using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using LehrerApp.Core.Interfaces;
using LehrerApp.Core.Models;
using System.Collections.ObjectModel;
using System.Globalization;
using System.Linq;

namespace LehrerApp.Desktop.ViewModels.Students;

/// Für die Schüler-Auswahl im Dokumentationsdialog, wenn er ohne festen Schüler geöffnet wird
/// (Gruppen-Tab, siehe GroupDocumentationTabViewModel).
public record StudentOption(Guid Id, string Name);

// ── Dokumentation: deutsche Anzeige für Typ/Status (5.1) ─────────────────────

public static class DocumentationTypeDisplay
{
    public static string[] Options { get; } =
        ["Gespräch", "Vorkommnis", "Förderplan", "Fehlzeit", "Elternanruf", "Elternbrief"];

    public static string Label(DocumentationType t) => t switch
    {
        DocumentationType.Conversation => "Gespräch",
        DocumentationType.Incident     => "Vorkommnis",
        DocumentationType.SupportPlan  => "Förderplan",
        DocumentationType.Absence      => "Fehlzeit",
        DocumentationType.ParentCall   => "Elternanruf",
        DocumentationType.ParentLetter => "Elternbrief",
        _ => "",
    };

    public static DocumentationType FromLabel(string label) => label switch
    {
        "Vorkommnis"  => DocumentationType.Incident,
        "Förderplan"  => DocumentationType.SupportPlan,
        "Fehlzeit"    => DocumentationType.Absence,
        "Elternanruf" => DocumentationType.ParentCall,
        "Elternbrief" => DocumentationType.ParentLetter,
        _             => DocumentationType.Conversation,
    };
}

// ── Dokumentation: Labels zur Nachverfolgung ─────────────────────────────────

public static class DocumentationTagDisplay
{
    // Vorschläge für die AutoCompleteBox im Dialog — eigene Labels sind trotzdem frei möglich.
    public static string[] Suggestions { get; } =
    [
        "Kritisch", "Nacharbeiten", "Mit JGL abklären", "Erkundigung einholen",
        "Elterngespräch nötig", "Mit Schulleitung abklären", "Klassenkonferenz",
        "Frist beachten", "Beobachten", "Erledigt",
    ];

    public static string ColorHex(string tag) => tag switch
    {
        "Kritisch" or "Dringend"                     => "#E53935", // rot – Priorität
        "Erledigt"                                    => "#43A047", // grün – abgeschlossen
        "Beobachten" or "Frist beachten"               => "#1E88E5", // blau – im Blick behalten
        "Nacharbeiten" or "Mit JGL abklären" or "Erkundigung einholen"
            or "Elterngespräch nötig" or "Mit Schulleitung abklären" or "Klassenkonferenz"
            => "#FB8C00", // orange – Handlungsbedarf
        _ => "#757575", // grau – freies Label
    };
}

public static class SupportStatusDisplay
{
    public static string[] Options { get; } = ["Aktiv", "Abgeschlossen", "Pausiert"];

    public static string Label(SupportStatus s) => s switch
    {
        SupportStatus.Completed => "Abgeschlossen",
        SupportStatus.Paused    => "Pausiert",
        _                       => "Aktiv",
    };

    public static SupportStatus FromLabel(string label) => label switch
    {
        "Abgeschlossen" => SupportStatus.Completed,
        "Pausiert"      => SupportStatus.Paused,
        _               => SupportStatus.Active,
    };
}

// ── Dialog: Dokumentationseintrag anlegen/bearbeiten (5.1.1–5.1.3, 5.3.1) ────

public partial class DocumentationDialogViewModel : ObservableObject
{
    private readonly IAttachmentStorage _attachmentStorage;
    private readonly Documentation? _editing;
    private readonly Guid _studentId;
    private readonly Guid? _contextGroupId;
    private readonly List<string> _newlyUploadedStorageIds = [];

    // Nur gesetzt, wenn der Dialog aus einem Gruppen-Kontext (5.1, Dokumentation-Tab der
    // Lerngruppe) ohne festen Schüler geöffnet wird — vom Schüler-Tab aus (fester _studentId)
    // bleibt die Liste leer und die Auswahl unsichtbar.
    public List<StudentOption> StudentOptions { get; }
    public bool CanPickStudent => StudentOptions.Count > 0;
    [ObservableProperty] private StudentOption? _selectedStudent;
    [ObservableProperty] private string _studentError = "";

    [ObservableProperty] private string _typeName = DocumentationTypeDisplay.Options[0];
    [ObservableProperty] private string _dateText = DateOnly.FromDateTime(DateTime.Today).ToString("dd.MM.yyyy");
    [ObservableProperty] private string _title = "";
    [ObservableProperty] private string _content = "";
    [ObservableProperty] private bool _isConfidential;
    [ObservableProperty] private bool _excludeFromWebUntisSync;

    [ObservableProperty] private string _newParticipant = "";
    public ObservableCollection<string> Participants { get; } = [];

    [ObservableProperty] private int _lessonCount = 1;
    [ObservableProperty] private bool _absenceExcused;
    [ObservableProperty] private string _absenceReason = "";

    [ObservableProperty] private string _newMeasure = "";
    public ObservableCollection<string> Measures { get; } = [];
    [ObservableProperty] private string _reviewDateText = "";
    [ObservableProperty] private string _supportStatusName = SupportStatusDisplay.Options[0];

    // Elternanruf (nur Planung — Abhaken/Eindrücke laufen über ParentCallSessionDialog)
    [ObservableProperty] private string _newCallPoint = "";
    public ObservableCollection<string> CallPoints { get; } = [];

    // Elternbrief
    [ObservableProperty] private string _letterDraftContent = "";
    [ObservableProperty] private string _letterSentDateText = "";
    [ObservableProperty] private bool   _letterResponseReceived;
    [ObservableProperty] private string _letterResponseDateText = "";
    [ObservableProperty] private string _letterResponseNote = "";
    [ObservableProperty] private string _letterSentDateError = "";
    [ObservableProperty] private string _letterResponseDateError = "";

    // Anhänge (für alle Typen)
    public ObservableCollection<AttachmentItem> Attachments { get; } = [];
    [ObservableProperty] private string _attachmentError = "";

    // Labels zur Nachverfolgung (für alle Typen)
    [ObservableProperty] private string _newTag = "";
    public ObservableCollection<string> Tags { get; } = [];
    public string[] TagSuggestions => DocumentationTagDisplay.Suggestions;

    [ObservableProperty] private string _titleError = "";
    [ObservableProperty] private string _dateTextError = "";
    [ObservableProperty] private string _reviewDateTextError = "";

    public bool IsConversation => TypeName == "Gespräch";
    public bool IsAbsence => TypeName == "Fehlzeit";
    public bool IsSupportPlan => TypeName == "Förderplan";
    public bool IsParentCall => TypeName == "Elternanruf";
    public bool IsParentLetter => TypeName == "Elternbrief";

    public string[] TypeOptions => DocumentationTypeDisplay.Options;
    public string[] SupportStatusOptions => SupportStatusDisplay.Options;
    public string DialogTitle => _editing is null ? "Dokumentation hinzufügen" : "Dokumentation bearbeiten";
    public long MaxAttachmentSizeBytes => IAttachmentStorage.MaxSizeBytes;

    public Documentation? Result { get; private set; }

    public DocumentationDialogViewModel(Guid studentId, Documentation? editing, IAttachmentStorage attachmentStorage,
        List<StudentOption>? studentOptions = null, Guid? contextGroupId = null)
    {
        _studentId = studentId;
        _editing = editing;
        _attachmentStorage = attachmentStorage;
        _contextGroupId = contextGroupId;
        StudentOptions = studentOptions ?? [];
        if (CanPickStudent)
            SelectedStudent = StudentOptions.FirstOrDefault(s => s.Id == studentId);
        if (editing is null) return;

        TypeName = DocumentationTypeDisplay.Label(editing.Type);
        DateText = editing.Date.ToString("dd.MM.yyyy");
        Title = editing.Title;
        Content = editing.Content;
        IsConfidential = editing.IsConfidential;
        ExcludeFromWebUntisSync = editing.ExcludeFromWebUntisSync;
        foreach (var p in editing.Participants) Participants.Add(p);
        if (editing.AbsenceData is { } a)
        {
            LessonCount = a.LessonCount;
            AbsenceExcused = a.Excused;
            AbsenceReason = a.Reason ?? "";
        }
        if (editing.SupportData is { } s)
        {
            foreach (var m in s.Measures) Measures.Add(m);
            ReviewDateText = s.ReviewDate?.ToString("dd.MM.yyyy") ?? "";
            SupportStatusName = SupportStatusDisplay.Label(s.Status);
        }
        if (editing.ParentCallData is { } pc)
            foreach (var point in pc.Points) CallPoints.Add(point.Text);
        if (editing.ParentLetterData is { } pl)
        {
            LetterDraftContent = pl.DraftContent;
            LetterSentDateText = pl.SentDate?.ToString("dd.MM.yyyy") ?? "";
            LetterResponseReceived = pl.ResponseReceived;
            LetterResponseDateText = pl.ResponseDate?.ToString("dd.MM.yyyy") ?? "";
            LetterResponseNote = pl.ResponseNote;
        }
        foreach (var att in editing.Attachments)
            Attachments.Add(new AttachmentItem(att.StorageId, att.FileName, att.SizeBytes, att.UploadedAt));
        foreach (var tag in editing.Tags) Tags.Add(tag);
    }

    partial void OnTypeNameChanged(string value)
    {
        OnPropertyChanged(nameof(IsConversation));
        OnPropertyChanged(nameof(IsAbsence));
        OnPropertyChanged(nameof(IsSupportPlan));
        OnPropertyChanged(nameof(IsParentCall));
        OnPropertyChanged(nameof(IsParentLetter));
    }

    // ── Anhänge ────────────────────────────────────────────────────────────

    public void AddAttachment(string fileName, Stream content)
    {
        AttachmentError = "";
        if (content.Length > IAttachmentStorage.MaxSizeBytes)
        {
            AttachmentError = $"Datei zu groß (max. {IAttachmentStorage.MaxSizeBytes / 1024 / 1024} MB).";
            return;
        }
        var storageId = _attachmentStorage.Upload(fileName, content);
        _newlyUploadedStorageIds.Add(storageId);
        Attachments.Add(new AttachmentItem(storageId, fileName, content.Length, DateTime.UtcNow));
    }

    public Stream? OpenAttachment(AttachmentItem item) => _attachmentStorage.OpenRead(item.StorageId);

    [RelayCommand]
    private void RemoveAttachment(AttachmentItem? item)
    {
        if (item is null) return;
        _attachmentStorage.Delete(item.StorageId);
        _newlyUploadedStorageIds.Remove(item.StorageId);
        Attachments.Remove(item);
    }

    /// Vom Code-Behind beim Abbrechen aufgerufen: neu hochgeladene, nie gespeicherte Anhänge
    /// wieder entfernen, damit keine verwaisten Blobs in der Datenbank zurückbleiben.
    public void DiscardUnsavedAttachments()
    {
        foreach (var id in _newlyUploadedStorageIds) _attachmentStorage.Delete(id);
    }

    [RelayCommand]
    private void AddParticipant()
    {
        if (string.IsNullOrWhiteSpace(NewParticipant)) return;
        Participants.Add(NewParticipant.Trim());
        NewParticipant = "";
    }

    [RelayCommand]
    private void RemoveParticipant(string? p) { if (p is not null) Participants.Remove(p); }

    [RelayCommand]
    private void AddMeasure()
    {
        if (string.IsNullOrWhiteSpace(NewMeasure)) return;
        Measures.Add(NewMeasure.Trim());
        NewMeasure = "";
    }

    [RelayCommand]
    private void RemoveMeasure(string? m) { if (m is not null) Measures.Remove(m); }

    [RelayCommand]
    private void AddCallPoint()
    {
        if (string.IsNullOrWhiteSpace(NewCallPoint)) return;
        CallPoints.Add(NewCallPoint.Trim());
        NewCallPoint = "";
    }

    [RelayCommand]
    private void RemoveCallPoint(string? p) { if (p is not null) CallPoints.Remove(p); }

    [RelayCommand]
    private void AddTag()
    {
        if (string.IsNullOrWhiteSpace(NewTag)) return;
        var tag = NewTag.Trim();
        if (Tags.Contains(tag)) return;
        Tags.Add(tag);
        NewTag = "";
    }

    [RelayCommand]
    private void RemoveTag(string? t) { if (t is not null) Tags.Remove(t); }

    [RelayCommand]
    private void Save()
    {
        TitleError = ""; DateTextError = ""; ReviewDateTextError = ""; StudentError = "";
        LetterSentDateError = ""; LetterResponseDateError = "";
        var valid = true;

        if (CanPickStudent && SelectedStudent is null) { StudentError = "Schüler auswählen."; valid = false; }

        if (string.IsNullOrWhiteSpace(Title)) { TitleError = "Titel erforderlich."; valid = false; }

        if (!DateOnly.TryParseExact(DateText, "dd.MM.yyyy", null, DateTimeStyles.None, out var date))
        { DateTextError = "Format TT.MM.JJJJ."; valid = false; }

        DateOnly? reviewDate = null;
        if (IsSupportPlan && !string.IsNullOrWhiteSpace(ReviewDateText))
        {
            if (!DateOnly.TryParseExact(ReviewDateText, "dd.MM.yyyy", null, DateTimeStyles.None, out var r))
            { ReviewDateTextError = "Format TT.MM.JJJJ."; valid = false; }
            else reviewDate = r;
        }

        DateOnly? sentDate = null;
        if (IsParentLetter && !string.IsNullOrWhiteSpace(LetterSentDateText))
        {
            if (!DateOnly.TryParseExact(LetterSentDateText, "dd.MM.yyyy", null, DateTimeStyles.None, out var s))
            { LetterSentDateError = "Format TT.MM.JJJJ."; valid = false; }
            else sentDate = s;
        }

        DateOnly? responseDate = null;
        if (IsParentLetter && !string.IsNullOrWhiteSpace(LetterResponseDateText))
        {
            if (!DateOnly.TryParseExact(LetterResponseDateText, "dd.MM.yyyy", null, DateTimeStyles.None, out var r))
            { LetterResponseDateError = "Format TT.MM.JJJJ."; valid = false; }
            else responseDate = r;
        }

        if (!valid) return;

        var type = DocumentationTypeDisplay.FromLabel(TypeName);
        var effectiveStudentId = CanPickStudent ? SelectedStudent!.Id : _studentId;
        Result = _editing ?? new Documentation { StudentId = effectiveStudentId, GroupId = _contextGroupId };
        Result.Type = type;
        Result.Date = date;
        Result.Title = Title.Trim();
        Result.Content = (Content ?? "").Trim();
        // Das bewusste Speichern im vollständigen Dialog schließt einen im Sitzplan erzeugten
        // Schnellentwurf ab. Stunden- und Lesson-Bezug bleiben am bestehenden Objekt erhalten.
        Result.IsDraft = false;
        Result.IsConfidential = IsConfidential;
        Result.ExcludeFromWebUntisSync = ExcludeFromWebUntisSync;
        Result.Participants = type == DocumentationType.Conversation ? Participants.ToList() : [];
        Result.AbsenceData = type == DocumentationType.Absence
            ? new AbsenceData
            {
                LessonCount = LessonCount,
                Excused = AbsenceExcused,
                Reason = string.IsNullOrWhiteSpace(AbsenceReason) ? null : AbsenceReason.Trim(),
            }
            : null;
        Result.SupportData = type == DocumentationType.SupportPlan
            ? new SupportData
            {
                Measures = Measures.ToList(),
                ReviewDate = reviewDate,
                Status = SupportStatusDisplay.FromLabel(SupportStatusName),
            }
            : null;

        if (type == DocumentationType.ParentCall)
        {
            var existingPoints = _editing?.ParentCallData?.Points ?? [];
            Result.ParentCallData = new ParentCallData
            {
                // Punkte mit unverändertem Text behalten ihren Abhak-Status; neue/umbenannte
                // Punkte starten offen — das Abhaken selbst läuft über ParentCallSessionDialog.
                Points = CallPoints.Select(text =>
                    existingPoints.FirstOrDefault(p => p.Text == text) ?? new ParentCallPoint { Text = text }).ToList(),
                Impressions = _editing?.ParentCallData?.Impressions ?? "",
                IsConducted = _editing?.ParentCallData?.IsConducted ?? false,
                ConductedDate = _editing?.ParentCallData?.ConductedDate,
            };
        }
        else Result.ParentCallData = null;

        Result.ParentLetterData = type == DocumentationType.ParentLetter
            ? new ParentLetterData
            {
                DraftContent = (LetterDraftContent ?? "").Trim(),
                SentDate = sentDate,
                ResponseReceived = LetterResponseReceived,
                ResponseDate = responseDate,
                ResponseNote = (LetterResponseNote ?? "").Trim(),
            }
            : null;

        Result.Attachments = Attachments.Select(a => new DocumentAttachment
        {
            StorageId = a.StorageId, FileName = a.FileName, SizeBytes = a.SizeBytes, UploadedAt = a.UploadedAt,
        }).ToList();
        Result.Tags = Tags.ToList();
        // Nach erfolgreichem Speichern sollen diese Anhänge NICHT mehr beim Abbrechen-Cleanup
        // gelöscht werden — der Aufrufer speichert den Eintrag direkt im Anschluss an Save().
        _newlyUploadedStorageIds.Clear();
    }
}

public class AttachmentItem(string storageId, string fileName, long sizeBytes, DateTime uploadedAt)
{
    public const string HazardAssessmentSuffix = ".gbu.json";

    public string StorageId { get; } = storageId;
    public string FileName { get; } = fileName;
    public long SizeBytes { get; } = sizeBytes;
    public DateTime UploadedAt { get; } = uploadedAt;
    public string SizeDisplay => $"{SizeBytes / 1024.0:0} KB";
    /// Strukturierter Gefährdungsbeurteilungs-Anhang (siehe HazardAssessment) statt einer
    /// beliebigen hochgeladenen Datei — steuert im Anhang-Editor, ob "Öffnen"+"PDF" statt des
    /// generischen "Speichern" angeboten wird.
    public bool IsHazardAssessment => FileName.EndsWith(HazardAssessmentSuffix, StringComparison.OrdinalIgnoreCase);
}

public class TagChip(string text)
{
    public string Text { get; } = text;
    public string ColorHex { get; } = DocumentationTagDisplay.ColorHex(text);
}

// ── Listen-Eintrag mit Vertraulichkeits-Freigabe (5.1.3/5.4.1) ───────────────

public partial class DocumentationItem : ObservableObject
{
    public Documentation Model { get; }
    public string DateDisplay { get; }
    public string TypeLabel { get; }
    public bool IsConfidential { get; }
    public bool IsParentCall { get; }
    public bool HasAttachments { get; }
    public bool IsDraft { get; }
    public string StatusLabel { get; }
    public List<TagChip> TagChips { get; }
    /// Nur im Gruppen-Tab (5.1, GroupDocumentationTabViewModel) gefüllt — die Schüler-Detailansicht
    /// zeigt ohnehin nur Einträge eines einzelnen Schülers und braucht den Namen nicht.
    public string StudentName { get; }
    /// True, wenn der Eintrag keiner Gruppe zugeordnet ist oder der aktuell angezeigten Gruppe
    /// entspricht — false für Einträge aus einem anderen Unterricht desselben Schülers (werden im
    /// Gruppen-Tab optisch abgesetzt statt komplett ausgeblendet, siehe Nutzer-Feedback).
    public bool IsOwnGroup { get; }
    /// Name der Gruppe, aus der ein nicht-eigener Eintrag stammt (nur gesetzt, wenn !IsOwnGroup).
    public string OtherGroupLabel { get; }
    /// Dimmt Einträge aus anderen Lerngruppen im Gruppen-Tab, ohne sie zu verstecken.
    public double ContentOpacity => IsOwnGroup ? 1.0 : 0.55;

    [ObservableProperty] private bool _isRevealed;

    public DocumentationItem(Documentation d, string studentName = "", bool isOwnGroup = true, string otherGroupLabel = "")
    {
        Model = d;
        DateDisplay = d.Date.ToString("dd.MM.yyyy");
        TypeLabel = DocumentationTypeDisplay.Label(d.Type);
        IsConfidential = d.IsConfidential;
        IsRevealed = !d.IsConfidential;
        IsParentCall = d.Type == DocumentationType.ParentCall;
        HasAttachments = d.Attachments.Count > 0;
        IsDraft = d.IsDraft;
        StatusLabel = BuildStatusLabel(d);
        TagChips = d.Tags.Select(t => new TagChip(t)).ToList();
        StudentName = studentName;
        IsOwnGroup = isOwnGroup;
        OtherGroupLabel = otherGroupLabel;
    }

    private static string BuildStatusLabel(Documentation d) => d.Type switch
    {
        _ when d.IsDraft => "Nacharbeiten",
        DocumentationType.ParentCall when d.ParentCallData is { IsConducted: true } pc =>
            $"Durchgeführt am {pc.ConductedDate:dd.MM.yyyy}",
        DocumentationType.ParentCall => "Noch nicht durchgeführt",
        DocumentationType.ParentLetter when d.ParentLetterData is { } pl =>
            pl.ResponseReceived ? "Rückmeldung erhalten"
                : pl.SentDate.HasValue ? $"Versendet am {pl.SentDate:dd.MM.yyyy}"
                : "Noch nicht versendet",
        _ => "",
    };

    [RelayCommand] private void Reveal() => IsRevealed = true;
}