using BlueLaminate.EFCore.Data;
using BlueLaminate.EFCore.Entities;
using BlueLaminate.Scraper.Skins;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;

namespace BlueLaminate.Core.Skins;

/// <summary>
/// Loads the CS2 skin catalogue from the CSGO-API dataset and upserts it. The
/// weapon list and the collections/containers are derived from the skins
/// themselves, so any that are missing are created on the fly and no skin is
/// dropped. Throttled to once a month unless forced, since the catalogue changes
/// slowly.
/// </summary>
public sealed class SkinSyncService
{
    public const string Source = "skins";

    private readonly SkinTrackerDbContext _db;
    private readonly SkinCatalogClient _client;
    private readonly ILogger<SkinSyncService> _logger;

    public SkinSyncService(
        SkinTrackerDbContext db,
        SkinCatalogClient client,
        ILogger<SkinSyncService> logger)
    {
        _db = db;
        _client = client;
        _logger = logger;
    }

    public async Task<SkinSyncResult> SyncAsync(bool force = false, CancellationToken ct = default)
    {
        var now = DateTimeOffset.UtcNow;

        var lastRanAt = await _db.ScrapeRuns
            .Where(r => r.Source == Source)
            .OrderByDescending(r => r.RanAt)
            .Select(r => (DateTimeOffset?)r.RanAt)
            .FirstOrDefaultAsync(ct);

        if (!force && lastRanAt is { } last && last.AddMonths(1) > now)
        {
            _logger.LogInformation(
                "Skipping skin sync; last run was {LastRanAt:u} (throttled to monthly).", last);
            return new SkinSyncResult(true, last, 0, 0, 0, 0, 0);
        }

        _logger.LogInformation("Starting skin sync (force: {Force}).", force);
        var catalog = await _client.FetchAsync(ct);
        _logger.LogInformation("Loaded {Count} skins from the catalogue.", catalog.Count);

        var weapons = await _db.Weapons.ToDictionaryAsync(w => w.Name, ct);
        var collections = await _db.Collections.ToDictionaryAsync(c => c.Slug, ct);
        var existing = await _db.Skins
            .Include(s => s.Collections)
            .ToDictionaryAsync(s => s.Slug, ct);

        var inserted = 0;
        var updated = 0;
        var weaponsCreated = 0;
        var collectionsCreated = 0;

        foreach (var s in catalog)
        {
            var weapon = ResolveWeapon(weapons, s, ref weaponsCreated);
            var sources = ResolveCollections(collections, s, ref collectionsCreated);

            if (existing.TryGetValue(s.Id, out var skin))
            {
                if (Apply(skin, s, weapon, sources))
                {
                    updated++;
                }
            }
            else
            {
                skin = new Skin { Slug = s.Id };
                Apply(skin, s, weapon, sources);
                _db.Skins.Add(skin);
                existing[s.Id] = skin;
                inserted++;
            }
        }

        _db.ScrapeRuns.Add(new ScrapeRun { Source = Source, RanAt = now, ItemCount = catalog.Count });
        await _db.SaveChangesAsync(ct);

        _logger.LogInformation(
            "Skin sync complete: {Loaded} loaded, {Inserted} inserted, {Updated} updated, "
            + "{WeaponsCreated} weapons created, {CollectionsCreated} collections created.",
            catalog.Count, inserted, updated, weaponsCreated, collectionsCreated);

        return new SkinSyncResult(
            false, lastRanAt, catalog.Count, inserted, updated, weaponsCreated, collectionsCreated);
    }

    private Weapon ResolveWeapon(Dictionary<string, Weapon> weapons, CatalogSkin s, ref int created)
    {
        if (weapons.TryGetValue(s.WeaponName, out var weapon))
        {
            // Category/team can be refined as the catalogue grows; keep them current.
            weapon.Type = s.Category;
            weapon.Team = s.Team;
            return weapon;
        }

        weapon = new Weapon { Name = s.WeaponName, Type = s.Category, Team = s.Team };
        _db.Weapons.Add(weapon);
        weapons[s.WeaponName] = weapon;
        created++;
        return weapon;
    }

    private List<Collection> ResolveCollections(
        Dictionary<string, Collection> collections, CatalogSkin s, ref int created)
    {
        var resolved = new List<Collection>(s.Sources.Count);
        foreach (var source in s.Sources)
        {
            if (!collections.TryGetValue(source.Id, out var collection))
            {
                collection = new Collection { Slug = source.Id, Name = source.Name, Type = source.Type };
                _db.Collections.Add(collection);
                collections[source.Id] = collection;
                created++;
            }
            resolved.Add(collection);
        }
        return resolved;
    }

    // Copies catalogue values onto the entity. Returns true if anything changed.
    // The weapon navigation is assigned directly (a newly created weapon has no
    // id yet to compare against, so reference-assigning is the only correct way
    // to wire the FK). The collection links are reconciled against the current set.
    private static bool Apply(Skin skin, CatalogSkin s, Weapon weapon, List<Collection> sources)
    {
        skin.Weapon = weapon;

        var changed = false;

        void Set<T>(Func<T> get, Action<T> set, T value)
        {
            if (!EqualityComparer<T>.Default.Equals(get(), value))
            {
                set(value);
                changed = true;
            }
        }

        Set(() => skin.Name, v => skin.Name = v, s.Name);
        Set<int?>(() => skin.DefIndex, v => skin.DefIndex = v, s.DefIndex);
        Set<int?>(() => skin.PaintIndex, v => skin.PaintIndex = v, s.PaintIndex);
        Set(() => skin.Rarity, v => skin.Rarity = v, s.Rarity);
        Set(() => skin.Description, v => skin.Description = v, s.Description);
        Set(() => skin.ImageUrl, v => skin.ImageUrl = v, s.ImageUrl);
        Set(() => skin.StatTrakAvailable, v => skin.StatTrakAvailable = v, s.StatTrakAvailable);
        Set(() => skin.SouvenirAvailable, v => skin.SouvenirAvailable = v, s.SouvenirAvailable);
        Set<decimal?>(() => skin.FloatMin, v => skin.FloatMin = v, s.FloatMin);
        Set<decimal?>(() => skin.FloatMax, v => skin.FloatMax = v, s.FloatMax);

        if (ReconcileCollections(skin.Collections, sources))
        {
            changed = true;
        }

        return changed;
    }

    // Adds collections the skin newly belongs to and removes ones it no longer
    // does, comparing by slug. Returns true if the set changed.
    private static bool ReconcileCollections(ICollection<Collection> current, List<Collection> desired)
    {
        var changed = false;

        foreach (var collection in desired)
        {
            if (!current.Any(c => c.Slug == collection.Slug))
            {
                current.Add(collection);
                changed = true;
            }
        }

        foreach (var collection in current.Where(c => desired.All(d => d.Slug != c.Slug)).ToList())
        {
            current.Remove(collection);
            changed = true;
        }

        return changed;
    }
}