using System.Collections;
using PkmnLib.Static.Utils;

namespace PkmnLib.Dynamic.ScriptHandling;

/// <summary>
/// A script set is a collection of scripts that can be accessed by a key.
/// We can add, remove, and clear scripts from the set.
/// This is generally used for volatile scripts.
/// </summary>
public interface IScriptSet : IEnumerable<ScriptContainer>
{
    /// <summary>
    /// Adds a script to the set. If the script with that name already exists in this set, this
    /// makes that script stack instead. The return value here is that script.
    /// </summary>
    ScriptContainer Add(Script script);

    /// <summary>
    /// Adds a script with a name to the set. If the script with that name already exists in this
    /// set, this makes that script stack instead. The return value here is that script.
    /// </summary>
    ScriptContainer? StackOrAdd(StringKey scriptKey, Func<Script> instantiation);

    /// <summary>
    /// Gets a script from the set using its unique name.
    /// </summary>
    ScriptContainer? Get(StringKey scriptKey);

    /// <summary>
    /// Removes a script from the set using its unique name.
    /// </summary>
    void Remove(StringKey scriptKey);

    /// <summary>
    /// Clears all scripts from the set.
    /// </summary>
    void Clear();

    /// <summary>
    /// Checks if the set has a script with the given name.
    /// </summary>
    bool Contains(StringKey scriptKey);

    /// <summary>
    /// Gets a script from the set at a specific index.
    /// </summary>
    ScriptContainer At(int index);

    /// <summary>
    /// Gets the number of scripts in the set.
    /// </summary>
    int Count { get; }

    /// <summary>
    /// Gets the names of all scripts in the set.
    /// </summary>
    IEnumerable<StringKey> GetScriptNames();
}

/// <inheritdoc cref="IScriptSet"/>
public class ScriptSet : IScriptSet
{
    private readonly List<ScriptContainer> _scripts = [];

    /// <inheritdoc />
    public IEnumerator<ScriptContainer> GetEnumerator() => _scripts.GetEnumerator();

    /// <inheritdoc />
    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();

    /// <inheritdoc />
    public ScriptContainer Add(Script script)
    {
        var existing = _scripts.FirstOrDefault(s => s.Script?.Name == script.Name);
        if (existing != null)
        {
            existing.Script!.Stack();
            return existing;
        }

        script.OnRemoveEvent += s => Remove(s.Name);
        var container = new ScriptContainer(script);
        _scripts.Add(container);
        return container;
    }

    /// <inheritdoc />
    public ScriptContainer? StackOrAdd(StringKey scriptKey, Func<Script?> instantiation)
    {
        var existing = _scripts.FirstOrDefault(s => s.Script?.Name == scriptKey);
        if (existing != null)
        {
            existing.Script!.Stack();
            return existing;
        }

        var script = instantiation();
        if (script is null)
            return null;
        script.OnRemoveEvent += s => Remove(s.Name);
        var container = new ScriptContainer(script);
        _scripts.Add(container);
        return container;
    }

    /// <inheritdoc />
    public ScriptContainer? Get(StringKey scriptKey) => _scripts.FirstOrDefault(s => s.Script?.Name == scriptKey);

    /// <inheritdoc />
    public void Remove(StringKey scriptKey)
    {
        var script = _scripts.FirstOrDefault(s => s.Script?.Name == scriptKey);
        if (script is null)
            return;
        script.Script?.OnRemove();
        _scripts.Remove(script);
    }

    /// <inheritdoc />
    public void Clear()
    {
        foreach (var script in _scripts)
        {
            if (!script.IsEmpty)
            {
                script.Script.OnRemove();
            }
        }
        _scripts.Clear();
    }

    /// <inheritdoc />
    public bool Contains(StringKey scriptKey) => _scripts.Any(s => s.Script?.Name == scriptKey);

    /// <inheritdoc />
    public ScriptContainer At(int index) => _scripts[index];

    /// <inheritdoc />
    public int Count => _scripts.Count;

    /// <inheritdoc />
    public IEnumerable<StringKey> GetScriptNames() =>
        _scripts
            .Select(x => x.Script)
            .WhereNotNull()
            .Select(s => s.Name);
}