using System.Threading;
using TMPro;
using UnityEngine;
using UnityEngine.UI;
using Yarn.Unity;
using Ichni.Story.UI;

namespace Ichni.Story.Dialogue
{
    /// <summary>
    /// 视觉小说（VN）风格的 Yarn 对话呈现器。
    /// <para>
    /// 职责：
    /// <list type="bullet">
    ///   <item>对话流控制：打字机效果、点击推进、等待选项。</item>
    ///   <item>将所有的 UI 引用委托给 <see cref="DialogUIPage"/> 进行管理。</item>
    /// </list>
    /// </para>
    /// </summary>
    public class VNDialoguePresenter : DialoguePresenterBase
    {
        [Header("UI 管理")]
        [Tooltip("负责当前对话界面的 UI Page 容器。如果为空，将尝试获取全局单例。")]
        [SerializeField] private DialogUIPage uiPage;

        [Header("打字效果")]
        [Tooltip("每秒显示的字符数。设为 0 则瞬间显示全文。")]
        [SerializeField] private float lettersPerSecond = 40f;

        // ── 私有状态 ─────────────────────────────────────────────────────────────

        /// <summary>
        /// 当前行的打字效果是否已完成。
        /// 用于区分"加速打字（第一次点击）"与"推进到下一行（第二次点击）"两个阶段。
        /// </summary>
        private bool _typewriterComplete;

        /// <summary>
        /// 是否处于快进状态（遇到选项或玩家再次点击时会打断）。
        /// </summary>
        private bool _isFastForwarding;

        /// <summary>
        /// 选项选择的异步结果来源。RunOptionsAsync 等待其 Task 完成，
        /// 点击按钮时 TrySetResult 触发完成。
        /// </summary>
        private YarnTaskCompletionSource<DialogueOption?> _optionTcs;

        /// <summary>
        /// 对应 StoryDialogueRoot 上的 DialogueRunner。
        /// </summary>
        private DialogueRunner _runner;

        private DialogUIPage Page => uiPage != null ? uiPage : DialogUIPage.instance;

        // ── 生命周期 ─────────────────────────────────────────────────────────────

        private void Awake()
        {
            _runner = GetComponent<DialogueRunner>();
            if (_runner == null)
                Debug.LogWarning("[VNDialoguePresenter] 未在同 GameObject 上找到 DialogueRunner。" +
                                 "请确认 VNDialoguePresenter 挂载在 StoryDialogueRoot 上。");
        }

        private void Start()
        {
            if (Page == null) return;

            // 启动时隐藏选项容器
            if (Page.choiceFrame != null) Page.choiceFrame.SetActive(false);

            // 注册推进按钮回调
            if (Page.advanceButton != null)
                Page.advanceButton.onClick.AddListener(OnAdvanceButtonClicked);
                
            // 注册快进按钮回调
            if (Page.fastForwardButton != null)
                Page.fastForwardButton.onClick.AddListener(OnFastForwardButtonClicked);
        }

        private void OnDestroy()
        {
            if (Page != null)
            {
                if (Page.advanceButton != null)
                    Page.advanceButton.onClick.RemoveListener(OnAdvanceButtonClicked);
                if (Page.fastForwardButton != null)
                    Page.fastForwardButton.onClick.RemoveListener(OnFastForwardButtonClicked);
            }
        }

        // ── DialoguePresenterBase 实现 ───────────────────────────────────────────

        public override async YarnTask OnDialogueStartedAsync()
        {
            if (Page != null)
            {
                var tcs = new YarnTaskCompletionSource<bool>();
                Page.PlayFadeIn(() => tcs.TrySetResult(true));
                await tcs.Task;
            }
        }

        public override async YarnTask RunLineAsync(LocalizedLine line, LineCancellationToken token)
        {
            if (Page == null) return;

            // 确保选项区不可见；台词区始终可见
            if (Page.choiceFrame != null) Page.choiceFrame.SetActive(false);

            // ── 说话者名称 ──
            bool hasSpeaker = !string.IsNullOrEmpty(line.CharacterName);
            if (Page.speakerContainer != null) Page.speakerContainer.SetActive(hasSpeaker);
            if (Page.speakerText != null) Page.speakerText.text = hasSpeaker ? line.CharacterName : string.Empty;

            // ── 立绘高亮 ──
            Page.portraitStage?.HighlightSpeaker(line.CharacterName);

            // ── 打字效果 ──
            string fullText = line.TextWithoutCharacterName.Text;
            _typewriterComplete = false;

            if (Page.dialogueText != null)
            {
                Page.dialogueText.text = fullText;
                Page.dialogueText.maxVisibleCharacters = 0;
            }

            if (_isFastForwarding)
            {
                // 瞬间显示全文
                if (Page.dialogueText != null) Page.dialogueText.maxVisibleCharacters = int.MaxValue;
                _typewriterComplete = true;

                // 极短的延迟，防止瞬间刷过几百句话造成卡顿，也给玩家微小的视觉感知
                await YarnTask.Delay(50).SuppressCancellationThrow();

                if (_isFastForwarding && _runner != null)
                {
                    _runner.RequestNextLine();
                }
            }
            else
            {
                // 正常逐字播放
                await TypewriterAsync(fullText, token.HurryUpToken);

                // 确保全文可见
                if (Page.dialogueText != null)
                    Page.dialogueText.maxVisibleCharacters = int.MaxValue;
                    
                _typewriterComplete = true;
            }

            // ── 等待玩家推进 ──
            await YarnTask.WaitUntilCanceled(token.NextContentToken).SuppressCancellationThrow();
        }

        public override async YarnTask<DialogueOption?> RunOptionsAsync(
            DialogueOption[] options,
            LineCancellationToken token)
        {
            if (Page == null) return null;

            // 遇到选项强制打断快进
            _isFastForwarding = false;

            // 清空台词区，准备显示选项
            if (Page.speakerContainer != null) Page.speakerContainer.SetActive(false);
            if (Page.dialogueText != null) Page.dialogueText.text = string.Empty;

            // 显示选项容器
            if (Page.choiceFrame != null) Page.choiceFrame.SetActive(true);

            _optionTcs = new YarnTaskCompletionSource<DialogueOption?>();

            WaitForExternalCancelAsync(token.NextContentToken).Forget();

            // ── 配置每个选项按钮 ──
            for (int i = 0; i < Page.choiceButtons.Length; i++)
            {
                if (Page.choiceButtons[i] == null) continue;

                if (i < options.Length)
                    Page.choiceButtons[i].Setup(options[i], opt => _optionTcs.TrySetResult(opt));
                else
                    Page.choiceButtons[i].Cleanup();
            }

            // ── 等待玩家选择 ──
            DialogueOption? selected = await _optionTcs.Task;

            // 清理所有按钮并隐藏选项容器
            foreach (ChoiceButton btn in Page.choiceButtons)
                btn?.Cleanup();

            if (Page.choiceFrame != null) Page.choiceFrame.SetActive(false);

            return selected;
        }

        public override async YarnTask OnDialogueCompleteAsync()
        {
            if (Page != null)
            {
                var tcs = new YarnTaskCompletionSource<bool>();
                Page.PlayFadeOut(() => tcs.TrySetResult(true));
                await tcs.Task;
            }
        }

        // ── 内部方法 ─────────────────────────────────────────────────────────────

        private void OnAdvanceButtonClicked()
        {
            // 如果玩家在快进时点击屏幕/推进键，则打断快进状态并停止当前动作
            if (_isFastForwarding)
            {
                _isFastForwarding = false;
                return;
            }

            if (_runner == null) return;

            if (!_typewriterComplete)
                _runner.RequestHurryUpLine(); // 第一次点击：跳过打字效果
            else
                _runner.RequestNextLine();    // 第二次点击：推进到下一行
        }

        private void OnFastForwardButtonClicked()
        {
            _isFastForwarding = true;
            
            if (_runner == null) return;

            // 立即跳过当前的等待状态
            if (!_typewriterComplete)
                _runner.RequestHurryUpLine();
            else
                _runner.RequestNextLine();
        }

        private async YarnTask TypewriterAsync(string text, CancellationToken hurryUpToken)
        {
            if (Page.dialogueText == null) return;

            if (lettersPerSecond <= 0f)
            {
                Page.dialogueText.maxVisibleCharacters = int.MaxValue;
                return;
            }

            int delayMs = Mathf.Max(1, Mathf.RoundToInt(1000f / lettersPerSecond));

            for (int i = 1; i <= text.Length; i++)
            {
                if (hurryUpToken.IsCancellationRequested) return;
                Page.dialogueText.maxVisibleCharacters = i;
                await YarnTask.Delay(delayMs, hurryUpToken).SuppressCancellationThrow();
                if (hurryUpToken.IsCancellationRequested) return;
            }
        }

        private async YarnTask WaitForExternalCancelAsync(CancellationToken externalToken)
        {
            await YarnTask.WaitUntilCanceled(externalToken).SuppressCancellationThrow();
            _optionTcs?.TrySetResult(null);
        }
    }
}