From 86ae2ae3953f72a8d96c7359b7bf9fd2614b2cad Mon Sep 17 00:00:00 2001
From: Harry <harry@h313.info>
Date: Fri, 25 Aug 2017 16:08:49 -0400
Subject: [PATCH] Improved shuffle (#1412)

---
 AUTHORS.md                              |  1 +
 apps/openmw/mwsound/soundmanagerimp.cpp | 25 +++++++++++++++++--------
 apps/openmw/mwsound/soundmanagerimp.hpp |  2 ++
 3 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/AUTHORS.md b/AUTHORS.md
index c48647f4e..bb773c4ef 100644
--- a/AUTHORS.md
+++ b/AUTHORS.md
@@ -60,6 +60,7 @@ Programmers
     Gašper Sedej
     gugus/gus
     Hallfaer Tuilinn
+    Haoda Wang (h313)
     hristoast
     Internecine
     Jacob Essex (Yacoby)    
diff --git a/apps/openmw/mwsound/soundmanagerimp.cpp b/apps/openmw/mwsound/soundmanagerimp.cpp
index c6f663059..811797369 100644
--- a/apps/openmw/mwsound/soundmanagerimp.cpp
+++ b/apps/openmw/mwsound/soundmanagerimp.cpp
@@ -3,6 +3,7 @@
 #include <iostream>
 #include <algorithm>
 #include <map>
+#include <numeric>
 
 #include <osg/Matrixf>
 
@@ -271,7 +272,6 @@ namespace MWSound
         return sound;
     }
 
-
     // Gets the combined volume settings for the given sound type
     float SoundManager::volumeFromType(PlayType type) const
     {
@@ -298,7 +298,6 @@ namespace MWSound
         return volume;
     }
 
-
     void SoundManager::stopMusic()
     {
         if(mMusic)
@@ -349,6 +348,7 @@ namespace MWSound
     void SoundManager::startRandomTitle()
     {
         std::vector<std::string> filelist;
+        auto &tracklist = mMusicToPlay[mCurrentPlaylist];
         if (mMusicFiles.find(mCurrentPlaylist) == mMusicFiles.end())
         {
             const std::map<std::string, VFS::File*>& index = mVFS->getIndex();
@@ -367,7 +367,6 @@ namespace MWSound
             }
 
             mMusicFiles[mCurrentPlaylist] = filelist;
-
         }
         else
             filelist = mMusicFiles[mCurrentPlaylist];
@@ -375,15 +374,25 @@ namespace MWSound
         if(filelist.empty())
             return;
 
-        int i = Misc::Rng::rollDice(filelist.size());
+        // Do a Fisher-Yates shuffle
 
-        // Don't play the same music track twice in a row
-        if (filelist[i] == mLastPlayedMusic)
+        // Repopulate if playlist is empty
+        if(tracklist.empty())
         {
-            i = (i+1) % filelist.size();
+            tracklist.resize(filelist.size());
+            std::iota(tracklist.begin(), tracklist.end(), 0);
         }
 
-        advanceMusic(filelist[i]);
+        int i = Misc::Rng::rollDice(tracklist.size());
+
+        // Reshuffle if last played music is the same after a repopulation
+        if(filelist[tracklist[i]] == mLastPlayedMusic)
+            i = (i+1) % tracklist.size();
+
+        // Remove music from list after advancing music
+        advanceMusic(filelist[tracklist[i]]);
+        tracklist[i] = tracklist.back();
+        tracklist.pop_back();
     }
 
     bool SoundManager::isMusicPlaying()
diff --git a/apps/openmw/mwsound/soundmanagerimp.hpp b/apps/openmw/mwsound/soundmanagerimp.hpp
index 5d911d4be..691e52932 100644
--- a/apps/openmw/mwsound/soundmanagerimp.hpp
+++ b/apps/openmw/mwsound/soundmanagerimp.hpp
@@ -6,6 +6,7 @@
 #include <utility>
 #include <deque>
 #include <map>
+#include <unordered_map>
 
 #include <components/settings/settings.hpp>
 
@@ -49,6 +50,7 @@ namespace MWSound
 
         // Caches available music tracks by <playlist name, (sound files) >
         std::map<std::string, std::vector<std::string> > mMusicFiles;
+        std::unordered_map<std::string, std::vector<int>> mMusicToPlay; // A list with music files not yet played
         std::string mLastPlayedMusic; // The music file that was last played
 
         float mMasterVolume;