feat(hass): ✨ add validation of sensor requests

- support requests providing a validation function that is run before request is sent to HA
- add basic validation to sensor registration and update requests

internal/hass/client.go

@@ -45,6 +45,11 @@ var (
 	}
 )
 
+// Validate is a request that supports validation of its values.
+type Validate interface {
+	Validate() error
+}
+
 // GetRequest is a HTTP GET request.
 type GetRequest any
 
@@ -180,7 +185,7 @@ func (c *Client) handleSensorUpdate(ctx context.Context, details sensor.Details)
 
 	response, err := send[sensor.StateUpdateResponse](ctx, c, req)
 	if err != nil {
-		return fmt.Errorf("failed to send sensor update request: %w", err)
+		return fmt.Errorf("failed to send sensor update request for %s: %w", details.ID(), err)
 	}
 
 	if response == nil {
@@ -335,6 +340,13 @@ func send[T any](ctx context.Context, client *Client, requestDetails any) (T, er
 		return response, ErrInvalidClient
 	}
 
+	// If the request supports validation, make sure it is valid.
+	if a, ok := requestDetails.(Validate); ok {
+		if err := a.Validate(); err != nil {
+			return response, fmt.Errorf("validation failed: %w", err)
+		}
+	}
+
 	requestObj := client.endpoint.R().SetContext(ctx)
 	requestObj = requestObj.SetError(&responseErr)
 	requestObj = requestObj.SetResult(&response)

internal/hass/sensor/sensor.go

@@ -54,10 +54,10 @@ type Details interface {
 
 type stateUpdateRequest struct {
 	StateAttributes map[string]any `json:"attributes,omitempty"`
-	State           any            `json:"state"`
-	Icon            string         `json:"icon,omitempty"`
+	State           any            `json:"state" validate:"required"`
+	Icon            string         `json:"icon,omitempty" validate:"startswith=mdi"`
 	Type            string         `json:"type"`
-	UniqueID        string         `json:"unique_id"`
+	UniqueID        string         `json:"unique_id" validate:"required"`
 }
 
 func createStateUpdateRequest(sensor State) *stateUpdateRequest {
@@ -77,8 +77,8 @@ func createStateUpdateRequest(sensor State) *stateUpdateRequest {
 
 type registrationRequest struct {
 	*stateUpdateRequest
-	Name              string `json:"name,omitempty"`
-	UnitOfMeasurement string `json:"unit_of_measurement,omitempty"`
+	Name              string `json:"name" validate:"required"`
+	UnitOfMeasurement string `json:"unit_of_measurement,omitempty" validate:"required_with:DeviceClass"`
 	StateClass        string `json:"state_class,omitempty"`
 	EntityCategory    string `json:"entity_category,omitempty"`
 	DeviceClass       string `json:"device_class,omitempty"`
@@ -119,7 +119,16 @@ type LocationRequest struct {
 
 type Request struct {
 	Data        any    `json:"data"`
-	RequestType string `json:"type"`
+	RequestType string `json:"type" validate:"oneof=register_sensor update_sensor_states update_location"`
+}
+
+func (r *Request) Validate() error {
+	err := validate.Struct(r.Data)
+	if err != nil {
+		return fmt.Errorf("%w: %s", ErrValidationFailed, parseValidationErrors(err))
+	}
+
+	return nil
 }
 
 func (r *Request) RequestBody() json.RawMessage {

internal/hass/sensor/validation.go

@@ -0,0 +1,45 @@
+// Copyright (c) 2024 Joshua Rich <joshua.rich@gmail.com>
+//
+// This software is released under the MIT License.
+// https://opensource.org/licenses/MIT
+
+package sensor
+
+import (
+	"errors"
+	"strings"
+
+	"github.com/go-playground/validator/v10"
+)
+
+var validate *validator.Validate
+
+var ErrValidationFailed = errors.New("validation failed")
+
+func init() {
+	validate = validator.New(validator.WithRequiredStructEnabled())
+}
+
+//nolint:errorlint
+//revive:disable:unhandled-error
+func parseValidationErrors(validation error) string {
+	validationErrs, ok := validation.(validator.ValidationErrors)
+	if !ok {
+		return "internal validation error"
+	}
+
+	var message strings.Builder
+
+	for _, err := range validationErrs {
+		switch err.Tag() {
+		case "required":
+			message.WriteString(err.Field() + " is required")
+		default:
+			message.WriteString(err.Field() + " should match " + err.Tag())
+		}
+
+		message.WriteRune(' ')
+	}
+
+	return message.String()
+}