feat(completion): select candidates per context

tag: and is: share the tag list, since notmuch aliases them. path: offers
each account maildir in both bare and recursive forms, the latter being
what Account::scopedQuery builds and not something a user would guess.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

3 files changed, 209 insertions, 0 deletions

diff --git a/src/querycompleter.cpp b/src/querycompleter.cpp
index 77c62c1..6b4c69a 100644
--- a/src/querycompleter.cpp
+++ b/src/querycompleter.cpp
@@ -18,6 +18,8 @@
 
 #include "querycompleter.h"
 
+#include "config.h"
+
 #include <QCoreApplication>
 
 namespace {
@@ -186,3 +188,83 @@ CompletionContext completionContext(const QString &text, int cursor)
     }
     return ctx;
 }
+
+QueryCompleter::QueryCompleter(QLineEdit *edit, const Config &config,
+                               QObject *parent)
+    : QObject(parent), m_edit(edit), m_config(config)
+{
+}
+
+void QueryCompleter::setTags(const QStringList &tags)
+{
+    m_tags = tags;
+}
+
+QList<CompletionEntry> QueryCompleter::entriesFor(
+    const CompletionContext &context) const
+{
+    if (context.kind == CompletionContext::None)
+        return {};
+
+    if (context.kind == CompletionContext::Prefix)
+        return prefixVocabulary();
+
+    // notmuch treats is:x as a synonym for tag:x, so both take the tag list.
+    if (context.prefix == QStringLiteral("tag")
+        || context.prefix == QStringLiteral("is")) {
+        QList<CompletionEntry> entries;
+        entries.reserve(m_tags.size());
+        for (const QString &tag : m_tags)
+            entries.append({ tag, QString() });
+        return entries;
+    }
+
+    if (context.prefix == QStringLiteral("date")) {
+        QList<CompletionEntry> entries;
+        const QList<CompletionEntry> vocabulary = dateVocabulary();
+        for (const CompletionEntry &entry : vocabulary) {
+            // Entries that are themselves ranges cannot go inside a range.
+            if (!context.allowRangeEntries
+                && entry.value.contains(QStringLiteral("..")))
+                continue;
+            entries.append(entry);
+        }
+        return entries;
+    }
+
+    if (context.prefix == QStringLiteral("mimetype")) {
+        QList<CompletionEntry> entries = mimetypeVocabulary();
+        entries.append(m_config.extraMimetypes());
+        return entries;
+    }
+
+    if (context.prefix == QStringLiteral("path")) {
+        QList<CompletionEntry> entries;
+        const QList<Account> accounts = m_config.accounts();
+        for (const Account &account : accounts) {
+            if (account.maildir.isEmpty())
+                continue;
+            entries.append({ account.maildir,
+                             VocabularyStrings::tr("account directory") });
+            entries.append({ account.maildir + QStringLiteral("/**"),
+                             VocabularyStrings::tr("and everything below it") });
+        }
+        return entries;
+    }
+
+    // from:, to:, folder:, subject:, attachment:, thread:, id: complete no
+    // values. Addresses need an enumerator libnotmuch does not expose;
+    // folder: matches a Maildir folder name that config cannot enumerate, and
+    // the rest are free text.
+    return {};
+}
+
+QStringList QueryCompleter::candidatesFor(const CompletionContext &context) const
+{
+    QStringList values;
+    const QList<CompletionEntry> entries = entriesFor(context);
+    values.reserve(entries.size());
+    for (const CompletionEntry &entry : entries)
+        values.append(entry.value);
+    return values;
+}
diff --git a/src/querycompleter.h b/src/querycompleter.h
index 7c00ce2..e9ffc64 100644
--- a/src/querycompleter.h
+++ b/src/querycompleter.h
@@ -19,10 +19,15 @@
 #pragma once
 
 #include <QList>
+#include <QObject>
 #include <QString>
+#include <QStringList>
 
 #include "completionentry.h"
 
+class Config;
+class QLineEdit;
+
 /// Where the cursor sits in a query, and therefore what should be offered.
 ///
 /// A plain value type produced by a pure function so the parsing rules can be
@@ -72,3 +77,29 @@ QList<CompletionEntry> dateVocabulary();
 
 /// The built-in mimetypes, before the user's extra_mimetypes are appended.
 QList<CompletionEntry> mimetypeVocabulary();
+
+/// Completion for the notmuch query bar.
+///
+/// completionContext() above decides which context the cursor sits in; this
+/// class owns the candidates offered for that context.
+class QueryCompleter : public QObject
+{
+    Q_OBJECT
+public:
+    /// `edit` may be null in tests that exercise candidate selection only.
+    QueryCompleter(QLineEdit *edit, const Config &config,
+                   QObject *parent = nullptr);
+
+    /// Replaces the tag candidates. Called with the worker's allTagsReady.
+    void setTags(const QStringList &tags);
+
+    /// The candidate values for a context, in the order they are offered.
+    QStringList candidatesFor(const CompletionContext &context) const;
+
+private:
+    QList<CompletionEntry> entriesFor(const CompletionContext &context) const;
+
+    QLineEdit *m_edit = nullptr;
+    const Config &m_config;
+    QStringList m_tags;
+};
diff --git a/tests/test_querycompleter.cpp b/tests/test_querycompleter.cpp
index fb14adf..bd1e50f 100644
--- a/tests/test_querycompleter.cpp
+++ b/tests/test_querycompleter.cpp
@@ -17,7 +17,9 @@
  */
 
 #include <QtTest>
+#include <QTemporaryDir>
 
+#include "config.h"
 #include "querycompleter.h"
 
 class TestQueryCompleter : public QObject
@@ -41,8 +43,25 @@ private slots:
     void rangeSuppressesRelativeEntries();
     void prefixVocabularyCoversNotmuchKeywords();
     void dateVocabularySeparatesRelativeEntries();
+    void tagAndIsShareTheTagModel();
+    void pathOffersAccountMaildirsBothForms();
+    void folderOffersNothing();
+    void mimetypeAppendsConfiguredEntries();
+    void rangeContextDropsRelativeDates();
 };
 
+// Copied from tests/test_config.cpp rather than shared, so the two test files
+// stay independent.
+static QString writeIni(const QTemporaryDir &dir, const QString &body)
+{
+    const QString path = dir.filePath(QStringLiteral("qtmaildir.conf"));
+    QFile f(path);
+    f.open(QIODevice::WriteOnly | QIODevice::Text);
+    f.write(body.toUtf8());
+    f.close();
+    return path;
+}
+
 void TestQueryCompleter::emptyTextCompletesPrefix()
 {
     const CompletionContext ctx = completionContext(QString(), 0);
@@ -202,5 +221,82 @@ void TestQueryCompleter::dateVocabularySeparatesRelativeEntries()
     QVERIFY(sawRelative);
 }
 
+void TestQueryCompleter::tagAndIsShareTheTagModel()
+{
+    Config config;
+    QueryCompleter completer(nullptr, config);
+    completer.setTags({ QStringLiteral("inbox"), QStringLiteral("shopping/amazon") });
+
+    const QStringList forTag = completer.candidatesFor(
+        completionContext(QStringLiteral("tag:"), 4));
+    const QStringList forIs = completer.candidatesFor(
+        completionContext(QStringLiteral("is:"), 3));
+
+    QVERIFY(forTag.contains(QStringLiteral("shopping/amazon")));
+    QCOMPARE(forTag, forIs);
+}
+
+void TestQueryCompleter::pathOffersAccountMaildirsBothForms()
+{
+    QTemporaryDir dir;
+    Config config;
+    config.load(writeIni(dir, QStringLiteral(
+        "[account.work]\n"
+        "maildir = work\n"
+        "address = you@example.org\n")));
+
+    QueryCompleter completer(nullptr, config);
+    const QStringList candidates = completer.candidatesFor(
+        completionContext(QStringLiteral("path:"), 5));
+
+    QVERIFY(candidates.contains(QStringLiteral("work")));
+    // The recursive form is what scopedQuery() itself builds and is not
+    // guessable, so it is offered directly.
+    QVERIFY(candidates.contains(QStringLiteral("work/**")));
+}
+
+void TestQueryCompleter::folderOffersNothing()
+{
+    // folder: matches a Maildir folder name, not a path, and its values are
+    // not enumerable from config. Prefix-only, like from: and to:.
+    Config config;
+    QueryCompleter completer(nullptr, config);
+    const QStringList candidates = completer.candidatesFor(
+        completionContext(QStringLiteral("folder:"), 7));
+    QVERIFY(candidates.isEmpty());
+}
+
+void TestQueryCompleter::mimetypeAppendsConfiguredEntries()
+{
+    QTemporaryDir dir;
+    Config config;
+    config.load(writeIni(dir, QStringLiteral(
+        "[completion]\n"
+        "extra_mimetypes = application/epub+zip|EPUB book\n")));
+
+    QueryCompleter completer(nullptr, config);
+    const QStringList candidates = completer.candidatesFor(
+        completionContext(QStringLiteral("mimetype:"), 9));
+
+    QVERIFY(candidates.contains(QStringLiteral("application/epub+zip")));
+    QVERIFY(candidates.contains(QStringLiteral("application/pdf")));
+}
+
+void TestQueryCompleter::rangeContextDropsRelativeDates()
+{
+    Config config;
+    QueryCompleter completer(nullptr, config);
+
+    const QStringList bare = completer.candidatesFor(
+        completionContext(QStringLiteral("date:"), 5));
+    QVERIFY(bare.contains(QStringLiteral("1week..")));
+
+    const QString ranged = QStringLiteral("date:today..");
+    const QStringList inRange = completer.candidatesFor(
+        completionContext(ranged, ranged.size()));
+    QVERIFY(inRange.contains(QStringLiteral("yesterday")));
+    QVERIFY(!inRange.contains(QStringLiteral("1week..")));
+}
+
 QTEST_MAIN(TestQueryCompleter)
 #include "test_querycompleter.moc"