using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.SemanticKernel.ChatCompletion;
using YamlDotNet.Serialization;
using YamlDotNet.Serialization.NamingConventions;

namespace AI.Models.Store
{
    /// <summary>
    /// 会话存储序列化用的 DTO（YAML 根为 entries 列表）
    /// </summary>
    public class ConversationStoreDto
    {
        public List<ConversationEntryDto> Entries { get; set; } = new();
    }

    /// <summary>
    /// 单条存储条目的 DTO
    /// </summary>
    public class ConversationEntryDto
    {
        public string Kind { get; set; } = string.Empty;
        public string? Role { get; set; }
        public string? Content { get; set; }
        public string? Type { get; set; }
        public string? Payload { get; set; }
    }

    /// <summary>
    /// 会话级结构化存储，作为 UI 与 Prompt 构建的唯一事实来源。
    /// 持有有序的 ConversationEntry 列表，支持追加文本与特殊消息。
    /// 每个 ChatSession 持有一份 ConversationStore 实例。
    /// </summary>
    public class ConversationStore
    {
        private readonly List<ConversationEntry> _entries = new();
        private static readonly ISerializer _yamlSerializer = new SerializerBuilder()
            .WithNamingConvention(CamelCaseNamingConvention.Instance)
            .Build();
        private static readonly IDeserializer _yamlDeserializer = new DeserializerBuilder()
            .WithNamingConvention(CamelCaseNamingConvention.Instance)
            .IgnoreUnmatchedProperties()
            .Build();

        /// <summary>
        /// 有序条目列表（只读视图）
        /// </summary>
        public IReadOnlyList<ConversationEntry> Entries => _entries;

        /// <summary>
        /// 存储内容变更时触发（用于持久化层按需保存）
        /// </summary>
        public event EventHandler? StoreChanged;

        /// <summary>
        /// 追加一条文本消息
        /// </summary>
        public void AppendText(AuthorRole role, string content)
        {
            _entries.Add(new TextConversationEntry(role, content ?? string.Empty));
            StoreChanged?.Invoke(this, EventArgs.Empty);
        }

        /// <summary>
        /// 追加一条特殊消息（type + YAML 载荷）
        /// </summary>
        public void AppendSpecial(string type, string yamlPayload)
        {
            _entries.Add(new SpecialConversationEntry(type ?? string.Empty, yamlPayload ?? string.Empty));
            StoreChanged?.Invoke(this, EventArgs.Empty);
        }

        /// <summary>
        /// 清空存储（用于测试或重置）
        /// </summary>
        public void Clear()
        {
            _entries.Clear();
        }

        /// <summary>
        /// 移除最后一条条目（用于回滚等）
        /// </summary>
        /// <returns>是否移除了条目</returns>
        public bool RemoveLast()
        {
            if (_entries.Count == 0) return false;
            _entries.RemoveAt(_entries.Count - 1);
            return true;
        }

        /// <summary>
        /// 条目数量
        /// </summary>
        public int Count => _entries.Count;

        /// <summary>
        /// 序列化为 YAML 字符串（仅 entries 列表，用于嵌入会话文件或单独观察）
        /// </summary>
        public string ToYaml()
        {
            var dto = new ConversationStoreDto
            {
                Entries = ConversationEntryMapper.ToDtoList(_entries)
            };
            return _yamlSerializer.Serialize(dto);
        }

        /// <summary>
        /// 从 YAML 字符串加载并替换当前存储内容（先清空再按序追加）
        /// </summary>
        public void LoadFromYaml(string yaml)
        {
            if (string.IsNullOrWhiteSpace(yaml))
            {
                Clear();
                return;
            }
            var dto = _yamlDeserializer.Deserialize<ConversationStoreDto>(yaml);
            LoadFromEntries(dto?.Entries);
        }

        /// <summary>
        /// 从 DTO 条目列表加载并替换当前存储（先清空再按序追加），用于会话文件反序列化
        /// </summary>
        public void LoadFromEntries(IEnumerable<ConversationEntryDto>? entries)
        {
            _entries.Clear();
            _entries.AddRange(ConversationEntryMapper.ToEntryList(entries));
        }
    }
}