import type { ChildProcessWithoutNullStreams } from "node:child_process";
import { Readable, Writable } from "node:stream";
import * as acp from "@agentclientprotocol/sdk";
import type { AgentCapabilities, InitializeResponse, RequestPermissionRequest, RequestPermissionResponse, SessionNotification } from "@agentclientprotocol/sdk";
import type { PermissionPolicy } from "../config.js";

export type SafeActivityCategory = "read" | "write" | "execute" | "search" | "delegate" | "other";

export interface AcpClientOptions {
  initializeTimeoutMs: number;
  policy: PermissionPolicy;
  onSessionActivity?: (category?: SafeActivityCategory) => void;
  forbidToolActivity?: boolean;
  onToolViolation?: () => void;
}

export class AcpClient {
  private readonly connection: acp.ClientConnection;
  private capabilities: AgentCapabilities = {};
  private activeSessionId?: string;
  private collecting = false;
  private toolViolation = false;
  private violationReject?: (error: Error) => void;
  private chunks: string[] = [];

  constructor(private readonly child: ChildProcessWithoutNullStreams, private readonly options: AcpClientOptions) {
    const app = acp.client({ name: "gori-agent" })
      .onRequest(acp.methods.client.session.requestPermission, ({ params }) => {
        if (options.forbidToolActivity) this.recordToolViolation();
        return decidePermission(params, options.policy);
      })
      .onNotification(acp.methods.client.session.update, ({ params }) => this.handleUpdate(params));
    const stream = acp.ndJsonStream(
      Writable.toWeb(child.stdin) as WritableStream<Uint8Array>,
      Readable.toWeb(child.stdout) as ReadableStream<Uint8Array>
    );
    this.connection = app.connect(stream);
  }

  async initialize(): Promise<InitializeResponse> {
    const response = await withTimeout(this.connection.agent.request(acp.methods.agent.initialize, {
      protocolVersion: acp.PROTOCOL_VERSION,
      clientCapabilities: {},
      clientInfo: { name: "gori-agent", version: "0.1.0" }
    }), this.options.initializeTimeoutMs, "ACP initialize timed out");
    if (response.protocolVersion !== acp.PROTOCOL_VERSION) throw new Error(`Unsupported ACP protocol version ${response.protocolVersion}`);
    this.capabilities = response.agentCapabilities || {};
    return response;
  }

  async newSession(cwd: string): Promise<string> {
    const response = await withTimeout(
      this.connection.agent.request(acp.methods.agent.session.new, { cwd, mcpServers: [] }),
      this.options.initializeTimeoutMs,
      "ACP session/new timed out"
    );
    this.activeSessionId = response.sessionId;
    if (this.toolViolation) throw new Error("Assistant session attempted forbidden tool activity");
    return response.sessionId;
  }

  async resumeSession(sessionId: string, cwd: string): Promise<void> {
    this.collecting = false;
    this.chunks = [];
    this.activeSessionId = sessionId;
    const request = <T>(promise: Promise<T>, operation: string): Promise<T> => withTimeout(
      promise,
      this.options.initializeTimeoutMs,
      `ACP session/${operation} timed out`
    );
    try {
      if (this.capabilities.sessionCapabilities?.resume) {
        try {
          await request(this.connection.agent.request(acp.methods.agent.session.resume, { sessionId, cwd, mcpServers: [] }), "resume");
        } catch (error) {
          if (!this.capabilities.loadSession) throw error;
          await request(this.connection.agent.request(acp.methods.agent.session.load, { sessionId, cwd, mcpServers: [] }), "load");
        }
      } else if (this.capabilities.loadSession) {
        await request(this.connection.agent.request(acp.methods.agent.session.load, { sessionId, cwd, mcpServers: [] }), "load");
      } else {
        throw new Error("ACP backend cannot resume or load sessions");
      }
    } catch (error) {
      this.activeSessionId = undefined;
      throw error;
    }
    this.chunks = [];
  }

  async prompt(text: string, cancellationSignal?: AbortSignal): Promise<string> {
    if (!this.activeSessionId) throw new Error("ACP session is not active");
    if (this.toolViolation) throw new Error("Assistant session attempted forbidden tool activity");
    this.chunks = [];
    this.collecting = true;
    const violation = new Promise<never>((_resolve, reject) => { this.violationReject = reject; });
    try {
      await Promise.race([
        this.connection.agent.request(acp.methods.agent.session.prompt, {
          sessionId: this.activeSessionId,
          prompt: [{ type: "text", text }]
        }, cancellationSignal ? { cancellationSignal } : undefined),
        violation
      ]);
      if (this.toolViolation) throw new Error("Assistant session attempted forbidden tool activity");
      return this.chunks.join("").trim();
    } finally {
      this.violationReject = undefined;
      this.collecting = false;
    }
  }

  async settleIsolation(): Promise<void> {
    if (!this.options.forbidToolActivity) return;
    await new Promise((resolve) => setTimeout(resolve, 50));
    if (this.toolViolation) throw new Error("Assistant session attempted forbidden tool activity");
  }

  async cancel(): Promise<void> {
    if (this.activeSessionId) await this.connection.agent.notify(acp.methods.agent.session.cancel, { sessionId: this.activeSessionId });
  }

  async closeSession(): Promise<void> {
    if (this.activeSessionId && this.capabilities.sessionCapabilities?.close) {
      await this.connection.agent.request(acp.methods.agent.session.close, { sessionId: this.activeSessionId }).catch(() => undefined);
    }
  }

  close(error?: unknown): void { this.connection.close(error); }

  private handleUpdate(notification: SessionNotification): void {
    if (this.activeSessionId && notification.sessionId !== this.activeSessionId) return;
    const update = notification.update;
    const category = activityCategory(update);
    if (category && this.options.forbidToolActivity) this.recordToolViolation();
    this.options.onSessionActivity?.(category);
    if (!this.collecting || notification.sessionId !== this.activeSessionId) return;
    if (update.sessionUpdate === "agent_message_chunk" && update.content.type === "text") this.chunks.push(update.content.text);
  }

  private recordToolViolation(): void {
    if (this.toolViolation) return;
    this.toolViolation = true;
    this.violationReject?.(new Error("Assistant session attempted forbidden tool activity"));
    this.options.onToolViolation?.();
  }
}

function activityCategory(update: SessionNotification["update"]): SafeActivityCategory | undefined {
  if (!String(update.sessionUpdate).startsWith("tool_call")) return undefined;
  const record = update as unknown as Record<string, unknown>;
  const raw = JSON.stringify({ kind: record.kind, name: record.name, title: record.title }).toLowerCase();
  if (/read|view|fetch/.test(raw)) return "read";
  if (/grep|glob|search|find/.test(raw)) return "search";
  if (/write|edit|patch/.test(raw)) return "write";
  if (/bash|terminal|execute|command/.test(raw)) return "execute";
  if (/agent|delegate|subagent/.test(raw)) return "delegate";
  return "other";
}

export function decidePermission(request: RequestPermissionRequest, policy: PermissionPolicy): RequestPermissionResponse {
  if (policy.mode === "deny") return reject(request);
  const allowOption = request.options.find((option) => option.kind === "allow_once") || request.options.find((option) => option.kind === "allow_always");
  if (!allowOption) return reject(request);
  if (policy.mode === "auto") return { outcome: { outcome: "selected", optionId: allowOption.optionId } };

  const name = typeof request.toolCall.name === "string" ? request.toolCall.name.trim().toLowerCase() : "";
  if (!name || !policy.allowedTools.some((tool) => name === tool.trim().toLowerCase())) return reject(request);
  if (name === "bash" || name === "terminal") {
    if (policy.allowedCommandPatterns.length === 0) return reject(request);
    const input = commandInput(request.toolCall.rawInput);
    if (!input || !policy.allowedCommandPatterns.some((pattern) => fullMatch(pattern, input))) return reject(request);
  }
  return { outcome: { outcome: "selected", optionId: allowOption.optionId } };
}

function commandInput(rawInput: unknown): string | undefined {
  if (typeof rawInput === "string") return rawInput;
  if (typeof rawInput === "object" && rawInput !== null && !Array.isArray(rawInput)) {
    const record = rawInput as Record<string, unknown>;
    if (Object.keys(record).some((key) => !["command", "timeout", "timeoutMs"].includes(key))) return undefined;
    return typeof record.command === "string" ? record.command : undefined;
  }
  return undefined;
}

function fullMatch(pattern: string, input: string): boolean {
  const match = new RegExp(pattern).exec(input);
  return match?.index === 0 && match[0] === input;
}

function reject(request: RequestPermissionRequest): RequestPermissionResponse {
  const option = request.options.find((item) => item.kind === "reject_once") || request.options.find((item) => item.kind === "reject_always");
  return option ? { outcome: { outcome: "selected", optionId: option.optionId } } : { outcome: { outcome: "cancelled" } };
}

async function withTimeout<T>(promise: Promise<T>, timeoutMs: number, message: string): Promise<T> {
  let timer: NodeJS.Timeout | undefined;
  try {
    return await Promise.race([promise, new Promise<T>((_resolve, reject) => { timer = setTimeout(() => reject(new Error(message)), timeoutMs); })]);
  } finally {
    if (timer) clearTimeout(timer);
  }
}