using System.Collections.Concurrent;
using Telegram.Bot.Types.ReplyMarkups;
using Volcanic.AgenticCore.Abstractions.Ui;
using Volcanic.AgenticCore.Telegram.Rendering;

namespace Volcanic.AgenticCore.Telegram.Chats;

/// <summary>
/// <see cref="IUserInterface"/> for one chat: choices become inline keyboards (callback data <c>ui:&lt;id&gt;:&lt;index&gt;</c>),
/// free-text questions a ForceReply prompt answered by the chat's next plain message.
/// </summary>
public sealed class TelegramUi(TelegramSender sender, ChatRenderer renderer) : IUserInterface
{
    public const string CallbackPrefix = "ui:";
    private static readonly TimeSpan DefaultTimeout = TimeSpan.FromMinutes(10);

    private readonly ConcurrentDictionary<string, TaskCompletionSource<string?>> _choices = new();
    private TaskCompletionSource<string?>? _input;

    /// <summary>True while an <see cref="InputAsync"/> question waits for its answer.</summary>
    public bool IsWaitingForInput => Volatile.Read(ref _input) is { Task.IsCompleted: false };

    public async Task<string?> SelectAsync(string title, IReadOnlyList<string> options, UiRequestOptions? requestOptions, CancellationToken cancellationToken)
    {
        if (options.Count == 0) return null;
        var id = Guid.NewGuid().ToString("N")[..8];
        var tcs = new TaskCompletionSource<string?>(TaskCreationOptions.RunContinuationsAsynchronously);
        _choices[id] = tcs;
        try
        {
            var keyboard = new InlineKeyboardMarkup(options.Select((option, i) =>
                new[] { InlineKeyboardButton.WithCallbackData(option, $"{CallbackPrefix}{id}:{i}") }));
            var target = renderer.DeliveryChatId; // the edit below goes to the chat the question went to
            var messageId = await sender.SendTextAsync(target, title, keyboard, cancellationToken).ConfigureAwait(false);
            if (messageId is null) return null;

            var index = await WaitAsync(tcs, requestOptions, cancellationToken).ConfigureAwait(false);
            var choice = int.TryParse(index, out var i) && i >= 0 && i < options.Count ? options[i] : null;
            var outcome = choice is null ? "— no answer" : $"→ {choice}";
            await sender.EditHtmlAsync(target, messageId.Value, TelegramFormatter.Escape($"{title}\n{outcome}"), $"{title}\n{outcome}", CancellationToken.None)
                .ConfigureAwait(false);
            return choice;
        }
        finally
        {
            _choices.TryRemove(id, out _);
        }
    }

    public async Task<bool> ConfirmAsync(string title, string message, UiRequestOptions? requestOptions, CancellationToken cancellationToken) =>
        await SelectAsync($"{title}\n{message}", ["Yes", "No"], requestOptions, cancellationToken).ConfigureAwait(false) == "Yes";

    public async Task<string?> InputAsync(string title, string? placeholder, UiRequestOptions? requestOptions, CancellationToken cancellationToken)
    {
        var tcs = new TaskCompletionSource<string?>(TaskCreationOptions.RunContinuationsAsynchronously);
        Interlocked.Exchange(ref _input, tcs)?.TrySetResult(null); // one question at a time: a newer one cancels the older
        try
        {
            var markup = new ForceReplyMarkup { InputFieldPlaceholder = placeholder };
            if (await sender.SendTextAsync(renderer.DeliveryChatId, title, markup, cancellationToken).ConfigureAwait(false) is null) return null;
            return await WaitAsync(tcs, requestOptions, cancellationToken).ConfigureAwait(false);
        }
        finally
        {
            Interlocked.CompareExchange(ref _input, null, tcs);
        }
    }

    public void Notify(string message, NotifyKind kind = NotifyKind.Info) =>
        renderer.Post(new Abstractions.Events.AgentSessionEvent.Notification(message, kind));

    /// <summary>Status lines are not shown in Telegram; tool and retry progress is rendered from session events.</summary>
    public void SetStatus(string key, string? text) { }

    /// <summary>Resolve a pending choice from callback data. False when it is not ours or no longer pending.</summary>
    public bool TryResolveCallback(string data)
    {
        if (!data.StartsWith(CallbackPrefix, StringComparison.Ordinal)) return false;
        var parts = data[CallbackPrefix.Length..].Split(':');
        return parts.Length == 2 && _choices.TryGetValue(parts[0], out var tcs) && tcs.TrySetResult(parts[1]);
    }

    /// <summary>Answer a pending <see cref="InputAsync"/> question. False when none is pending.</summary>
    public bool TryResolveInput(string text) => Interlocked.Exchange(ref _input, null) is { } tcs && tcs.TrySetResult(text);

    private static async Task<string?> WaitAsync(TaskCompletionSource<string?> tcs, UiRequestOptions? requestOptions, CancellationToken cancellationToken)
    {
        using var timeout = new CancellationTokenSource(requestOptions?.Timeout ?? DefaultTimeout);
        using var linked = CancellationTokenSource.CreateLinkedTokenSource(timeout.Token, cancellationToken);
        await using var registration = linked.Token.Register(() => tcs.TrySetResult(null)).ConfigureAwait(false);
        return await tcs.Task.ConfigureAwait(false);
    }
}