using System.Collections;
using System.Text;
using TMPro;
using UnityEngine;
using UnityEngine.UI;

namespace BaseGames.Dialogue
{
    /// <summary>
    /// 对话框 UI 组件（架构 14_NarrativeModule §5）。
    /// 挂载在 Canvas_Overlay 下的 DialogueBox 子对象。
    /// 负责打字机效果、头像显示、继续提示。
    /// </summary>
    public class DialogueUI : MonoBehaviour
    {
        [SerializeField] private GameObject  _rootPanel;
        [SerializeField] private TMP_Text    _speakerNameText;
        [SerializeField] private TMP_Text    _dialogueText;
        [SerializeField] private GameObject  _speakerNamePanel;  // 无名称时隐藏整个名称框
        [SerializeField] private GameObject  _continuePrompt;    // "▼" 图标，打字完成后显示
        [SerializeField] private Image       _speakerPortrait;   // 角色头像框

        private Coroutine   _typingCoroutine;
        private DialogueLine _currentLine;
        private const float  DefaultTypewriterDelay = 0.03f;

        /// <summary>当前是否仍在执行打字机效果。</summary>
        public bool IsTyping { get; private set; }

        // ── 公开 API ──────────────────────────────────────────────────────

        /// <summary>显示一行对话并开始打字机效果。</summary>
        public void ShowLine(DialogueLine line)
        {
            _currentLine = line;
            _rootPanel.SetActive(true);
            _continuePrompt.SetActive(false);

            // 说话人名称
            bool hasSpeaker = !string.IsNullOrEmpty(line.speakerNameKey);
            if (_speakerNamePanel != null) _speakerNamePanel.SetActive(hasSpeaker);
            if (hasSpeaker && _speakerNameText != null)
                _speakerNameText.text = line.speakerNameKey;

            // 头像
            if (_speakerPortrait != null)
            {
                _speakerPortrait.gameObject.SetActive(line.portraitSprite != null);
                if (line.portraitSprite != null) _speakerPortrait.sprite = line.portraitSprite;
            }

            // 开始打字机协程
            if (_typingCoroutine != null) StopCoroutine(_typingCoroutine);
            _typingCoroutine = StartCoroutine(TypeLine(line));
        }

        /// <summary>立即显示全部文字（跳过打字机效果）。</summary>
        public void SkipTyping()
        {
            if (!IsTyping) return;
            if (_typingCoroutine != null)
            {
                StopCoroutine(_typingCoroutine);
                _typingCoroutine = null;
            }
            if (_dialogueText != null)
                _dialogueText.text = _currentLine.textKey ?? "";
            IsTyping = false;
            if (_continuePrompt != null) _continuePrompt.SetActive(true);
        }

        /// <summary>隐藏对话框面板。</summary>
        public void Hide()
        {
            if (_rootPanel != null) _rootPanel.SetActive(false);
        }

        // ── 内部协程 ──────────────────────────────────────────────────────

        private IEnumerator TypeLine(DialogueLine line)
        {
            IsTyping = true;
            float delay = line.typewriterDelay > 0f ? line.typewriterDelay : DefaultTypewriterDelay;
            string text = line.textKey ?? "";

            // 性能：StringBuilder 避免每帧字符串分配（O(n²) → O(n)）
            var sb = new StringBuilder(text.Length);
            if (_dialogueText != null) _dialogueText.text = "";

            foreach (char c in text)
            {
                sb.Append(c);
                if (_dialogueText != null) _dialogueText.SetText(sb);   // TMP SetText(StringBuilder) 零分配
                yield return new WaitForSecondsRealtime(delay);
            }

            IsTyping = false;
            if (_continuePrompt != null) _continuePrompt.SetActive(true);
            _typingCoroutine = null;
        }
    }
}