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

namespace PowderCoating.Web.Controllers;

/// <summary>
/// SuperAdmin-only dashboard that shows per-company resource usage versus
/// plan limits across users, active jobs, customers, active quotes, and catalog items.
/// Uses <see cref="ApplicationDbContext"/> directly (bypassing UoW) to issue
/// efficient bulk-count GROUP BY queries in parallel rather than loading
/// each company's data through separate repository calls.
/// </summary>
// Intentional exception: cross-tenant bulk GROUP BY quota queries that would require O(n) repository round-trips if routed through IUnitOfWork. See docs/DATA_ACCESS_ARCHITECTURE.md — Permanent Exceptions.
[Authorize(Policy = AppConstants.Policies.SuperAdminOnly)]
public class UsageQuotaController : Controller
{
    private readonly ApplicationDbContext _db;

    public UsageQuotaController(ApplicationDbContext db) => _db = db;

    /// <summary>
    /// Renders the usage quota dashboard with one <see cref="UsageRow"/> per company.
    /// <para>
    /// Design decisions:
    /// <list type="bullet">
    ///   <item>Five separate GROUP BY queries are issued in sequence (not parallel) so
    ///     the same <see cref="ApplicationDbContext"/> instance is not used concurrently.</item>
    ///   <item>Comped companies receive unlimited limits (-1) on every resource because
    ///     they are exempt from plan restrictions by design.</item>
    ///   <item>Company-level overrides (<c>MaxUsersOverride</c> etc.) take precedence
    ///     over plan defaults, enabling per-tenant exceptions without a plan change.</item>
    ///   <item>"Near limit" is defined as ≥ 80 % of the limit; "at limit" is ≥ 100 %.</item>
    ///   <item>The <c>concern</c> filter is applied in-memory after building rows because
    ///     the at/near-limit logic combines data from multiple resource types.</item>
    /// </list>
    /// </para>
    /// </summary>
    public async Task<IActionResult> Index(string? search, string? status, string? plan, string? concern)
    {
        // Plan configs for limit resolution
        var planConfigs = await _db.SubscriptionPlanConfigs
            .AsNoTracking().IgnoreQueryFilters()
            .Where(p => p.IsActive)
            .OrderBy(p => p.SortOrder)
            .ToListAsync();

        var planById = planConfigs.ToDictionary(p => p.Plan);

        // All non-deleted companies
        var companiesQuery = _db.Companies.AsNoTracking().IgnoreQueryFilters()
            .Where(c => !c.IsDeleted);

        if (!string.IsNullOrWhiteSpace(search))
            companiesQuery = companiesQuery.Where(c => c.CompanyName.Contains(search));

        if (!string.IsNullOrWhiteSpace(status) && Enum.TryParse<SubscriptionStatus>(status, out var statusEnum))
            companiesQuery = companiesQuery.Where(c => c.SubscriptionStatus == statusEnum);

        if (!string.IsNullOrWhiteSpace(plan) && int.TryParse(plan, out var planInt))
            companiesQuery = companiesQuery.Where(c => c.SubscriptionPlan == planInt);

        var companies = await companiesQuery.OrderBy(c => c.CompanyName).ToListAsync();
        var companyIds = companies.Select(c => c.Id).ToList();

        // Bulk-fetch usage counts in parallel — one query per resource type
        var userCounts = await _db.Users.AsNoTracking().IgnoreQueryFilters()
            .Where(u => companyIds.Contains(u.CompanyId))
            .GroupBy(u => u.CompanyId)
            .Select(g => new { CompanyId = g.Key, Count = g.Count() })
            .ToDictionaryAsync(x => x.CompanyId, x => x.Count);

        // Active jobs = non-deleted jobs whose status is not a terminal status
        var activeJobCounts = await _db.Jobs.AsNoTracking().IgnoreQueryFilters()
            .Where(j => companyIds.Contains(j.CompanyId) && !j.IsDeleted &&
                        !j.JobStatus.IsTerminalStatus)
            .GroupBy(j => j.CompanyId)
            .Select(g => new { CompanyId = g.Key, Count = g.Count() })
            .ToDictionaryAsync(x => x.CompanyId, x => x.Count);

        var customerCounts = await _db.Customers.AsNoTracking().IgnoreQueryFilters()
            .Where(c => companyIds.Contains(c.CompanyId) && !c.IsDeleted)
            .GroupBy(c => c.CompanyId)
            .Select(g => new { CompanyId = g.Key, Count = g.Count() })
            .ToDictionaryAsync(x => x.CompanyId, x => x.Count);

        // Active quotes = non-deleted quotes not in a terminal status (converted, rejected)
        var quoteCounts = await _db.Quotes.AsNoTracking().IgnoreQueryFilters()
            .Where(q => companyIds.Contains(q.CompanyId) && !q.IsDeleted &&
                        !q.QuoteStatus.IsConvertedStatus && !q.QuoteStatus.IsRejectedStatus)
            .GroupBy(q => q.CompanyId)
            .Select(g => new { CompanyId = g.Key, Count = g.Count() })
            .ToDictionaryAsync(x => x.CompanyId, x => x.Count);

        var catalogCounts = await _db.CatalogItems.AsNoTracking().IgnoreQueryFilters()
            .Where(ci => companyIds.Contains(ci.CompanyId) && !ci.IsDeleted)
            .GroupBy(ci => ci.CompanyId)
            .Select(g => new { CompanyId = g.Key, Count = g.Count() })
            .ToDictionaryAsync(x => x.CompanyId, x => x.Count);

        // Build rows
        int Effective(int? companyOverride, int planDefault) =>
            companyOverride.HasValue ? companyOverride.Value : planDefault;

        var rows = companies.Select(c =>
        {
            var cfg = planById.TryGetValue(c.SubscriptionPlan, out var pc) ? pc : null;

            int users = userCounts.GetValueOrDefault(c.Id);
            int jobs = activeJobCounts.GetValueOrDefault(c.Id);
            int customers = customerCounts.GetValueOrDefault(c.Id);
            int quotes = quoteCounts.GetValueOrDefault(c.Id);
            int catalog = catalogCounts.GetValueOrDefault(c.Id);

            int maxUsers = c.IsComped ? -1 : Effective(c.MaxUsersOverride, cfg?.MaxUsers ?? -1);
            int maxJobs = c.IsComped ? -1 : Effective(c.MaxActiveJobsOverride, cfg?.MaxActiveJobs ?? -1);
            int maxCust = c.IsComped ? -1 : Effective(c.MaxCustomersOverride, cfg?.MaxCustomers ?? -1);
            int maxQuotes = c.IsComped ? -1 : Effective(c.MaxQuotesOverride, cfg?.MaxQuotes ?? -1);
            int maxCatalog = c.IsComped ? -1 : Effective(c.MaxCatalogItemsOverride, cfg?.MaxCatalogItems ?? -1);

            bool IsNearLimit(int used, int max) => max > 0 && used >= max * 0.8;
            bool IsAtLimit(int used, int max) => max > 0 && used >= max;

            bool anyAtLimit = IsAtLimit(users, maxUsers) || IsAtLimit(jobs, maxJobs) ||
                              IsAtLimit(customers, maxCust) || IsAtLimit(quotes, maxQuotes) ||
                              IsAtLimit(catalog, maxCatalog);
            bool anyNearLimit = IsNearLimit(users, maxUsers) || IsNearLimit(jobs, maxJobs) ||
                                IsNearLimit(customers, maxCust) || IsNearLimit(quotes, maxQuotes) ||
                                IsNearLimit(catalog, maxCatalog);

            return new UsageRow
            {
                CompanyId = c.Id,
                CompanyName = c.CompanyName,
                PlanName = cfg?.DisplayName ?? c.SubscriptionPlan.ToString(),
                Status = c.SubscriptionStatus,
                IsActive = c.IsActive,
                IsComped = c.IsComped,
                Users = users, MaxUsers = maxUsers,
                ActiveJobs = jobs, MaxActiveJobs = maxJobs,
                Customers = customers, MaxCustomers = maxCust,
                ActiveQuotes = quotes, MaxActiveQuotes = maxQuotes,
                CatalogItems = catalog, MaxCatalogItems = maxCatalog,
                IsAtLimit = anyAtLimit,
                IsNearLimit = anyNearLimit && !anyAtLimit
            };
        }).ToList();

        // "concern" filter — only show rows with issues
        if (concern == "limit") rows = rows.Where(r => r.IsAtLimit || r.IsNearLimit).ToList();
        else if (concern == "atlimit") rows = rows.Where(r => r.IsAtLimit).ToList();

        ViewBag.Search = search;
        ViewBag.StatusFilter = status;
        ViewBag.PlanFilter = plan;
        ViewBag.ConcernFilter = concern;
        ViewBag.PlanConfigs = planConfigs;
        ViewBag.AtLimitCount = rows.Count(r => r.IsAtLimit);
        ViewBag.NearLimitCount = rows.Count(r => r.IsNearLimit);
        ViewBag.TotalCount = rows.Count;

        return View(rows);
    }
}

public class UsageRow
{
    public int CompanyId { get; set; }
    public string CompanyName { get; set; } = string.Empty;
    public string PlanName { get; set; } = string.Empty;
    public SubscriptionStatus Status { get; set; }
    public bool IsActive { get; set; }
    public bool IsComped { get; set; }
    public int Users { get; set; }
    public int MaxUsers { get; set; }
    public int ActiveJobs { get; set; }
    public int MaxActiveJobs { get; set; }
    public int Customers { get; set; }
    public int MaxCustomers { get; set; }
    public int ActiveQuotes { get; set; }
    public int MaxActiveQuotes { get; set; }
    public int CatalogItems { get; set; }
    public int MaxCatalogItems { get; set; }
    public bool IsAtLimit { get; set; }
    public bool IsNearLimit { get; set; }
}