Replace Foundation replacingOccurrences(of:with:) and percent encoding

[madsodgaard]

Part of apple/swift-openapi-generator#868

Introduces a Swift impl of replacingOccurrences(of:with:), addingPercentEncoding and removingPercentEncoding.

The percent encoding were inspired by impl in swift-foundation: https://github.com/swiftlang/swift-foundation/blob/aee1d337039b5b2a1f0c3b7f83baa950dac3a84e/Sources/FoundationEssentials/URL/URLParser.swift

I also added tests to verify behaviour with Foundation.

[czechboy0]

Thanks @madsodgaard - got some suggestions on this one

[czechboy0]

Suggested change

	@inlinable func replacingOccurrences<Target: StringProtocol, Replacement: StringProtocol>(
	of target: Target,
	with replacement: Replacement,
	maxReplacements: Int = .max
	) -> String {
	guard !target.isEmpty, maxReplacements > 0 else { return String(self) }
	var result = ""
	result.reserveCapacity(self.count)
	var currentIndex = self.startIndex
	let end = self.endIndex
	var replacementsCount = 0
	// Keeps track of the last un-appended chunk
	var chunkStartIndex = currentIndex
	while currentIndex < end {
	if replacementsCount == maxReplacements { break }
	let remainder = self[currentIndex...]
	if remainder.starts(with: target) {
	result.append(contentsOf: self[chunkStartIndex..<currentIndex])
	result.append(contentsOf: replacement)
	currentIndex = self.index(currentIndex, offsetBy: target.count)
	chunkStartIndex = currentIndex
	replacementsCount += 1
	} else {
	currentIndex = self.index(after: currentIndex)
	}
	}
	// Append any remaining characters after the final match
	if chunkStartIndex < end { result.append(contentsOf: self[chunkStartIndex...]) }
	return result
	}
	@inlinable func replacingOccurrences<Replacement: StringProtocol>(
	of target: String,
	with replacement: Replacement,
	maxReplacements: Int = .max
	) -> String {
	guard !target.isEmpty, maxReplacements > 0 else { return String(self) }
	var result = ""
	result.reserveCapacity(self.count)
	var searchStart = self.startIndex
	var replacements = 0
	while
	replacements < maxReplacements,
	let foundRange = self.range(of: target, range: searchStart..<self.endIndex)
	{
	result.append(contentsOf: self[searchStart..<foundRange.lowerBound])
	result.append(contentsOf: replacement)
	searchStart = foundRange.upperBound
	replacements += 1
	}
	result.append(contentsOf: self[searchStart..<self.endIndex])
	return result
	}

I couldn't convince myself that currentIndex = self.index(currentIndex, offsetBy: target.count) was actually always going to be correct, so how about this alternative that sidesteps that problem, and only ever uses indexes with the string that originated them?

[madsodgaard]

sounds good 👍

[madsodgaard]

Whoops, I was a bit too quick here. range(of:) is not in FoundationEssentials. When are you worried that the above code would be incorrect?