using Data.SeaHavenIndustries;
using Data.SeaHavenIndustries.Enums;
using Microsoft.EntityFrameworkCore;
using SeaHaven.DataServices.Interfaces;
using SeaHaven.DataServices.Models;

namespace SeaHaven.DataServices.Implementation
{
    public class VendorCompanyRosterDataService : IVendorCompanyRosterDataService
    {
        private static readonly string[] TerminalLegacyStatuses = { "completed", "cancelled", "canceled" };

        private readonly ApplicationDbContext _context;

        public VendorCompanyRosterDataService(ApplicationDbContext context)
        {
            _context = context;
        }

        public Task<bool> IsActiveAreaAsync(int areaId, CancellationToken cancellationToken) =>
            _context.Areas
                .AsNoTracking()
                .AnyAsync(area => area.Id == areaId && area.IsActive, cancellationToken);

        public async Task<VendorCompanyRosterReadModel?> GetRosterAsync(
            int? vendorId,
            int? companyId,
            CancellationToken cancellationToken)
        {
            int? resolvedCompanyId = companyId;

            if (vendorId.HasValue)
            {
                var vendorCompanyId = await _context.Vendors
                    .AsNoTracking()
                    .Where(v => v.Id == vendorId.Value && (v.IsDeleted == null || v.IsDeleted == false))
                    .Select(v => v.CompanyId)
                    .FirstOrDefaultAsync(cancellationToken);

                if (!vendorCompanyId.HasValue ||
                    (companyId.HasValue && vendorCompanyId.Value != companyId.Value))
                    return null;

                resolvedCompanyId = vendorCompanyId;
            }

            if (!resolvedCompanyId.HasValue)
                return null;

            var company = await _context.VendorCompanies
                .AsNoTracking()
                .Where(c => c.Id == resolvedCompanyId.Value)
                .Select(c => new VendorCompanyRosterReadModel
                {
                    CompanyId = c.Id,
                    Name = c.Name,
                    CompanyPhone = c.CompanyPhone,
                    Email = c.Email,
                    Address = c.Address,
                    City = c.City,
                    State = c.State,
                    Zip = c.Zip,
                    GoogleMapsUrl = c.GoogleMapsUrl,
                    Notes = c.Notes,
                    AreaId = c.AreaId,
                    AreaName = c.Area != null ? c.Area.Name : null,
                    RowVersion = c.RowVersion
                })
                .FirstOrDefaultAsync(cancellationToken);

            if (company == null)
                return null;

            var technicians = await _context.Vendors
                .AsNoTracking()
                .Where(v => v.CompanyId == company.CompanyId
                    && (v.IsDeleted == null || v.IsDeleted == false))
                .OrderBy(v => v.Id)
                .Select(v => new VendorRosterTechnicianReadModel
                {
                    Id = v.Id,
                    ContactName = v.ContactName,
                    Phone = v.Phone,
                    Email = v.Email,
                    PreferredContact = v.PreferredContact,
                    TradeSpecialties = v.TradeSpecialties,
                    IsActive = v.IsActive,
                    TotalJobs = v.TotalJobs
                })
                .ToListAsync(cancellationToken);

            company.Technicians = technicians;
            return company;
        }

        public async Task<VendorCompanyRosterReadModel> SaveRosterAsync(
            VendorCompanyRosterWriteModel roster,
            CancellationToken cancellationToken)
        {
            var company = await _context.VendorCompanies
                .FirstOrDefaultAsync(c => c.Id == roster.CompanyId, cancellationToken);

            if (company == null)
                throw new KeyNotFoundException($"Vendor company with ID {roster.CompanyId} not found.");

            // Concurrency: pin the client-supplied row version as the original value so a
            // stale save throws DbUpdateConcurrencyException (mapped to a stable 409).
            if (roster.RowVersion != null && roster.RowVersion.Length > 0)
                _context.Entry(company).Property(c => c.RowVersion).OriginalValue = roster.RowVersion;

            var now = DateTime.UtcNow;
            var trimmedName = roster.Name.Trim();

            company.Name = trimmedName;
            company.NormalizedName = trimmedName.ToLowerInvariant();
            company.CompanyPhone = roster.CompanyPhone;
            company.Email = roster.Email;
            company.Address = roster.Address;
            company.City = roster.City;
            company.State = roster.State;
            company.Zip = roster.Zip;
            company.GoogleMapsUrl = roster.GoogleMapsUrl;
            company.Notes = roster.Notes;
            if (roster.AreaIdProvided)
                company.AreaId = roster.AreaId;
            company.LastModificationTime = now;
            int? actorId = int.TryParse(roster.ActorUserId, out var parsedActorId) ? parsedActorId : null;
            if (actorId.HasValue)
                company.LastModifierUserId = actorId;

            var existingTechnicians = await _context.Vendors
                .Where(v => v.CompanyId == company.Id && (v.IsDeleted == null || v.IsDeleted == false))
                .ToListAsync(cancellationToken);

            var snapshotIds = roster.Technicians
                .Where(t => t.Id.HasValue)
                .Select(t => t.Id!.Value)
                .ToHashSet();

            var toRemove = existingTechnicians
                .Where(e => !snapshotIds.Contains(e.Id))
                .ToList();

            // A technician omitted from the snapshot may only be soft-deleted when it has no
            // open linked work orders; otherwise the whole reconcile fails (nothing saved).
            if (toRemove.Count > 0)
            {
                var blocked = await GetOpenLinkedWorkOrdersAsync(
                    toRemove.Select(vendor => vendor.Id).ToArray(),
                    cancellationToken);

                if (blocked.Count > 0)
                    throw new VendorRosterConflictException(
                        "One or more technicians cannot be removed because they have open linked work orders.",
                        blocked);
            }

            foreach (var removed in toRemove)
            {
                removed.IsActive = false;
                removed.IsDeleted = true;
                removed.DeletionTime = now;
                removed.LastModificationTime = now;
                if (actorId.HasValue)
                    removed.LastModifierUserId = actorId;
            }

            foreach (var technician in roster.Technicians)
            {
                if (technician.Id.HasValue)
                {
                    var existing = existingTechnicians.FirstOrDefault(e => e.Id == technician.Id.Value);
                    if (existing == null)
                        continue;

                    existing.ContactName = technician.ContactName;
                    existing.Phone = technician.Phone;
                    existing.Email = technician.Email;
                    existing.PreferredContact = technician.PreferredContact;
                    existing.TradeSpecialties = technician.TradeSpecialties;
                    existing.IsActive = technician.IsActive;
                    existing.CompanyName = trimmedName;
                    existing.CompanyPhone = company.CompanyPhone;
                    existing.Address = company.Address;
                    existing.City = company.City;
                    existing.State = company.State;
                    existing.Zip = company.Zip;
                    existing.GoogleMapsUrl = company.GoogleMapsUrl;
                    existing.LastModificationTime = now;
                    if (actorId.HasValue)
                        existing.LastModifierUserId = actorId;
                }
                else
                {
                    var vendor = new Vendor
                    {
                        CompanyName = trimmedName,
                        ContactName = technician.ContactName,
                        Phone = technician.Phone,
                        Email = technician.Email,
                        PreferredContact = technician.PreferredContact,
                        TradeSpecialties = technician.TradeSpecialties,
                        IsActive = technician.IsActive,
                        CompanyId = company.Id,
                        CompanyPhone = company.CompanyPhone,
                        Address = company.Address,
                        City = company.City,
                        State = company.State,
                        Zip = company.Zip,
                        GoogleMapsUrl = company.GoogleMapsUrl,
                        CreatedDate = now,
                        createdby = roster.ActorUserId
                    };

                    await _context.Vendors.AddAsync(vendor, cancellationToken);
                }
            }

            await _context.SaveChangesAsync(cancellationToken);

            return await GetRosterAsync(null, company.Id, cancellationToken)
                ?? throw new InvalidOperationException("Roster could not be reloaded after save.");
        }

        public async Task<VendorCompanyRosterReadModel> CreateRosterAsync(
            VendorCompanyRosterWriteModel roster,
            CancellationToken cancellationToken)
        {
            var now = DateTime.UtcNow;
            var trimmedName = roster.Name.Trim();
            var normalizedName = trimmedName.ToLowerInvariant();

            // NormalizedName has an unfiltered unique index, so deleted companies still
            // reserve their names. Detect the ordinary collision before tracking a new
            // aggregate; the save guard below covers the concurrent-create race.
            var nameTaken = await _context.VendorCompanies
                .AnyAsync(company => company.NormalizedName == normalizedName, cancellationToken);

            if (nameTaken)
                throw new VendorRosterDuplicateNameException(
                    "Another vendor company already uses that name.",
                    new InvalidOperationException(
                        $"NormalizedName '{normalizedName}' is already in use."));

            var company = new VendorCompany
            {
                Name = trimmedName,
                NormalizedName = normalizedName,
                CompanyPhone = roster.CompanyPhone,
                Email = roster.Email,
                Address = roster.Address,
                City = roster.City,
                State = roster.State,
                Zip = roster.Zip,
                GoogleMapsUrl = roster.GoogleMapsUrl,
                Notes = roster.Notes,
                AreaId = roster.AreaId,
                CreatedDate = now,
                createdby = roster.ActorUserId
            };

            await _context.VendorCompanies.AddAsync(company, cancellationToken);

            foreach (var technician in roster.Technicians)
            {
                var vendor = new Vendor
                {
                    CompanyName = trimmedName,
                    ContactName = technician.ContactName,
                    Phone = technician.Phone,
                    Email = technician.Email,
                    PreferredContact = technician.PreferredContact,
                    TradeSpecialties = technician.TradeSpecialties,
                    IsActive = technician.IsActive,
                    Company = company,
                    CompanyPhone = company.CompanyPhone,
                    Address = company.Address,
                    City = company.City,
                    State = company.State,
                    Zip = company.Zip,
                    GoogleMapsUrl = company.GoogleMapsUrl,
                    CreatedDate = now,
                    createdby = roster.ActorUserId
                };

                await _context.Vendors.AddAsync(vendor, cancellationToken);
            }

            try
            {
                await _context.SaveChangesAsync(cancellationToken);
            }
            catch (DbUpdateException ex) when (IsUniqueConstraintViolation(ex))
            {
                throw new VendorRosterDuplicateNameException(
                    "Another vendor company already uses that name.",
                    ex);
            }

            return await GetRosterAsync(null, company.Id, cancellationToken)
                ?? throw new InvalidOperationException("Roster could not be reloaded after create.");
        }

        private static bool IsUniqueConstraintViolation(DbUpdateException ex)
        {
            var message = ex.InnerException?.Message ?? ex.Message;
            return message.Contains("duplicate", StringComparison.OrdinalIgnoreCase)
                || message.Contains("UNIQUE", StringComparison.OrdinalIgnoreCase);
        }

        public async Task<VendorCompanyRosterReadModel> AddTechniciansAsync(
            VendorCompanyRosterAddWriteModel roster,
            CancellationToken cancellationToken)
        {
            var company = await _context.VendorCompanies
                .FirstOrDefaultAsync(c => c.Id == roster.CompanyId, cancellationToken);

            if (company == null)
                throw new KeyNotFoundException($"Vendor company with ID {roster.CompanyId} not found.");

            // Concurrency: pin the client-supplied row version as the original value so a
            // stale save throws DbUpdateConcurrencyException (mapped to a stable 409).
            if (roster.RowVersion != null && roster.RowVersion.Length > 0)
                _context.Entry(company).Property(c => c.RowVersion).OriginalValue = roster.RowVersion;

            var now = DateTime.UtcNow;
            int? actorId = int.TryParse(roster.ActorUserId, out var parsedActorId) ? parsedActorId : null;
            string? renamedTo = null;

            // Partial company update: only fields present in CompanyFields are applied;
            // a null field leaves the stored value untouched. The company row is always
            // touched so the concurrency token fires on every additive save.
            if (roster.CompanyFields != null)
            {
                var fields = roster.CompanyFields;

                if (fields.Name != null)
                {
                    var trimmedName = fields.Name.Trim();
                    var normalized = trimmedName.ToLowerInvariant();

                    if (normalized != company.NormalizedName)
                    {
                        var nameTaken = await _context.VendorCompanies
                            .AnyAsync(
                                other => other.Id != company.Id
                                    && (other.IsDeleted == null || other.IsDeleted == false)
                                    && other.NormalizedName == normalized,
                                cancellationToken);

                        if (nameTaken)
                            throw new VendorRosterDuplicateNameException(
                                "Another vendor company already uses that name.",
                                new InvalidOperationException(
                                    $"NormalizedName '{normalized}' is already in use."));

                        renamedTo = normalized;
                    }

                    company.Name = trimmedName;
                    company.NormalizedName = normalized;
                }

                if (fields.CompanyPhone != null)
                    company.CompanyPhone = fields.CompanyPhone;
                if (fields.Email != null)
                    company.Email = fields.Email;
                if (fields.Address != null)
                    company.Address = fields.Address;
                if (fields.City != null)
                    company.City = fields.City;
                if (fields.State != null)
                    company.State = fields.State;
                if (fields.Zip != null)
                    company.Zip = fields.Zip;
                if (fields.GoogleMapsUrl != null)
                    company.GoogleMapsUrl = fields.GoogleMapsUrl;
                if (fields.Notes != null)
                    company.Notes = fields.Notes;
                if (fields.AreaIdProvided)
                    company.AreaId = fields.AreaId;

                // Keep the denormalized company columns on existing technicians aligned
                // with the company row (same invariant SaveRosterAsync maintains). This
                // never removes, deactivates or rewrites technician-owned fields.
                var existingTechnicians = await _context.Vendors
                    .Where(v => v.CompanyId == company.Id && (v.IsDeleted == null || v.IsDeleted == false))
                    .ToListAsync(cancellationToken);

                foreach (var existing in existingTechnicians)
                {
                    existing.CompanyName = company.Name;
                    existing.CompanyPhone = company.CompanyPhone;
                    existing.Address = company.Address;
                    existing.City = company.City;
                    existing.State = company.State;
                    existing.Zip = company.Zip;
                    existing.GoogleMapsUrl = company.GoogleMapsUrl;
                    existing.LastModificationTime = now;
                    if (actorId.HasValue)
                        existing.LastModifierUserId = actorId;
                }
            }

            company.LastModificationTime = now;
            if (actorId.HasValue)
                company.LastModifierUserId = actorId;

            // Purely additive: every submitted technician is a new row. Existing
            // technicians are deliberately not consulted for removal.
            foreach (var technician in roster.AddTechnicians)
            {
                var vendor = new Vendor
                {
                    CompanyName = company.Name,
                    ContactName = technician.ContactName,
                    Phone = technician.Phone,
                    Email = technician.Email,
                    PreferredContact = technician.PreferredContact,
                    TradeSpecialties = technician.TradeSpecialties,
                    IsActive = technician.IsActive,
                    CompanyId = company.Id,
                    CompanyPhone = company.CompanyPhone,
                    Address = company.Address,
                    City = company.City,
                    State = company.State,
                    Zip = company.Zip,
                    GoogleMapsUrl = company.GoogleMapsUrl,
                    CreatedDate = now,
                    createdby = roster.ActorUserId
                };

                await _context.Vendors.AddAsync(vendor, cancellationToken);
            }

            // SH-250: a rename can collide with the unique NormalizedName index. Without
            // this guard the DbUpdateException reached the controller's generic handler
            // and surfaced as a 500, even though SQL Server rolls the batch back cleanly.
            // The pre-check above handles the ordinary case; this covers the race where a
            // competing rename commits between that check and this save.
            try
            {
                await _context.SaveChangesAsync(cancellationToken);
            }
            catch (DbUpdateException ex) when (renamedTo != null && ex is not DbUpdateConcurrencyException)
            {
                throw new VendorRosterDuplicateNameException(
                    "Another vendor company already uses that name.",
                    ex);
            }

            return await GetRosterAsync(null, company.Id, cancellationToken)
                ?? throw new InvalidOperationException("Roster could not be reloaded after save.");
        }

        private async Task<List<LinkedWorkOrderInfo>> GetOpenLinkedWorkOrdersAsync(
            IReadOnlyCollection<int> vendorIds,
            CancellationToken cancellationToken)
        {
            var directLinks = _context.Dispatches
                .Where(d => vendorIds.Contains(d.VendorId) && d.WorkOrderId.HasValue)
                .Select(d => new { DispatchId = d.Id, WorkOrderId = d.WorkOrderId!.Value });

            var multiLinks = _context.DispatchWorkOrders
                .Where(link => link.Dispatch != null && vendorIds.Contains(link.Dispatch.VendorId))
                .Select(link => new { DispatchId = link.DispatchId, WorkOrderId = link.WorkOrderId });

            var linkedIds = await directLinks
                .Concat(multiLinks)
                .Join(_context.workOrders,
                    link => link.WorkOrderId,
                    wo => wo.Id,
                    (link, wo) => new LinkedWorkOrderInfo
                    {
                        WorkOrderId = wo.Id,
                        WorkOrderNumber = wo.WorkerOrderNumber,
                        WorkOrderTitle = wo.WorkerOrderTitle,
                        Status = wo.Status,
                        LifecycleStatus = wo.LifecycleStatus,
                        ScheduledDate = wo.ScheduledDate,
                        DispatchId = link.DispatchId
                    })
                .OrderBy(wo => wo.WorkOrderId)
                .ToListAsync(cancellationToken);

            return linkedIds
                .Where(wo => !IsTerminalWorkOrderStatus(wo.LifecycleStatus, wo.Status))
                .DistinctBy(x => x.WorkOrderId)
                .ToList();
        }

        private static bool IsTerminalWorkOrderStatus(LifecycleStatus? lifecycleStatus, string? legacyStatus)
        {
            if (lifecycleStatus == LifecycleStatus.Completed || lifecycleStatus == LifecycleStatus.Canceled)
                return true;

            if (!string.IsNullOrWhiteSpace(legacyStatus) &&
                TerminalLegacyStatuses.Contains(legacyStatus.Trim().ToLowerInvariant()))
                return true;

            return false;
        }
    }
}