package main

import (
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"path/filepath"
	"regexp"
	"strings"
)

type link struct {
	full  string
	title string
	url   string
}

func procAudio(fileContent string, audioRegex *regexp.Regexp) string {
	audios := audioRegex.FindAllStringSubmatch(fileContent, -1)

	if audios != nil {
		for i := range audios {
			full := audios[i][0]
			url := audios[i][1]
			link := link{full, "audio", url}

			replacement := fmt.Sprintf("=> %s", link.url)
			fileContent = strings.Replace(fileContent, link.full, replacement, 1)
		}
	}

	return fileContent
}

func procVideos(fileContent string, videoRegex *regexp.Regexp) string {
	videos := videoRegex.FindAllStringSubmatch(fileContent, -1)

	if videos != nil {
		for i := range videos {
			full := videos[i][0]
			url := videos[i][1]
			url = fmt.Sprintf("%s.webm", url)
			link := link{full, "video", url}

			replacement := fmt.Sprintf("=> %s", link.url)
			fileContent = strings.Replace(fileContent, link.full, replacement, 1)
		}
	}

	return fileContent
}

func procImages(fileContent string, imgRegex *regexp.Regexp) string {
	images := imgRegex.FindAllStringSubmatch(fileContent, -1)

	if images != nil {
		for i := range images {
			full := images[i][1]
			title := images[i][2]
			url := images[i][3]
			urlParts := strings.Split(url, " ")
			link := link{full, title, urlParts[0]}

			replacement := fmt.Sprintf("%s\n=> %s", link.title, link.url)
			fileContent = strings.Replace(fileContent, link.full, replacement, 1)
		}
	}

	return fileContent
}

func procLinks(fileContent string, linkRegex *regexp.Regexp) string {
	links := linkRegex.FindAllStringSubmatch(fileContent, -1)
	linkUrls := make([]link, len(links))

	if links != nil {
		for i := range links {
			full := links[i][1]
			title := links[i][2]
			url := links[i][3]
			link := link{full, title, url}

			replacement := fmt.Sprintf("*%s*", link.title)
			fileContent = strings.Replace(fileContent, link.full, replacement, 1)

			linkUrls[i] = link
		}
	}

	var sb strings.Builder
	for _, link := range linkUrls {
		fmtLink := fmt.Sprintf("=> %s %s\n", link.url, link.title)
		sb.WriteString(fmtLink)
	}
	fmtLinks := sb.String()
	fileContent += fmt.Sprintf("\n%s", fmtLinks)

	return fileContent
}

func procFile(src string, linkRegex *regexp.Regexp, imgRegex *regexp.Regexp, videoRegex *regexp.Regexp, audioRegex *regexp.Regexp) (string, error) {
	fileData, err := ioutil.ReadFile(src)
	if err != nil {
		return "", err
	}

	fileContent := string(fileData)
	fileContent = procLinks(fileContent, linkRegex)
	fileContent = procImages(fileContent, imgRegex)
	fileContent = procVideos(fileContent, videoRegex)
	fileContent = procAudio(fileContent, audioRegex)

	return fileContent, nil
}

func procFiles(srcDir string, destDir string) error {
	libRegex := regexp.MustCompile("^.+\\.(md)$")
	linkRegex := regexp.MustCompile("[^!](\\[(.+?)\\]\\((.+?)\\))")
	imgRegex := regexp.MustCompile("([!]\\[(.+?)\\]\\((.+?)\\))")
	videoRegex := regexp.MustCompile("{{< video src=\"(.*)\" >}}")
	audioRegex := regexp.MustCompile("{{< audio src=\"(.*)\" >}}")

	srcDir, err := filepath.Abs(srcDir)
	if err != nil {
		return err
	}

	destDir, err = filepath.Abs(destDir)
	if err != nil {
		return err
	}

	err = filepath.Walk(srcDir, func(path string, info os.FileInfo, err error) error {
		if err == nil && libRegex.MatchString(info.Name()) {
			processedFile, err := procFile(path, linkRegex, imgRegex, videoRegex, audioRegex)
			if err != nil {
				return err
			}

			path, err = filepath.Abs(path)
			if err != nil {
				return err
			}

			srcFile := strings.Replace(path, srcDir, "", 1)
			destFile := filepath.Join(destDir, srcFile)
			destDir := filepath.Dir(destFile)

			err = os.MkdirAll(destDir, os.ModePerm)
			if err != nil {
				return err
			}

			err = ioutil.WriteFile(destFile, []byte(processedFile), 0644)
			if err != nil {
				return err
			}
			log.Printf("processed %s", path)
		}
		return nil
	})

	return err
}

func main() {
	if len(os.Args) < 2 {
		log.Fatal("no source directory specified")
		os.Exit(1)
	}

	if len(os.Args) < 3 {
		log.Fatal("no dest directory specified")
		os.Exit(1)
	}

	srcDir := os.Args[1]
	srcInfo, err := os.Stat(srcDir)
	if os.IsNotExist(err) {
		log.Fatalf("source directory %s does not exist", srcDir)
		os.Exit(1)
	}

	if !srcInfo.IsDir() {
		log.Fatalf("%s is not a directory", srcDir)
		os.Exit(1)
	}

	destDir := os.Args[2]

	err = procFiles(srcDir, destDir)
	if err != nil {
		log.Fatal(err)
		os.Exit(1)
	}
}