1 files changed, 85 insertions, 0 deletions
diff --git a/pkg/variables.go b/pkg/variables.go
new file mode 100644
index 0000000..ed09d31
--- /dev/null
+++ b/pkg/variables.go
@@ -0,0 +1,85 @@
+package gonf
+
+import (
+	"fmt"
+	"log/slog"
+)
+
+// ----- Globals ---------------------------------------------------------------
+var variables map[string]*VariablePromise
+
+// ----- Init ------------------------------------------------------------------
+func init() {
+	variables = make(map[string]*VariablePromise)
+}
+
+// ----- Public ----------------------------------------------------------------
+func AppendVariable(name string, values ...string) *VariablePromise {
+	if v, ok := variables[name]; ok {
+		if l, ok := v.value.(*StringsListValue); ok {
+			l.Append(values...)
+		}
+		return v
+	}
+	v := &VariablePromise{
+		isDefault: false,
+		name:      name,
+		value:     &StringsListValue{values},
+	}
+	variables[name] = v
+	return v
+}
+
+func Default(name string, value string) *VariablePromise {
+	if v, ok := variables[name]; ok {
+		if !v.isDefault {
+			slog.Debug("default would overwrite a variable, ignoring", "name", name, "old_value", v.value, "new_value", value)
+			return nil
+		}
+		slog.Error("default is being overwritten", "name", name, "old_value", v.value, "new_value", value)
+	}
+	v := &VariablePromise{
+		isDefault: true,
+		name:      name,
+		value:     interfaceToTemplateValue(value),
+	}
+	variables[name] = v
+	return v
+}
+
+func Variable(name string, value string) *VariablePromise {
+	if v, ok := variables[name]; ok && !v.isDefault {
+		slog.Error("variable is being overwritten", "name", name, "old_value", v, "new_value", value)
+	}
+	v := &VariablePromise{
+		isDefault: false,
+		name:      name,
+		value:     interfaceToTemplateValue(value),
+	}
+	variables[name] = v
+	return v
+}
+
+type VariablePromise struct {
+	isDefault bool
+	name      string
+	value     Value
+}
+
+// We want VariablePromise to satisfy the Value interface
+func (s VariablePromise) Bytes() []byte {
+	return s.value.Bytes()
+}
+func (s VariablePromise) String() string {
+	return s.value.String()
+}
+
+// ----- Internal --------------------------------------------------------------
+func getVariable(name string) string {
+	if v, ok := variables[name]; ok {
+		return v.value.String()
+	} else {
+		slog.Error("undefined variable or default", "name", name)
+		panic(fmt.Sprintf("undefined variable or default %s", name))
+	}
+}