using System;
using Godot;
using Mr.BrickAdventures.Progression;
using Mr.BrickAdventures.Progression.Adapters;
using Mr.BrickAdventures.scripts.Resources;

namespace Mr.BrickAdventures.Autoloads;

/// <summary>
/// Composition root for player progression: builds the stores, loads the Profile, and owns the
/// <see cref="ProgressionService"/>.
/// </summary>
/// <remarks>
/// <para>
/// The only Node in this area. The aggregates are plain objects, so their lifetime is no longer tied
/// to the scene tree — which is why the operations below need no null-guarding of the store itself.
/// </para>
/// <para>
/// Every mutating operation is wrapped so that draining and republishing cannot be forgotten. That is
/// the one risk of the DrainEvents design, and wrapping collapses it to this file.
/// </para>
/// </remarks>
public partial class ProgressionRoot : Node
{
    public static ProgressionRoot Instance { get; private set; }

    /// <summary>
    /// The one slot the game currently uses. Phase B replaces this with a picker over several
    /// Playthroughs; until then a fixed id keeps the file name stable across runs.
    /// </summary>
    public static readonly PlaythroughId SoleSlot =
        PlaythroughId.Of(new Guid("a17e0000-0000-4000-8000-000000000001"));

    [Export] public LevelCatalogue Catalogue { get; set; }

    /// <summary>Lives a new Playthrough starts with. A tuning value, so it is authored here rather than baked into the domain.</summary>
    [Export] public int StartingLives { get; set; } = 3;

    private ProgressionService _service;
    private ProgressionEventRepublisher _republisher;

    /// <summary>Levels in campaign order, as the domain sees them.</summary>
    public Campaign Campaign { get; private set; }

    public override void _Ready()
    {
        Instance = this;

        if (Catalogue == null)
        {
            GD.PushError("ProgressionRoot has no LevelCatalogue assigned; progression is unavailable.");
            return;
        }

        foreach (var problem in Catalogue.Validate())
            GD.PushError($"LevelCatalogue: {problem}");

        Campaign = Catalogue.ToCampaign();

        var directory = ProjectSettings.GlobalizePath("user://");
        var playthroughs = new JsonPlaythroughStore(directory);
        var profiles = new JsonProfileStore(directory);

        _service = new ProgressionService(
            LoadProfile(profiles), playthroughs, profiles,
            Campaign, BuildSkillCatalogue(), Lives.Of(StartingLives));

        _republisher = new ProgressionEventRepublisher(Catalogue, GetTree());
    }

    public override void _ExitTree()
    {
        if (Instance == this) Instance = null;
    }

    /// <summary>
    /// A missing Profile is a first run. A corrupt one is reported loudly and replaced with an empty
    /// Profile so the game still starts — but the file is left alone, so it can still be recovered.
    /// </summary>
    private static Profile LoadProfile(IProfileStore profiles)
    {
        var result = profiles.Load();

        if (result.Outcome == LoadOutcome.Corrupt)
            GD.PushError($"Profile could not be read and has been left untouched: {result.Problem}");

        return result.Outcome == LoadOutcome.Loaded ? result.Value : Profile.Empty();
    }

    /// <summary>
    /// Reads the authored upgrade tables into the domain's view of them. A Skill with no upgrade
    /// entries yields an empty cost list, which the domain reports as not purchasable rather than
    /// throwing on <c>Upgrades[0]</c>.
    /// </summary>
    private static SkillCatalogue BuildSkillCatalogue()
    {
        var available = SkillManager.Instance?.AvailableSkills;
        if (available == null) return SkillCatalogue.Empty();

        var costs = new System.Collections.Generic.Dictionary<SkillId, System.Collections.Generic.IReadOnlyList<Coins>>();

        foreach (var skill in available)
        {
            if (skill == null || string.IsNullOrWhiteSpace(skill.Name)) continue;

            var levels = new System.Collections.Generic.List<Coins>();
            foreach (var upgrade in skill.Upgrades)
                levels.Add(Coins.Of(Mathf.Max(0, upgrade.Cost)));

            costs[SkillId.Of(skill.Name)] = levels;
        }

        return SkillCatalogue.Of(costs);
    }

    #region Operations — each drains and republishes, so callers cannot forget to

    public void StartPlaythrough(PlaythroughId id) => Run(() => _service.StartPlaythrough(id));

    public bool LoadPlaythrough(PlaythroughId id)
    {
        if (_service == null) return false;

        var loaded = _service.LoadPlaythrough(id);
        Publish();
        return loaded;
    }

    public LoadOutcome PeekPlaythrough(PlaythroughId id) =>
        _service?.PeekPlaythrough(id) ?? LoadOutcome.Absent;

    public void RecordStat(StatName stat, int amount = 1) => _service?.RecordStat(stat, amount);

    #endregion

    #region Reads

    public bool IsPlaying => _service?.IsPlaying ?? false;
    public bool CanEnter(LevelId level) => _service?.CanEnter(level) ?? false;
    public LevelId? CurrentLevel => _service?.CurrentLevel;
    public Coins TotalCoins => _service?.TotalCoins ?? Coins.Zero;
    public Lives Lives => _service?.Lives ?? Lives.Of(0);
    public bool IsRunOver => _service?.IsRunOver ?? false;
    public SkillLevel? LevelOf(SkillId skill) => _service?.LevelOf(skill);
    public bool IsOwned(SkillId skill) => _service?.IsOwned(skill) ?? false;
    public bool CanAfford(SkillId skill) => _service?.CanAfford(skill) ?? false;
    public bool HasCleared(LevelId level) => _service?.HasCleared(level) ?? false;

    #endregion

    #region Operations, continued

    public bool EnterLevel(LevelId level)
    {
        if (_service == null) return false;

        var entered = _service.EnterLevel(level);
        Publish();
        return entered;
    }

    public void RecordCoinsFound(Coins amount) => Run(() => _service.RecordCoinsFound(amount));

    public void HandlePlayerDeath() => Run(() => _service.HandlePlayerDeath());

    public void FinishLevel(LevelTime? time) => Run(() => _service.FinishLevel(time));

    public PurchaseOutcome PurchaseSkill(SkillId skill)
    {
        if (_service == null) return PurchaseOutcome.NotPlaying;

        var outcome = _service.PurchaseSkill(skill);
        Publish();
        return outcome;
    }

    /// <summary>Free unlock, as a pickup gives. Returns false if it was already owned.</summary>
    public bool GrantSkill(SkillId skill)
    {
        if (_service == null) return false;

        var granted = _service.GrantSkill(skill);
        Publish();
        return granted;
    }

    /// <summary>Takes a Skill away — for Skills that consume themselves.</summary>
    public bool RevokeSkill(SkillId skill)
    {
        if (_service == null) return false;

        var revoked = _service.RevokeSkill(skill);
        Publish();
        return revoked;
    }

    /// <summary>Discards the current Attempt without charging a life — leaving a Level, not dying.</summary>
    public void AbandonAttempt() => Run(() => _service.AbandonAttempt());

    /// <summary>Console only — see <see cref="ProgressionService.ApplyCheat"/>.</summary>
    public void ApplyCheat(Func<PlaythroughSnapshot, PlaythroughSnapshot> change) =>
        Run(() => _service.ApplyCheat(change));

    /// <summary>Whether there is a resumable Playthrough, for enabling the Continue button.</summary>
    public bool HasSavedPlaythrough =>
        PeekPlaythrough(SoleSlot) == LoadOutcome.Loaded;

    private void Run(System.Action operation)
    {
        if (_service == null) return;

        operation();
        Publish();
    }

    private void Publish() => _republisher?.Publish(_service.DrainEvents());

    #endregion
}