#!/usr/bin/env bun
/**
 * gstack-dispatch-daemon — accept and execute coding tasks from orchestrators
 *
 * Watches ~/.gstack/dispatch/ for new dispatch files, validates them against
 * the JSON schema, spawns Claude Code sessions with scoped permissions, and
 * reports completion back via Clawvisor callback or local disk.
 *
 * Usage:
 *   gstack-dispatch-daemon                    # foreground mode
 *   gstack-dispatch-daemon --max-concurrent 3 # custom concurrency
 *   gstack-dispatch-daemon --local-only       # no Clawvisor, filesystem approval
 */

import { watch } from "fs";
import { readdir, readFile, writeFile, mkdir, unlink } from "fs/promises";
import { spawn } from "child_process";
import { join, basename } from "path";
import { existsSync } from "fs";

// --- Config ---
const GSTACK_HOME = process.env.GSTACK_HOME || join(process.env.HOME!, ".gstack");
const DISPATCH_DIR = join(GSTACK_HOME, "dispatch");
const COMPLETED_DIR = join(DISPATCH_DIR, "completed");
const AUDIT_LOG = join(DISPATCH_DIR, "audit.jsonl");
const HEARTBEAT_FILE = join(DISPATCH_DIR, ".daemon-heartbeat");
const MAX_CONCURRENT = parseInt(process.argv.find((_, i, a) => a[i - 1] === "--max-concurrent") || "2");
const LOCAL_ONLY = process.argv.includes("--local-only");

// --- State ---
const activeSessions = new Map<string, { proc: ReturnType<typeof spawn>; startedAt: number; project: string }>();
const queue: string[] = [];
let shuttingDown = false;

// --- Startup validation ---
async function validateStartup() {
  await mkdir(DISPATCH_DIR, { recursive: true });
  await mkdir(COMPLETED_DIR, { recursive: true });

  // Check claude binary
  try {
    const which = Bun.spawnSync(["which", "claude"]);
    if (which.exitCode !== 0) {
      console.error("[daemon] claude binary not found in PATH");
      process.exit(1);
    }
  } catch {
    console.error("[daemon] could not verify claude binary");
    process.exit(1);
  }

  console.log(`[daemon] started (max_concurrent=${MAX_CONCURRENT}, local_only=${LOCAL_ONLY})`);
  console.log(`[daemon] watching ${DISPATCH_DIR}`);
}

// --- Audit logging ---
async function audit(event: string, dispatchId: string, details?: Record<string, unknown>) {
  const entry = JSON.stringify({
    ts: new Date().toISOString(),
    event,
    dispatch_id: dispatchId,
    ...details,
  });
  await Bun.write(Bun.file(AUDIT_LOG), (existsSync(AUDIT_LOG) ? await Bun.file(AUDIT_LOG).text() : "") + entry + "\n");
}

// --- Heartbeat ---
let heartbeatInterval: ReturnType<typeof setInterval>;
async function writeHeartbeat() {
  const data = JSON.stringify({
    ts: new Date().toISOString(),
    active: activeSessions.size,
    queued: queue.length,
    pid: process.pid,
  });
  await Bun.write(HEARTBEAT_FILE, data);
}

// --- Schema validation (lightweight, no ajv dependency) ---
function validateDispatch(data: unknown): data is DispatchFile {
  if (!data || typeof data !== "object") return false;
  const d = data as Record<string, unknown>;
  if (typeof d.id !== "string" || !d.id.startsWith("dispatch-")) return false;
  if (typeof d.dispatched_by !== "string") return false;
  if (typeof d.task !== "string" || d.task.length === 0) return false;
  if (typeof d.project !== "string") return false;
  if (typeof d.project_dir !== "string") return false;
  if (d.ttl_seconds !== undefined && (typeof d.ttl_seconds !== "number" || d.ttl_seconds < 60 || d.ttl_seconds > 86400)) return false;
  if (d.target_agent !== undefined && !["claude", "codex", "cursor", "gemini"].includes(d.target_agent as string)) return false;
  return true;
}

interface DispatchFile {
  id: string;
  dispatched_by: string;
  task: string;
  project: string;
  project_dir: string;
  target_agent?: string;
  learnings?: string[];
  constraints?: string[];
  callback_url?: string;
  clawvisor_task_id?: string;
  source_signature?: string;
  ttl_seconds?: number;
}

// --- Session spawning ---
async function spawnSession(dispatchPath: string) {
  const raw = await readFile(dispatchPath, "utf-8");
  let dispatch: DispatchFile;
  try {
    dispatch = JSON.parse(raw);
  } catch {
    await audit("schema_invalid", basename(dispatchPath), { error: "invalid JSON" });
    await unlink(dispatchPath).catch(() => {});
    return;
  }

  if (!validateDispatch(dispatch)) {
    await audit("schema_invalid", dispatch.id || basename(dispatchPath), { error: "schema validation failed" });
    await unlink(dispatchPath).catch(() => {});
    return;
  }

  // Only claude is supported in v0
  if (dispatch.target_agent && dispatch.target_agent !== "claude") {
    await audit("unsupported_agent", dispatch.id, { target_agent: dispatch.target_agent });
    await writeCompletion(dispatch, "failed", 0, { error: `unsupported agent: ${dispatch.target_agent}` });
    await unlink(dispatchPath).catch(() => {});
    return;
  }

  // Concurrency check
  if (activeSessions.size >= MAX_CONCURRENT) {
    queue.push(dispatchPath);
    await audit("queued", dispatch.id, { queue_depth: queue.length });
    console.log(`[daemon] queued ${dispatch.id} (${queue.length} in queue)`);
    return;
  }

  await executeSession(dispatchPath, dispatch);
}

async function executeSession(dispatchPath: string, dispatch: DispatchFile, retryCount = 0) {
  await audit("spawned", dispatch.id, { project: dispatch.project, retry: retryCount });
  console.log(`[daemon] spawning session for ${dispatch.id} (project: ${dispatch.project})`);

  const projectDir = dispatch.project_dir.replace("~", process.env.HOME!);
  const startedAt = Date.now();

  // Build the prompt
  let prompt = `Load gstack. Dispatch ID: ${dispatch.id}. Task: ${dispatch.task}`;
  if (dispatch.constraints?.length) {
    prompt += `\nConstraints: ${dispatch.constraints.join(", ")}`;
  }
  if (dispatch.learnings?.length) {
    prompt += `\nRelevant learnings from prior sessions:\n${dispatch.learnings.slice(0, 5).join("\n")}`;
  }

  const proc = spawn("claude", [
    "--print",
    "--permission-mode", "acceptEdits",
    "--output-format", "stream-json",
    "--verbose",
    "--project", projectDir,
    prompt,
  ], {
    cwd: projectDir,
    stdio: ["ignore", "pipe", "pipe"],
    env: { ...process.env, GSTACK_DISPATCH_ID: dispatch.id },
  });

  activeSessions.set(dispatch.id, { proc, startedAt, project: dispatch.project });

  let stdout = "";
  let stderr = "";
  proc.stdout?.on("data", (chunk: Buffer) => { stdout += chunk.toString(); });
  proc.stderr?.on("data", (chunk: Buffer) => { stderr += chunk.toString(); });

  // TTL enforcement
  const ttl = (dispatch.ttl_seconds || 3600) * 1000;
  const ttlTimer = setTimeout(() => {
    console.log(`[daemon] TTL exceeded for ${dispatch.id}, killing`);
    proc.kill("SIGTERM");
    setTimeout(() => proc.kill("SIGKILL"), 5000);
  }, ttl);

  proc.on("close", async (code) => {
    clearTimeout(ttlTimer);
    activeSessions.delete(dispatch.id);
    const duration = Math.round((Date.now() - startedAt) / 1000);

    if (code === 0) {
      await audit("completed", dispatch.id, { duration, exit_code: code });
      await writeCompletion(dispatch, "completed", duration, { output_length: stdout.length });
      console.log(`[daemon] ${dispatch.id} completed (${duration}s)`);
    } else {
      // Error classification for smart retry
      const errorType = classifyError(stderr, code);

      if (retryCount === 0 && (errorType === "rate_limit" || errorType === "tool_failure")) {
        console.log(`[daemon] ${dispatch.id} failed (${errorType}), retrying...`);
        await audit("retried", dispatch.id, { error_type: errorType, retry: retryCount + 1 });

        if (errorType === "rate_limit") {
          await new Promise(r => setTimeout(r, 30000)); // 30s backoff
        }
        await executeSession(dispatchPath, dispatch, retryCount + 1);
        return;
      }

      await audit("failed", dispatch.id, { duration, exit_code: code, error_type: errorType, retry_count: retryCount });
      await writeCompletion(dispatch, "failed", duration, {
        error: stderr.slice(0, 500),
        error_type: errorType,
        retry_count: retryCount
      });
      console.log(`[daemon] ${dispatch.id} failed (${errorType}, ${duration}s)`);
    }

    // Remove dispatch file
    await unlink(dispatchPath).catch(() => {});

    // Process queue
    if (queue.length > 0 && !shuttingDown) {
      const next = queue.shift()!;
      await spawnSession(next);
    }
  });
}

// --- Error classification ---
function classifyError(stderr: string, code: number | null): string {
  const lower = stderr.toLowerCase();
  if (lower.includes("rate limit") || lower.includes("429") || lower.includes("too many requests")) return "rate_limit";
  if (lower.includes("context") && (lower.includes("overflow") || lower.includes("too long") || lower.includes("token"))) return "context_overflow";
  if (lower.includes("i can't") || lower.includes("unable to") || lower.includes("not possible")) return "logic_error";
  if (code === 137 || code === 143) return "timeout"; // SIGKILL or SIGTERM
  return "tool_failure";
}

// --- Completion report ---
async function writeCompletion(dispatch: DispatchFile, status: string, duration: number, extra?: Record<string, unknown>) {
  const report = {
    dispatch_id: dispatch.id,
    status,
    duration,
    target_agent: dispatch.target_agent || "claude",
    ...extra,
  };

  const reportPath = join(COMPLETED_DIR, `${dispatch.id}.json`);
  await writeFile(reportPath, JSON.stringify(report, null, 2));

  // Callback via Clawvisor (or skip in local-only mode)
  if (dispatch.callback_url && !LOCAL_ONLY) {
    try {
      const res = await fetch(dispatch.callback_url, {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify(report),
      });
      await audit("callback_sent", dispatch.id, { status: res.status });
    } catch (e) {
      await audit("callback_failed", dispatch.id, { error: String(e) });
      console.error(`[daemon] callback failed for ${dispatch.id}: ${e}`);
    }
  }
}

// --- Graceful shutdown ---
function shutdown() {
  if (shuttingDown) return;
  shuttingDown = true;
  console.log(`[daemon] shutting down (${activeSessions.size} active, ${queue.length} queued)`);

  // Clear queue
  queue.length = 0;

  // Wait for active sessions to finish (with 60s timeout)
  if (activeSessions.size === 0) {
    clearInterval(heartbeatInterval);
    process.exit(0);
  }

  setTimeout(() => {
    console.log("[daemon] timeout waiting for sessions, force killing");
    for (const [id, { proc }] of activeSessions) {
      proc.kill("SIGKILL");
    }
    clearInterval(heartbeatInterval);
    process.exit(1);
  }, 60000);
}

process.on("SIGTERM", shutdown);
process.on("SIGINT", shutdown);

// --- Main ---
async function main() {
  await validateStartup();

  // Start heartbeat
  heartbeatInterval = setInterval(writeHeartbeat, 30000);
  await writeHeartbeat();

  // Process existing dispatch files
  const existing = await readdir(DISPATCH_DIR).catch(() => [] as string[]);
  for (const f of existing) {
    if (f.endsWith(".json") && f.startsWith("dispatch-")) {
      await spawnSession(join(DISPATCH_DIR, f));
    }
  }

  // Watch for new files
  watch(DISPATCH_DIR, async (eventType, filename) => {
    if (shuttingDown) return;
    if (!filename || !filename.endsWith(".json") || !filename.startsWith("dispatch-")) return;

    const filepath = join(DISPATCH_DIR, filename);
    if (!existsSync(filepath)) return; // file was deleted

    // Small delay to ensure file is fully written
    await new Promise(r => setTimeout(r, 100));

    await audit("received", filename);
    await spawnSession(filepath);
  });

  console.log("[daemon] ready");
}

main().catch((e) => {
  console.error("[daemon] fatal:", e);
  process.exit(1);
});