using System.Diagnostics;

namespace Rmsys.Infrastructure;

/// <summary>
/// Word/OFD → PDF 转换（数据包内 PAD 只能显示 PDF，不能显示 docx）。
///
/// 依赖外部转换器：服务器上装 LibreOffice（soffice）即可；可用环境变量
/// RMSYS_SOFFICE 指定 soffice 可执行文件全路径。
/// 转换结果按「材料Id_版本号」缓存在 App_Data/_pdfcache，同一份材料只转一次。
/// </summary>
public static class PdfConverter
{
    private static readonly object _lock = new();
    private static bool _checked;
    private static string? _soffice;

    /// <summary>转换器是否可用（不可用时不阻断出包，只是包里没有 PDF 正文）</summary>
    public static bool Available
    {
        get { EnsureProbe(); return _soffice != null; }
    }

    public static string? ExePath { get { EnsureProbe(); return _soffice; } }

    private static void EnsureProbe()
    {
        if (_checked) return;
        lock (_lock)
        {
            if (_checked) return;
            _checked = true;

            var custom = Environment.GetEnvironmentVariable("RMSYS_SOFFICE");
            if (!string.IsNullOrWhiteSpace(custom) && File.Exists(custom)) { _soffice = custom; return; }

            var candidates = new[]
            {
                "soffice", "soffice.exe", "soffice.com",
                @"C:\Program Files\LibreOffice\program\soffice.exe",
                @"C:\Program Files (x86)\LibreOffice\program\soffice.exe",
                "/usr/bin/soffice", "/usr/lib/libreoffice/program/soffice"
            };
            foreach (var c in candidates)
            {
                try
                {
                    if (c.Contains('/') || c.Contains('\\'))
                    {
                        if (File.Exists(c)) { _soffice = c; return; }
                    }
                    else
                    {
                        var psi = new ProcessStartInfo(c) { Arguments = "--version", RedirectStandardOutput = true, RedirectStandardError = true, UseShellExecute = false, CreateNoWindow = true };
                        using var p = Process.Start(psi);
                        if (p != null && p.WaitForExit(8000) && p.ExitCode == 0) { _soffice = c; return; }
                        try { p?.Kill(true); } catch { }
                    }
                }
                catch { /* 试下一个 */ }
            }
        }
    }

    /// <summary>
    /// 把源文件转成 PDF，返回 PDF 全路径；转不了返回 null。
    /// PDF 直接返回源文件；docx/doc 走 LibreOffice；其余类型（.lrmx/.ofd 等）返回 null。
    /// </summary>
    public static string? ToPdf(string srcFull, string cacheDir, string cacheKey)
    {
        try
        {
            if (!File.Exists(srcFull)) return null;
            var ext = Path.GetExtension(srcFull).ToLowerInvariant();

            // 已经是 PDF：直接用源文件
            if (ext == ".pdf") return srcFull;

            // 只对 Word 家族做转换
            if (ext != ".docx" && ext != ".doc") return null;

            if (!Available || ExePath == null) return null;

            Directory.CreateDirectory(cacheDir);
            var cache = Path.Combine(cacheDir, cacheKey + ".pdf");
            if (File.Exists(cache) && File.GetLastWriteTimeUtc(cache) >= File.GetLastWriteTimeUtc(srcFull))
                return cache;

            var outDir = Path.Combine(Path.GetTempPath(), "rmsyspdf_" + Guid.NewGuid().ToString("N"));
            Directory.CreateDirectory(outDir);
            var profile = Path.Combine(Path.GetTempPath(), "rmsyslo_" + Guid.NewGuid().ToString("N"));

            try
            {
                // 每次用独立 UserInstallation，避免并发调用时 LibreOffice 单实例锁冲突
                var args = $"--headless --norestore --nolockcheck --nodefault --nofirststartwizard " +
                           $"-env:UserInstallation=file:///{profile.Replace('\\', '/')} " +
                           $"--convert-to pdf:writer_pdf_Export --outdir \"{outDir}\" \"{srcFull}\"";

                var psi = new ProcessStartInfo(ExePath!)
                {
                    Arguments = args,
                    RedirectStandardOutput = true,
                    RedirectStandardError = true,
                    UseShellExecute = false,
                    CreateNoWindow = true
                };
                using var proc = Process.Start(psi);
                if (proc == null) return null;
                if (!proc.WaitForExit(180_000))
                {
                    try { proc.Kill(true); } catch { }
                    return null;
                }

                var produced = Directory.GetFiles(outDir, "*.pdf").FirstOrDefault();
                if (produced == null || new FileInfo(produced).Length < 1024) return null;

                File.Copy(produced, cache, overwrite: true);
                return cache;
            }
            finally
            {
                try { if (Directory.Exists(outDir)) Directory.Delete(outDir, true); } catch { }
                try { if (Directory.Exists(profile)) Directory.Delete(profile, true); } catch { }
            }
        }
        catch
        {
            return null;   // 转换失败不阻断出包
        }
    }
}