Add HA connection validation and improved error debugging

- Add test_ha_connection() function to validate API access at startup
- Improve error logging with response body details
- Add debug logs showing exact API endpoints being called
- Capture stderr from curl to catch connection errors

thinkcenter_monitor.sh

@@ -33,6 +33,20 @@ log() {
     echo "[$timestamp] $message" | tee -a "$LOG_FILE"
 }
 
+test_ha_connection() {
+    # Test Home Assistant connectivity at startup
+    log "Testing Home Assistant connection..."
+    local http_code=$(curl -s -o /dev/null -w "%{http_code}" -H "Authorization: Bearer $HA_TOKEN" "$HA_URL/api/" 2>/dev/null)
+    
+    if [[ "$http_code" == "200" ]]; then
+        log "Home Assistant API connection successful"
+        return 0
+    else
+        log "ERROR: Home Assistant API returned HTTP $http_code"
+        return 1
+    fi
+}
+
 check_target() {
     # Use curl to get HTTP response code without following redirects
     local response_code=$(curl -s -o /dev/null -w "%{http_code}" -m 5 "$TARGET_URL" 2>/dev/null)
@@ -65,11 +79,12 @@ trigger_power_cycle() {
      
       # Turn off
       log "Sending turn_off request to Home Assistant ($turn_off_service)..."
+      log "DEBUG: POST to $HA_URL/api/services/$turn_off_service with entity_id=$entity"
       local response=$(curl -s -w "\n%{http_code}" -X POST \
           -H "Authorization: Bearer $HA_TOKEN" \
           -H "Content-Type: application/json" \
           -d "{\"entity_id\": \"$entity\"}" \
-          "$HA_URL/api/services/$turn_off_service")
+          "$HA_URL/api/services/$turn_off_service" 2>&1)
      
      local http_code=$(echo "$response" | tail -n 1)
      local body=$(echo "$response" | head -n -1)
@@ -77,7 +92,8 @@ trigger_power_cycle() {
      if [[ "$http_code" =~ ^[2][0-9]{2}$ ]]; then
          log "Turn off request sent successfully (HTTP $http_code)"
      else
-         log "ERROR: Failed to send turn_off request (HTTP $http_code). Response: $body"
+         log "ERROR: Failed to send turn_off request (HTTP $http_code)"
+         log "ERROR: Response body: $body"
      fi
      
      # Wait 10 seconds
@@ -86,11 +102,12 @@ trigger_power_cycle() {
      
       # Turn on
       log "Sending turn_on request to Home Assistant ($turn_on_service)..."
+      log "DEBUG: POST to $HA_URL/api/services/$turn_on_service with entity_id=$entity"
       local response=$(curl -s -w "\n%{http_code}" -X POST \
           -H "Authorization: Bearer $HA_TOKEN" \
           -H "Content-Type: application/json" \
           -d "{\"entity_id\": \"$entity\"}" \
-          "$HA_URL/api/services/$turn_on_service")
+          "$HA_URL/api/services/$turn_on_service" 2>&1)
      
      local http_code=$(echo "$response" | tail -n 1)
      local body=$(echo "$response" | head -n -1)
@@ -99,7 +116,8 @@ trigger_power_cycle() {
          log "Turn on request sent successfully (HTTP $http_code)"
          log "Power cycle completed for $entity"
      else
-         log "ERROR: Failed to send turn_on request (HTTP $http_code). Response: $body"
+         log "ERROR: Failed to send turn_on request (HTTP $http_code)"
+         log "ERROR: Response body: $body"
      fi
      
      # Reset state
@@ -115,6 +133,12 @@ log "  HA_ENTITY: $HA_ENTITY"
 log "  GRACE_PERIOD: ${GRACE_PERIOD}s ($(( GRACE_PERIOD / 60 )) minutes)"
 log "  CHECK_INTERVAL: ${CHECK_INTERVAL}s"
 
+# Test HA connection before entering main loop
+if ! test_ha_connection; then
+    log "FATAL: Cannot connect to Home Assistant. Exiting."
+    exit 1
+fi
+
 # Main monitoring loop
 while true; do
     RESPONSE_CODE=$(check_target)