// AXIS-facing state names are a view over the native task and interpreter
// states. Keep sim_task.v1 unchanged and expose this as an additive payload.
export const AXIS_STATES = Object.freeze(["ESTOP", "ESTOP_RESET", "OFF", "ON", "HOME", "IDLE", "RUNNING", "PAUSED"]);
export const LINUXCNC_STATE_CONSTANTS = Object.freeze({
  STATE_ESTOP: 1,
  STATE_ESTOP_RESET: 2,
  STATE_OFF: 3,
  STATE_ON: 4,
  MODE_MANUAL: 1,
  MODE_AUTO: 2,
  MODE_MDI: 3,
  INTERP_IDLE: 1,
  INTERP_READING: 2,
  INTERP_PAUSED: 3,
  INTERP_WAITING: 4,
});
export const AXIS_TRANSITIONS = Object.freeze({
  ESTOP: ["ESTOP", "ESTOP_RESET"],
  ESTOP_RESET: ["ESTOP", "ON", "OFF"],
  OFF: ["OFF", "ESTOP", "ESTOP_RESET"],
  ON: ["ON", "OFF", "ESTOP", "HOME", "IDLE", "RUNNING", "PAUSED"],
  HOME: ["HOME", "ON", "IDLE", "ESTOP"],
  IDLE: ["IDLE", "RUNNING", "PAUSED", "HOME", "ESTOP", "OFF"],
  RUNNING: ["RUNNING", "PAUSED", "IDLE", "ESTOP"],
  PAUSED: ["PAUSED", "RUNNING", "IDLE", "ESTOP"],
});

function programActivity(task, program) {
  if (task?.state === "PAUSED" || program?.program_status === "paused") return "PAUSED";
  if (task?.state === "RUNNING" || program?.program_status === "running") return "RUNNING";
  return "IDLE";
}

export function axisState({ task = {}, program = {}, motion = {}, devices = {}, device_io = {}, io = {}, action = null, payload = {} } = {}) {
  const taskState = String(task.state ?? "NEW").toUpperCase();
  const ioState = io?.state ?? io ?? device_io?.state ?? device_io ?? {};
  const hasIoState = typeof ioState.estop === "boolean" || typeof ioState.estop === "number";
  const ioEstop = hasIoState && Boolean(ioState.estop);
  const ioReady = typeof ioState.ready === "boolean" || typeof ioState.ready === "number" ? Boolean(ioState.ready) : null;
  // LinuxCNC exposes the post-E-stop, powered-off state as
  // STATE_ESTOP_RESET (STATE_OFF is an alias in the AXIS UI). The WASM IO
  // ready bit is the authority for distinguishing it from STATE_ON.
  const estopReset = hasIoState && !ioEstop && ioReady === false;
  let machineState = ioEstop || ["ESTOP", "FAULT"].includes(taskState) ? "ESTOP" : estopReset ? "ESTOP_RESET" : ioReady === false ? "OFF" : ["READY", "RUNNING", "PAUSED", "STOPPED"].includes(taskState) ? "ON" : "OFF";
  let operationState = programActivity(task, program);
  if (action === "ESTOP" && payload.active === true) machineState = "ESTOP";
  if (action === "ESTOP" && payload.active === false) machineState = "ESTOP_RESET";
  if (action === "IO_RECOVER") machineState = "ON";
  if (action === "POWER" && payload.active === true) machineState = "ON";
  if (action === "POWER" && payload.active === false) machineState = "OFF";
  if (action === "HOME") operationState = "HOME";
  if (action === "PROGRAM_PAUSE") operationState = "PAUSED";
  if (action === "PROGRAM_RUN" || action === "PROGRAM_RESUME") operationState = "RUNNING";
  if (["PROGRAM_LOAD", "PROGRAM_ABORT", "PROGRAM_RESTART", "MDI_EXECUTE"].includes(action)) operationState = "IDLE";
  const state = machineState === "ESTOP" || machineState === "ESTOP_RESET" ? machineState : operationState === "HOME" ? "HOME" : operationState === "RUNNING" ? "RUNNING" : operationState === "PAUSED" ? "PAUSED" : machineState === "OFF" ? "OFF" : "IDLE";
  const sourceTaskState = machineState === "ESTOP" ? "STATE_ESTOP" : machineState === "ESTOP_RESET" ? "STATE_ESTOP_RESET" : machineState === "OFF" ? "STATE_OFF" : "STATE_ON";
  const sourceInterpState = operationState === "PAUSED" ? "INTERP_PAUSED" : operationState === "RUNNING" ? "INTERP_READING" : "INTERP_IDLE";
  const sourceMode = String(task.mode ?? "MANUAL").toUpperCase();
  return Object.freeze({ state, machine_state: machineState, operation_state: operationState, source_task_state: sourceTaskState, source_interp_state: sourceInterpState, source_mode: sourceMode, states: [...AXIS_STATES] });
}

export function validateAxisTransition(previous, next) {
  if (!AXIS_STATES.includes(previous) || !AXIS_STATES.includes(next)) return { status: "blocked", code: "axis_state_unknown" };
  return AXIS_TRANSITIONS[previous]?.includes(next) ? { status: "accepted", previous, next } : { status: "blocked", code: "axis_state_transition_invalid", previous, next };
}