From 5e7e9cac3500805650cc6b52e4e1503f7ec654a8 Mon Sep 17 00:00:00 2001
From: Pierre Lamot <pierre@videolabs.io>
Date: Wed, 23 Mar 2022 17:19:48 +0100
Subject: [PATCH] qt: allow to move or remove range of items from the cache

this would allow to move or update elements in "a priori" before getting the
notification from the database
---
 modules/gui/qt/medialibrary/mlbasemodel.cpp | 21 +++++++++++
 modules/gui/qt/medialibrary/mlbasemodel.hpp |  3 ++
 modules/gui/qt/medialibrary/mllistcache.cpp | 42 +++++++++++++++++++++
 modules/gui/qt/medialibrary/mllistcache.hpp | 13 +++++++
 4 files changed, 79 insertions(+)

diff --git a/modules/gui/qt/medialibrary/mlbasemodel.cpp b/modules/gui/qt/medialibrary/mlbasemodel.cpp
index bb5653dd5e..3380071121 100644
--- a/modules/gui/qt/medialibrary/mlbasemodel.cpp
+++ b/modules/gui/qt/medialibrary/mlbasemodel.cpp
@@ -574,6 +574,27 @@ void MLBaseModel::deleteItemInCache(const MLItemId& mlid)
     m_cache->deleteItem(mlid);
 }
 
+
+void MLBaseModel::moveRangeInCache(int first, int last, int to)
+{
+    if (!m_cache)
+    {
+        emit resetRequested();
+        return;
+    }
+    m_cache->moveRange(first, last, to);
+}
+
+void MLBaseModel::deleteRangeInCache(int first, int last)
+{
+    if (!m_cache)
+    {
+        emit resetRequested();
+        return;
+    }
+    m_cache->deleteRange(first, last);
+}
+
 //-------------------------------------------------------------------------------------------------
 
 MLBaseModel::BaseLoader::BaseLoader(MLItemId parent, QString searchPattern,
diff --git a/modules/gui/qt/medialibrary/mlbasemodel.hpp b/modules/gui/qt/medialibrary/mlbasemodel.hpp
index daf6e697d8..a0dfab94de 100644
--- a/modules/gui/qt/medialibrary/mlbasemodel.hpp
+++ b/modules/gui/qt/medialibrary/mlbasemodel.hpp
@@ -123,6 +123,9 @@ protected:
     //this is only to reflect changes from the ML, it won't alter the database
     void deleteItemInCache(const MLItemId& mlid);
 
+    void moveRangeInCache(int first, int last, int to);
+    void deleteRangeInCache(int first, int last);
+
     virtual void onVlcMlEvent( const MLEvent &event );
 
 
diff --git a/modules/gui/qt/medialibrary/mllistcache.cpp b/modules/gui/qt/medialibrary/mllistcache.cpp
index 7ff6930d9c..4fd48cad79 100644
--- a/modules/gui/qt/medialibrary/mllistcache.cpp
+++ b/modules/gui/qt/medialibrary/mllistcache.cpp
@@ -151,6 +151,48 @@ int MLListCache::deleteItem(const MLItemId& mlid)
     return pos;
 }
 
+void MLListCache::moveRange(int first, int last, int to)
+{
+    assert(first <= last);
+    if (first <= to && to <= last)
+        return;
+
+    emit beginMoveRows(first, last, to);
+    auto it = m_cachedData->list.begin();
+    //build a temporary list with the items in order
+    std::vector<ItemType> tmpList;
+    if (to < first)
+    {
+        std::move(it, it+to, std::back_inserter(tmpList));
+        std::move(it+first, it+(last+1), std::back_inserter(tmpList));
+        std::move(it+to, it+first, std::back_inserter(tmpList));
+        std::move(it+(last+1), m_cachedData->list.end(), std::back_inserter(tmpList));
+    }
+    else //last < to
+    {
+        std::move(it, it+first, std::back_inserter(tmpList));
+        std::move(it+last+1, it+to, std::back_inserter(tmpList));
+        std::move(it+first, it+(last+1), std::back_inserter(tmpList));
+        std::move(it+to, m_cachedData->list.end(), std::back_inserter(tmpList));
+    }
+
+    m_cachedData->list = std::move(tmpList);
+    emit endMoveRows();
+}
+
+void MLListCache::deleteRange(int first, int last)
+{
+    assert(first <= last);
+    emit beginRemoveRows(first, last);
+    auto it = m_cachedData->list.begin();
+    m_cachedData->list.erase(it+first, it+(last+1));
+    size_t delta = m_cachedData->loadedCount - m_cachedData->list.size();
+    m_cachedData->loadedCount -= delta;
+    m_cachedData->totalCount -= delta;
+    emit endRemoveRows();
+    emit localSizeChanged(m_cachedData->totalCount);
+}
+
 ssize_t MLListCache::count() const
 {
     if (!m_cachedData)
diff --git a/modules/gui/qt/medialibrary/mllistcache.hpp b/modules/gui/qt/medialibrary/mllistcache.hpp
index d5f5a55e9a..56b1e61635 100644
--- a/modules/gui/qt/medialibrary/mllistcache.hpp
+++ b/modules/gui/qt/medialibrary/mllistcache.hpp
@@ -155,6 +155,19 @@ public:
      */
     int deleteItem(const MLItemId& mlid);
 
+
+    /**
+     * move items in the cache contained between @a first
+     * and @a last to the index @a to
+     */
+    void moveRange(int first, int last, int to);
+
+    /**
+     * remove items in the cache from the index @a first up to the
+     * index @a last
+     */
+    void deleteRange(int first, int last);
+
     /**
      * Return the number of items or `COUNT_UNINITIALIZED`
      *