refactor aviation parser architecture

internal/adapter/parser/aviation/tokenizer.go

@@ -0,0 +1,61 @@
+package aviation
+
+import "strings"
+
+// Token represents a lexeme in the body with its byte offsets.
+type Token struct {
+	Text  string
+	Start int
+	End   int
+}
+
+// Tokenizer splits text into tokens using a whitespace set.
+// A forward slash is treated as whitespace but is emitted as its own token.
+type Tokenizer struct {
+	Whitespace string
+}
+
+// Tokenize tokenizes input and returns tokens with byte offsets.
+func (t Tokenizer) Tokenize(input string) []Token {
+	if t.Whitespace == "" {
+		t.Whitespace = " \n\t\r"
+	}
+
+	var tokens []Token
+	start := -1
+
+	for idx, r := range input {
+		if strings.ContainsRune(t.Whitespace, r) {
+			if start != -1 {
+				tokens = append(tokens, Token{
+					Text:  input[start:idx],
+					Start: start,
+					End:   idx,
+				})
+				start = -1
+			}
+			if r == '/' {
+				tokens = append(tokens, Token{
+					Text:  "/",
+					Start: idx,
+					End:   idx + 1,
+				})
+			}
+			continue
+		}
+
+		if start == -1 {
+			start = idx
+		}
+	}
+
+	if start != -1 {
+		tokens = append(tokens, Token{
+			Text:  input[start:],
+			Start: start,
+			End:   len(input),
+		})
+	}
+
+	return tokens
+}