using Microsoft.EntityFrameworkCore;
using SVSim.Database.Enums;
using SVSim.Database.Models;

namespace SVSim.Database.Services;

/// <summary>
/// Wire-shape returned by <see cref="RewardGrantService.Apply"/>. Field names match the
/// <c>reward_list</c> entries used by <c>/pack/open</c> and <c>/basic_puzzle/finish</c>.
/// reward_num is a POST-STATE TOTAL for currencies and a count for collection grants — see
/// <see cref="Models.RewardListEntry"/>... see SVSim.EmulatedEntrypoint.Models.Dtos.RewardListEntry
/// for the on-the-wire DTO and the rationale.
/// </summary>
public sealed record GrantedReward(int RewardType, long RewardId, int RewardNum);

/// <summary>
/// General reward-grant primitive. Switches on <see cref="UserGoodsType"/>, mutates the
/// appropriate viewer collection or <see cref="ViewerCurrency"/> field, and returns the
/// wire-shape entry the caller should embed in its response's reward_list.
///
/// Caller is responsible for <c>SaveChangesAsync</c> — this service only mutates the in-memory
/// graph so a controller can stack several grants in a single transaction.
/// </summary>
public sealed class RewardGrantService
{
    private readonly SVSimDbContext _db;
    public RewardGrantService(SVSimDbContext db) => _db = db;

    public GrantedReward Apply(Viewer viewer, UserGoodsType type, long detailId, int num)
    {
        switch (type)
        {
            case UserGoodsType.Sleeve:
                AddCosmeticIfMissing(viewer.Sleeves, detailId, _db.Sleeves);
                return new GrantedReward((int)type, detailId, 1);

            case UserGoodsType.Emblem:
                AddCosmeticIfMissing(viewer.Emblems, detailId, _db.Emblems);
                return new GrantedReward((int)type, detailId, 1);

            case UserGoodsType.Skin: // LeaderSkin in our schema
                AddCosmeticIfMissing(viewer.LeaderSkins, detailId, _db.LeaderSkins);
                return new GrantedReward((int)type, detailId, 1);

            case UserGoodsType.Degree:
                AddCosmeticIfMissing(viewer.Degrees, detailId, _db.Degrees);
                return new GrantedReward((int)type, detailId, 1);

            case UserGoodsType.MyPageBG:
                AddCosmeticIfMissing(viewer.MyPageBackgrounds, detailId, _db.MyPageBackgrounds);
                return new GrantedReward((int)type, detailId, 1);

            case UserGoodsType.Rupy:
                viewer.Currency.Rupees += (ulong)num;
                return new GrantedReward((int)type, detailId, checked((int)viewer.Currency.Rupees));

            case UserGoodsType.Crystal:
                viewer.Currency.Crystals += (ulong)num;
                return new GrantedReward((int)type, detailId, checked((int)viewer.Currency.Crystals));

            case UserGoodsType.RedEther:
                viewer.Currency.RedEther += (ulong)num;
                return new GrantedReward((int)type, detailId, checked((int)viewer.Currency.RedEther));

            case UserGoodsType.Item:
            {
                var owned = viewer.Items.FirstOrDefault(i => i.Item.Id == (int)detailId);
                if (owned is null)
                {
                    var item = _db.Items.Find((int)detailId)
                               ?? throw new InvalidOperationException($"Item {detailId} not in catalog");
                    viewer.Items.Add(new OwnedItemEntry { Item = item, Count = num, Viewer = viewer });
                    return new GrantedReward((int)type, detailId, num);
                }
                owned.Count += num;
                return new GrantedReward((int)type, detailId, owned.Count);
            }

            case UserGoodsType.Card:
            case UserGoodsType.SpotCard:
            case UserGoodsType.SpotCardOnlyLatestCardPack:
                throw new NotSupportedException(
                    $"{type} rewards are out of Phase 1 scope — extend RewardGrantService when /pack/open or similar needs them.");

            default:
                throw new NotSupportedException($"UserGoodsType {type} not yet handled by RewardGrantService");
        }
    }

    private static void AddCosmeticIfMissing<T>(List<T> collection, long detailId, DbSet<T> catalog) where T : class
    {
        // Cosmetic ownership is binary — if the viewer already owns it, the grant is a no-op
        // (matches client UpdateHaveUserGoodsNum behaviour which just calls .Acquired() each time).
        bool alreadyOwned = collection.Any(e => GetId(e) == detailId);
        if (alreadyOwned) return;

        // Wire reward_detail_id is long, but every cosmetic catalog in this codebase uses
        // BaseEntity<int>; downcast for Find. The checked() throws OverflowException if a
        // future capture ships a real long id rather than silently truncating it.
        var entity = catalog.Find(checked((int)detailId))
                     ?? throw new InvalidOperationException(
                         $"Cosmetic id {detailId} not in catalog for type {typeof(T).Name}");
        collection.Add(entity);
    }

    /// <summary>
    /// Reflectively reads an entity's Id property — works for both <c>BaseEntity&lt;int&gt;</c>
    /// (cosmetics) and <c>BaseEntity&lt;long&gt;</c> (e.g. Viewer/Card) without forcing two
    /// non-generic overloads of <see cref="AddCosmeticIfMissing"/>.
    /// </summary>
    private static long GetId<T>(T e)
    {
        var prop = typeof(T).GetProperty("Id")
                   ?? throw new InvalidOperationException($"Type {typeof(T).Name} missing Id property");
        var val = prop.GetValue(e);
        return val switch { long l => l, int i => i, _ => 0 };
    }
}