using System;
using System.Collections.Generic;
using System.IO;
using DCIT.Core.Models;

namespace DCIT.Core.Services
{
    public class RuntimeEnvironmentValidationService
    {
        private static readonly string[] WpsProgIds =
        {
            "KWPS.Application",
            "kwps.Application",
            "WPS.Application",
            "wps.Application",
        };

        private readonly string _startupDirectory;

        public RuntimeEnvironmentValidationService(string startupDirectory = null)
        {
            _startupDirectory = string.IsNullOrWhiteSpace(startupDirectory)
                ? AppContext.BaseDirectory
                : startupDirectory;
        }

        public RuntimeEnvironmentValidationResult Validate()
        {
            var result = new RuntimeEnvironmentValidationResult
            {
                StartupDirectory = _startupDirectory,
            };

            result.IsStartupDirectoryWritable = CanWriteToDirectory(_startupDirectory);
            if (!result.IsStartupDirectoryWritable)
            {
                result.BlockingIssues.Add("程序启动目录不可写。请将程序部署到当前用户具有写权限的目录后再启动。");
            }

            result.ResolvedAutomationProgId = ResolveAutomationProgId();
            if (string.IsNullOrWhiteSpace(result.ResolvedAutomationProgId))
            {
                result.BlockingIssues.Add("未检测到可自动化的 Microsoft Word 或 WPS 组件。当前环境无法满足目录/域刷新及 .doc 处理要求。");
            }

            result.ResolvedDocToPath = ResolveDocToPath();
            if (string.IsNullOrWhiteSpace(result.ResolvedDocToPath))
            {
                result.Warnings.Add("未检测到 docto.exe，.doc 兼容性将仅依赖 Word/WPS 自动化链路。");
            }

            return result;
        }

        protected virtual IEnumerable<string> GetOfficeAutomationProgIds()
        {
            yield return "Word.Application";
            foreach (var progId in WpsProgIds)
            {
                yield return progId;
            }
        }

        protected virtual bool IsProgIdRegistered(string progId)
        {
            return !string.IsNullOrWhiteSpace(progId)
                && Type.GetTypeFromProgID(progId, false) != null;
        }

        protected virtual string ResolveDocToPath()
        {
            var candidates = new List<string>();
            var envPath = Environment.GetEnvironmentVariable("DCIT_DOCTO_PATH");
            if (!string.IsNullOrWhiteSpace(envPath))
            {
                candidates.Add(envPath);
            }

            candidates.Add(Path.Combine(_startupDirectory, "docto.exe"));
            candidates.Add(Path.Combine(_startupDirectory, "tools", "DocTo", "docto.exe"));

            foreach (var candidate in candidates)
            {
                if (!string.IsNullOrWhiteSpace(candidate) && File.Exists(candidate))
                {
                    return candidate;
                }
            }

            var pathEnv = Environment.GetEnvironmentVariable("PATH") ?? string.Empty;
            foreach (var segment in pathEnv.Split(new[] { ';' }, StringSplitOptions.RemoveEmptyEntries))
            {
                try
                {
                    var candidate = Path.Combine(segment.Trim(), "docto.exe");
                    if (File.Exists(candidate))
                    {
                        return candidate;
                    }
                }
                catch
                {
                }
            }

            return null;
        }

        protected virtual bool CanWriteToDirectory(string directoryPath)
        {
            if (string.IsNullOrWhiteSpace(directoryPath))
            {
                return false;
            }

            try
            {
                Directory.CreateDirectory(directoryPath);
                var probePath = Path.Combine(directoryPath, ".dcit-writecheck-" + Guid.NewGuid().ToString("N") + ".tmp");
                File.WriteAllText(probePath, "probe");
                File.Delete(probePath);
                return true;
            }
            catch
            {
                return false;
            }
        }

        private string ResolveAutomationProgId()
        {
            foreach (var progId in GetOfficeAutomationProgIds())
            {
                if (IsProgIdRegistered(progId))
                {
                    return progId;
                }
            }

            return null;
        }
    }
}