const fs = require('fs');

const data = require('./_data/simple-icons.json');
const { htmlFriendlyToTitle } = require('./scripts/utils.js');
const htmlNamedEntities = require('named-html-entities-json');
const svgpath = require('svgpath');
const svgPathBbox = require('svg-path-bbox');
const parsePath = require('svg-path-segments');

const svgRegexp =
  /^<svg( [^\s]*=".*"){3}><title>.*<\/title><path d=".*"\/><\/svg>\r?\n?$/;
const negativeZerosRegexp = /-0(?=[^\.]|[\s\d\w]|$)/g;

const iconSize = 24;
const iconFloatPrecision = 3;
const iconMaxFloatPrecision = 5;
const iconTolerance = 0.001;

// set env SI_UPDATE_IGNORE to recreate the ignore file
const updateIgnoreFile = process.env.SI_UPDATE_IGNORE === 'true';
const ignoreFile = './.svglint-ignored.json';
const iconIgnored = !updateIgnoreFile ? require(ignoreFile) : {};

const sortObjectByKey = (obj) => {
  return Object.keys(obj)
    .sort()
    .reduce((r, k) => Object.assign(r, { [k]: obj[k] }), {});
};

const sortObjectByValue = (obj) => {
  return Object.keys(obj)
    .sort((a, b) => ('' + obj[a]).localeCompare(obj[b]))
    .reduce((r, k) => Object.assign(r, { [k]: obj[k] }), {});
};

const removeLeadingZeros = (number) => {
  // convert 0.03 to '.03'
  return number.toString().replace(/^(-?)(0)(\.?.+)/, '$1$3');
};

/**
 * Given three points, returns if the middle one (x2, y2) is collinear
 *   to the line formed by the two limit points.
 **/
const collinear = (x1, y1, x2, y2, x3, y3) => {
  return x1 * (y2 - y3) + x2 * (y3 - y1) + x3 * (y1 - y2) === 0;
};

/**
 * Returns the number of digits after the decimal point.
 * @param num The number of interest.
 */
const countDecimals = (num) => {
  if (num && num % 1) {
    let [base, op, trail] = num.toExponential().split(/e([+-])/);
    let elen = parseInt(trail, 10);
    let idx = base.indexOf('.');
    return idx == -1
      ? elen
      : base.length - idx - 1 + (op === '+' ? -elen : elen);
  }
  return 0;
};

/**
 * Get the index at which the first path value of an SVG starts.
 * @param svgFileContent The raw SVG as text.
 */
const getPathDIndex = (svgFileContent) => {
  const pathDStart = '<path d="';
  return svgFileContent.indexOf(pathDStart) + pathDStart.length;
};

/**
 * Get the index at which the text of the first `<title></title>` tag starts.
 * @param svgFileContent The raw SVG as text.
 **/
const getTitleTextIndex = (svgFileContent) => {
  const titleStart = '<title>';
  return svgFileContent.indexOf(titleStart) + titleStart.length;
};

/**
 * Convert a hexadecimal number passed as string to decimal number as integer.
 * @param hex The hexadecimal number representation to convert.
 **/
const hexadecimalToDecimal = (hex) => {
  let result = 0,
    digitValue;
  hex = hex.toLowerCase();
  for (var i = 0; i < hex.length; i++) {
    digitValue = '0123456789abcdefgh'.indexOf(hex[i]);
    result = result * 16 + digitValue;
  }
  return result;
};

if (updateIgnoreFile) {
  process.on('exit', () => {
    // ensure object output order is consistent due to async svglint processing
    const sorted = sortObjectByKey(iconIgnored);
    for (const linterName in sorted) {
      sorted[linterName] = sortObjectByValue(sorted[linterName]);
    }

    fs.writeFileSync(ignoreFile, JSON.stringify(sorted, null, 2) + '\n', {
      flag: 'w',
    });
  });
}

const isIgnored = (linterName, path) => {
  return (
    iconIgnored[linterName] && iconIgnored[linterName].hasOwnProperty(path)
  );
};

const ignoreIcon = (linterName, path, $) => {
  if (!iconIgnored[linterName]) {
    iconIgnored[linterName] = {};
  }

  const title = $.find('title').text();
  const iconName = htmlFriendlyToTitle(title);

  iconIgnored[linterName][path] = iconName;
};

module.exports = {
  rules: {
    elm: {
      svg: 1,
      'svg > title': 1,
      'svg > path': 1,
      '*': false,
    },
    attr: [
      {
        // ensure that the SVG elm has the appropriate attrs
        role: 'img',
        viewBox: `0 0 ${iconSize} ${iconSize}`,
        xmlns: 'http://www.w3.org/2000/svg',
        'rule::selector': 'svg',
        'rule::whitelist': true,
      },
      {
        // ensure that the title elm has the appropriate attr
        'rule::selector': 'svg > title',
        'rule::whitelist': true,
      },
      {
        // ensure that the path element only has the 'd' attr (no style, opacity, etc.)
        d: /^[,a-zA-Z0-9\. -]+$/,
        'rule::selector': 'svg > path',
        'rule::whitelist': true,
      },
    ],
    custom: [
      (reporter, $, ast) => {
        reporter.name = 'icon-title';

        const iconTitleText = $.find('title').text(),
          xmlNamedEntitiesCodepoints = [38, 60, 62],
          xmlNamedEntities = ['amp', 'lt', 'gt'];
        let _validCodepointsRepr = true;

        // avoid character codepoints as hexadecimal representation
        const hexadecimalCodepoints = Array.from(
          iconTitleText.matchAll(/&#x([A-Fa-f0-9]+);/g),
        );
        if (hexadecimalCodepoints.length > 0) {
          _validCodepointsRepr = false;

          hexadecimalCodepoints.forEach((match) => {
            const charHexReprIndex =
              getTitleTextIndex(ast.source) + match.index + 1;
            const charDec = hexadecimalToDecimal(match[1]);

            let charRepr;
            if (xmlNamedEntitiesCodepoints.includes(charDec)) {
              charRepr = `&${
                xmlNamedEntities[xmlNamedEntitiesCodepoints.indexOf(charDec)]
              };`;
            } else if (charDec < 128) {
              charRepr = String.fromCodePoint(charDec);
            } else {
              charRepr = `&#${charDec};`;
            }

            reporter.error(
              `Hexadecimal representation of encoded character "${match[0]}" found at index ${charHexReprIndex}:` +
                ` replace it with "${charRepr}".`,
            );
          });
        }

        // avoid character codepoints as named entities
        const namedEntitiesCodepoints = Array.from(
          iconTitleText.matchAll(/&([A-Za-z0-9]+);/g),
        );
        if (namedEntitiesCodepoints.length > 0) {
          namedEntitiesCodepoints.forEach((match) => {
            const namedEntiyReprIndex =
              getTitleTextIndex(ast.source) + match.index + 1;

            if (!xmlNamedEntities.includes(match[1].toLowerCase())) {
              _validCodepointsRepr = false;
              const namedEntityJsRepr = htmlNamedEntities[match[1]];
              let replacement;

              if (
                namedEntityJsRepr === undefined ||
                namedEntityJsRepr.length != 1
              ) {
                replacement = 'its decimal or literal representation';
              } else {
                const namedEntityDec = namedEntityJsRepr.codePointAt(0);
                if (namedEntityDec < 128) {
                  replacement = `"${namedEntityJsRepr}"`;
                } else {
                  replacement = `"&#${namedEntityDec};"`;
                }
              }

              reporter.error(
                `Named entity representation of encoded character "${match[0]}" found at index ${namedEntiyReprIndex}.` +
                  ` Replace it with ${replacement}.`,
              );
            }
          });
        }

        if (_validCodepointsRepr) {
          // compare encoded title with original title and report error if not equal
          const encodingMatches = Array.from(
              iconTitleText.matchAll(/&(#([0-9]+)|(amp|quot|lt|gt));/g),
            ),
            encodedBuf = [];

          const _indexesToIgnore = [];
          for (let m = 0; m < encodingMatches.length; m++) {
            let index = encodingMatches[m].index;
            for (let r = index; r < index + encodingMatches[m][0].length; r++) {
              _indexesToIgnore.push(r);
            }
          }

          for (let i = iconTitleText.length - 1; i >= 0; i--) {
            if (_indexesToIgnore.includes(i)) {
              encodedBuf.unshift(iconTitleText[i]);
            } else {
              // encode all non ascii characters plus "'&<> (XML named entities)
              let charDecimalCode = iconTitleText.charCodeAt(i);

              if (charDecimalCode > 127) {
                encodedBuf.unshift(`&#${charDecimalCode};`);
              } else if (xmlNamedEntitiesCodepoints.includes(charDecimalCode)) {
                encodedBuf.unshift(
                  `&${
                    xmlNamedEntities[
                      xmlNamedEntitiesCodepoints.indexOf(charDecimalCode)
                    ]
                  };`,
                );
              } else {
                encodedBuf.unshift(iconTitleText[i]);
              }
            }
          }
          const encodedIconTitleText = encodedBuf.join('');
          if (encodedIconTitleText !== iconTitleText) {
            _validCodepointsRepr = false;

            reporter.error(
              `Unencoded unicode characters found in title "${iconTitleText}":` +
                ` rewrite it as "${encodedIconTitleText}".`,
            );
          }

          // check if there are some other encoded characters in decimal notation
          // which shouldn't be encoded
          encodingMatches
            .filter((m) => !isNaN(m[2]))
            .forEach((match) => {
              const decimalNumber = parseInt(match[2]);
              if (decimalNumber < 128) {
                _validCodepointsRepr = false;

                const decimalCodepointCharIndex =
                  getTitleTextIndex(ast.source) + match.index + 1;
                if (xmlNamedEntitiesCodepoints.includes(decimalNumber)) {
                  replacement = `"&${
                    xmlNamedEntities[
                      xmlNamedEntitiesCodepoints.indexOf(decimalNumber)
                    ]
                  };"`;
                } else {
                  replacement = String.fromCharCode(decimalNumber);
                  replacement = replacement == '"' ? `'"'` : `"${replacement}"`;
                }

                reporter.error(
                  `Unnecessary encoded character "${match[0]}" found at index ${decimalCodepointCharIndex}:` +
                    ` replace it with ${replacement}.`,
                );
              }
            });

          if (_validCodepointsRepr) {
            const iconName = htmlFriendlyToTitle(iconTitleText);
            const iconExists = data.icons.some(
              (icon) => icon.title === iconName,
            );
            if (!iconExists) {
              reporter.error(
                `No icon with title "${iconName}" found in simple-icons.json`,
              );
            }
          }
        }
      },
      (reporter, $, ast) => {
        reporter.name = 'icon-size';

        const iconPath = $.find('path').attr('d');
        if (!updateIgnoreFile && isIgnored(reporter.name, iconPath)) {
          return;
        }

        const [minX, minY, maxX, maxY] = svgPathBbox(iconPath);
        const width = +(maxX - minX).toFixed(iconFloatPrecision);
        const height = +(maxY - minY).toFixed(iconFloatPrecision);

        if (width === 0 && height === 0) {
          reporter.error(
            'Path bounds were reported as 0 x 0; check if the path is valid',
          );
          if (updateIgnoreFile) {
            ignoreIcon(reporter.name, iconPath, $);
          }
        } else if (width !== iconSize && height !== iconSize) {
          reporter.error(
            `Size of <path> must be exactly ${iconSize} in one dimension; the size is currently ${width} x ${height}`,
          );
          if (updateIgnoreFile) {
            ignoreIcon(reporter.name, iconPath, $);
          }
        }
      },
      (reporter, $, ast) => {
        reporter.name = 'icon-precision';

        const iconPath = $.find('path').attr('d');
        if (!updateIgnoreFile && isIgnored(reporter.name, iconPath)) {
          return;
        }

        const segments = parsePath(iconPath),
          svgFileContent = $.html();

        segments.forEach((segment) => {
          const precisionMax = Math.max(
            ...segment.params.slice(1).map(countDecimals),
          );
          if (precisionMax > iconMaxFloatPrecision) {
            let errorMsg = `found ${precisionMax} decimals in segment "${iconPath.substring(
              segment.start,
              segment.end,
            )}"`;
            if (segment.chained) {
              let readableChain = iconPath.substring(
                segment.chainStart,
                segment.chainEnd,
              );
              if (readableChain.length > 20) {
                readableChain = `${readableChain.substring(0, 20)}...`;
              }
              errorMsg += ` of chain "${readableChain}"`;
            }
            errorMsg += ` at index ${
              segment.start + getPathDIndex(svgFileContent)
            }`;
            reporter.error(
              `Maximum precision should not be greater than ${iconMaxFloatPrecision}; ${errorMsg}`,
            );
            if (updateIgnoreFile) {
              ignoreIcon(reporter.name, iconPath, $);
            }
          }
        });
      },
      (reporter, $, ast) => {
        reporter.name = 'ineffective-segments';

        const iconPath = $.find('path').attr('d');
        if (!updateIgnoreFile && isIgnored(reporter.name, iconPath)) {
          return;
        }

        const segments = parsePath(iconPath);
        const absSegments = svgpath(iconPath).abs().unshort().segments;

        const lowerMovementCommands = ['m', 'l'];
        const lowerDirectionCommands = ['h', 'v'];
        const lowerCurveCommand = 'c';
        const lowerShorthandCurveCommand = 's';
        const lowerCurveCommands = [
          lowerCurveCommand,
          lowerShorthandCurveCommand,
        ];
        const upperMovementCommands = ['M', 'L'];
        const upperHorDirectionCommand = 'H';
        const upperVerDirectionCommand = 'V';
        const upperDirectionCommands = [
          upperHorDirectionCommand,
          upperVerDirectionCommand,
        ];
        const upperCurveCommand = 'C';
        const upperShorthandCurveCommand = 'S';
        const upperCurveCommands = [
          upperCurveCommand,
          upperShorthandCurveCommand,
        ];
        const curveCommands = [...lowerCurveCommands, ...upperCurveCommands];
        const commands = [
          ...lowerMovementCommands,
          ...lowerDirectionCommands,
          ...upperMovementCommands,
          ...upperDirectionCommands,
          ...curveCommands,
        ];
        const isInvalidSegment = (
          [command, x1Coord, y1Coord, ...rest],
          index,
        ) => {
          if (commands.includes(command)) {
            // Relative directions (h or v) having a length of 0
            if (lowerDirectionCommands.includes(command) && x1Coord === 0) {
              return true;
            }
            // Relative movement (m or l) having a distance of 0
            if (
              index > 0 &&
              lowerMovementCommands.includes(command) &&
              x1Coord === 0 &&
              y1Coord === 0
            ) {
              return true;
            }
            if (
              lowerCurveCommands.includes(command) &&
              x1Coord === 0 &&
              y1Coord === 0
            ) {
              const [x2Coord, y2Coord] = rest;
              if (
                // Relative shorthand curve (s) having a control point of 0
                command === lowerShorthandCurveCommand ||
                // Relative bézier curve (c) having control points of 0
                (command === lowerCurveCommand &&
                  x2Coord === 0 &&
                  y2Coord === 0)
              ) {
                return true;
              }
            }
            if (index > 0) {
              let [yPrevCoord, xPrevCoord] = [
                ...absSegments[index - 1],
              ].reverse();
              // If the previous command was a direction one, we need to iterate back until we find the missing coordinates
              if (upperDirectionCommands.includes(xPrevCoord)) {
                xPrevCoord = undefined;
                yPrevCoord = undefined;
                let idx = index;
                while (
                  --idx > 0 &&
                  (xPrevCoord === undefined || yPrevCoord === undefined)
                ) {
                  let [yPrevCoordDeep, xPrevCoordDeep] = [
                    ...absSegments[idx],
                  ].reverse();
                  // If the previous command was a horizontal movement, we need to consider the single coordinate as x
                  if (upperHorDirectionCommand === xPrevCoordDeep) {
                    xPrevCoordDeep = yPrevCoordDeep;
                    yPrevCoordDeep = undefined;
                  }
                  // If the previous command was a vertical movement, we need to consider the single coordinate as y
                  if (upperVerDirectionCommand === xPrevCoordDeep) {
                    xPrevCoordDeep = undefined;
                  }
                  if (
                    xPrevCoord === undefined &&
                    xPrevCoordDeep !== undefined
                  ) {
                    xPrevCoord = xPrevCoordDeep;
                  }
                  if (
                    yPrevCoord === undefined &&
                    yPrevCoordDeep !== undefined
                  ) {
                    yPrevCoord = yPrevCoordDeep;
                  }
                }
              }

              if (upperCurveCommands.includes(command)) {
                const [x2Coord, y2Coord, xCoord, yCoord] = rest;
                // Absolute shorthand curve (S) having the same coordinate as the previous segment and a control point equal to the ending point
                if (
                  upperShorthandCurveCommand === command &&
                  x1Coord === xPrevCoord &&
                  y1Coord === yPrevCoord &&
                  x1Coord === x2Coord &&
                  y1Coord === y2Coord
                ) {
                  return true;
                }
                // Absolute bézier curve (C) having the same coordinate as the previous segment and last control point equal to the ending point
                if (
                  upperCurveCommand === command &&
                  x1Coord === xPrevCoord &&
                  y1Coord === yPrevCoord &&
                  x2Coord === xCoord &&
                  y2Coord === yCoord
                ) {
                  return true;
                }
              }

              return (
                // Absolute horizontal direction (H) having the same x coordinate as the previous segment
                (upperHorDirectionCommand === command &&
                  x1Coord === xPrevCoord) ||
                // Absolute vertical direction (V) having the same y coordinate as the previous segment
                (upperVerDirectionCommand === command &&
                  x1Coord === yPrevCoord) ||
                // Absolute movement (M or L) having the same coordinate as the previous segment
                (upperMovementCommands.includes(command) &&
                  x1Coord === xPrevCoord &&
                  y1Coord === yPrevCoord)
              );
            }
          }
        };

        const svgFileContent = $.html();

        segments.forEach((segment, index) => {
          if (isInvalidSegment(segment.params, index)) {
            const [command, x1, y1, ...rest] = segment.params;

            let errorMsg = `Innefective segment "${iconPath.substring(
                segment.start,
                segment.end,
              )}" found`,
              resolutionTip = 'should be removed';

            if (curveCommands.includes(command)) {
              const [x2, y2, x, y] = rest;

              if (
                command === lowerShorthandCurveCommand &&
                (x2 !== 0 || y2 !== 0)
              ) {
                resolutionTip = `should be "l${removeLeadingZeros(
                  x2,
                )} ${removeLeadingZeros(y2)}" or removed`;
              }
              if (command === upperShorthandCurveCommand) {
                resolutionTip = `should be "L${removeLeadingZeros(
                  x2,
                )} ${removeLeadingZeros(y2)}" or removed`;
              }
              if (command === lowerCurveCommand && (x !== 0 || y !== 0)) {
                resolutionTip = `should be "l${removeLeadingZeros(
                  x,
                )} ${removeLeadingZeros(y)}" or removed`;
              }
              if (command === upperCurveCommand) {
                resolutionTip = `should be "L${removeLeadingZeros(
                  x,
                )} ${removeLeadingZeros(y)}" or removed`;
              }
            }

            if (segment.chained) {
              let readableChain = iconPath.substring(
                segment.chainStart,
                segment.chainEnd,
              );
              if (readableChain.length > 20) {
                readableChain = `${chain.substring(0, 20)}...`;
              }
              errorMsg += ` in chain "${readableChain}"`;
            }
            errorMsg += ` at index ${
              segment.start + getPathDIndex(svgFileContent)
            }`;

            reporter.error(`${errorMsg} (${resolutionTip})`);

            if (updateIgnoreFile) {
              ignoreIcon(reporter.name, iconPath, $);
            }
          }
        });
      },
      (reporter, $, ast) => {
        reporter.name = 'collinear-segments';

        const iconPath = $.find('path').attr('d');
        if (!updateIgnoreFile && isIgnored(reporter.name, iconPath)) {
          return;
        }

        /**
         * Extracts collinear coordinates from SVG path straight lines
         *   (does not extracts collinear coordinates from curves).
         **/
        const getCollinearSegments = (iconPath) => {
          const segments = parsePath(iconPath),
            collinearSegments = [],
            straightLineCommands = 'HhVvLlMm',
            zCommands = 'Zz';

          let currLine = [],
            currAbsCoord = [undefined, undefined],
            startPoint,
            _inStraightLine = false,
            _nextInStraightLine = false,
            _resetStartPoint = false;

          for (let s = 0; s < segments.length; s++) {
            let seg = segments[s].params,
              cmd = seg[0],
              nextCmd = s + 1 < segments.length ? segments[s + 1][0] : null;

            if (cmd === 'L') {
              currAbsCoord[0] = seg[1];
              currAbsCoord[1] = seg[2];
            } else if (cmd === 'l') {
              currAbsCoord[0] =
                (!currAbsCoord[0] ? 0 : currAbsCoord[0]) + seg[1];
              currAbsCoord[1] =
                (!currAbsCoord[1] ? 0 : currAbsCoord[1]) + seg[2];
            } else if (cmd === 'm') {
              currAbsCoord[0] =
                (!currAbsCoord[0] ? 0 : currAbsCoord[0]) + seg[1];
              currAbsCoord[1] =
                (!currAbsCoord[1] ? 0 : currAbsCoord[1]) + seg[2];
              startPoint = undefined;
            } else if (cmd === 'M') {
              currAbsCoord[0] = seg[1];
              currAbsCoord[1] = seg[2];
              startPoint = undefined;
            } else if (cmd === 'H') {
              currAbsCoord[0] = seg[1];
            } else if (cmd === 'h') {
              currAbsCoord[0] =
                (!currAbsCoord[0] ? 0 : currAbsCoord[0]) + seg[1];
            } else if (cmd === 'V') {
              currAbsCoord[1] = seg[1];
            } else if (cmd === 'v') {
              currAbsCoord[1] =
                (!currAbsCoord[1] ? 0 : currAbsCoord[1]) + seg[1];
            } else if (cmd === 'C') {
              currAbsCoord[0] = seg[5];
              currAbsCoord[1] = seg[6];
            } else if (cmd === 'a') {
              currAbsCoord[0] =
                (!currAbsCoord[0] ? 0 : currAbsCoord[0]) + seg[6];
              currAbsCoord[1] =
                (!currAbsCoord[1] ? 0 : currAbsCoord[1]) + seg[7];
            } else if (cmd === 'A') {
              currAbsCoord[0] = seg[6];
              currAbsCoord[1] = seg[7];
            } else if (cmd === 's') {
              currAbsCoord[0] =
                (!currAbsCoord[0] ? 0 : currAbsCoord[0]) + seg[1];
              currAbsCoord[1] =
                (!currAbsCoord[1] ? 0 : currAbsCoord[1]) + seg[2];
            } else if (cmd === 'S') {
              currAbsCoord[0] = seg[1];
              currAbsCoord[1] = seg[2];
            } else if (cmd === 't') {
              currAbsCoord[0] =
                (!currAbsCoord[0] ? 0 : currAbsCoord[0]) + seg[1];
              currAbsCoord[1] =
                (!currAbsCoord[1] ? 0 : currAbsCoord[1]) + seg[2];
            } else if (cmd === 'T') {
              currAbsCoord[0] = seg[1];
              currAbsCoord[1] = seg[2];
            } else if (cmd === 'c') {
              currAbsCoord[0] =
                (!currAbsCoord[0] ? 0 : currAbsCoord[0]) + seg[5];
              currAbsCoord[1] =
                (!currAbsCoord[1] ? 0 : currAbsCoord[1]) + seg[6];
            } else if (cmd === 'Q') {
              currAbsCoord[0] = seg[3];
              currAbsCoord[1] = seg[4];
            } else if (cmd === 'q') {
              currAbsCoord[0] =
                (!currAbsCoord[0] ? 0 : currAbsCoord[0]) + seg[3];
              currAbsCoord[1] =
                (!currAbsCoord[1] ? 0 : currAbsCoord[1]) + seg[4];
            } else if (zCommands.includes(cmd)) {
              // Overlapping in Z should be handled in another rule
              currAbsCoord = [startPoint[0], startPoint[1]];
              _resetStartPoint = true;
            } else {
              throw new Error(`"${cmd}" command not handled`);
            }

            if (startPoint === undefined) {
              startPoint = [currAbsCoord[0], currAbsCoord[1]];
            } else if (_resetStartPoint) {
              startPoint = undefined;
              _resetStartPoint = false;
            }

            _nextInStraightLine = straightLineCommands.includes(nextCmd);
            let _exitingStraightLine = _inStraightLine && !_nextInStraightLine;
            _inStraightLine = straightLineCommands.includes(cmd);

            if (_inStraightLine) {
              currLine.push([currAbsCoord[0], currAbsCoord[1]]);
            } else {
              if (_exitingStraightLine) {
                if (straightLineCommands.includes(cmd)) {
                  currLine.push([currAbsCoord[0], currAbsCoord[1]]);
                }
                // Get collinear coordinates
                for (let p = 1; p < currLine.length - 1; p++) {
                  let _collinearCoord = collinear(
                    currLine[p - 1][0],
                    currLine[p - 1][1],
                    currLine[p][0],
                    currLine[p][1],
                    currLine[p + 1][0],
                    currLine[p + 1][1],
                  );
                  if (_collinearCoord) {
                    collinearSegments.push(
                      segments[s - currLine.length + p + 1],
                    );
                  }
                }
              }
              currLine = [];
            }
          }

          return collinearSegments;
        };

        const collinearSegments = getCollinearSegments(iconPath),
          pathDIndex = getPathDIndex($.html());
        collinearSegments.forEach((segment) => {
          let errorMsg = `Collinear segment "${iconPath.substring(
            segment.start,
            segment.end,
          )}" found`;
          if (segment.chained) {
            let readableChain = iconPath.substring(
              segment.chainStart,
              segment.chainEnd,
            );
            if (readableChain.length > 20) {
              readableChain = `${readableChain.substring(0, 20)}...`;
            }
            errorMsg += ` in chain "${readableChain}"`;
          }
          errorMsg += ` at index ${
            segment.start + pathDIndex
          } (should be removed)`;
          reporter.error(errorMsg);
        });

        if (collinearSegments.length) {
          if (updateIgnoreFile) {
            ignoreIcon(reporter.name, iconPath, $);
          }
        }
      },
      (reporter, $, ast) => {
        reporter.name = 'extraneous';

        if (!svgRegexp.test(ast.source)) {
          reporter.error(
            'Unexpected character(s), most likely extraneous whitespace, detected in SVG markup',
          );
        }
      },
      (reporter, $, ast) => {
        reporter.name = 'negative-zeros';

        const iconPath = $.find('path').attr('d');
        if (!updateIgnoreFile && isIgnored(reporter.name, iconPath)) {
          return;
        }

        // Find negative zeros inside path
        const negativeZeroMatches = Array.from(
          iconPath.matchAll(negativeZerosRegexp),
        );
        if (negativeZeroMatches.length) {
          // Calculate the index for each match in the file
          const svgFileContent = $.html();
          const pathDIndex = getPathDIndex(svgFileContent);

          negativeZeroMatches.forEach((match) => {
            const negativeZeroFileIndex = match.index + pathDIndex;
            const previousChar = svgFileContent[negativeZeroFileIndex - 1];
            const replacement = '0123456789'.includes(previousChar)
              ? ' 0'
              : '0';
            reporter.error(
              `Found "-0" at index ${negativeZeroFileIndex} (should be "${replacement}")`,
            );
          });
        }
      },
      (reporter, $, ast) => {
        reporter.name = 'icon-centered';

        const iconPath = $.find('path').attr('d');
        if (!updateIgnoreFile && isIgnored(reporter.name, iconPath)) {
          return;
        }

        const [minX, minY, maxX, maxY] = svgPathBbox(iconPath);
        const targetCenter = iconSize / 2;
        const centerX = +((minX + maxX) / 2).toFixed(iconFloatPrecision);
        const devianceX = centerX - targetCenter;
        const centerY = +((minY + maxY) / 2).toFixed(iconFloatPrecision);
        const devianceY = centerY - targetCenter;

        if (
          Math.abs(devianceX) > iconTolerance ||
          Math.abs(devianceY) > iconTolerance
        ) {
          reporter.error(
            `<path> must be centered at (${targetCenter}, ${targetCenter}); the center is currently (${centerX}, ${centerY})`,
          );
          if (updateIgnoreFile) {
            ignoreIcon(reporter.name, iconPath, $);
          }
        }
      },
      (reporter, $, ast) => {
        reporter.name = 'path-format';

        const iconPath = $.find('path').attr('d');

        const validPathFormatRegex = /^[Mm][MmZzLlHhVvCcSsQqTtAaEe0-9-,.\s]+$/;
        if (!validPathFormatRegex.test(iconPath)) {
          let errorMsg = 'Invalid path format',
            reason;

          if (!/^[Mm]/.test(iconPath)) {
            // doesn't start with moveto
            reason = `should start with \"moveto\" command (\"M\" or \"m\"), but starts with \"${iconPath[0]}\"`;
            reporter.error(`${errorMsg}: ${reason}`);
          }

          const validPathCharacters = 'MmZzLlHhVvCcSsQqTtAaEe0123456789-,. ',
            invalidCharactersMsgs = [],
            pathDIndex = getPathDIndex($.html());

          for (let [i, char] of Object.entries(iconPath)) {
            if (validPathCharacters.indexOf(char) === -1) {
              invalidCharactersMsgs.push(
                `"${char}" at index ${pathDIndex + parseInt(i)}`,
              );
            }
          }

          // contains invalid characters
          if (invalidCharactersMsgs.length > 0) {
            reason = `unexpected character${
              invalidCharactersMsgs.length > 1 ? 's' : ''
            } found`;
            reason += ` (${invalidCharactersMsgs.join(', ')})`;
            reporter.error(`${errorMsg}: ${reason}`);
          }
        }
      },
      (reporter, $, ast) => {
        reporter.name = 'svg-format';

        // Don't allow explicit '</path>' closing tag
        if (ast.source.includes('</path>')) {
          const reason =
            `found a closing "path" tag at index ${ast.source.indexOf(
              '</path>',
            )}.` +
            " The path should be self-closing, use '/>' instead of '></path>'.";
          reporter.error(`Invalid SVG content format: ${reason}`);
        }
      },
    ],
  },
};