using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.RateLimiting;
using Microsoft.EntityFrameworkCore;
using PowderCoating.Core.Entities;
using PowderCoating.Core.Enums;
using PowderCoating.Infrastructure.Data;
using PowderCoating.Shared.Constants;
using Twilio.Security;

namespace PowderCoating.Web.Controllers;

/// <summary>
/// Receives inbound webhooks from Twilio (SMS status / opt-out).
/// AllowAnonymous — Twilio posts from their servers, not authenticated users.
/// Requests are validated using the Twilio Request Validator (HMAC-SHA1).
/// </summary>
[AllowAnonymous]
[ApiController]
[EnableRateLimiting(AppConstants.RateLimitPolicies.Webhook)]
public class WebhooksController : ControllerBase
{
    private readonly ApplicationDbContext _context;
    private readonly IConfiguration _configuration;
    private readonly IWebHostEnvironment _environment;
    private readonly ILogger<WebhooksController> _logger;

    // CTIA-standard opt-out keywords (case-insensitive)
    private static readonly HashSet<string> StopKeywords = new(StringComparer.OrdinalIgnoreCase)
    {
        "STOP", "STOPALL", "UNSUBSCRIBE", "CANCEL", "END", "QUIT"
    };

    // CTIA-standard opt-in keywords
    private static readonly HashSet<string> StartKeywords = new(StringComparer.OrdinalIgnoreCase)
    {
        "START", "YES", "UNSTOP"
    };

    // CTIA-standard help keywords
    private static readonly HashSet<string> HelpKeywords = new(StringComparer.OrdinalIgnoreCase)
    {
        "HELP", "INFO"
    };

    public WebhooksController(
        ApplicationDbContext context,
        IConfiguration configuration,
        IWebHostEnvironment environment,
        ILogger<WebhooksController> logger)
    {
        _context = context;
        _configuration = configuration;
        _environment = environment;
        _logger = logger;
    }

    /// <summary>
    /// Receives inbound SMS messages forwarded by Twilio. Configure this endpoint as the
    /// "A message comes in" webhook URL in the Twilio Console for the outbound SMS number.
    /// Validates the request signature, then routes STOP keywords (opts customer out with
    /// timestamp + DB log + TwiML confirmation), HELP keywords (TwiML help reply + DB log),
    /// and all other messages (silent acknowledgment). Always returns TwiML — Twilio expects a
    /// 200 with valid TwiML; any other response triggers automatic retries.
    /// </summary>
    [HttpPost("Webhooks/TwilioSms")]
    [IgnoreAntiforgeryToken]
    public async Task<IActionResult> TwilioSms([FromForm] TwilioSmsPayload payload)
    {
        if (!ValidateTwilioRequest())
        {
            _logger.LogWarning("Rejected Twilio webhook: invalid signature from {IP}",
                HttpContext.Connection.RemoteIpAddress);
            return Forbid();
        }

        if (string.IsNullOrWhiteSpace(payload.From))
            return TwimlEmpty();

        var body = (payload.Body ?? string.Empty).Trim();
        _logger.LogInformation("Twilio inbound SMS from {From}: {Body}", payload.From, body);

        if (StopKeywords.Contains(body))
            return await HandleStopAsync(payload.From);

        if (StartKeywords.Contains(body))
            return await HandleStartAsync(payload.From);

        if (HelpKeywords.Contains(body))
            return await HandleHelpAsync(payload.From);

        // Unrecognized message — silent acknowledge
        return TwimlEmpty();
    }

    // ── STOP ──────────────────────────────────────────────────────────────────

    /// <summary>
    /// Processes a STOP keyword: opts the customer out, stamps SmsOptedOutAt, logs to
    /// NotificationLog, and returns a TwiML confirmation message.
    /// </summary>
    private async Task<IActionResult> HandleStopAsync(string from)
    {
        var (customer, digits10) = await FindCustomerByPhoneAsync(from);

        if (customer == null)
        {
            _logger.LogWarning("Twilio STOP from {From} — no matching customer found", from);
            // Still send a polite confirmation even if we can't find them
            return TwimlMessage("You have been unsubscribed and will not receive further messages.");
        }

        var companyName = await GetCompanyNameAsync(customer.CompanyId);

        if (customer.NotifyBySms)
        {
            customer.NotifyBySms   = false;
            customer.SmsOptedOutAt = DateTime.UtcNow;
            customer.UpdatedAt     = DateTime.UtcNow;
            await _context.SaveChangesAsync();
            _logger.LogInformation("Customer {CustomerId} opted out of SMS via STOP reply", customer.Id);
        }

        await WriteInboundLogAsync(
            NotificationType.SmsInboundStop,
            customer,
            from,
            "STOP");

        return TwimlMessage(
            $"{companyName}: You have been unsubscribed. No further messages will be sent. " +
            $"Reply START to re-subscribe.");
    }

    // ── START ─────────────────────────────────────────────────────────────────

    /// <summary>
    /// Processes a START keyword: re-enables SMS for the customer, clears SmsOptedOutAt,
    /// logs to NotificationLog, and returns a TwiML confirmation message.
    /// </summary>
    private async Task<IActionResult> HandleStartAsync(string from)
    {
        var (customer, digits10) = await FindCustomerByPhoneAsync(from);

        if (customer == null)
        {
            _logger.LogWarning("Twilio START from {From} — no matching customer found", from);
            return TwimlMessage("You have been re-subscribed and will receive messages again.");
        }

        var companyName = await GetCompanyNameAsync(customer.CompanyId);

        if (!customer.NotifyBySms)
        {
            customer.NotifyBySms   = true;
            customer.SmsOptedOutAt = null;
            customer.UpdatedAt     = DateTime.UtcNow;
            await _context.SaveChangesAsync();
            _logger.LogInformation("Customer {CustomerId} re-subscribed to SMS via START reply", customer.Id);
        }

        await WriteInboundLogAsync(
            NotificationType.SmsInboundStart,
            customer,
            from,
            "START");

        return TwimlMessage(
            $"{companyName}: You have been re-subscribed and will receive messages again. " +
            $"Reply STOP to unsubscribe at any time.");
    }

    // ── HELP ──────────────────────────────────────────────────────────────────

    /// <summary>
    /// Processes a HELP keyword: logs the inbound message and returns a TwiML help response
    /// with the program description and opt-out instructions.
    /// </summary>
    private async Task<IActionResult> HandleHelpAsync(string from)
    {
        var (customer, _) = await FindCustomerByPhoneAsync(from);

        string companyName;
        if (customer != null)
        {
            companyName = await GetCompanyNameAsync(customer.CompanyId);
            await WriteInboundLogAsync(
                NotificationType.SmsInboundHelp,
                customer,
                from,
                "HELP");
        }
        else
        {
            companyName = "Powder Coating Logix";
            _logger.LogWarning("Twilio HELP from {From} — no matching customer found", from);
        }

        return TwimlMessage(
            $"{companyName}: Job status & pickup alerts. Msg & data rates may apply. " +
            $"Reply STOP to unsubscribe. Contact us directly for additional help.");
    }

    // ── Helpers ───────────────────────────────────────────────────────────────

    /// <summary>
    /// Finds a customer by matching the last 10 digits of the inbound phone number against
    /// MobilePhone and Phone fields (handles E.164, formatted, and local number variations).
    /// When the same phone number exists across multiple tenant companies, breaks the tie by
    /// choosing the customer whose company most recently sent them an outbound SMS — it is
    /// nearly impossible for two shops to be texting the same number about a job on the same day.
    /// Falls back to the alphabetically first match if no outbound SMS log exists for any candidate.
    /// </summary>
    private async Task<(Customer? customer, string digits10)> FindCustomerByPhoneAsync(string from)
    {
        var digits10 = from.Length >= 10 ? from[^10..] : from;

        var candidates = await _context.Customers
            .IgnoreQueryFilters()
            .Where(c =>
                !c.IsDeleted && (
                    (c.MobilePhone != null && c.MobilePhone.Replace("-", "").Replace("(", "").Replace(")", "").Replace(" ", "").Replace("+", "").EndsWith(digits10)) ||
                    (c.Phone       != null && c.Phone.Replace("-", "").Replace("(", "").Replace(")", "").Replace(" ", "").Replace("+", "").EndsWith(digits10))
                ))
            .ToListAsync();

        if (candidates.Count == 0) return (null, digits10);
        if (candidates.Count == 1) return (candidates[0], digits10);

        // Multiple tenants share this phone number — pick the one whose company most recently
        // sent an outbound SMS to this number (tiebreaker: most recent NotificationLog entry).
        var candidateIds = candidates.Select(c => c.Id).ToList();

        var mostRecentLog = await _context.NotificationLogs
            .IgnoreQueryFilters()
            .Where(l =>
                l.Channel == NotificationChannel.Sms &&
                l.Status  == NotificationStatus.Sent &&
                l.CustomerId.HasValue &&
                candidateIds.Contains(l.CustomerId.Value))
            .OrderByDescending(l => l.SentAt)
            .Select(l => new { l.CustomerId, l.SentAt })
            .FirstOrDefaultAsync();

        if (mostRecentLog?.CustomerId != null)
        {
            var match = candidates.FirstOrDefault(c => c.Id == mostRecentLog.CustomerId.Value);
            if (match != null)
            {
                _logger.LogInformation(
                    "Multi-tenant phone match resolved to customer {CustomerId} via most recent outbound SMS at {SentAt}",
                    match.Id, mostRecentLog.SentAt);
                return (match, digits10);
            }
        }

        // No outbound log found for any candidate — fall back to first result
        _logger.LogWarning(
            "Multi-tenant phone match for {Digits} could not be resolved by SMS log; using first candidate (CustomerId {CustomerId})",
            digits10, candidates[0].Id);
        return (candidates[0], digits10);
    }

    /// <summary>Writes a NotificationLog row for an inbound STOP or HELP message.</summary>
    private async Task WriteInboundLogAsync(
        NotificationType type,
        Customer customer,
        string fromPhone,
        string body)
    {
        try
        {
            _context.NotificationLogs.Add(new NotificationLog
            {
                Channel          = NotificationChannel.Sms,
                NotificationType = type,
                Status           = NotificationStatus.Sent,
                RecipientName    = GetCustomerDisplayName(customer),
                Recipient        = fromPhone,
                Message          = body,
                SentAt           = DateTime.UtcNow,
                CustomerId       = customer.Id,
                CompanyId        = customer.CompanyId
            });
            await _context.SaveChangesAsync();
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to write inbound SMS log for customer {CustomerId}", customer.Id);
        }
    }

    private async Task<string> GetCompanyNameAsync(int companyId)
    {
        var company = await _context.Companies
            .AsNoTracking()
            .IgnoreQueryFilters()
            .FirstOrDefaultAsync(c => c.Id == companyId);
        return company?.CompanyName ?? "Powder Coating Logix";
    }

    private static string GetCustomerDisplayName(Customer customer)
    {
        var contact = $"{customer.ContactFirstName} {customer.ContactLastName}".Trim();
        if (!string.IsNullOrEmpty(contact)) return contact;
        return customer.CompanyName ?? "Customer";
    }

    /// <summary>Returns an empty TwiML response (no reply sent to sender).</summary>
    private static ContentResult TwimlEmpty() =>
        new ContentResult { Content = "<Response/>", ContentType = "application/xml" };

    /// <summary>Returns a TwiML response that sends <paramref name="message"/> as an SMS reply.</summary>
    private static ContentResult TwimlMessage(string message) =>
        new ContentResult
        {
            Content     = $"<?xml version=\"1.0\" encoding=\"UTF-8\"?><Response><Message>{System.Net.WebUtility.HtmlEncode(message)}</Message></Response>",
            ContentType = "application/xml"
        };

    /// <summary>
    /// Validates the incoming Twilio webhook request using HMAC-SHA1. Local development may skip
    /// validation when the auth token is unconfigured, but shared environments fail closed.
    /// </summary>
    private bool ValidateTwilioRequest()
    {
        var authToken = _configuration["Twilio:AuthToken"];
        if (string.IsNullOrWhiteSpace(authToken) || authToken.StartsWith("your-"))
        {
            if (_environment.IsDevelopment())
            {
                _logger.LogDebug("Twilio auth token not configured in development; skipping signature validation");
                return true;
            }

            _logger.LogError("Twilio auth token is not configured; rejecting webhook request");
            return false;
        }

        var signature = Request.Headers["X-Twilio-Signature"].FirstOrDefault() ?? string.Empty;
        if (string.IsNullOrEmpty(signature))
        {
            _logger.LogWarning("Twilio webhook missing X-Twilio-Signature header");
            return false;
        }

        var url = $"{Request.Scheme}://{Request.Host}{Request.Path}";
        var parameters = new Dictionary<string, string>();
        foreach (var kvp in Request.Form)
            parameters[kvp.Key] = kvp.Value.ToString();

        return new RequestValidator(authToken).Validate(url, parameters, signature);
    }
}

/// <summary>Bound from the Twilio POST form body.</summary>
public class TwilioSmsPayload
{
    public string? From { get; set; }
    public string? Body { get; set; }
    public string? To   { get; set; }
}