using System;
using System.Collections.Generic;
using System.IO;
using Newtonsoft.Json;
using XP.Common.Logging.Interfaces;
using XP.ReportEngine.Interfaces;
using XP.ReportEngine.Models;

namespace XP.ReportEngine.Services
{
    /// <summary>
    /// JSON 模板引擎实现 | JSON template engine implementation
    /// 负责加载、反序列化和验证 JSON 格式的报告模板
    /// Responsible for loading, deserializing and validating JSON report templates
    /// </summary>
    public class JsonTemplateEngine : ITemplateEngine
    {
        private readonly ILoggerService _logger;

        /// <summary>
        /// 默认样式定义（当模板引用未定义的样式名称时使用）
        /// Default style definition (used when template references undefined style name)
        /// </summary>
        public static readonly StyleDefinition DefaultStyle = new()
        {
            Font = null,
            Size = 12f,
            Bold = false,
            Italic = false,
            Color = "#000000",
            Align = "left",
            BackgroundColor = null
        };

        /// <summary>
        /// 构造函数 | Constructor
        /// </summary>
        /// <param name="logger">日志服务 | Logger service</param>
        public JsonTemplateEngine(ILoggerService logger)
        {
            _logger = logger?.ForModule<JsonTemplateEngine>() ?? throw new ArgumentNullException(nameof(logger));
        }

        /// <summary>
        /// 加载并反序列化 JSON 模板文件 | Load and deserialize JSON template file
        /// </summary>
        /// <param name="templatePath">模板文件路径 | Template file path</param>
        /// <returns>解析后的模板对象，文件不存在时返回 null | Parsed template object, null if file not found</returns>
        public ReportTemplate LoadTemplate(string templatePath)
        {
            if (string.IsNullOrWhiteSpace(templatePath))
            {
                _logger.Warn("模板文件路径为空 | Template file path is null or empty");
                return null;
            }

            if (!File.Exists(templatePath))
            {
                _logger.Warn("模板文件未找到: {Path} | Template file not found: {Path}", templatePath);
                return null;
            }

            _logger.Info("开始加载模板文件: {Path} | Loading template file: {Path}", templatePath);

            try
            {
                var json = File.ReadAllText(templatePath);
                var template = JsonConvert.DeserializeObject<ReportTemplate>(json);

                _logger.Info("模板文件加载成功 | Template file loaded successfully");
                return template;
            }
            catch (JsonReaderException ex)
            {
                // JSON 语法错误，包含错误位置信息 | JSON syntax error with position info
                var message = $"模板 JSON 语法错误，行 {ex.LineNumber}，位置 {ex.LinePosition}: {ex.Message} | " +
                              $"Template JSON syntax error at line {ex.LineNumber}, position {ex.LinePosition}: {ex.Message}";
                _logger.Error(ex, message);
                throw new InvalidOperationException(message, ex);
            }
            catch (JsonSerializationException ex)
            {
                // JSON 反序列化错误 | JSON deserialization error
                var message = $"模板 JSON 反序列化失败: {ex.Message} | Template JSON deserialization failed: {ex.Message}";
                _logger.Error(ex, message);
                throw new InvalidOperationException(message, ex);
            }
        }

        /// <summary>
        /// 验证模板结构完整性 | Validate template structure integrity
        /// 检查 document、pages、styles 必需字段是否存在
        /// Checks if required fields (document, pages, styles) are present
        /// </summary>
        /// <param name="template">待验证的模板 | Template to validate</param>
        /// <returns>验证结果 | Validation result</returns>
        public TemplateValidationResult Validate(ReportTemplate template)
        {
            if (template == null)
            {
                return TemplateValidationResult.Invalid("模板对象为 null | Template object is null");
            }

            var missingFields = new List<string>();

            if (template.Document == null)
            {
                missingFields.Add("document");
            }

            if (template.Pages == null || template.Pages.Count == 0)
            {
                missingFields.Add("pages");
            }

            if (template.Styles == null)
            {
                missingFields.Add("styles");
            }

            if (missingFields.Count > 0)
            {
                var fieldList = string.Join(", ", missingFields);
                var message = $"模板缺少必需字段: {fieldList} | Template missing required fields: {fieldList}";
                _logger.Warn(message);
                return TemplateValidationResult.Invalid(message);
            }

            _logger.Info("模板验证通过 | Template validation passed");
            return TemplateValidationResult.Valid();
        }

        /// <summary>
        /// 解析样式名称，未定义时回退为默认样式 | Resolve style name, fallback to default if undefined
        /// </summary>
        /// <param name="template">报告模板 | Report template</param>
        /// <param name="styleName">样式名称 | Style name</param>
        /// <returns>解析后的样式定义 | Resolved style definition</returns>
        public StyleDefinition ResolveStyle(ReportTemplate template, string styleName)
        {
            // 样式名称为空时直接返回默认样式 | Return default style if style name is empty
            if (string.IsNullOrWhiteSpace(styleName))
            {
                return DefaultStyle;
            }

            // 模板或样式字典为空时返回默认样式 | Return default style if template or styles dictionary is null
            if (template?.Styles == null)
            {
                _logger.Warn("模板样式字典为空，使用默认样式: {StyleName} | Template styles dictionary is null, using default style: {StyleName}", styleName);
                return DefaultStyle;
            }

            // 查找样式，找到则返回，否则回退为默认样式并记录警告
            // Look up style, return if found, otherwise fallback to default and log warning
            if (template.Styles.TryGetValue(styleName, out var style))
            {
                return style;
            }

            _logger.Warn("未定义的样式名称 '{StyleName}'，使用默认样式 | Undefined style name '{StyleName}', using default style", styleName);
            return DefaultStyle;
        }
    }
}