slice`)
      .data(pie(data))
      .enter()
      .append('g')
      .attr('class', `${className}-slice`);

    slices.append('path')
      .attr('fill', (d, i) => colorScale(i))
      .attr('stroke', '#fff')
      .attr('stroke-width', 2)
      .attr('d', arc)
      .each(function(d) { this._current = { startAngle: 0, endAngle: 0 }; })
      .transition()
      .duration(1000)
      .attrTween('d', function(d) {
        const interpolate = d3__namespace.interpolate(this._current, d);
        this._current = interpolate(0);
        return function(t