using System.Security.Cryptography;
using System.Text;
using Microsoft.EntityFrameworkCore;
using RadicadeServer.Admin;
using RadicadeServer.DB;

namespace RadicadeServer.Auth;








public static class AdminSession
{
	public const string CookieName = "radicade_admin_session";
	public const string StateCookieName = "radicade_oauth_state";
	public const string RedirectCookieName = "radicade_oauth_redirect";


	public static readonly TimeSpan Lifetime = TimeSpan.FromHours(12);

	public static readonly TimeSpan AbsoluteLifetime = TimeSpan.FromDays(7);


	private static readonly TimeSpan RotationGrace = TimeSpan.FromMinutes(2);


	public static async Task<string> CreateAsync(RecDBContext db, long adminUserId)
	{
		var token = NewToken();
		db.AdminSessions.Add(new AdminSessionRecord
		{
			AdminUserId = adminUserId,
			TokenHash = Hash(token),
			CreatedAt = DateTime.UtcNow,
			LastSeenAt = DateTime.UtcNow,
			ExpiresAt = DateTime.UtcNow.Add(Lifetime)
		});
		await db.SaveChangesAsync();
		return token;
	}





	public static async Task<(bool Ok, long UserId)> ValidateAsync(RecDBContext db, string? token)
	{
		if (string.IsNullOrWhiteSpace(token)) return (false, 0);

		var now = DateTime.UtcNow;
		var hash = Hash(token);

		var record = await db.AdminSessions.FirstOrDefaultAsync(s => s.TokenHash == hash);
		if (record == null)
		{

			record = await db.AdminSessions.FirstOrDefaultAsync(s =>
				s.PreviousTokenHash == hash && s.LastSeenAt > now - RotationGrace);
			if (record == null) return (false, 0);
		}

		if (record.RevokedAt.HasValue || record.ExpiresAt <= now)
			return (false, 0);

		var ceiling = record.CreatedAt.Add(AbsoluteLifetime);
		if (now >= ceiling) return (false, 0);

		record.LastSeenAt = now;
		record.ExpiresAt = now.Add(Lifetime) < ceiling ? now.Add(Lifetime) : ceiling;
		await db.SaveChangesAsync();

		return (true, record.AdminUserId);
	}




	private static readonly object RotateLock = new();









	public static (string Token, bool Rotated) TryRotate(RecDBContext db, string? currentToken)
	{
		if (string.IsNullOrWhiteSpace(currentToken)) return ("", false);

		lock (RotateLock)
		{
			var record = db.AdminSessions.FirstOrDefault(s => s.TokenHash == Hash(currentToken));
			if (record == null)
			{



				record = db.AdminSessions.FirstOrDefault(s => s.PreviousTokenHash == Hash(currentToken));
				if (record != null && record.LastSeenAt > DateTime.UtcNow - RotationGrace)
					return (currentToken, false);
				return (currentToken, false);
			}

			var now = DateTime.UtcNow;
			var ceiling = record.CreatedAt.Add(AbsoluteLifetime);
			if (now >= ceiling) return (currentToken, false);

			var next = NewToken();
			record.PreviousTokenHash = record.TokenHash;
			record.TokenHash = Hash(next);
			record.LastSeenAt = now;
			record.ExpiresAt = now.Add(Lifetime) < ceiling ? now.Add(Lifetime) : ceiling;
			db.SaveChanges();
			return (next, true);
		}
	}

	public static async Task RevokeAsync(RecDBContext db, string? token)
	{
		if (string.IsNullOrWhiteSpace(token)) return;

		var record = await db.AdminSessions.FirstOrDefaultAsync(s => s.TokenHash == Hash(token));
		if (record == null) return;

		record.RevokedAt = DateTime.UtcNow;
		await db.SaveChangesAsync();
	}


	public static async Task RevokeAllAsync(RecDBContext db, long adminUserId)
	{
		var sessions = await db.AdminSessions
			.Where(s => s.AdminUserId == adminUserId && !s.RevokedAt.HasValue)
			.ToListAsync();
		foreach (var session in sessions)
			session.RevokedAt = DateTime.UtcNow;
		await db.SaveChangesAsync();
	}


	public static async Task PruneAsync(RecDBContext db)
	{
		var cutoff = DateTime.UtcNow.AddDays(-2);
		var stale = await db.AdminSessions
			.Where(s => s.RevokedAt.HasValue || s.ExpiresAt < cutoff)
			.ToListAsync();
		if (stale.Count == 0) return;
		db.AdminSessions.RemoveRange(stale);
		await db.SaveChangesAsync();
	}

	private static string NewToken() => Convert.ToHexString(RandomNumberGenerator.GetBytes(32));

	private static string Hash(string token) =>
		Convert.ToHexString(SHA256.HashData(Encoding.UTF8.GetBytes(token)));
}