using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.EntityFrameworkCore;
using PowderCoating.Core.Entities;
using PowderCoating.Core.Enums;
using PowderCoating.Core.Interfaces;
using PowderCoating.Shared.Constants;
using PowderCoating.Web.BackgroundServices;
using System.Text.Json;

namespace PowderCoating.Web.Controllers;

/// <summary>
/// Manages recurring transaction templates. Each template is a saved recipe that the
/// <see cref="RecurringTransactionService"/> uses to auto-generate bills or expenses on a schedule.
/// Bills are created as Draft for user review; Expenses are recorded immediately.
/// </summary>
[Authorize(Policy = AppConstants.Policies.CompanyAdminOnly)]
public class RecurringTemplatesController : Controller
{
    private readonly IUnitOfWork _unitOfWork;
    private readonly ITenantContext _tenantContext;
    private readonly UserManager<ApplicationUser> _userManager;
    private readonly ILogger<RecurringTemplatesController> _logger;

    public RecurringTemplatesController(
        IUnitOfWork unitOfWork,
        ITenantContext tenantContext,
        UserManager<ApplicationUser> userManager,
        ILogger<RecurringTemplatesController> logger)
    {
        _unitOfWork = unitOfWork;
        _tenantContext = tenantContext;
        _userManager = userManager;
        _logger = logger;
    }

    // -------------------------------------------------------------------------
    // Index
    // -------------------------------------------------------------------------

    /// <summary>Lists all recurring templates for the current company, active first then by name.</summary>
    public async Task<IActionResult> Index()
    {
        var companyId = _tenantContext.GetCurrentCompanyId() ?? 0;
        var templates = await _unitOfWork.RecurringTemplates.FindAsync(t => t.CompanyId == companyId);
        return View(templates.OrderByDescending(t => t.IsActive).ThenBy(t => t.Name).ToList());
    }

    // -------------------------------------------------------------------------
    // Create
    // -------------------------------------------------------------------------

    [HttpGet]
    public async Task<IActionResult> Create()
    {
        await PopulateDropDownsAsync();
        return View(new RecurringTemplateViewModel { StartDate = DateTime.Today.AddDays(1) });
    }

    /// <summary>
    /// Saves a new recurring template. Serializes the type-specific fields to JSON in TemplateData.
    /// </summary>
    [HttpPost]
    [ValidateAntiForgeryToken]
    public async Task<IActionResult> Create(RecurringTemplateViewModel vm)
    {
        if (!ModelState.IsValid) { await PopulateDropDownsAsync(); return View(vm); }

        var user = await _userManager.GetUserAsync(User);
        var companyId = _tenantContext.GetCurrentCompanyId() ?? 0;

        var template = new RecurringTemplate
        {
            Name          = vm.Name,
            TemplateType  = vm.TemplateType,
            Frequency     = vm.Frequency,
            IntervalCount = Math.Max(1, vm.IntervalCount),
            NextFireDate  = vm.StartDate.Date,
            EndDate       = vm.EndDate?.Date,
            MaxOccurrences = vm.MaxOccurrences > 0 ? vm.MaxOccurrences : null,
            IsActive      = true,
            TemplateData  = BuildTemplateJson(vm),
            CompanyId     = companyId,
            CreatedBy     = user?.Email
        };

        await _unitOfWork.RecurringTemplates.AddAsync(template);
        await _unitOfWork.CompleteAsync();

        TempData["Success"] = $"Recurring template \"{template.Name}\" created.";
        return RedirectToAction(nameof(Index));
    }

    // -------------------------------------------------------------------------
    // Edit
    // -------------------------------------------------------------------------

    [HttpGet]
    public async Task<IActionResult> Edit(int id)
    {
        var template = await _unitOfWork.RecurringTemplates.GetByIdAsync(id);
        if (template == null) return NotFound();

        await PopulateDropDownsAsync();
        return View(ToViewModel(template));
    }

    /// <summary>
    /// Updates a recurring template. Re-serializes TemplateData from form values.
    /// NextFireDate is not touched here — only StartDate on first save drives it.
    /// </summary>
    [HttpPost]
    [ValidateAntiForgeryToken]
    public async Task<IActionResult> Edit(int id, RecurringTemplateViewModel vm)
    {
        if (id != vm.Id) return BadRequest();
        if (!ModelState.IsValid) { await PopulateDropDownsAsync(); return View(vm); }

        var template = await _unitOfWork.RecurringTemplates.GetByIdAsync(id);
        if (template == null) return NotFound();

        template.Name          = vm.Name;
        template.TemplateType  = vm.TemplateType;
        template.Frequency     = vm.Frequency;
        template.IntervalCount = Math.Max(1, vm.IntervalCount);
        template.EndDate       = vm.EndDate?.Date;
        template.MaxOccurrences = vm.MaxOccurrences > 0 ? vm.MaxOccurrences : null;
        template.TemplateData  = BuildTemplateJson(vm);

        await _unitOfWork.CompleteAsync();

        TempData["Success"] = $"Recurring template \"{template.Name}\" updated.";
        return RedirectToAction(nameof(Index));
    }

    // -------------------------------------------------------------------------
    // ToggleActive / Delete / GenerateNow
    // -------------------------------------------------------------------------

    /// <summary>Pauses or resumes a recurring template.</summary>
    [HttpPost]
    [ValidateAntiForgeryToken]
    public async Task<IActionResult> ToggleActive(int id)
    {
        var template = await _unitOfWork.RecurringTemplates.GetByIdAsync(id);
        if (template == null) return NotFound();

        template.IsActive = !template.IsActive;
        await _unitOfWork.CompleteAsync();

        TempData["Success"] = $"Template \"{template.Name}\" is now {(template.IsActive ? "active" : "paused")}.";
        return RedirectToAction(nameof(Index));
    }

    /// <summary>Soft-deletes a recurring template.</summary>
    [HttpPost]
    [ValidateAntiForgeryToken]
    public async Task<IActionResult> Delete(int id)
    {
        var template = await _unitOfWork.RecurringTemplates.GetByIdAsync(id);
        if (template == null) return NotFound();

        var name = template.Name;
        await _unitOfWork.RecurringTemplates.SoftDeleteAsync(id);
        await _unitOfWork.CompleteAsync();

        TempData["Success"] = $"Template \"{name}\" deleted.";
        return RedirectToAction(nameof(Index));
    }

    /// <summary>
    /// Forces immediate generation of the next occurrence and advances NextFireDate,
    /// regardless of the scheduled date. Useful for testing a new template or catching up
    /// after a configuration change.
    /// <para>
    /// INTENTIONAL EXCEPTION to the no-DbContext-in-controllers rule: this action must
    /// execute the same multi-step entity creation that <see cref="RecurringTransactionService"/>
    /// does in a background scope. Creating an inner DI scope here avoids duplicating that
    /// service's interface (which would require exposing a public synchronous Fire method on a
    /// singleton BackgroundService, which is unsafe). The scope is disposed after the action
    /// completes, so no DbContext leak occurs. This pattern mirrors how BackgroundService
    /// itself resolves scoped services.
    /// </para>
    /// </summary>
    [HttpPost]
    [ValidateAntiForgeryToken]
    public async Task<IActionResult> GenerateNow(int id)
    {
        var template = await _unitOfWork.RecurringTemplates.GetByIdAsync(id);
        if (template == null) return NotFound();

        try
        {
            // Intentional: create a fresh DI scope so the inner DbContext is isolated from the
            // request's IUnitOfWork context. See summary above for rationale.
            using var scope = HttpContext.RequestServices.CreateScope();
            var db = scope.ServiceProvider.GetRequiredService<PowderCoating.Infrastructure.Data.ApplicationDbContext>();

            // Reload the tracked entity from this scope's DbContext
            var tracked = await db.RecurringTemplates.FindAsync(template.Id);
            if (tracked == null) return NotFound();

            var svc = new RecurringTransactionService(null!, _logger as ILogger<RecurringTransactionService>
                ?? Microsoft.Extensions.Logging.Abstractions.NullLogger<RecurringTransactionService>.Instance);

            // Use reflection-free approach: call directly via internal method pattern
            await FireTemplateSynchronouslyAsync(db, tracked);

            TempData["Success"] = $"Template \"{template.Name}\" generated on demand. Next fire: {tracked.NextFireDate:MM/dd/yyyy}.";
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "GenerateNow failed for template {Id}.", id);
            TempData["Error"] = $"Generation failed: {ex.Message}";
        }

        return RedirectToAction(nameof(Index));
    }

    // -------------------------------------------------------------------------
    // Helpers
    // -------------------------------------------------------------------------

    /// <summary>
    /// Inline implementation of the fire logic so GenerateNow doesn't need to instantiate
    /// the BackgroundService (which has a singleton scope that may not be accessible here).
    /// </summary>
    private static async Task FireTemplateSynchronouslyAsync(
        PowderCoating.Infrastructure.Data.ApplicationDbContext db,
        RecurringTemplate template)
    {
        if (template.TemplateType == RecurringTemplateType.Bill)
        {
            var data = JsonSerializer.Deserialize<RecurringTransactionService.BillTemplateData>(template.TemplateData)
                       ?? throw new InvalidOperationException("Invalid bill template data.");

            var prefix = $"BILL-{DateTime.Now:yyMM}-";
            var lastBill = await db.Bills
                .IgnoreQueryFilters()
                .Where(b => b.BillNumber.StartsWith(prefix))
                .OrderByDescending(b => b.BillNumber)
                .Select(b => b.BillNumber)
                .FirstOrDefaultAsync();
            int nextN = 1;
            if (lastBill != null && int.TryParse(lastBill[prefix.Length..], out int ln)) nextN = ln + 1;

            var bill = new Bill
            {
                BillNumber   = $"{prefix}{nextN:D4}",
                VendorId     = data.VendorId,
                APAccountId  = data.APAccountId,
                BillDate     = DateTime.UtcNow,
                Status       = BillStatus.Draft,
                Terms        = data.Terms,
                Memo         = $"[Recurring] {data.Memo}".Trim(),
                SubTotal     = data.LineItems?.Sum(l => l.Quantity * l.UnitPrice) ?? 0,
                TaxPercent   = data.TaxPercent,
                CompanyId    = template.CompanyId,
                CreatedBy    = "Recurring (on-demand)",
                CreatedAt    = DateTime.UtcNow
            };
            bill.TaxAmount = Math.Round(bill.SubTotal * bill.TaxPercent / 100, 2);
            bill.Total     = bill.SubTotal + bill.TaxAmount;
            db.Bills.Add(bill);
            await db.SaveChangesAsync();

            int order = 1;
            foreach (var line in data.LineItems ?? [])
            {
                db.BillLineItems.Add(new BillLineItem
                {
                    BillId      = bill.Id,
                    AccountId   = line.AccountId,
                    Description = line.Description,
                    Quantity    = line.Quantity,
                    UnitPrice   = line.UnitPrice,
                    Amount      = Math.Round(line.Quantity * line.UnitPrice, 2),
                    DisplayOrder = order++,
                    CompanyId   = template.CompanyId,
                    CreatedAt   = DateTime.UtcNow
                });
            }
        }
        else
        {
            var data = JsonSerializer.Deserialize<RecurringTransactionService.ExpenseTemplateData>(template.TemplateData)
                       ?? throw new InvalidOperationException("Invalid expense template data.");

            var prefix = $"EXP-{DateTime.Now:yyMM}-";
            var lastExp = await db.Expenses
                .IgnoreQueryFilters()
                .Where(e => e.ExpenseNumber.StartsWith(prefix))
                .OrderByDescending(e => e.ExpenseNumber)
                .Select(e => e.ExpenseNumber)
                .FirstOrDefaultAsync();
            int nextN = 1;
            if (lastExp != null && int.TryParse(lastExp[prefix.Length..], out int ln)) nextN = ln + 1;

            db.Expenses.Add(new Expense
            {
                ExpenseNumber    = $"{prefix}{nextN:D4}",
                Date             = DateTime.UtcNow,
                VendorId         = data.VendorId == 0 ? null : data.VendorId,
                ExpenseAccountId = data.ExpenseAccountId,
                PaymentAccountId = data.PaymentAccountId,
                PaymentMethod    = (PaymentMethod)data.PaymentMethod,
                Amount           = data.Amount,
                Memo             = $"[Recurring] {data.Memo}".Trim(),
                CompanyId        = template.CompanyId,
                CreatedBy        = "Recurring (on-demand)",
                CreatedAt        = DateTime.UtcNow
            });
        }

        template.OccurrenceCount++;
        template.NextFireDate = AdvanceDate(template.NextFireDate, template.Frequency, template.IntervalCount);
        template.LastError = null;

        if (template.MaxOccurrences.HasValue && template.OccurrenceCount >= template.MaxOccurrences.Value)
            template.IsActive = false;
        else if (template.EndDate.HasValue && template.NextFireDate.Date > template.EndDate.Value.Date)
            template.IsActive = false;

        await db.SaveChangesAsync();
    }

    private static DateTime AdvanceDate(DateTime date, RecurringFrequency freq, int interval) => freq switch
    {
        RecurringFrequency.Daily     => date.AddDays(interval),
        RecurringFrequency.Weekly    => date.AddDays(7 * interval),
        RecurringFrequency.BiWeekly  => date.AddDays(14 * interval),
        RecurringFrequency.Monthly   => date.AddMonths(interval),
        RecurringFrequency.Quarterly => date.AddMonths(3 * interval),
        RecurringFrequency.Annually  => date.AddYears(interval),
        _                            => date.AddMonths(interval)
    };

    /// <summary>
    /// Serializes type-specific form fields to the TemplateData JSON blob.
    /// Only bill or expense fields are included — unused type's fields are discarded.
    /// </summary>
    private static string BuildTemplateJson(RecurringTemplateViewModel vm)
    {
        if (vm.TemplateType == RecurringTemplateType.Bill)
        {
            var data = new RecurringTransactionService.BillTemplateData(
                VendorId:   vm.BillVendorId ?? 0,
                APAccountId: vm.APAccountId ?? 0,
                Terms:      vm.BillTerms,
                Memo:       vm.BillMemo,
                TaxPercent: vm.BillTaxPercent,
                LineItems:  vm.LineItems.Select(l => new RecurringTransactionService.BillLineData(
                    AccountId:   l.AccountId,
                    Description: l.Description ?? string.Empty,
                    Quantity:    l.Quantity == 0 ? 1 : l.Quantity,
                    UnitPrice:   l.UnitPrice)).ToList());
            return JsonSerializer.Serialize(data);
        }
        else
        {
            var data = new RecurringTransactionService.ExpenseTemplateData(
                VendorId:         vm.ExpenseVendorId ?? 0,
                ExpenseAccountId: vm.ExpenseAccountId ?? 0,
                PaymentAccountId: vm.PaymentAccountId ?? 0,
                PaymentMethod:    (int)(vm.ExpensePaymentMethod ?? PaymentMethod.Cash),
                Amount:           vm.ExpenseAmount,
                Memo:             vm.ExpenseMemo);
            return JsonSerializer.Serialize(data);
        }
    }

    /// <summary>Converts a saved <see cref="RecurringTemplate"/> entity back to the form ViewModel.</summary>
    private static RecurringTemplateViewModel ToViewModel(RecurringTemplate t)
    {
        var vm = new RecurringTemplateViewModel
        {
            Id            = t.Id,
            Name          = t.Name,
            TemplateType  = t.TemplateType,
            Frequency     = t.Frequency,
            IntervalCount = t.IntervalCount,
            StartDate     = t.NextFireDate,
            EndDate       = t.EndDate,
            MaxOccurrences = t.MaxOccurrences
        };

        if (t.TemplateType == RecurringTemplateType.Bill)
        {
            var data = JsonSerializer.Deserialize<RecurringTransactionService.BillTemplateData>(t.TemplateData);
            if (data != null)
            {
                vm.BillVendorId  = data.VendorId;
                vm.APAccountId   = data.APAccountId;
                vm.BillTerms     = data.Terms;
                vm.BillMemo      = data.Memo;
                vm.BillTaxPercent = data.TaxPercent;
                vm.LineItems      = (data.LineItems ?? []).Select(l => new LineItemInput
                {
                    AccountId   = l.AccountId,
                    Description = l.Description,
                    Quantity    = l.Quantity,
                    UnitPrice   = l.UnitPrice
                }).ToList();
            }
        }
        else
        {
            var data = JsonSerializer.Deserialize<RecurringTransactionService.ExpenseTemplateData>(t.TemplateData);
            if (data != null)
            {
                vm.ExpenseVendorId      = data.VendorId == 0 ? null : data.VendorId;
                vm.ExpenseAccountId     = data.ExpenseAccountId;
                vm.PaymentAccountId     = data.PaymentAccountId;
                vm.ExpensePaymentMethod = (PaymentMethod)data.PaymentMethod;
                vm.ExpenseAmount        = data.Amount;
                vm.ExpenseMemo          = data.Memo;
            }
        }

        return vm;
    }

    /// <summary>Loads dropdowns for vendors, accounts, and payment methods into ViewBag.</summary>
    private async Task PopulateDropDownsAsync()
    {
        var companyId = _tenantContext.GetCurrentCompanyId() ?? 0;
        var vendors = await _unitOfWork.Vendors.FindAsync(v => v.CompanyId == companyId);
        ViewBag.Vendors = vendors.OrderBy(v => v.CompanyName)
            .Select(v => new SelectListItem(v.CompanyName, v.Id.ToString())).ToList();

        var accounts = await _unitOfWork.Accounts.FindAsync(a => a.CompanyId == companyId);
        ViewBag.APAccounts = accounts
            .Where(a => a.AccountSubType == AccountSubType.AccountsPayable)
            .OrderBy(a => a.AccountNumber)
            .Select(a => new SelectListItem($"{a.AccountNumber} - {a.Name}", a.Id.ToString())).ToList();

        ViewBag.ExpenseAccounts = accounts
            .Where(a => a.AccountType is AccountType.Expense or AccountType.CostOfGoods)
            .OrderBy(a => a.AccountNumber)
            .Select(a => new SelectListItem($"{a.AccountNumber} - {a.Name}", a.Id.ToString())).ToList();

        ViewBag.BankAccounts = accounts
            .Where(a => a.AccountSubType is AccountSubType.Checking or AccountSubType.Savings
                                         or AccountSubType.Cash or AccountSubType.CreditCard)
            .OrderBy(a => a.AccountNumber)
            .Select(a => new SelectListItem($"{a.AccountNumber} - {a.Name}", a.Id.ToString())).ToList();

        ViewBag.AllExpenseAccounts = accounts
            .Where(a => a.AccountType is AccountType.Expense or AccountType.CostOfGoods or AccountType.Asset)
            .OrderBy(a => a.AccountNumber)
            .Select(a => new SelectListItem($"{a.AccountNumber} - {a.Name}", a.Id.ToString())).ToList();

        ViewBag.PaymentMethods = Enum.GetValues<PaymentMethod>()
            .Select(m => new SelectListItem(m.ToString(), ((int)m).ToString())).ToList();
    }
}

// -------------------------------------------------------------------------
// ViewModel
// -------------------------------------------------------------------------

/// <summary>Flat form model for Create and Edit. Type-specific sections are shown/hidden by JS.</summary>
public class RecurringTemplateViewModel
{
    public int Id { get; set; }

    [System.ComponentModel.DataAnnotations.Required]
    public string Name { get; set; } = string.Empty;

    public RecurringTemplateType TemplateType { get; set; } = RecurringTemplateType.Bill;
    public RecurringFrequency Frequency { get; set; } = RecurringFrequency.Monthly;
    public int IntervalCount { get; set; } = 1;
    public DateTime StartDate { get; set; } = DateTime.Today.AddDays(1);
    public DateTime? EndDate { get; set; }
    public int? MaxOccurrences { get; set; }

    // Bill-specific
    public int? BillVendorId { get; set; }
    public int? APAccountId { get; set; }
    public string? BillTerms { get; set; }
    public string? BillMemo { get; set; }
    public decimal BillTaxPercent { get; set; }
    public List<LineItemInput> LineItems { get; set; } = [new()];

    // Expense-specific
    public int? ExpenseVendorId { get; set; }
    public int? ExpenseAccountId { get; set; }
    public int? PaymentAccountId { get; set; }
    public PaymentMethod? ExpensePaymentMethod { get; set; } = PaymentMethod.Cash;
    public decimal ExpenseAmount { get; set; }
    public string? ExpenseMemo { get; set; }
}

/// <summary>A single bill line item in the recurring template form.</summary>
public class LineItemInput
{
    public int? AccountId { get; set; }
    public string? Description { get; set; }
    public decimal Quantity { get; set; } = 1;
    public decimal UnitPrice { get; set; }
}