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

namespace LehrerApp.Desktop.ViewModels.Workload;

// ── Anzeige-Hilfen für die Enums (6.1) ──────────────────────────────────────

public static class WorkTaskStatusDisplay
{
    public static string Label(WorkTaskStatus s) => s switch
    {
        WorkTaskStatus.Open       => "Offen",
        WorkTaskStatus.InProgress => "In Bearbeitung",
        WorkTaskStatus.Done       => "Erledigt",
        _                         => s.ToString(),
    };

    public static string ColorHex(WorkTaskStatus s) => s switch
    {
        WorkTaskStatus.Open       => "#9E9E9E",
        WorkTaskStatus.InProgress => "#1976D2",
        WorkTaskStatus.Done       => "#43A047",
        _                         => "#9E9E9E",
    };

    // Klick auf die Status-Kachel wechselt reihum (6.1.3).
    public static WorkTaskStatus Next(WorkTaskStatus s) => s switch
    {
        WorkTaskStatus.Open       => WorkTaskStatus.InProgress,
        WorkTaskStatus.InProgress => WorkTaskStatus.Done,
        _                         => WorkTaskStatus.Open,
    };
}

public static class TaskCategoryDisplay
{
    public static string Label(TaskCategory c) => c switch
    {
        TaskCategory.Correction  => "Korrektur",
        TaskCategory.Preparation => "Vorbereitung",
        TaskCategory.Admin       => "Verwaltung",
        TaskCategory.Meeting     => "Besprechung",
        TaskCategory.Other       => "Sonstiges",
        _                        => c.ToString(),
    };

    public static string[] Options { get; } = Enum.GetValues<TaskCategory>().Select(Label).ToArray();

    public static TaskCategory FromLabel(string? label) =>
        Enum.GetValues<TaskCategory>().FirstOrDefault(c => Label(c) == label, TaskCategory.Other);
}

// ── Aufgabenliste (6.1.1, 6.1.3) ─────────────────────────────────────────────

public partial class WorkTaskListViewModel : ObservableObject
{
    private readonly IWorkTaskRepository _tasks;
    private readonly IGroupRepository _groups;
    private readonly ITimeEntryRepository _timeEntries;

    public const string AllFilter = "Alle";
    public const string ActiveFilter = "Offene Aufgaben";
    public const string DoneFilter = "Erledigt";
    public const string NoGroupFilter = "Ohne Gruppe";

    [ObservableProperty] private string _statusFilter = ActiveFilter;
    [ObservableProperty] private string _categoryFilter = AllFilter;
    [ObservableProperty] private string _groupFilter = AllFilter;

    public List<string> StatusFilterOptions { get; } = [ActiveFilter, AllFilter, DoneFilter];
    public List<string> CategoryFilterOptions { get; } = [AllFilter, .. TaskCategoryDisplay.Options];
    public ObservableCollection<string> GroupFilterOptions { get; } = [AllFilter, NoGroupFilter];

    public ObservableCollection<WorkTaskListItem> Tasks { get; } = [];
    public string CountSummary => $"{Tasks.Count} Aufgabe(n)";

    public Func<WorkTask?, Task<WorkTask?>>? OnEditTask { get; set; }

    private Dictionary<Guid, string> _groupNames = [];

    public WorkTaskListViewModel(IWorkTaskRepository tasks, IGroupRepository groups,
        ITimeEntryRepository timeEntries)
    {
        _tasks = tasks;
        _groups = groups;
        _timeEntries = timeEntries;
        Load();
    }

    partial void OnStatusFilterChanged(string value) => Refresh();
    partial void OnCategoryFilterChanged(string value) => Refresh();
    partial void OnGroupFilterChanged(string value) => Refresh();

    public void Load()
    {
        var groups = _groups.GetAll(includeInactive: true);
        _groupNames = groups.ToDictionary(g => g.Id, g => g.Name);

        GroupFilterOptions.Clear();
        GroupFilterOptions.Add(AllFilter);
        GroupFilterOptions.Add(NoGroupFilter);
        foreach (var name in groups.Select(g => g.Name).OrderBy(n => n))
            GroupFilterOptions.Add(name);

        Refresh();
    }

    private void Refresh()
    {
        Tasks.Clear();
        var all = _tasks.GetAll().AsEnumerable();

        all = StatusFilter switch
        {
            ActiveFilter => all.Where(t => t.Status != WorkTaskStatus.Done),
            DoneFilter   => all.Where(t => t.Status == WorkTaskStatus.Done),
            _            => all,
        };

        if (CategoryFilter != AllFilter)
        {
            var category = TaskCategoryDisplay.FromLabel(CategoryFilter);
            all = all.Where(t => t.Category == category);
        }

        if (GroupFilter == NoGroupFilter)
            all = all.Where(t => t.GroupId is null);
        else if (GroupFilter != AllFilter)
            all = all.Where(t => t.GroupId.HasValue && _groupNames.GetValueOrDefault(t.GroupId.Value) == GroupFilter);

        // Fälligkeit: fällige zuerst, unbefristete ans Ende (6.1.1).
        foreach (var t in all.OrderBy(t => t.DueDate ?? DateOnly.MaxValue).ThenBy(t => t.Title))
        {
            // Ist-Zeit (6.2.4): Summe aller mit der Aufgabe verknüpften Zeiteinträge.
            var actualMinutes = _timeEntries.GetByTask(t.Id).Sum(e => e.DurationMinutes);
            Tasks.Add(new WorkTaskListItem(t, _groupNames.GetValueOrDefault(t.GroupId ?? Guid.Empty), actualMinutes));
        }

        OnPropertyChanged(nameof(CountSummary));
    }

    [RelayCommand]
    private async Task AddTask()
    {
        if (OnEditTask is null) return;
        var result = await OnEditTask(null);
        if (result is null) return;
        _tasks.Save(result);
        Refresh();
    }

    [RelayCommand]
    private async Task EditTask(WorkTaskListItem? item)
    {
        if (item is null || OnEditTask is null) return;
        var result = await OnEditTask(item.Model);
        if (result is null) return;
        _tasks.Save(result);
        Refresh();
    }

    [RelayCommand]
    private void CycleStatus(WorkTaskListItem? item)
    {
        if (item is null) return;
        item.Model.Status = WorkTaskStatusDisplay.Next(item.Model.Status);
        _tasks.Save(item.Model);
        Refresh();
    }

    [RelayCommand]
    private void DeleteTask(WorkTaskListItem? item)
    {
        if (item is null) return;
        _tasks.Delete(item.Model.Id);
        Refresh();
    }
}

public class WorkTaskListItem(WorkTask model, string? groupName, int actualMinutes = 0)
{
    public WorkTask Model { get; } = model;
    public string Title => Model.Title;
    public string CategoryLabel => TaskCategoryDisplay.Label(Model.Category);
    public string GroupName => groupName ?? "";
    public string DueDateDisplay => Model.DueDate?.ToString("dd.MM.yyyy", CultureInfo.InvariantCulture) ?? "";
    public bool IsOverdue => Model.DueDate is { } d && d < DateOnly.FromDateTime(DateTime.Today)
        && Model.Status != WorkTaskStatus.Done;
    public string DueDateColorHex => IsOverdue ? "#D32F2F" : "#9E9E9E";
    public string StatusLabel => WorkTaskStatusDisplay.Label(Model.Status);
    public string StatusColorHex => WorkTaskStatusDisplay.ColorHex(Model.Status);
    public string EstimatedMinutesDisplay => Model.EstimatedMinutes is { } m ? $"{m} min" : "";

    // Ist-Zeit vs. Schätzung (6.2.4) — nur anzeigen, wenn tatsächlich etwas erfasst wurde.
    public bool HasActualTime => actualMinutes > 0;
    public string ActualVsEstimateDisplay => Model.EstimatedMinutes is { } estimate
        ? $"{actualMinutes} / {estimate} min erfasst"
        : $"{actualMinutes} min erfasst";
}

// ── Dialog: Aufgabe anlegen/bearbeiten (6.1.2) ───────────────────────────────

public partial class AddEditWorkTaskDialogViewModel : ObservableObject
{
    private readonly WorkTask? _source;

    [ObservableProperty] private string _title = "";
    [ObservableProperty] private string _selectedCategory = TaskCategoryDisplay.Options[0];
    [ObservableProperty] private LearningGroup? _selectedGroup;
    [ObservableProperty] private string _dueDateText = "";
    [ObservableProperty] private string _estimatedMinutesText = "";
    [ObservableProperty] private string _notes = "";
    [ObservableProperty] private string _titleError = "";
    [ObservableProperty] private string _dueDateError = "";
    [ObservableProperty] private string _estimatedMinutesError = "";

    public string DialogTitle => _source is null ? "Aufgabe anlegen" : "Aufgabe bearbeiten";
    public List<string> CategoryOptions { get; } = [.. TaskCategoryDisplay.Options];
    public List<LearningGroup> Groups { get; }
    public WorkTask? Result { get; private set; }

    public AddEditWorkTaskDialogViewModel(WorkTask? source, List<LearningGroup> groups)
    {
        _source = source;
        Groups = groups;
        if (source is null) return;

        Title = source.Title;
        SelectedCategory = TaskCategoryDisplay.Label(source.Category);
        SelectedGroup = source.GroupId is { } id ? groups.FirstOrDefault(g => g.Id == id) : null;
        DueDateText = source.DueDate?.ToString("dd.MM.yyyy", CultureInfo.InvariantCulture) ?? "";
        EstimatedMinutesText = source.EstimatedMinutes?.ToString(CultureInfo.InvariantCulture) ?? "";
        Notes = source.Notes ?? "";
    }

    [RelayCommand]
    private void Save()
    {
        TitleError = ""; DueDateError = ""; EstimatedMinutesError = "";
        var valid = true;

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

        DateOnly? dueDate = null;
        if (!string.IsNullOrWhiteSpace(DueDateText))
        {
            if (!DateOnly.TryParseExact(DueDateText, "dd.MM.yyyy", null, DateTimeStyles.None, out var d))
            { DueDateError = "Format TT.MM.JJJJ."; valid = false; }
            else dueDate = d;
        }

        int? estimatedMinutes = null;
        if (!string.IsNullOrWhiteSpace(EstimatedMinutesText))
        {
            if (!int.TryParse(EstimatedMinutesText, out var m) || m <= 0)
            { EstimatedMinutesError = "Ganze Zahl > 0 erwartet."; valid = false; }
            else estimatedMinutes = m;
        }

        if (!valid) return;

        Result = new WorkTask
        {
            Id               = _source?.Id ?? Guid.NewGuid(),
            Title            = Title.Trim(),
            Category         = TaskCategoryDisplay.FromLabel(SelectedCategory),
            GroupId          = SelectedGroup?.Id,
            DueDate          = dueDate,
            EstimatedMinutes = estimatedMinutes,
            Status           = _source?.Status ?? WorkTaskStatus.Open,
            Notes            = string.IsNullOrWhiteSpace(Notes) ? null : Notes.Trim(),
            CreatedAt        = _source?.CreatedAt ?? DateTime.UtcNow,
        };
    }
}

// ── Zeiterfassung (6.2) ──────────────────────────────────────────────────────

public partial class TimeTrackingViewModel : ObservableObject
{
    private readonly ITimeEntryRepository _entries;
    private readonly IWorkTaskRepository _tasks;

    public const string NoTaskOption = "Keine Aufgabe";

    [ObservableProperty] private bool _isTimerRunning;
    [ObservableProperty] private DateTime? _timerStartedAt;
    [ObservableProperty] private WorkTask? _selectedTimerTask;
    [ObservableProperty] private string _selectedTimerCategory = TaskCategoryDisplay.Options[0];

    public List<string> CategoryOptions { get; } = [.. TaskCategoryDisplay.Options];
    public List<WorkTask> OpenTasks { get; private set; } = [];
    public string RunningSinceDisplay => TimerStartedAt is { } started
        ? $"Läuft seit {started:HH:mm} Uhr"
        : "";

    public ObservableCollection<TimeEntryListItem> WeekEntries { get; } = [];
    public ObservableCollection<CategoryWeekSummary> CategorySummaries { get; } = [];
    public string TotalWeekMinutesDisplay => $"{WeekEntries.Sum(e => e.Model.DurationMinutes)} min diese Woche";

    public Func<Task<TimeEntry?>>? OnAddEntry { get; set; }

    public TimeTrackingViewModel(ITimeEntryRepository entries, IWorkTaskRepository tasks)
    {
        _entries = entries;
        _tasks = tasks;
        Load();
    }

    partial void OnSelectedTimerTaskChanged(WorkTask? value)
    {
        if (value is not null) SelectedTimerCategory = TaskCategoryDisplay.Label(value.Category);
    }

    public void Load()
    {
        OpenTasks = _tasks.GetAll().Where(t => t.Status != WorkTaskStatus.Done).ToList();
        OnPropertyChanged(nameof(OpenTasks));
        Refresh();
    }

    private void Refresh()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var monday = today.AddDays(-((int)today.DayOfWeek + 6) % 7);
        var sunday = monday.AddDays(6);

        var weekEntries = _entries.GetByDateRange(monday, sunday);
        var taskTitles = _tasks.GetAll().ToDictionary(t => t.Id, t => t.Title);

        WeekEntries.Clear();
        foreach (var e in weekEntries.OrderByDescending(e => e.Date).ThenByDescending(e => e.StartTime))
            WeekEntries.Add(new TimeEntryListItem(e, e.TaskId is { } id ? taskTitles.GetValueOrDefault(id) : null));

        CategorySummaries.Clear();
        var maxMinutes = weekEntries.Count > 0
            ? weekEntries.GroupBy(e => e.Category).Max(g => g.Sum(e => e.DurationMinutes))
            : 0;
        foreach (var group in weekEntries.GroupBy(e => e.Category).OrderByDescending(g => g.Sum(e => e.DurationMinutes)))
        {
            var minutes = group.Sum(e => e.DurationMinutes);
            CategorySummaries.Add(new CategoryWeekSummary(
                string.IsNullOrWhiteSpace(group.Key) ? "Ohne Kategorie" : group.Key,
                minutes, maxMinutes > 0 ? minutes / (double)maxMinutes : 0));
        }

        OnPropertyChanged(nameof(TotalWeekMinutesDisplay));
    }

    [RelayCommand]
    private void StartTimer()
    {
        IsTimerRunning = true;
        TimerStartedAt = DateTime.Now;
        OnPropertyChanged(nameof(RunningSinceDisplay));
    }

    [RelayCommand]
    private void StopTimer()
    {
        if (TimerStartedAt is not { } startedAt) return;
        var endedAt = DateTime.Now;
        var minutes = Math.Max(1, (int)Math.Round((endedAt - startedAt).TotalMinutes));

        _entries.Save(new TimeEntry
        {
            TaskId          = SelectedTimerTask?.Id,
            Category        = SelectedTimerCategory,
            GroupId         = SelectedTimerTask?.GroupId,
            Date            = DateOnly.FromDateTime(startedAt),
            StartTime       = TimeOnly.FromDateTime(startedAt),
            EndTime         = TimeOnly.FromDateTime(endedAt),
            DurationMinutes = minutes,
        });

        IsTimerRunning = false;
        TimerStartedAt = null;
        OnPropertyChanged(nameof(RunningSinceDisplay));
        Refresh();
    }

    [RelayCommand]
    private async Task AddEntry()
    {
        if (OnAddEntry is null) return;
        var result = await OnAddEntry();
        if (result is null) return;
        _entries.Save(result);
        Refresh();
    }

    [RelayCommand]
    private void DeleteEntry(TimeEntryListItem? item)
    {
        if (item is null) return;
        _entries.Delete(item.Model.Id);
        Refresh();
    }
}

public class TimeEntryListItem(TimeEntry model, string? taskTitle)
{
    public TimeEntry Model { get; } = model;
    public string DateDisplay => Model.Date.ToString("dd.MM.yyyy", CultureInfo.InvariantCulture);
    public string Category => string.IsNullOrWhiteSpace(Model.Category) ? "Ohne Kategorie" : Model.Category;
    public string TaskTitle => taskTitle ?? "";
    public string CategoryAndTaskDisplay => string.IsNullOrEmpty(TaskTitle) ? Category : $"{Category} · {TaskTitle}";
    public string DurationDisplay => $"{Model.DurationMinutes} min";
    public string Description => Model.Description ?? "";
}

public class CategoryWeekSummary(string category, int minutes, double barFraction)
{
    public string Category { get; } = category;
    public string MinutesDisplay { get; } = $"{minutes} min";
    public double BarFraction { get; } = barFraction;
}

// ── Dialog: Zeiteintrag nacherfassen (6.2.2) ─────────────────────────────────

public partial class AddTimeEntryDialogViewModel : ObservableObject
{
    [ObservableProperty] private string _dateText = DateTime.Today.ToString("dd.MM.yyyy", CultureInfo.InvariantCulture);
    [ObservableProperty] private string _selectedCategory = TaskCategoryDisplay.Options[0];
    [ObservableProperty] private WorkTask? _selectedTask;
    [ObservableProperty] private string _startTimeText = "";
    [ObservableProperty] private string _endTimeText = "";
    [ObservableProperty] private string _durationText = "";
    [ObservableProperty] private string _description = "";
    [ObservableProperty] private string _dateError = "";
    [ObservableProperty] private string _timeError = "";

    public List<string> CategoryOptions { get; } = [.. TaskCategoryDisplay.Options];
    public List<WorkTask> Tasks { get; }
    public TimeEntry? Result { get; private set; }

    public AddTimeEntryDialogViewModel(List<WorkTask> tasks) => Tasks = tasks;

    partial void OnSelectedTaskChanged(WorkTask? value)
    {
        if (value is not null) SelectedCategory = TaskCategoryDisplay.Label(value.Category);
    }

    [RelayCommand]
    private void Save()
    {
        DateError = ""; TimeError = "";
        var valid = true;

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

        TimeOnly? start = null, end = null;
        int? duration = null;

        if (!string.IsNullOrWhiteSpace(DurationText))
        {
            if (!int.TryParse(DurationText, out var m) || m <= 0)
            { TimeError = "Dauer: ganze Zahl > 0 erwartet."; valid = false; }
            else duration = m;
        }
        else if (!string.IsNullOrWhiteSpace(StartTimeText) || !string.IsNullOrWhiteSpace(EndTimeText))
        {
            if (!TimeOnly.TryParseExact(StartTimeText, "HH:mm", null, DateTimeStyles.None, out var s)
                || !TimeOnly.TryParseExact(EndTimeText, "HH:mm", null, DateTimeStyles.None, out var e)
                || e <= s)
            { TimeError = "Format HH:mm, Ende muss nach Beginn liegen."; valid = false; }
            else { start = s; end = e; duration = (int)(e - s).TotalMinutes; }
        }
        else { TimeError = "Dauer oder Von/Bis erforderlich."; valid = false; }

        if (!valid) return;

        Result = new TimeEntry
        {
            TaskId          = SelectedTask?.Id,
            Category        = SelectedCategory,
            GroupId         = SelectedTask?.GroupId,
            Date            = date,
            StartTime       = start,
            EndTime         = end,
            DurationMinutes = duration!.Value,
            Description     = string.IsNullOrWhiteSpace(Description) ? null : Description.Trim(),
        };
    }
}

// ── Container: Arbeitszeit-Seite mit Tabs "Aufgaben"/"Zeiterfassung" ─────────

public partial class WorkloadViewModel(WorkTaskListViewModel tasks, TimeTrackingViewModel timeTracking) : ObservableObject
{
    [ObservableProperty] private int _activeTabIndex;

    public WorkTaskListViewModel Tasks { get; } = tasks;
    public TimeTrackingViewModel TimeTracking { get; } = timeTracking;
}