package sql

import (
	"bufio"
	"io"
)

// Scanner represents a SQL statement scanner.
type Scanner struct {
	r *bufio.Reader
	c []rune
}

// NewScanner returns a new instance of Scanner.
func NewScanner(r io.Reader) *Scanner {
	return &Scanner{
		r: bufio.NewReader(r),
		c: make([]rune, 0),
	}
}

// read reads the next rune from the bufferred reader.
// Returns the rune(0) if an error occurs (or io.EOF is returned).
func (s *Scanner) read() rune {
	ch, _, err := s.r.ReadRune()
	if err != nil {
		return eof
	}
	return ch
}

// Scan returns the next SQL statement.
func (s *Scanner) Scan() string {
	for {
		if ch := s.read(); ch == eof {
			break
		} else if ch == '\'' {
			// Check for ' in c
		} else if !isLetter(ch) && !isDigit(ch) && ch != '_' {
			s.unread()
			break
		} else {
			_, _ = buf.WriteRune(ch)
		}
	}
}

// isWhitespace returns true if the rune is a space, tab, or newline.
func isWhitespace(ch rune) bool { return ch == ' ' || ch == '\t' || ch == '\n' }

// isLetter returns true if the rune is a letter.
func isLetter(ch rune) bool { return (ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z') }

// isDigit returns true if the rune is a digit.
func isDigit(ch rune) bool { return (ch >= '0' && ch <= '9') }

// eof represents a marker rune for the end of the reader.
var eof = rune(0)