package aprs

import (
	"fmt"
	"strconv"
	"strings"
)

type Message struct {
	ID            int    `json::"id"`
	IsAcknowledge bool   `json:"is_ack"`
	IsRejection   bool   `json:"is_rejection"`
	IsBulletin    bool   `json:"is_bulletin"`
	Recipient     string `json:"recipient"`
	AnnoucementID byte   `json:"announcement_id,omitempty"`
	Group         string `json:"group,omitempty"`
	Severity      string `json:"severity,omitempty"`
	Text          string `json:"text"`
}

func (msg *Message) String() string {
	return fmt.Sprintf("%s: %q", msg.Recipient, msg.Text)
}

type messageDecoder struct{}

func (messageDecoder) CanDecode(frame *Frame) bool {
	var (
		maybeMessage  = len(frame.Raw) >= 11 && frame.Raw[10] == ':'
		maybeBulletin = len(frame.Raw) >= 10 && frame.Raw[9] == ':'
	)
	return frame.Raw.Type() == ':' && (maybeMessage || maybeBulletin)
}

func (messageDecoder) Decode(frame *Frame) (data Data, err error) {
	var (
		msg  = new(Message)
		text string
		size = len(text)
	)
	if len(frame.Raw) >= 10 && frame.Raw[9] == ':' {
		msg.Recipient, text = strings.TrimSpace(string(frame.Raw[1:9])), string(frame.Raw[9:])
	} else {
		msg.Recipient, text = strings.TrimSpace(string(frame.Raw[1:10])), string(frame.Raw[10:])
	}

	switch {
	case strings.HasPrefix(msg.Recipient, "BLN"):
		// Bulletin
		kind := msg.Recipient[3:]
		if id, err := strconv.Atoi(kind); err == nil {
			// General bulletin
			msg.IsBulletin = true
			msg.ID = id
		} else if len(kind) >= 2 && isDigit(kind[0]) {
			// Group Bulletin Format
			msg.IsBulletin = true
			msg.ID = int(kind[0] - '0')
			msg.Group = kind[1:]
		} else if len(kind) == 1 {
			// Announcement
			msg.IsBulletin = true
			msg.AnnoucementID = kind[0]
		}

	case strings.HasPrefix(msg.Recipient, "NWS-"):
		// National Weather Service Bulletins
		msg.IsBulletin = true
		msg.Severity = msg.Recipient[4:]

	default:
		if i := strings.LastIndexByte(text, '{'); i != -1 && i > (size-6) {
			// Plain message ID: {XXXXX (where there are 1-5 X)
			msg.ID, _ = strconv.Atoi(text[i+1:])
			text = text[:i]
		}

		if i := strings.LastIndex(text, ":ack"); i != -1 && i > (size-9) {
			// Message acknowledgement: :ackXXXXX (where there are 1-5 X)
			msg.IsAcknowledge = true
			msg.ID, _ = strconv.Atoi(text[i+4:])
			text = text[:i]
		}

		if i := strings.LastIndex(text, ":rej"); i != -1 && i > (size-9) {
			// Message acknowledgement: :rejXXXXX (where there are 1-5 X)
			msg.IsRejection = true
			msg.ID, _ = strconv.Atoi(text[i+4:])
			text = text[:i]
		}
	}

	if len(text) > 0 && text[0] == ':' {
		text = text[1:]
	}

	msg.Text = text
	return msg, nil
}