using System.Collections.Generic;
using TMPro;
using UnityEngine;
using UnityEngine.UI;
using Yarn.Unity;

// Annotations only (not warnings): DialoguePresenterBase declares
// RunOptionsAsync as YarnTask<DialogueOption?>, so the override needs a
// nullable annotation context to match it without CS8632.
#nullable enable annotations

namespace NightclubArcadia.UI.Dialogue
{
    /// <summary>
    /// Yarn presenter that appends each line to a scrolling chat-style stream
    /// rather than replacing a single text box.
    /// </summary>
    public sealed class DialogueStreamPresenter : DialoguePresenterBase
    {
        [SerializeField] DialogueMessageRow messageRowPrefab;
        [SerializeField] RectTransform messageContainer;
        [SerializeField] ScrollRect scrollRect;
        [SerializeField] int maxRows = 100;
        [SerializeField] float lettersPerSecond = 60f;

        readonly List<DialogueMessageRow> rows = new List<DialogueMessageRow>();

        void Awake()
        {
            // Must exist before LineAdvancer.Start(), which does
            //     presenter.Typewriter?.ActionMarkupHandlers.Add(this);
            // to learn when a line has finished displaying. Leave Typewriter
            // null and that is a silent no-op: LineAdvancer never receives
            // OnLineDisplayComplete, its status never leaves LineBegan, and
            // pressing the advance key only ever hurries up the line — the
            // conversation can never move past the first message.
            Typewriter = new LetterTypewriter
            {
                CharactersPerSecond = lettersPerSecond,
            };
        }

        public override YarnTask OnDialogueStartedAsync()
        {
            ClearRows();
            return YarnTask.CompletedTask;
        }

        public override YarnTask OnDialogueCompleteAsync()
        {
            // DialogueTransitionController owns showing/hiding the panel.
            return YarnTask.CompletedTask;
        }

        public override async YarnTask RunLineAsync(LocalizedLine line, LineCancellationToken token)
        {
            if (messageRowPrefab == null || messageContainer == null)
            {
                Debug.LogError($"[{nameof(DialogueStreamPresenter)}] Missing messageRowPrefab or messageContainer.", this);
                return;
            }

            var row = Instantiate(messageRowPrefab, messageContainer);
            row.gameObject.SetActive(true);
            rows.Add(row);

            while (rows.Count > maxRows)
            {
                var oldest = rows[0];
                rows.RemoveAt(0);
                if (oldest != null)
                {
                    Destroy(oldest.gameObject);
                }
            }

            var text = line.TextWithoutCharacterName;
            row.SetContent(line.CharacterName, text.Text ?? string.Empty);

            // Delegate the reveal to Yarn's own typewriter rather than
            // hand-rolling maxVisibleCharacters. It drives the
            // IActionMarkupHandler lifecycle — including LineAdvancer's
            // OnLineDisplayComplete, which is what lets the advance key move to
            // the next line instead of only hurrying up the current one — and
            // it honours [pause] markup for free.
            //
            // TextElement is re-pointed at each new row; the typewriter itself
            // is reused so LineAdvancer's registration survives.
            if (Typewriter != null && row.BodyText != null)
            {
                Typewriter.TextElement = row.BodyText;
                Typewriter.PrepareForContent(text);
                await Typewriter.RunTypewriter(text, token.HurryUpToken).SuppressCancellationThrow();
            }

            // Deliberately no ContentWillDismiss/ContentDidDismiss: rows persist
            // in the stream, and ContentDidDismiss would blank the row by
            // resetting maxVisibleCharacters to 0.

            Canvas.ForceUpdateCanvases();
            if (scrollRect != null)
            {
                scrollRect.verticalNormalizedPosition = 0f;
            }

            if (!token.IsNextContentRequested)
            {
                await YarnTask.WaitUntilCanceled(token.NextContentToken).SuppressCancellationThrow();
            }
        }

        public override YarnTask<DialogueOption?> RunOptionsAsync(
            DialogueOption[] dialogueOptions,
            LineCancellationToken cancellationToken)
        {
            // Options are handled by DialogueStreamOptionsPresenter.
            return DialogueRunner.NoOptionSelected;
        }

        void ClearRows()
        {
            for (var i = 0; i < rows.Count; i++)
            {
                if (rows[i] != null)
                {
                    Destroy(rows[i].gameObject);
                }
            }

            rows.Clear();
        }
    }
}