using Fitness_core_BE.Domain;
using Fitness_core_BE.Exceptions;
using Fitness_core_BE.Helpers;
using Fitness_core_BE.Infra.UoW;
using Fitness_core_BE.Interfaces;
using Fitness_core_BE.Interfaces.Services;
using Fitness_core_BE.Models;
using Microsoft.AspNetCore.Http;

namespace Fitness_core_BE.Services
{
    // Staff-facing approval workflow for the unapproved (IsActive=false) invoices the daily
    // SubscriptionRenewalJob sweep creates -- approve/change-plan/reject are the only things
    // that ever advance CustomerSubscription.RenewalDate or replace a subscription's plan; the
    // daily sweep itself only ever creates unapproved invoices.
    public class SubscriptionRenewalApprovalService : ISubscriptionRenewalApprovalService
    {
        private readonly ICustomerInvoiceRepository _invoiceRepository;
        private readonly ICustomerSubscriptionRepository _subscriptionRepository;
        private readonly IClientRepository _clientRepository;
        private readonly IUnitOfWork _uow;
        private readonly UserRoleHelper _userRoleHelper;
        private readonly ILogger<SubscriptionRenewalApprovalService> _logger;

        public SubscriptionRenewalApprovalService(
            ICustomerInvoiceRepository invoiceRepository,
            ICustomerSubscriptionRepository subscriptionRepository,
            IClientRepository clientRepository,
            IUnitOfWork uow,
            UserRoleHelper userRoleHelper,
            ILogger<SubscriptionRenewalApprovalService> logger)
        {
            _invoiceRepository = invoiceRepository;
            _subscriptionRepository = subscriptionRepository;
            _clientRepository = clientRepository;
            _uow = uow;
            _userRoleHelper = userRoleHelper;
            _logger = logger;
        }

        public async Task<object> GetUnapprovedInvoicesAsync(HttpContext httpContext)
        {
            var clientId = await _userRoleHelper.GetClientId(DataExtractor.GetUserIdFromContext(httpContext));
            var invoices = await _invoiceRepository.GetUnapprovedInvoicesByClientIdAsync(clientId);

            // How much of `amount` is this cycle's own charge vs. debt carried over from a prior
            // Pending/Partial invoice -- the approvals list shows the total already, but staff
            // reviewing a renewal need to see the breakdown before approving it.
            var carriedForward = await _invoiceRepository.GetCarriedForwardAmountsAsync(
                invoices.Select(i => i.CustomerInvoiceId).ToList());

            return invoices.Select(i =>
            {
                carriedForward.TryGetValue(i.CustomerInvoiceId, out var carriedForwardAmount);
                return new
                {
                    customerInvoiceId = i.CustomerInvoiceId,
                    fkCustomerSubscriptionId = i.FKCustomerSubscriptionId,
                    amount = i.Amount,
                    carriedForwardAmount,
                    status = i.Status,
                    customerInvoiceDate = i.CustomerInvoiceDate,
                    customerName = i.CustomerSubscription?.TenantCustomerLink?.DisplayName,
                    planName = i.CustomerSubscription?.CustomerPlan?.PlanName,
                    planPrice = i.CustomerSubscription?.CustomerPlan?.PlanPrice,
                };
            }).ToList();
        }

        public async Task<object> ApproveAsync(Guid customerInvoiceId, HttpContext httpContext)
        {
            var clientId = await _userRoleHelper.GetClientId(DataExtractor.GetUserIdFromContext(httpContext));

            await _uow.BeginAsync();
            try
            {
                var invoice = await LoadUnapprovedInvoiceForClientAsync(customerInvoiceId, clientId);
                var subscription = invoice.CustomerSubscription;
                var plan = subscription.CustomerPlan
                    ?? throw new BadRequestException("This subscription's plan could not be found.");

                var now = DateTime.UtcNow;

                // Installments are keyed by subscription, not by invoice/cycle -- the prior
                // cycle's rows must be removed before this cycle's schedule is added (see
                // DeactivatePriorInstallmentsAsync for why this is a hard delete).
                await _subscriptionRepository.DeactivatePriorInstallmentsAsync(subscription.SubscriptionId);
                var installments = CustomerSubscriptionFactory.BuildInstallmentSchedule(
                    subscription, plan, now, anchorDate: now);
                await _subscriptionRepository.AddInstallmentsAsync(installments);

                invoice.IsActive = true;

                // Advance from the OLD RenewalDate, not from "now" -- a late approval shouldn't
                // shift the cadence of future cycles.
                var newRenewalDate = (subscription.RenewalDate ?? now).AddDays(plan.DurationInDays);
                await _subscriptionRepository.AdvanceRenewalDateAsync(subscription.SubscriptionId, newRenewalDate);

                // Session-count cycle reset (SessionsPerCycle plans only -- unlimited-access
                // plans have nothing to reset). Whatever was left unused this ending cycle either
                // rolls into the new one (GracePeriod, until RolloverGraceDays elapses) or is
                // forfeited (NoRollover) -- see the fields' own comments on CustomerPlan/
                // CustomerSubscription for the full reasoning.
                if (plan.SessionsPerCycle.HasValue)
                {
                    var allowanceThisCycle = plan.SessionsPerCycle.Value + subscription.SessionsCarriedOver;
                    var unusedThisCycle = Math.Max(0, allowanceThisCycle - subscription.SessionsUsedThisCycle);

                    if (plan.SessionRolloverPolicy == "GracePeriod" && unusedThisCycle > 0)
                    {
                        subscription.SessionsCarriedOver = unusedThisCycle;
                        subscription.SessionsCarriedOverExpiresAt = now.AddDays(plan.RolloverGraceDays);
                    }
                    else
                    {
                        subscription.SessionsCarriedOver = 0;
                        subscription.SessionsCarriedOverExpiresAt = null;
                    }

                    subscription.SessionsUsedThisCycle = 0;
                }

                await _uow.SaveChangesAsync();
                await _uow.CommitAsync();

                _logger.LogInformation(
                    "SubscriptionRenewalApproval: invoice {InvoiceId} approved for subscription {SubscriptionId}; RenewalDate advanced to {RenewalDate:u}.",
                    customerInvoiceId, subscription.SubscriptionId, newRenewalDate);

                return new
                {
                    success = true,
                    message = "Renewal approved",
                    customerInvoiceId,
                    subscriptionId = subscription.SubscriptionId,
                    renewalDate = newRenewalDate
                };
            }
            catch
            {
                await _uow.RollbackAsync();
                throw;
            }
        }

        public async Task<object> ChangePlanAsync(Guid customerInvoiceId, Guid newCustomerPlanId, HttpContext httpContext)
        {
            var clientId = await _userRoleHelper.GetClientId(DataExtractor.GetUserIdFromContext(httpContext));

            await _uow.BeginAsync();
            try
            {
                var invoice = await LoadUnapprovedInvoiceForClientAsync(customerInvoiceId, clientId);
                var oldSubscription = invoice.CustomerSubscription;

                var newPlan = await _clientRepository.GetCustomerPlanEntityForClientAsync(newCustomerPlanId, clientId)
                    ?? throw new NotFoundException("Membership plan not found.");
                if (newPlan.PlanScope != "Individual")
                    throw new BadRequestException("Change Membership only supports Individual-scope plans.");

                var oldMembership = await _clientRepository.GetActiveMembershipForCustomerAsync(oldSubscription.FKCustomerId);

                // Sibling namespace Fitness_core_BE.Services.CustomerSubscription
                // (CustomerSubscriptionService.cs) outranks a bare `CustomerSubscription` here.
                var newSubscription = new Fitness_core_BE.Models.CustomerSubscription
                {
                    FKCustomerPlanId = newCustomerPlanId,
                    FKCustomerId = oldSubscription.FKCustomerId,
                    OnboardDate = DateTime.UtcNow,
                    IsActive = true
                };
                var initialSubItem = new CustomerSubItem
                {
                    SubItemName = "Membership change (renewal approval)",
                    IsActive = true
                };
                var aggregate = CustomerSubscriptionFactory.Create(newSubscription, newPlan, initialSubItem);

                await _clientRepository.ReplaceCustomerSubscriptionAsync(oldMembership, aggregate);
                // RepointAndRecalculateInvoiceAsync re-queries the new subscription by id, so it
                // must be persisted first.
                await _uow.SaveChangesAsync();

                await _invoiceRepository.RepointAndRecalculateInvoiceAsync(customerInvoiceId, newSubscription.SubscriptionId);
                await _uow.SaveChangesAsync();
                await _uow.CommitAsync();

                _logger.LogInformation(
                    "SubscriptionRenewalApproval: invoice {InvoiceId} approved via plan change -- subscription {OldSubscriptionId} replaced by {NewSubscriptionId} on plan {NewPlanId}.",
                    customerInvoiceId, oldSubscription.SubscriptionId, newSubscription.SubscriptionId, newCustomerPlanId);

                return new
                {
                    success = true,
                    message = "Plan changed and renewal approved",
                    customerInvoiceId,
                    subscriptionId = newSubscription.SubscriptionId
                };
            }
            catch
            {
                await _uow.RollbackAsync();
                throw;
            }
        }

        public async Task<object> RejectAsync(Guid customerInvoiceId, HttpContext httpContext)
        {
            var clientId = await _userRoleHelper.GetClientId(DataExtractor.GetUserIdFromContext(httpContext));

            await _uow.BeginAsync();
            try
            {
                var invoice = await LoadUnapprovedInvoiceForClientAsync(customerInvoiceId, clientId);

                // Already IsActive=false (that's what put it in the approval queue) -- Status
                // also needs a terminal value, otherwise it still reads as an outstanding invoice
                // everywhere that isn't IsActive-filtered (e.g. GetCustomerInvoicesByClientId).
                invoice.Status = "Cancelled";
                invoice.IsActive = false;

                await _clientRepository.DeactivateSubscriptionAsync(invoice.FKCustomerSubscriptionId);

                await _uow.SaveChangesAsync();
                await _uow.CommitAsync();

                _logger.LogInformation(
                    "SubscriptionRenewalApproval: invoice {InvoiceId} rejected; subscription {SubscriptionId} deactivated.",
                    customerInvoiceId, invoice.FKCustomerSubscriptionId);

                return new { success = true, message = "Renewal rejected", customerInvoiceId };
            }
            catch
            {
                await _uow.RollbackAsync();
                throw;
            }
        }

        // Sibling namespace Fitness_core_BE.Services.CustomerInvoice (CustomerInvoiceService.cs)
        // outranks a bare `CustomerInvoice` here, so the model type needs its full name.
        private async Task<Fitness_core_BE.Models.CustomerInvoice> LoadUnapprovedInvoiceForClientAsync(Guid customerInvoiceId, Guid clientId)
        {
            var invoice = await _invoiceRepository.GetCustomerInvoiceById(customerInvoiceId)
                ?? throw new NotFoundException("Invoice not found.");

            if (invoice.FKClientId != clientId)
                throw new ForbiddenException("This invoice does not belong to your gym.");

            if (invoice.IsActive)
                throw new BadRequestException("This invoice has already been approved or is not awaiting approval.");

            return invoice;
        }
    }
}