namespace MeetingAssistant.Hotkeys;

[Flags]
public enum HotkeyModifiers : uint
{
    None = 0,
    Alt = 0x0001,
    Control = 0x0002,
    Shift = 0x0004,
    Windows = 0x0008
}

public sealed record HotkeyDefinition(HotkeyModifiers Modifiers, uint VirtualKey)
{
    public static HotkeyDefinition Parse(string value)
    {
        if (string.IsNullOrWhiteSpace(value))
        {
            throw new ArgumentException("Hotkey cannot be empty.", nameof(value));
        }

        var modifiers = HotkeyModifiers.None;
        uint? virtualKey = null;

        foreach (var rawPart in value.Split('+', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries))
        {
            var part = rawPart.ToUpperInvariant();
            modifiers |= part switch
            {
                "CTRL" or "CONTROL" => HotkeyModifiers.Control,
                "ALT" => HotkeyModifiers.Alt,
                "SHIFT" => HotkeyModifiers.Shift,
                "WIN" or "WINDOWS" => HotkeyModifiers.Windows,
                _ => HotkeyModifiers.None
            };

            if (modifiers.HasFlagForToken(part))
            {
                continue;
            }

            virtualKey = ParseVirtualKey(part);
        }

        return virtualKey is null
            ? throw new FormatException($"Hotkey '{value}' does not contain a key.")
            : new HotkeyDefinition(modifiers, virtualKey.Value);
    }

    private static uint ParseVirtualKey(string part)
    {
        if (part.Length == 1 && char.IsLetterOrDigit(part[0]))
        {
            return part[0];
        }

        if (part.Length is 2 or 3 && part[0] == 'F' && int.TryParse(part[1..], out var functionKey) && functionKey is >= 1 and <= 24)
        {
            return (uint)(0x70 + functionKey - 1);
        }

        throw new FormatException($"Unsupported hotkey key '{part}'.");
    }
}

file static class HotkeyModifierExtensions
{
    public static bool HasFlagForToken(this HotkeyModifiers _, string token)
    {
        return token is "CTRL" or "CONTROL" or "ALT" or "SHIFT" or "WIN" or "WINDOWS";
    }
}