package main

import (
	_ "embed"
	"flag"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"regexp"
	"strings"
)

func _main(o opts) error {
	t, err := ioutil.ReadAll(o.In)
	if err != nil {
		return fmt.Errorf("could not read from stdin: %w", err)
	}

	// TODO replace imgs

	linkRE := regexp.MustCompile(`\(LINK ([^ ]+?) (.+?)\)`)
	linkMatches := linkRE.FindAllSubmatch(t, -1)

	imgRE := regexp.MustCompile(`\(IMG ([^ ]+?) (.+?)\)`)
	imgMatches := imgRE.FindAllSubmatch(t, -1)

	if linkMatches == nil && imgMatches == nil {
		fmt.Fprintf(o.Out, string(t))
		return nil
	}

	output := string(t)
	footer := ""

	linkIx := 0

	for ix, lm := range linkMatches {
		linkIx = ix
		rawLink := string(lm[0])
		link := string(lm[1])
		title := string(lm[2])
		switch o.Mode {
		case "html":
			output = strings.ReplaceAll(output, rawLink,
				fmt.Sprintf("<a href=\"%s\">%s</a>", link, title))
		case "gopher":
			output = strings.ReplaceAll(output, rawLink, fmt.Sprintf("%s[%d]", title, ix))
			linkType := "i"
			if strings.HasPrefix(link, "http") {
				linkType = "h"
			}
			footer += fmt.Sprintf("%s[%d]: %s	%s\n", linkType, ix, title, link)
		case "gemini":
			output = strings.ReplaceAll(output, rawLink, fmt.Sprintf("%s[%d]", title, ix))
			footer += fmt.Sprintf("=> %s [%d]: %s\n", link, ix, title)
		}
	}

	for ix, im := range imgMatches {
		linkIx += ix
		rawImg := string(im[0])
		src := string(im[1])
		alt := string(im[2])
		switch o.Mode {
		case "html":
			output = strings.ReplaceAll(output, rawImg,
				fmt.Sprintf("<img src=\"%s\" alt=\"%s\"/>", src, alt))
		case "gopher":
			output = strings.ReplaceAll(output, rawImg, fmt.Sprintf("%s[%d]", alt, linkIx))
			linkType := "p"
			footer += fmt.Sprintf("%s[%d]: %s	%s\n", linkType, linkIx, alt, src)
		case "gemini":
			output = strings.ReplaceAll(output, rawImg, fmt.Sprintf("%s[%d]", alt, linkIx))
			footer += fmt.Sprintf("=> %s [%d]: %s\n", src, linkIx, alt)
		}
	}

	if footer != "" {
		output = output + "\n\n" + footer
	}

	fmt.Fprintf(o.Out, output)

	return nil
}

type opts struct {
	In   io.Reader
	Out  io.Writer
	Mode string
}

func main() {
	var modeFlag = flag.String("mode", "", "one of html, gopher, gemini.")
	flag.Parse()
	if *modeFlag == "" || (*modeFlag != "html" && *modeFlag != "gopher" && *modeFlag != "gemini") {
		fmt.Fprintln(os.Stderr, "--mode must be specified and one of: html, gopher, gemini")
		os.Exit(1)
	}
	o := opts{
		In:   os.Stdin,
		Out:  os.Stdout,
		Mode: *modeFlag,
	}
	if err := _main(o); err != nil {
		fmt.Fprintln(os.Stderr, err.Error())
		os.Exit(2)
	}
}