tiny tool to extract codeblocks from markdown

defence.go

package main

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

func main() {
	lang := flag.String("lang", "go", "The language tag to grep for.")
	flag.Parse()

	type blockState int

	const (
		findBlock blockState = iota
		inBlock
		skipBlock
	)

	state := findBlock

	s := bufio.NewScanner(os.Stdin)
	for s.Scan() {
		l := s.Text()
		if strings.HasPrefix(l, "```") {
			if state == findBlock && *lang != "" && l[3:] != *lang {
				state = skipBlock
			} else if state == findBlock {
				state = inBlock
			} else {
				state = findBlock
			}
			continue
		}
		if state == inBlock {
			fmt.Println(l)
		}
	}
	if err := s.Err(); err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
}