/**
 * @file startSession.ts — starting a session in a workspace's first free tab
 * (`POST /api/lanes/:id/start` with `slot: "auto"`) and the small pane-slot
 * helpers around it. Kept out of `WorkspaceHome.tsx` so the sidebar's session
 * list can use them without pulling the whole home (and react-markdown) into
 * the main bundle.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

import i18n from "../../i18n";
import { api, type RunHandle } from "../../lib/api";
import { MAX_SLOTS, slotOfKey } from "../../lib/paneLayout";

/** The tmux session a pane slot of a lane owns (server/lib/pty-run.js). */
export function paneRunId(laneId: number, slot: number): string {
  return slot ? `agenthub-lane-${laneId}-${slot}` : `agenthub-lane-${laneId}`;
}

/**
 * Start a session in the workspace's first free tab. The SERVER picks the slot
 * (`slot: "auto"`, under its lane lock), because any list the client holds may
 * already be stale. Resolves to the run id it opened — or, when the session to
 * resume is already open in a tab (`ESESSIONLIVE`), to that tab, so a second
 * `--resume` of one session never starts.
 */
export async function startInFreeTab(
  laneId: number,
  body: Record<string, unknown>
): Promise<string> {
  return (await startInFreeTabDetailed(laneId, body)).runId;
}

/** The workspace a pane belongs to, from its tmux name `agenthub-lane-<id>[-slot]`. */
export function laneOfRun(runId: string): number | null {
  const m = /^agenthub-lane-(\d+)(?:-[1-9])?$/.exec(runId);
  return m ? Number(m[1]) : null;
}

/** `startInFreeTab`, saying also whether the run was STARTED or an existing
 *  pane already held the session (`held` — nothing was sent to it), and the
 *  workspace that pane belongs to (a nested folder's workspace may hold it). */
export async function startInFreeTabDetailed(
  laneId: number,
  body: Record<string, unknown>
): Promise<{ runId: string; laneId: number; held: boolean }> {
  try {
    const r = await api.lanes.action(laneId, "start", { ...body, slot: "auto" });
    return { runId: r.run_id ?? paneRunId(laneId, 0), laneId, held: false };
  } catch (err) {
    const e = err as { code?: string; runId?: string };
    if (e.code === "ESESSIONLIVE" && e.runId)
      return { runId: e.runId, laneId: laneOfRun(e.runId) ?? laneId, held: true };
    if (e.code === "ERUNLIVE") throw new Error(i18n.t("lanes:home.allBusy"));
    throw err;
  }
}

/** The first pane slot with no live run, or null when all ten are busy. */
export function freeSlot(laneId: number, runs: RunHandle[]): number | null {
  const busy = new Set(
    runs
      .filter((r) => r.laneId === laneId && r.status === "running")
      .map((r) => slotOfKey(r.slot ?? 0))
  );
  for (let s = 0; s < MAX_SLOTS; s++) if (!busy.has(s)) return s;
  return null;
}