From 3edf777c6804dcff30d2b25b234de6c05a35902d Mon Sep 17 00:00:00 2001
From: Alejandro Mery <amery@jpi.io>
Date: Sun, 4 Jul 2021 00:40:22 +0100
Subject: [PATCH] lexer: add Lexer.AtLeast() to gather input data from the
 Feeder

Signed-off-by: Alejandro Mery <amery@jpi.io>
---
 lexer/lexer.go | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/lexer/lexer.go b/lexer/lexer.go
index 8033769..e9bad1c 100644
--- a/lexer/lexer.go
+++ b/lexer/lexer.go
@@ -16,6 +16,8 @@ type Lexer interface {
 	Position() TokenPosition // base for the next token
 	Tokens() <-chan Token    // tokens output
 
+	AtLeast(n int) ([]rune, error)
+
 	NewLine()
 	Step(n int)
 
@@ -51,6 +53,21 @@ func (lex *lexer) Run() {
 	}
 }
 
+func (lex *lexer) AtLeast(n int) ([]rune, error) {
+	min := lex.cursor
+	if n > 0 {
+		min += n
+	}
+
+	s, err := lex.in.AtLeast(min)
+	if len(s) > lex.cursor {
+		s = s[lex.cursor:]
+	} else {
+		s = nil
+	}
+	return s, err
+}
+
 func (lex *lexer) Position() TokenPosition {
 	return lex.pos
 }