using System.Security.AccessControl;
using System.Security.Principal;
using Agent.Windows.Recovery;

namespace Agent.Windows.Security;

public sealed record AclSnapshot(string Path, byte[] SecurityDescriptor, Guid? JournalEntryId = null);

public sealed class TaskAclManager(SecurityIdentifier appContainerSid, ISecurityAuditSink audit, TaskResourceJournal? journal = null)
{
    public AclSnapshot Grant(Guid taskId, string path, FileCapability capabilities)
    {
        string canonical = CanonicalPath.Resolve(path);
        FileSystemSecurity security = ReadSecurity(canonical);
        byte[] original = security.GetSecurityDescriptorBinaryForm();
        Guid? journalEntry = journal?.Prepare("acl", canonical, new Dictionary<string, string>
        {
            ["security_descriptor"] = Convert.ToBase64String(original)
        });
        FileSystemRights rights = ToRights(capabilities);
        if (rights == 0) throw new ArgumentOutOfRangeException(nameof(capabilities));
        bool directory = Directory.Exists(canonical);
        var rule = new FileSystemAccessRule(appContainerSid, rights,
            directory ? InheritanceFlags.ContainerInherit | InheritanceFlags.ObjectInherit : InheritanceFlags.None,
            PropagationFlags.None, AccessControlType.Allow);
        security.AddAccessRule(rule);
        WriteSecurity(canonical, security);
        if (journalEntry is not null) journal!.MarkApplied(journalEntry.Value);
        audit.Write(new(DateTimeOffset.UtcNow, taskId, "acl.apply", "applied", new Dictionary<string, string> { ["path"] = canonical, ["sid"] = appContainerSid.Value, ["rights"] = rights.ToString() }));
        return new(canonical, original, journalEntry);
    }

    public void Restore(Guid taskId, AclSnapshot snapshot)
    {
        FileSystemSecurity security = Directory.Exists(snapshot.Path) ? new DirectorySecurity() : new FileSecurity();
        security.SetSecurityDescriptorBinaryForm(snapshot.SecurityDescriptor, AccessControlSections.Access);
        WriteSecurity(snapshot.Path, security);
        if (snapshot.JournalEntryId is not null) journal!.MarkCleaned(snapshot.JournalEntryId.Value);
        audit.Write(new(DateTimeOffset.UtcNow, taskId, "acl.restore", "restored", new Dictionary<string, string> { ["path"] = snapshot.Path }));
    }

    public void NormalizeNewEntry(Guid taskId, string path)
    {
        string canonical = CanonicalPath.Resolve(path);
        FileSystemSecurity security = ReadSecurity(canonical);
        security.SetAccessRuleProtection(isProtected: true, preserveInheritance: false);
        foreach (FileSystemAccessRule rule in security.GetAccessRules(includeExplicit: true, includeInherited: false, typeof(SecurityIdentifier))
            .OfType<FileSystemAccessRule>()
            .Where(rule => rule.IdentityReference == appContainerSid)
            .ToArray())
            security.RemoveAccessRuleSpecific(rule);
        security.SetAccessRuleProtection(isProtected: false, preserveInheritance: false);
        WriteSecurity(canonical, security);
        audit.Write(new(DateTimeOffset.UtcNow, taskId, "acl.normalize", "normalized", new Dictionary<string, string> { ["path"] = canonical }));
    }

    private static FileSystemSecurity ReadSecurity(string path) => Directory.Exists(path)
        ? FileSystemAclExtensions.GetAccessControl(new DirectoryInfo(path), AccessControlSections.Access)
        : FileSystemAclExtensions.GetAccessControl(new FileInfo(path), AccessControlSections.Access);

    private static void WriteSecurity(string path, FileSystemSecurity security)
    {
        if (security is DirectorySecurity directorySecurity) FileSystemAclExtensions.SetAccessControl(new DirectoryInfo(path), directorySecurity);
        else FileSystemAclExtensions.SetAccessControl(new FileInfo(path), (FileSecurity)security);
    }

    private static FileSystemRights ToRights(FileCapability capabilities)
    {
        FileSystemRights rights = 0;
        if ((capabilities & FileCapability.Read) != 0) rights |= FileSystemRights.ReadAndExecute | FileSystemRights.ListDirectory;
        if ((capabilities & FileCapability.Write) != 0) rights |= FileSystemRights.Write;
        if ((capabilities & FileCapability.Execute) != 0) rights |= FileSystemRights.ReadAndExecute;
        if ((capabilities & FileCapability.Delete) != 0) rights |= FileSystemRights.Delete | FileSystemRights.DeleteSubdirectoriesAndFiles;
        return rights;
    }
}