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osu-lazer/osu.Game/Beatmaps/DifficultyRecommender.cs

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// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
// See the LICENCE file in the repository root for full licence text.
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#nullable disable
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using System;
using System.Collections.Generic;
using System.Linq;
using JetBrains.Annotations;
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using osu.Framework.Allocation;
using osu.Framework.Bindables;
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using osu.Framework.Graphics;
using osu.Game.Online.API;
using osu.Game.Rulesets;
namespace osu.Game.Beatmaps
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{
/// <summary>
/// A class which will recommend the most suitable difficulty for the local user from a beatmap set.
/// This requires the user to be logged in, as it sources from the user's online profile.
/// </summary>
public class DifficultyRecommender : Component
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{
[Resolved]
private IAPIProvider api { get; set; }
[Resolved]
private Bindable<RulesetInfo> ruleset { get; set; }
private readonly Dictionary<string, double> recommendedDifficultyMapping = new Dictionary<string, double>();
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[BackgroundDependencyLoader]
private void load()
{
api.LocalUser.BindValueChanged(_ => populateValues(), true);
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}
/// <summary>
/// Find the recommended difficulty from a selection of available difficulties for the current local user.
/// </summary>
/// <remarks>
/// This requires the user to be online for now.
/// </remarks>
/// <param name="beatmaps">A collection of beatmaps to select a difficulty from.</param>
/// <returns>The recommended difficulty, or null if a recommendation could not be provided.</returns>
[CanBeNull]
public BeatmapInfo GetRecommendedBeatmap(IEnumerable<BeatmapInfo> beatmaps)
{
foreach (string r in orderedRulesets)
{
if (!recommendedDifficultyMapping.TryGetValue(r, out double recommendation))
continue;
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BeatmapInfo beatmapInfo = beatmaps.Where(b => b.Ruleset.ShortName.Equals(r)).OrderBy(b =>
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{
double difference = b.StarRating - recommendation;
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return difference >= 0 ? difference * 2 : difference * -1; // prefer easier over harder
}).FirstOrDefault();
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if (beatmapInfo != null)
return beatmapInfo;
}
return null;
}
private void populateValues()
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{
if (api.LocalUser.Value.RulesetsStatistics == null)
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return;
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foreach (var kvp in api.LocalUser.Value.RulesetsStatistics)
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{
// algorithm taken from https://github.com/ppy/osu-web/blob/e6e2825516449e3d0f3f5e1852c6bdd3428c3437/app/Models/User.php#L1505
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recommendedDifficultyMapping[kvp.Key] = Math.Pow((double)(kvp.Value.PP ?? 0), 0.4) * 0.195;
}
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}
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/// <returns>
/// Rulesets ordered descending by their respective recommended difficulties.
/// The currently selected ruleset will always be first.
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/// </returns>
private IEnumerable<string> orderedRulesets
{
get
{
if (LoadState < LoadState.Ready || ruleset.Value == null)
return Enumerable.Empty<string>();
return recommendedDifficultyMapping
.OrderByDescending(pair => pair.Value)
.Select(pair => pair.Key)
.Where(r => !r.Equals(ruleset.Value.ShortName))
.Prepend(ruleset.Value.ShortName);
}
}
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}
}