Chore: Start rewriting

.gitignore

@@ -5,7 +5,9 @@
 
 !src/
 !src/config/
-!src/config/mapping
+
+!src2/
+!src2/config/
 
 !.editorconfig
 !openttd.cfg

src2/config/mapping.v

@@ -0,0 +1,60 @@
+module config
+
+pub type Mapping = map[string]map[string]Map
+
+// TODO: &Mapping
+pub fn (mpng Mapping) unmap(mapped map[string]map[string]string) !map[string]map[string]string {
+	mut unmapped := map[string]map[string]string{}
+
+	for mapped_section, mapped_fields in mapped {
+		if mapped_section !in mpng {
+			return error('Unknown section: ${mapped_section}')
+		}
+
+		for mapped_field, mapped_value in mapped_fields {
+			if mapped_field !in mpng[mapped_section] {
+				return error('Unknown field: ${mapped_section}.${mapped_field}')
+			}
+
+			mapped_field_mapping := mpng[mapped_section][mapped_field]
+
+			unmapped[mapped_field_mapping.section()][mapped_field_mapping.field()] = mapped_field_mapping.transform(mapped_value)
+		}
+	}
+
+	return unmapped
+}
+
+pub enum ValueType {
+	string
+	integer
+	boolean
+}
+
+// Maps one ManageTTD -> OpenTTD config field.
+[noinit]
+pub struct Map {
+	equivalent  [2]string           [required]
+	transformer ?fn (string) string
+pub:
+	@type         ValueType = .string
+	documentation string    [required]
+}
+
+[inline]
+pub fn (m &Map) section() string {
+	return m.equivalent[0]
+}
+
+[inline]
+pub fn (m &Map) field() string {
+	return m.equivalent[1]
+}
+
+pub fn (m &Map) transform(s string) string {
+	return if transform_fn := m.transformer {
+		transform_fn(s)
+	} else {
+		s
+	}
+}