import {path} from "d3-path";
import constant from "./constant.js";
import curveLinear from "./curve/linear.js";
import line from "./line.js";
import {x as pointX, y as pointY} from "./point.js";

export default function() {
  var x0 = pointX,
      x1 = null,
      y0 = constant(0),
      y1 = pointY,
      defined = constant(true),
      context = null,
      curve = curveLinear,
      output = null;

  function area(data) {
    var i,
        j,
        k,
        n = data.length,
        d,
        defined0 = false,
        buffer,
        x0z = new Array(n),
        y0z = new Array(n);

    if (context == null) output = curve(buffer = path());

    for (i = 0; i <= n; ++i) {
      if (!(i < n && defined(d = data[i], i, data)) === defined0) {
        if (defined0 = !defined0) {
          j = i;
          output.areaStart();
          output.lineStart();
        } else {
          output.lineEnd();
          output.lineStart();
          for (k = i - 1; k >= j; --k) {
            output.point(x0z[k], y0z[k]);
          }
          output.lineEnd();
          output.areaEnd();
        }
      }
      if (defined0) {
        x0z[i] = +x0(d, i, data), y0z[i] = +y0(d, i, data);
        output.point(x1 ? +x1(d, i, data) : x0z[i], y1 ? +y1(d, i, data) : y0z[i]);
      }
    }

    if (buffer) return output = null, buffer + "" || null;
  }

  function arealine() {
    return line().defined(defined).curve(curve).context(context);
  }

  area.x = function(_) {
    return arguments.length ? (x0 = typeof _ === "function" ? _ : constant(+_), x1 = null, area) : x0;
  };

  area.x0 = function(_) {
    return arguments.length ? (x0 = typeof _ === "function" ? _ : constant(+_), area) : x0;
  };

  area.x1 = function(_) {
    return arguments.length ? (x1 = _ == null ? null : typeof _ === "function" ? _ : constant(+_), area) : x1;
  };

  area.y = function(_) {
    return arguments.length ? (y0 = typeof _ === "function" ? _ : constant(+_), y1 = null, area) : y0;
  };

  area.y0 = function(_) {
    return arguments.length ? (y0 = typeof _ === "function" ? _ : constant(+_), area) : y0;
  };

  area.y1 = function(_) {
    return arguments.length ? (y1 = _ == null ? null : typeof _ === "function" ? _ : constant(+_), area) : y1;
  };

  area.lineX0 =
  area.lineY0 = function() {
    return arealine().x(x0).y(y0);
  };

  area.lineY1 = function() {
    return arealine().x(x0).y(y1);
  };

  area.lineX1 = function() {
    return arealine().x(x1).y(y0);
  };

  area.defined = function(_) {
    return arguments.length ? (defined = typeof _ === "function" ? _ : constant(!!_), area) : defined;
  };

  area.curve = function(_) {
    return arguments.length ? (curve = _, context != null && (output = curve(context)), area) : curve;
  };

  area.context = function(_) {
    return arguments.length ? (_ == null ? context = output = null : output = curve(context = _), area) : context;
  };

  return area;
}