import { SESSION_NIX_COMMAND } from "../constants.js";

export type DshNixArgs =
  | { kind: "help" }
  | { kind: "fresh" }
  | { kind: "quit" }
  | { kind: "error"; error: string };

export function dshNixUsage(): string {
  return [
    `Usage: /${SESSION_NIX_COMMAND}`,
    `       /${SESSION_NIX_COMMAND} quit`,
    `       /${SESSION_NIX_COMMAND} help`,
    "",
    "Deletes the current session and starts a new one, then switches the live view to it.",
    "On macOS the old session directory goes to Trash; elsewhere it is permanently removed.",
    `/${SESSION_NIX_COMMAND} quit deletes the current session and then exits DSH.`,
  ].join("\n");
}

export function parseDshNixArgs(args: string): DshNixArgs {
  const trimmed = args.trim();
  if (!trimmed) {
    return { kind: "fresh" };
  }

  const parts = trimmed.split(/\s+/u);
  const command = parts[0]?.toLowerCase();
  if (!command) {
    return { kind: "fresh" };
  }

  if (command === "help") {
    return { kind: "help" };
  }

  if (command === "quit" || command === "exit") {
    return parts.length === 1
      ? { kind: "quit" }
      : { kind: "error", error: `/${SESSION_NIX_COMMAND} quit does not accept additional arguments.` };
  }

  return { kind: "error", error: `Unknown argument: ${trimmed}` };
}