1 files changed, 77 insertions, 0 deletions
diff --git a/cmd/vartan/parse.go b/cmd/vartan/parse.go
new file mode 100644
index 0000000..0f262b4
--- /dev/null
+++ b/cmd/vartan/parse.go
@@ -0,0 +1,77 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"os"
+
+	"github.com/nihei9/vartan/driver"
+	"github.com/nihei9/vartan/spec"
+	"github.com/spf13/cobra"
+)
+
+var lexFlags = struct {
+	source *string
+}{}
+
+func init() {
+	cmd := &cobra.Command{
+		Use:     "parse <grammar file path>",
+		Short:   "Parse a text stream",
+		Example: `  cat src | vartan parse grammar.json`,
+		Args:    cobra.ExactArgs(1),
+		RunE:    runParse,
+	}
+	lexFlags.source = cmd.Flags().StringP("source", "s", "", "source file path (default stdin)")
+	rootCmd.AddCommand(cmd)
+}
+
+func runParse(cmd *cobra.Command, args []string) (retErr error) {
+	cgram, err := readCompiledGrammar(args[0])
+	if err != nil {
+		return fmt.Errorf("Cannot read a compiled grammar: %w", err)
+	}
+
+	var p *driver.Parser
+	{
+		src := os.Stdin
+		if *lexFlags.source != "" {
+			f, err := os.Open(*lexFlags.source)
+			if err != nil {
+				return fmt.Errorf("Cannot open the source file %s: %w", *lexFlags.source, err)
+			}
+			defer f.Close()
+			src = f
+		}
+		p, err = driver.NewParser(cgram, src)
+		if err != nil {
+			return err
+		}
+	}
+
+	err = p.Parse()
+	if err != nil {
+		return err
+	}
+	fmt.Printf("Accepted\n")
+
+	return nil
+}
+
+func readCompiledGrammar(path string) (*spec.CompiledGrammar, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	data, err := ioutil.ReadAll(f)
+	if err != nil {
+		return nil, err
+	}
+	cgram := &spec.CompiledGrammar{}
+	err = json.Unmarshal(data, cgram)
+	if err != nil {
+		return nil, err
+	}
+	return cgram, nil
+}