CatStation/Content.Shared/EntityTable/EntityTableSystem.cs

using System.Diagnostics.CodeAnalysis;
using Content.Shared.EntityTable.EntitySelectors;
using JetBrains.Annotations;
using Robust.Shared.Prototypes;
using Robust.Shared.Random;
using Robust.Shared.Utility;

namespace Content.Shared.EntityTable;

public sealed partial class EntityTableSystem : EntitySystem
{
    [Dependency] private IRobustRandom _random = default!;

    /// <summary>
    /// Iterates once through Entities that EntitySelector in EntityTableProto provides and picks first one.
    /// </summary>
    public EntProtoId? GetFirstOrNull(
        EntityTablePrototype entTableProto,
        IRobustRandom? rand = null,
        EntityTableContext? ctx = null
    )
    {
        return GetSpawns(entTableProto, rand, ctx).FirstOrNull();
    }

    /// <summary>
    /// Iterates once through Entities that EntitySelector provides and picks first one.
    /// </summary>
    public EntProtoId? GetFirstOrNull(
        EntityTableSelector? entTableProto,
        IRobustRandom? rand = null,
        EntityTableContext? ctx = null
    )
    {
        return GetSpawns(entTableProto, rand, ctx).FirstOrNull();
    }

    /// <summary>
    /// Compiles a random list of entity prototypes using constraints.
    /// </summary>
    public IEnumerable<EntProtoId> GetSpawns(EntityTablePrototype entTableProto, IRobustRandom? rand = null, EntityTableContext? ctx = null)
    {
        // convenient
        return GetSpawns(entTableProto.Table, rand, ctx);
    }

    /// <summary>
    /// Compiles a random list of entity prototypes using constraints.
    /// </summary>
    public IEnumerable<EntProtoId> GetSpawns(EntityTableSelector? table, IRobustRandom? rand = null, EntityTableContext? ctx = null)
    {
        if (table == null)
            return new List<EntProtoId>();

        rand ??= _random;
        ctx ??= new EntityTableContext();
        return table.GetSpawns(rand, EntityManager, ProtoMan, ctx);
    }

    /// <summary>
    /// Builds a list of all the spawns in an EntityTable as keys, and their modified weights as values.
    /// </summary>
    public IEnumerable<(EntProtoId spawn, double)> ListSpawns(EntityTablePrototype entTableProto, EntityTableContext? ctx = null)
    {
        return ListSpawns(entTableProto.Table, ctx);
    }

    /// <summary>
    /// Builds a list of all the spawns in an EntityTable as keys, and their modified weights as values.
    /// </summary>
    /// <param name="table">Table we're examining</param>
    /// <param name="ctx">Optional extra context</param>
    public IEnumerable<(EntProtoId spawn, double)> ListSpawns(EntityTableSelector? table, EntityTableContext? ctx = null)
    {
        if (table == null)
            return new List<(EntProtoId spawn, double)>();

        ctx ??= new EntityTableContext();
        return table.ListSpawns(EntityManager, ProtoMan, ctx);
    }

    /// <inheritdoc cref="AverageSpawns(EntityTableSelector?,EntityTableContext?)"/>
    public IEnumerable<(EntProtoId spawn, double)> AverageSpawns(EntityTablePrototype entTableProto, EntityTableContext? ctx = null)
    {
        return AverageSpawns(entTableProto.Table, ctx);
    }

    /// <summary>
    /// Returns the average expected spawns of a specific entity table.
    /// </summary>
    /// <param name="table">The entity table we want the spawns of</param>
    /// <param name="ctx">Optional EntityTableContext</param>
    /// <returns></returns>
    public IEnumerable<(EntProtoId spawn, double)> AverageSpawns(EntityTableSelector? table, EntityTableContext? ctx = null)
    {
        if (table == null)
            return new List<(EntProtoId spawn, double)>();

        ctx ??= new EntityTableContext();
        return table.AverageSpawns(EntityManager, ProtoMan, ctx);
    }
}

/// <summary>
/// Context used by selectors and conditions to evaluate in generic gamestate information.
/// </summary>
public sealed class EntityTableContext
{
    private readonly Dictionary<string, object> _data = new();

    public EntityTableContext()
    {

    }

    public EntityTableContext(Dictionary<string, object> data)
    {
        _data = data;
    }

    /// <summary>
    /// Retrieves an arbitrary piece of data from the context based on a provided key.
    /// </summary>
    /// <param name="key">A string key that corresponds to the value we are searching for. </param>
    /// <param name="value">The value we are trying to extract from the context object</param>
    /// <typeparam name="T">The type of <see cref="value"/> that we are trying to retrieve</typeparam>
    /// <returns>If <see cref="key"/> has a corresponding value of type <see cref="T"/></returns>
    [PublicAPI]
    public bool TryGetData<T>([ForbidLiteral] string key, [NotNullWhen(true)] out T? value)
    {
        value = default;
        if (!_data.TryGetValue(key, out var valueData) || valueData is not T castValueData)
            return false;

        value = castValueData;
        return true;
    }

    /// <summary>
    /// Sets data into context using provided key.
    /// </summary>
    [PublicAPI]
    public void SetData<T>([ForbidLiteral] string key, T data) where T : notnull
    {
        _data[key] = data;
    }

    /// <summary>
    /// Removes data from the context, if the key exists.
    /// </summary>
    [PublicAPI]
    public void RemoveData([ForbidLiteral] string key)
    {
        _data.Remove(key);
    }
}