package gtp

import (
	"errors"
	"fmt"
	"git.noahlan.cn/noahlan/ntool/nbyte"
	"git.noahlan.cn/noahlan/ntool/nstr"
	"regexp"
	"strings"
)

var (
	TabRegex = regexp.MustCompile(`\t`)
	IdRegex  = regexp.MustCompile(`\s`)
)

type GTPSerializer struct {
	contentBuf strings.Builder
	firstLine  bool
	//
	lastResp *GTPResponse
}

func NewGTPSerializer() *GTPSerializer {
	ret := &GTPSerializer{
		contentBuf: strings.Builder{},
	}
	ret.reset()

	return ret
}

func (s *GTPSerializer) Marshal(v any) ([]byte, error) {
	ret, ok := v.(*GTPCommand)
	if !ok {
		return nil, errors.New(fmt.Sprintf("参数类型必须为 %T", GTPCommand{}))
	}
	// ret arg0 arg1 arg2 ...
	// Cmd arg0 arg1 arg2 ...
	sb := strings.Builder{}
	if ret.ID != "" {
		sb.WriteString(ret.ID)
		sb.WriteString(" ")
	}
	sb.WriteString(ret.Cmd)
	sb.WriteString(" ")
	sb.WriteString(strings.Join(ret.Args, " "))
	return []byte(sb.String()), nil
}

func (s *GTPSerializer) reset() {
	s.contentBuf.Reset()
	s.firstLine = true
	s.lastResp = nil
}

func (s *GTPSerializer) Unmarshal(line string) (*GTPResponse, bool) {
	// replace \t and trimSpace
	line = strings.TrimSpace(TabRegex.ReplaceAllString(line, " "))
	// 是否第一行
	s.firstLine = nstr.ContainsOne(line, []string{"=", "?"})

	if len(line) == 0 {
		defer s.reset()

		if s.firstLine {
			s.lastResp = &GTPResponse{
				ID:      "",
				Content: s.contentBuf.String(),
				Err:     errors.New("unknown"),
			}
			return s.lastResp, true
		} else {
			// end line
			content := s.contentBuf.String()

			// remove last '\n'
			cLen := len(content)
			if cLen > 0 && content[cLen-1] == '\n' {
				content = content[:cLen-1]
			}

			if s.lastResp.Err == nil {
				s.lastResp.Content = content
			} else {
				s.lastResp.Err = errors.New(content)
			}

			return s.lastResp, true
		}
	}

	if s.firstLine {
		s.lastResp = &GTPResponse{}

		// 第一行，处理 err, id 等内容
		hasErr := line[0] == '?'
		hasId := len(line) >= 2 && nbyte.IsDigit(line[1])
		line = line[1:]

		if hasId {
			s.lastResp.ID = IdRegex.Split(line, -1)[0]
			line = line[len(s.lastResp.ID):]
		}
		if hasErr {
			s.lastResp.Err = errors.New("接收GTP错误消息")
		}
	}
	// 填充内容直至末尾行
	s.contentBuf.WriteString(strings.TrimSpace(line))
	s.contentBuf.WriteByte('\n')

	return nil, false
}