using System.Security.Cryptography;
using System.Text;
using System.Text.Json;
using System.Text.RegularExpressions;
using Agent.App.Configuration;
using Agent.Windows.Security;
using Agent.Windows.Tools;

namespace Agent.App.Sandbox;

public sealed record ExecutableApprovalRecord(
    string Alias,
    string Classification,
    string LogicalPath,
    string ResolvedPath,
    string Sha256,
    string? RuntimeRoot,
    DateTimeOffset ApprovedAt);

public sealed record ExecutableApprovalDocument(int SchemaVersion, IReadOnlyList<ExecutableApprovalRecord> Approvals);

public sealed class ExecutableApprovalStore
{
    private static readonly JsonSerializerOptions JsonOptions = new(JsonSerializerDefaults.Web) { WriteIndented = true };
    public string StorePath { get; }
    private readonly bool _protectDirectory;

    public ExecutableApprovalStore(string? storePath = null) : this(storePath, protectDirectory: true) { }

    internal ExecutableApprovalStore(string? storePath, bool protectDirectory)
    {
        StorePath = storePath ?? Path.Combine(UserStoreRoot(), "executable-approvals.json");
        _protectDirectory = protectDirectory;
    }

    public IReadOnlyList<ExecutableApprovalRecord> List() => Load().Approvals;

    public ExecutableApprovalRecord? Find(string alias) =>
        Load().Approvals.SingleOrDefault(item => item.Alias.Equals(alias, StringComparison.OrdinalIgnoreCase));

    public void Approve(ExecutableApprovalRecord approval)
    {
        List<ExecutableApprovalRecord> records = Load().Approvals
            .Where(item => !item.Alias.Equals(approval.Alias, StringComparison.OrdinalIgnoreCase)).ToList();
        records.Add(approval);
        Save(new(1, records.OrderBy(item => item.Alias, StringComparer.OrdinalIgnoreCase).ToArray()));
    }

    public bool Revoke(string alias)
    {
        ExecutableApprovalDocument current = Load();
        ExecutableApprovalRecord[] remaining = current.Approvals
            .Where(item => !item.Alias.Equals(alias, StringComparison.OrdinalIgnoreCase)).ToArray();
        if (remaining.Length == current.Approvals.Count) return false;
        Save(new(1, remaining));
        return true;
    }

    private ExecutableApprovalDocument Load()
    {
        if (!File.Exists(StorePath)) return new(1, []);
        ExecutableApprovalDocument? document = JsonSerializer.Deserialize<ExecutableApprovalDocument>(File.ReadAllText(StorePath), JsonOptions);
        if (document is null || document.SchemaVersion != 1)
            throw new ConfigurationException($"Unsupported Executable Approval Store schema: '{StorePath}'.");
        if (document.Approvals.GroupBy(item => item.Alias, StringComparer.OrdinalIgnoreCase).Any(group => group.Count() != 1))
            throw new ConfigurationException($"Executable Approval Store contains duplicate Alias records: '{StorePath}'.");
        foreach (ExecutableApprovalRecord item in document.Approvals)
        {
            if (!Regex.IsMatch(item.Alias, "^[a-z0-9][a-z0-9._-]{0,63}$", RegexOptions.CultureInvariant) ||
                item.Classification is not ("executable" or "shell") || !Path.IsPathFullyQualified(item.ResolvedPath) ||
                !Regex.IsMatch(item.Sha256, "^[A-Fa-f0-9]{64}$", RegexOptions.CultureInvariant) ||
                (item.RuntimeRoot is not null && !Path.IsPathFullyQualified(item.RuntimeRoot)))
                throw new ConfigurationException($"Executable Approval Store contains an invalid record for Alias '{item.Alias}': '{StorePath}'.");
        }
        return document;
    }

    private void Save(ExecutableApprovalDocument document)
    {
        string directory = Path.GetDirectoryName(StorePath) ?? throw new ConfigurationException("Executable Approval Store path has no directory.");
        if (_protectDirectory) UserOnlyDirectory.Ensure(directory); else Directory.CreateDirectory(directory);
        AtomicJson.Write(StorePath, document, JsonOptions);
    }

    internal static string UserStoreRoot() => Path.Combine(
        Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), "AgentSandboxMcp");
}

public sealed record ResolutionItem(string Kind, string LogicalPath, string ResolvedPath, string Access);
public sealed record SandboxResolutionDocument(
    int SchemaVersion,
    string ConfigPath,
    string ConfigFingerprint,
    IReadOnlyList<ResolutionItem> Items,
    DateTimeOffset ConfirmedAt);

public sealed class SandboxResolutionStore
{
    private static readonly JsonSerializerOptions JsonOptions = new(JsonSerializerDefaults.Web) { WriteIndented = true };
    public string StorePath { get; }
    private readonly bool _protectDirectory;

    public SandboxResolutionStore(string configPath, string? storeRoot = null) : this(configPath, storeRoot, protectDirectory: true) { }

    internal SandboxResolutionStore(string configPath, string? storeRoot, bool protectDirectory)
    {
        string normalized = Path.GetFullPath(configPath).ToUpperInvariant();
        string name = Convert.ToHexString(SHA256.HashData(Encoding.UTF8.GetBytes(normalized))) + ".json";
        StorePath = Path.Combine(storeRoot ?? Path.Combine(ExecutableApprovalStore.UserStoreRoot(), "environment-resolutions"), name);
        _protectDirectory = protectDirectory;
    }

    public SandboxResolutionDocument? Load()
    {
        if (!File.Exists(StorePath)) return null;
        SandboxResolutionDocument? document = JsonSerializer.Deserialize<SandboxResolutionDocument>(File.ReadAllText(StorePath), JsonOptions);
        if (document is null || document.SchemaVersion != 1)
            throw new ConfigurationException($"Unsupported Sandbox Environment Resolution Store schema: '{StorePath}'.");
        if (!Path.IsPathFullyQualified(document.ConfigPath) ||
            !Regex.IsMatch(document.ConfigFingerprint, "^[A-Fa-f0-9]{64}$", RegexOptions.CultureInvariant) ||
            document.Items.Any(item => item.Kind is not ("workspace" or "mount") || !Path.IsPathFullyQualified(item.ResolvedPath)))
            throw new ConfigurationException($"Sandbox Environment Resolution Store contains an invalid record: '{StorePath}'.");
        return document;
    }

    public void Save(SandboxResolutionDocument document)
    {
        string directory = Path.GetDirectoryName(StorePath) ?? throw new ConfigurationException("Resolution Store path has no directory.");
        if (_protectDirectory) UserOnlyDirectory.Ensure(directory); else Directory.CreateDirectory(directory);
        AtomicJson.Write(StorePath, document, JsonOptions);
    }
}

public sealed record SandboxResolutionPreview(string ConfigPath, string Fingerprint, IReadOnlyList<ResolutionItem> Items);

public sealed class SandboxEnvironmentResolver
{
    private readonly string _configPath;
    private readonly string _baseDirectory;
    private readonly AgentConfiguration _configuration;
    private readonly SandboxResolutionStore _resolutionStore;
    private readonly ExecutableApprovalStore _approvalStore;

    public SandboxEnvironmentResolver(string configPath, AgentConfiguration configuration,
        SandboxResolutionStore? resolutionStore = null, ExecutableApprovalStore? approvalStore = null)
    {
        _configPath = Path.GetFullPath(configPath);
        _baseDirectory = Path.GetDirectoryName(_configPath)!;
        _configuration = configuration;
        _resolutionStore = resolutionStore ?? new SandboxResolutionStore(_configPath);
        _approvalStore = approvalStore ?? new ExecutableApprovalStore();
    }

    public SandboxResolutionPreview Resolve()
    {
        var items = new List<ResolutionItem>();
        foreach (string workspace in _configuration.Sandbox.Workspaces)
            items.Add(ResolveDirectory("workspace", workspace,
                _configuration.Sandbox.Profile == "development" ? "read_write_delete_execute" : "read_only"));
        foreach (MountOptions mount in _configuration.Sandbox.Mounts)
            items.Add(ResolveDirectory("mount", mount.Path, mount.Access));
        return new(_configPath, Fingerprint(), items);
    }

    public SandboxResolutionDocument Confirm()
    {
        SandboxResolutionPreview preview = Resolve();
        var document = new SandboxResolutionDocument(1, preview.ConfigPath, preview.Fingerprint, preview.Items, DateTimeOffset.UtcNow);
        _resolutionStore.Save(document);
        return document;
    }

    public EffectiveSandboxPolicy Compile(string journalDirectory, string backupDirectory)
    {
        SandboxResolutionPreview current = Resolve();
        SandboxResolutionDocument? confirmed = _resolutionStore.Load();
        if (confirmed is null)
            throw Error("sandbox.resolution_unconfirmed", "Sandbox Environment Resolution is not confirmed.", _configPath,
                "Run 'agent-mcp sandbox resolve --config <file>' and then 'agent-mcp sandbox confirm --config <file>'.");
        if (!confirmed.ConfigPath.Equals(current.ConfigPath, StringComparison.OrdinalIgnoreCase) ||
            !confirmed.ConfigFingerprint.Equals(current.Fingerprint, StringComparison.Ordinal) ||
            !Equivalent(confirmed.Items, current.Items))
            throw Error("sandbox.resolution_changed", "Sandbox Environment Resolution changed after confirmation.", _configPath,
                "Review 'sandbox resolve' and run 'sandbox confirm' again.");

        var files = new List<FilePolicyEntry>();
        var artifactRoots = new List<string>();
        foreach (ResolutionItem item in current.Items)
        {
            FileCapability capabilities = item.Kind == "workspace"
                ? (_configuration.Sandbox.Profile == "development"
                    ? FileCapability.Read | FileCapability.Write | FileCapability.Delete | FileCapability.Execute
                    : FileCapability.Read)
                : item.Access switch
                {
                    "read_only" => FileCapability.Read,
                    "read_write" => FileCapability.Read | FileCapability.Write,
                    "read_write_delete" => FileCapability.Read | FileCapability.Write | FileCapability.Delete,
                    _ => throw new ConfigurationException($"Unsupported Mount access '{item.Access}'.")
                };
            files.Add(new(item.ResolvedPath, capabilities, item.Kind));
            if (item.Kind == "workspace" && _configuration.Sandbox.Profile == "development") artifactRoots.Add(item.ResolvedPath);
        }

        var approvals = new List<ApprovedEntryExecutable>();
        var runtimeRoots = new List<string>();
        foreach ((string alias, bool shell) in RequestedAliases())
        {
            ExecutableApprovalRecord record = _approvalStore.Find(alias) ??
                throw Error("executable.approval_missing", $"Executable Alias '{alias}' has no approval.", alias,
                    $"Run 'agent-mcp executable resolve {alias} --config <file>' and 'executable approve'.");
            if (shell != record.Classification.Equals("shell", StringComparison.Ordinal))
                throw Error("executable.classification_changed", $"Executable Alias '{alias}' approval classification does not match sandbox.execution configuration.", alias,
                    "Revoke and re-approve the Executable Alias using its configured classification.");
            if (shell && !ExecutableResolver.IsSupportedShell(record.ResolvedPath))
                throw Error("executable.shell_unsupported", $"Executable Alias '{alias}' does not resolve to a supported Shell.", record.ResolvedPath,
                    "Select cmd.exe, powershell.exe, or pwsh.exe and explicitly approve it.");
            string logicalExecutable = Path.IsPathFullyQualified(record.LogicalPath)
                ? record.LogicalPath : Path.Combine(_baseDirectory, record.LogicalPath);
            string resolved = ResolvedPath.Resolve(logicalExecutable);
            if (!resolved.Equals(record.ResolvedPath, StringComparison.OrdinalIgnoreCase))
                throw Error("executable.resolution_changed", $"Executable Alias '{alias}' resolution changed from '{record.ResolvedPath}' to '{resolved}'.", resolved,
                    "Review the new Resolved Path and explicitly re-approve the Executable Alias.");
            string hash = EntryExecutablePolicy.ComputeSha256(resolved);
            if (!hash.Equals(record.Sha256, StringComparison.OrdinalIgnoreCase))
                throw Error("executable.hash_changed", $"Executable Alias '{alias}' SHA-256 changed.", resolved,
                    "Verify the Executable identity and explicitly re-approve it.");
            string? runtimeRoot = record.RuntimeRoot is null ? null : ResolvedPath.Resolve(record.RuntimeRoot);
            approvals.Add(new(alias, resolved, hash, shell, runtimeRoot));
            files.Add(new(resolved, FileCapability.Read | FileCapability.Execute, shell ? "approved_shell_executable" : "approved_entry_executable"));
            if (runtimeRoot is not null)
            {
                runtimeRoots.Add(runtimeRoot);
                files.Add(new(runtimeRoot, FileCapability.Read | FileCapability.Execute, "runtime_root"));
            }
        }

        string system32 = ResolvedPath.Resolve(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Windows), "System32"));
        files.Add(new(system32, FileCapability.Read | FileCapability.Execute, "os_runtime_root"));
        IReadOnlyList<FilePolicyEntry> normalizedFiles = NormalizeRoots(files);
        (int memoryMb, int processes, int timeout) = ResourceLimits();
        IReadOnlyList<(string Host, IReadOnlyList<int> Ports)> network = NetworkAllowances();
        return new(normalizedFiles, approvals, runtimeRoots.Distinct(StringComparer.OrdinalIgnoreCase).ToArray(),
            artifactRoots, new((uint)processes, checked((ulong)memoryMb * 1024 * 1024)),
            _configuration.Sandbox.Network.Access, network, journalDirectory, backupDirectory,
            checked((long)_configuration.FileEdit.MemoryBackupLimitMb * 1024 * 1024),
            _configuration.Limits.WholeReadBytes, _configuration.Limits.SearchMaxResults,
            _configuration.Limits.TailMaxLines, timeout, _configuration.Sandbox.Resources.Profile,
            ["registryRead", "lpacInstrumentation"]);
    }

    private ResolutionItem ResolveDirectory(string kind, string logicalPath, string access)
    {
        string absolute = Path.IsPathFullyQualified(logicalPath) ? logicalPath : Path.Combine(_baseDirectory, logicalPath);
        string resolved = ResolvedPath.Resolve(absolute);
        if (!Directory.Exists(resolved)) throw Error("sandbox.resolved_directory_missing", $"{kind} Resolved Path is not a directory: '{resolved}'.", resolved,
            "Correct the Logical Path or restore the directory, then confirm the Sandbox Environment Resolution again.");
        return new(kind, logicalPath, resolved, access);
    }

    private string Fingerprint()
    {
        string json = JsonSerializer.Serialize(_configuration.Sandbox, new JsonSerializerOptions(JsonSerializerDefaults.Web));
        return Convert.ToHexString(SHA256.HashData(Encoding.UTF8.GetBytes(json)));
    }

    private IEnumerable<(string Alias, bool Shell)> RequestedAliases() =>
        _configuration.Sandbox.Execution.Executables.Select(alias => (alias, false))
            .Concat(_configuration.Sandbox.Execution.Shells.Select(alias => (alias, true)));

    private (int MemoryMb, int Processes, int Timeout) ResourceLimits()
    {
        (int memory, int processes, int timeout) = _configuration.Sandbox.Resources.Profile switch
        {
            "constrained" => (1024, 4, 300),
            "normal" => (4096, 16, 1800),
            "extended" => (8192, 32, 3600),
            _ => throw new ConfigurationException($"Unsupported Resource Profile '{_configuration.Sandbox.Resources.Profile}'.")
        };
        return (_configuration.Sandbox.Resources.MemoryMb ?? memory,
            _configuration.Sandbox.Resources.ProcessLimit ?? processes,
            _configuration.Sandbox.Resources.ExecutionTimeoutSeconds ?? timeout);
    }

    private IReadOnlyList<(string Host, IReadOnlyList<int> Ports)> NetworkAllowances() =>
        _configuration.Sandbox.Network.Access switch
        {
            "none" => [],
            "local" => _configuration.Sandbox.Network.LocalEndpoints
                .SelectMany(item => new[] { ("127.0.0.1", (IReadOnlyList<int>)[item.Port]), ("::1", (IReadOnlyList<int>)[item.Port]) }).ToArray(),
            "restricted" => _configuration.Sandbox.Network.RestrictedEndpoints
                .Select(item => (item.Host, (IReadOnlyList<int>)item.Ports)).ToArray(),
            _ => throw new ConfigurationException($"Unsupported Network access '{_configuration.Sandbox.Network.Access}'.")
        };

    private static IReadOnlyList<FilePolicyEntry> NormalizeRoots(IEnumerable<FilePolicyEntry> input)
    {
        FilePolicyEntry[] roots = input.GroupBy(item => ResolvedPath.Resolve(item.Path), StringComparer.OrdinalIgnoreCase)
            .Select(group => new FilePolicyEntry(group.Key,
                group.Aggregate(FileCapability.None, (value, item) => value | item.Capabilities),
                string.Join(',', group.Select(item => item.Origin).Distinct(StringComparer.Ordinal).Order(StringComparer.Ordinal)))).ToArray();
        foreach (FilePolicyEntry parent in roots)
        foreach (FilePolicyEntry child in roots)
        {
            if (ReferenceEquals(parent, child) || !IsBelow(child.Path, parent.Path)) continue;
            if ((parent.Capabilities & child.Capabilities) != parent.Capabilities)
                throw new ConfigurationException($"Nested Filesystem Root '{child.Path}' is narrower than inherited capabilities from '{parent.Path}' and cannot be enforced without widening it.");
        }
        return roots;
    }

    private static bool Equivalent(IReadOnlyList<ResolutionItem> left, IReadOnlyList<ResolutionItem> right) =>
        left.OrderBy(Key, StringComparer.OrdinalIgnoreCase).SequenceEqual(right.OrderBy(Key, StringComparer.OrdinalIgnoreCase));
    private static string Key(ResolutionItem item) => $"{item.Kind}|{item.LogicalPath}|{item.ResolvedPath}|{item.Access}";
    private static bool IsBelow(string child, string parent) => child.StartsWith(parent.TrimEnd(Path.DirectorySeparatorChar) + Path.DirectorySeparatorChar, StringComparison.OrdinalIgnoreCase);
    private static ConfigurationException Error(string code, string message, string? target, string resolution) =>
        new(message, code: code, category: "sandbox", target: target, resolution: resolution);
}

public static class ExecutableResolver
{
    public static bool IsSupportedShell(string path) => Path.GetFileName(path).ToLowerInvariant() is "cmd.exe" or "powershell.exe" or "pwsh.exe";

    public static IReadOnlyList<string> ResolveCandidates(string alias, string? explicitPath)
    {
        if (!string.IsNullOrWhiteSpace(explicitPath))
        {
            string resolved = ResolvedPath.Resolve(explicitPath);
            if (!File.Exists(resolved)) throw new ConfigurationException($"Executable Resolved Path is not a file: '{resolved}'.");
            return [resolved];
        }
        string fileName = Path.HasExtension(alias) ? alias : alias + ".exe";
        string[] candidates = (Environment.GetEnvironmentVariable("PATH") ?? string.Empty)
            .Split(Path.PathSeparator, StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries)
            .Select(directory => Path.Combine(directory, fileName)).Where(File.Exists)
            .Select(path => ResolvedPath.Resolve(path)).Distinct(StringComparer.OrdinalIgnoreCase).ToArray();
        if (candidates.Length == 0) throw new ConfigurationException($"No PATH candidate was found for Executable Alias '{alias}'. Use --path <path>.");
        return candidates;
    }
}

internal static class AtomicJson
{
    public static void Write<T>(string path, T value, JsonSerializerOptions options)
    {
        string temporary = path + "." + Guid.NewGuid().ToString("N") + ".tmp";
        try
        {
            using (var stream = new FileStream(temporary, FileMode.CreateNew, FileAccess.Write, FileShare.None, 4096, FileOptions.WriteThrough))
            {
                JsonSerializer.Serialize(stream, value, options);
                stream.Flush(flushToDisk: true);
            }
            File.Move(temporary, path, overwrite: true);
        }
        finally
        {
            if (File.Exists(temporary)) File.Delete(temporary);
        }
    }
}