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//
// RandomBySlot.cs
//
// Authors:
// Elena Grassi <grassi.e@gmail.com>
// Alexander Kojevnikov <alexander@kojevnikov.com>
// Gabriel Burt <gburt@novell.com>
//
// Copyright (C) 2008 Elena Grassi
// Copyright (C) 2009 Alexander Kojevnikov
// Copyright (C) 2009 Novell, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
using System;
using System.Collections.Generic;
using System.Linq;
using Hyena;
using Hyena.Data;
using Hyena.Data.Sqlite;
using Banshee.ServiceStack;
using Banshee.PlaybackController;
namespace Banshee.Collection.Database
{
public abstract class RandomBySlot : RandomBy
{
private static Random random = new Random ();
private HyenaSqliteCommand query;
protected int slot;
public RandomBySlot (string id) : base (id)
{
}
protected override void OnModelAndCacheUpdated ()
{
query = null;
}
public override void Reset ()
{
slot = -1;
}
public override bool IsReady { get { return slot != -1; } }
public override bool Next (DateTime after)
{
Reset ();
// counts[x] = number of tracks in slot x.
int[] counts = new int[Slots];
int default_slot = (Slots - 1) / 2;
// Get the distribution for tracks that haven't been played since stamp.
var reader = Shuffler == Shuffler.Playback
? ServiceManager.DbConnection.Query (SlotQuery, after, after)
: ServiceManager.DbConnection.Query (SlotQuery, after);
using (reader) {
while (reader.Read ()) {
int s = Convert.ToInt32 (reader[0]);
int count = Convert.ToInt32 (reader[1]);
if (s < 0 || s >= Slots) {
s = default_slot;
}
counts[s] += count;
}
}
if (counts.Sum () == 0) {
slot = -1;
return false;
}
// We will use powers of phi as weights. Such weights result in songs rated R played as often as songs
// rated R-1 and R-2 combined. The exponent is adjusted to the number of slots when it's different from 5.
const double phi = 1.618033989;
// If you change the weights make sure ALL of them are strictly positive.
var weights = Enumerable.Range (0, Slots).Select (i => Math.Pow (phi, i * 5 / (double) Slots)).ToArray ();
// Apply weights to the counts.
var weighted_counts = counts.Select ((c, i) => c * weights[i]);
// Normalise the counts.
var weighted_total = weighted_counts.Sum ();
weighted_counts = weighted_counts.Select (c => c / weighted_total);
// Now that we have our counts, get the slot a weighted random track belongs to.
double random_value = random.NextDouble ();
int current_slot = -1;
foreach (var weighted_count in weighted_counts) {
current_slot++;
random_value -= weighted_count;
if (random_value <= 0.0) {
break;
}
}
slot = current_slot;
return IsReady;
}
private HyenaSqliteCommand SlotQuery {
get {
if (query == null) {
query = new HyenaSqliteCommand (String.Format (SlotQuerySql,
Model.JoinFragment,
Model.CachesJoinTableEntries
? String.Format ("CoreCache.ItemID = {0}.{1} AND", Model.JoinTable, Model.JoinPrimaryKey)
: "CoreCache.ItemId = CoreTracks.TrackID AND",
Model.CacheId,
Model.ConditionFragment
));
}
return query;
}
}
private string SlotQuerySql {
get {
return Shuffler == Shuffler.Playback ? PlaybackSlotQuerySql : ShufflerSlotQuerySql;
}
}
protected abstract int Slots { get; }
protected abstract string PlaybackSlotQuerySql { get; }
protected abstract string ShufflerSlotQuerySql { get; }
}
}
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