package aprs

import (
	"fmt"
	"regexp"
	"strconv"
	"time"
)

type decoder interface {
	CanDecode(*Frame) bool
	Decode(*Frame) (Data, error)
}

var decoders []decoder

func init() {
	decoders = []decoder{
		positionDecoder{},
		micEDecoder{},
		messageDecoder{},
		queryDecoder{},
	}
}

// Raw is the string encoded raw frame payload.
type Raw string

func (p Raw) Type() Type {
	var t Type
	if len(p) > 0 {
		t = Type(p[0])
	}
	return t
}

// Data represents a decoded payload data.
type Data interface {
	String() string
}

// Type of payload.
type Type byte

var typeName = map[Type]string{
	0x1c: "Current Mic-E Data (Rev 0 beta)",
	0x1d: "Old Mic-E Data (Rev 0 beta)",
	'!':  "Position without timestamp (no APRS messaging), or Ultimeter 2000 WX Station",
	'#':  "Peet Bros U-II Weather Station",
	'$':  "Raw GPS data or Ultimeter 2000",
	'%':  "Agrelo DFJr / MicroFinder",
	'"':  "Old Mic-E Data (but Current data for TM-D700)",
	')':  "Item",
	'*':  "Peet Bros U-II Weather Station",
	',':  "Invalid data or test data",
	'/':  "Position with timestamp (no APRS messaging)",
	':':  "Message",
	';':  "Object",
	'<':  "Station Capabilities",
	'=':  "Position without timestamp (with APRS messaging)",
	'>':  "Status",
	'?':  "Query",
	'@':  "Position with timestamp (with APRS messaging)",
	'T':  "Telemetry data",
	'[':  "Maidenhead grid locator beacon (obsolete)",
	'_':  "Weather Report (without position)",
	'`':  "Current Mic-E Data (not used in TM-D700)",
	'{':  "User-Defined APRS packet format",
	'}':  "Third-party traffic",
}

func (t Type) String() string {
	if s, ok := typeName[t]; ok {
		return s
	}
	return fmt.Sprintf("unknown %02x", byte(t))
}

func (t Type) IsMessage() bool {
	return t == ':'
}

func (t Type) IsThirdParty() bool {
	return t == '}'
}

var matchTimestamp = regexp.MustCompile(`^[0-9]{6}[zh/]`)

func hasTimestamp(s string) bool {
	return matchTimestamp.MatchString(s)
}

func parseTimestamp(s string) (t time.Time, comment string, err error) {
	// log.Printf("parse timestamp %q", s)
	var hh, mm, ss int
	if hh, err = strconv.Atoi(s[0:2]); err != nil {
		return
	}
	if mm, err = strconv.Atoi(s[2:4]); err != nil {
		return
	}
	if ss, err = strconv.Atoi(s[4:6]); err != nil {
		return
	}

	now := time.Now()
	switch s[6] {
	case 'z': // DDHHMMz zulu time
		now = now.UTC()
		return time.Date(now.Year(), now.Month(), hh, mm, ss, 0, 0, time.UTC), s[7:], nil
	case '/': // DDHHMM/ local time
		return time.Date(now.Year(), now.Month(), hh, mm, ss, 0, 0, now.Location()), s[7:], nil
	case 'h': // HHMMSSh zulu time
		now = now.UTC()
		return time.Date(now.Year(), now.Month(), now.Day(), hh, mm, ss, 0, time.UTC), s[7:], nil
	default:
		return time.Time{}, "", fmt.Errorf("aprs: invalid/unknown timestamp marker %q", s[6])
	}
}