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>

2 files changed, 113 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;
+};