add metric endpoint to public API (#72, #80)

internal/adapters/database.go

@@ -295,6 +295,30 @@ func (r *SqlRepo) GetAllInterfaces(ctx context.Context) ([]domain.Interface, err
 	return interfaces, nil
 }
 
+func (r *SqlRepo) GetInterfaceStats(ctx context.Context, id domain.InterfaceIdentifier) (
+	*domain.InterfaceStatus,
+	error,
+) {
+	if id == "" {
+		return nil, nil
+	}
+
+	var stats []domain.InterfaceStatus
+
+	err := r.db.WithContext(ctx).Where("identifier = ?", id).Find(&stats).Error
+	if err != nil {
+		return nil, err
+	}
+
+	if len(stats) == 0 {
+		return nil, domain.ErrNotFound
+	}
+
+	stat := stats[0]
+
+	return &stat, nil
+}
+
 func (r *SqlRepo) FindInterfaces(ctx context.Context, search string) ([]domain.Interface, error) {
 	var users []domain.Interface
 

internal/app/api/core/assets/doc/v1_swagger.json

@@ -309,6 +309,180 @@
                 }
             }
         },
+        "/metrics/by-interface/{id}": {
+            "get": {
+                "security": [
+                    {
+                        "BasicAuth": []
+                    }
+                ],
+                "produces": [
+                    "application/json"
+                ],
+                "tags": [
+                    "Metrics"
+                ],
+                "summary": "Get all metrics for a WireGuard Portal interface.",
+                "operationId": "metrics_handleMetricsForInterfaceGet",
+                "parameters": [
+                    {
+                        "type": "string",
+                        "description": "The WireGuard interface identifier.",
+                        "name": "id",
+                        "in": "path",
+                        "required": true
+                    }
+                ],
+                "responses": {
+                    "200": {
+                        "description": "OK",
+                        "schema": {
+                            "$ref": "#/definitions/models.InterfaceMetrics"
+                        }
+                    },
+                    "400": {
+                        "description": "Bad Request",
+                        "schema": {
+                            "$ref": "#/definitions/models.Error"
+                        }
+                    },
+                    "401": {
+                        "description": "Unauthorized",
+                        "schema": {
+                            "$ref": "#/definitions/models.Error"
+                        }
+                    },
+                    "404": {
+                        "description": "Not Found",
+                        "schema": {
+                            "$ref": "#/definitions/models.Error"
+                        }
+                    },
+                    "500": {
+                        "description": "Internal Server Error",
+                        "schema": {
+                            "$ref": "#/definitions/models.Error"
+                        }
+                    }
+                }
+            }
+        },
+        "/metrics/by-peer/{id}": {
+            "get": {
+                "security": [
+                    {
+                        "BasicAuth": []
+                    }
+                ],
+                "produces": [
+                    "application/json"
+                ],
+                "tags": [
+                    "Metrics"
+                ],
+                "summary": "Get all metrics for a WireGuard Portal peer.",
+                "operationId": "metrics_handleMetricsForPeerGet",
+                "parameters": [
+                    {
+                        "type": "string",
+                        "description": "The peer identifier (public key).",
+                        "name": "id",
+                        "in": "path",
+                        "required": true
+                    }
+                ],
+                "responses": {
+                    "200": {
+                        "description": "OK",
+                        "schema": {
+                            "$ref": "#/definitions/models.PeerMetrics"
+                        }
+                    },
+                    "400": {
+                        "description": "Bad Request",
+                        "schema": {
+                            "$ref": "#/definitions/models.Error"
+                        }
+                    },
+                    "401": {
+                        "description": "Unauthorized",
+                        "schema": {
+                            "$ref": "#/definitions/models.Error"
+                        }
+                    },
+                    "404": {
+                        "description": "Not Found",
+                        "schema": {
+                            "$ref": "#/definitions/models.Error"
+                        }
+                    },
+                    "500": {
+                        "description": "Internal Server Error",
+                        "schema": {
+                            "$ref": "#/definitions/models.Error"
+                        }
+                    }
+                }
+            }
+        },
+        "/metrics/by-user/{id}": {
+            "get": {
+                "security": [
+                    {
+                        "BasicAuth": []
+                    }
+                ],
+                "produces": [
+                    "application/json"
+                ],
+                "tags": [
+                    "Metrics"
+                ],
+                "summary": "Get all metrics for a WireGuard Portal user.",
+                "operationId": "metrics_handleMetricsForUserGet",
+                "parameters": [
+                    {
+                        "type": "string",
+                        "description": "The user identifier.",
+                        "name": "id",
+                        "in": "path",
+                        "required": true
+                    }
+                ],
+                "responses": {
+                    "200": {
+                        "description": "OK",
+                        "schema": {
+                            "$ref": "#/definitions/models.UserMetrics"
+                        }
+                    },
+                    "400": {
+                        "description": "Bad Request",
+                        "schema": {
+                            "$ref": "#/definitions/models.Error"
+                        }
+                    },
+                    "401": {
+                        "description": "Unauthorized",
+                        "schema": {
+                            "$ref": "#/definitions/models.Error"
+                        }
+                    },
+                    "404": {
+                        "description": "Not Found",
+                        "schema": {
+                            "$ref": "#/definitions/models.Error"
+                        }
+                    },
+                    "500": {
+                        "description": "Internal Server Error",
+                        "schema": {
+                            "$ref": "#/definitions/models.Error"
+                        }
+                    }
+                }
+            }
+        },
         "/peer/by-id/{id}": {
             "get": {
                 "security": [
@@ -1523,6 +1697,26 @@
                 }
             }
         },
+        "models.InterfaceMetrics": {
+            "type": "object",
+            "properties": {
+                "BytesReceived": {
+                    "description": "The number of bytes received by the interface.",
+                    "type": "integer",
+                    "example": 123456789
+                },
+                "BytesTransmitted": {
+                    "description": "The number of bytes transmitted by the interface.",
+                    "type": "integer",
+                    "example": 123456789
+                },
+                "InterfaceIdentifier": {
+                    "description": "The unique identifier of the interface.",
+                    "type": "string",
+                    "example": "wg0"
+                }
+            }
+        },
         "models.Peer": {
             "type": "object",
             "required": [
@@ -1728,6 +1922,51 @@
                 }
             }
         },
+        "models.PeerMetrics": {
+            "type": "object",
+            "properties": {
+                "BytesReceived": {
+                    "description": "The number of bytes received by the peer.",
+                    "type": "integer",
+                    "example": 123456789
+                },
+                "BytesTransmitted": {
+                    "description": "The number of bytes transmitted by the peer.",
+                    "type": "integer",
+                    "example": 123456789
+                },
+                "Endpoint": {
+                    "description": "The current endpoint address of the peer.",
+                    "type": "string",
+                    "example": "12.34.56.78"
+                },
+                "IsPingable": {
+                    "description": "If this field is set, the peer is pingable.",
+                    "type": "boolean",
+                    "example": true
+                },
+                "LastHandshake": {
+                    "description": "The last time the peer initiated a handshake.",
+                    "type": "string",
+                    "example": "2021-01-01T12:00:00Z"
+                },
+                "LastPing": {
+                    "description": "The last time the peer responded to a ICMP ping request.",
+                    "type": "string",
+                    "example": "2021-01-01T12:00:00Z"
+                },
+                "LastSessionStart": {
+                    "description": "The last time the peer initiated a session.",
+                    "type": "string",
+                    "example": "2021-01-01T12:00:00Z"
+                },
+                "PeerIdentifier": {
+                    "description": "The unique identifier of the peer.",
+                    "type": "string",
+                    "example": "xTIBA5rboUvnH4htodjb6e697QjLERt1NAB4mZqp8Dg="
+                }
+            }
+        },
         "models.ProvisioningRequest": {
             "type": "object",
             "required": [
@@ -1922,6 +2161,38 @@
                     "example": true
                 }
             }
+        },
+        "models.UserMetrics": {
+            "type": "object",
+            "properties": {
+                "BytesReceived": {
+                    "description": "The total number of bytes received by the user. This is the sum of all bytes received by the peers linked to the user.",
+                    "type": "integer",
+                    "example": 123456789
+                },
+                "BytesTransmitted": {
+                    "description": "The total number of bytes transmitted by the user. This is the sum of all bytes transmitted by the peers linked to the user.",
+                    "type": "integer",
+                    "example": 123456789
+                },
+                "PeerCount": {
+                    "description": "PeerCount represents the number of peers linked to the user.",
+                    "type": "integer",
+                    "example": 2
+                },
+                "PeerMetrics": {
+                    "description": "PeerMetrics represents the metrics of the peers linked to the user.",
+                    "type": "array",
+                    "items": {
+                        "$ref": "#/definitions/models.PeerMetrics"
+                    }
+                },
+                "UserIdentifier": {
+                    "description": "The unique identifier of the user.",
+                    "type": "string",
+                    "example": "uid-1234567"
+                }
+            }
         }
     },
     "securityDefinitions": {

internal/app/api/core/assets/doc/v1_swagger.yaml

@@ -239,6 +239,21 @@ definitions:
     - PrivateKey
     - PublicKey
     type: object
+  models.InterfaceMetrics:
+    properties:
+      BytesReceived:
+        description: The number of bytes received by the interface.
+        example: 123456789
+        type: integer
+      BytesTransmitted:
+        description: The number of bytes transmitted by the interface.
+        example: 123456789
+        type: integer
+      InterfaceIdentifier:
+        description: The unique identifier of the interface.
+        example: wg0
+        type: string
+    type: object
   models.Peer:
     properties:
       Addresses:
@@ -383,6 +398,41 @@ definitions:
     - InterfaceIdentifier
     - PrivateKey
     type: object
+  models.PeerMetrics:
+    properties:
+      BytesReceived:
+        description: The number of bytes received by the peer.
+        example: 123456789
+        type: integer
+      BytesTransmitted:
+        description: The number of bytes transmitted by the peer.
+        example: 123456789
+        type: integer
+      Endpoint:
+        description: The current endpoint address of the peer.
+        example: 12.34.56.78
+        type: string
+      IsPingable:
+        description: If this field is set, the peer is pingable.
+        example: true
+        type: boolean
+      LastHandshake:
+        description: The last time the peer initiated a handshake.
+        example: "2021-01-01T12:00:00Z"
+        type: string
+      LastPing:
+        description: The last time the peer responded to a ICMP ping request.
+        example: "2021-01-01T12:00:00Z"
+        type: string
+      LastSessionStart:
+        description: The last time the peer initiated a session.
+        example: "2021-01-01T12:00:00Z"
+        type: string
+      PeerIdentifier:
+        description: The unique identifier of the peer.
+        example: xTIBA5rboUvnH4htodjb6e697QjLERt1NAB4mZqp8Dg=
+        type: string
+    type: object
   models.ProvisioningRequest:
     properties:
       InterfaceIdentifier:
@@ -547,6 +597,33 @@ definitions:
         example: true
         type: boolean
     type: object
+  models.UserMetrics:
+    properties:
+      BytesReceived:
+        description: The total number of bytes received by the user. This is the sum
+          of all bytes received by the peers linked to the user.
+        example: 123456789
+        type: integer
+      BytesTransmitted:
+        description: The total number of bytes transmitted by the user. This is the
+          sum of all bytes transmitted by the peers linked to the user.
+        example: 123456789
+        type: integer
+      PeerCount:
+        description: PeerCount represents the number of peers linked to the user.
+        example: 2
+        type: integer
+      PeerMetrics:
+        description: PeerMetrics represents the metrics of the peers linked to the
+          user.
+        items:
+          $ref: '#/definitions/models.PeerMetrics'
+        type: array
+      UserIdentifier:
+        description: The unique identifier of the user.
+        example: uid-1234567
+        type: string
+    type: object
 info:
   contact:
     name: WireGuard Portal Project
@@ -749,6 +826,117 @@ paths:
       summary: Create a new interface record.
       tags:
       - Interfaces
+  /metrics/by-interface/{id}:
+    get:
+      operationId: metrics_handleMetricsForInterfaceGet
+      parameters:
+      - description: The WireGuard interface identifier.
+        in: path
+        name: id
+        required: true
+        type: string
+      produces:
+      - application/json
+      responses:
+        "200":
+          description: OK
+          schema:
+            $ref: '#/definitions/models.InterfaceMetrics'
+        "400":
+          description: Bad Request
+          schema:
+            $ref: '#/definitions/models.Error'
+        "401":
+          description: Unauthorized
+          schema:
+            $ref: '#/definitions/models.Error'
+        "404":
+          description: Not Found
+          schema:
+            $ref: '#/definitions/models.Error'
+        "500":
+          description: Internal Server Error
+          schema:
+            $ref: '#/definitions/models.Error'
+      security:
+      - BasicAuth: []
+      summary: Get all metrics for a WireGuard Portal interface.
+      tags:
+      - Metrics
+  /metrics/by-peer/{id}:
+    get:
+      operationId: metrics_handleMetricsForPeerGet
+      parameters:
+      - description: The peer identifier (public key).
+        in: path
+        name: id
+        required: true
+        type: string
+      produces:
+      - application/json
+      responses:
+        "200":
+          description: OK
+          schema:
+            $ref: '#/definitions/models.PeerMetrics'
+        "400":
+          description: Bad Request
+          schema:
+            $ref: '#/definitions/models.Error'
+        "401":
+          description: Unauthorized
+          schema:
+            $ref: '#/definitions/models.Error'
+        "404":
+          description: Not Found
+          schema:
+            $ref: '#/definitions/models.Error'
+        "500":
+          description: Internal Server Error
+          schema:
+            $ref: '#/definitions/models.Error'
+      security:
+      - BasicAuth: []
+      summary: Get all metrics for a WireGuard Portal peer.
+      tags:
+      - Metrics
+  /metrics/by-user/{id}:
+    get:
+      operationId: metrics_handleMetricsForUserGet
+      parameters:
+      - description: The user identifier.
+        in: path
+        name: id
+        required: true
+        type: string
+      produces:
+      - application/json
+      responses:
+        "200":
+          description: OK
+          schema:
+            $ref: '#/definitions/models.UserMetrics'
+        "400":
+          description: Bad Request
+          schema:
+            $ref: '#/definitions/models.Error'
+        "401":
+          description: Unauthorized
+          schema:
+            $ref: '#/definitions/models.Error'
+        "404":
+          description: Not Found
+          schema:
+            $ref: '#/definitions/models.Error'
+        "500":
+          description: Internal Server Error
+          schema:
+            $ref: '#/definitions/models.Error'
+      security:
+      - BasicAuth: []
+      summary: Get all metrics for a WireGuard Portal user.
+      tags:
+      - Metrics
   /peer/by-id/{id}:
     delete:
       operationId: peers_handleDelete

internal/app/api/v1/backend/metrics_service.go

@@ -0,0 +1,131 @@
+package backend
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/h44z/wg-portal/internal/config"
+	"github.com/h44z/wg-portal/internal/domain"
+)
+
+type MetricsServiceDatabaseRepo interface {
+	GetPeersStats(ctx context.Context, ids ...domain.PeerIdentifier) ([]domain.PeerStatus, error)
+	GetInterfaceStats(ctx context.Context, id domain.InterfaceIdentifier) (
+		*domain.InterfaceStatus,
+		error,
+	)
+	GetUserPeers(ctx context.Context, id domain.UserIdentifier) ([]domain.Peer, error)
+}
+
+type MetricsServiceUserManagerRepo interface {
+	GetUser(ctx context.Context, id domain.UserIdentifier) (*domain.User, error)
+}
+
+type MetricsServicePeerManagerRepo interface {
+	GetPeer(ctx context.Context, id domain.PeerIdentifier) (*domain.Peer, error)
+}
+
+type MetricsService struct {
+	cfg *config.Config
+
+	db    MetricsServiceDatabaseRepo
+	users MetricsServiceUserManagerRepo
+	peers MetricsServicePeerManagerRepo
+}
+
+func NewMetricsService(
+	cfg *config.Config,
+	db MetricsServiceDatabaseRepo,
+	users MetricsServiceUserManagerRepo,
+	peers MetricsServicePeerManagerRepo,
+) *MetricsService {
+	return &MetricsService{
+		cfg:   cfg,
+		db:    db,
+		users: users,
+		peers: peers,
+	}
+}
+
+func (m MetricsService) GetForInterface(ctx context.Context, id domain.InterfaceIdentifier) (
+	*domain.InterfaceStatus,
+	error,
+) {
+	if !m.cfg.Statistics.CollectInterfaceData {
+		return nil, fmt.Errorf("interface statistics collection is disabled")
+	}
+
+	// validate admin rights
+	if err := domain.ValidateAdminAccessRights(ctx); err != nil {
+		return nil, err
+	}
+
+	interfaceStats, err := m.db.GetInterfaceStats(ctx, id)
+	if err != nil {
+		return nil, fmt.Errorf("failed to fetch stats for interface %s: %w", id, err)
+	}
+
+	return interfaceStats, nil
+}
+
+func (m MetricsService) GetForUser(ctx context.Context, id domain.UserIdentifier) (
+	*domain.User,
+	[]domain.PeerStatus,
+	error,
+) {
+	if !m.cfg.Statistics.CollectPeerData {
+		return nil, nil, fmt.Errorf("statistics collection is disabled")
+	}
+
+	if err := domain.ValidateUserAccessRights(ctx, id); err != nil {
+		return nil, nil, err
+	}
+
+	user, err := m.users.GetUser(ctx, id)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	peers, err := m.db.GetUserPeers(ctx, user.Identifier)
+	if err != nil {
+		return nil, nil, fmt.Errorf("failed to fetch peers for user %s: %w", user.Identifier, err)
+	}
+
+	peerIds := make([]domain.PeerIdentifier, len(peers))
+	for i, peer := range peers {
+		peerIds[i] = peer.Identifier
+	}
+
+	peerStats, err := m.db.GetPeersStats(ctx, peerIds...)
+	if err != nil {
+		return nil, nil, fmt.Errorf("failed to fetch peer stats for user %s: %w", user.Identifier, err)
+	}
+
+	return user, peerStats, nil
+}
+
+func (m MetricsService) GetForPeer(ctx context.Context, id domain.PeerIdentifier) (*domain.PeerStatus, error) {
+	if !m.cfg.Statistics.CollectPeerData {
+		return nil, fmt.Errorf("peer statistics collection is disabled")
+	}
+
+	peer, err := m.peers.GetPeer(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+
+	if err := domain.ValidateUserAccessRights(ctx, peer.UserIdentifier); err != nil {
+		return nil, err
+	}
+
+	peerStats, err := m.db.GetPeersStats(ctx, peer.Identifier)
+	if err != nil {
+		return nil, fmt.Errorf("failed to fetch stats for peer %s: %w", peer.Identifier, err)
+	}
+
+	if len(peerStats) == 0 {
+		return nil, fmt.Errorf("no stats found for peer %s: %w", peer.Identifier, domain.ErrNotFound)
+	}
+
+	return &peerStats[0], nil
+}

internal/app/api/v1/handlers/endpoint_metrics.go

@@ -0,0 +1,140 @@
+package handlers
+
+import (
+	"context"
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+	"github.com/h44z/wg-portal/internal/app/api/v1/models"
+	"github.com/h44z/wg-portal/internal/domain"
+)
+
+type MetricsEndpointStatisticsService interface {
+	GetForInterface(ctx context.Context, id domain.InterfaceIdentifier) (*domain.InterfaceStatus, error)
+	GetForUser(ctx context.Context, id domain.UserIdentifier) (*domain.User, []domain.PeerStatus, error)
+	GetForPeer(ctx context.Context, id domain.PeerIdentifier) (*domain.PeerStatus, error)
+}
+
+type MetricsEndpoint struct {
+	metrics MetricsEndpointStatisticsService
+}
+
+func NewMetricsEndpoint(metrics MetricsEndpointStatisticsService) *MetricsEndpoint {
+	return &MetricsEndpoint{
+		metrics: metrics,
+	}
+}
+
+func (e MetricsEndpoint) GetName() string {
+	return "MetricsEndpoint"
+}
+
+func (e MetricsEndpoint) RegisterRoutes(g *gin.RouterGroup, authenticator *authenticationHandler) {
+	apiGroup := g.Group("/metrics", authenticator.LoggedIn())
+
+	apiGroup.GET("/by-interface/:id", authenticator.LoggedIn(ScopeAdmin), e.handleMetricsForInterfaceGet())
+	apiGroup.GET("/by-user/:id", authenticator.LoggedIn(), e.handleMetricsForUserGet())
+	apiGroup.GET("/by-peer/:id", authenticator.LoggedIn(), e.handleMetricsForPeerGet())
+}
+
+// handleMetricsForInterfaceGet returns a gorm Handler function.
+//
+// @ID metrics_handleMetricsForInterfaceGet
+// @Tags Metrics
+// @Summary Get all metrics for a WireGuard Portal interface.
+// @Param id path string true "The WireGuard interface identifier."
+// @Produce json
+// @Success 200 {object} models.InterfaceMetrics
+// @Failure 400 {object} models.Error
+// @Failure 401 {object} models.Error
+// @Failure 404 {object} models.Error
+// @Failure 500 {object} models.Error
+// @Router /metrics/by-interface/{id} [get]
+// @Security BasicAuth
+func (e MetricsEndpoint) handleMetricsForInterfaceGet() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		ctx := domain.SetUserInfoFromGin(c)
+
+		id := c.Param("id")
+		if id == "" {
+			c.JSON(http.StatusBadRequest, models.Error{Code: http.StatusBadRequest, Message: "missing interface id"})
+			return
+		}
+
+		interfaceMetrics, err := e.metrics.GetForInterface(ctx, domain.InterfaceIdentifier(id))
+		if err != nil {
+			c.JSON(ParseServiceError(err))
+			return
+		}
+
+		c.JSON(http.StatusOK, models.NewInterfaceMetrics(interfaceMetrics))
+	}
+}
+
+// handleMetricsForUserGet returns a gorm Handler function.
+//
+// @ID metrics_handleMetricsForUserGet
+// @Tags Metrics
+// @Summary Get all metrics for a WireGuard Portal user.
+// @Param id path string true "The user identifier."
+// @Produce json
+// @Success 200 {object} models.UserMetrics
+// @Failure 400 {object} models.Error
+// @Failure 401 {object} models.Error
+// @Failure 404 {object} models.Error
+// @Failure 500 {object} models.Error
+// @Router /metrics/by-user/{id} [get]
+// @Security BasicAuth
+func (e MetricsEndpoint) handleMetricsForUserGet() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		ctx := domain.SetUserInfoFromGin(c)
+
+		id := c.Param("id")
+		if id == "" {
+			c.JSON(http.StatusBadRequest, models.Error{Code: http.StatusBadRequest, Message: "missing interface id"})
+			return
+		}
+
+		user, userMetrics, err := e.metrics.GetForUser(ctx, domain.UserIdentifier(id))
+		if err != nil {
+			c.JSON(ParseServiceError(err))
+			return
+		}
+
+		c.JSON(http.StatusOK, models.NewUserMetrics(user, userMetrics))
+	}
+}
+
+// handleMetricsForPeerGet returns a gorm Handler function.
+//
+// @ID metrics_handleMetricsForPeerGet
+// @Tags Metrics
+// @Summary Get all metrics for a WireGuard Portal peer.
+// @Param id path string true "The peer identifier (public key)."
+// @Produce json
+// @Success 200 {object} models.PeerMetrics
+// @Failure 400 {object} models.Error
+// @Failure 401 {object} models.Error
+// @Failure 404 {object} models.Error
+// @Failure 500 {object} models.Error
+// @Router /metrics/by-peer/{id} [get]
+// @Security BasicAuth
+func (e MetricsEndpoint) handleMetricsForPeerGet() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		ctx := domain.SetUserInfoFromGin(c)
+
+		id := c.Param("id")
+		if id == "" {
+			c.JSON(http.StatusBadRequest, models.Error{Code: http.StatusBadRequest, Message: "missing peer id"})
+			return
+		}
+
+		peerMetrics, err := e.metrics.GetForPeer(ctx, domain.PeerIdentifier(id))
+		if err != nil {
+			c.JSON(ParseServiceError(err))
+			return
+		}
+
+		c.JSON(http.StatusOK, models.NewPeerMetrics(peerMetrics))
+	}
+}

internal/app/api/v1/models/models_metrics.go

@@ -0,0 +1,105 @@
+package models
+
+import (
+	"time"
+
+	"github.com/h44z/wg-portal/internal/domain"
+)
+
+// PeerMetrics represents the metrics of a WireGuard peer.
+type PeerMetrics struct {
+	// The unique identifier of the peer.
+	PeerIdentifier string `json:"PeerIdentifier" example:"xTIBA5rboUvnH4htodjb6e697QjLERt1NAB4mZqp8Dg="`
+
+	// If this field is set, the peer is pingable.
+	IsPingable bool `json:"IsPingable" example:"true"`
+	// The last time the peer responded to a ICMP ping request.
+	LastPing *time.Time `json:"LastPing" example:"2021-01-01T12:00:00Z"`
+
+	// The number of bytes received by the peer.
+	BytesReceived uint64 `json:"BytesReceived" example:"123456789"`
+	// The number of bytes transmitted by the peer.
+	BytesTransmitted uint64 `json:"BytesTransmitted" example:"123456789"`
+
+	// The last time the peer initiated a handshake.
+	LastHandshake *time.Time `json:"LastHandshake" example:"2021-01-01T12:00:00Z"`
+	// The current endpoint address of the peer.
+	Endpoint string `json:"Endpoint" example:"12.34.56.78"`
+	// The last time the peer initiated a session.
+	LastSessionStart *time.Time `json:"LastSessionStart" example:"2021-01-01T12:00:00Z"`
+}
+
+func NewPeerMetrics(src *domain.PeerStatus) *PeerMetrics {
+	return &PeerMetrics{
+		PeerIdentifier:   string(src.PeerId),
+		IsPingable:       src.IsPingable,
+		LastPing:         src.LastPing,
+		BytesReceived:    src.BytesReceived,
+		BytesTransmitted: src.BytesTransmitted,
+		LastHandshake:    src.LastHandshake,
+		Endpoint:         src.Endpoint,
+		LastSessionStart: src.LastSessionStart,
+	}
+}
+
+// InterfaceMetrics represents the metrics of a WireGuard interface.
+type InterfaceMetrics struct {
+	// The unique identifier of the interface.
+	InterfaceIdentifier string `json:"InterfaceIdentifier" example:"wg0"`
+
+	// The number of bytes received by the interface.
+	BytesReceived uint64 `json:"BytesReceived" example:"123456789"`
+	// The number of bytes transmitted by the interface.
+	BytesTransmitted uint64 `json:"BytesTransmitted" example:"123456789"`
+}
+
+func NewInterfaceMetrics(src *domain.InterfaceStatus) *InterfaceMetrics {
+	return &InterfaceMetrics{
+		InterfaceIdentifier: string(src.InterfaceId),
+		BytesReceived:       src.BytesReceived,
+		BytesTransmitted:    src.BytesTransmitted,
+	}
+}
+
+// UserMetrics represents the metrics of a WireGuard user.
+type UserMetrics struct {
+	// The unique identifier of the user.
+	UserIdentifier string `json:"UserIdentifier" example:"uid-1234567"`
+
+	// PeerCount represents the number of peers linked to the user.
+	PeerCount int `json:"PeerCount" example:"2"`
+
+	// The total number of bytes received by the user. This is the sum of all bytes received by the peers linked to the user.
+	BytesReceived uint64 `json:"BytesReceived" example:"123456789"`
+	// The total number of bytes transmitted by the user. This is the sum of all bytes transmitted by the peers linked to the user.
+	BytesTransmitted uint64 `json:"BytesTransmitted" example:"123456789"`
+
+	// PeerMetrics represents the metrics of the peers linked to the user.
+	PeerMetrics []PeerMetrics `json:"PeerMetrics"`
+}
+
+func NewUserMetrics(srcUser *domain.User, src []domain.PeerStatus) *UserMetrics {
+	if srcUser == nil {
+		return nil
+	}
+
+	um := &UserMetrics{
+		UserIdentifier: string(srcUser.Identifier),
+		PeerCount:      srcUser.LinkedPeerCount,
+		PeerMetrics:    []PeerMetrics{},
+
+		BytesReceived:    0,
+		BytesTransmitted: 0,
+	}
+
+	peerMetrics := make([]PeerMetrics, len(src))
+	for i, peer := range src {
+		peerMetrics[i] = *NewPeerMetrics(&peer)
+
+		um.BytesReceived += peer.BytesReceived
+		um.BytesTransmitted += peer.BytesTransmitted
+	}
+	um.PeerMetrics = peerMetrics
+
+	return um
+}