Pad list of strings

StringArray+Padding.swift

extension Collection where Element == String {

    func pad(to commonString: String) -> [String] {
        let stringsAndWidths = self.map { string -> (String, Int) in
            return (string, string[string.startIndex ..< string.range(of: commonString)!.lowerBound].count)
        }
        let marginWidth = stringsAndWidths.map { $0.1 }.reduce(0) { result, count -> Int in Swift.max(result, count) }

        return stringsAndWidths.map { tuple -> String in
            let (string, width) = tuple
            return string.prefix(width).padding(toLength: marginWidth, withPad: " ", startingAt: 0) + tuple.0.suffix(tuple.0.count - tuple.1)
        }
    }
    
}


let input = """
func foo() { return NSLocalizedString("foo", comment: "this is foo") }
func alphaBetaCharlie() { return NSLocalizedString("alpha beta charlie", comment: "this is alpha beta charlie") }
func alpha() { return NSLocalizedString("alpha", comment: "this is alpha") }
"""

let strings = input.split(separator: "\n").map { String($0) }

let fixed = strings
    .pad(to: "{ return NSLocalizedString")
    .pad(to: "comment: ")

for string in fixed {
    print(string)
}

// Output:
//
// func foo()              { return NSLocalizedString("foo",                comment: "this is foo") }
// func alphaBetaCharlie() { return NSLocalizedString("alpha beta charlie", comment: "this is alpha beta charlie") }
// func alpha()            { return NSLocalizedString("alpha",              comment: "this is alpha") }