Refactor projectmetadata into separate package.

Replace regular expressions to extract fields from a text proto with
and actual parsed protobuf.

Refactor TestFS into its own package, and implement StatFS.

Test: m droid dist cts alllicensemetadata

Test: repo forall -c 'echo -n "$REPO_PATH  " && $ANDROID_BUILD_TOP/out/host/linux-x86/bin/compliance_checkmetadata . 2>&1' | fgrep -v PASS

Change-Id: Icd17a6a2b6a4e2b6ffded48e964b9c9d6e4d64d6
diff --git a/tools/compliance/cmd/checkmetadata/checkmetadata.go b/tools/compliance/cmd/checkmetadata/checkmetadata.go
new file mode 100644
index 0000000..c6c84e4
--- /dev/null
+++ b/tools/compliance/cmd/checkmetadata/checkmetadata.go
@@ -0,0 +1,148 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"io"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"android/soong/response"
+	"android/soong/tools/compliance"
+	"android/soong/tools/compliance/projectmetadata"
+)
+
+var (
+	failNoneRequested = fmt.Errorf("\nNo projects requested")
+)
+
+func main() {
+	var expandedArgs []string
+	for _, arg := range os.Args[1:] {
+		if strings.HasPrefix(arg, "@") {
+			f, err := os.Open(strings.TrimPrefix(arg, "@"))
+			if err != nil {
+				fmt.Fprintln(os.Stderr, err.Error())
+				os.Exit(1)
+			}
+
+			respArgs, err := response.ReadRspFile(f)
+			f.Close()
+			if err != nil {
+				fmt.Fprintln(os.Stderr, err.Error())
+				os.Exit(1)
+			}
+			expandedArgs = append(expandedArgs, respArgs...)
+		} else {
+			expandedArgs = append(expandedArgs, arg)
+		}
+	}
+
+	flags := flag.NewFlagSet("flags", flag.ExitOnError)
+
+	flags.Usage = func() {
+		fmt.Fprintf(os.Stderr, `Usage: %s {-o outfile} projectdir {projectdir...}
+
+Tries to open the METADATA.android or METADATA file in each projectdir
+reporting any errors on stderr.
+
+Reports "FAIL" to stdout if any errors found and exits with status 1.
+
+Otherwise, reports "PASS" and the number of project metadata files
+found exiting with status 0.
+`, filepath.Base(os.Args[0]))
+		flags.PrintDefaults()
+	}
+
+	outputFile := flags.String("o", "-", "Where to write the output. (default stdout)")
+
+	flags.Parse(expandedArgs)
+
+	// Must specify at least one root target.
+	if flags.NArg() == 0 {
+		flags.Usage()
+		os.Exit(2)
+	}
+
+	if len(*outputFile) == 0 {
+		flags.Usage()
+		fmt.Fprintf(os.Stderr, "must specify file for -o; use - for stdout\n")
+		os.Exit(2)
+	} else {
+		dir, err := filepath.Abs(filepath.Dir(*outputFile))
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "cannot determine path to %q: %s\n", *outputFile, err)
+			os.Exit(1)
+		}
+		fi, err := os.Stat(dir)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "cannot read directory %q of %q: %s\n", dir, *outputFile, err)
+			os.Exit(1)
+		}
+		if !fi.IsDir() {
+			fmt.Fprintf(os.Stderr, "parent %q of %q is not a directory\n", dir, *outputFile)
+			os.Exit(1)
+		}
+	}
+
+	var ofile io.Writer
+	ofile = os.Stdout
+	var obuf *bytes.Buffer
+	if *outputFile != "-" {
+		obuf = &bytes.Buffer{}
+		ofile = obuf
+	}
+
+	err := checkProjectMetadata(ofile, os.Stderr, compliance.FS, flags.Args()...)
+	if err != nil {
+		if err == failNoneRequested {
+			flags.Usage()
+		}
+		fmt.Fprintf(os.Stderr, "%s\n", err.Error())
+		fmt.Fprintln(ofile, "FAIL")
+		os.Exit(1)
+	}
+	if *outputFile != "-" {
+		err := os.WriteFile(*outputFile, obuf.Bytes(), 0666)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "could not write output to %q from %q: %s\n", *outputFile, os.Getenv("PWD"), err)
+			os.Exit(1)
+		}
+	}
+	os.Exit(0)
+}
+
+// checkProjectMetadata implements the checkmetadata utility.
+func checkProjectMetadata(stdout, stderr io.Writer, rootFS fs.FS, projects ...string) error {
+
+	if len(projects) < 1 {
+		return failNoneRequested
+	}
+
+	// Read the project metadata files from `projects`
+	ix := projectmetadata.NewIndex(rootFS)
+	pms, err := ix.MetadataForProjects(projects...)
+	if err != nil {
+		return fmt.Errorf("Unable to read project metadata file(s) %q from %q: %w\n", projects, os.Getenv("PWD"), err)
+	}
+
+	fmt.Fprintf(stdout, "PASS -- parsed %d project metadata files for %d projects\n", len(pms), len(projects))
+	return nil
+}