harmonize-path-data.js

// @info
//   Takes normalized path data and harmonizes it so that each subpath starts with "M" seg, followed by one or
//   more "C" or "L" segs, optionally followed by "Z" seg.
let harmonizePathData = (pathData) => {
  if (!pathData.find(($0) => $0.type === "C" || $0.type === "L")) return [];

  let simplifiedPathData = [];
  let lastType = null;

  let currentX = 0;
  let currentY = 0;

  let subpathX = 0;
  let subpathY = 0;

  for (let seg of pathData) {
    if (seg.type === "M") {
      // M is redundant if it is followed by another M
      if (lastType === "M") {
        simplifiedPathData.pop();
      }

      simplifiedPathData.push(seg);

      currentX = seg.values[0];
      currentY = seg.values[1];
      subpathX = seg.values[0];
      subpathY = seg.values[1];
    }
    else if (seg.type === "L") {
      // Insert explicit M if the last seg is Z
      if (lastType === "Z") {
        simplifiedPathData.push({type: "M", values: [subpathX, subpathY]});
      }

      simplifiedPathData.push(seg);

      currentX = seg.values[0];
      currentY = seg.values[1];
    }
    else if (seg.type === "C") {
      // Insert explicit M if the last seg is Z
      if (lastType === "Z") {
        simplifiedPathData.push({type: "M", values: [subpathX, subpathY]});
      }

      simplifiedPathData.push(seg);

      currentX = seg.values[4];
      currentY = seg.values[5];

    }
    else if (seg.type === "Z") {
      // Insert explicit L if the subpath is not closed
      if (currentX !== subpathX || currentY !== subpathY) {
        simplifiedPathData.push({type: "L", values: [subpathX, subpathY]});
      }

      simplifiedPathData.push(seg);

      currentX = subpathX;
      currentY = subpathY;
    }

    lastType = seg.type;
  }

  return simplifiedPathData;
};