using System;
using System.Collections.Generic;
using System.Linq;
using StarfaceOutlookSync.Models;

namespace StarfaceOutlookSync.Services
{
    /// <summary>
    /// Erkennt, ob zwei Kontakte dieselbe Person/Firma sind. Wird sowohl vom
    /// Sync (Wiederzuordnung, Duplikat-Vermeidung) als auch von der
    /// Dubletten-Zusammenfuehrung genutzt - beide MUESSEN dieselbe Logik
    /// verwenden, sonst laufen sie gegeneinander.
    /// </summary>
    public static class ContactMatcher
    {
        public static UnifiedContact FindMatch(UnifiedContact contact, List<UnifiedContact> candidates)
        {
            if (candidates == null || candidates.Count == 0) return null;
            foreach (var c in candidates)
                if (IsMatch(contact, c))
                    return c;
            return null;
        }

        public static bool IsMatch(UnifiedContact a, UnifiedContact b)
        {
            bool hasName = (!string.IsNullOrEmpty(a.FirstName) || !string.IsNullOrEmpty(a.LastName))
                           && (!string.IsNullOrEmpty(b.FirstName) || !string.IsNullOrEmpty(b.LastName));

            bool emailMatch = !string.IsNullOrEmpty(a.Email) && !string.IsNullOrEmpty(b.Email)
                              && a.Email.Equals(b.Email, StringComparison.OrdinalIgnoreCase);
            bool nameMatch = hasName
                             && (a.FirstName ?? "").Equals(b.FirstName ?? "", StringComparison.OrdinalIgnoreCase)
                             && (a.LastName ?? "").Equals(b.LastName ?? "", StringComparison.OrdinalIgnoreCase);
            // Telefon feldUEBERGREIFEND und formatunabhaengig (+49 == 0).
            bool phoneMatch = SharedPhone(a, b);
            bool companyMatch = !string.IsNullOrEmpty(a.Company) && !string.IsNullOrEmpty(b.Company)
                                && a.Company.Equals(b.Company, StringComparison.OrdinalIgnoreCase);

            bool emailContradiction = !string.IsNullOrEmpty(a.Email) && !string.IsNullOrEmpty(b.Email) && !emailMatch;

            if (emailMatch) return true;
            if (nameMatch && !emailContradiction) return true;

            // Firma-/Service-Eintraege OHNE Personennamen: gleiche Firma + gemeinsame
            // Nummer. Bewusst nur ohne Namen, damit nicht zwei Kollegen mit gleicher
            // Zentrale-Nummer + Firma faelschlich verschmolzen werden.
            bool aHasName = !string.IsNullOrEmpty(a.FirstName) || !string.IsNullOrEmpty(a.LastName);
            bool bHasName = !string.IsNullOrEmpty(b.FirstName) || !string.IsNullOrEmpty(b.LastName);
            if (phoneMatch && companyMatch && !aHasName && !bHasName && !emailContradiction) return true;

            // Reine Nummern-Eintraege: eine gemeinsame Rufnummer identifiziert den Eintrag.
            if (phoneMatch && IsBareNumberEntry(a) && IsBareNumberEntry(b)) return true;

            return false;
        }

        private static bool IsBareNumberEntry(UnifiedContact c) =>
            string.IsNullOrEmpty(c.FirstName) && string.IsNullOrEmpty(c.LastName)
            && string.IsNullOrEmpty(c.Company) && string.IsNullOrEmpty(c.Email);

        /// <summary>True, wenn a und b mindestens eine (normalisierte) Rufnummer gemeinsam haben.</summary>
        public static bool SharedPhone(UnifiedContact a, UnifiedContact b)
        {
            var pa = PhoneSet(a);
            if (pa.Count == 0) return false;
            var pb = PhoneSet(b);
            return pb.Count > 0 && pa.Overlaps(pb);
        }

        private static HashSet<string> PhoneSet(UnifiedContact c)
        {
            var set = new HashSet<string>();
            foreach (var p in new[] { c.PhoneWork, c.PhoneMobile, c.PhoneHome, c.Fax })
            {
                var n = NormalizePhone(p);
                if (n.Length >= 5) set.Add(n); // zu kurze (z.B. reine Durchwahlen) ignorieren
            }
            return set;
        }

        public static string NormalizePhone(string phone)
        {
            if (string.IsNullOrEmpty(phone)) return "";
            var s = new string(phone.Where(c => char.IsDigit(c) || c == '+').ToArray());
            if (s.StartsWith("+49")) s = "0" + s.Substring(3);
            else if (s.StartsWith("0049")) s = "0" + s.Substring(4);
            else if (s.StartsWith("+")) s = s.Substring(1);
            return s;
        }
    }
}