feat(db): add battery REST endpoint

Get latest value of battery for each node

Assisted-by: Junie:claude-sonnet-4.6
Signed-off-by: Klagarge <remi@heredero.ch>

db/get-db.http

@@ -15,3 +15,7 @@ Authorization: Basic {{username}} {{password}}
 ### GET all rooms
 GET {{host}}/api/v1/rooms
 Authorization: Basic {{username}} {{password}}
+
+### GET battery status of all devices
+GET {{host}}/api/v1/battery
+Authorization: Basic {{username}} {{password}}

db/src/docs/docs.go

@@ -15,6 +15,47 @@ const docTemplate = `{
     "host": "{{.Host}}",
     "basePath": "{{.BasePath}}",
     "paths": {
+        "/battery": {
+            "get": {
+                "security": [
+                    {
+                        "BasicAuth": []
+                    }
+                ],
+                "description": "Get the last battery level for each node grouped by room",
+                "produces": [
+                    "application/json"
+                ],
+                "tags": [
+                    "battery"
+                ],
+                "summary": "Get last battery level for each node",
+                "responses": {
+                    "200": {
+                        "description": "OK",
+                        "schema": {
+                            "type": "object",
+                            "additionalProperties": {
+                                "type": "object",
+                                "additionalProperties": {
+                                    "type": "object",
+                                    "additionalProperties": true
+                                }
+                            }
+                        }
+                    },
+                    "500": {
+                        "description": "Internal Server Error",
+                        "schema": {
+                            "type": "object",
+                            "additionalProperties": {
+                                "type": "string"
+                            }
+                        }
+                    }
+                }
+            }
+        },
         "/rooms": {
             "get": {
                 "security": [

db/src/docs/swagger.json

@@ -9,6 +9,47 @@
     "host": "api.db.e.kb28.ch",
     "basePath": "/api/v1",
     "paths": {
+        "/battery": {
+            "get": {
+                "security": [
+                    {
+                        "BasicAuth": []
+                    }
+                ],
+                "description": "Get the last battery level for each node grouped by room",
+                "produces": [
+                    "application/json"
+                ],
+                "tags": [
+                    "battery"
+                ],
+                "summary": "Get last battery level for each node",
+                "responses": {
+                    "200": {
+                        "description": "OK",
+                        "schema": {
+                            "type": "object",
+                            "additionalProperties": {
+                                "type": "object",
+                                "additionalProperties": {
+                                    "type": "object",
+                                    "additionalProperties": true
+                                }
+                            }
+                        }
+                    },
+                    "500": {
+                        "description": "Internal Server Error",
+                        "schema": {
+                            "type": "object",
+                            "additionalProperties": {
+                                "type": "string"
+                            }
+                        }
+                    }
+                }
+            }
+        },
         "/rooms": {
             "get": {
                 "security": [

db/src/docs/swagger.yaml

@@ -6,6 +6,32 @@ info:
   title: Gateway API
   version: "1.0"
 paths:
+  /battery:
+    get:
+      description: Get the last battery level for each node grouped by room
+      produces:
+      - application/json
+      responses:
+        "200":
+          description: OK
+          schema:
+            additionalProperties:
+              additionalProperties:
+                additionalProperties: true
+                type: object
+              type: object
+            type: object
+        "500":
+          description: Internal Server Error
+          schema:
+            additionalProperties:
+              type: string
+            type: object
+      security:
+      - BasicAuth: []
+      summary: Get last battery level for each node
+      tags:
+      - battery
   /rooms:
     get:
       description: Get a list of all unique rooms from the measurement

db/src/mapping.go

@@ -90,6 +90,15 @@ func (c *MappingConfig) NodesForRoom(room string) []string {
 	return nodes
 }
 
+// AllNodes returns all node IDs defined in the mapping.
+func (c *MappingConfig) AllNodes() []string {
+	nodes := make([]string, 0, len(c.nodeToRoom))
+	for nodeID := range c.nodeToRoom {
+		nodes = append(nodes, nodeID)
+	}
+	return nodes
+}
+
 // Rooms returns the list of all room names defined in the mapping.
 func (c *MappingConfig) Rooms() []string {
 	seen := make(map[string]struct{})

db/src/rest/rest.go

@@ -20,6 +20,8 @@ import (
 type RoomMapper interface {
 	Rooms() []string
 	NodesForRoom(room string) []string
+	AllNodes() []string
+	GetRoom(nodeID string) (string, bool)
 }
 
 type RestGateway struct {
@@ -71,6 +73,7 @@ func (g *RestGateway) setupRoutes() {
 		v1.GET("/rooms", g.getRooms)
 		v1.GET("/rooms/:room-id/current", g.getRoomCurrent)
 		v1.GET("/rooms/:room-id/history", g.getRoomHistory)
+		v1.GET("/battery", g.getBattery)
 	}
 
 	g.engine.GET("/swagger/*any", ginSwagger.WrapHandler(swaggerFiles.Handler))
@@ -85,6 +88,77 @@ func buildNodeFilter(nodes []string) string {
 	return "(" + strings.Join(parts, " OR ") + ")"
 }
 
+// GET /api/v1/battery
+// getBattery godoc
+// @Summary Get last battery level for each node
+// @Description Get the last battery level for each node grouped by room
+// @Tags battery
+// @Produce json
+// @Success 200 {object} map[string]map[string]map[string]any
+// @Failure 500 {object} map[string]string
+// @Security BasicAuth
+// @Router /battery [get]
+func (g *RestGateway) getBattery(c *gin.Context) {
+	allNodes := g.mapping.AllNodes()
+	if len(allNodes) == 0 {
+		c.JSON(http.StatusOK, gin.H{})
+		return
+	}
+
+	nodeFilter := buildNodeFilter(allNodes)
+	query := fmt.Sprintf(
+		`SELECT "node", "battery" FROM "%s" WHERE %s AND time > now() - INTERVAL '3 hour' ORDER BY time DESC`,
+		g.measurementName, nodeFilter,
+	)
+
+	it, err := g.influxGateway.Query(context.Background(), query)
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+		return
+	}
+
+	// Collect last battery per node (first occurrence = most recent due to DESC order)
+	nodeBattery := make(map[string]any)
+	for it.Next() {
+		row := it.Value()
+		nodeVal, ok := row["node"]
+		if !ok {
+			continue
+		}
+		nodeID, ok := nodeVal.(string)
+		if !ok {
+			continue
+		}
+		if _, seen := nodeBattery[nodeID]; !seen {
+			nodeBattery[nodeID] = row["battery"]
+		}
+	}
+
+	if err := it.Err(); err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+		return
+	}
+
+	// Group by room
+	result := make(map[string]map[string]map[string]any)
+	for _, nodeID := range allNodes {
+		room, ok := g.mapping.GetRoom(nodeID)
+		if !ok {
+			room = "not-attributed"
+		}
+		if result[room] == nil {
+			result[room] = make(map[string]map[string]any)
+		}
+		battery, hasData := nodeBattery[nodeID]
+		if !hasData {
+			battery = "offline (3h)"
+		}
+		result[room][nodeID] = map[string]any{"battery": battery}
+	}
+
+	c.JSON(http.StatusOK, result)
+}
+
 func (g *RestGateway) Run(addr string) error {
 	return g.engine.Run(addr)
 }