Initial code commit

This is extracted from oscalkit project. Similarly as NIST extracted metaschema
out of original OSCAL repo, I am extracting metaschema to a separate repo.

See: https://github.com/usnistgov/metaschema

go.mod

@@ -0,0 +1,5 @@
+module github.com/gocomply/metaschema
+
+go 1.13
+
+require github.com/iancoleman/strcase v0.0.0-20191112232945-16388991a334

go.sum

@@ -0,0 +1,2 @@
+github.com/iancoleman/strcase v0.0.0-20191112232945-16388991a334 h1:VHgatEHNcBFEB7inlalqfNqw65aNkM1lGX2yt3NmbS8=
+github.com/iancoleman/strcase v0.0.0-20191112232945-16388991a334/go.mod h1:SK73tn/9oHe+/Y0h39VT4UCxmurVJkR5NA7kMEAOgSE=

metaschema/generate.go

@@ -0,0 +1,94 @@
+// +build ignore
+
+package main
+
+import (
+	"encoding/xml"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"os/exec"
+
+	"github.com/gocomply/metaschema/metaschema"
+)
+
+const (
+	oscalRepo         = "https://github.com/usnistgov/OSCAL.git"
+	metaschemaBaseDir = "OSCAL/src/metaschema/%s"
+)
+
+func main() {
+	rmCmd := exec.Command("rm", "-rf", "OSCAL/")
+	if err := rmCmd.Run(); err != nil {
+		log.Fatal(err)
+	}
+
+	cloneCmd := exec.Command("git", "clone", "--depth", "1", oscalRepo)
+	if err := cloneCmd.Run(); err != nil {
+		log.Fatal(err)
+	}
+
+	metaschemaPaths := map[string]string{
+		"validation_root": "oscal_metadata_metaschema.xml",
+		"nominal_catalog": "oscal_control-common_metaschema.xml",
+		"catalog":         "oscal_catalog_metaschema.xml",
+		"profile":         "oscal_profile_metaschema.xml",
+		"implementation":  "oscal_implementation-common_metaschema.xml",
+		"ssp":             "oscal_ssp_metaschema.xml",
+		"component":       "oscal_component_metaschema.xml",
+	}
+
+	for _, metaschemaPath := range metaschemaPaths {
+		f, err := os.Open(fmt.Sprintf(metaschemaBaseDir, metaschemaPath))
+		if err != nil {
+			log.Fatal(err)
+		}
+		defer f.Close()
+
+		meta, err := decode(f)
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		if err := metaschema.GenerateTypes(meta); err != nil {
+			log.Fatalf("Error generating go types for metaschema: %s", err)
+		}
+	}
+
+	rmCmd = exec.Command("rm", "-rf", "OSCAL/")
+	if err := rmCmd.Run(); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func decode(r io.Reader) (*metaschema.Metaschema, error) {
+	var meta metaschema.Metaschema
+
+	d := xml.NewDecoder(r)
+
+	if err := d.Decode(&meta); err != nil {
+		return nil, fmt.Errorf("Error decoding metaschema: %s", err)
+	}
+
+	for _, imported := range meta.Import {
+		if imported.Href == nil {
+			return nil, fmt.Errorf("import element in %s is missing 'href' attribute", r)
+		}
+		imf, err := os.Open(fmt.Sprintf(metaschemaBaseDir, imported.Href.URL.String()))
+		if err != nil {
+			return nil, err
+		}
+		defer imf.Close()
+
+		importedMeta, err := decode(imf)
+		if err != nil {
+			return nil, err
+		}
+
+		meta.ImportedMetaschema = append(meta.ImportedMetaschema, *importedMeta)
+	}
+	err := meta.LinkDefinitions()
+
+	return &meta, err
+}