Add validation of lexical specs and improve error messages

1 files changed, 82 insertions, 7 deletions

diff --git a/spec/spec.go b/spec/spec.go
index d827b68..0f9b484 100644
--- a/spec/spec.go
+++ b/spec/spec.go
@@ -1,21 +1,96 @@
 package spec
 
+import (
+	"fmt"
+	"regexp"
+	"strings"
+)
+
+const lexKindPattern = "[A-Za-z_][0-9A-Za-z_]*"
+
+var lexKindRE = regexp.MustCompile(lexKindPattern)
+
+type LexKind string
+
+const LexKindNil = LexKind("")
+
+func (k LexKind) String() string {
+	return string(k)
+}
+
+func (k LexKind) validate() error {
+	if k == "" {
+		return fmt.Errorf("kind doesn't allow to be the empty string")
+	}
+	if !lexKindRE.Match([]byte(k)) {
+		return fmt.Errorf("kind must be %v", lexKindPattern)
+	}
+	return nil
+}
+
+type LexPattern string
+
+func (p LexPattern) validate() error {
+	if p == "" {
+		return fmt.Errorf("pattern doesn't allow to be the empty string")
+	}
+	return nil
+}
+
 type LexEntry struct {
-	Kind    string `json:"kind"`
-	Pattern string `json:"pattern"`
+	Kind    LexKind    `json:"kind"`
+	Pattern LexPattern `json:"pattern"`
 }
 
-func NewLexEntry(kind string, pattern string) *LexEntry {
-	return &LexEntry{
-		Kind:    kind,
-		Pattern: pattern,
+func (e *LexEntry) validate() error {
+	err := e.Kind.validate()
+	if err != nil {
+		return err
+	}
+	err = e.Pattern.validate()
+	if err != nil {
+		return err
 	}
+	return nil
 }
 
 type LexSpec struct {
 	Entries []*LexEntry `json:"entries"`
 }
 
+func (s *LexSpec) Validate() error {
+	if len(s.Entries) <= 0 {
+		return fmt.Errorf("the lexical specification must have at least one entry")
+	}
+	{
+		var errs []error
+		for i, e := range s.Entries {
+			err := e.validate()
+			if err != nil {
+				errs = append(errs, fmt.Errorf("entry #%v: %w", i+1, err))
+			}
+		}
+		if len(errs) > 0 {
+			var b strings.Builder
+			fmt.Fprintf(&b, "%v", errs[0])
+			for _, err := range errs[1:] {
+				fmt.Fprintf(&b, "\n%v", err)
+			}
+			return fmt.Errorf(b.String())
+		}
+	}
+	{
+		ks := map[string]struct{}{}
+		for _, e := range s.Entries {
+			if _, exist := ks[e.Kind.String()]; exist {
+				return fmt.Errorf("kinds `%v` are duplicates", e.Kind)
+			}
+			ks[e.Kind.String()] = struct{}{}
+		}
+	}
+	return nil
+}
+
 type TransitionTable struct {
 	InitialState    int         `json:"initial_state"`
 	AcceptingStates map[int]int `json:"accepting_states"`
@@ -23,6 +98,6 @@ type TransitionTable struct {
 }
 
 type CompiledLexSpec struct {
-	Kinds []string         `json:"kinds"`
+	Kinds []LexKind        `json:"kinds"`
 	DFA   *TransitionTable `json:"dfa"`
 }