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 AppliedExecutionEntry(
    string Alias,
    string Classification,
    string LogicalPath,
    string ResolvedPath,
    string Sha256,
    string? LogicalRuntimeRoot,
    string? ResolvedRuntimeRoot);

public sealed record AppliedNetworkEndpoint(string Host, IReadOnlyList<int> Ports);
public sealed record AppliedNetworkConfiguration(string Access, IReadOnlyList<AppliedNetworkEndpoint> Endpoints);
public sealed record AppliedResourceConfiguration(string Profile, int MemoryMb, int ProcessLimit, int ExecutionTimeoutSeconds);

public sealed record AppliedConfigurationPreview(
    string ConfigPath,
    string ConfigFingerprint,
    IReadOnlyList<ResolutionItem> Filesystem,
    IReadOnlyList<AppliedExecutionEntry> Execution,
    AppliedNetworkConfiguration Network,
    AppliedResourceConfiguration Resources);

public sealed record AppliedConfigurationDocument(
    int SchemaVersion,
    string ConfigPath,
    string ConfigFingerprint,
    IReadOnlyList<ResolutionItem> Filesystem,
    IReadOnlyList<AppliedExecutionEntry> Execution,
    AppliedNetworkConfiguration Network,
    AppliedResourceConfiguration Resources,
    DateTimeOffset AppliedAt);

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

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

    internal AppliedConfigurationStore(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(UserStoreRoot(), "applied-configurations"), name);
        _protectDirectory = protectDirectory;
    }

    public AppliedConfigurationDocument? Load()
    {
        if (!File.Exists(StorePath)) return null;
        AppliedConfigurationDocument? document = JsonSerializer.Deserialize<AppliedConfigurationDocument>(File.ReadAllText(StorePath), JsonOptions);
        if (document is null || document.SchemaVersion != 2 || !Path.IsPathFullyQualified(document.ConfigPath) ||
            !Regex.IsMatch(document.ConfigFingerprint, "^[A-Fa-f0-9]{64}$", RegexOptions.CultureInvariant) ||
            document.Filesystem.Any(static item => item.Kind is not ("workspace" or "mount") || !Path.IsPathFullyQualified(item.ResolvedPath)) ||
            document.Execution.GroupBy(static item => item.Alias, StringComparer.OrdinalIgnoreCase).Any(static group => group.Count() != 1) ||
            document.Execution.Any(static item => !Regex.IsMatch(item.Alias, "^[a-z0-9][a-z0-9._-]{0,63}$", RegexOptions.CultureInvariant) ||
                item.Classification is not ("executable" or "shell") || !Path.IsPathFullyQualified(item.ResolvedPath) ||
                !Regex.IsMatch(item.Sha256, "^[A-Fa-f0-9]{64}$", RegexOptions.CultureInvariant) ||
                (item.ResolvedRuntimeRoot is not null && !Path.IsPathFullyQualified(item.ResolvedRuntimeRoot))) ||
            document.Network is null || document.Resources is null ||
            document.Network.Access is not ("none" or "local" or "restricted") ||
            document.Network.Endpoints.Any(static item => string.IsNullOrWhiteSpace(item.Host) || item.Ports.Count == 0 || item.Ports.Any(static port => port is < 1 or > 65535)) ||
            document.Resources.MemoryMb <= 0 || document.Resources.ProcessLimit <= 0 || document.Resources.ExecutionTimeoutSeconds <= 0)
            throw new ConfigurationException($"Applied Configuration Store contains an invalid record: '{StorePath}'.");
        return document;
    }

    public void Save(AppliedConfigurationDocument document)
    {
        string directory = Path.GetDirectoryName(StorePath) ?? throw new ConfigurationException("Applied Configuration 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 class AppliedSandboxConfiguration
{
    private readonly string _configPath;
    private readonly string _baseDirectory;
    private readonly AgentConfiguration _configuration;
    private readonly AppliedConfigurationStore _store;

    public AppliedSandboxConfiguration(string configPath, AgentConfiguration configuration, AppliedConfigurationStore? store = null)
    {
        _configPath = Path.GetFullPath(configPath);
        _baseDirectory = Path.GetDirectoryName(_configPath)!;
        _configuration = configuration;
        _store = store ?? new AppliedConfigurationStore(_configPath);
    }

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

        var execution = new List<AppliedExecutionEntry>();
        foreach (ExecutionEntryOptions entry in _configuration.Sandbox.Execution.Entries)
        {
            string logicalPath = Absolute(entry.Path);
            string resolvedPath = ResolvedPath.Resolve(logicalPath);
            if (!File.Exists(resolvedPath)) throw Error("sandbox.resolved_executable_missing",
                $"Execution Entry '{entry.Alias}' does not resolve to an existing file: '{resolvedPath}'.", resolvedPath);
            string? logicalRuntime = entry.RuntimeRoot is null ? null : Absolute(entry.RuntimeRoot);
            string? resolvedRuntime = logicalRuntime is null ? null : ResolvedPath.Resolve(logicalRuntime);
            if (resolvedRuntime is not null && !Directory.Exists(resolvedRuntime)) throw Error("sandbox.resolved_runtime_missing",
                $"Execution Entry '{entry.Alias}' Runtime Root is not a directory: '{resolvedRuntime}'.", resolvedRuntime);
            string classification = ExecutableResolver.IsSupportedShell(resolvedPath) ? "shell" : "executable";
            execution.Add(new(entry.Alias, classification, entry.Path, resolvedPath,
                EntryExecutablePolicy.ComputeSha256(resolvedPath), entry.RuntimeRoot, resolvedRuntime));
        }
        (int memoryMb, int processes, int timeout) = ResourceLimits();
        var network = new AppliedNetworkConfiguration(_configuration.Sandbox.Network.Access,
            NetworkAllowances().Select(static item => new AppliedNetworkEndpoint(item.Host, item.Ports)).ToArray());
        return new(_configPath, Fingerprint(), filesystem, execution, network,
            new(_configuration.Sandbox.Resources.Profile, memoryMb, processes, timeout));
    }

    public AppliedConfigurationDocument Apply()
    {
        AppliedConfigurationPreview preview = Resolve();
        var document = new AppliedConfigurationDocument(2, preview.ConfigPath, preview.ConfigFingerprint,
            preview.Filesystem, preview.Execution, preview.Network, preview.Resources, DateTimeOffset.UtcNow);
        _store.Save(document);
        return document;
    }

    public AppliedConfigurationDocument? LoadApplied() => _store.Load();

    public bool IsApplied(AppliedConfigurationPreview current, AppliedConfigurationDocument? applied) =>
        applied is not null && applied.ConfigPath.Equals(current.ConfigPath, StringComparison.OrdinalIgnoreCase) &&
        applied.ConfigFingerprint.Equals(current.ConfigFingerprint, StringComparison.Ordinal) &&
        applied.Filesystem.SequenceEqual(current.Filesystem) && applied.Execution.SequenceEqual(current.Execution) &&
        NetworkEquivalent(applied.Network, current.Network) && applied.Resources == current.Resources;

    public EffectiveSandboxPolicy Compile(string journalDirectory, string backupDirectory)
    {
        AppliedConfigurationPreview current = Resolve();
        AppliedConfigurationDocument? applied = _store.Load();
        if (!IsApplied(current, applied))
            throw Error("sandbox.configuration_not_applied", "Configuration is not applied or has changed.", _configPath,
                "Review the consolidated permission matrix and run 'agent-mcp apply'.");

        var files = new List<FilePolicyEntry>();
        var artifactRoots = new List<string>();
        foreach (ResolutionItem item in current.Filesystem)
        {
            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 (AppliedExecutionEntry entry in current.Execution)
        {
            bool shell = entry.Classification == "shell";
            approvals.Add(new(entry.Alias, entry.ResolvedPath, entry.Sha256, shell, entry.ResolvedRuntimeRoot));
            files.Add(new(entry.ResolvedPath, FileCapability.Read | FileCapability.Execute,
                shell ? "approved_shell_executable" : "approved_entry_executable"));
            if (entry.ResolvedRuntimeRoot is not null)
            {
                runtimeRoots.Add(entry.ResolvedRuntimeRoot);
                files.Add(new(entry.ResolvedRuntimeRoot, 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();
        return new(normalizedFiles, approvals, runtimeRoots.Distinct(StringComparer.OrdinalIgnoreCase).ToArray(), artifactRoots,
            new((uint)processes, checked((ulong)memoryMb * 1024 * 1024)), _configuration.Sandbox.Network.Access,
            NetworkAllowances(), 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 resolved = ResolvedPath.Resolve(Absolute(logicalPath));
        if (!Directory.Exists(resolved)) throw Error("sandbox.resolved_directory_missing",
            $"{kind} Resolved Path is not a directory: '{resolved}'.", resolved);
        return new(kind, logicalPath, resolved, access);
    }

    private string Absolute(string path) => Path.IsPathFullyQualified(path) ? Path.GetFullPath(path) : Path.GetFullPath(path, _baseDirectory);
    private string Fingerprint() => Convert.ToHexString(SHA256.HashData(JsonSerializer.SerializeToUtf8Bytes(_configuration)));

    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(static item => new[] { ("127.0.0.1", (IReadOnlyList<int>)[item.Port]), ("::1", (IReadOnlyList<int>)[item.Port]) }).ToArray(),
            "restricted" => _configuration.Sandbox.Network.RestrictedEndpoints
                .Select(static 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(static item => ResolvedPath.Resolve(item.Path), StringComparer.OrdinalIgnoreCase)
            .Select(static group => new FilePolicyEntry(group.Key,
                group.Aggregate(FileCapability.None, static (value, item) => value | item.Capabilities),
                string.Join(',', group.Select(static 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) &&
                (parent.Capabilities & child.Capabilities) != parent.Capabilities && !IsDerivedExecutionRoot(child))
                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 IsDerivedExecutionRoot(FilePolicyEntry entry) => entry.Origin.Split(',').All(static origin =>
        origin is "approved_entry_executable" or "approved_shell_executable" or "runtime_root" or "os_runtime_root");

    private static bool IsBelow(string child, string parent) => child.StartsWith(
        parent.TrimEnd(Path.DirectorySeparatorChar) + Path.DirectorySeparatorChar, StringComparison.OrdinalIgnoreCase);

    internal static bool NetworkEquivalent(AppliedNetworkConfiguration left, AppliedNetworkConfiguration right) =>
        left.Access == right.Access && left.Endpoints.Count == right.Endpoints.Count &&
        left.Endpoints.Zip(right.Endpoints).All(static pair => pair.First.Host == pair.Second.Host && pair.First.Ports.SequenceEqual(pair.Second.Ports));

    private static ConfigurationException Error(string code, string message, string? target, string? resolution = null) =>
        new(message, code: code, category: "sandbox", target: target, resolution: resolution ?? "Correct the YAML and run 'agent-mcp apply'.");
}