First working version

internal/generator/mapper.go

@@ -0,0 +1,48 @@
+package generator
+
+import (
+	"fmt"
+	"strings"
+)
+
+// GenerateMapper generates the mapper snippet (without imports)
+func GenerateMapper(ctx *Context) (string, error) {
+	var b strings.Builder
+
+	// Mapper registration (snippet only, no imports)
+	b.WriteString("    mapper_registry.map_imperatively(\n")
+	b.WriteString(fmt.Sprintf("        class_=%s,\n", ctx.EntityName))
+	b.WriteString(fmt.Sprintf("        local_table=%s,\n", ctx.TableConstant))
+	b.WriteString("        properties={\n")
+
+	// Generate relationships for all foreign keys
+	fkRelationships := make(map[string][]string) // entity -> []column_names
+
+	for _, fk := range ctx.TableInfo.ForeignKeys {
+		relationName := GetRelationshipName(fk.ColumnName)
+		entityName := GetRelationshipEntityName(fk.ForeignTableName)
+
+		// Group by entity name to handle multiple FKs to same table
+		fkRelationships[entityName] = append(fkRelationships[entityName], fk.ColumnName)
+
+		if len(fkRelationships[entityName]) == 1 {
+			// First FK to this table
+			b.WriteString(fmt.Sprintf("            \"%s\": relationship(\n", relationName))
+			b.WriteString(fmt.Sprintf("                %s, lazy=relationship_loading_strategy.value\n", entityName))
+		} else {
+			// Multiple FKs to same table, need to specify foreign_keys
+			b.WriteString(fmt.Sprintf("            \"%s\": relationship(\n", relationName))
+			b.WriteString(fmt.Sprintf("                %s,\n", entityName))
+			b.WriteString("                lazy=relationship_loading_strategy.value,\n")
+			b.WriteString(fmt.Sprintf("                foreign_keys=%s.columns.%s,\n",
+				ctx.TableConstant, fk.ColumnName))
+		}
+
+		b.WriteString("            ),\n")
+	}
+
+	b.WriteString("        },\n")
+	b.WriteString("    )\n")
+
+	return b.String(), nil
+}