refactor: introduce the DiffEqualizer interface

This replaces the untyped lambda.

Author: lppedd

src/commonMain/kotlin/io/github/petertrr/diffutils/DiffUtils.kt

@@ -22,6 +22,7 @@ package io.github.petertrr.diffutils
 
 import io.github.petertrr.diffutils.algorithm.DiffAlgorithm
 import io.github.petertrr.diffutils.algorithm.DiffAlgorithmListener
+import io.github.petertrr.diffutils.algorithm.DiffEqualizer
 import io.github.petertrr.diffutils.algorithm.NoopAlgorithmListener
 import io.github.petertrr.diffutils.algorithm.myers.MyersDiff
 import io.github.petertrr.diffutils.patch.Patch
@@ -73,7 +74,7 @@ public fun diff(
 public fun <T> diff(
     source: List<T>,
     target: List<T>,
-    equalizer: ((T, T) -> Boolean),
+    equalizer: DiffEqualizer<T>,
 ): Patch<T> =
     diff(
         source = source,

src/commonMain/kotlin/io/github/petertrr/diffutils/algorithm/DiffEqualizer.kt

@@ -0,0 +1,20 @@
+/*
+ * Copyright 2024 Peter Trifanov.
+ *
+ * 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.
+ */
+package io.github.petertrr.diffutils.algorithm
+
+public fun interface DiffEqualizer<T> {
+    public fun test(one: T, two: T): Boolean
+}

src/commonMain/kotlin/io/github/petertrr/diffutils/algorithm/EqualsDiffEqualizer.kt

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2024 Peter Trifanov.
+ *
+ * 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.
+ */
+package io.github.petertrr.diffutils.algorithm
+
+public class EqualsDiffEqualizer<T> : DiffEqualizer<T> {
+    override fun test(one: T, two: T): Boolean =
+        one == two
+}

src/commonMain/kotlin/io/github/petertrr/diffutils/algorithm/IgnoreWsStringDiffEqualizer.kt

@@ -0,0 +1,25 @@
+/*
+ * Copyright 2024 Peter Trifanov.
+ *
+ * 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.
+ */
+package io.github.petertrr.diffutils.algorithm
+
+public class IgnoreWsStringDiffEqualizer : DiffEqualizer<String> {
+    private companion object {
+        private val ws = Regex("\\s+")
+    }
+
+    override fun test(one: String, two: String): Boolean =
+        ws.replace(one.trim(), " ") == ws.replace(two.trim(), " ")
+}

src/commonMain/kotlin/io/github/petertrr/diffutils/algorithm/myers/MyersDiff.kt

@@ -21,12 +21,14 @@ package io.github.petertrr.diffutils.algorithm.myers
 import io.github.petertrr.diffutils.algorithm.Change
 import io.github.petertrr.diffutils.algorithm.DiffAlgorithm
 import io.github.petertrr.diffutils.algorithm.DiffAlgorithmListener
+import io.github.petertrr.diffutils.algorithm.DiffEqualizer
+import io.github.petertrr.diffutils.algorithm.EqualsDiffEqualizer
 import io.github.petertrr.diffutils.patch.DeltaType
 
 /**
  * A clean-room implementation of Eugene Myers greedy differencing algorithm.
  */
-public class MyersDiff<T>(private val equalizer: (T, T) -> Boolean = { t1, t2 -> t1 == t2 }) : DiffAlgorithm<T> {
+public class MyersDiff<T>(private val equalizer: DiffEqualizer<T> = EqualsDiffEqualizer()) : DiffAlgorithm<T> {
     /**
      * Returns an empty diff if we get an error while procession the difference.
      */
@@ -82,7 +84,7 @@ public class MyersDiff<T>(private val equalizer: (T, T) -> Boolean = { t1, t2 ->
                 var j = i - k
                 var node = PathNode(i, j, snake = false, bootstrap = false, prev = prev)
 
-                while (i < origSize && j < revSize && equalizer.invoke(orig[i], rev[j])) {
+                while (i < origSize && j < revSize && equalizer.test(orig[i], rev[j])) {
                     i++
                     j++
                 }

src/commonMain/kotlin/io/github/petertrr/diffutils/text/DiffRowGenerator.kt

@@ -18,6 +18,9 @@
  */
 package io.github.petertrr.diffutils.text
 
+import io.github.petertrr.diffutils.algorithm.DiffEqualizer
+import io.github.petertrr.diffutils.algorithm.EqualsDiffEqualizer
+import io.github.petertrr.diffutils.algorithm.IgnoreWsStringDiffEqualizer
 import io.github.petertrr.diffutils.diff
 import io.github.petertrr.diffutils.patch.ChangeDelta
 import io.github.petertrr.diffutils.patch.Chunk
@@ -51,7 +54,7 @@ public class DiffRowGenerator(
     /**
      * Provide an equalizer for diff processing.
      */
-    private var equalizer: ((String, String) -> Boolean) = if (ignoreWhiteSpaces) IGNORE_WHITESPACE_EQUALIZER else DEFAULT_EQUALIZER,
+    private var equalizer: DiffEqualizer<String> = if (ignoreWhiteSpaces) IgnoreWsStringDiffEqualizer() else EqualsDiffEqualizer(),
 
     /**
      * Per default each character is separately processed. Setting this parameter to `true`
@@ -410,12 +413,6 @@ public class DiffRowGenerator(
     }
 
     public companion object {
-        internal val DEFAULT_EQUALIZER: (Any?, Any?) -> Boolean = { o1: Any?, o2: Any? -> o1 == o2 }
-        internal val IGNORE_WHITESPACE_EQUALIZER: (String, String) -> Boolean = { original: String, revised: String ->
-            adjustWhitespace(
-                original
-            ) == adjustWhitespace(revised)
-        }
         internal val LINE_NORMALIZER_FOR_HTML: (String) -> String = { normalize(it) }
 
         /**
@@ -439,11 +436,6 @@ public class DiffRowGenerator(
                 SPLIT_BY_WORD_PATTERN
             )
         }
-        internal val WHITESPACE_PATTERN = Regex("\\s+")
-
-        private fun adjustWhitespace(raw: String): String {
-            return WHITESPACE_PATTERN.replace(raw.trim(), " ")
-        }
 
         internal fun splitStringPreserveDelimiter(str: String?, splitPattern: Regex): List<String> {
             val list: MutableList<String> = mutableListOf()