huge refactoring

internal/pkg/xassert/string.go

@@ -0,0 +1,60 @@
+package xassert
+
+import (
+	"fmt"
+
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xerror"
+)
+
+// RuleString is an interface for
+// validating a string.
+type RuleString interface {
+	with(key, value string)
+	validate() error
+}
+
+type baseRuleString struct {
+	key   string
+	value string
+}
+
+func (r *baseRuleString) with(key, value string) {
+	r.key = key
+	r.value = value
+}
+
+type ruleStringOneOf struct {
+	*baseRuleString
+	values []string
+}
+
+func (r ruleStringOneOf) validate() error {
+	const op string = "xassert.ruleStringOneOf.validate"
+	for _, v := range r.values {
+		if r.value == v {
+			return nil
+		}
+	}
+	return xerror.Invalid(
+		op,
+		fmt.Sprintf("'%s' should be one of '%v', got '%s'", r.key, r.values, r.value),
+		nil,
+	)
+}
+
+/*
+StringOneOf returns a RuleString for
+validating that a string is one of given
+values.
+*/
+func StringOneOf(values []string) RuleString {
+	return ruleStringOneOf{
+		&baseRuleString{},
+		values,
+	}
+}
+
+// Compile-time checks to ensure type implements desired interfaces.
+var (
+	_ = RuleString(new(ruleStringOneOf))
+)