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

namespace GerbilManagerWebAPI.Import
{
    /// <summary>
    /// FEAT-8c import loader. Consumes tools/import/output (animals.json + litters.json
    /// produced by extract.py) and loads conflict-free data into the database:
    /// litters first (Wurfchronik = authoritative), then animals matched onto them.
    ///
    /// Load policy:
    ///   - Litters: all created (idempotent by ExternalRef = source litter id).
    ///   - Animals: created when they have a DOB and are NOT in conflict. The birth-litter
    ///     link is set only for HIGH-confidence matches (litterRef.confidence == "hoch");
    ///     date-only/ambiguous links are quarantined (animal loads with LitterId = null).
    ///   - QUARANTINED (never loaded): conflicts + stubs (no DOB) — await the wife's review.
    /// Idempotent: re-running matches on ExternalRef and skips existing rows.
    /// Execute is gated by the endpoint; this service only acts when asked.
    /// </summary>
    public sealed class ImportService
    {
        private static readonly string[] LocusOrder = { "A", "C", "D", "E", "G", "P", "Sp", "Re" };
        private static readonly JsonSerializerOptions Json = new()
        {
            PropertyNameCaseInsensitive = true,
        };
        private const string ImportSourceTag = "FEAT-8 Stammbaum/Wurfchronik";

        private readonly ApplicationContext _db;
        private readonly string _sourceDir;
        private readonly string _photoRoot;

        /// <summary>Test-friendly constructor with explicit paths.</summary>
        public ImportService(ApplicationContext db, string sourceDir, string photoRoot)
        {
            _db = db;
            _sourceDir = sourceDir;
            _photoRoot = photoRoot;
        }

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

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

            var animals = Load<List<SourceAnimal>>("animals.json") ?? new();
            var litters = Load<List<SourceLitter>>("litters.json") ?? new();
            if (animals.Count == 0 && litters.Count == 0)
                notes.Add($"Keine Quelldaten gefunden in {_sourceDir} (animals.json/litters.json). extract.py zuerst ausführen.");

            // ---- categorise animals ----
            var loadable = new List<SourceAnimal>();
            int conflicts = 0, stubs = 0, dateOnly = 0, ambiguous = 0;
            foreach (var a in animals)
            {
                if (a.Conflict) { conflicts++; continue; }
                if (string.IsNullOrEmpty(a.Dob)) { stubs++; continue; }
                loadable.Add(a);
                var conf = a.LitterRef?.Confidence;
                if (a.LitterRef?.Candidates is { Count: > 0 }) ambiguous++;
                else if (conf == "niedrig") dateOnly++;
            }

            // existing rows (idempotency). Gerbils carry ExternalRef; Litters have no such
            // column, so we key litter idempotency on the stable (Name + Date) pair instead.
            var existingGerbilExtRefs = await _db.Gerbils
                .Where(g => g.ExternalRef != null)
                .Select(g => g.ExternalRef!).ToListAsync();
            var existingGerbilSet = existingGerbilExtRefs.ToHashSet();

            var existingLitterKeys = await _db.Litters
                .Select(l => new { l.Name, l.Date }).ToListAsync();
            var existingLitterKeySet = existingLitterKeys
                .Select(x => $"{x.Name}|{x.Date:yyyy-MM-dd}").ToHashSet();

            // colour-variety name -> id (case-insensitive)
            var varieties = await _db.ColorVarieties.Select(v => new { v.Id, v.Name }).ToListAsync();
            var varietyByName = varieties
                .GroupBy(v => v.Name.Trim().ToLowerInvariant())
                .ToDictionary(g => g.Key, g => g.First().Id);

            // gender inference from litter roles (sire -> male, dam -> female; both -> unknown)
            var sireNames = litters.Select(l => Normalize(StripZucht(l.SireName))).Where(s => s.Length > 0).ToHashSet();
            var damNames = litters.Select(l => Normalize(StripZucht(l.DamName))).Where(s => s.Length > 0).ToHashSet();

            // ---- litters: create map source.id -> Litter (for high-confidence animal links) ----
            int littersCreated = 0, littersExisting = 0;
            var litterIdMap = new Dictionary<string, Guid>();    // source litter id -> Litter.Id
            foreach (var sl in litters)
            {
                var date = ParseDate(sl.Date);
                var name = $"Wurf {sl.LitterId}".Trim();
                var key = $"{name}|{date:yyyy-MM-dd}";
                if (existingLitterKeySet.Contains(key)) { littersExisting++; continue; }

                var id = Guid.NewGuid();
                litterIdMap[sl.Id] = id;
                littersCreated++;
                if (execute && date is DateOnly d)
                {
                    _db.Litters.Add(new Litter
                    {
                        Id = id,
                        Name = name,
                        Date = d,
                        TotalBorn = sl.TotalBorn,
                        Notes = string.IsNullOrWhiteSpace(sl.Note) ? null : sl.Note,
                        PairingCode = string.IsNullOrWhiteSpace(sl.Zuchtnummer) ? null : sl.Zuchtnummer,
                    });
                }
                if (samples.Count < 8 && date is not null)
                    samples.Add($"Wurf: {name} ({sl.Date}) — {sl.DamName} × {sl.SireName}");
            }
            if (execute) await _db.SaveChangesAsync();

            // ---- animals ----
            int animalsCreated = 0, linked = 0, fbMatched = 0, fbUnmatched = 0, animalsExisting = 0;
            int photosAttached = 0, photosMissing = 0;
            var createdAnimalByName = new Dictionary<string, Guid>();  // normalized name -> gerbil id (for litter back-link)

            foreach (var a in loadable)
            {
                if (existingGerbilSet.Contains(a.Id)) { animalsExisting++; continue; }
                animalsCreated++;

                Guid? litterId = null;
                if (a.LitterRef?.Confidence == "hoch" && a.LitterRef.Candidates is not { Count: > 0 }
                    && litterIdMap.TryGetValue(a.LitterRef.LitterId, out var lid))
                {
                    litterId = lid;
                    linked++;
                }

                Guid? colorVarietyId = null;
                var fbCandidates = new[] { a.Farbschlag }.Concat(a.FarbschlagVariants)
                    .Where(s => !string.IsNullOrWhiteSpace(s));
                foreach (var fb in fbCandidates)
                {
                    if (varietyByName.TryGetValue(fb.Trim().ToLowerInvariant(), out var vid))
                    { colorVarietyId = vid; break; }
                }
                if (colorVarietyId is null) fbUnmatched++; else fbMatched++;

                var gender = InferGender(a, sireNames, damNames);
                var gid = Guid.NewGuid();
                var norm = Normalize(StripZucht(a.Name));
                if (norm.Length > 0) createdAnimalByName.TryAdd(norm, gid);

                if (samples.Count < 16)
                    samples.Add($"Tier: {a.Name} (*{a.Dob}), Genotyp {ComposeGenotype(a.Genotype)}"
                        + (litterId is not null ? ", Wurf-verknüpft" : "")
                        + (colorVarietyId is not null ? $", Farbschlag „{a.Farbschlag}\"" : ""));

                if (execute)
                {
                    _db.Gerbils.Add(new Gerbil
                    {
                        Id = gid,
                        Name = a.Name,
                        Gender = gender,
                        Status = GerbilStatus.Active,
                        DateOfBirth = ParseDate(a.Dob),
                        DateOfDeath = ParseDate(a.Death),
                        LitterId = litterId,
                        ColorVarietyId = colorVarietyId,
                        Genotype = ComposeGenotype(a.Genotype),
                        ImportSource = ImportSourceTag,
                        ExternalRef = a.Id,
                        RawImportData = JsonSerializer.Serialize(new
                        {
                            a.Genotype.RawGenotype,
                            a.Genotype.UnmappedTokens,
                            a.Zucht,
                            a.SourceFiles,
                            FarbschlagRaw = a.Farbschlag,
                        }),
                    });
                }

                // photos
                foreach (var rel in a.Photos)
                {
                    var src = Path.Combine(_sourceDir, rel.Replace('/', Path.DirectorySeparatorChar));
                    if (!File.Exists(src)) { photosMissing++; continue; }
                    photosAttached++;
                    if (execute)
                    {
                        Directory.CreateDirectory(_photoRoot);
                        var fileName = $"{Guid.NewGuid():N}{Path.GetExtension(src)}";
                        File.Copy(src, Path.Combine(_photoRoot, fileName), overwrite: true);
                        _db.GerbilPhotos.Add(new GerbilPhoto
                        {
                            Id = Guid.NewGuid(),
                            GerbilId = gid,
                            FileName = fileName,
                            SortOrder = 0,
                            CreatedAt = DateTimeOffset.UtcNow,
                        });
                    }
                }
            }
            if (execute) await _db.SaveChangesAsync();

            // ---- back-link litter parents by name (best effort) ----
            if (execute)
            {
                foreach (var sl in litters)
                {
                    if (!litterIdMap.TryGetValue(sl.Id, out var lid)) continue;
                    var litter = await _db.Litters.FirstOrDefaultAsync(l => l.Id == lid);
                    if (litter is null) continue;
                    if (createdAnimalByName.TryGetValue(Normalize(StripZucht(sl.SireName)), out var fId))
                        litter.FatherId = fId;
                    if (createdAnimalByName.TryGetValue(Normalize(StripZucht(sl.DamName)), out var mId))
                        litter.MotherId = mId;
                }
                await _db.SaveChangesAsync();
            }

            notes.Add("Quarantäne (kein Import): Konflikte + Stubs ohne Geburtsdatum + unsichere Wurf-Zuordnungen — warten auf die Prüfung durch die Züchterin.");
            if (!execute) notes.Add("DRY-RUN: nichts gespeichert. /import/execute lädt die konfliktfreien Daten.");

            return new ImportReport(
                Executed: execute,
                Litters: new LitterSummary(litters.Count, littersCreated, littersExisting),
                Animals: new AnimalSummary(
                    animals.Count, animalsCreated, linked, fbMatched, fbUnmatched, animalsExisting,
                    new QuarantineSummary(conflicts, stubs, dateOnly, ambiguous, conflicts + stubs)),
                Photos: new PhotoSummary(photosAttached, photosMissing),
                Samples: samples,
                Notes: 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);
        }

        public static string ComposeGenotype(SourceGenotype g)
        {
            var tokens = LocusOrder.Select(locus =>
            {
                if (g.Mapped8locus.TryGetValue(locus, out var pair) && pair.Count == 2)
                    return StripCaret(pair[0]) + StripCaret(pair[1]);
                return "??";
            });
            return string.Join(' ', tokens);
        }

        private static string StripCaret(string allele) => allele.Replace("^", "");

        private static Gender InferGender(SourceAnimal a, HashSet<string> sires, HashSet<string> dams)
        {
            var n = Normalize(StripZucht(a.Name));
            bool isSire = sires.Contains(n), isDam = dams.Contains(n);
            if (isSire && !isDam) return Gender.male;
            if (isDam && !isSire) return Gender.female;
            return Gender.unknown;
        }

        public static DateOnly? ParseDate(string s)
        {
            if (string.IsNullOrWhiteSpace(s)) return null;
            var m = 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 StripZucht(string name)
        {
            var n = Regex.Replace(name ?? "", @"\[.*?\]", " ");
            n = Regex.Replace(n, @"\s+(?:of|von\s+den|von\s+der|v\.\s?d\.|von)\s+.*$", "", RegexOptions.IgnoreCase);
            return n.Trim();
        }

        private static string Normalize(string name)
        {
            var n = (name ?? "").ToLowerInvariant();
            n = Regex.Replace(n, @"\bgen\.\b", " ");
            n = Regex.Replace(n, @"[^a-z0-9äöüß]", "");
            return n;
        }
    }
}