refactor: Break core package into multiple packages under config/endpoint (#759)

* refactor: Partially break core package into dns, result and ssh packages

* refactor: Move core package to config/endpoint

* refactor: Fix warning about overlapping imported package name with endpoint variable

* refactor: Rename EndpointStatus to Status

* refactor: Merge result pkg back into endpoint pkg, because it makes more sense

* refactor: Rename parameter r to result in Condition.evaluate

* refactor: Rename parameter r to result

* refactor: Revert accidental change to endpoint.TypeDNS

* refactor: Rename parameter r to result

* refactor: Merge util package into endpoint package

* refactor: Rename parameter r to result

config/endpoint/dns/dns.go

@@ -0,0 +1,38 @@
+package dns
+
+import (
+	"errors"
+	"strings"
+
+	"github.com/miekg/dns"
+)
+
+var (
+	// ErrDNSWithNoQueryName is the error with which gatus will panic if a dns is configured without query name
+	ErrDNSWithNoQueryName = errors.New("you must specify a query name in the DNS configuration")
+
+	// ErrDNSWithInvalidQueryType is the error with which gatus will panic if a dns is configured with invalid query type
+	ErrDNSWithInvalidQueryType = errors.New("invalid query type in the DNS configuration")
+)
+
+// Config for an Endpoint of type DNS
+type Config struct {
+	// QueryType is the type for the DNS records like A, AAAA, CNAME...
+	QueryType string `yaml:"query-type"`
+
+	// QueryName is the query for DNS
+	QueryName string `yaml:"query-name"`
+}
+
+func (d *Config) ValidateAndSetDefault() error {
+	if len(d.QueryName) == 0 {
+		return ErrDNSWithNoQueryName
+	}
+	if !strings.HasSuffix(d.QueryName, ".") {
+		d.QueryName += "."
+	}
+	if _, ok := dns.StringToType[d.QueryType]; !ok {
+		return ErrDNSWithInvalidQueryType
+	}
+	return nil
+}

config/endpoint/dns/dns_test.go

@@ -0,0 +1,27 @@
+package dns
+
+import (
+	"testing"
+)
+
+func TestConfig_ValidateAndSetDefault(t *testing.T) {
+	dns := &Config{
+		QueryType: "A",
+		QueryName: "",
+	}
+	err := dns.ValidateAndSetDefault()
+	if err == nil {
+		t.Error("Should've returned an error because endpoint's dns didn't have a query name, which is a mandatory field for dns")
+	}
+}
+
+func TestConfig_ValidateAndSetDefaultsWithInvalidDNSQueryType(t *testing.T) {
+	dns := &Config{
+		QueryType: "B",
+		QueryName: "example.com",
+	}
+	err := dns.ValidateAndSetDefault()
+	if err == nil {
+		t.Error("Should've returned an error because endpoint's dns query type is invalid, it needs to be a valid query name like A, AAAA, CNAME...")
+	}
+}