package aprs

import (
	"errors"
	"strings"
)

var (
	ErrPayloadMarker     = errors.New("aprs: can't find payload marker")
	ErrDestinationMarker = errors.New("aprs: can't find destination marker")
	ErrPathLength        = errors.New("aprs: invalid path length")
)

// Frame represents a single APRS frame.
type Frame struct {
	// Addressing
	Source      Address `json:"source"`
	Destination Address `json:"destination"`
	Path        Path    `json:"path"`

	// Raw payload
	Raw Raw `json:"raw"`

	// Data contained in the raw payload.
	Data Data `json:"data,omitempty"`

	// Data extracted
	Latitude  float64
	Longitude float64
	Altitude  float64
	Symbol    string
	Comment   string
}

func Parse(s string) (*Frame, error) {
	i := strings.IndexByte(s, ':')
	if i == -1 {
		return nil, ErrPayloadMarker
	}

	var (
		route = s[:i]
		frame = &Frame{Raw: Raw(s[i+1:])}
	)
	if i = strings.IndexByte(route, '>'); i == -1 {
		return nil, ErrDestinationMarker
	}
	frame.Source, route = ParseAddress(route[:i]), route[i+1:]

	path := strings.Split(route, ",")
	if len(path) == 0 || len(path) > 9 {
		return nil, ErrPathLength
	}
	frame.Destination = ParseAddress(path[0])
	for i, l := 1, len(path); i < l; i++ {
		addr := ParseAddress(path[i])
		frame.Path = append(frame.Path, addr)
	}

	var err error
	for _, d := range decoders {
		if d.CanDecode(frame) {
			if frame.Data, err = d.Decode(frame); err == nil {
				break
			}
		}
	}

	return frame, nil
}