feat(alerting): Implement alert-level provider overrides (#929)

* feat(alerting): Implement alert-level provider overrides

Fixes #96

* Fix tests

* Add missing test cases for alerting providers

* feat(alerting): Implement alert-level overrides on all providers

* chore: Add config.yaml to .gitignore

* fix typo in discord provider

* test: Start fixing tests for alerting providers

* test: Fix GitLab tests

* Fix all tests

* test: Improve coverage

* test: Improve coverage

* Rename override to provider-override

* docs: Mention new provider-override config

* test: Improve coverage

* test: Improve coverage

* chore: Rename Alert.OverrideAsBytes to Alert.ProviderOverrideAsBytes

alerting/provider/twilio/twilio.go

@@ -3,6 +3,7 @@ package twilio
 import (
 	"bytes"
 	"encoding/base64"
+	"errors"
 	"fmt"
 	"io"
 	"net/http"
@@ -11,33 +12,80 @@ import (
 	"github.com/TwiN/gatus/v5/alerting/alert"
 	"github.com/TwiN/gatus/v5/client"
 	"github.com/TwiN/gatus/v5/config/endpoint"
+	"gopkg.in/yaml.v3"
 )
 
-// AlertProvider is the configuration necessary for sending an alert using Twilio
-type AlertProvider struct {
+var (
+	ErrSIDNotSet   = errors.New("sid not set")
+	ErrTokenNotSet = errors.New("token not set")
+	ErrFromNotSet  = errors.New("from not set")
+	ErrToNotSet    = errors.New("to not set")
+)
+
+type Config struct {
 	SID   string `yaml:"sid"`
 	Token string `yaml:"token"`
 	From  string `yaml:"from"`
 	To    string `yaml:"to"`
+}
+
+func (cfg *Config) Validate() error {
+	if len(cfg.SID) == 0 {
+		return ErrSIDNotSet
+	}
+	if len(cfg.Token) == 0 {
+		return ErrTokenNotSet
+	}
+	if len(cfg.From) == 0 {
+		return ErrFromNotSet
+	}
+	if len(cfg.To) == 0 {
+		return ErrToNotSet
+	}
+	return nil
+}
+
+func (cfg *Config) Merge(override *Config) {
+	if len(override.SID) > 0 {
+		cfg.SID = override.SID
+	}
+	if len(override.Token) > 0 {
+		cfg.Token = override.Token
+	}
+	if len(override.From) > 0 {
+		cfg.From = override.From
+	}
+	if len(override.To) > 0 {
+		cfg.To = override.To
+	}
+}
+
+// AlertProvider is the configuration necessary for sending an alert using Twilio
+type AlertProvider struct {
+	DefaultConfig Config `yaml:",inline"`
 
 	// DefaultAlert is the default alert configuration to use for endpoints with an alert of the appropriate type
 	DefaultAlert *alert.Alert `yaml:"default-alert,omitempty"`
 }
 
-// IsValid returns whether the provider's configuration is valid
-func (provider *AlertProvider) IsValid() bool {
-	return len(provider.Token) > 0 && len(provider.SID) > 0 && len(provider.From) > 0 && len(provider.To) > 0
+// Validate the provider's configuration
+func (provider *AlertProvider) Validate() error {
+	return provider.DefaultConfig.Validate()
 }
 
 // Send an alert using the provider
 func (provider *AlertProvider) Send(ep *endpoint.Endpoint, alert *alert.Alert, result *endpoint.Result, resolved bool) error {
-	buffer := bytes.NewBuffer([]byte(provider.buildRequestBody(ep, alert, result, resolved)))
-	request, err := http.NewRequest(http.MethodPost, fmt.Sprintf("https://api.twilio.com/2010-04-01/Accounts/%s/Messages.json", provider.SID), buffer)
+	cfg, err := provider.GetConfig(ep.Group, alert)
+	if err != nil {
+		return err
+	}
+	buffer := bytes.NewBuffer([]byte(provider.buildRequestBody(cfg, ep, alert, result, resolved)))
+	request, err := http.NewRequest(http.MethodPost, fmt.Sprintf("https://api.twilio.com/2010-04-01/Accounts/%s/Messages.json", cfg.SID), buffer)
 	if err != nil {
 		return err
 	}
 	request.Header.Set("Content-Type", "application/x-www-form-urlencoded")
-	request.Header.Set("Authorization", fmt.Sprintf("Basic %s", base64.StdEncoding.EncodeToString([]byte(provider.SID+":"+provider.Token))))
+	request.Header.Set("Authorization", fmt.Sprintf("Basic %s", base64.StdEncoding.EncodeToString([]byte(cfg.SID+":"+cfg.Token))))
 	response, err := client.GetHTTPClient(nil).Do(request)
 	if err != nil {
 		return err
@@ -51,7 +99,7 @@ func (provider *AlertProvider) Send(ep *endpoint.Endpoint, alert *alert.Alert, r
 }
 
 // buildRequestBody builds the request body for the provider
-func (provider *AlertProvider) buildRequestBody(ep *endpoint.Endpoint, alert *alert.Alert, result *endpoint.Result, resolved bool) string {
+func (provider *AlertProvider) buildRequestBody(cfg *Config, ep *endpoint.Endpoint, alert *alert.Alert, result *endpoint.Result, resolved bool) string {
 	var message string
 	if resolved {
 		message = fmt.Sprintf("RESOLVED: %s - %s", ep.DisplayName(), alert.GetDescription())
@@ -59,8 +107,8 @@ func (provider *AlertProvider) buildRequestBody(ep *endpoint.Endpoint, alert *al
 		message = fmt.Sprintf("TRIGGERED: %s - %s", ep.DisplayName(), alert.GetDescription())
 	}
 	return url.Values{
-		"To":   {provider.To},
-		"From": {provider.From},
+		"To":   {cfg.To},
+		"From": {cfg.From},
 		"Body": {message},
 	}.Encode()
 }
@@ -69,3 +117,25 @@ func (provider *AlertProvider) buildRequestBody(ep *endpoint.Endpoint, alert *al
 func (provider *AlertProvider) GetDefaultAlert() *alert.Alert {
 	return provider.DefaultAlert
 }
+
+// GetConfig returns the configuration for the provider with the overrides applied
+func (provider *AlertProvider) GetConfig(group string, alert *alert.Alert) (*Config, error) {
+	cfg := provider.DefaultConfig
+	// Handle alert overrides
+	if len(alert.ProviderOverride) != 0 {
+		overrideConfig := Config{}
+		if err := yaml.Unmarshal(alert.ProviderOverrideAsBytes(), &overrideConfig); err != nil {
+			return nil, err
+		}
+		cfg.Merge(&overrideConfig)
+	}
+	// Validate the configuration
+	err := cfg.Validate()
+	return &cfg, err
+}
+
+// ValidateOverrides validates the alert's provider override and, if present, the group override
+func (provider *AlertProvider) ValidateOverrides(group string, alert *alert.Alert) error {
+	_, err := provider.GetConfig(group, alert)
+	return err
+}