From f2986c7a7910b9e3bae265f93dcf2984b07a6059 Mon Sep 17 00:00:00 2001
From: Brian Picciano <mediocregopher@gmail.com>
Date: Sat, 23 Jul 2016 10:34:14 -0600
Subject: [PATCH] implement block comments in the lexer

---
 lexer/lexer.go      | 36 +++++++++++++++++++++++++++++++-
 lexer/lexer_test.go | 50 +++++++++++++++++++++++++++++----------------
 2 files changed, 67 insertions(+), 19 deletions(-)

diff --git a/lexer/lexer.go b/lexer/lexer.go
index 2fc3355..3886ffa 100644
--- a/lexer/lexer.go
+++ b/lexer/lexer.go
@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"log"
 	"strings"
 )
 
@@ -189,6 +190,9 @@ func (l *Lexer) Next() Token {
 	return t
 }
 
+////////////////////////////////////////////////////////////////////////////////
+// the actual fsm
+
 var whitespaceSet = " \n\r\t\v\f"
 var punctuationSet = ",{}()<>|"
 var identifierSepSet = whitespaceSet + punctuationSet
@@ -203,8 +207,10 @@ func lex(l *Lexer) lexerFn {
 	// handle comments first, cause we have to peek for those. We ignore errors,
 	// and assume that any error that would happen here will happen again the
 	// next read
-	if n, _ := l.peekRune(); n == '/' {
+	if n, _ := l.peekRune(); r == '/' && n == '/' {
 		return lexLineComment
+	} else if r == '/' && n == '*' {
+		return lexBlockComment
 	}
 
 	return lexSingleRune(l, r)
@@ -257,6 +263,34 @@ func lexLineComment(l *Lexer) lexerFn {
 	return lexLineComment
 }
 
+// assumes the starting / has been read already
+func lexBlockComment(l *Lexer) lexerFn {
+	depth := 1
+	log.Printf("in block comment")
+
+	var recurse lexerFn
+	recurse = func(l *Lexer) lexerFn {
+		r, err := l.readRune()
+		if err != nil {
+			l.emitErr(err)
+			return nil
+		}
+		n, _ := l.peekRune()
+
+		if r == '/' && n == '*' {
+			depth++
+		} else if r == '*' && n == '/' {
+			depth--
+		}
+
+		if depth == 0 {
+			return lexSkipThen(lex)
+		}
+		return recurse
+	}
+	return recurse
+}
+
 func lexStrStart(lexer *Lexer, r rune, then lexerFn) lexerFn {
 	lexer.bufferRune(r)
 	return then
diff --git a/lexer/lexer_test.go b/lexer/lexer_test.go
index b80d9aa..7fa0e00 100644
--- a/lexer/lexer_test.go
+++ b/lexer/lexer_test.go
@@ -18,6 +18,20 @@ var lexTestSrc = `
 	1.5
 	1.5e9
 
+	/*
+		some stuff
+	*/
+
+	/* this should actually work */
+	/*/
+
+	/*
+		nested!
+		/*
+			wtf this is crazy
+		*/
+	*/
+
 	(punctuation,is{cool}<> )
 	-tab
 
@@ -46,24 +60,24 @@ func TestLex(t *T) {
 	assertNext(Identifier, "100", 6, 2)
 	assertNext(Identifier, "1.5", 7, 2)
 	assertNext(Identifier, "1.5e9", 8, 2)
-	assertNext(Punctuation, "(", 10, 2)
-	assertNext(Identifier, "punctuation", 10, 3)
-	assertNext(Punctuation, ",", 10, 14)
-	assertNext(Identifier, "is", 10, 15)
-	assertNext(Punctuation, "{", 10, 17)
-	assertNext(Identifier, "cool", 10, 18)
-	assertNext(Punctuation, "}", 10, 22)
-	assertNext(Punctuation, "<", 10, 23)
-	assertNext(Punctuation, ">", 10, 24)
-	assertNext(Punctuation, ")", 10, 26)
-	assertNext(Identifier, "-tab", 11, 2)
-	assertNext(String, `"this is a string"`, 13, 2)
-	assertNext(Punctuation, ",", 13, 20)
-	assertNext(String, `"and so is this one"`, 13, 22)
-	assertNext(String, `"\"foo"`, 14, 2)
-	assertNext(String, `"bar\"baz\""`, 15, 2)
-	assertNext(String, `"buz\0"`, 16, 2)
-	assertNext(EOF, "EOF", 17, 0)
+	assertNext(Punctuation, "(", 24, 2)
+	assertNext(Identifier, "punctuation", 24, 3)
+	assertNext(Punctuation, ",", 24, 14)
+	assertNext(Identifier, "is", 24, 15)
+	assertNext(Punctuation, "{", 24, 17)
+	assertNext(Identifier, "cool", 24, 18)
+	assertNext(Punctuation, "}", 24, 22)
+	assertNext(Punctuation, "<", 24, 23)
+	assertNext(Punctuation, ">", 24, 24)
+	assertNext(Punctuation, ")", 24, 26)
+	assertNext(Identifier, "-tab", 25, 2)
+	assertNext(String, `"this is a string"`, 27, 2)
+	assertNext(Punctuation, ",", 27, 20)
+	assertNext(String, `"and so is this one"`, 27, 22)
+	assertNext(String, `"\"foo"`, 28, 2)
+	assertNext(String, `"bar\"baz\""`, 29, 2)
+	assertNext(String, `"buz\0"`, 30, 2)
+	assertNext(EOF, "EOF", 31, 0)
 
 	assert.False(t, l.HasNext())
 }