using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.IO;
using System.Linq;
using ClaudeDo.Ui.Localization;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;

namespace ClaudeDo.Ui.ViewModels.Modals;

/// <summary>One cheat sheet: title from the file's leading <c># </c> heading, body is the rest.</summary>
public sealed record CheatSheet(string Key, string Title, string Body);

/// <summary>
/// Backs the non-modal cheat-sheet window (Help → Cheat Sheets). Content lives as markdown
/// under <c>Assets/CheatSheets/*.md</c> (embedded resources) and is rendered by the existing
/// <c>MarkdownView</c>,
/// so a new sheet is a new file — but the key list here stays explicit to keep the order
/// deterministic and a missing resource visible instead of silently absent.
/// </summary>
public partial class CheatSheetsViewModel : ViewModelBase
{
    private static readonly string[] Keys =
        ["git", "conventional-commits", "claude-cli", "claude-config", "dotnet-cli", "powershell"];

    public ObservableCollection<CheatSheet> Sheets { get; } = [];

    [ObservableProperty]
    private CheatSheet? _selectedSheet;

    /// <summary>Keeps the window above the shell so it can sit docked at a screen edge.</summary>
    [ObservableProperty]
    private bool _isPinned;

    public Action? CloseAction { get; set; }

    public CheatSheetsViewModel()
    {
        foreach (var key in Keys) Sheets.Add(Load(key));
        SelectedSheet = Sheets.FirstOrDefault();
    }

    /// <summary>Preselects a sheet by key; unknown keys keep the current selection.</summary>
    public void Select(string key)
    {
        var sheet = Sheets.FirstOrDefault(s => s.Key == key);
        if (sheet is not null) SelectedSheet = sheet;
    }

    [RelayCommand]
    private void Close() => CloseAction?.Invoke();

    private static CheatSheet Load(string key)
    {
        var assembly = typeof(CheatSheetsViewModel).Assembly;
        // Match by suffix rather than composing the logical name from RootNamespace — the
        // prefix is a build detail, and a rename shouldn't silently blank the sheet.
        var name = assembly.GetManifestResourceNames()
            .FirstOrDefault(n => n.EndsWith($".CheatSheets.{key}.md", StringComparison.Ordinal));
        var stream = name is null ? null : assembly.GetManifestResourceStream(name);
        if (stream is null)
            return new CheatSheet(key, key, Loc.T("modals.cheatSheets.missing", $"{key}.md"));

        using var reader = new StreamReader(stream);
        var text = reader.ReadToEnd().Replace("\r\n", "\n");

        // The window shows the title in its own selector, so strip the leading heading
        // rather than rendering it a second time inside the body.
        var lines = new List<string>(text.Split('\n'));
        var title = key;
        var first = lines.FindIndex(l => !string.IsNullOrWhiteSpace(l));
        if (first >= 0 && lines[first].StartsWith("# ", StringComparison.Ordinal))
        {
            title = lines[first][2..].Trim();
            lines.RemoveRange(0, first + 1);
        }
        return new CheatSheet(key, title, string.Join('\n', lines).Trim());
    }
}