gemtext2gophermap/main.go

package main

import(
	"fmt"
	"os"
	"io"
	"strings"
	"strconv"
	p "github.com/mcecode/gemtext-parser"
)

type State struct {
	out io.Writer
	maxLineLength int
	insertionMap []string
	insertionIndex int
	isInCodeBlock bool
	wasPreviousLink bool
	isWebOnly bool
}

func main() {
	if len(os.Args) < 3 {
		fmt.Printf("Usage: %s input.gmi output_gophermap [max line length (default 70)] [preprocessor insertion map file]\n", os.Args[0])
		return
	}

	var asl p.ASL
	var err error
	if os.Args[1] != "-" {
		asl, err = p.ParseFile(os.Args[1])
		if err != nil {
			fmt.Fprintln(os.Stderr, err)
			return
		}
	} else {
		stdin, err := io.ReadAll(os.Stdin)
		if err != nil {
			fmt.Fprintln(os.Stderr, err)
			return
		}
		asl = p.Parse(string(stdin))
	}

	var outputWriter io.Writer
	if os.Args[2] != "-" {
		file, err := os.Create(os.Args[2])
		if err != nil {
			fmt.Fprintln(os.Stderr, err)
			return
		}
		defer file.Close()
		outputWriter = file
	} else {
		outputWriter = os.Stdout
	}

	preprocessorMap := []string{}
	if len(os.Args) >= 5 {
		data, err := os.ReadFile(os.Args[4])
		if err != nil {
			fmt.Fprintln(os.Stderr, err)
			os.Exit(1)
		}
		preprocessorMap = strings.Split(string(data), "<!--break-->")
	}

	s := State{outputWriter, 70, preprocessorMap, 0, false, false, false}
	if len(os.Args) >= 4 {
		maxLineLength, err := strconv.Atoi(os.Args[3])
		if err != nil {
			fmt.Fprintln(os.Stderr, err)
			return
		}
		s.maxLineLength = maxLineLength
	}

	asl.Visit(s.handleElement)
}

var gopherTypeCharParams = GopherTypeCharParams{
	GophermapFiles: []string{"gophermap"},
	GophermapExtensions: []string{},
	PromptFileExtensions: []string{},
}

func (s *State) handleElement(e p.Element) {
	if strings.HasPrefix(e.Text(), "<!--web-only-->") {
		s.isWebOnly = !s.isWebOnly
		return
	}
	if s.isWebOnly { return }
	if strings.HasPrefix(e.Text(), "<!--insert-gopher-->") {
		s.out.Write([]byte(s.insertionMap[s.insertionIndex]))
		s.insertionIndex += 1
		return
	}

	switch (e.Type()) {
		case p.ElementTypes.Text():
			if e.Text() == "" { return }
			if !s.isInCodeBlock { s.out.Write([]byte("\n")) }
			s.out.Write([]byte(JoinGophermapLines("i", WrapLines(e.Text(), s.maxLineLength, " "), "\t/FAKE\tNULL\t0")))
			s.wasPreviousLink = false
		case p.ElementTypes.Link():
			if !s.wasPreviousLink {
				s.out.Write([]byte("\n"))
			}
			isUrl := strings.Contains(e.URL(), "://")
			linkPrefix := ""
			if isUrl {
				linkPrefix = "URL:"
			}
			typeChar := gopherTypeCharParams.GopherTypeChar(e.URL(), strings.HasSuffix(e.URL(), "/"))
			s.out.Write([]byte(typeChar + e.Text() + "\t" + linkPrefix + e.URL()))
			s.wasPreviousLink = true
		case p.ElementTypes.Heading():
			s.out.Write([]byte("\n"))
			if e.Level() == p.HeadingLevels.Heading() || e.Level() == p.HeadingLevels.SubHeading() {
				s.out.Write([]byte("\n\n"))
			}
			if e.Level() == p.HeadingLevels.SubSubHeading() {
				s.out.Write([]byte("\n"))
			}
			s.out.Write([]byte(JoinGophermapLines("i", WrapLines(e.Text(), s.maxLineLength, " "), "\t/FAKE\tNULL\t0")))
			s.wasPreviousLink = false
		case p.ElementTypes.List():
			s.out.Write([]byte(JoinGophermapLines("i- ", WrapLines(e.Text(), s.maxLineLength - 2, " "), "\t/FAKE\tNULL\t0")))
			s.wasPreviousLink = false
		case p.ElementTypes.Quote():
			s.out.Write([]byte(JoinGophermapLines("i> ", WrapLines(e.Text(), s.maxLineLength - 2, " "), "\t/FAKE\tNULL\t0")))
			s.wasPreviousLink = false
		case p.ElementTypes.PreformatToggle():
			s.isInCodeBlock = !s.isInCodeBlock
			s.wasPreviousLink = false
	}
	if e.Text() != "" {
		s.out.Write([]byte("\n"))
	}
}