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

namespace StarfaceOutlookSync.Services
{
    /// <summary>
    /// Feldweises 3-Wege-Merge zweier Kontaktstaende gegen ihre Baseline.
    /// Erlaubt es, dass zwei Stellen unterschiedliche Felder desselben Kontakts
    /// aendern, ohne dass eine Aenderung verloren geht. Nur wenn DASSELBE Feld
    /// auf beiden Seiten geaendert wurde, greift die Vorrang-Regel.
    /// </summary>
    public static class ContactMerger
    {
        private class FieldDef
        {
            public string Key;
            public string Label;
            public Func<UnifiedContact, string> Get;
            public Action<UnifiedContact, string> Set;
            public bool IsPhone;
        }

        private static readonly FieldDef[] Fields = new[]
        {
            new FieldDef { Key = "FirstName",      Label = "Vorname",        Get = c => c.FirstName,      Set = (c, v) => c.FirstName = v },
            new FieldDef { Key = "LastName",       Label = "Nachname",       Get = c => c.LastName,       Set = (c, v) => c.LastName = v },
            new FieldDef { Key = "Company",        Label = "Firma",          Get = c => c.Company,        Set = (c, v) => c.Company = v },
            new FieldDef { Key = "JobTitle",       Label = "Position",       Get = c => c.JobTitle,       Set = (c, v) => c.JobTitle = v },
            new FieldDef { Key = "Email",          Label = "E-Mail",         Get = c => c.Email,          Set = (c, v) => c.Email = v },
            new FieldDef { Key = "EmailSecondary", Label = "E-Mail 2",       Get = c => c.EmailSecondary, Set = (c, v) => c.EmailSecondary = v },
            new FieldDef { Key = "PhoneWork",      Label = "Telefon",        Get = c => c.PhoneWork,      Set = (c, v) => c.PhoneWork = v,   IsPhone = true },
            new FieldDef { Key = "PhoneMobile",    Label = "Mobil",          Get = c => c.PhoneMobile,    Set = (c, v) => c.PhoneMobile = v, IsPhone = true },
            new FieldDef { Key = "PhoneHome",      Label = "Telefon privat", Get = c => c.PhoneHome,      Set = (c, v) => c.PhoneHome = v,   IsPhone = true },
            new FieldDef { Key = "Fax",            Label = "Fax",            Get = c => c.Fax,            Set = (c, v) => c.Fax = v,         IsPhone = true },
            new FieldDef { Key = "Street",         Label = "Strasse",        Get = c => c.Street,         Set = (c, v) => c.Street = v },
            new FieldDef { Key = "City",           Label = "Ort",            Get = c => c.City,           Set = (c, v) => c.City = v },
            new FieldDef { Key = "PostalCode",     Label = "PLZ",            Get = c => c.PostalCode,     Set = (c, v) => c.PostalCode = v },
            new FieldDef { Key = "State",          Label = "Bundesland",     Get = c => c.State,          Set = (c, v) => c.State = v },
            new FieldDef { Key = "Country",        Label = "Land",           Get = c => c.Country,        Set = (c, v) => c.Country = v },
            new FieldDef { Key = "Website",        Label = "Webseite",       Get = c => c.Website,        Set = (c, v) => c.Website = v },
            new FieldDef { Key = "Notes",          Label = "Notizen",        Get = c => c.Notes,          Set = (c, v) => c.Notes = v },
            new FieldDef { Key = "Salutation",     Label = "Anrede",         Get = c => c.Salutation,     Set = (c, v) => c.Salutation = v },
            new FieldDef { Key = "Title",          Label = "Titel",          Get = c => c.Title,          Set = (c, v) => c.Title = v },
            new FieldDef { Key = "Birthday",       Label = "Geburtstag",     Get = c => c.Birthday,       Set = (c, v) => c.Birthday = v },
        };

        /// <summary>Liest den Wert eines Feldes per stabilem Schluessel.</summary>
        public static string GetValue(UnifiedContact c, string key)
        {
            if (c == null || string.IsNullOrEmpty(key)) return "";
            var f = Fields.FirstOrDefault(x => x.Key == key);
            return f == null ? "" : (f.Get(c) ?? "");
        }

        /// <summary>Vergleicht zwei Feldwerte (telefon-normalisiert je nach Feld).</summary>
        public static bool ValuesEqual(string key, string a, string b)
        {
            var f = Fields.FirstOrDefault(x => x.Key == key);
            return Equal(a ?? "", b ?? "", f?.IsPhone ?? false);
        }

        /// <summary>
        /// Fuehrt den Outlook- und Starface-Stand gegen ihre jeweilige Baseline
        /// zusammen. outlookWins entscheidet bei echten Feld-Konflikten.
        /// </summary>
        public static (UnifiedContact merged, List<FieldConflict> conflicts) Merge(
            UnifiedContact baseOutlook, UnifiedContact baseStarface,
            UnifiedContact outlook, UnifiedContact starface,
            bool outlookWins)
        {
            var merged = new UnifiedContact
            {
                OutlookEntryId = outlook.OutlookEntryId,
                StarfaceId = starface.StarfaceId
            };
            var conflicts = new List<FieldConflict>();

            foreach (var f in Fields)
            {
                string olv = f.Get(outlook) ?? "";
                string sfv = f.Get(starface) ?? "";
                string bol = f.Get(baseOutlook) ?? "";
                string bsf = f.Get(baseStarface) ?? "";

                bool olChanged = !Equal(olv, bol, f.IsPhone);
                bool sfChanged = !Equal(sfv, bsf, f.IsPhone);

                string chosen;
                if (olChanged && !sfChanged)
                {
                    chosen = olv;
                }
                else if (sfChanged && !olChanged)
                {
                    chosen = sfv;
                }
                else if (olChanged && sfChanged)
                {
                    if (Equal(olv, sfv, f.IsPhone))
                    {
                        // Beide auf denselben Wert geaendert -> kein echter Konflikt.
                        chosen = olv;
                    }
                    else
                    {
                        chosen = outlookWins ? olv : sfv;
                        conflicts.Add(new FieldConflict
                        {
                            StarfaceId = starface.StarfaceId,
                            ContactName = outlook.DisplayName,
                            Field = f.Label,
                            FieldKey = f.Key,
                            OutlookValue = olv,
                            StarfaceValue = sfv,
                            Winner = outlookWins ? "Outlook" : "Starface"
                        });
                    }
                }
                else
                {
                    // Keine Seite hat dieses Feld geaendert -> Outlook-Wert behalten.
                    chosen = olv;
                }

                f.Set(merged, chosen);
            }

            return (merged, conflicts);
        }

        private static bool Equal(string a, string b, bool isPhone)
        {
            if (isPhone)
                return NormalizePhone(a) == NormalizePhone(b);
            return string.Equals(a ?? "", b ?? "", StringComparison.OrdinalIgnoreCase);
        }

        private static string NormalizePhone(string phone)
        {
            if (string.IsNullOrEmpty(phone)) return "";
            return new string(phone.Where(c => char.IsDigit(c) || c == '+').ToArray());
        }
    }
}