using System.Text.Json;
using GerbilManagerWebAPI.Models;
using Microsoft.EntityFrameworkCore;

namespace GerbilManagerWebAPI.Import
{
    /// <summary>
    /// FEAT-8d docx loader. Consumes tools/import/output/docx_litters.json +
    /// docx_animals.json (produced by extract_docx.py) and enriches the database:
    ///
    /// Load policy (IDEMPOTENT NACHZUG after main WIPE+REIMPORT):
    ///   - Litter link: match docx WS-code to Litters.PairingCode → set Gerbil.LitterId
    ///     for animals matched by normalize(name) + litter birth date.
    ///   - ReceiverContact: lookup-or-create Contact by owner name → set ReceiverContactId.
    ///   - GoHomeDate, DateOfDeath, CauseOfDeath: fill if currently null (fill-NULL-only).
    ///   - NEVER overwrites a manually-set non-null value.
    ///
    /// Idempotent: running multiple times is safe. Each run resolves whatever is still null.
    /// Execute is gated by the endpoint; this service only acts when asked.
    /// </summary>
    public sealed class ImportDocxService
    {
        private static readonly JsonSerializerOptions Json = new() { PropertyNameCaseInsensitive = true };

        private readonly ApplicationContext _db;
        private readonly string _sourceDir;

        public ImportDocxService(ApplicationContext db, IConfiguration config, IWebHostEnvironment env)
            : this(db,
                   config["Import:SourcePath"]
                       ?? Path.GetFullPath(Path.Combine(env.ContentRootPath, "..", "tools", "import", "output")))
        { }

        public ImportDocxService(ApplicationContext db, string sourceDir)
        {
            _db = db;
            _sourceDir = sourceDir;
        }

        public async Task<ImportDocxReport> RunAsync(bool execute)
        {
            var notes = new List<string>();

            var docxLitters = Load<List<DocxLitter>>("docx_litters.json") ?? new();
            var docxAnimals = Load<List<DocxAnimal>>("docx_animals.json") ?? new();

            if (docxLitters.Count == 0 && docxAnimals.Count == 0)
            {
                notes.Add($"Keine Quelldaten in {_sourceDir} (docx_litters.json/docx_animals.json). " +
                          "extract_docx.py zuerst ausführen.");
                return new ImportDocxReport(false, 0, 0, 0, 0, 0, 0, notes);
            }

            // Build lookup: PairingCode → Litter.Id (WS-code normalised: spaces removed)
            var littersInDb = await _db.Litters
                .Where(l => l.PairingCode != null)
                .Select(l => new { l.Id, l.Date, l.PairingCode })
                .ToListAsync();
            var litterByWs = littersInDb
                .GroupBy(l => l.PairingCode!.Replace(" ", ""))
                .ToDictionary(g => g.Key, g => g.ToList());

            // Build animal lookup: normalize(name) + litter_dob → Gerbil (for litter-link)
            var gerbilsInDb = await _db.Gerbils
                .Select(g => new { g.Id, g.Name, g.DateOfBirth, g.LitterId,
                                   g.ReceiverContactId, g.GoHomeDate, g.DateOfDeath, g.CauseOfDeath })
                .ToListAsync();
            var gerbilByKey = gerbilsInDb
                .Where(g => g.DateOfBirth is not null)
                .GroupBy(g => NameDobKey(g.Name, g.DateOfBirth!.Value))
                .ToDictionary(g => g.Key, g => g.ToList());

            // Contact lookup: normalized name → existing Contact
            var contactsInDb = await _db.Contacts
                .Select(c => new { c.Id, c.Name })
                .ToListAsync();
            var contactByNorm = contactsInDb
                .GroupBy(c => NormalizeName(c.Name))
                .ToDictionary(g => g.Key, g => g.First().Id);

            int litterLinked = 0, goHomeFilled = 0, deathFilled = 0;
            int ownerLinked = 0, ownerCreated = 0, skipped = 0;

            foreach (var da in docxAnimals)
            {
                if (string.IsNullOrWhiteSpace(da.Name)) { skipped++; continue; }

                // Resolve the litter by WS-code + approximate birth date
                Guid? litterId = null;
                if (!string.IsNullOrWhiteSpace(da.WsCode) && !string.IsNullOrWhiteSpace(da.LitterDob))
                {
                    var litterDob = ParseDate(da.LitterDob);
                    if (litterDob is not null && litterByWs.TryGetValue(da.WsCode.Replace(" ", ""), out var cands))
                    {
                        // Pick the litter whose date matches (within ±5 days for rounding)
                        var match = cands.FirstOrDefault(l =>
                            Math.Abs((l.Date.DayNumber - litterDob.Value.DayNumber)) <= 5);
                        litterId = match?.Id;
                    }
                }

                // Resolve the gerbil by name + litter birth date
                var animalDob = litterId is not null
                    ? (await _db.Litters.Where(l => l.Id == litterId).Select(l => (DateOnly?)l.Date).FirstOrDefaultAsync())
                    : ParseDate(da.LitterDob);

                if (animalDob is null) { skipped++; continue; }

                var key = NameDobKey(da.Name, animalDob.Value);
                if (!gerbilByKey.TryGetValue(key, out var gerbilCands)) { skipped++; continue; }

                // If multiple gerbils match (same name+dob), take the one without a litter link first
                var gerbilSnap = gerbilCands.FirstOrDefault(g => g.LitterId == null)
                              ?? gerbilCands.First();

                // Resolve receiver contact (lookup-or-create)
                Guid? receiverId = null;
                if (!string.IsNullOrWhiteSpace(da.Owner))
                {
                    var normOwner = NormalizeName(da.Owner);
                    if (contactByNorm.TryGetValue(normOwner, out var existingId))
                    {
                        receiverId = existingId;
                        ownerLinked++;
                    }
                    else
                    {
                        ownerCreated++;
                        if (execute)
                        {
                            var newContact = new Contact { Id = Guid.NewGuid(), Name = da.Owner.Trim() };
                            _db.Contacts.Add(newContact);
                            await _db.SaveChangesAsync();
                            receiverId = newContact.Id;
                            contactByNorm[normOwner] = receiverId.Value;
                        }
                    }
                }

                var goHomeDate = ParseDate(da.AbgabeDate);
                var deathDate = ParseDate(da.DeathDate);

                // Count what will change
                bool willLinkLitter = litterId is not null && gerbilSnap.LitterId is null;
                bool willFillGoHome = goHomeDate is not null && gerbilSnap.GoHomeDate is null;
                bool willFillDeath = deathDate is not null && gerbilSnap.DateOfDeath is null;

                if (willLinkLitter) litterLinked++;
                if (willFillGoHome) goHomeFilled++;
                if (willFillDeath) deathFilled++;

                if (execute)
                {
                    var row = await _db.Gerbils.FirstOrDefaultAsync(g => g.Id == gerbilSnap.Id);
                    if (row is null) continue;

                    if (willLinkLitter) row.LitterId = litterId;
                    if (receiverId is not null && row.ReceiverContactId is null)
                        row.ReceiverContactId = receiverId;
                    if (willFillGoHome) row.GoHomeDate = goHomeDate;
                    if (willFillDeath)
                    {
                        row.DateOfDeath = deathDate;
                        if (!string.IsNullOrWhiteSpace(da.DeathCause) && row.CauseOfDeath is null)
                            row.CauseOfDeath = da.DeathCause.Trim();
                    }
                }
            }

            if (execute && (litterLinked + goHomeFilled + deathFilled + ownerLinked + ownerCreated) > 0)
                await _db.SaveChangesAsync();

            notes.Add($"Quelle: {docxLitters.Count} Würfe, {docxAnimals.Count} Tier-Zeilen aus der docx.");
            notes.Add($"Litter-Links: {litterLinked} Tiere einem Wurf zugeordnet (WS-Code → PairingCode).");
            notes.Add($"Abnehmer: {ownerLinked} bestehende Kontakte verknüpft, {ownerCreated} neue Kontakte angelegt.");
            notes.Add($"GoHomeDate: {goHomeFilled} Abgabe-Daten nachgetragen.");
            notes.Add($"Tod-Datum: {deathFilled} Todesdaten nachgetragen.");
            notes.Add($"Übersprungen: {skipped} Zeilen (kein Name oder kein DB-Match).");
            if (!execute) notes.Add("DRY-RUN: nichts gespeichert. /import/docx/execute schreibt die Änderungen.");

            return new ImportDocxReport(execute, litterLinked, ownerLinked + ownerCreated,
                goHomeFilled, deathFilled, ownerCreated, skipped, notes);
        }

        private T? Load<T>(string file)
        {
            var path = Path.Combine(_sourceDir, file);
            if (!File.Exists(path)) return default;
            using var fs = File.OpenRead(path);
            return JsonSerializer.Deserialize<T>(fs, Json);
        }

        private static DateOnly? ParseDate(string? s)
        {
            if (string.IsNullOrWhiteSpace(s)) return null;
            var m = System.Text.RegularExpressions.Regex.Match(s,
                @"(\d{1,2})\.(\d{1,2})\.(\d{2,4})");
            if (!m.Success) return null;
            int d = int.Parse(m.Groups[1].Value), mo = int.Parse(m.Groups[2].Value);
            int y = int.Parse(m.Groups[3].Value);
            if (y < 100) y += 2000;
            try { return new DateOnly(y, mo, d); } catch { return null; }
        }

        private static string NameDobKey(string name, DateOnly dob)
        {
            var n = System.Text.RegularExpressions.Regex.Replace(
                (name ?? "").ToLowerInvariant(), @"[^a-z0-9äöüß]", "");
            return $"{n}|{dob:yyyy-MM-dd}";
        }

        private static string NormalizeName(string name)
        {
            var n = (name ?? "").ToLowerInvariant();
            n = System.Text.RegularExpressions.Regex.Replace(n, @"\s+", " ").Trim();
            return n;
        }
    }

    // ---- Source shapes (from extract_docx.py output) ----

    public sealed class DocxLitter
    {
        public string LitterId { get; set; } = "";
        public string Dob { get; set; } = "";
        public string MotherName { get; set; } = "";
        public string FatherName { get; set; } = "";
        public string WsCode { get; set; } = "";
        public string Note { get; set; } = "";
    }

    public sealed class DocxAnimal
    {
        public string WsCode { get; set; } = "";
        public string LitterDob { get; set; } = "";
        public string Name { get; set; } = "";
        public string Farbschlag { get; set; } = "";
        public string Gender { get; set; } = "";
        public string Owner { get; set; } = "";
        public string AbgabeDate { get; set; } = "";
        public string AbgabeWeight { get; set; } = "";
        public string DeathDate { get; set; } = "";
        public string DeathCause { get; set; } = "";
        public string PartnerName { get; set; } = "";
        public string PartnerDob { get; set; } = "";
    }

    // ---- Report ----

    public sealed record ImportDocxReport(
        bool Executed,
        int LitterLinked,
        int OwnerLinked,
        int GoHomeFilled,
        int DeathFilled,
        int ContactsCreated,
        int Skipped,
        IReadOnlyList<string> Notes);
}