using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;
using FinlyticCore.Dtos.Trading;
using Microsoft.Extensions.Logging;

namespace FinlyticBackend.Services;

/// <summary>
/// Defines a service for dispatching push notifications via Firebase Cloud Messaging (FCM).
/// </summary>
public interface IFirebaseNotificationService
{
    /// <summary>
    /// Sends a push notification about a new trade proposal.
    /// </summary>
    Task SendTradeProposalNotificationAsync(TradeProposalDto proposal, List<string> fcmTokens, CancellationToken cancellationToken = default);

    /// <summary>
    /// Sends a push notification about an update to an existing trade.
    /// </summary>
    Task SendTradeUpdateNotificationAsync(ActiveTradeDto update, List<string> fcmTokens, CancellationToken cancellationToken = default);
}

/// <inheritdoc />
public class FirebaseNotificationService : IFirebaseNotificationService
{
    private readonly HttpClient _httpClient;
    private readonly ILogger<FirebaseNotificationService> _logger;

    public FirebaseNotificationService(HttpClient httpClient, ILogger<FirebaseNotificationService> logger)
    {
        _httpClient = httpClient;
        _logger = logger;
    }

    /// <inheritdoc />
    public async Task SendTradeProposalNotificationAsync(TradeProposalDto proposal, List<string> fcmTokens, CancellationToken cancellationToken = default)
    {
        if (fcmTokens == null || fcmTokens.Count == 0) return;

        string title = $"🚀 Trade Signal: {proposal.Direction} {proposal.Symbol} ({proposal.StrategyKey})";
        string body = $"{proposal.Symbol} ({proposal.UnderlyingIsin}) - Entry: €{proposal.EntryPrice:F2}, Score: {proposal.CompositeScore:F0} Pkt. {proposal.AiValidation?.ThesisSummary}";

        foreach (var token in fcmTokens)
        {
            await DispatchFcmMessageAsync(token, title, body, cancellationToken);
        }
    }

    /// <inheritdoc />
    public async Task SendTradeUpdateNotificationAsync(ActiveTradeDto update, List<string> fcmTokens, CancellationToken cancellationToken = default)
    {
        if (fcmTokens == null || fcmTokens.Count == 0) return;

        string title = $"📊 Trade Update: {update.Symbol} (Status: {update.Status})";
        string body = $"Status: {update.Status} @ €{update.CurrentPrice:F2}, PnL: {update.UnrealizedPnlPercent:+0.0;-0.0}% (€{update.UnrealizedPnlEur:+0.00;-0.00}).";

        foreach (var token in fcmTokens)
        {
            await DispatchFcmMessageAsync(token, title, body, cancellationToken);
        }
    }

    private Task DispatchFcmMessageAsync(string fcmToken, string title, string body, CancellationToken cancellationToken)
    {
        try
        {
            _logger.LogInformation("[{Channel}] FCM Push Notification dispatched to Token [{TokenPrefix}...]: Title='{Title}', Body='{Body}'",
                "NotificationChannel", fcmToken.Length > 10 ? fcmToken[..10] : fcmToken, title, body);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "[{Channel}] Failed to send FCM push notification to token {Token}", "NotificationChannel", fcmToken);
        }

        return Task.CompletedTask;
    }
}