view cmd/sievemgr/internal/config/scanner.go @ 5:4dff4c3f0fbb

Introduce configuration file where account information is specified Introduce a configuration file where account information must be specified instead of passing it with each invocation on the command line. Each account has a name by which it can be selected and one may be specified as the default account. This is intended to improve usability for productive usage. Enforce strict permissions since passwords may be specified for non-interactive usage. Remove command-line flags for passing account information.
author Guido Berhoerster <guido+sievemgr@berhoerster.name>
date Tue, 03 Nov 2020 23:44:45 +0100
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// Copyright (C) 2020 Guido Berhoerster <guido+sievemgr@berhoerster.name>
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
// IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
// SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

package config

import (
	"bufio"
	"fmt"
	"io"
	"strings"
	"unicode"
)

type token int

const (
	tokenEOF token = -(iota + 1)
	tokenIllegal
	tokenIdent
	tokenNumber
	tokenString
)

func (tok token) String() string {
	switch tok {
	case tokenIllegal:
		return "illegal"
	case tokenEOF:
		return "EOF"
	case tokenIdent:
		return "identifier"
	case tokenNumber:
		return "number"
	case tokenString:
		return "string"
	default:
		return "unknown"
	}
}

func isWhitespaceRune(r rune) bool {
	return r == ' ' || r == '\t' || r == '\r' || r == '\n'
}

func isIdentRune(r rune) bool {
	return r >= 'A' && r <= 'Z' || r >= 'a' && r <= 'z'
}

func isNumberRune(r rune) bool {
	return r >= '0' && r <= '9'
}

type scanner struct {
	br       *bufio.Reader
	line     int  // line number for error messages
	r        rune // last read rune
	rdSize   int  // last read size
	rdOffset int  // offset from beginning of file
}

func newScanner(br *bufio.Reader) *scanner {
	return &scanner{line: 1, br: br}
}

func (s *scanner) read() error {
	var size int
again:
	r, size, err := s.br.ReadRune()
	if err != nil {
		return err
	}

	// skip over BOM at the beginning of the file
	if r == bom && s.rdOffset == 0 {
		s.rdOffset += size
		goto again
	}

	if s.r == '\n' {
		s.line++
	}

	s.r = r
	s.rdOffset += size
	s.rdSize = size

	if r == unicode.ReplacementChar && size == 1 {
		return fmt.Errorf("illegal UTF-8 sequence")
	} else if r == 0 {
		return fmt.Errorf("illegal nul byte")
	}
	return nil
}

func (s *scanner) unread() {
	if s.br.UnreadRune() != nil {
		return
	}

	if b, _ := s.br.Peek(1); b[0] == '\n' {
		// moved back to the previous line
		s.line--
	}

	s.r = 0
	s.rdOffset -= s.rdSize
	s.rdSize = 0
}

func (s *scanner) skipWhitespace() error {
	for {
		if err := s.read(); err == io.EOF {
			break
		} else if err != nil {
			return err
		} else if !isWhitespaceRune(s.r) {
			s.unread()
			break
		}
	}
	return nil
}

func (s *scanner) scanIdent() (token, string, error) {
	var sb strings.Builder
	for {
		if err := s.read(); err == io.EOF {
			break
		} else if err != nil {
			return tokenIllegal, "", err
		}
		if isIdentRune(s.r) {
			sb.WriteRune(s.r)
		} else if isWhitespaceRune(s.r) {
			s.unread()
			break
		} else {
			return tokenIllegal, "", fmt.Errorf("illegal rune in identifier: %q", s.r)
		}
	}
	if sb.Len() == 0 {
		return tokenIllegal, "", fmt.Errorf("expected identifier, got %q", s.r)
	}
	return tokenIdent, sb.String(), nil
}

func (s *scanner) scanNumber() (token, string, error) {
	var sb strings.Builder
	for {
		if err := s.read(); err == io.EOF {
			break
		} else if err != nil {
			return tokenIllegal, "", err
		}
		if isNumberRune(s.r) {
			sb.WriteRune(s.r)
		} else if isWhitespaceRune(s.r) {
			s.unread()
			break
		} else {
			return tokenIllegal, "", fmt.Errorf("illegal rune in number: %q", s.r)
		}
	}
	if sb.Len() == 0 {
		return tokenIllegal, "", fmt.Errorf("expected number, got %q", s.r)
	}
	return tokenNumber, sb.String(), nil
}

func (s *scanner) scanString() (token, string, error) {
	if err := s.read(); err == io.EOF {
		return tokenIllegal, "", fmt.Errorf("unexpected EOF")
	} else if err != nil {
		return tokenIllegal, "", err
	}

	if s.r != '"' {
		return tokenIllegal, "",
			fmt.Errorf("expected '\"', got %q", s.r)
	}

	var sb strings.Builder
	var inEscape bool
	for {
		if err := s.read(); err == io.EOF {
			return tokenIllegal, "", fmt.Errorf("unterminated string")
		} else if err != nil {
			return tokenIllegal, "", err
		}

		if s.r == '\\' && !inEscape {
			inEscape = true
		} else if s.r == '"' && !inEscape {
			break
		} else {
			sb.WriteRune(s.r)
			inEscape = false
		}
	}

	return tokenString, sb.String(), nil
}

func (s *scanner) scan() (token, string, error) {
	if err := s.skipWhitespace(); err != nil {
		return tokenIllegal, "", err
	}

	if err := s.read(); err == io.EOF {
		return tokenEOF, "", nil
	} else if err != nil {
		return tokenIllegal, "", err
	}
	r := s.r
	s.unread()

	switch {
	case isIdentRune(r):
		return s.scanIdent()
	case isNumberRune(r):
		return s.scanNumber()
	case r == '"':
		return s.scanString()
	}
	return tokenIllegal, string(r), nil
}