using System.Collections.Generic;
using System;
using AI.Models.Form;
using YamlDotNet.Serialization;
using YamlDotNet.Serialization.NamingConventions;

namespace AI.Utils
{
    /// <summary>
    /// 将表单定义序列化为 YAML，供 LLM 上下文、追踪、调试等使用。
    /// </summary>
    public static class FormSchemaYamlGenerator
    {
        /// <summary>
        /// System 消息中「表单 Schema YAML」块的开始标记（存在则整块替换，避免重复追加）。
        /// </summary>
        public const string FormsYamlBlockStart = "\n\n# --- 当前可用表单 Schema (YAML) ---\n";

        /// <summary>
        /// System 消息中「表单 Schema YAML」块的结束标记。
        /// </summary>
        public const string FormsYamlBlockEnd = "\n# --- 结束 ---";

        /// <summary>
        /// 将现有 System 内容与新的表单 YAML 合并：若已包含标记块则替换该块，否则在末尾追加。
        /// </summary>
        public static string MergeFormsYamlIntoSystemContent(string currentSystemContent, string formsYaml)
        {
            var block = FormsYamlBlockStart + formsYaml + FormsYamlBlockEnd;
            if (string.IsNullOrEmpty(currentSystemContent))
                return block.TrimStart('\n');
            if (currentSystemContent.Contains(FormsYamlBlockStart))
            {
                int start = currentSystemContent.IndexOf(FormsYamlBlockStart, StringComparison.Ordinal);
                int end = currentSystemContent.IndexOf(FormsYamlBlockEnd, start, StringComparison.Ordinal);
                if (end >= 0)
                {
                    end += FormsYamlBlockEnd.Length;
                }
                else
                {
                    end = currentSystemContent.Length;
                }
                return currentSystemContent.Remove(start, end - start).Insert(start, block);
            }
            return currentSystemContent + block;
        }
        /// <summary>
        /// 将当前可用表单定义生成为 YAML 字符串。
        /// </summary>
        public static string ToYaml(IEnumerable<FormDefinition> forms)
        {
            var schema = new FormsSchemaYaml
            {
                Forms = BuildForms(forms)
            };

            var serializer = new SerializerBuilder()
                .WithNamingConvention(CamelCaseNamingConvention.Instance)
                .ConfigureDefaultValuesHandling(DefaultValuesHandling.OmitNull | DefaultValuesHandling.OmitDefaults)
                .Build();

            // 保留顶部说明注释（内容不参与结构序列化）。
            return "# 当前可用表单 Schema（供助手了解可展示的表单与字段）\n" + serializer.Serialize(schema);
        }

        private static List<FormYaml> BuildForms(IEnumerable<FormDefinition>? forms)
        {
            var list = new List<FormYaml>();
            foreach (var form in forms ?? [])
            {
                var formYaml = new FormYaml
                {
                    Id = form.Id,
                    Title = form.Title,
                    SubmitTarget = form.SubmitTarget,
                    SubmitLabel = form.SubmitLabel,
                    Fields = BuildFields(form.Fields)
                };
                list.Add(formYaml);
            }
            return list;
        }

        private static List<FieldYaml> BuildFields(IReadOnlyList<FormField>? fields)
        {
            var list = new List<FieldYaml>();
            foreach (var f in fields ?? [])
            {
                list.Add(new FieldYaml
                {
                    Id = f.Id,
                    Label = f.Label,
                    Description = string.IsNullOrEmpty(f.Description) ? null : f.Description,
                    Type = f.Type.ToString(),
                    Required = f.Required ? true : null,
                    Default = f.DefaultValue == null ? null : f.DefaultValue.ToString(),
                    Min = f.Min,
                    Max = f.Max,
                    Step = f.Step,
                    MaxLength = f.MaxLength,
                    Placeholder = string.IsNullOrEmpty(f.Placeholder) ? null : f.Placeholder,
                    Options = (f.Options != null && f.Options.Count > 0) ? new List<string>(f.Options) : null,
                    DefaultValues = (f.DefaultValues != null && f.DefaultValues.Count > 0) ? new List<string>(f.DefaultValues) : null
                });
            }
            return list;
        }

        private sealed class FormsSchemaYaml
        {
            public List<FormYaml> Forms { get; init; } = [];
        }

        private sealed class FormYaml
        {
            public string? Id { get; init; }
            public string? Title { get; init; }
            public string? SubmitTarget { get; init; }
            public string? SubmitLabel { get; init; }
            public List<FieldYaml> Fields { get; init; } = [];
        }

        private sealed class FieldYaml
        {
            public string? Id { get; init; }
            public string? Label { get; init; }
            public string? Description { get; init; }
            public string? Type { get; init; }

            // 仅在 true 时输出
            public bool? Required { get; init; }

            [YamlMember(Alias = "default")]
            public string? Default { get; init; }

            public double? Min { get; init; }
            public double? Max { get; init; }
            public double? Step { get; init; }
            public int? MaxLength { get; init; }
            public string? Placeholder { get; init; }
            public List<string>? Options { get; init; }
            public List<string>? DefaultValues { get; init; }
        }
    }
}