using System.Collections.Generic;
using System.Linq;
using Godot;
using Godot.Collections;
using Mr.BrickAdventures.Progression;

namespace Mr.BrickAdventures.scripts.Resources;

/// <summary>
/// The authored list of Levels in campaign order, and the bridge from a <see cref="LevelId"/> back to
/// the Godot scene that implements it.
/// </summary>
/// <remarks>
/// Not a domain port. Nothing in the progression domain resolves a Level to a scene — the domain only
/// needs the ordering, which it takes as a <see cref="Campaign"/>. Scene lookup is wanted solely by
/// the composition root, which is engine-side anyway.
/// </remarks>
[GlobalClass]
public partial class LevelCatalogue : Resource
{
    /// <summary>
    /// Levels in campaign order. A Level absent from this list is not reachable, even if its
    /// <see cref="LevelResource"/> exists.
    /// </summary>
    [Export]
    public Array<LevelResource> Levels { get; set; } = [];

    /// <summary>
    /// The ordering the domain works from. Throws if the authored data is inconsistent — a blank or
    /// duplicated id cannot produce a <see cref="Campaign"/>, so a mistake here fails at boot rather
    /// than corrupting a save later.
    /// </summary>
    public Campaign ToCampaign()
    {
        var ids = new List<LevelId>();

        for (var i = 0; i < Levels.Count; i++)
        {
            var level = Levels[i];
            if (level == null)
                throw new System.InvalidOperationException(
                    $"LevelCatalogue has an empty slot at index {i}.");

            ids.Add(LevelId.Of(level.Id));
        }

        return Campaign.Of(ids);
    }

    public LevelResource Find(LevelId id) =>
        Levels.FirstOrDefault(level => level != null && level.Id == id.Value);

    public PackedScene SceneFor(LevelId id) => Find(id)?.Scene;
}