package metar

import (
	"context"
	"encoding/xml"
	"errors"
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"time"
)

type Client struct {
	hc http.Client
}

const (
	MostRecentConstraint = "constraint"
	MostRecentPostFilter = "postfilter"
	MostRecentTrue       = "true"
)

type Response struct {
	RequestIndex int `xml:"request_index"`
	DataSource   struct {
		Name string `xml:"name,attr"`
	} `xml:"data_source"`
	Request struct {
		Type string `xml:"type,attr"`
	} `xml:"request"`
	Errors      []string `xml:"errors>error"`
	Warnings    []string `xml:"warnings>warning"`
	TimeTakenMs int      `xml:"time_taken_ms"`
	Data        struct {
		NumResults int     `xml:"num_results,attr"`
		METARs     []METAR `xml:"METAR"`
	} `xml:"data"`
}

type METAR struct {
	RawText             string  `xml:"raw_text"`
	StationID           string  `xml:"station_id"`
	ObservationTime     string  `xml:"observation_time"`
	Latitude            float32 `xml:"latitude"`
	Longitude           float32 `xml:"longitude"`
	TempC               float32 `xml:"temp_c"`
	DewpointC           float32 `xml:"dewpoint_c"`
	WindDirDegrees      int     `xml:"wind_dir_degress"`
	WindSpeedKt         int     `xml:"wind_speed_kt"`
	WindGustKt          int     `xml:"wind_gust_kt"`
	VisibilityStatuteMi float32 `xml:"visibility_statute_mi"`
	AltimInHg           float32 `xml:"altim_in_hg"`
	SeaLevelPressureMb  float32 `xml:"sea_level_pressure_mb"`
	QualityControlFlags struct {
		Corrected               string `xml:"corrected"`
		Auto                    string `xml:"auto"`
		AutoStation             string `xml:"auto_station"`
		MaintenanceIndicatorOn  string `xml:"maintenance_indicator_on"`
		NoSignal                string `xml:"no_signal"`
		LightningSensorOff      string `xml:"lightning_sensor_off"`
		FreezingRainSensorOff   string `xml:"freezing_rain_sensor_off"`
		PresentWeatherSensorOff string `xml:"present_weather_sensor_off"`
	} `xml:"quality_control_flags"`
	WxString                  string         `xml:"wx_string"`
	SkyConditions             []SkyCondition `xml:"sky_condition"`
	FlightCategory            string         `xml:"flight_category"`
	ThreeHrPressureTendencyMb float32        `xml:"three_hr_pressure_tendency_mb"`
	MaxTC                     float32        `xml:"maxT_c"`
	MinTC                     float32        `xml:"minT_c"`
	MaxT24HrC                 float32        `xml:"maxT24hr_c"`
	MinT24HrC                 float32        `xml:"minT24hr_c"`
	PrecipIn                  float32        `xml:"precip_in"`
	Pcp3HrIn                  float32        `xml:"pcp3hr_in"`
	Pcp6HrIn                  float32        `xml:"pcp6hr_in"`
	Pcp24HrIn                 float32        `xml:"pcp24hr_in"`
	SnowIn                    float32        `xml:"snow_in"`
	VertVisFt                 int            `xml:"vert_vis_ft"`
	METARType                 string         `xml:"metar_type"`
	ElevationM                float32        `xml:"elevation_m"`
}

type SkyCondition struct {
	SkyCover       string `xml:"sky_cover,attr"`
	CloudBaseFtAGL int    `xml:"cloud_base_ft_agl,attr"`
}

type Request struct {
	v url.Values
}

type requestArg func(*Request)

func NewRequest(args ...requestArg) *Request {
	var r Request
	for _, arg := range args {
		arg(&r)
	}
	return &r
}

func StationString(s string) requestArg {
	return func(r *Request) {
		r.v.Add("stationString", s)
	}
}

func TimeRange(from, to time.Time) requestArg {
	return func(r *Request) {
		r.v.Add("startTime", string(from.Unix()))
		r.v.Add("endTime", string(to.Unix()))
	}
}

func HoursBeforeNow(h float64) requestArg {
	return func(r *Request) {
		r.v.Add("hoursBeforeNow", strconv.FormatFloat(h, 'f', 64, -1))
	}
}

func MostRecent(mr bool) requestArg {
	return func(r *Request) {
		r.v.Add("mostRecent", strconv.FormatBool(mr))
	}
}

func MostRecentForEachStation(s string) requestArg {
	return func(r *Request) {
		r.v.Add("mostRecentForEachStation", s)
	}
}

func LatLongRect(minLat, minLon, maxLat, maxLon float64) requestArg {
	return func(r *Request) {
		r.v.Add("minLat", strconv.FormatFloat(minLat, 'f', 64, -1))
		r.v.Add("minLon", strconv.FormatFloat(minLon, 'f', 64, -1))
		r.v.Add("maxLat", strconv.FormatFloat(maxLat, 'f', 64, -1))
		r.v.Add("maxLon", strconv.FormatFloat(maxLon, 'f', 64, -1))
	}
}

func RadialDistance(s string) requestArg {
	return func(r *Request) {
		r.v.Add("radialDistance", s)
	}
}

func FlightPath(s string) requestArg {
	return func(r *Request) {
		r.v.Add("flightPath", s)
	}
}

func MinDegreeDistance(d float64) requestArg {
	return func(r *Request) {
		r.v.Add("minDegreeDistance", strconv.FormatFloat(d, 'f', 64, -1))
	}
}

func Fields(ss ...string) requestArg {
	return func(r *Request) {
		r.v.Add("fields", strings.Join(ss, ","))
	}
}

func requestToQueryString(m *Request) string {
	m.v.Add("dataSource", "metars")
	m.v.Add("requestType", "retrieve")
	m.v.Add("format", "xml")
	return m.v.Encode()
}

func (c *Client) GetMETARs(ctx context.Context, req *Request) (*Response, error) {
	u := url.URL{
		Scheme:   "https",
		Host:     "www.aviationweather.gov",
		Path:     "/adds/dataserver_current/httpparam",
		RawQuery: requestToQueryString(req),
	}
	hr, err := http.NewRequestWithContext(ctx, "GET", u.String(), nil)
	if err != nil {
		return nil, err
	}
	hr.Header.Add("user-agent", "wxbot/1.0 +bnbl.io/wx")
	resp, err := c.hc.Do(hr)
	if err != nil {
		return nil, err
	}
	if resp.StatusCode != http.StatusOK {
		return nil, errors.New(resp.Status)
	}
	defer resp.Body.Close()
	var r Response
	if err := xml.NewDecoder(resp.Body).Decode(&r); err != nil {
		return nil, err
	}
	return &r, nil
}