package main

import (
	"encoding/xml"
	"fmt"
	"io"
	"io/ioutil"
	"mime/quotedprintable"
	"os"
	"strings"
	"time"
)

func complain(s string) {
	fmt.Fprintln(os.Stderr, s)
}

func optExit(err error) {
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(-1)
	}
}

// the vCard RFC says, a single logical line can be "folded" to multiple physical lines,
// so this shit must be done
type UnfoldingReader struct {
	buf []byte
	i   int
	j   int
}

func NewUnfoldingReader(buf []byte) *UnfoldingReader {
	return &UnfoldingReader{buf, 0, 0}
}

func replaceFold(s string) string {
	// Yes, I know and I don't care
	return strings.TrimSpace(strings.ReplaceAll(strings.ReplaceAll(s, "\r\n ", ""), "\r\n\t", ""))
}

func (r *UnfoldingReader) ReadLine() (string, bool) {
	readCR := false
	readCRLF := false
	for r.j = r.i; r.j < len(r.buf); r.j++ {
		if r.buf[r.j] == '\r' {
			readCR = true
		} else if readCR && r.buf[r.j] == '\n' {
			readCRLF = true
		} else if readCRLF && r.buf[r.j] != ' ' && r.buf[r.j] != '\t' {
			break
		} else {
			readCRLF = false
		}
	}
	var s string
	if r.i < len(r.buf) {
		s = replaceFold(string(r.buf[r.i:r.j]))
	} else {
		s = ""
	}
	notEOB := (r.i < len(r.buf))
	r.i = r.j
	return s, notEOB
}

func vCardValue(line string) string {
	start := strings.LastIndex(line, ":")
	end := strings.LastIndex(line, ";")
	if start == -1 {
		return ""
	}
	if end < start {
		end = len(line) - 1
	}
	return line[start+1 : end+1]
}

type Contact struct {
	Name    string
	Numbers NumberSet
}

type ContactSet []Contact

var uniqueID int = 1741

const xmlPreamble = `<?xml version="1.0" encoding="utf-8"?>
<phonebooks>
<phonebook>
<contact><category /><person><realName>AVM Ansage (HD)</realName></person><telephony
nid="1"><number prio="1" type="work" quickdial="99" id="0">500@hd-telefonie.avm.de</number></telephony><services /><setup /><uniqueid>0</uniqueid></contact><contact><category /><person><realName>HD-Musik</realName></person><telephony
nid="1"><number prio="1" type="home" quickdial="97" id="0">200@hd-telefonie.avm.de</number></telephony><services /><setup /><uniqueid>1</uniqueid></contact><contact><category /><person><realName>HD-Sprache</realName></person><telephony
nid="1"><number prio="1" type="home" quickdial="98" id="0">100@hd-telefonie.avm.de</number></telephony><services /><setup /><uniqueid>2</uniqueid></contact>

`

const xmlEnd = `</phonebook>
</phonebooks>
`

func (c ContactSet) ToFritzboxXML() string {
	var s strings.Builder
	s.WriteString(xmlPreamble)
	for _, contact := range c {
		contact.WriteFritzboxXML(&s)
	}
	s.WriteString(xmlEnd)
	return s.String()
}

func (c *Contact) WriteFritzboxXML(s io.Writer) {
	if c == nil {
		return
	}
	uniqueID++
	fmt.Fprint(s, "<contact><category>0</category><person><realName>")
	xml.Escape(s, []byte(c.Name))
	fmt.Fprintf(s, "</realName></person><telephony nid=\"%d\">\n", len(c.Numbers))
	c.Numbers.WriteFritzboxXML(s)
	fmt.Fprintf(s, "</telephony><services /><setup /><uniqueid>%d</uniqueid></contact>\n\n", uniqueID)
}

func (c *Contact) setName(line string) {
	if c == nil {
		c = &Contact{}
	}
	c.Name = vCardValue(line)
	if strings.Count(c.Name, "=") > 1 {
		tmp, err := ioutil.ReadAll(quotedprintable.NewReader(strings.NewReader(c.Name)))
		if err == nil {
			c.Name = string(tmp)
		}
	}
}

func (c *Contact) addNumber(line string) {
	if c == nil {
		c = &Contact{}
	}
	tolower := strings.ToLower(line)
	val := vCardValue(line)
	var n Number
	if strings.Contains(tolower, "cell") {
		n = Number{val, "mobile"}
	} else {
		n = Number{val, "home"}
	}
	c.Numbers = append(c.Numbers, n)
}

func (c *Contact) setValue(line string) {
	if strings.HasPrefix(line, "FN") {
		c.setName(line)
	} else if strings.HasPrefix(line, "TEL") {
		c.addNumber(line)
	}
}

type Number struct {
	Value string
	Kind  string
}

type NumberSet []Number

func (n NumberSet) WriteFritzboxXML(s io.Writer) {
	for i, number := range n {
		number.WriteFritzboxXML(s, i)
	}
}

func (n *Number) WriteFritzboxXML(s io.Writer, i int) {
	if n == nil {
		return
	}
	var prio int
	if i == 0 {
		prio = 1
	} else {
		prio = 0
	}
	fmt.Fprintf(s, `<number type="%s" prio="%d" id="%d">%s</number>`, n.Kind, prio, i, n.Value)
	fmt.Fprint(s, "\n")
}

func GetContacts(buf []byte) (c ContactSet) {
	r := NewUnfoldingReader(buf)
	var current *Contact
	for l, ok := r.ReadLine(); ok; l, ok = r.ReadLine() {
		if l == "BEGIN:VCARD" {
			current = &Contact{}
		} else if l == "END:VCARD" {
			c = append(c, *current)
			current = nil
		} else {
			current.setValue(l)
		}
	}
	if current != nil {
		c = append(c, *current)
	}
	return
}

func main() {
	if len(os.Args) != 2 {
		fmt.Fprintln(os.Stderr, "Usage:", os.Args[0], "VCF-FILE")
		os.Exit(-1)
	}
	b, err := ioutil.ReadFile(os.Args[1])
	optExit(err)
	outfile := os.Args[1] + "." + time.Now().Format("20060102-150405") + ".xml"
	err = ioutil.WriteFile(outfile, []byte(GetContacts(b).ToFritzboxXML()), 0644)
	optExit(err)
	fmt.Println(outfile)
}