Add CLI

1 files changed, 82 insertions, 0 deletions

diff --git a/cmd/vartan/compile.go b/cmd/vartan/compile.go
new file mode 100644
index 0000000..769f143
--- /dev/null
+++ b/cmd/vartan/compile.go
@@ -0,0 +1,82 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+
+	"github.com/nihei9/vartan/grammar"
+	"github.com/nihei9/vartan/spec"
+	"github.com/spf13/cobra"
+)
+
+var compileFlags = struct {
+	grammar *string
+	output  *string
+}{}
+
+func init() {
+	cmd := &cobra.Command{
+		Use:     "compile",
+		Short:   "Compile a grammar into a parsing table",
+		Example: `  cat grammar | vartan compile -o grammar.json`,
+		RunE:    runCompile,
+	}
+	compileFlags.grammar = cmd.Flags().StringP("grammar", "g", "", "grammar file path (default stdin)")
+	compileFlags.output = cmd.Flags().StringP("output", "o", "", "output file path (default stdout)")
+	rootCmd.AddCommand(cmd)
+}
+
+func runCompile(cmd *cobra.Command, args []string) (retErr error) {
+	gram, err := readGrammar(*compileFlags.grammar)
+	if err != nil {
+		return err
+	}
+
+	cgram, err := grammar.Compile(gram)
+	if err != nil {
+		return err
+	}
+
+	err = writeCompiledGrammar(cgram, *compileFlags.output)
+	if err != nil {
+		return fmt.Errorf("Cannot write a compiled grammar: %w", err)
+	}
+
+	return nil
+}
+
+func readGrammar(path string) (*grammar.Grammar, error) {
+	r := os.Stdin
+	if path != "" {
+		f, err := os.Open(path)
+		if err != nil {
+			return nil, fmt.Errorf("Cannot open the grammar file %s: %w", path, err)
+		}
+		defer f.Close()
+		r = f
+	}
+	ast, err := spec.Parse(r)
+	if err != nil {
+		return nil, err
+	}
+	return grammar.NewGrammar(ast)
+}
+
+func writeCompiledGrammar(cgram *spec.CompiledGrammar, path string) error {
+	out, err := json.Marshal(cgram)
+	if err != nil {
+		return err
+	}
+	w := os.Stdout
+	if path != "" {
+		f, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
+		if err != nil {
+			return fmt.Errorf("Cannot open the output file %s: %w", path, err)
+		}
+		defer f.Close()
+		w = f
+	}
+	fmt.Fprintf(w, "%v\n", string(out))
+	return nil
+}