using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using PowderCoating.Core.Enums;
using PowderCoating.Infrastructure.Data;
using PowderCoating.Shared.Constants;

namespace PowderCoating.Web.Controllers;

/// <summary>
/// SuperAdmin-only revenue intelligence dashboard that aggregates subscription
/// metrics across all tenant companies.  Uses <see cref="ApplicationDbContext"/>
/// directly (bypassing the UoW) because it queries across company boundaries and
/// joins plan configs — a pattern that would require multiple unrelated repositories.
/// </summary>
// Intentional exception: cross-tenant MRR/ARR metrics joining Company + SubscriptionPlanConfig; same pattern as CompanyHealthController. See docs/DATA_ACCESS_ARCHITECTURE.md — Permanent Exceptions.
[Authorize(Policy = AppConstants.Policies.SuperAdminOnly)]
public class RevenueController : Controller
{
    private readonly ApplicationDbContext _db;

    public RevenueController(ApplicationDbContext db)
    {
        _db = db;
    }

    /// <summary>
    /// Renders the platform revenue dashboard with MRR, ARR, plan distribution,
    /// a 12-month MRR trend, and a list of companies needing subscription attention.
    /// <para>
    /// Design decisions:
    /// <list type="bullet">
    ///   <item>Demo company (Id = 1) and comped companies are excluded from all
    ///     revenue figures because they do not represent real subscription income.</item>
    ///   <item>The 12-month MRR trend is an approximation — it estimates active
    ///     subscribers per historical month using <c>CreatedAt</c> and current status,
    ///     not a ledger of actual billing events, because no billing-transactions table
    ///     exists yet.</item>
    ///   <item><c>IgnoreQueryFilters()</c> is required throughout so that the global
    ///     multi-tenancy filter does not restrict visibility to a single company.</item>
    /// </list>
    /// </para>
    /// </summary>
    public async Task<IActionResult> Index()
    {
        var now = DateTime.UtcNow;
        var thisMonthStart = new DateTime(now.Year, now.Month, 1);
        var lastMonthStart = thisMonthStart.AddMonths(-1);

        // Plan configs (price lookup)
        var planConfigs = await _db.SubscriptionPlanConfigs
            .AsNoTracking().IgnoreQueryFilters()
            .Where(p => p.IsActive)
            .OrderBy(p => p.SortOrder)
            .ToListAsync();

        var priceByPlan = planConfigs.ToDictionary(p => p.Plan, p => p.MonthlyPrice);
        string PlanName(int plan) => planConfigs.FirstOrDefault(p => p.Plan == plan)?.DisplayName ?? plan.ToString();

        // Exclude demo company (Id 1) and comped companies from revenue calculations;
        // they don't represent real subscription income.
        const int DemoCompanyId = 1;

        var companies = await _db.Companies
            .AsNoTracking().IgnoreQueryFilters()
            .Where(c => !c.IsDeleted && c.Id != DemoCompanyId && !c.IsComped)
            .ToListAsync();

        // Comped companies are excluded from revenue but must be counted separately
        // so the status table in the view sums to a correct total.
        var compedCount = await _db.Companies
            .AsNoTracking().IgnoreQueryFilters()
            .CountAsync(c => !c.IsDeleted && c.Id != DemoCompanyId && c.IsComped);

        // ── Revenue metrics ──────────────────────────────────────────────

        // Active paying companies
        var payingActive = companies
            .Where(c =>
                        (c.SubscriptionStatus == SubscriptionStatus.Active ||
                         c.SubscriptionStatus == SubscriptionStatus.GracePeriod))
            .ToList();

        var mrr = payingActive.Sum(c =>
            priceByPlan.TryGetValue(c.SubscriptionPlan, out var price) ? price : 0m);

        var arr = mrr * 12;

        // Average revenue per paying company
        var avgRevenue = payingActive.Count > 0 ? mrr / payingActive.Count : 0m;

        // ── Company counts ───────────────────────────────────────────────
        // totalCompanies includes comped so that Active + GracePeriod + Expired + Canceled + Comped = Total.
        var totalCompanies  = companies.Count + compedCount;
        var activeCount     = companies.Count(c => c.SubscriptionStatus == SubscriptionStatus.Active);
        var gracePeriodCount = companies.Count(c => c.SubscriptionStatus == SubscriptionStatus.GracePeriod);
        var expiredCount    = companies.Count(c => c.SubscriptionStatus == SubscriptionStatus.Expired);
        var canceledCount   = companies.Count(c =>
            c.SubscriptionStatus == SubscriptionStatus.Canceled ||
            c.SubscriptionStatus == SubscriptionStatus.Inactive);
        var stripeCount     = companies.Count(c => !string.IsNullOrEmpty(c.StripeSubscriptionId));

        // ── Month-over-month ─────────────────────────────────────────────
        var newThisMonth = companies.Count(c => c.CreatedAt >= thisMonthStart);
        var newLastMonth = companies.Count(c => c.CreatedAt >= lastMonthStart && c.CreatedAt < thisMonthStart);
        var churnThisMonth = companies.Count(c =>
            c.UpdatedAt >= thisMonthStart &&
            (c.SubscriptionStatus == SubscriptionStatus.Canceled ||
             c.SubscriptionStatus == SubscriptionStatus.Expired));

        // ── Plan distribution ────────────────────────────────────────────
        var planDistribution = companies
            .Where(c => !c.IsComped &&
                        (c.SubscriptionStatus == SubscriptionStatus.Active ||
                         c.SubscriptionStatus == SubscriptionStatus.GracePeriod))
            .GroupBy(c => c.SubscriptionPlan)
            .Select(g => new PlanMetricRow
            {
                PlanId = g.Key,
                PlanName = PlanName(g.Key),
                CompanyCount = g.Count(),
                MonthlyPrice = priceByPlan.TryGetValue(g.Key, out var p) ? p : 0m,
                Revenue = g.Sum(c => priceByPlan.TryGetValue(c.SubscriptionPlan, out var pr) ? pr : 0m)
            })
            .OrderByDescending(r => r.Revenue)
            .ToList();

        // ── Approximated 12-month trend ──────────────────────────────────
        // We estimate MRR per month by looking at company creation dates.
        // (No billing transactions table yet — this is an approximation.)
        var trendMonths = new List<MrrTrendPoint>();
        for (int i = 11; i >= 0; i--)
        {
            var monthStart = new DateTime(now.Year, now.Month, 1).AddMonths(-i);
            var monthEnd = monthStart.AddMonths(1);

            var activeInMonth = companies
                .Where(c =>
                    !c.IsComped &&
                    c.CreatedAt < monthEnd &&
                    (c.SubscriptionStatus == SubscriptionStatus.Active ||
                     c.SubscriptionStatus == SubscriptionStatus.GracePeriod ||
                     c.CreatedAt >= monthStart)) // simplification
                .ToList();

            var mrrPoint = activeInMonth.Sum(c =>
                priceByPlan.TryGetValue(c.SubscriptionPlan, out var pr) ? pr : 0m);

            trendMonths.Add(new MrrTrendPoint
            {
                Month = monthStart.ToString("MMM yy"),
                Mrr = mrrPoint,
                CompanyCount = activeInMonth.Count
            });
        }

        // ── Companies needing attention ──────────────────────────────────
        var alerts = companies
            .Where(c =>
                c.SubscriptionStatus == SubscriptionStatus.GracePeriod ||
                c.SubscriptionStatus == SubscriptionStatus.Expired ||
                (c.SubscriptionStatus == SubscriptionStatus.Active &&
                 c.SubscriptionEndDate.HasValue &&
                 c.SubscriptionEndDate.Value <= now.AddDays(14) &&
                 !c.IsComped))
            .OrderBy(c => c.SubscriptionEndDate)
            .Take(20)
            .Select(c => new SubscriptionAlertRow
            {
                Id = c.Id,
                CompanyName = c.CompanyName,
                PlanName = PlanName(c.SubscriptionPlan),
                Status = c.SubscriptionStatus,
                EndDate = c.SubscriptionEndDate,
                DaysUntilExpiry = c.SubscriptionEndDate.HasValue
                    ? (int)(c.SubscriptionEndDate.Value.Date - now.Date).TotalDays
                    : 0,
                IsComped = c.IsComped
            })
            .ToList();

        var vm = new RevenueDashboardViewModel
        {
            Mrr = mrr,
            Arr = arr,
            AvgRevenuePerCompany = avgRevenue,
            TotalCompanies = totalCompanies,
            ActiveCount = activeCount,
            GracePeriodCount = gracePeriodCount,
            ExpiredCount = expiredCount,
            CanceledCount = canceledCount,
            CompedCount = compedCount,
            StripeManaged = stripeCount,
            NewThisMonth = newThisMonth,
            NewLastMonth = newLastMonth,
            ChurnThisMonth = churnThisMonth,
            PlanDistribution = planDistribution,
            TrendMonths = trendMonths,
            SubscriptionAlerts = alerts
        };

        return View(vm);
    }
}

// ── Local view models (scoped to this controller file) ───────────────────────

public class RevenueDashboardViewModel
{
    public decimal Mrr { get; set; }
    public decimal Arr { get; set; }
    public decimal AvgRevenuePerCompany { get; set; }

    public int TotalCompanies { get; set; }
    public int ActiveCount { get; set; }
    public int GracePeriodCount { get; set; }
    public int ExpiredCount { get; set; }
    public int CanceledCount { get; set; }
    public int CompedCount { get; set; }
    public int StripeManaged { get; set; }

    public int NewThisMonth { get; set; }
    public int NewLastMonth { get; set; }
    public int ChurnThisMonth { get; set; }

    public List<PlanMetricRow> PlanDistribution { get; set; } = new();
    public List<MrrTrendPoint> TrendMonths { get; set; } = new();
    public List<SubscriptionAlertRow> SubscriptionAlerts { get; set; } = new();
}

public class PlanMetricRow
{
    public int PlanId { get; set; }
    public string PlanName { get; set; } = string.Empty;
    public int CompanyCount { get; set; }
    public decimal MonthlyPrice { get; set; }
    public decimal Revenue { get; set; }
}

public class MrrTrendPoint
{
    public string Month { get; set; } = string.Empty;
    public decimal Mrr { get; set; }
    public int CompanyCount { get; set; }
}

public class SubscriptionAlertRow
{
    public int Id { get; set; }
    public string CompanyName { get; set; } = string.Empty;
    public string PlanName { get; set; } = string.Empty;
    public SubscriptionStatus Status { get; set; }
    public DateTime? EndDate { get; set; }
    public int DaysUntilExpiry { get; set; }
    public bool IsComped { get; set; }
}