tint/utils: Add Levenshtein Distance() function

Will be used to make a suggestion when enums fail to parse.

Bug: tint:1629
Change-Id: Ia2754f86641f752539fa541ddb6b90b4e200f07c
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/105320
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>

src/tint/BUILD.gn

@@ -577,6 +577,7 @@ libtint_source_set("libtint_core_all_src") {
     "utils/map.h",
     "utils/math.h",
     "utils/scoped_assignment.h",
+    "utils/string.cc",
     "utils/string.h",
     "utils/unique_allocator.h",
     "utils/unique_vector.h",

src/tint/CMakeLists.txt

@@ -486,6 +486,7 @@ set(TINT_LIB_SRCS
   utils/map.h
   utils/math.h
   utils/scoped_assignment.h
+  utils/string.cc
   utils/string.h
   utils/unique_allocator.h
   utils/unique_vector.h

src/tint/utils/string.cc

@@ -0,0 +1,51 @@
+// Copyright 2022 The Tint Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <algorithm>
+
+#include "src/tint/utils/string.h"
+#include "src/tint/utils/vector.h"
+
+namespace tint::utils {
+
+size_t Distance(const std::string& str_a, const std::string& str_b) {
+    const auto len_a = str_a.size();
+    const auto len_b = str_b.size();
+
+    Vector<size_t, 64> mat;
+    mat.Reserve((len_a + 1) * (len_b + 1));
+
+    auto at = [&](size_t a, size_t b) -> size_t& { return mat[a + b * (len_a + 1)]; };
+
+    at(0, 0) = 0;
+    for (size_t a = 1; a <= len_a; a++) {
+        at(a, 0) = a;
+    }
+    for (size_t b = 1; b <= len_b; b++) {
+        at(0, b) = b;
+    }
+    for (size_t b = 1; b <= len_b; b++) {
+        for (size_t a = 1; a <= len_a; a++) {
+            bool eq = str_a[a - 1] == str_b[b - 1];
+            at(a, b) = std::min({
+                at(a - 1, b) + 1,
+                at(a, b - 1) + 1,
+                at(a - 1, b - 1) + (eq ? 0 : 1),
+            });
+        }
+    }
+    return at(len_a, len_b);
+}
+
+}  // namespace tint::utils

src/tint/utils/string.h

@@ -44,6 +44,11 @@ std::string ToString(const T& value) {
     return s.str();
 }
 
+/// @param a the first string
+/// @param b the second string
+/// @returns the Levenshtein distance between @p a and @p b
+size_t Distance(const std::string& a, const std::string& b);
+
 }  // namespace tint::utils
 
 #endif  // SRC_TINT_UTILS_STRING_H_

src/tint/utils/string_test.cc

@@ -20,21 +20,33 @@ namespace tint::utils {
 namespace {
 
 TEST(StringTest, ReplaceAll) {
-    ASSERT_EQ("xybbcc", ReplaceAll("aabbcc", "aa", "xy"));
-    ASSERT_EQ("aaxycc", ReplaceAll("aabbcc", "bb", "xy"));
-    ASSERT_EQ("aabbxy", ReplaceAll("aabbcc", "cc", "xy"));
-    ASSERT_EQ("xyxybbcc", ReplaceAll("aabbcc", "a", "xy"));
-    ASSERT_EQ("aaxyxycc", ReplaceAll("aabbcc", "b", "xy"));
-    ASSERT_EQ("aabbxyxy", ReplaceAll("aabbcc", "c", "xy"));
+    EXPECT_EQ("xybbcc", ReplaceAll("aabbcc", "aa", "xy"));
+    EXPECT_EQ("aaxycc", ReplaceAll("aabbcc", "bb", "xy"));
+    EXPECT_EQ("aabbxy", ReplaceAll("aabbcc", "cc", "xy"));
+    EXPECT_EQ("xyxybbcc", ReplaceAll("aabbcc", "a", "xy"));
+    EXPECT_EQ("aaxyxycc", ReplaceAll("aabbcc", "b", "xy"));
+    EXPECT_EQ("aabbxyxy", ReplaceAll("aabbcc", "c", "xy"));
     // Replacement string includes the searched-for string.
     // This proves that the algorithm needs to advance 'pos'
     // past the replacement.
-    ASSERT_EQ("aabxybbxybcc", ReplaceAll("aabbcc", "b", "bxyb"));
+    EXPECT_EQ("aabxybbxybcc", ReplaceAll("aabbcc", "b", "bxyb"));
 }
 
 TEST(StringTest, ToString) {
-    ASSERT_EQ("123", ToString(123));
-    ASSERT_EQ("hello", ToString("hello"));
+    EXPECT_EQ("123", ToString(123));
+    EXPECT_EQ("hello", ToString("hello"));
+}
+
+TEST(StringTest, Distance) {
+    EXPECT_EQ(Distance("hello world", "hello world"), 0u);
+    EXPECT_EQ(Distance("hello world", "helloworld"), 1u);
+    EXPECT_EQ(Distance("helloworld", "hello world"), 1u);
+    EXPECT_EQ(Distance("hello world", "hello  world"), 1u);
+    EXPECT_EQ(Distance("hello  world", "hello world"), 1u);
+    EXPECT_EQ(Distance("Hello World", "hello world"), 2u);
+    EXPECT_EQ(Distance("hello world", "Hello World"), 2u);
+    EXPECT_EQ(Distance("Hello world", ""), 11u);
+    EXPECT_EQ(Distance("", "Hello world"), 11u);
 }
 
 }  // namespace