using System.Text.Json;
using System.Text.Json.Nodes;
using ClawdDotNet.Core.Engine;
using ClawdDotNet.Core.Sandbox;

namespace ClawdDotNet.Core.Runtimes;

/// <summary>
/// #712: Claude Code as a runtime — <c>claude -p</c> in the sandbox.
///
/// <para><b>Allow lists, never the bypass.</b> Claude Code gets <c>--allowedTools</c> and
/// <c>--max-turns</c>; <c>--dangerously-skip-permissions</c> is never passed. In print mode
/// there is no one to ask, so what is not allowed is denied.</para>
///
/// <para><b>Only our configuration counts.</b> The work copy may carry a
/// <c>.claude/settings.json</c> or an <c>.mcp.json</c> — written by whoever wrote the
/// workspace. <c>--setting-sources user</c> reads only the settings this class writes into
/// the runtime's home before each run; <c>--strict-mcp-config</c> only the one MCP server,
/// ours. Hooks are off, and what a run left in the home that would instruct the next one
/// (agents, commands, skills, a CLAUDE.md) is removed before it starts.</para>
///
/// <para><b>Nothing secret on the command line.</b> The key goes through the launcher's
/// file; the prompt through stdin; the briefing through a file.</para>
/// </summary>
public sealed class ClaudeCodeRuntime(Func<ClaudeCodeSettings> settings) : IForeignRuntime
{
    public string Kind => RuntimeKinds.ClaudeCode;

    /// <summary>Reading and editing the work copy, and our MCP server. No shell, no web.</summary>
    public static readonly IReadOnlyList<string> DefaultAllowedTools = ["Read", "Edit", "Write", "Glob", "Grep", "mcp__clawd"];

    /// <summary>Denied even when listed — the web goes through our tools (#193), not around them.</summary>
    public static readonly IReadOnlyList<string> AlwaysDenied = ["WebFetch", "WebSearch"];

    /// <summary>The hosts Claude Code needs: the API. Updates and telemetry are switched off.</summary>
    public static readonly IReadOnlyList<string> Egress = ["api.anthropic.com"];

    private static readonly string[] Candidates =
    [
        "~/.local/bin/claude", "~/.claude/local/claude", "/usr/local/bin/claude", "/usr/bin/claude"
    ];

    /// <summary>The program, as configured or where an installer puts it; links resolved.</summary>
    public static string? Locate(ClaudeCodeSettings settings)
    {
        var home = Environment.GetFolderPath(Environment.SpecialFolder.UserProfile);
        var candidates = string.IsNullOrWhiteSpace(settings.Executable) ? Candidates : [settings.Executable];
        foreach (var candidate in candidates)
        {
            var path = candidate.StartsWith("~/", StringComparison.Ordinal) ? Path.Combine(home, candidate[2..]) : candidate;
            if (!File.Exists(path))
                continue;
            var target = new FileInfo(path).ResolveLinkTarget(returnFinalTarget: true);
            return target?.FullName ?? Path.GetFullPath(path);
        }
        return null;
    }

    public SandboxRequest Prepare(ForeignRunContext context)
    {
        var config = settings();
        var executable = Locate(config)
            ?? throw new ForeignRunException("Claude Code is not installed here — set 'claudeCode.executable' in the instance configuration.");
        var secret = config.OnSubscription ? config.OAuthToken : config.ApiKey;
        if (string.IsNullOrWhiteSpace(secret))
            throw new ForeignRunException(config.OnSubscription
                ? "No subscription token for Claude Code — run 'claude setup-token' and enter it in the instance settings."
                : "No API key for Claude Code in the instance settings.");

        var runtime = context.Agent.Runtime;
        var allowed = (runtime.AllowedTools.Count > 0 ? runtime.AllowedTools : DefaultAllowedTools)
            .Where(t => !AlwaysDenied.Contains(t, StringComparer.OrdinalIgnoreCase))
            .Where(t => context.HasMcp || !t.StartsWith("mcp__", StringComparison.Ordinal))
            .ToList();

        PrepareHome(context.HomeDirectory, allowed);
        File.WriteAllText(Path.Combine(context.PrivateDirectory, ForeignRunContext.BriefingFileName), Briefing(context));
        File.WriteAllText(Path.Combine(context.PrivateDirectory, "mcp.json"), McpConfig(context));

        var arguments = new List<string>
        {
            "-p",
            "--output-format", "stream-json",
            "--verbose",
            "--max-turns", Math.Clamp(runtime.MaxTurns, 1, 500).ToString(System.Globalization.CultureInfo.InvariantCulture),
            "--setting-sources", "user",
            "--strict-mcp-config",
            "--mcp-config", ForeignRunContext.Private + "/mcp.json",
            "--append-system-prompt-file", ForeignRunContext.Private + "/" + ForeignRunContext.BriefingFileName,
            "--allowedTools", string.Join(",", allowed),
            "--disallowedTools", string.Join(",", AlwaysDenied)
        };
        if (ModelName(context.Agent.Model) is { } model)
            arguments.AddRange(["--model", model]);

        var environment = new Dictionary<string, string>(context.McpEnvironment(), StringComparer.Ordinal)
        {
            ["DISABLE_AUTOUPDATER"] = "1",
            ["DISABLE_TELEMETRY"] = "1",
            ["DISABLE_ERROR_REPORTING"] = "1",
            ["CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC"] = "1"
        };

        var readOnly = new List<string>(config.ReadOnlyPaths.Concat(context.HelperPaths()));
        var directory = Path.GetDirectoryName(executable)!;
        if (!directory.StartsWith("/usr/", StringComparison.Ordinal))
            readOnly.Add(directory);

        return new SandboxRequest
        {
            Executable = executable,
            Arguments = arguments,
            WorkspacePath = context.WorkCopy,
            ProtectedPaths = [],
            ReadOnlyPaths = readOnly,
            Mounts = context.Mounts(),
            Environment = environment,
            SecretEnvironment = new Dictionary<string, string>
            {
                [config.OnSubscription ? "CLAUDE_CODE_OAUTH_TOKEN" : "ANTHROPIC_API_KEY"] = secret.Trim()
            },
            Egress = [.. Egress, .. runtime.Egress],
            StandardInput = context.Message,
            Limits = ForeignRunner.Limits(runtime)
        };
    }

    /// <summary>
    /// The home as this run finds it: our settings, and nothing a previous run left to
    /// instruct this one. Login state and history stay.
    /// </summary>
    internal static void PrepareHome(string home, IReadOnlyList<string> allowed)
    {
        // A previous run could have made .claude a link to anywhere on the host — writing
        // through it would put our file there. Links go; only a real folder is used.
        var claude = Path.Combine(home, ".claude");
        if (new DirectoryInfo(claude).LinkTarget is not null || File.Exists(claude))
            DeleteEntry(claude);
        Directory.CreateDirectory(claude);
        foreach (var name in new[] { "agents", "commands", "skills", "hooks", "output-styles", "plugins" })
        {
            var path = Path.Combine(claude, name);
            if (Directory.Exists(path) || File.Exists(path))
                DeleteEntry(path);
        }
        foreach (var name in new[] { "CLAUDE.md", "settings.local.json" })
        {
            var path = Path.Combine(claude, name);
            if (File.Exists(path) || Directory.Exists(path))
                DeleteEntry(path);
        }

        var settings = new JsonObject
        {
            ["permissions"] = new JsonObject
            {
                ["allow"] = new JsonArray(allowed.Select(a => (JsonNode)a).ToArray()),
                ["deny"] = new JsonArray(AlwaysDenied.Select(a => (JsonNode)a).ToArray())
            },
            ["disableAllHooks"] = true
        };
        var file = Path.Combine(claude, "settings.json");
        if (File.Exists(file) || new FileInfo(file).LinkTarget is not null)
            DeleteEntry(file);
        File.WriteAllText(file, settings.ToJsonString(new JsonSerializerOptions { WriteIndented = true }));
    }

    /// <summary>Removes a file, a folder or a link — never what a link points to.</summary>
    private static void DeleteEntry(string path)
    {
        var info = new FileInfo(path);
        if (info.LinkTarget is not null || !Directory.Exists(path))
            info.Delete();
        else
            Directory.Delete(path, recursive: true);
    }

    private static string Briefing(ForeignRunContext context)
        => context.Briefing + "\n\n## How this run works\n\n"
           + "You work in /work, a copy of your workspace. Nothing you change there is used directly: "
           + "the changed files become a proposal that is reviewed before anything is applied.\n"
           + (context.HasMcp
               ? "The taskboard, your colleagues and your other tools are reachable only through the MCP server 'clawd'.\n"
               : "")
           + "End with a short summary of what you did and what is left.";

    private static string McpConfig(ForeignRunContext context)
    {
        var servers = new JsonObject();
        if (context.HasMcp)
        {
            var env = new JsonObject
            {
                [Mcp.McpStdioBridge.TokenFileVariable] = ForeignRunContext.Private + "/" + ForeignRunContext.TokenFileName
            };
            // An MCP server does not inherit the runtime's environment, only a few variables.
            foreach (var (key, value) in context.Helper!.Environment)
                env[key] = value;
            servers["clawd"] = new JsonObject
            {
                ["type"] = "stdio",
                ["command"] = context.Helper.Executable,
                ["args"] = new JsonArray("--mcp-bridge", Mcp.McpStdioBridge.SocketArgument, ForeignRunContext.McpSocketInSandbox),
                ["env"] = env
            };
        }
        return new JsonObject { ["mcpServers"] = servers }.ToJsonString();
    }

    /// <summary><c>anthropic/claude-sonnet-5</c> (OpenRouter's name) → <c>claude-sonnet-5</c>; empty stays the runtime's default.</summary>
    public static string? ModelName(string? model)
    {
        if (string.IsNullOrWhiteSpace(model))
            return null;
        var slash = model.IndexOf('/');
        if (slash >= 0 && !model.StartsWith("anthropic/", StringComparison.OrdinalIgnoreCase))
            return null;
        return slash >= 0 ? model[(slash + 1)..] : model;
    }

    public ForeignRunOutcome Interpret(SandboxResult result, ForeignRunContext context, Action<string> note)
    {
        var onSubscription = settings().OnSubscription;
        JsonObject? final = null;
        string? model = null;
        var turns = 0;

        foreach (var line in result.StandardOutput.Split('\n'))
        {
            if (!line.StartsWith('{'))
                continue;
            JsonObject? message;
            try
            {
                message = JsonNode.Parse(line) as JsonObject;
            }
            catch (JsonException)
            {
                continue;
            }
            switch (Text(message?["type"]))
            {
                case "system" when Text(message!["subtype"]) == "init":
                    model = Text(message["model"]);
                    break;
                case "assistant":
                    turns++;
                    foreach (var part in message!["message"]?["content"] as JsonArray ?? [])
                    {
                        if (Text(part?["type"]) == "tool_use")
                            note($"Tool: {Text(part!["name"])}");
                        else if (Text(part?["type"]) == "text" && Text(part!["text"]) is { Length: > 0 } text)
                            note(text.Length > 500 ? text[..500] + " …" : text);
                    }
                    break;
                case "result":
                    final = message;
                    break;
            }
        }

        if (final is null)
        {
            var reason = result.TimedOut ? "timed out"
                : result.OutputTruncated ? "produced more output than allowed"
                : $"ended with exit code {result.ExitCode} and no result";
            return new ForeignRunOutcome
            {
                Status = result.TimedOut ? AgentRunStatus.Cancelled : AgentRunStatus.Failed,
                Text = $"[Claude Code {reason}]" + Tail(result.StandardError),
                Turns = turns,
                Model = model,
                OnSubscription = onSubscription
            };
        }

        var usage = final["usage"] as JsonObject;
        var input = Number(usage?["input_tokens"]);
        var cacheWrite = Number(usage?["cache_creation_input_tokens"]);
        var cacheRead = Number(usage?["cache_read_input_tokens"]);
        var subtype = Text(final["subtype"]) ?? "";
        var isError = final["is_error"]?.GetValueKind() == JsonValueKind.True;
        var status = subtype == "error_max_turns" ? AgentRunStatus.LoopLimitExceeded
            : isError || subtype != "success" ? AgentRunStatus.Failed
            : AgentRunStatus.Completed;

        decimal? cost = onSubscription ? 0m : null;
        if (!onSubscription && final["total_cost_usd"] is JsonValue value && value.TryGetValue<decimal>(out var usd))
            cost = usd;

        return new ForeignRunOutcome
        {
            Status = status,
            Text = Text(final["result"]) ?? (status == AgentRunStatus.Completed ? "" : $"[Claude Code: {subtype}]"),
            Turns = (int)Math.Max(turns, Number(final["num_turns"])),
            PromptTokens = (int)(input + cacheWrite + cacheRead),
            CompletionTokens = (int)Number(usage?["output_tokens"]),
            CachedTokens = (int)cacheRead,
            CostUsd = cost,
            OnSubscription = onSubscription,
            Model = model
        };
    }

    private static string? Text(JsonNode? node)
        => node is JsonValue value && value.TryGetValue<string>(out var text) ? text : null;

    private static long Number(JsonNode? node)
        => node is JsonValue value && value.TryGetValue<long>(out var number) ? number : 0;

    internal static string Tail(string stderr)
    {
        var text = stderr.Trim();
        if (text.Length == 0)
            return "";
        return "\n" + (text.Length > 1000 ? "…" + text[^1000..] : text);
    }
}