namespace BotPages.Core.Routing;

using System.Text.RegularExpressions;


/// <summary>
/// Реестр команд, доступных из любого места.
/// </summary>
internal sealed class CommandsRegistry
{
    private readonly List<Command> _commands = new();

    public List<Command> Commands => _commands;

    /// <summary>
    /// Зарегистрировать команду, ведущую на страницу.
    /// </summary>
    public CommandsRegistry Map<TPage>(string commandTemplate, bool publish = false, string? description = null) where TPage : Page
    {
        var pattern = ToRegex(commandTemplate);

        return Map(commandTemplate, (ctx, args, ct) => ctx.Navigation.GoToAsync<TPage>(ctx, ct), publish, description);
    }

    /// <summary>
    /// Зарегистрировать команду с кастомным обработчиком.
    /// </summary>
    public CommandsRegistry Map(string commandTemplate, CommandHandler handler, bool publish = false, string? description = null)
    {
        var pattern = ToRegex(commandTemplate);
        _commands.Add(new Command()
        {
            Name = ToCommandName(commandTemplate),
            Pattern = pattern,
            Handler = handler,
            Publish = publish,
            Description = string.IsNullOrWhiteSpace(description) ? null : description
        });
        return this;
    }

    /// <summary>
    /// Попробовать выполнить команду.
    /// </summary>
    public bool TryDispatch(PageContext ctx, string command, CancellationToken ct, out Task? task)
    {
        foreach (var cmd in _commands)
        {
            var match = cmd.Pattern.Match(command);
            if (match.Success)
            {
                // Собираем аргументы
                var args = cmd.Pattern.GetGroupNames()
                    .Where(n => n != "0")
                    .Select(n => new { n, v = match.Groups[n].Value })
                    .Where(x => !string.IsNullOrEmpty(x.v))
                    .ToDictionary(x => x.n, x => x.v);

                task = cmd.Handler(ctx, args, ct);
                return true;
            }
        }
        task = null;
        return false;
    }

    private static Regex ToRegex(string template)
    {
        // Простейшее преобразование шаблона: "/open {page} {id?}" -> Regex
        var escaped = Regex.Escape(template)
            .Replace("\\{", "{").Replace("\\}", "}");
        var pattern = "^" + escaped
            .Replace("{page}", "(?<page>\\S+)")
            .Replace("{id?}", "(?<id>\\S+)?") + "$";
        return new Regex(pattern, RegexOptions.Compiled | RegexOptions.IgnoreCase);
    }

    private static string ToCommandName(string template)
    {
        // Простейшее преобразование шаблона: "/open {page} {id?}" -> "/open"
        return template.Split(" ", StringSplitOptions.RemoveEmptyEntries).First().ToLowerInvariant();
    }
}