feat(signatures): splice a signature into a buffer

Both placements over one implementation. above_quote inserts before the
attribution rather than before the first quoted line: the attribution
introduces the quote and belongs with it, and a signature between the two
would read as part of the quoted message.

A buffer with no quote makes above_quote identical to end, so a new
message needs no branch of its own.

Part of item 152.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KEcn3u19xPqv6ggD15PG4c

1 files changed, 62 insertions, 0 deletions

diff --git a/tests/test_signatures.cpp b/tests/test_signatures.cpp
index 2a75067..30085fb 100644
--- a/tests/test_signatures.cpp
+++ b/tests/test_signatures.cpp
@@ -31,6 +31,10 @@ private slots:
     void aMissingDirectoryHasNoNames();
     void textIsTheFileContent();
     void textOfAnUnknownNameIsEmpty();
+    void insertingAtTheEndAppendsAfterADelimiter();
+    void insertingAboveTheQuotePutsItBeforeTheFirstQuotedLine();
+    void insertingAboveTheQuoteWithNoQuoteIsTheSameAsEnd();
+    void insertingNothingLeavesTheBufferAlone();
 
 private:
     /// Writes \p files as name -> content into a fresh temporary directory.
@@ -100,5 +104,63 @@ void TestSignatures::textOfAnUnknownNameIsEmpty()
     QVERIFY(Signatures::text(dir.path(), QStringLiteral("absent")).isEmpty());
 }
 
+void TestSignatures::insertingAtTheEndAppendsAfterADelimiter()
+{
+    const QString buffer = QStringLiteral("Hello.\n");
+
+    const QString result = Signatures::replace(
+        buffer, QStringLiteral("Jane Doe"), {}, Signatures::Position::End);
+
+    QCOMPARE(result, QStringLiteral("Hello.\n\n-- \nJane Doe"));
+}
+
+void TestSignatures::insertingAboveTheQuotePutsItBeforeTheFirstQuotedLine()
+{
+    const QString buffer = QStringLiteral(
+        "My reply.\n"
+        "\n"
+        "On Mon, someone wrote:\n"
+        "> the original\n"
+        "> second line\n");
+
+    const QString result = Signatures::replace(
+        buffer, QStringLiteral("Jane Doe"), {},
+        Signatures::Position::AboveQuote);
+
+    // Before the QUOTED lines, and the attribution stays with the quote it
+    // introduces: it is the line the quote hangs from, not part of the reply.
+    QCOMPARE(result, QStringLiteral(
+        "My reply.\n"
+        "\n"
+        "-- \n"
+        "Jane Doe\n"
+        "\n"
+        "On Mon, someone wrote:\n"
+        "> the original\n"
+        "> second line\n"));
+}
+
+void TestSignatures::insertingAboveTheQuoteWithNoQuoteIsTheSameAsEnd()
+{
+    const QString buffer = QStringLiteral("A new message.\n");
+
+    const QString above = Signatures::replace(
+        buffer, QStringLiteral("Jane Doe"), {},
+        Signatures::Position::AboveQuote);
+    const QString end = Signatures::replace(
+        buffer, QStringLiteral("Jane Doe"), {}, Signatures::Position::End);
+
+    QCOMPARE(above, end);
+}
+
+void TestSignatures::insertingNothingLeavesTheBufferAlone()
+{
+    const QString buffer = QStringLiteral("Hello.\n");
+
+    QCOMPARE(Signatures::replace(buffer, QString(), {},
+                                 Signatures::Position::End),
+             buffer);
+}
+
 QTEST_MAIN(TestSignatures)
 #include "test_signatures.moc"