using FluentValidation;
using FluentValidation.Results;
using SeaHaven.DataServices.Interfaces;
using SeaHaven.DataServices.Models;
using SeaHaven.Services.DTOs;
using SeaHaven.Services.Helpers;
using SeaHaven.Services.Interfaces;
using SeaHaven.Services.Validation;

namespace SeaHaven.Services.Implementation
{
    public class VendorCompanyRosterService : IVendorCompanyRosterService
    {
        private const int MaxNotesLength = 500;
        private const string NotesMaxLengthMessage = "Notes cannot exceed 500 characters.";

        private readonly IVendorCompanyRosterDataService _rosterDataService;

        public VendorCompanyRosterService(IVendorCompanyRosterDataService rosterDataService)
        {
            _rosterDataService = rosterDataService;
        }

        public async Task<VendorRosterDTO?> GetRosterAsync(
            int? vendorId,
            int? companyId,
            string userId,
            CancellationToken cancellationToken)
        {
            EnsureAuthenticated(userId);

            if (!vendorId.HasValue && !companyId.HasValue)
                throw new ValidationException("A vendor id or company id is required.");

            var roster = await _rosterDataService.GetRosterAsync(vendorId, companyId, cancellationToken);
            return roster == null ? null : MapToDTO(roster);
        }

        public async Task<VendorRosterDTO> CreateRosterAsync(
            CreateVendorRosterDTO dto,
            string userId,
            CancellationToken cancellationToken)
        {
            EnsureAuthenticated(userId);
            dto.Technicians ??= new List<RosterTechnicianInputDTO>();
            NormalizeAndValidateCompanyFields(
                dto.Name,
                dto.CompanyPhone,
                dto.Email,
                dto.GoogleMapsUrl,
                dto.Notes,
                nameof(CreateVendorRosterDTO.Notes),
                dto.Technicians);

            if (dto.Technicians.Any(technician => technician.Id.HasValue))
                throw new ValidationException(new[]
                {
                    new ValidationFailure(
                        nameof(CreateVendorRosterDTO.Technicians),
                        "Technician ids are not allowed when creating a vendor company.")
                });

            var writeModel = new VendorCompanyRosterWriteModel
            {
                Name = dto.Name,
                CompanyPhone = VendorPhoneNormalizer.NormalizeToCanonical(dto.CompanyPhone),
                Email = dto.Email,
                Address = dto.Address,
                City = dto.City,
                State = dto.State,
                Zip = dto.Zip,
                GoogleMapsUrl = dto.GoogleMapsUrl,
                Notes = dto.Notes,
                ActorUserId = userId,
                Technicians = MapTechnicians(dto.Technicians)
            };

            var saved = await _rosterDataService.CreateRosterAsync(writeModel, cancellationToken);
            return MapToDTO(saved);
        }

        public async Task<VendorRosterDTO> ReconcileRosterAsync(
            int companyId,
            ReconcileVendorRosterDTO dto,
            string userId,
            CancellationToken cancellationToken)
        {
            EnsureAuthenticated(userId);
            dto.Technicians ??= new List<RosterTechnicianInputDTO>();
            NormalizeAndValidateCompanyFields(
                dto.Name,
                dto.CompanyPhone,
                dto.Email,
                dto.GoogleMapsUrl,
                dto.Notes,
                nameof(ReconcileVendorRosterDTO.Notes),
                dto.Technicians);

            byte[] rowVersion = ParseRequiredRowVersion(dto.RowVersion);

            // Mismatched ids: every non-null technician id must belong to this company.
            await EnsureTechnicianIdsBelongToCompanyAsync(companyId, dto.Technicians, cancellationToken);

            var writeModel = new VendorCompanyRosterWriteModel
            {
                CompanyId = companyId,
                RowVersion = rowVersion,
                Name = dto.Name,
                CompanyPhone = VendorPhoneNormalizer.NormalizeToCanonical(dto.CompanyPhone),
                Email = dto.Email,
                Address = dto.Address,
                City = dto.City,
                State = dto.State,
                Zip = dto.Zip,
                GoogleMapsUrl = dto.GoogleMapsUrl,
                Notes = dto.Notes,
                ActorUserId = userId,
                Technicians = MapTechnicians(dto.Technicians)
            };

            var saved = await _rosterDataService.SaveRosterAsync(writeModel, cancellationToken);
            return MapToDTO(saved);
        }

        public async Task<VendorRosterDTO> AddTechniciansAsync(
            int companyId,
            AddTechniciansVendorRosterDTO dto,
            string userId,
            CancellationToken cancellationToken)
        {
            EnsureAuthenticated(userId);
            dto.AddTechnicians ??= new List<RosterTechnicianInputDTO>();

            byte[] rowVersion = ParseRequiredRowVersion(dto.RowVersion);

            var failures = new List<ValidationFailure>();

            // Additive contract (SH-250): added technicians are always new rows, so an
            // id from this or any other company is rejected instead of silently
            // mutating an existing technician.
            if (dto.AddTechnicians.Any(technician => technician.Id.HasValue))
                failures.Add(new ValidationFailure(
                    nameof(AddTechniciansVendorRosterDTO.AddTechnicians),
                    "Technician ids are not allowed when adding technicians."));

            var hasCompanyChange = dto.CompanyFields != null && HasAnyCompanyValue(dto.CompanyFields);
            if (dto.AddTechnicians.Count == 0 && !hasCompanyChange)
                failures.Add(new ValidationFailure(
                    nameof(AddTechniciansVendorRosterDTO.AddTechnicians),
                    "At least one technician to add or a company update is required."));

            NormalizeAndValidateTechnicians(nameof(AddTechniciansVendorRosterDTO.AddTechnicians), dto.AddTechnicians, failures);

            VendorRosterCompanyFieldsWriteModel? companyFields = null;
            if (dto.CompanyFields != null)
            {
                companyFields = ValidateAndMapCompanyFields(dto.CompanyFields, failures);

                // SH-250: blank company fields all map to null ("unchanged"), so an empty
                // or all-blank CompanyFields object carries no company update. Forwarding
                // it as a non-null write model made the data layer bump RowVersion and
                // rewrite every technician's LastModificationTime for a no-op request.
                if (HasNoCompanyChange(companyFields))
                    companyFields = null;
            }

            if (failures.Count > 0)
                throw new ValidationException(failures);

            // The contact-group invariant ("at least one company phone or email") is
            // preserved by construction: blank company fields map to null ("unchanged"),
            // so this endpoint can only set valid phone/email values, never clear them.

            var writeModel = new VendorCompanyRosterAddWriteModel
            {
                CompanyId = companyId,
                RowVersion = rowVersion,
                ActorUserId = userId,
                CompanyFields = companyFields,
                AddTechnicians = MapTechnicians(dto.AddTechnicians)
            };

            var saved = await _rosterDataService.AddTechniciansAsync(writeModel, cancellationToken);
            return MapToDTO(saved);
        }

        private static void EnsureAuthenticated(string userId)
        {
            if (string.IsNullOrWhiteSpace(userId))
                throw new UnauthorizedAccessException("An authenticated user is required.");
        }

        private static void NormalizeAndValidateCompanyFields(
            string name,
            string? companyPhone,
            string? email,
            string? googleMapsUrl,
            string? notes,
            string notesPropertyName,
            List<RosterTechnicianInputDTO> technicians)
        {
            var failures = new List<ValidationFailure>();

            if (string.IsNullOrWhiteSpace(name))
                failures.Add(new ValidationFailure(nameof(CreateVendorRosterDTO.Name), "Company name is required."));

            // Contact group: the company must expose at least one contact channel.
            var normalizedCompanyPhone = VendorPhoneNormalizer.NormalizeToCanonical(companyPhone);
            if (string.IsNullOrWhiteSpace(normalizedCompanyPhone) && string.IsNullOrWhiteSpace(email))
                failures.Add(new ValidationFailure(
                    nameof(CreateVendorRosterDTO.CompanyPhone),
                    "At least one company phone or email is required."));

            if (!string.IsNullOrWhiteSpace(normalizedCompanyPhone) &&
                !VendorPhoneNormalizer.NorthAmericanPhoneRegex.IsMatch(normalizedCompanyPhone))
                failures.Add(new ValidationFailure(
                    nameof(CreateVendorRosterDTO.CompanyPhone),
                    "Company phone must be in North American format: (XXX) XXX-XXXX"));

            if (!string.IsNullOrWhiteSpace(email) && !BeValidEmail(email))
                failures.Add(new ValidationFailure(nameof(CreateVendorRosterDTO.Email), "Invalid email address."));

            if (!string.IsNullOrWhiteSpace(googleMapsUrl) && !BeValidAbsoluteHttpsUrl(googleMapsUrl))
                failures.Add(new ValidationFailure(
                    nameof(CreateVendorRosterDTO.GoogleMapsUrl),
                    "Google Maps URL must be an absolute HTTPS URL."));

            ValidateNotes(notes, notesPropertyName, failures);

            // Technician phones must be valid North American format when provided.
            NormalizeAndValidateTechnicians(nameof(CreateVendorRosterDTO.Technicians), technicians, failures);

            // Duplicate technician ids are not allowed.
            var duplicateIds = technicians
                .Where(t => t.Id.HasValue)
                .GroupBy(t => t.Id!.Value)
                .Where(group => group.Count() > 1)
                .Select(group => group.Key)
                .ToList();

            if (duplicateIds.Count > 0)
                failures.Add(new ValidationFailure(
                    nameof(CreateVendorRosterDTO.Technicians),
                    "Duplicate technician ids are not allowed."));

            if (failures.Count > 0)
                throw new ValidationException(failures);
        }

        // Normalizes technician phones in place and collects format failures using the
        // supplied property-name prefix so each endpoint reports its own payload path.
        private static void NormalizeAndValidateTechnicians(
            string techniciansPropertyName,
            List<RosterTechnicianInputDTO> technicians,
            List<ValidationFailure> failures)
        {
            for (var i = 0; i < technicians.Count; i++)
            {
                var technician = technicians[i];
                var normalized = VendorPhoneNormalizer.NormalizeToCanonical(technician.Phone);
                technician.Phone = normalized;

                if (!string.IsNullOrWhiteSpace(normalized) && !VendorPhoneNormalizer.NorthAmericanPhoneRegex.IsMatch(normalized))
                    failures.Add(new ValidationFailure(
                        $"{techniciansPropertyName}[{i}].{nameof(RosterTechnicianInputDTO.Phone)}",
                        "Phone must be in North American format: (XXX) XXX-XXXX"));

                if (!string.IsNullOrWhiteSpace(technician.Email) && !BeValidEmail(technician.Email))
                    failures.Add(new ValidationFailure(
                        $"{techniciansPropertyName}[{i}].{nameof(RosterTechnicianInputDTO.Email)}",
                        "Invalid email address."));

                if (!string.IsNullOrWhiteSpace(technician.PreferredContact) &&
                    !VendorValidationRules.BeValidPreferredContact(technician.PreferredContact))
                    failures.Add(new ValidationFailure(
                        $"{techniciansPropertyName}[{i}].{nameof(RosterTechnicianInputDTO.PreferredContact)}",
                        "PreferredContact must be one of: Phone, Email, Text"));
            }
        }

        // Validates optional company-level updates for the additive path and maps them
        // to the write model. A null (or blank) field means "leave unchanged"; blank
        // values normalize to null so a partial update can never clear data by accident.
        private static bool HasAnyCompanyValue(VendorRosterCompanyFieldsDTO fields) =>
            !string.IsNullOrWhiteSpace(fields.Name)
            || !string.IsNullOrWhiteSpace(fields.CompanyPhone)
            || !string.IsNullOrWhiteSpace(fields.Email)
            || !string.IsNullOrWhiteSpace(fields.Address)
            || !string.IsNullOrWhiteSpace(fields.City)
            || !string.IsNullOrWhiteSpace(fields.State)
            || !string.IsNullOrWhiteSpace(fields.Zip)
            || !string.IsNullOrWhiteSpace(fields.GoogleMapsUrl)
            || !string.IsNullOrWhiteSpace(fields.Notes);

        private static bool HasNoCompanyChange(VendorRosterCompanyFieldsWriteModel model) =>
            model.Name == null
            && model.CompanyPhone == null
            && model.Email == null
            && model.Address == null
            && model.City == null
            && model.State == null
            && model.Zip == null
            && model.GoogleMapsUrl == null
            && model.Notes == null;

        private static VendorRosterCompanyFieldsWriteModel ValidateAndMapCompanyFields(
            VendorRosterCompanyFieldsDTO fields,
            List<ValidationFailure> failures)
        {
            var name = fields.Name?.Trim();
            if (fields.Name != null && string.IsNullOrWhiteSpace(name))
                failures.Add(new ValidationFailure(
                    nameof(VendorRosterCompanyFieldsDTO.Name),
                    "Company name is required."));

            var normalizedPhone = VendorPhoneNormalizer.NormalizeToCanonical(fields.CompanyPhone);
            if (normalizedPhone != null && !VendorPhoneNormalizer.NorthAmericanPhoneRegex.IsMatch(normalizedPhone))
                failures.Add(new ValidationFailure(
                    nameof(VendorRosterCompanyFieldsDTO.CompanyPhone),
                    "Company phone must be in North American format: (XXX) XXX-XXXX"));

            if (!string.IsNullOrWhiteSpace(fields.Email) && !BeValidEmail(fields.Email))
                failures.Add(new ValidationFailure(
                    nameof(VendorRosterCompanyFieldsDTO.Email),
                    "Invalid email address."));

            if (!string.IsNullOrWhiteSpace(fields.GoogleMapsUrl) && !BeValidAbsoluteHttpsUrl(fields.GoogleMapsUrl))
                failures.Add(new ValidationFailure(
                    nameof(VendorRosterCompanyFieldsDTO.GoogleMapsUrl),
                    "Google Maps URL must be an absolute HTTPS URL."));

            ValidateNotes(
                fields.Notes,
                $"{nameof(AddTechniciansVendorRosterDTO.CompanyFields)}.{nameof(VendorRosterCompanyFieldsDTO.Notes)}",
                failures);

            return new VendorRosterCompanyFieldsWriteModel
            {
                Name = name,
                CompanyPhone = normalizedPhone,
                Email = string.IsNullOrWhiteSpace(fields.Email) ? null : fields.Email,
                Address = string.IsNullOrWhiteSpace(fields.Address) ? null : fields.Address,
                City = string.IsNullOrWhiteSpace(fields.City) ? null : fields.City,
                State = string.IsNullOrWhiteSpace(fields.State) ? null : fields.State,
                Zip = string.IsNullOrWhiteSpace(fields.Zip) ? null : fields.Zip,
                GoogleMapsUrl = string.IsNullOrWhiteSpace(fields.GoogleMapsUrl) ? null : fields.GoogleMapsUrl,
                Notes = string.IsNullOrWhiteSpace(fields.Notes) ? null : fields.Notes
            };
        }

        private static void ValidateNotes(
            string? notes,
            string propertyName,
            List<ValidationFailure> failures)
        {
            if (notes?.Length > MaxNotesLength)
                failures.Add(new ValidationFailure(propertyName, NotesMaxLengthMessage));
        }

        private async Task EnsureTechnicianIdsBelongToCompanyAsync(
            int companyId,
            List<RosterTechnicianInputDTO> technicians,
            CancellationToken cancellationToken)
        {
            var requestedIds = technicians
                .Where(t => t.Id.HasValue)
                .Select(t => t.Id!.Value)
                .Distinct()
                .ToList();

            if (requestedIds.Count == 0)
                return;

            var roster = await _rosterDataService.GetRosterAsync(null, companyId, cancellationToken);
            if (roster == null)
                throw new ValidationException(new[]
                {
                    new ValidationFailure(nameof(ReconcileVendorRosterDTO.Name), $"No vendor company exists with ID {companyId}.")
                });

            var validIds = roster.Technicians.Select(t => t.Id).ToHashSet();
            var mismatched = requestedIds.Where(id => !validIds.Contains(id)).ToList();

            if (mismatched.Count > 0)
                throw new ValidationException(new[]
                {
                    new ValidationFailure(
                        nameof(ReconcileVendorRosterDTO.Technicians),
                        $"Technician ids do not belong to company {companyId}: {string.Join(", ", mismatched)}.")
                });
        }

        private static List<RosterTechnicianWriteModel> MapTechnicians(List<RosterTechnicianInputDTO> technicians)
        {
            return technicians.Select(t => new RosterTechnicianWriteModel
            {
                Id = t.Id,
                ContactName = t.ContactName,
                Phone = t.Phone,
                Email = t.Email,
                PreferredContact = t.PreferredContact,
                TradeSpecialties = t.TradeSpecialties,
                IsActive = t.IsActive ?? true
            }).ToList();
        }

        private static byte[] ParseRequiredRowVersion(string? base64)
        {
            if (string.IsNullOrWhiteSpace(base64))
                throw new ValidationException(new[]
                {
                    new ValidationFailure(nameof(ReconcileVendorRosterDTO.RowVersion), "Row version is required.")
                });

            try
            {
                return Convert.FromBase64String(base64);
            }
            catch (FormatException)
            {
                throw new ValidationException(new[]
                {
                    new ValidationFailure(nameof(ReconcileVendorRosterDTO.RowVersion), "Invalid row version format.")
                });
            }
        }

        private static bool BeValidEmail(string? value) =>
            System.Net.Mail.MailAddress.TryCreate(value, out var address) && address.Address == value;

        private static bool BeValidAbsoluteHttpsUrl(string? value) =>
            Uri.TryCreate(value, UriKind.Absolute, out var uri) && uri.Scheme == Uri.UriSchemeHttps;

        private static VendorRosterDTO MapToDTO(VendorCompanyRosterReadModel roster) => new()
        {
            CompanyId = roster.CompanyId,
            Name = roster.Name,
            CompanyPhone = roster.CompanyPhone,
            Email = roster.Email,
            Address = roster.Address,
            City = roster.City,
            State = roster.State,
            Zip = roster.Zip,
            GoogleMapsUrl = roster.GoogleMapsUrl,
            Notes = roster.Notes,
            RowVersion = roster.RowVersion == null ? null : Convert.ToBase64String(roster.RowVersion),
            Technicians = roster.Technicians.Select(t => new VendorRosterTechnicianDTO
            {
                Id = t.Id,
                ContactName = t.ContactName,
                Phone = t.Phone,
                Email = t.Email,
                PreferredContact = t.PreferredContact,
                TradeSpecialties = t.TradeSpecialties,
                IsActive = t.IsActive,
                TotalJobs = t.TotalJobs
            }).ToList()
        };
    }
}