km2md.go

package main

import (
	"encoding/json"
	"flag"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"strings"
)

type KmSize struct {
	Width  int `json:"width"`
	Height int `json:"height"`
}

type KmData struct {
	Id          string `json:"id"`
	Created     int64  `json:"created"`
	Text        string `json:"text"`
	Note        string `json:"note"`
	Image       string `json:"image"`
	ImageSize   KmSize `json:"imageSize"`
	ImageTitle  string `json:"imageTitle"`
	ExpandState string `json:"expandState"`
}

type KmNode struct {
	Data     KmData   `json:"data"`
	Children []KmNode `json:"children"`
}

type KmDoc struct {
	Root KmNode `json:"root"`
}

func loadKmDoc(path string) (*KmDoc, error) {
	data, err := ioutil.ReadFile(path)
	if err != nil {
		return nil, err
	}

	var doc KmDoc
	err = json.Unmarshal(data, &doc)
	if err != nil {
		return nil, err
	}

	return &doc, nil
}

func nodeToMarkdown(out io.Writer, node *KmNode, level int) error {
	if len(node.Children) == 0 || level > 4 {
		fmt.Fprintf(out, "%s\n\n", node.Data.Text)
	} else {
		title := node.Data.Text
		if title == "" {
			title = node.Data.Id
		}
		fmt.Fprintf(out, "%s %s\n\n", strings.Repeat("#", level), title)
	}
	if node.Data.Image != "" {
		fmt.Fprintf(out, "![%s](%s)\n\n", node.Data.ImageTitle, node.Data.Image)
	}
	if node.Data.Note != "" {
		fmt.Fprintf(out, "%s\n\n", node.Data.Note)
	}

	for _, child := range node.Children {
		if err := nodeToMarkdown(out, &child, level+1); err != nil {
			return err
		}
	}
	return nil
}

func convertMarkdown(doc *KmDoc, out io.Writer) error {
	fmt.Fprintf(out, "# %s\n\n", doc.Root.Data.Text)
	fmt.Fprintf(out, "---\n\n")
	for _, node := range doc.Root.Children {
		if err := nodeToMarkdown(out, &node, 1); err != nil {
			return err
		}
	}
	return nil
}

func main() {
	var (
		infile  string
		outfile string
	)
	flag.StringVar(&infile, "i", "in.km", "input file")
	flag.StringVar(&outfile, "o", "out.md", "output file")
	flag.Parse()

	doc, err := loadKmDoc(infile)
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}

	var out io.Writer
	if outfile == "-" {
		out = os.Stdout
	} else {
		f, err := os.Create(outfile)
		if err != nil {
			fmt.Fprintln(os.Stderr, err)
			os.Exit(1)
		}
		defer f.Close()
		out = f
	}
	err = convertMarkdown(doc, out)
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
}