feat(alerting): Add Google Chat alerting provider (#234)

alerting/provider/googlechat/googlechat.go

@@ -0,0 +1,124 @@
+package googlechat
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"net/http"
+
+	"github.com/TwiN/gatus/v3/alerting/alert"
+	"github.com/TwiN/gatus/v3/client"
+	"github.com/TwiN/gatus/v3/core"
+)
+
+// AlertProvider is the configuration necessary for sending an alert using Google chat
+type AlertProvider struct {
+	WebhookURL string `yaml:"webhook-url"`
+
+	// ClientConfig is the configuration of the client used to communicate with the provider's target
+	ClientConfig *client.Config `yaml:"client,omitempty"`
+
+	// 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 {
+	if provider.ClientConfig == nil {
+		provider.ClientConfig = client.GetDefaultConfig()
+	}
+	return len(provider.WebhookURL) > 0
+}
+
+// Send an alert using the provider
+func (provider *AlertProvider) Send(endpoint *core.Endpoint, alert *alert.Alert, result *core.Result, resolved bool) error {
+	buffer := bytes.NewBuffer([]byte(provider.buildRequestBody(endpoint, alert, result, resolved)))
+	request, err := http.NewRequest(http.MethodPost, provider.WebhookURL, buffer)
+	if err != nil {
+		return err
+	}
+	request.Header.Set("Content-Type", "application/json")
+	response, err := client.GetHTTPClient(provider.ClientConfig).Do(request)
+	if err != nil {
+		return err
+	}
+	if response.StatusCode > 399 {
+		body, _ := io.ReadAll(response.Body)
+		return fmt.Errorf("call to provider alert returned status code %d: %s", response.StatusCode, string(body))
+	}
+	return err
+}
+
+// buildRequestBody builds the request body for the provider
+func (provider *AlertProvider) buildRequestBody(endpoint *core.Endpoint, alert *alert.Alert, result *core.Result, resolved bool) string {
+	var message, color string
+	if resolved {
+		color = "#36A64F"
+		message = fmt.Sprintf("<font color='%s'>An alert has been resolved after passing successfully %d time(s) in a row</font>", color, alert.SuccessThreshold)
+	} else {
+		color = "#DD0000"
+		message = fmt.Sprintf("<font color='%s'>An alert has been triggered due to having failed %d time(s) in a row</font>", color, alert.FailureThreshold)
+	}
+	var results string
+	for _, conditionResult := range result.ConditionResults {
+		var prefix string
+		if conditionResult.Success {
+			prefix = "✅"
+		} else {
+			prefix = "❌"
+		}
+		results += fmt.Sprintf("%s   %s<br>", prefix, conditionResult.Condition)
+	}
+	var description string
+	if alertDescription := alert.GetDescription(); len(alertDescription) > 0 {
+		description = ":: " + alertDescription
+	}
+	return fmt.Sprintf(`{
+    "cards": [
+  {
+    "sections": [
+      {
+        "widgets": [
+          {
+            "keyValue": {
+              "topLabel": "%s [%s]",
+              "content": "%s",
+              "contentMultiline": "true",
+              "bottomLabel": "%s",
+              "icon": "BOOKMARK"
+            }
+          },
+          {
+            "keyValue": {
+              "topLabel": "Condition results",
+              "content": "%s",
+              "contentMultiline": "true",
+              "icon": "DESCRIPTION"
+            }
+          },
+          {
+            "buttons": [
+              {
+                "textButton": {
+                  "text": "URL",
+                  "onClick": {
+                    "openLink": {
+                      "url": "%s"
+                    }
+                  }
+                }
+              }
+            ]
+          }
+        ]
+      }
+    ]
+  }
+]
+}`, endpoint.Name, endpoint.Group, message, description, results, endpoint.URL)
+}
+
+// GetDefaultAlert returns the provider's default alert configuration
+func (provider AlertProvider) GetDefaultAlert() *alert.Alert {
+	return provider.DefaultAlert
+}