using FluentValidation.Results;
using SeaHaven.Services.DTOs;

namespace SeaHaven.Services.Validation
{
    /// <summary>
    /// SH-138 site-contact request validation shared by location create and update.
    /// Null contacts means legacy behavior (no validation, no mutation);
    /// a present array must contain 1..20 complete rows.
    /// </summary>
    public static class SiteContactsValidation
    {
        public const int MaxContacts = 20;
        public const int MaxNameLength = 100;
        public const int MaxPhoneLength = 20;

        public static List<ValidationFailure> Validate(IReadOnlyList<SiteContactRequestDTO> contacts)
        {
            var failures = new List<ValidationFailure>();

            if (contacts.Count == 0)
            {
                failures.Add(new ValidationFailure(
                    nameof(LocationCreateRequestDTO.Contacts),
                    "Contacts must contain at least one contact when provided."));
                return failures;
            }

            if (contacts.Count > MaxContacts)
            {
                failures.Add(new ValidationFailure(
                    nameof(LocationCreateRequestDTO.Contacts),
                    $"Contacts cannot exceed {MaxContacts} entries."));
                return failures;
            }

            var seenIds = new HashSet<int>();
            for (var i = 0; i < contacts.Count; i++)
            {
                var row = contacts[i];
                var name = row.Name?.Trim();
                var phone = row.Phone?.Trim();

                if (string.IsNullOrWhiteSpace(name))
                {
                    failures.Add(new ValidationFailure(
                        $"{nameof(LocationCreateRequestDTO.Contacts)}[{i}].{nameof(SiteContactRequestDTO.Name)}",
                        "Contact name is required."));
                }
                else if (name.Length > MaxNameLength)
                {
                    failures.Add(new ValidationFailure(
                        $"{nameof(LocationCreateRequestDTO.Contacts)}[{i}].{nameof(SiteContactRequestDTO.Name)}",
                        $"Contact name cannot exceed {MaxNameLength} characters."));
                }

                if (string.IsNullOrWhiteSpace(phone))
                {
                    failures.Add(new ValidationFailure(
                        $"{nameof(LocationCreateRequestDTO.Contacts)}[{i}].{nameof(SiteContactRequestDTO.Phone)}",
                        "Contact phone is required."));
                }
                else if (phone.Length > MaxPhoneLength)
                {
                    failures.Add(new ValidationFailure(
                        $"{nameof(LocationCreateRequestDTO.Contacts)}[{i}].{nameof(SiteContactRequestDTO.Phone)}",
                        $"Contact phone cannot exceed {MaxPhoneLength} characters."));
                }

                if (row.Id is int id && !seenIds.Add(id))
                {
                    failures.Add(new ValidationFailure(
                        $"{nameof(LocationCreateRequestDTO.Contacts)}[{i}].{nameof(SiteContactRequestDTO.Id)}",
                        $"Contact id {id} appears more than once."));
                }
            }

            return failures;
        }
    }
}