package snowluma

import (
	"sort"
	"strings"
)

// ParseCQ 将 CQ 码字符串解析为消息段数组。
// 文本与 [CQ:type,k=v] 混排时会还原为对应的段序列。
func ParseCQ(s string) []Segment {
	var out []Segment
	var text strings.Builder
	flush := func() {
		if text.Len() > 0 {
			out = append(out, Text(unescapeText(text.String())))
			text.Reset()
		}
	}
	for i := 0; i < len(s); {
		if strings.HasPrefix(s[i:], "[CQ:") {
			end := strings.IndexByte(s[i:], ']')
			if end < 0 {
				text.WriteString(s[i:])
				break
			}
			end += i
			flush()
			out = append(out, parseCQBody(s[i+4:end]))
			i = end + 1
			continue
		}
		text.WriteByte(s[i])
		i++
	}
	flush()
	return out
}

func parseCQBody(body string) Segment {
	parts := strings.Split(body, ",")
	seg := Segment{Type: strings.ToLower(strings.TrimSpace(parts[0])), Data: map[string]any{}}
	for _, p := range parts[1:] {
		k, v, ok := strings.Cut(p, "=")
		if !ok {
			continue
		}
		seg.Data[strings.TrimSpace(k)] = unescapeParam(v)
	}
	return seg
}

// EncodeCQ 将消息段数组编码为 CQ 码字符串。
func EncodeCQ(segs []Segment) string {
	var b strings.Builder
	for _, s := range segs {
		if s.Type == "text" {
			b.WriteString(escapeText(strOf(s.Data["text"])))
			continue
		}
		b.WriteString("[CQ:" + s.Type)
		keys := make([]string, 0, len(s.Data))
		for k := range s.Data {
			keys = append(keys, k)
		}
		sort.Strings(keys)
		for _, k := range keys {
			b.WriteString(",")
			b.WriteString(k)
			b.WriteString("=")
			b.WriteString(escapeParam(strOf(s.Data[k])))
		}
		b.WriteString("]")
	}
	return b.String()
}

// String 将单个消息段编码为 CQ 码。
func (s Segment) String() string { return EncodeCQ([]Segment{s}) }

func escapeText(s string) string {
	r := strings.NewReplacer("&", "&#38;", "[", "&#91;", "]", "&#93;")
	return r.Replace(s)
}

func escapeParam(s string) string {
	r := strings.NewReplacer("&", "&#38;", "[", "&#91;", "]", "&#93;", ",", "&#44;")
	return r.Replace(s)
}

func unescapeText(s string) string {
	r := strings.NewReplacer("&#91;", "[", "&#93;", "]", "&#38;", "&")
	return r.Replace(s)
}

func unescapeParam(s string) string {
	r := strings.NewReplacer("&#44;", ",", "&#91;", "[", "&#93;", "]", "&#38;", "&")
	return r.Replace(s)
}