using Microsoft.EntityFrameworkCore;
using PowderCoating.Application.Interfaces;
using PowderCoating.Core.Entities;
using PowderCoating.Core.Enums;
using PowderCoating.Core.Interfaces;
using PowderCoating.Infrastructure.Data;
using PowderCoating.Shared.Constants;

namespace PowderCoating.Infrastructure.Services;

/// <summary>
/// Manages subscription-based feature gating and resource-limit enforcement for tenant companies.
/// All limit checks follow a consistent priority order:
/// <list type="number">
///   <item><description>Comped companies (<c>Company.IsComped == true</c>) bypass every limit
///   and are always treated as having unlimited allowances — useful for demo accounts,
///   partners, and internal testing.</description></item>
///   <item><description>Per-company overrides (<c>Company.Max*Override</c>) take precedence
///   over plan defaults, enabling SuperAdmins to grant exceptions without changing the plan.</description></item>
///   <item><description><see cref="SubscriptionPlanConfig"/> provides the plan-level defaults
///   looked up by <c>Company.SubscriptionPlan</c>.</description></item>
///   <item><description>Hard-coded fallbacks in each method guard against missing plan config rows.</description></item>
/// </list>
/// All count queries use <c>IgnoreQueryFilters()</c> to include soft-deleted records where
/// relevant, preventing a company from circumventing limits by deleting and re-adding records.
/// </summary>
public class SubscriptionService : ISubscriptionService
{
    private readonly IUnitOfWork _unitOfWork;
    private readonly ApplicationDbContext _context;
    private readonly IPlatformSettingsService _platformSettings;

    public SubscriptionService(IUnitOfWork unitOfWork, ApplicationDbContext context, IPlatformSettingsService platformSettings)
    {
        _unitOfWork = unitOfWork;
        _context = context;
        _platformSettings = platformSettings;
    }

    /// <summary>
    /// Returns <c>true</c> if the company can add another active user account.
    /// Unlimited is indicated by <see cref="AppConstants.SubscriptionConstants.UnlimitedValue"/>
    /// (-1) which short-circuits the count check.
    /// </summary>
    public async Task<bool> CanAddUserAsync(int companyId)
    {
        var (used, max) = await GetUserCountAsync(companyId);
        return max == AppConstants.SubscriptionConstants.UnlimitedValue || used < max;
    }

    /// <summary>
    /// Returns <c>true</c> if the company can create another active (non-terminal) job.
    /// Terminal statuses are Completed, Delivered, and Cancelled — jobs in those states
    /// do not count against the active-job limit because they no longer consume shop capacity.
    /// </summary>
    public async Task<bool> CanAddJobAsync(int companyId)
    {
        var (used, max) = await GetJobCountAsync(companyId);
        return max == AppConstants.SubscriptionConstants.UnlimitedValue || used < max;
    }

    /// <summary>
    /// Returns <c>true</c> if the company can add another customer record.
    /// The count includes soft-deleted customers (<c>IgnoreQueryFilters</c>) to prevent
    /// the limit from being gamed by deleting and re-creating customers.
    /// </summary>
    public async Task<bool> CanAddCustomerAsync(int companyId)
    {
        var (used, max) = await GetCustomerCountAsync(companyId);
        return max == AppConstants.SubscriptionConstants.UnlimitedValue || used < max;
    }

    /// <summary>
    /// Returns <c>true</c> if the company can create another quote this calendar month.
    /// Quote limits are intentionally per-calendar-month (not per-billing-period) so that
    /// the reset is predictable for end users regardless of when their subscription renews.
    /// </summary>
    public async Task<bool> CanAddQuoteAsync(int companyId)
    {
        var (used, max) = await GetQuoteCountAsync(companyId);
        return max == AppConstants.SubscriptionConstants.UnlimitedValue || used < max;
    }

    /// <summary>
    /// Returns <c>true</c> if the company can add another catalog service item.
    /// </summary>
    public async Task<bool> CanAddCatalogItemAsync(int companyId)
    {
        var (used, max) = await GetCatalogItemCountAsync(companyId);
        return max == AppConstants.SubscriptionConstants.UnlimitedValue || used < max;
    }

    /// <summary>
    /// Returns the current active user count and the plan maximum for the company.
    /// Comped companies always return (0, Unlimited) to short-circuit all UI limit displays.
    /// The per-company override (<c>MaxUsersOverride</c>) is checked before the plan config,
    /// letting SuperAdmins grant a higher seat count without upgrading the plan.
    /// Falls back to 3 when neither override nor plan config is present.
    /// </summary>
    public async Task<(int Used, int Max)> GetUserCountAsync(int companyId)
    {
        var (company, config) = await GetCompanyAndConfigAsync(companyId);
        if (company?.IsComped == true) return (0, AppConstants.SubscriptionConstants.UnlimitedValue);
        var used = await _context.Users
            .Where(u => u.CompanyId == companyId && u.IsActive)
            .CountAsync();
        var max = company?.MaxUsersOverride ?? config?.MaxUsers ?? 3;
        return (used, max);
    }

    /// <summary>
    /// Returns the active job count and the plan maximum.
    /// Only non-terminal jobs contribute to the count; a JOIN against <c>JobStatusLookups</c>
    /// is required because job status is a lookup-table entity, not an enum (see AI Accounting
    /// Features in MEMORY.md).  <c>IgnoreQueryFilters()</c> is needed here because the global
    /// multi-tenancy filter would normally restrict to the current HTTP context's company, but
    /// this service is also called from background middleware where no HTTP context exists.
    /// Falls back to 50 active jobs when no plan config is found.
    /// </summary>
    public async Task<(int Used, int Max)> GetJobCountAsync(int companyId)
    {
        var (company, config) = await GetCompanyAndConfigAsync(companyId);
        if (company?.IsComped == true) return (0, AppConstants.SubscriptionConstants.UnlimitedValue);

        var terminalStatusCodes = new[] { "Completed", "Delivered", "Cancelled" };
        var used = await _context.Jobs
            .IgnoreQueryFilters()
            .Where(j => j.CompanyId == companyId && !j.IsDeleted)
            .Join(_context.JobStatusLookups.IgnoreQueryFilters(),
                j => j.JobStatusId,
                s => s.Id,
                (j, s) => new { j, s })
            .Where(x => !terminalStatusCodes.Contains(x.s.StatusCode))
            .CountAsync();

        var max = company?.MaxActiveJobsOverride ?? config?.MaxActiveJobs ?? 50;
        return (used, max);
    }

    /// <summary>
    /// Returns the total customer count (including soft-deleted) and the plan maximum.
    /// Soft-deleted records are counted to prevent limit circumvention.
    /// Falls back to 100 customers when no plan config is present.
    /// </summary>
    public async Task<(int Used, int Max)> GetCustomerCountAsync(int companyId)
    {
        var (company, config) = await GetCompanyAndConfigAsync(companyId);
        if (company?.IsComped == true) return (0, AppConstants.SubscriptionConstants.UnlimitedValue);
        var used = await _context.Customers
            .IgnoreQueryFilters()
            .Where(c => c.CompanyId == companyId && !c.IsDeleted)
            .CountAsync();
        var max = company?.MaxCustomersOverride ?? config?.MaxCustomers ?? 100;
        return (used, max);
    }

    /// <summary>
    /// Returns the number of quotes created this calendar month and the monthly plan limit.
    /// The window is anchored to UTC midnight on the first of the current month.
    /// A limit of -1 (<see cref="AppConstants.SubscriptionConstants.UnlimitedValue"/>) means no cap.
    /// </summary>
    public async Task<(int Used, int Max)> GetQuoteCountAsync(int companyId)
    {
        var (company, config) = await GetCompanyAndConfigAsync(companyId);
        if (company?.IsComped == true) return (0, AppConstants.SubscriptionConstants.UnlimitedValue);

        var startOfMonth = new DateTime(DateTime.UtcNow.Year, DateTime.UtcNow.Month, 1, 0, 0, 0, DateTimeKind.Utc);
        var used = await _context.Quotes
            .IgnoreQueryFilters()
            .Where(q => q.CompanyId == companyId && q.CreatedAt >= startOfMonth)
            .CountAsync();

        var max = company?.MaxQuotesOverride ?? config?.MaxQuotes ?? -1;
        return (used, max);
    }

    /// <summary>
    /// Determines the overall subscription status of a company.
    /// The status progression is: Active → GracePeriod → Expired.
    /// <list type="bullet">
    ///   <item><description>Comped companies are permanently <see cref="SubscriptionStatus.Active"/>
    ///   regardless of <c>SubscriptionEndDate</c>.</description></item>
    ///   <item><description>Companies with no <c>SubscriptionEndDate</c> are treated as Active
    ///   (e.g., manual invoicing arrangements that don't set an end date).</description></item>
    ///   <item><description>Companies within the grace period
    ///   (<see cref="AppConstants.SubscriptionConstants.GracePeriodDays"/> days after expiry)
    ///   can still log in but see an expiry banner.</description></item>
    ///   <item><description>Companies past the grace period are <see cref="SubscriptionStatus.Expired"/>
    ///   and are blocked by <c>SubscriptionMiddleware</c>.</description></item>
    /// </list>
    /// </summary>
    public async Task<SubscriptionStatus> GetStatusAsync(int companyId)
    {
        var company = await _unitOfWork.Companies.GetByIdAsync(companyId, ignoreQueryFilters: true);
        if (company == null || !company.IsActive)
            return SubscriptionStatus.Inactive;

        // Comped companies are always Active regardless of end date
        if (company.IsComped)
            return SubscriptionStatus.Active;

        if (company.SubscriptionEndDate == null)
            return SubscriptionStatus.Active;

        var daysUntil = DaysUntilExpiry(company);
        if (daysUntil == null || daysUntil > 0)
            return SubscriptionStatus.Active;

        var graceDays = await GetEffectiveGracePeriodDaysAsync(company);
        if (daysUntil >= -graceDays)
            return SubscriptionStatus.GracePeriod;

        return SubscriptionStatus.Expired;
    }

    /// <summary>
    /// Calculates the number of days remaining until <c>SubscriptionEndDate</c> (positive)
    /// or the number of days since expiry (negative).  Returns <c>null</c> when the company
    /// has no end date, which the caller interprets as "does not expire."
    /// Date-only comparison (using <c>.Date</c>) ensures the result does not fluctuate
    /// based on the time of day the check is performed.
    /// </summary>
    public int? DaysUntilExpiry(Company company)
    {
        if (company.SubscriptionEndDate == null)
            return null;

        var today = DateTime.UtcNow.Date;
        var expiry = company.SubscriptionEndDate.Value.Date;
        return (int)(expiry - today).TotalDays;
    }

    /// <summary>
    /// Returns the effective grace period in days for a company. Trial companies (no Stripe subscription)
    /// get 0 days unless the <c>GracePeriodAppliesToTrials</c> platform setting is explicitly enabled.
    /// Paid companies always use the configured <c>GracePeriodDays</c> value.
    /// </summary>
    private async Task<int> GetEffectiveGracePeriodDaysAsync(Company company)
    {
        var isTrial = string.IsNullOrEmpty(company.StripeSubscriptionId);
        if (isTrial)
        {
            var appliesToTrials = await _platformSettings.GetBoolAsync(
                PlatformSettingKeys.GracePeriodAppliesToTrials, defaultValue: false);
            if (!appliesToTrials) return 0;
        }
        return await _platformSettings.GetIntAsync(
            PlatformSettingKeys.GracePeriodDays,
            AppConstants.SubscriptionConstants.GracePeriodDays);
    }

    /// <summary>
    /// Returns the total catalog item count (including soft-deleted) and the plan maximum.
    /// Returns a max of -1 when the plan config is absent (unlimited by default).
    /// </summary>
    public async Task<(int Used, int Max)> GetCatalogItemCountAsync(int companyId)
    {
        var (company, config) = await GetCompanyAndConfigAsync(companyId);
        if (company?.IsComped == true) return (0, AppConstants.SubscriptionConstants.UnlimitedValue);
        var used = await _context.CatalogItems
            .IgnoreQueryFilters()
            .Where(c => c.CompanyId == companyId && !c.IsDeleted)
            .CountAsync();
        return (used, company?.MaxCatalogItemsOverride ?? config?.MaxCatalogItems ?? -1);
    }

    /// <summary>
    /// Returns <c>true</c> if the company can attach another photo to the specified job.
    /// Photo limits are enforced per-job (not per-company) to prevent any single job from
    /// accumulating an unreasonable number of attachments while still allowing the overall
    /// company photo volume to grow with the number of jobs.
    /// </summary>
    public async Task<bool> CanAddJobPhotoAsync(int companyId, int jobId)
    {
        var (used, max) = await GetJobPhotoCountAsync(companyId, jobId);
        return max == AppConstants.SubscriptionConstants.UnlimitedValue || used < max;
    }

    /// <summary>
    /// Returns the current photo count and the per-job limit for the specified job.
    /// AI analysis photos (<c>IsAiAnalysisPhoto == true</c>) are excluded from the count
    /// because they are transient artifacts of the AI quoting process, not permanent
    /// customer-uploaded reference photos.
    /// </summary>
    public async Task<(int Used, int Max)> GetJobPhotoCountAsync(int companyId, int jobId)
    {
        var (company, config) = await GetCompanyAndConfigAsync(companyId);
        if (company?.IsComped == true) return (0, AppConstants.SubscriptionConstants.UnlimitedValue);
        var max = company?.MaxJobPhotosOverride ?? config?.MaxJobPhotos ?? -1;
        var used = await _context.JobPhotos
            .IgnoreQueryFilters()
            .Where(p => p.JobId == jobId && p.CompanyId == companyId && !p.IsDeleted && !p.IsAiAnalysisPhoto)
            .CountAsync();
        return (used, max);
    }

    /// <summary>
    /// Returns <c>true</c> if the company can attach another photo to the specified quote.
    /// </summary>
    public async Task<bool> CanAddQuotePhotoAsync(int companyId, int quoteId)
    {
        var (used, max) = await GetQuotePhotoCountAsync(companyId, quoteId);
        return max == AppConstants.SubscriptionConstants.UnlimitedValue || used < max;
    }

    /// <summary>
    /// Returns the current photo count and the per-quote limit for the specified quote.
    /// AI analysis photos are excluded for the same reason as <see cref="GetJobPhotoCountAsync"/>.
    /// </summary>
    public async Task<(int Used, int Max)> GetQuotePhotoCountAsync(int companyId, int quoteId)
    {
        var (company, config) = await GetCompanyAndConfigAsync(companyId);
        if (company?.IsComped == true) return (0, AppConstants.SubscriptionConstants.UnlimitedValue);
        var max = company?.MaxQuotePhotosOverride ?? config?.MaxQuotePhotos ?? -1;
        var used = await _context.QuotePhotos
            .IgnoreQueryFilters()
            .Where(p => p.QuoteId == quoteId && p.CompanyId == companyId && !p.IsDeleted && !p.IsAiAnalysisPhoto)
            .CountAsync();
        return (used, max);
    }

    /// <summary>
    /// Returns <c>true</c> when the AI Inventory Assist feature is available for the company.
    /// Two gates must both pass: (1) the plan must have <c>AllowAiInventoryAssist</c> set to
    /// <c>true</c> in <see cref="SubscriptionPlanConfig"/>, and (2) the company-level
    /// <c>AiInventoryAssistEnabled</c> flag must be <c>true</c> (a SuperAdmin toggle).
    /// Comped companies bypass both gates.
    /// </summary>
    public async Task<bool> IsAiInventoryAssistEnabledAsync(int companyId)
    {
        var (company, config) = await GetCompanyAndConfigAsync(companyId);
        if (company == null) return false;
        if (company.IsComped) return true;

        // Plan-level gate: feature must be enabled on the plan
        if (config != null && !config.AllowAiInventoryAssist) return false;

        return company.AiInventoryAssistEnabled;
    }

    /// <summary>
    /// Returns <c>true</c> if the company can run an AI Catalog Price Check.
    /// The company-level <c>AiCatalogPriceCheckEnabled</c> flag is checked first as an
    /// explicit SuperAdmin override — enabling it grants access regardless of plan tier,
    /// useful for granting individual companies on lower plans. If the override is not set,
    /// access falls back to the plan-level <c>AllowAiCatalogPriceCheck</c> flag.
    /// Comped companies bypass all gates.
    /// </summary>
    public async Task<bool> CanUseAiCatalogPriceCheckAsync(int companyId)
    {
        var (company, config) = await GetCompanyAndConfigAsync(companyId);
        if (company == null) return false;
        if (company.IsComped) return true;

        // Company toggle is an explicit override — grants access regardless of plan
        if (company.AiCatalogPriceCheckEnabled) return true;

        // Fall back to plan-level gate
        return config != null && config.AllowAiCatalogPriceCheck;
    }

    public async Task<bool> CanUseAiPhotoQuoteAsync(int companyId)
    {
        var (company, config) = await GetCompanyAndConfigAsync(companyId);
        if (company == null) return false;
        if (company.IsComped) return true;

        // Plan-level gate: feature must be enabled on the plan
        if (config != null && !config.AllowAiPhotoQuotes) return false;

        // Company-level override: SuperAdmin can disable per company
        if (!company.AiPhotoQuotesEnabled) return false;

        var (used, max) = await GetAiPhotoQuoteUsageAsync(companyId);
        return max == AppConstants.SubscriptionConstants.UnlimitedValue || used < max;
    }

    /// <summary>
    /// Returns the number of AI photo quote analyses used this calendar month and the
    /// monthly cap.  Usage is measured against <see cref="AiItemPrediction"/> rows because
    /// each prediction corresponds to one Claude API call with an uploaded photo.
    /// The per-company override (<c>MaxAiPhotoQuotesPerMonthOverride</c>) takes precedence
    /// over the plan config value; -1 means unlimited.
    /// Returns (0, 0) when the company does not exist, which causes <see cref="CanUseAiPhotoQuoteAsync"/>
    /// to return <c>false</c> safely.
    /// </summary>
    public async Task<(int Used, int Max)> GetAiPhotoQuoteUsageAsync(int companyId)
    {
        var (company, config) = await GetCompanyAndConfigAsync(companyId);
        if (company == null) return (0, 0);
        if (company.IsComped) return (0, AppConstants.SubscriptionConstants.UnlimitedValue);

        var startOfMonth = new DateTime(DateTime.UtcNow.Year, DateTime.UtcNow.Month, 1, 0, 0, 0, DateTimeKind.Utc);
        var used = await _context.AiItemPredictions
            .IgnoreQueryFilters()
            .Where(p => p.CompanyId == companyId && p.CreatedAt >= startOfMonth && !p.IsDeleted)
            .CountAsync();

        var max = company.MaxAiPhotoQuotesPerMonthOverride ?? config?.MaxAiPhotoQuotesPerMonth ?? -1;
        return (used, max);
    }

    /// <summary>
    /// Shared helper that loads the <see cref="Company"/> record and its associated
    /// <see cref="SubscriptionPlanConfig"/> in two queries.  Both queries use
    /// <c>ignoreQueryFilters: true</c> so that inactive or soft-deleted companies can still
    /// have their subscription status evaluated (e.g., by middleware during login).
    /// Returns <c>(null, null)</c> when the company does not exist; callers are expected
    /// to handle this as a worst-case "no access" state.
    /// </summary>
    private async Task<(Company? company, SubscriptionPlanConfig? config)> GetCompanyAndConfigAsync(int companyId)
    {
        var company = await _unitOfWork.Companies.GetByIdAsync(companyId, ignoreQueryFilters: true);
        if (company == null) return (null, null);

        var config = await _unitOfWork.SubscriptionPlanConfigs.FirstOrDefaultAsync(
            c => c.Plan == company.SubscriptionPlan && c.IsActive,
            ignoreQueryFilters: true);

        return (company, config);
    }
}