src/dict: abstract out deconjugators from dictionary code

Create a new class called QueryGenerator that defines a class that can
generate queries from a string of text. ExactQueryGenerator implements
this for searching exact text, and MeCabQueryGenerator implements this
for deconjuating text with MeCab. This makes it so these two methods of
generating queries can share all the same code for filtering duplicates,
generating cloze info, and searching the database. This also makes it
easier to implement new query generators in the future such as the
deconjuator in #210 or the proposed MeCab with UniDic option in #211.

This commit removes all multithreading from searches. I have known for
a while that it provides little to no performance imporvement due to
most time being spent querying a synchronized database. It may also harm
performance on Windows. I don't see any need to add it back, but it can
be if there is a compelling reason to. Queries seem plenty fast with
this change.

src/dict/CMakeLists.txt

@@ -1,3 +1,47 @@
+add_library(searchquery INTERFACE searchquery.h)
+target_compile_features(searchquery INTERFACE cxx_std_17)
+target_compile_options(searchquery INTERFACE ${MEMENTO_COMPILER_FLAGS})
+target_include_directories(searchquery INTERFACE ${MEMENTO_INCLUDE_DIRS})
+target_link_libraries(searchquery INTERFACE Qt6::Core)
+
+add_library(querygenerator INTERFACE querygenerator.h)
+target_compile_features(querygenerator INTERFACE cxx_std_17)
+target_compile_options(querygenerator INTERFACE ${MEMENTO_COMPILER_FLAGS})
+target_include_directories(querygenerator INTERFACE ${MEMENTO_INCLUDE_DIRS})
+target_link_libraries(
+    querygenerator
+    INTERFACE Qt6::Core
+    INTERFACE searchquery
+)
+
+add_library(
+    exactquerygenerator STATIC
+    exactquerygenerator.cpp
+    exactquerygenerator.h
+)
+target_compile_features(exactquerygenerator PRIVATE cxx_std_17)
+target_compile_options(exactquerygenerator PRIVATE ${MEMENTO_COMPILER_FLAGS})
+target_include_directories(exactquerygenerator PRIVATE ${MEMENTO_INCLUDE_DIRS})
+target_link_libraries(
+    exactquerygenerator
+    PUBLIC querygenerator
+)
+
+add_library(
+    mecabquerygenerator STATIC
+    mecabquerygenerator.cpp
+    mecabquerygenerator.h
+)
+target_compile_features(mecabquerygenerator PRIVATE cxx_std_17)
+target_compile_options(mecabquerygenerator PRIVATE ${MEMENTO_COMPILER_FLAGS})
+target_include_directories(mecabquerygenerator PRIVATE ${MEMENTO_INCLUDE_DIRS})
+target_link_libraries(
+    mecabquerygenerator
+    PRIVATE utils
+    PUBLIC MeCab::MeCab
+    PUBLIC querygenerator
+)
+
 add_library(
     yomidbbuilder STATIC
     yomidbbuilder.c
@@ -34,8 +78,10 @@ target_compile_options(dictionary_db PRIVATE ${MEMENTO_COMPILER_FLAGS})
 target_include_directories(dictionary_db PRIVATE ${MEMENTO_INCLUDE_DIRS})
 target_link_libraries(
     dictionary_db
-    PRIVATE MeCab::MeCab
+    PRIVATE exactquerygenerator
+    PRIVATE mecabquerygenerator
     PRIVATE Qt6::Widgets
+    PRIVATE querygenerator
     PRIVATE SQLite::SQLite3
     PRIVATE yomidbbuilder
     PUBLIC Qt6::Core

src/dict/databasemanager.cpp

@@ -221,7 +221,7 @@ int DatabaseManager::disableDictionaries(const QStringList &dicts)
 
 #define QUERY   "SELECT title FROM directory;"
 
-QStringList DatabaseManager::getDictionaries()
+QStringList DatabaseManager::getDictionaries() const
 {
     m_dbLock.lockForRead();
 
@@ -249,7 +249,7 @@ QStringList DatabaseManager::getDictionaries()
 
 #define QUERY   "SELECT dic_id FROM dict_disabled;"
 
-QStringList DatabaseManager::getDisabledDictionaries()
+QStringList DatabaseManager::getDisabledDictionaries() const
 {
     m_dbLock.lockForRead();
 
@@ -302,7 +302,7 @@ QStringList DatabaseManager::getDisabledDictionaries()
 #define COLUMN_EXPRESSION       0
 #define COLUMN_READING          1
 
-QString DatabaseManager::queryTerms(const QString &query, QList<SharedTerm> &terms)
+QString DatabaseManager::queryTerms(const QString &query, QList<SharedTerm> &terms) const
 {
     if (m_db == nullptr)
     {
@@ -439,7 +439,7 @@ QString DatabaseManager::queryTerms(const QString &query, QList<SharedTerm> &ter
 #define TAG_NAME_CODE       "code"
 #define TAG_NAME_INDEX      "index"
 
-QString DatabaseManager::queryKanji(const QString &query, Kanji &kanji)
+QString DatabaseManager::queryKanji(const QString &query, Kanji &kanji) const
 {
     if (m_db == nullptr)
     {
@@ -497,29 +497,31 @@ QString DatabaseManager::queryKanji(const QString &query, Kanji &kanji)
              it != map.constKeyValueEnd();
              ++it)
         {
-            const Tag *tag = &m_tagCache[id][it->first];
+            Tag tag = m_tagCache[id][it->first];
             QList<QPair<Tag, QString>> *list = nullptr;
-            if (tag->category == TAG_NAME_INDEX)
+            if (tag.category == TAG_NAME_INDEX)
             {
                 list = &def.index;
             }
-            else if (tag->category == TAG_NAME_STATS)
+            else if (tag.category == TAG_NAME_STATS)
             {
                 list = &def.stats;
             }
-            else if (tag->category == TAG_NAME_CLAS)
+            else if (tag.category == TAG_NAME_CLAS)
             {
                 list = &def.clas;
             }
-            else if (tag->category == TAG_NAME_CODE)
+            else if (tag.category == TAG_NAME_CODE)
             {
                 list = &def.code;
             }
             else
             {
                 continue;
             }
-            list->append(QPair<Tag, QString>(*tag, it->second.toString()));
+            list->append(
+                QPair<Tag, QString>(std::move(tag), it->second.toString())
+            );
         }
 
         kanji.definitions.append(def);

src/dict/databasemanager.h

@@ -78,13 +78,13 @@ class DatabaseManager
      * Gets a list of dictionary names in the database in arbitrary order.
      * @return A list of dictionary names.
      */
-    QStringList getDictionaries();
+    QStringList getDictionaries() const;
 
     /**
      * Gets the list of disabled dictionaries.
      * @return The names of all disabled dictionaries.
      */
-    QStringList getDisabledDictionaries();
+    QStringList getDisabledDictionaries() const;
 
     /**
      * Searches for terms that exactly match the query. Does automatic
@@ -93,15 +93,15 @@ class DatabaseManager
      * @param[out] terms A list of matching terms. Belongs to the caller.
      * @return Empty string on success, error string on error.
      */
-    QString queryTerms(const QString &query, QList<SharedTerm> &terms);
+    QString queryTerms(const QString &query, QList<SharedTerm> &terms) const;
 
     /**
      * Searches for kanji that exactly match the query.
      * @param      query The kanji to look for. Should be a single character.
      * @param[out] kanji The Kanji struct to populate.
      * @return Empty string on success, error string on error.
      */
-    QString queryKanji(const QString &query, Kanji &kanji);
+    QString queryKanji(const QString &query, Kanji &kanji) const;
 
 private:
     /**
@@ -203,7 +203,7 @@ class DatabaseManager
     sqlite3 *m_db;
 
     /* Locks the database for reading and writing. */
-    QReadWriteLock m_dbLock;
+    mutable QReadWriteLock m_dbLock;
 
     /* Saved path to the database. */
     const QByteArray m_dbpath;