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//
// KatexUtils.swift
// iTexSnip
//
// Created by Navan Chauhan on 10/13/24.
//
import Foundation
func change(
_ inputStr: String, oldInst: String, newInst: String, oldSurrL: Character, oldSurrR: Character,
newSurrL: String, newSurrR: String
) -> String {
var result = ""
var i = 0
let n = inputStr.count
let inputArray = Array(inputStr)
while i < n {
if i + oldInst.count <= n
&& inputStr[
inputStr.index(
inputStr.startIndex, offsetBy: i)..<inputStr.index(
inputStr.startIndex, offsetBy: i + oldInst.count)] == oldInst
{
let start = i + oldInst.count
if start < n && inputArray[start] == oldSurrL {
var count = 1
var j = start + 1
var escaped = false
while j < n && count > 0 {
if inputArray[j] == "\\" && !escaped {
escaped = true
j += 1
continue
}
if inputArray[j] == oldSurrR && !escaped {
count -= 1
if count == 0 {
break
}
} else if inputArray[j] == oldSurrL && !escaped {
count += 1
}
escaped = false
j += 1
}
if count == 0 {
let innerContent = String(inputArray[(start + 1)..<j])
result += newInst + newSurrL + innerContent + newSurrR
i = j + 1
continue
} else {
result += newInst + newSurrL
i = start + 1
continue
}
}
}
result.append(inputArray[i])
i += 1
}
if oldInst != newInst && result.contains(oldInst + String(oldSurrL)) {
return change(
result, oldInst: oldInst, newInst: newInst, oldSurrL: oldSurrL, oldSurrR: oldSurrR,
newSurrL: newSurrL, newSurrR: newSurrR)
}
return result
}
func findSubstringPositions(_ string: String, substring: String) -> [Int] {
var positions: [Int] = []
var searchRange = string.startIndex..<string.endIndex
while let range = string.range(of: substring, options: [], range: searchRange) {
let position = string.distance(from: string.startIndex, to: range.lowerBound)
positions.append(position)
searchRange = range.upperBound..<string.endIndex
}
return positions
}
func rmDollarSurr(content: String) -> String {
let pattern = try! NSRegularExpression(pattern: "\\\\[a-zA-Z]+\\$.*?\\$|\\$.*?\\$", options: [])
var newContent = content
let matches = pattern.matches(
in: content, options: [], range: NSRange(content.startIndex..<content.endIndex, in: content))
for match in matches.reversed() {
let matchedString = (content as NSString).substring(with: match.range)
if !matchedString.starts(with: "\\") {
let strippedMatch = matchedString.replacingOccurrences(of: "$", with: "")
newContent = newContent.replacingOccurrences(of: matchedString, with: " \(strippedMatch) ")
}
}
return newContent
}
func changeAll(
inputStr: String, oldInst: String, newInst: String, oldSurrL: Character, oldSurrR: Character,
newSurrL: String, newSurrR: String
) -> String {
let positions = findSubstringPositions(inputStr, substring: oldInst + String(oldSurrL))
var result = inputStr
for pos in positions.reversed() {
let startIndex = result.index(result.startIndex, offsetBy: pos)
let substring = String(result[startIndex..<result.endIndex])
let changedSubstring = change(
substring, oldInst: oldInst, newInst: newInst, oldSurrL: oldSurrL, oldSurrR: oldSurrR,
newSurrL: newSurrL, newSurrR: newSurrR)
result.replaceSubrange(startIndex..<result.endIndex, with: changedSubstring)
}
return result
}
func toKatex(formula: String) -> String {
var res = formula
res = changeAll(
inputStr: res, oldInst: "\\mbox ", newInst: " ", oldSurrL: "{", oldSurrR: "}", newSurrL: "",
newSurrR: "")
res = changeAll(
inputStr: res, oldInst: "\\mbox", newInst: " ", oldSurrL: "{", oldSurrR: "}", newSurrL: "",
newSurrR: "")
res = res.replacingOccurrences(of: "\\[", with: "")
res = res.replacingOccurrences(of: "\\]", with: "")
res = res.replacingOccurrences(
of: "\\\\[?.!,\'\"](?:\\s|$)", with: "", options: .regularExpression)
res = rmDollarSurr(content: res)
res = res.replacingOccurrences(of: " +", with: " ", options: .regularExpression)
return res.trimmingCharacters(in: .whitespacesAndNewlines)
}
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