package streams

import (
	"fmt"
	"sort"
	"strings"
	"unicode"
)

func quote(text string) string {
	text = strings.Replace(text, "\\", "\\\\", -1)
	text = strings.Replace(text, "'", "\\'", -1)
	text = "'" + text + "'"
	return text
}

func unquote(text string) string {
	if strings.HasPrefix(text, "'") && strings.HasSuffix(text, "'") {
		text = text[1 : len(text)-1]
		text = strings.Replace(text, "\\'", "'", -1)
		text = strings.Replace(text, "\\\\", "\\", -1)
	}
	return text
}

type Metadata map[string]string

func (meta Metadata) sortedKeys() []string {
	keys := make([]string, len(meta))
	i := 0
	for key, _ := range meta {
		keys[i] = key
		i++
	}
	sort.Strings(keys)
	return keys
}

func decodeMetadataItem(text string, metadata *Metadata) (err error) {
	parts := strings.SplitN(text, "=", 2)
	if len(parts) < 2 {
		err = fmt.Errorf("expected key=value but only got key (in %q)", text)
		return
	}

	parts[1] = unquote(parts[1])
	(*metadata)[parts[0]] = parts[1]

	return
}

func DecodeMetadata(source string) (meta Metadata, err error) {
	// name='value'; name='value';name='value';
	meta = make(Metadata)

	escape := false
	quoted := false
	fieldsFunc := func(c rune) (retval bool) {
		retval = false
		if escape {
			escape = false
		} else {
			switch {
			case unicode.IsSpace(c) && !quoted:
				retval = true
				return
			case c == '\'':
				quoted = !quoted
			case c == '\\' && quoted:
				escape = true
			case c == ';' && !quoted:
				retval = true
				return
			}
		}
		return
	}

	for _, field := range strings.FieldsFunc(source, fieldsFunc) {
		if len(field) == 0 {
			continue
		}
		if err = decodeMetadataItem(field, &meta); err != nil {
			return
		}
	}

	return
}

func (meta Metadata) String() string {
	mstr := ""

	if meta != nil {
		for _, key := range meta.sortedKeys() {
			value := meta[key]
			mstr += fmt.Sprintf("%s=%s;", key, quote(value))
		}
	}

	return mstr
}

func (meta Metadata) Bytes() (buf []byte) {
	return []byte(meta.String())
}