scanner.go

// Copyright 2014 The presenti Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package main

import (
	"fmt"
	"go/scanner"
	"go/token"
	"strconv"
	"strings"

	"github.com/dupoxy/presenti/notebook"
)

const generatedby = noteBookMarker + " # DO NOT EDIT GENERATED by presenti */"

// makeNoteBook scan source file and return a *notebook.NoteBook or an error.
// it only looks for toplevel comments with a noteBookMarker that are detached
// from next line.
func makeNoteBook(file string, source []byte) (*notebook.NoteBook, error) {
	nb := notebook.NewNoteBook()
	// add generated comment
	currentNote, err := newFilteredNote(generatedby)
	if err != nil {
		return nil, fmt.Errorf("FilteredNote: %v", err)
	}
	nb.Save(currentNote) // save it
	fset := token.NewFileSet()
	// error handler
	eh := func(_ token.Position, msg string) {
		fmt.Errorf("scanner error handler called (msg = %s)", msg)
	}
	var s scanner.Scanner
	s.Init(fset.AddFile(file, fset.Base(), len(source)), source, eh, scanner.ScanComments)
	nbcommentlit := "" // used to store a found nbcommentlit
	nbcommentline := 0
	expectedline := 0
	for {
		pos, tok, lit := s.Scan()
		if tok == token.EOF {
			// take care of end of file nbcommentlit
			if nbcommentlit != "" && expectedline != 0 {
				nbStart := noteBookMarker + " # from source line " + strconv.Itoa(nbcommentline) + " */"
				currentNoteLine, err := newFilteredNote(nbStart)
				nb.Save(currentNoteLine)
				currentNote, err := newFilteredNote(nbcommentlit)
				if err != nil {
					return nil, fmt.Errorf("FilteredNote: %v", err)
				}
				nb.Save(currentNote) // save it
			}
			break
		}
		switch { // check that nbcommentlit is detached from the current line
		case expectedline != lineNum(fset, pos): // in case it's not
			nbcommentlit = "" // empty it
			expectedline = 0  // and put expectedline back to 0

		case expectedline == lineNum(fset, pos): // in case it is
			nbStart := noteBookMarker + " # from source line " + strconv.Itoa(nbcommentline) + " */"
			currentNoteLine, err := newFilteredNote(nbStart)
			nb.Save(currentNoteLine)
			currentNote, err := newFilteredNote(nbcommentlit)
			if err != nil {
				return nil, fmt.Errorf("FilteredNote: %v", err)
			}
			nb.Save(currentNote) // save it
			expectedline = 0     // and put expectedline back to 0

		}
		// we are only interested in toplevel comments with a noteBookMarker
		switch {
		// in case it is
		case tok == token.COMMENT && topLevelComment(fset, pos) && strings.Contains(lit, noteBookMarker):
			// set nbcommentlit
			nbcommentlit = lit
			nbcommentline = lineNum(fset, pos)
			// split it by lines
			commentlines := strings.Split(nbcommentlit, "\n")
			// set expectedline
			expectedline = lineNum(fset, pos) + len(commentlines) + 1
		default:
			continue
		}

	}
	return nb, nil
}