websocket base and command parser

api/ws/commands.go

@@ -0,0 +1,234 @@
+package ws
+
+import (
+	"errors"
+	"io"
+	"strings"
+)
+
+type Command struct {
+	Command string
+	Args []string
+}
+
+type parser struct {
+	cmd *Command
+	r *strings.Reader
+	arg string
+	args []string
+}
+
+type parserQuote rune
+const (
+	parserQuoteSingle parserQuote = '\''
+	parserQuoteDouble parserQuote = '"'
+)
+
+type parserBracket rune
+const (
+	parserBracketCurly parserBracket = '{'
+	parserBracketSquare parserBracket = '['
+	parserBracketTriangle parserBracket = '<'
+)
+var parserClosingBracket = map[parserBracket]rune{
+	parserBracketCurly: '}',
+	parserBracketSquare: ']',
+	parserBracketTriangle: '>',
+}
+
+func parseCommand(msg string) (*Command, error) {
+	cmd := &Command{}
+	r := strings.NewReader(msg)
+	parser := &parser{cmd: cmd, r: r}
+	return cmd, parser.parse()
+}
+
+func (p *parser) parse() error {
+	err := p.stateBase()
+	if err != nil {
+		return err
+	}
+
+	p.args = append(p.args, p.arg)
+
+	filteredArgs := []string{}
+	for _, arg := range p.args {
+		if arg != "" {
+			filteredArgs = append(filteredArgs, arg)
+		}
+	}
+	
+	if len(p.args) >= 1 {
+		p.cmd.Command = p.args[0]
+	}
+	
+	if len(p.args) >= 2 {
+		p.cmd.Args = p.args[1:]
+	}
+
+	return nil
+}
+
+func (p *parser) consume() (rune, bool, error) {
+	b := make([]byte, 1)
+	_, err := p.r.Read(b)
+	if err == io.EOF {
+		return 0, true, nil 
+	}
+	if err != nil {
+		return 0, false, err
+	}
+	return rune(b[0]), false, nil
+}
+
+func (p *parser) push(r rune) {
+	p.arg += string(r)
+}
+
+func (p *parser) flush() {
+	p.args = append(p.args, p.arg)
+	p.arg = ""
+}
+
+func (p *parser) stateBase() error {
+	for {
+		ch, eof, err := p.consume()
+		if err != nil {
+			return err
+		}
+		if eof {
+			return nil
+		}
+
+		switch ch {
+		case '\\':
+			err := p.stateEscape()
+			if err != nil {
+				return err
+			}
+		
+		case rune(parserQuoteDouble): fallthrough
+		case rune(parserQuoteSingle):
+			err := p.stateQuote(parserQuote(ch))
+			if err != nil {
+				return err
+			}
+		
+		// special case, if the arg starts with a { then parse it with rough object mode
+		case rune(parserBracketCurly): fallthrough
+		case rune(parserBracketSquare): fallthrough
+		case rune(parserBracketTriangle):
+			if p.arg != "" {
+				p.push(ch)
+			} else {
+				err := p.stateBracket(parserBracket(ch))
+				if err != nil {
+					return err
+				}
+			}
+
+		case '\n': fallthrough
+		case '\t': fallthrough
+		case ' ':
+			p.flush()
+
+		default:
+			p.push(ch)
+		}
+
+	}
+}
+
+func (p *parser) stateQuote(quote parserQuote) error {
+	for {
+		ch, eof, err := p.consume()
+		if err != nil {
+			return err
+		}
+		if eof {
+			return errors.New("missing closing quote")
+		}
+
+		switch ch {
+		case '\\':
+			err := p.stateEscape()
+			if err != nil {
+				return err
+			}
+		
+		case rune(quote):
+			return nil
+		
+		default:
+			p.push(ch)
+		}
+	}
+}
+
+func (p *parser) stateBracket(bracket parserBracket) error {
+	p.push(rune(bracket))
+	for {
+		ch, eof, err := p.consume()
+		if err != nil {
+			return err
+		}
+		if eof {
+			return errors.New("missing closing bracket")
+		}
+
+		switch ch {
+		case '\\':
+			err := p.stateEscape()
+			if err != nil {
+				return err
+			}
+		
+		case rune(parserQuoteDouble): fallthrough
+		case rune(parserQuoteSingle):
+			p.push(ch)
+			err := p.stateQuote(parserQuote(ch))
+			if err != nil {
+				return err
+			}
+			p.push(ch)
+
+		case rune(parserBracketCurly): fallthrough
+		case rune(parserBracketSquare): fallthrough
+		case rune(parserBracketTriangle):
+			err := p.stateBracket(parserBracket(ch))
+			if err != nil {
+				return err
+			}
+
+		case parserClosingBracket[bracket]:
+			p.push(ch)
+			return nil
+
+		default:
+			p.push(ch)
+		}
+	}
+}
+
+func (p *parser) stateEscape() error {
+	ch, eof, err := p.consume()
+	if err != nil {
+		return err
+	}
+	if eof {
+		return errors.New("invalid escape sequence before end of file")
+	}
+	
+	switch ch {
+	case 'n':
+		p.arg += "\n"
+	
+	case 't':
+		p.arg += "\t"
+	
+	default:
+		p.push(ch)
+	}
+
+	return nil
+}