Move SnippetGenerator to vespajlib

2 files changed, 93 insertions, 0 deletions

diff --git a/vespajlib/src/main/java/com/yahoo/text/SnippetGenerator.java b/vespajlib/src/main/java/com/yahoo/text/SnippetGenerator.java
new file mode 100644
index 00000000000..756fe9b48e4
--- /dev/null
+++ b/vespajlib/src/main/java/com/yahoo/text/SnippetGenerator.java
@@ -0,0 +1,34 @@
+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.text;
+
+/**
+ * Truncate text to a snippet suitable for logging.
+ *
+ * @author hakon
+ */
+public class SnippetGenerator {
+
+    private static final String OMIT_PREFIX = "[...";
+    private static final String OMIT_SUFFIX = " chars omitted]";
+    private static final int ASSUMED_OMIT_TEXT_LENGTH = OMIT_PREFIX.length() + 4 + OMIT_SUFFIX.length();
+
+    /** Returns a snippet of approximate size. */
+    public String makeSnippet(String text, int sizeHint) {
+        if (text.length() <= Math.max(sizeHint, ASSUMED_OMIT_TEXT_LENGTH)) return text;
+
+        int maxSuffixLength = Math.max(0, (sizeHint - ASSUMED_OMIT_TEXT_LENGTH) / 2);
+        int maxPrefixLength = Math.max(0, sizeHint - ASSUMED_OMIT_TEXT_LENGTH - maxSuffixLength);
+        String sizeString = Integer.toString(text.length() - maxPrefixLength - maxSuffixLength);
+
+        // It would be silly to return a snippet when the full text is barely longer.
+        // Note: Say ASSUMED_OMIT_TEXT_LENGTH=23: text will be returned whenever sizeHint<23 and text.length()<28.
+        int snippetLength = maxPrefixLength + OMIT_PREFIX.length() + sizeString.length() + OMIT_SUFFIX.length() + maxSuffixLength;
+        if (text.length() <= 1.05 * snippetLength + 5) return text;
+
+        return text.substring(0, maxPrefixLength) +
+                OMIT_PREFIX +
+                sizeString +
+                OMIT_SUFFIX +
+                text.substring(text.length() - maxSuffixLength);
+    }
+}
diff --git a/vespajlib/src/test/java/com/yahoo/text/SnippetGeneratorTest.java b/vespajlib/src/test/java/com/yahoo/text/SnippetGeneratorTest.java
new file mode 100644
index 00000000000..e8ffdb16978
--- /dev/null
+++ b/vespajlib/src/test/java/com/yahoo/text/SnippetGeneratorTest.java
@@ -0,0 +1,59 @@
+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.text;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * @author hakon
+ */
+public class SnippetGeneratorTest {
+    private final SnippetGenerator generator = new SnippetGenerator();
+
+    private void assertSnippet(String text, int sizeHint, String expectedSnippet) {
+        assertEquals(expectedSnippet, generator.makeSnippet(text, sizeHint));
+    }
+
+    @Test
+    public void prefixSnippetForReallySmallSizeHint() {
+        assertSnippet(
+                "This is a long text that should be snippeted", 0,
+                "[...44 chars omitted]");
+
+        assertSnippet(
+                "This is a long text that should be snippeted", 1,
+                "[...44 chars omitted]");
+    }
+
+    @Test
+    public void snippet() {
+        assertSnippet(
+                "This is a long text that should be snippeted", 23,
+                "[...44 chars omitted]");
+
+        assertSnippet(
+                "This is a long text that should be snippeted", 24,
+                "T[...43 chars omitted]");
+
+        assertSnippet(
+                "This is a long text that should be snippeted", 30,
+                "This[...37 chars omitted]ted");
+
+    }
+
+    @Test
+    public void noShorteningNeeded() {
+        assertSnippet(
+                "This is a long text that should be snippeted", 39,
+                "This is [...28 chars omitted]nippeted");
+
+        assertSnippet(
+                "This is a long text that should be snippeted", 40,
+                "This is a long text that should be snippeted");
+
+        assertSnippet(
+                "This is a long text that should be snippeted", 50,
+                "This is a long text that should be snippeted");
+    }
+}