gg.go

// Go Gestalt
// make a series of pages visualizing the layout of Go code
package main

import (
	"bufio"
	"flag"
	"fmt"
	"os"
	"regexp"
	"strings"

	"github.com/ajstarks/deck/generate"
)

const (
	commentcolor = "lightgray"
	structcolor  = "rgb(0,0,127)"
	packagecolor = "black"
	defcolor     = "gray"
	funcolor     = "rgb(127,0,0)"
	importcolor  = "rgb(0,127,0)"
	tabsize      = 4
)

// vmap maps one range into another
func vmap(value float64, low1 float64, high1 float64, low2 float64, high2 float64) float64 {
	return low2 + (high2-low2)*(value-low1)/(high1-low1)
}

// rematch indicates a match of a regular expression
// errors are considered no match
func rematch(pattern, s string) bool {
	m, err := regexp.MatchString(pattern, s)
	if err != nil {
		return false
	}
	return m
}

// process reads an input file, and generates a series of pages
// showing the structure of the code.
func process(filename string, deck *generate.Deck, maxline int) error {
	r, err := os.Open(filename)
	if err != nil {
		return err
	}
	color := defcolor
	top := 90.0
	bottom := 5.0
	left := 5.0
	right := 20.0
	y := top
	page := 1
	colsize := 25.0
	deck.StartDeck()
	deck.StartSlide()
	deck.Text(left, 95, filename, "sans", 1.5, "")
	deck.TextEnd(95, 95, fmt.Sprintf("Page %d", page), "sans", 1, "")

	scanner := bufio.NewScanner(r)
	var incomment bool
	for scanner.Scan() {
		t := scanner.Text()

		if strings.HasPrefix(t, "/*") {
			incomment = true
		}
		if strings.HasPrefix(t, "*/") {
			incomment = false
		}

		if rematch(".*//", t) || incomment {
			color = commentcolor
		} else if rematch("^package", t) {
			color = packagecolor
		} else if rematch("^func.*{", t) {
			color = funcolor
		} else if rematch("^type.*struct.*{", t) || rematch("^type.*interface.*{", t) {
			color = structcolor
		} else if rematch("^import", t) {
			color = importcolor
		} else {
			color = defcolor
		}

		linelen := len(t)
		ntabs := strings.Count(t, "\t")
		ntlen := linelen - ntabs
		codelen := ntlen + (ntabs * tabsize)
		fmaxline := float64(maxline)

		x := vmap(float64(codelen), 0, fmaxline, left, right)
		tabshift := float64(ntabs)
		deck.Line(left+tabshift, y, x, y, 0.5, color)
		y -= 1.0
		// new column
		if y < bottom {
			y = top
			left += colsize
			right += colsize
		}
		// new page
		if left > 100 {
			top = 90.0
			bottom = 5.0
			left = 5.0
			right = 20.0
			y = top
			page++
			deck.EndSlide()
			deck.StartSlide()
			deck.Text(left, 95, filename, "sans", 1.5, "")
			deck.TextEnd(95, 95, fmt.Sprintf("Page %d", page), "sans", 1, "")
		}
	}
	deck.EndSlide()
	deck.EndDeck()
	r.Close()
	return nil
}

// for every input file, make a deck
func main() {
	linelength := flag.Int("l", 100, "max line length")
	flag.Parse()
	deck := generate.NewSlides(os.Stdout, 0, 0)
	for _, f := range flag.Args() {
		if err := process(f, deck, *linelength); err != nil {
			fmt.Fprintf(os.Stderr, "%v\n", err)
			continue
		}
	}
}