lexer: introduce StateFn and the basic state machine loop

Signed-off-by: Alejandro Mery <amery@jpi.io>

lexer/lexer.go

@@ -1,60 +1,6 @@
 // Package lexer provides basic helpers to implement parsers
 package lexer
 
-import (
-	"io"
-
-	"asciigoat.org/core/runes"
-)
-
-// Lexer adds Accept and AcceptAll support to a
-// [io.RuneScanner]
-type Lexer struct {
-	io.RuneScanner
-}
-
-// Accept consumes a rune from the source if it meets the condition.
-// it returns true if the condition was met and false if it wasn't.
-func (p Lexer) Accept(cond func(rune) bool) bool {
-	return Accept(p, cond)
-}
-
-// AcceptAll consumes runes from the source as long as they meet the
-// condition. it returns true if the condition was met for at least one rune,
-// and false if it wasn't.
-func (p Lexer) AcceptAll(cond func(rune) bool) bool {
-	return AcceptAll(p, cond)
-}
-
-// NewLexer extends a [io.RuneScanner] with Accept()/AcceptAll()
-// functionality
-func NewLexer(src io.RuneScanner) *Lexer {
-	if src == nil {
-		return nil
-	}
-
-	return &Lexer{src}
-}
-
-// NewLexerReader creates a Lexer from an [io.Reader]
-func NewLexerReader(r io.Reader) *Lexer {
-	if r == nil {
-		return nil
-	}
-
-	return &Lexer{runes.NewReader(r)}
-}
-
-// NewLexerBytes creates a Lexer from raw bytes
-func NewLexerBytes(b []byte) *Lexer {
-	return &Lexer{runes.NewReaderBytes(b)}
-}
-
-// NewLexerString creates a Lexer from a data string
-func NewLexerString(s string) *Lexer {
-	return &Lexer{runes.NewReaderString(s)}
-}
-
 // StateFn is a State Function of the parser
 type StateFn func() (StateFn, error)
 
@@ -69,38 +15,3 @@ func Run(fn StateFn) error {
 
 	return err
 }
-
-// Accept consumes a rune from the source if it meets the condition.
-// it returns true if the condition was met and false if it wasn't.
-func Accept(src io.RuneScanner, cond func(r rune) bool) bool {
-	r, _, err := src.ReadRune()
-	switch {
-	case err != nil:
-		return false
-	case cond(r):
-		return true
-	default:
-		_ = src.UnreadRune()
-		return false
-	}
-}
-
-// AcceptAll consumes runes from the source as long as they meet the
-// condition. it returns true if the condition was met for at least one rune,
-// and false if it wasn't.
-func AcceptAll(src io.RuneScanner, cond func(r rune) bool) bool {
-	var accepted bool
-
-	for {
-		r, _, err := src.ReadRune()
-		switch {
-		case err != nil:
-			return accepted
-		case cond(r):
-			accepted = true
-		default:
-			_ = src.UnreadRune()
-			return accepted
-		}
-	}
-}

lexer/position.go

@@ -1,68 +0,0 @@
-package lexer
-
-import "fmt"
-
-// Position indicates a line and column pair on a file.
-// Counting starts at 1.
-type Position struct {
-	Line   int
-	Column int
-}
-
-// String generates a pretty "(Line, Column)"" representation of the Position
-func (p Position) String() string {
-	if p.Line == 0 {
-		p.Reset()
-	}
-
-	return fmt.Sprintf("(%v, %v)", p.Line, p.Column)
-}
-
-// GoString generates a string representation of the Position for %#v usage
-func (p Position) GoString() string {
-	if p.Line == 0 {
-		p.Reset()
-	}
-
-	return fmt.Sprintf("lexer.Position{%v, %v}", p.Line, p.Column)
-}
-
-// Reset places a position at (1,1)
-func (p *Position) Reset() {
-	p.Line, p.Column = 1, 1
-}
-
-// Step moves the column one place
-func (p *Position) Step() {
-	if p.Line == 0 {
-		p.Reset()
-	}
-
-	p.Column++
-}
-
-// Next returns a new Position one rune forward
-// on the line
-func (p Position) Next() Position {
-	if p.Line == 0 {
-		p.Reset()
-	}
-
-	return Position{
-		Line:   p.Line,
-		Column: p.Column + 1,
-	}
-}
-
-// NextLine returns a new Position at the begining of the next
-// line.
-func (p Position) NextLine() Position {
-	if p.Line == 0 {
-		p.Reset()
-	}
-
-	return Position{
-		Line:   p.Line + 1,
-		Column: 1,
-	}
-}

lexer/reader.go

@@ -1,4 +1,4 @@
-package runes
+package lexer
 
 import (
 	"bytes"
@@ -198,6 +198,41 @@ func (b *Reader) PeekRune() (rune, int, error) {
 	return r, l, err
 }
 
+// Accept consumes a rune from the source if it meets the condition.
+// it returns true if the condition was met and false if it wasn't.
+func (b *Reader) Accept(cond func(r rune) bool) bool {
+	r, _, err := b.ReadRune()
+	switch {
+	case err != nil:
+		return false
+	case cond(r):
+		return true
+	default:
+		_ = b.UnreadRune()
+		return false
+	}
+}
+
+// AcceptAll consumes runes from the source as long as they meet the
+// condition. it returns true if the condition was met for at least one rune,
+// and false if it wasn't.
+func (b *Reader) AcceptAll(cond func(r rune) bool) bool {
+	var accepted bool
+
+	for {
+		r, _, err := b.ReadRune()
+		switch {
+		case err != nil:
+			return accepted
+		case cond(r):
+			accepted = true
+		default:
+			_ = b.UnreadRune()
+			return accepted
+		}
+	}
+}
+
 // NewReader creates a new runes [Reader] using the given [io.Reader]
 func NewReader(r io.Reader) *Reader {
 	if r == nil {

runes/docs.go

@@ -1,2 +0,0 @@
-// Package runes helps us work with runes
-package runes