using BlueLaminate.EFCore.Data;
using Microsoft.EntityFrameworkCore;

namespace BlueLaminate.Core.CsMoney;

/// <summary>One marketplace's current presence for a skin or a physical item.</summary>
/// <param name="Marketplace">"csfloat", "csmoney", …</param>
/// <param name="ActiveCount">Active listings on this market.</param>
/// <param name="MinPrice">Cheapest active listing (the comparable price).</param>
/// <param name="MaxPrice">Dearest active listing.</param>
/// <param name="LastSeenAt">When this market was last observed to have it.</param>
public sealed record MarketPresence(
    string Marketplace, int ActiveCount, decimal MinPrice, decimal MaxPrice, DateTimeOffset LastSeenAt);

/// <summary>
/// Answers "where is this listed?" over the cross-market <c>market_listings</c> view.
/// Per physical item (<see cref="ForInstanceAsync"/>) for the exact-copy / arbitrage /
/// dupe view, or per catalogue skin (<see cref="ForSkinAsync"/>) for "which markets
/// carry this skin, and cheapest where".
/// </summary>
public sealed class MarketPresenceService
{
    private const string Active = "Active";

    private readonly SkinTrackerDbContext _db;

    public MarketPresenceService(SkinTrackerDbContext db) => _db = db;

    /// <summary>Markets currently listing this exact physical copy.</summary>
    public Task<List<MarketPresence>> ForInstanceAsync(int skinInstanceId, CancellationToken ct = default) =>
        _db.MarketListings
            .Where(m => m.SkinInstanceId == skinInstanceId && m.Status == Active)
            .GroupBy(m => m.Marketplace)
            .Select(g => new MarketPresence(
                g.Key, g.Count(), g.Min(x => x.Price), g.Max(x => x.Price), g.Max(x => x.LastSeenAt)))
            .ToListAsync(ct);

    /// <summary>Markets currently listing this skin (any wear), cheapest per market.</summary>
    public Task<List<MarketPresence>> ForSkinAsync(int skinId, CancellationToken ct = default) =>
        _db.MarketListings
            .Where(m => m.SkinId == skinId && m.Status == Active)
            .GroupBy(m => m.Marketplace)
            .Select(g => new MarketPresence(
                g.Key, g.Count(), g.Min(x => x.Price), g.Max(x => x.Price), g.Max(x => x.LastSeenAt)))
            .ToListAsync(ct);
}