Add StringMatcher interface

Include two implementations regex and string.

Signed-off-by: Appu Goundan <[email protected]>

sigstore-java/src/main/java/dev/sigstore/strings/RegexSyntaxException.java

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2024 The Sigstore 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.
+ */
+package dev.sigstore.strings;
+
+/** Check exception wrapper around {@link java.util.regex.PatternSyntaxException}. */
+public class RegexSyntaxException extends Exception {
+  public RegexSyntaxException(String message, Throwable cause) {
+    super(message, cause);
+  }
+}

sigstore-java/src/main/java/dev/sigstore/strings/StringMatcher.java

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+/*
+ * Copyright 2024 The Sigstore 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.
+ */
+package dev.sigstore.strings;
+
+import java.util.Objects;
+import java.util.function.Predicate;
+import java.util.regex.Pattern;
+import java.util.regex.PatternSyntaxException;
+
+/**
+ * An interface for allowing direct string matching or regular expressions. Use the static factory
+ * {@link #string(String)} or {@link #regex(String)} to instantiate the appropriate matcher. Custom
+ * implementations should override {@link Object#toString} for better error reporting.
+ */
+public interface StringMatcher extends Predicate<String> {
+
+  /** Create a matcher for string equality. */
+  static StringMatcher string(String string) {
+    Objects.requireNonNull(string, "string matcher cannot be initialized with null string");
+    return new StringMatcher() {
+      @Override
+      public boolean test(String target) {
+        return string.equals(target);
+      }
+
+      @Override
+      public String toString() {
+        return "'String: " + string + "'";
+      }
+    };
+  }
+
+  /**
+   * Create a matcher using regular expressions. Regex matching ignores null values and returns
+   * false instead of erroring.
+   *
+   * @param string the input pattern
+   * @return a regex based instance
+   * @throws RegexSyntaxException if the input pattern is not valid regex. This is a runtime
+   *     exception and probably should be handled
+   */
+  static StringMatcher regex(String string) throws RegexSyntaxException {
+    Objects.requireNonNull(string, "string matcher cannot be initialized with null regex");
+    Pattern pattern;
+    try {
+      pattern = Pattern.compile(string);
+    } catch (PatternSyntaxException ex) {
+      throw new RegexSyntaxException("Could not parse regex: '" + string + "'", ex);
+    }
+    return new StringMatcher() {
+      @Override
+      public boolean test(String target) {
+        if (target == null) {
+          return false;
+        }
+        return pattern.matcher(target).matches();
+      }
+
+      @Override
+      public String toString() {
+        return "'RegEx: " + pattern + "'";
+      }
+    };
+  }
+}

sigstore-java/src/test/java/dev/sigstore/strings/StringMatcherTest.java

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+/*
+ * Copyright 2024 The Sigstore 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.
+ */
+package dev.sigstore.strings;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class StringMatcherTest {
+
+  @Test
+  public void testString() {
+    var testMatcher = StringMatcher.string("testtest");
+    Assertions.assertEquals("'String: testtest'", testMatcher.toString());
+
+    Assertions.assertTrue(testMatcher.test("testtest"));
+    Assertions.assertFalse(testMatcher.test("testtest1"));
+    Assertions.assertFalse(testMatcher.test(""));
+    Assertions.assertFalse(testMatcher.test(null));
+  }
+
+  @Test
+  public void testRegex() throws Exception {
+    var testMatcher = StringMatcher.regex("abc...xyz");
+    Assertions.assertEquals("'RegEx: abc...xyz'", testMatcher.toString());
+
+    Assertions.assertTrue(testMatcher.test("abc888xyz"));
+    Assertions.assertFalse(testMatcher.test("abc888xyzEXTRA"));
+    Assertions.assertFalse(testMatcher.test("abcxyz"));
+    Assertions.assertFalse(testMatcher.test(""));
+    Assertions.assertFalse(testMatcher.test(null));
+  }
+
+  @Test
+  public void testRegex_initFailure() {
+    Assertions.assertThrows(RegexSyntaxException.class, () -> StringMatcher.regex("asdf\\"));
+  }
+}