import * as d3 from 'd3';

export default () => {
  // defaults
  const options = {
    donutWidth: 15,
    endval: 0.66,
    width: 80,
    height: 80,
    duration: 1500,
    colors: [ '#7ED321', '#E3E3E3' ]
  };

  // start
  const donut = selection => {
    const datasetBase = [
      { color: 1, val: 100 }
    ];

    const dataset = [
      { color: 0, val: options.endval * 100 },
      { color: 1, val: 100 - (options.endval * 100) }
    ];

    const radius = Math.min(options.width, options.height) / 2;

    const svg = selection
      .append('svg')
      .attr('width', options.width)
      .attr('height', options.height);

    const arc = d3.arc()
      .innerRadius(radius - options.donutWidth)
      .outerRadius(radius);

    const pie = d3.pie()
      .value(d => d.val)
      .sort(null);

    // base donut without animation 100%
    const groupBase = svg.append('g')
      .attr('transform', `translate(${options.width / 2}, ${options.height / 2})`);

    groupBase.selectAll('path')
      .data(pie(datasetBase))
      .enter()
      .append('path')
      .attr('d', arc)
      .attr('fill', d => options.colors[d.data.color]);

    // fill x% from donut, animate!
    const group = svg.append('g')
      .attr('transform', `translate(${options.width / 2}, ${options.height / 2})`);

    group.selectAll('path')
      .data(pie(dataset))
      .enter()
      .append('path')
      .attr('fill', d => options.colors[d.data.color])
      .transition()
      .delay((d, i) => ((100 - d.value) * options.duration / 100 * i))
      .duration(d => (options.duration * d.value / 100))
      .attrTween('d', d => {
        const i = d3.interpolate(d.startAngle + 0.1, d.endAngle);

        return t => {
          d.endAngle = i(t);
          return arc(d);
        };
      });
  };

  // "setter"
  donut.options = input => {
    Object.assign(options, input);

    return donut;
  };

  return donut;
};