Rename Core to avoid collisions with other packages (i.e. GraphViz) (#1057)

* Rename 'Core' to 'XcodeGenCore'

* Update CHANGELOG.md

* Update CHANGELOG.md

Sources/XcodeGenCore/StringDiff.swift

@@ -0,0 +1,97 @@
+import Foundation
+
+// https://gist.github.com/kristopherjohnson/543687c763cd6e524c91
+
+/// Find first differing character between two strings
+///
+/// :param: s1 First String
+/// :param: s2 Second String
+///
+/// :returns: .DifferenceAtIndex(i) or .NoDifference
+public func firstDifferenceBetweenStrings(_ s1: String, _ s2: String) -> FirstDifferenceResult {
+    let len1 = s1.count
+    let len2 = s2.count
+
+    let lenMin = min(len1, len2)
+
+    for i in 0..<lenMin {
+        if (s1 as NSString).character(at: i) != (s2 as NSString).character(at: i) {
+            return .DifferenceAtIndex(i)
+        }
+    }
+
+    if len1 < len2 {
+        return .DifferenceAtIndex(len1)
+    }
+
+    if len2 < len1 {
+        return .DifferenceAtIndex(len2)
+    }
+
+    return .NoDifference
+}
+
+/// Create a formatted String representation of difference between strings
+///
+/// :param: s1 First string
+/// :param: s2 Second string
+///
+/// :returns: a string, possibly containing significant whitespace and newlines
+public func prettyFirstDifferenceBetweenStrings(_ s1: String, _ s2: String, previewPrefixLength: Int = 25, previewSuffixLength: Int = 25) -> String {
+    let firstDifferenceResult = firstDifferenceBetweenStrings(s1, s2)
+
+    func diffString(at index: Int, _ s1: String, _ s2: String) -> String {
+        let markerArrow = "\u{2b06}" // "⬆"
+        let ellipsis = "\u{2026}" // "…"
+
+        /// Given a string and a range, return a string representing that substring.
+        ///
+        /// If the range starts at a position other than 0, an ellipsis
+        /// will be included at the beginning.
+        ///
+        /// If the range ends before the actual end of the string,
+        /// an ellipsis is added at the end.
+        func windowSubstring(_ s: String, _ range: NSRange) -> String {
+            let validRange = NSMakeRange(range.location, min(range.length, s.count - range.location))
+            let substring = (s as NSString).substring(with: validRange)
+
+            let prefix = range.location > 0 ? ellipsis : ""
+            let suffix = (s.count - range.location > range.length) ? ellipsis : ""
+
+            return "\(prefix)\(substring)\(suffix)"
+        }
+
+        // Show this many characters before and after the first difference
+        let windowLength = previewPrefixLength + 1 + previewSuffixLength
+
+        let windowIndex = max(index - previewPrefixLength, 0)
+        let windowRange = NSMakeRange(windowIndex, windowLength)
+
+        let sub1 = windowSubstring(s1, windowRange)
+        let sub2 = windowSubstring(s2, windowRange)
+
+        let markerPosition = min(previewSuffixLength, index) + (windowIndex > 0 ? 1 : 0)
+
+        let markerPrefix = String(repeating: " ", count: markerPosition)
+        let markerLine = "\(markerPrefix)\(markerArrow)"
+
+        return "Difference at index \(index):\n\(sub1)\n\(sub2)\n\(markerLine)"
+    }
+
+    switch firstDifferenceResult {
+    case .NoDifference: return "No difference"
+    case let .DifferenceAtIndex(index): return diffString(at: index, s1, s2)
+    }
+}
+
+/// Result type for firstDifferenceBetweenStrings()
+public enum FirstDifferenceResult {
+    /// Strings are identical
+    case NoDifference
+
+    /// Strings differ at the specified index.
+    ///
+    /// This could mean that characters at the specified index are different,
+    /// or that one string is longer than the other
+    case DifferenceAtIndex(Int)
+}