1 files changed, 110 insertions, 0 deletions
diff --git a/src/urubu/cmd/vartan/parse.go b/src/urubu/cmd/vartan/parse.go
new file mode 100644
index 0000000..9c5fd9c
--- /dev/null
+++ b/src/urubu/cmd/vartan/parse.go
@@ -0,0 +1,110 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	driver "urubu/driver/parser"
+	spec "urubu/spec/grammar"
+)
+
+
+
+func runParse(args []string) error {
+	cg, err := readCompiledGrammar(args[0])
+	if err != nil {
+		return fmt.Errorf("Cannot read a compiled grammar: %w", err)
+	}
+
+	src := os.Stdin
+	gram := driver.NewGrammar(cg)
+
+	tb := driver.NewDefaultSyntaxTreeBuilder()
+	treeAct := driver.NewCSTActionSet(gram, tb)
+
+	opts := []driver.ParserOption{}
+	opts = append(opts, driver.SemanticAction(treeAct))
+
+	toks, err := driver.NewTokenStream(cg, src)
+	if err != nil {
+		return err
+	}
+
+	p, err := driver.NewParser(toks, gram, opts...)
+	if err != nil {
+		return err
+	}
+
+	err = p.Parse()
+	if err != nil {
+		return err
+	}
+
+	// A parser can construct a parse tree even if syntax errors occur.
+	// When therer is a parse tree, print it.
+	if tree := tb.Tree(); tree != nil {
+		b, err := json.Marshal(tree)
+		if err != nil {
+			return err
+		}
+		fmt.Fprintln(os.Stdout, string(b))
+	}
+
+	if len(p.SyntaxErrors()) > 0 {
+		var b strings.Builder
+		synErrs := p.SyntaxErrors()
+		writeSyntaxErrorMessage(&b, cg, synErrs[0])
+		for _, synErr := range synErrs[1:] {
+			fmt.Fprintf(&b, "\n")
+			writeSyntaxErrorMessage(&b, cg, synErr)
+		}
+		if b.Len() > 0 {
+			return fmt.Errorf(b.String())
+		}
+	}
+
+	return nil
+}
+
+func readCompiledGrammar(path string) (*spec.CompiledGrammar, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	data, err := io.ReadAll(f)
+	if err != nil {
+		return nil, err
+	}
+	cg := &spec.CompiledGrammar{}
+	err = json.Unmarshal(data, cg)
+	if err != nil {
+		return nil, err
+	}
+	return cg, nil
+}
+
+func writeSyntaxErrorMessage(b *strings.Builder, cgram *spec.CompiledGrammar, synErr *driver.SyntaxError) {
+	fmt.Fprintf(b, "%v:%v: %v: ", synErr.Row+1, synErr.Col+1, synErr.Message)
+
+	tok := synErr.Token
+	switch {
+	case tok.EOF():
+		fmt.Fprintf(b, "<eof>")
+	case tok.Invalid():
+		fmt.Fprintf(b, "'%v' (<invalid>)", string(tok.Lexeme()))
+	default:
+		if kind := cgram.Syntactic.Terminals[tok.TerminalID()]; kind != "" {
+			fmt.Fprintf(b, "'%v' (%v)", string(tok.Lexeme()), kind)
+		} else {
+			fmt.Fprintf(b, "'%v'", string(tok.Lexeme()))
+		}
+	}
+
+	fmt.Fprintf(b, ": expected: %v", synErr.ExpectedTerminals[0])
+	for _, t := range synErr.ExpectedTerminals[1:] {
+		fmt.Fprintf(b, ", %v", t)
+	}
+}