From 73d26bf458d26af9d78162b401b892e6076943b7 Mon Sep 17 00:00:00 2001
From: Paul Taykalo <tt.kilew@gmail.com>
Date: Fri, 25 Oct 2019 22:29:27 +0300
Subject: [PATCH] Use firsIndexAssumingSorted when searching in sorted arrays

---
 .../RandomAccessCollection+Swiftlint.swift    | 57 +++++++++++++++++++
 .../Extensions/SyntaxMap+SwiftLint.swift      | 46 ++-------------
 2 files changed, 62 insertions(+), 41 deletions(-)
 create mode 100644 Source/SwiftLintFramework/Extensions/RandomAccessCollection+Swiftlint.swift

diff --git a/Source/SwiftLintFramework/Extensions/RandomAccessCollection+Swiftlint.swift b/Source/SwiftLintFramework/Extensions/RandomAccessCollection+Swiftlint.swift
new file mode 100644
index 0000000000..3b97b7c803
--- /dev/null
+++ b/Source/SwiftLintFramework/Extensions/RandomAccessCollection+Swiftlint.swift
@@ -0,0 +1,57 @@
+internal extension RandomAccessCollection where Index == Int {
+    /// Returns the first index in which an element of the collection satisfies
+    /// the given predicate. The collection assumed to be sorted. If collection is not have sorted values
+    /// the result is undefined
+    ///
+    /// The idea  is to get first index of a function where predicate starting to return true values.
+    ///
+    ///       let values = [1,2,3,4,5]
+    ///       let idx = values.firstIndexAssumingSorted(where: { $0 > 3 })
+    ///
+    ///       // false, false, false, true, true
+    ///       //                      ^
+    ///       // therefore idx == 3
+    ///
+    /// - Parameter predicate: A closure that takes an element as its argument
+    ///   and returns a Boolean value that indicates whether the passed element
+    ///   represents a match.
+    /// - Returns: The index of the first element for which `predicate` returns
+    ///   `true`. If no elements in the collection satisfy the given predicate,
+    ///   returns `nil`.
+    ///
+    /// - Complexity: O(log(*n*)), where *n* is the length of the collection.
+    @inlinable
+    func firstIndexAssumingSorted(where predicate: (Self.Element) throws -> Bool) rethrows -> Int? {
+        // Predicate should divide a collection to two pars of vaues
+        // "bad" values for which predicate returns `false``
+        // "good" values for which predicate return `true`
+
+        // false false false false false true true true
+        //                               ^
+        // The idea is to get _first_ index which for which predicate returns `true`
+
+        let lastIndex = count
+
+        // The index that represetns where bad values starts.
+        var badIndex = -1
+
+        // The index that represetns where good values starts
+        var goodIndex = lastIndex
+        var midIndex = (badIndex + goodIndex) / 2
+
+        while badIndex + 1 < goodIndex {
+            if try predicate(self[midIndex]) {
+                goodIndex = midIndex
+            } else {
+                badIndex = midIndex
+            }
+            midIndex = (badIndex + goodIndex) / 2
+        }
+
+        // Corner case, we' re out of bound, no good items in array
+        if midIndex == lastIndex {
+            return nil
+        }
+        return goodIndex
+    }
+}
diff --git a/Source/SwiftLintFramework/Extensions/SyntaxMap+SwiftLint.swift b/Source/SwiftLintFramework/Extensions/SyntaxMap+SwiftLint.swift
index 345773199b..4f39409443 100644
--- a/Source/SwiftLintFramework/Extensions/SyntaxMap+SwiftLint.swift
+++ b/Source/SwiftLintFramework/Extensions/SyntaxMap+SwiftLint.swift
@@ -11,59 +11,23 @@ extension SyntaxMap {
                 .intersects(byteRange)
         }
 
-        guard let startIndex = firstIntersectingTokenIndex(inByteRange: byteRange) else {
-            return []
+        func intersectsOrAfter(_ token: SyntaxToken) -> Bool {
+            return token.offset + token.length > byteRange.location
         }
 
-        func isAfterByteRange(_ token: SyntaxToken) -> Bool {
-            return token.offset < byteRange.upperBound
+        guard let startIndex = tokens.firstIndexAssumingSorted(where: intersectsOrAfter) else {
+            return []
         }
 
         let tokensAfterFirstIntersection = tokens
             .lazy
             .suffix(from: startIndex)
-            .prefix(while: isAfterByteRange)
+            .prefix(while: { $0.offset < byteRange.upperBound })
             .filter(intersect)
 
         return Array(tokensAfterFirstIntersection)
     }
 
-    // Index of first token which intersects byterange
-    // Using binary search
-    func firstIntersectingTokenIndex(inByteRange byteRange: NSRange) -> Int? {
-        let lastIndex = tokens.count
-
-        // The idx, which definitely beyound byteOffset
-        var bad = -1
-
-        // The index which is definitely after byteOffset
-        var good = lastIndex
-        var mid = (bad + good) / 2
-
-        // 0 0 0 0 0 1 1 1 1 1
-        //           ^
-        // The idea is to get _first_ token index which intesects the byteRange
-        func intersectsOrAfter(at index: Int) -> Bool {
-            let token = tokens[index]
-            return token.offset + token.length > byteRange.location
-        }
-
-        while bad + 1 < good {
-            if intersectsOrAfter(at: mid) {
-                good = mid
-            } else {
-                bad = mid
-            }
-            mid = (bad + good) / 2
-        }
-
-        // Corner case, we' re out of bound, no good items in array
-        if mid == lastIndex {
-            return nil
-        }
-        return good
-    }
-
     internal func kinds(inByteRange byteRange: NSRange) -> [SyntaxKind] {
         return tokens(inByteRange: byteRange).kinds
     }