(* === DECLARATION === *)
FUNCTION_BLOCK fb_light
VAR_INPUT
    // Home Assistant Commands
    ha_on: BOOL;      // HA command: Turn ON
    ha_off: BOOL;     // HA command: Turn OFF
    
    // Zigbee Switch Input
    zigbee_sw: BOOL;  // Zigbee switch (edge detected)
    
    // Status Feedback
    relay_status: BOOL;  // Actual relay state (read from EtherCAT)
END_VAR
VAR_OUTPUT
    light_output: BOOL;      // Control output to relay
    light_status: BOOL;      // Status to send back (actual relay state)
END_VAR
VAR
    // Edge triggers
    r_trig_ha_on: R_TRIG;
    r_trig_ha_off: R_TRIG;
    r_trig_zigbee: R_TRIG;
    
    // Internal state
    light_state: BOOL := FALSE;
END_VAR

(* === IMPLEMENTATION === *)
// =====================================================
// fb_light - Implementation (per redesign)
// =====================================================
// Priority (highest to lowest):
// 1. HA OFF command  - Always turns light OFF
// 2. HA ON command   - Always turns light ON
// 3. Zigbee toggle   - Toggles current state
// 4. Maintain current state
// =====================================================

// Edge detection for commands
r_trig_ha_on(CLK := ha_on);
r_trig_ha_off(CLK := ha_off);
r_trig_zigbee(CLK := zigbee_sw);

// State machine
IF r_trig_ha_off.Q THEN
    light_state := FALSE;
ELSIF r_trig_ha_on.Q THEN
    light_state := TRUE;
ELSIF r_trig_zigbee.Q THEN
    light_state := NOT light_state;
END_IF;

// Output assignment
light_output := light_state;

// Status feedback (read from actual relay)
light_status := relay_status;