// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System;
using System.IO;
using System.Collections.Generic;
using System.Linq;
using System.Xml.Linq;

namespace Microsoft.DotNet.MacOsPkg.Core;

internal static class Package
{
    internal static void Unpack(string srcPath, string dstPath)
    {
        ExpandPackage(srcPath, dstPath);

        string? distribution = Utilities.FindInPath("Distribution", dstPath, isDirectory: false, searchOption: SearchOption.TopDirectoryOnly);
        if (!string.IsNullOrEmpty(distribution))
        {
            UnpackInstallerPackage(dstPath, distribution!);
            return;
        }

        string? packageInfo = Utilities.FindInPath("PackageInfo", dstPath, isDirectory: false, searchOption: SearchOption.TopDirectoryOnly);
        if (!string.IsNullOrEmpty(packageInfo))
        {
            UnpackComponentPackage(dstPath);
            return;
        }

        throw new Exception("Cannot unpack: no 'Distribution' or 'PackageInfo' file found in package");
    }

    internal static void Pack(string srcPath, string dstPath)
    {
        string? distribution = Utilities.FindInPath("Distribution", srcPath, isDirectory: false, searchOption: SearchOption.TopDirectoryOnly);
        if (!string.IsNullOrEmpty(distribution))
        {
            PackInstallerPackage(srcPath, dstPath, distribution!);
            return;
        }

        string? packageInfo = Utilities.FindInPath("PackageInfo", srcPath, isDirectory: false, searchOption: SearchOption.TopDirectoryOnly);
        if (!string.IsNullOrEmpty(packageInfo))
        {
            PackComponentPackage(srcPath, dstPath, packageInfo!);
            return;
        }

        throw new Exception("Cannot pack: no 'Distribution' or 'PackageInfo' file found in package");
    }

    private static void UnpackInstallerPackage(string dstPath, string distribution)
    {
        var xml = XElement.Load(distribution);
        List<XElement> componentPackages = xml.Elements("pkg-ref").Where(e => e.Value.Trim() != "").ToList();
        foreach (var package in componentPackages)
        {
            // Expanding the installer will unpack the nested component packages to a directory with a .pkg extension
            // so we repack the component packages to a temporary file and then rename the file with the .pkg extension.
            // Repacking is needed so that the signtool can properly identify and sign the nested component packages.
            string packageName = Path.Combine(dstPath, package.Value.Substring(1));
            string tempDest = Path.Combine(dstPath, Path.GetRandomFileName());
            FlattenComponentPackage(packageName, tempDest);

            Directory.Delete(packageName, true);
            File.Move(tempDest, packageName);
        }
    }

    /// <summary>
    /// Unpack the payload of the .pkg, and package up .app directories as .zips
    /// </summary>
    /// <param name="dstPath"></param>
    /// <remarks>
    /// In a pkg, the .app bundles are represented by directories with a standard file structure.
    /// The directory is typically marked with a .app extension, though apparently this is not required.
    /// The important part is that the .app bundle is viewed by the system as a single entity and is signed as such.
    /// This means that signtool needs to view the .app as a signable file and not as a directory. To achieve this,
    /// After unpacking the payload, we zip the .app directories so that signtool can properly track them, unpack them recursively again,
    /// and sign them.
    /// 
    /// There's one other important element to this. We need to recognize whether the .app directory is in fact
    /// a .app bundle and not, say "Microsoft.NetCore.App". To do this, we apply some heuristics.
    /// If:
    /// - Extension should be lower case ".app"
    /// - A directory named "Contents" under the .app directory.
    /// - An Info.plist in this "Contents" directory.
    /// 
    /// If these conditions are met, the file is re-zipped and treated like a bundle.
    /// 
    /// NOTE: I believe that there are very no circumstances where the first condition is met but the other two
    /// will NOT be met. For now, this method will throw an exception in this case so that further examination can be
    /// made.
    /// </remarks>
    private static void UnpackComponentPackage(string dstPath)
    {
        UnpackPayload(dstPath);

        // Zip the nested app bundles
        IEnumerable<string> nestedApps = Directory.GetDirectories(dstPath, "*.app", SearchOption.AllDirectories).Where(app => AppBundle.IsBundle(app));
        foreach (string app in nestedApps)
        {
            string tempDest = $"{app}.zip";
            AppBundle.Pack(app, tempDest);
            Directory.Delete(app, true);

            // Rename the zipped file to .app
            // This is needed so that the signtool
            // can properly identify and sign app bundles
            File.Move(tempDest, app);
        }
    }

    private static void PackInstallerPackage(string srcPath, string dstPath, string distribution)
    {
        string args = $"--distribution {distribution}";

        if (Directory.GetFiles(srcPath, "*.pkg", SearchOption.TopDirectoryOnly).Any())
        {
            args += $" --package-path {srcPath}";
        }

        string? resources = Utilities.FindInPath("Resources", srcPath, isDirectory: true, searchOption: SearchOption.TopDirectoryOnly);
        if (!string.IsNullOrEmpty(resources))
        {
            args += $" --resources {resources}";
        }

        string? scripts = Utilities.FindInPath("Scripts", srcPath, isDirectory: true, searchOption: SearchOption.TopDirectoryOnly);
        if (!string.IsNullOrEmpty(scripts))
        {
            args += $" --scripts {scripts}";
        }

        args += $" {dstPath}";

        ExecuteHelper.Run("productbuild", args);
    }

    private static void PackComponentPackage(string srcPath, string dstPath, string packageInfo)
    {
        // Unzip the nested app bundles
        IEnumerable<string> zippedNestedApps = Directory.GetFiles(srcPath, "*.app", SearchOption.AllDirectories).Where(app => AppBundle.IsBundle(app));
        foreach (string appZip in zippedNestedApps)
        {
            // Unzip the .app directory
            string tempDest = appZip + ".unzipped";
            AppBundle.Unpack(appZip, tempDest);
            File.Delete(appZip);

            // Rename the unzipped directory back to .app
            // so that it can be packed properly
            Directory.Move(tempDest, appZip);
        }

        XElement pkgInfo = XElement.Load(packageInfo);
        
        string payloadDirectoryPath = GetPayloadPath(srcPath, isDirectory: true);
        string identifier = GetPackageInfoAttribute(pkgInfo, "identifier");
        string version = GetPackageInfoAttribute(pkgInfo, "version");
        string installLocation = GetPackageInfoAttribute(pkgInfo, "install-location");

        string args = $"--root {payloadDirectoryPath} --identifier {identifier} --version {version} --install-location {installLocation}";
        string? script = Utilities.FindInPath("Scripts", srcPath, isDirectory: true, searchOption: SearchOption.TopDirectoryOnly);
        if (!string.IsNullOrEmpty(script))
        {
            args += $" --scripts {script}";
        }
        args += $" {dstPath}";

        ExecuteHelper.Run("pkgbuild", args);
    }

    private static void FlattenComponentPackage(string sourcePath, string destinationPath)
        => ExecuteHelper.Run("pkgutil", $"--flatten {sourcePath} {destinationPath}");

    private static void UnpackPayload(string dstPath)
    {
        string payloadFilePath = GetPayloadPath(dstPath, isDirectory: false);

        // Payloads can contain executable app bundles; keep extraction within the caller's workspace.
        string tempDir = Path.Combine(dstPath, Path.GetRandomFileName());
        Directory.CreateDirectory(tempDir);

        ExecuteHelper.Run("cat", $"{payloadFilePath} | gzip -d | cpio -id", tempDir);

        // Remove the payload file and replace it with
        // a directory of the same name containing the unpacked contents
        File.Delete(payloadFilePath);
        Directory.Move(tempDir, payloadFilePath);
    }

    private static string GetPayloadPath(string searchPath, bool isDirectory) =>
        Path.GetFullPath(Utilities.FindInPath("Payload", searchPath, isDirectory, searchOption: SearchOption.TopDirectoryOnly)
        ?? throw new Exception("Payload was not found"));

    private static void ExpandPackage(string srcPath, string dstPath) =>
        ExecuteHelper.Run("pkgutil", $"--expand {srcPath} {dstPath}");

    private static string GetPackageInfoAttribute(XElement pkgInfo, string elementName) =>
        pkgInfo.Attribute(elementName)?.Value ?? throw new Exception($"{elementName} is required in PackageInfo");

    internal static void VerifySignature(string inputPath)
    {
        Console.WriteLine($"Verifying signature of {inputPath}");
        string full_path = Path.GetFullPath(inputPath);
        string output = ExecuteHelper.Run("pkgutil", $"--check-signature {full_path}");
        Console.WriteLine(output);
        if (output.Contains("Status: no signature"))
        {
            throw new Exception("No signature found in package");
        }
    }
}