// The S6 launcher, inside the trusted bus host: it starts managed role
// sessions (packages/seat/src/session.mjs) and serves the launch socket the
// PM's `launch` tool calls. One launch at a time.
//
// A session asks over `<dataRoot>/bus-host/launch.sock` (0600) with one line,
// `{"cap": "<its capability>", "instance": "<role instance>"}`, and gets one
// line back: `{"ok": true, "result": {run, instance, harness, model}}` or
// `{"ok": false, "error": "<code>"}`. The host checks, in order:
//
//   1. identity: the capability names a role of this business
//   2. the business file's launch.instances lists the instance
//      (instance-not-listed)
//   3. the instance isn't already running (instance-running)
//   4. it resolves, has a role contract (no-role-contract) and a supported
//      harness and model (unsupported-harness)
//   5. its model is in exactly one launch.max family (unknown-model-family)
//   6. that family has room; every running session counts, the PM's too
//      (capacity-full)
//   7. the broker authorizes role.launch for the caller (its own codes:
//      launch-revoked, gated, ...)
//
// Steps 2 to 6 refuse through the broker's refuse(), so every refusal is an
// action.refused event; step 7's refusals the broker records itself. Then
// the host builds the bundle, spawns the runner, binds the run's process
// identity (the outer unshare pid) and writes the new capability on the
// runner's stdin. When the runner exits, the host ends the launch.
//
// `bus start <business> --pm` launches launch.by the same way with
// launchedBy = the business's human and no caller capability.

import { spawnSync } from "node:child_process";
import { createServer } from "node:net";
import { chmodSync, existsSync, lstatSync, mkdirSync, readFileSync, rmSync } from "node:fs";
import { join } from "node:path";
import { configDir, loadBusiness, resolveInstance, systemVars } from "../../business/src/index.mjs";
import { buildBundle, sessionModel } from "../../harness/src/bundle.mjs";
import {
  ADAPTERS,
  appendLaunchLog,
  endReason,
  family,
  launchSocketPath,
  newRun,
  readSessions,
  Registry,
  runnerOf,
  sessionEnv,
  spawnSession,
  UNSHARE,
  workspaceDir,
  writeSessionFile,
} from "../../seat/src/session.mjs";
import { cmdlineOf, startTimeOf } from "../../seat/src/proc.mjs";
import { REPO, rolesDir } from "./config.mjs";
import { CliError } from "./errors.mjs";

const PI_PACKAGE = "@earendil-works/pi-coding-agent";
const STOP_TIMEOUT_MS = 30000;
const LINE_MAX = 4096;

// A refusal the host decided; `code` goes back to the caller and to the broker.
class Refusal extends Error {
  constructor(code, message = code) {
    super(message);
    this.code = code;
  }
}

// The exact pi pin from the repository's package.json.
export function piVersion(repo = REPO) {
  try {
    const pkg = JSON.parse(readFileSync(join(repo, "package.json"), "utf8"));
    return pkg.dependencies?.[PI_PACKAGE] ?? pkg.devDependencies?.[PI_PACKAGE] ?? null;
  } catch {
    return null;
  }
}

// `claude --version` from the binary sessions run (MOSAIC_CLAUDE_BIN, else
// `claude` on PATH), or null when it doesn't answer.
export function claudeVersion(env = process.env) {
  const r = spawnSync(env.MOSAIC_CLAUDE_BIN || "claude", ["--version"], { encoding: "utf8", timeout: 10000, env });
  return r.status === 0 ? r.stdout.trim().split("\n")[0] || null : null;
}

// host: startHost()'s handle. tracker: true when the broker has task verbs for
// the business. adapters, namespace, sessionDefaults, versions and
// stopTimeoutMs exist for the tests; the command line never sets them.
export function createLauncher({
  host,
  system,
  env = process.env,
  tracker = false,
  adapters = ADAPTERS,
  namespace = true,
  sessionDefaults = {},
  versions = null,
  stopTimeoutMs = STOP_TIMEOUT_MS,
  log = (l) => process.stderr.write(`mosaic-bus: ${l}\n`),
}) {
  const dataRoot = system.dataRoot;
  const b = loadBusiness(host.business, { dir: configDir(env), rolesDir: rolesDir(env) });
  const vars = systemVars(system);

  // Sessions an earlier host left in sessions.json: it died without ending
  // them, so their runs still hold their roles. listen() ends them. A file
  // that can't be read refuses the host rather than drop them unseen.
  let leftover;
  try {
    leftover = readSessions(dataRoot).filter((s) => s.business === b.id);
  } catch (e) {
    throw new CliError(`${e.message}; check which sessions still run, then move the file aside`, 3);
  }
  const registry = new Registry(dataRoot);
  const children = new Map();
  let chain = Promise.resolve();
  let closed = false;
  let server = null;
  const sockets = new Set();

  const record = (entry) => {
    try {
      appendLaunchLog(dataRoot, b.id, entry);
    } catch (e) {
      log(`launch log: ${e.message}`);
    }
  };

  function serialize(fn) {
    const run = chain.then(fn);
    chain = run.catch(() => {});
    return run;
  }

  // Steps 2 to 6. Returns what the launch needs. Only `--pm` may name
  // launch.by itself.
  function check(instance, { pm = false } = {}) {
    if (!b.launch) throw new Refusal("launch-not-configured", `business ${b.id} has no launch block`);
    if (!(pm ? instance === b.launch.by : b.launch.instances.includes(instance))) throw new Refusal("instance-not-listed");
    if (registry.running(b.id, instance)) throw new Refusal("instance-running");
    let resolved, model;
    try {
      resolved = resolveInstance({ system: vars, business: b, instance });
      model = sessionModel(resolved);
    } catch (e) {
      throw new Refusal("unsupported-harness", e.message);
    }
    if (!resolved.contract) throw new Refusal("no-role-contract", `role ${resolved.definition} has no contract file`);
    const fam = family(model.model, b.launch.max);
    if (!fam) throw new Refusal("unknown-model-family", `model ${model.model} is in none, or more than one, of ${Object.keys(b.launch.max).join(", ")}`);
    if (registry.count(b.id, fam) >= b.launch.max[fam]) throw new Refusal("capacity-full", `${fam} sessions: ${registry.count(b.id, fam)} of ${b.launch.max[fam]}`);
    return { resolved, model, fam };
  }

  // Bundle, spawn, bind, register, hand over the capability.
  async function start({ instance, launchedBy, resolved, model, fam }) {
    const credentials = await host.op({ op: "credentialStatus", business: b.id, role: instance });
    const { run, runDir } = newRun(dataRoot, b.id);
    const workspace = workspaceDir(dataRoot, b.id, instance);
    mkdirSync(workspace, { recursive: true, mode: 0o700 });
    const sessionDir = join(runDir, "session");
    mkdirSync(sessionDir, { mode: 0o700 });
    const toolSocket = join(runDir, "tools.sock");
    const turnMarker = join(runDir, "turn.done");
    const v = versions ?? { pi: piVersion(), claude: model.harness === "claude-code" ? claudeVersion(env) : null };
    const bundle = buildBundle({
      dir: join(runDir, "bundle"),
      resolved,
      contract: readFileSync(resolved.contract, "utf8"),
      arbiter: Object.values(b.arbiters).includes(instance),
      tracker,
      credentials,
      session: { run, launchedBy, workspace, toolSocket, turnMarker },
      piVersion: v.pi,
      claudeVersion: v.claude,
    });
    const { manifest, ...files } = bundle.files;
    writeSessionFile(runDir, {
      ...sessionDefaults,
      business: b.id,
      instance,
      run,
      launchedBy,
      harness: model.harness,
      provider: model.provider,
      model: model.model,
      brokerSocket: host.path,
      launchSocket: launchSocketPath(dataRoot),
      workspace,
      sessionDir,
      adapter: adapters[model.harness],
      bundle: files,
      toolSocket,
      turnMarker,
    });

    const child = spawnSession({ runDir, env: sessionEnv(env, run), namespace });
    let bound = false;
    let entry = null;
    const exited = new Promise((resolve) => child.once("close", (code, signal) => resolve({ code, signal })));
    child.on("error", (e) => log(`run ${run}: ${e.message}`));
    child.stdin.on("error", () => {});
    try {
      if (child.pid === undefined) throw new Error("the session process did not start");
      const outerStart = startTimeOf(child.pid);
      const runner = await runnerOf(child, { namespace });
      if (!outerStart) throw new Error("the session process exited at once");
      const launch = await host.bindLaunch({ business: b.id, role: instance, run, harness: model.harness, pid: child.pid, startTime: outerStart });
      bound = true;
      entry = {
        business: b.id, instance, run, launchedBy, harness: model.harness, model: model.model, family: fam,
        pid: child.pid, startTime: outerStart, runnerPid: runner.pid, runnerStartTime: runner.startTime, runDir, startedAt: new Date().toISOString(),
      };
      registry.add(entry);
      child.stdin.end(`${JSON.stringify({ cap: launch.cap })}\n`);
    } catch (e) {
      child.kill("SIGKILL");
      await exited;
      if (bound) await endRun(run, "failed", null);
      throw new Refusal("launch-failed", e.message);
    }
    children.set(run, exited);
    exited.then(async ({ code, signal }) => {
      const reason = endReason(code, signal);
      try {
        await endRun(run, reason, signal ? null : code);
        registry.remove(b.id, run);
        record({ event: "end", instance, run, reason, exitCode: code, signal });
        log(`run ${run} (${instance}) ended: ${reason}`);
      } catch (e) {
        log(`run ${run}: ${e.message}`);
      } finally {
        children.delete(run);
      }
    });
    record({ event: "launch", instance, run, launchedBy, harness: model.harness, model: model.model, family: fam, pid: child.pid, runnerPid: entry.runnerPid, manifest });
    return { run, instance, harness: model.harness, model: model.model };
  }

  async function endRun(run, reason, exitCode) {
    try {
      await host.op({ op: "endLaunch", record: { business: b.id, run, reason, exitCode } });
    } catch (e) {
      log(`run ${run}: endLaunch refused: ${e.code ?? e.message}`);
    }
  }

  // A launch a session asked for. Resolves to the reply line's object.
  function fromSession(cap, instance) {
    return serialize(async () => {
      if (closed) return { ok: false, error: "host-closing" };
      let who;
      try {
        who = await host.op({ op: "identity", cap });
      } catch (e) {
        return { ok: false, error: e.code ?? "unauthenticated" };
      }
      if (!who.role || who.business !== b.id) {
        await host.op({ op: "refuse", cap, code: "not-a-role" }).catch(() => {});
        return { ok: false, error: "not-a-role" };
      }
      let checked;
      try {
        if (typeof instance !== "string") throw new Refusal("invalid-request");
        checked = check(instance);
      } catch (e) {
        if (!(e instanceof Refusal)) throw e;
        await host.op({ op: "refuse", cap, code: e.code }).catch(() => {});
        record({ event: "refused", by: who.role, instance, code: e.code, why: e.message });
        return { ok: false, error: e.code };
      }
      try {
        await host.op({ op: "authorizeLaunch", cap, instance });
      } catch (e) {
        record({ event: "refused", by: who.role, instance, code: e.code ?? "not-authorized" });
        return { ok: false, error: e.code ?? "not-authorized" };
      }
      try {
        return { ok: true, result: await start({ instance, launchedBy: who.role, ...checked }) };
      } catch (e) {
        const code = e instanceof Refusal ? e.code : "launch-failed";
        log(`launch of ${instance} for ${who.role} failed: ${e.message}`);
        await host.op({ op: "refuse", cap, code }).catch(() => {});
        record({ event: "refused", by: who.role, instance, code, why: e.message });
        return { ok: false, error: code };
      }
    });
  }

  // `bus start --pm`: the business's launcher instance, launched by the human.
  function launchPm() {
    return serialize(async () => {
      if (!b.launch) throw new CliError(`business ${b.id} has no launch block, so --pm has nothing to launch`, 3);
      try {
        return await start({ instance: b.launch.by, launchedBy: b.human, ...check(b.launch.by, { pm: true }) });
      } catch (e) {
        if (!(e instanceof Refusal)) throw e;
        record({ event: "refused", by: b.human, instance: b.launch.by, code: e.code, why: e.message });
        throw new CliError(`PM launch refused: ${e.code}${e.message !== e.code ? ` (${e.message})` : ""}`, 3);
      }
    });
  }

  // The earlier host's sessions. Their capabilities died with its broker, so
  // one that still runs can do nothing: kill it (the namespace takes its
  // turn with it). Then end each run in the bus, which releases its role.
  // This broker never bound those runs, so each is bound again first with
  // its identical launch record, which the broker accepts.
  async function recover() {
    for (const s of leftover) {
      if (startTimeOf(s.pid) === s.startTime && (cmdlineOf(s.pid) ?? [])[0] === UNSHARE[0]) {
        try {
          process.kill(s.pid, "SIGKILL");
        } catch {}
        const end = Date.now() + 5000;
        while (startTimeOf(s.pid) === s.startTime && Date.now() < end) await new Promise((r) => setTimeout(r, 20));
      }
      try {
        await host.bindLaunch({ business: b.id, role: s.instance, run: s.run, harness: s.harness, pid: s.pid, startTime: s.startTime });
      } catch (e) {
        // A host that died after ending the run but before updating sessions.json.
        if (e.code === "run-ended") log(`run ${s.run} (${s.instance}) from an earlier host was already ended`);
        else log(`run ${s.run} (${s.instance}) from an earlier host: not ended, bindLaunch refused: ${e.code ?? e.message}`);
        continue;
      }
      await endRun(s.run, "host-lost", null);
      record({ event: "end", instance: s.instance, run: s.run, reason: "host-lost", exitCode: null, signal: null });
      log(`run ${s.run} (${s.instance}) from an earlier host ended: host-lost`);
    }
    leftover = [];
  }

  async function listen() {
    await recover();
    const path = launchSocketPath(dataRoot);
    if (existsSync(path)) {
      if (!lstatSync(path).isSocket()) throw new CliError(`${path} exists and isn't a socket`, 3);
      rmSync(path);
    }
    server = createServer((socket) => {
      sockets.add(socket);
      socket.once("close", () => sockets.delete(socket));
      let buf = "";
      let answered = false;
      const reply = (obj) => {
        if (answered) return;
        answered = true;
        socket.end(`${JSON.stringify(obj)}\n`);
      };
      socket.setTimeout(10000, () => reply({ ok: false, error: "invalid-request" }));
      socket.on("error", () => {});
      socket.on("data", (chunk) => {
        if (answered) return;
        buf += chunk;
        if (buf.length > LINE_MAX) return reply({ ok: false, error: "invalid-request" });
        const nl = buf.indexOf("\n");
        if (nl < 0) return;
        socket.setTimeout(0);
        let req;
        try {
          req = JSON.parse(buf.slice(0, nl));
        } catch {
          return reply({ ok: false, error: "invalid-request" });
        }
        if (typeof req?.cap !== "string" || !/^[0-9a-f]{64}$/.test(req.cap)) return reply({ ok: false, error: "unauthenticated" });
        fromSession(req.cap, req.instance).then(reply, (e) => {
          log(`launch socket: ${e.message}`);
          reply({ ok: false, error: "launch-failed" });
        });
      });
    });
    // bus-host/ is 0700, so the moment before the chmod exposes nothing.
    await new Promise((resolve, reject) => {
      server.once("error", reject);
      server.listen(path, resolve);
    });
    chmodSync(path, 0o600);
  }

  // SIGTERM every runner, wait, then end what's left. Runs before the host
  // stops the broker, so endLaunch still works.
  async function close() {
    closed = true;
    if (server) {
      // server.close waits for every connection, and a client that never
      // ends its side (or never sends) would hold it; so they go first.
      const stopped = new Promise((r) => server.close(r));
      for (const socket of sockets) socket.destroy();
      await stopped;
      rmSync(launchSocketPath(dataRoot), { force: true });
    }
    await chain;
    // Again every second: a runner still starting has no handler yet, and as
    // pid 1 of its namespace it never sees a signal sent before it has one.
    const term = () => {
      for (const s of registry.sessions) {
        try {
          if (startTimeOf(s.runnerPid) === s.runnerStartTime) process.kill(s.runnerPid, "SIGTERM");
        } catch {}
      }
    };
    term();
    const again = setInterval(term, 1000);
    const pending = [...children.values()];
    const timer = setTimeout(() => {
      for (const s of registry.sessions) {
        try {
          if (startTimeOf(s.pid) === s.startTime) process.kill(s.pid, "SIGKILL");
        } catch {}
      }
    }, stopTimeoutMs);
    await Promise.all(pending);
    // The exit handlers run on the same tick as the close events; let them finish.
    while (children.size) await new Promise((r) => setTimeout(r, 20));
    clearInterval(again);
    clearTimeout(timer);
  }

  host.beforeClose(close);
  return { business: b, registry, listen, launchPm, fromSession, close };
}