package openweather

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"net/url"
	"strings"
	"time"

	"gitea.maximumdirect.net/ejr/feedkit/config"
	"gitea.maximumdirect.net/ejr/feedkit/event"
	"gitea.maximumdirect.net/ejr/weatherfeeder/internal/model"
	"gitea.maximumdirect.net/ejr/weatherfeeder/internal/standards"
)

// ObservationSource polls the OpenWeatherMap "Current weather" endpoint and emits one Observation event.
//
// Typical URL shape (you provide this via config):
//
//	https://api.openweathermap.org/data/2.5/weather?lat=...&lon=...&appid=...&units=metric
//
// Unit notes:
// - If `units` is omitted, OpenWeather uses "standard" units (temp Kelvin, wind m/s).
// - `units=metric` => temp Celsius, wind m/s.
// - `units=imperial` => temp Fahrenheit, wind mph.
//
// weatherd normalizes to:
// - TemperatureC in °C
// - WindSpeedKmh in km/h
// - Pressure in Pa (OpenWeather provides hPa)
type ObservationSource struct {
	name      string
	url       string
	userAgent string
	client    *http.Client
}

func NewObservationSource(cfg config.SourceConfig) (*ObservationSource, error) {
	if strings.TrimSpace(cfg.Name) == "" {
		return nil, fmt.Errorf("openweather_observation: name is required")
	}
	if cfg.Params == nil {
		return nil, fmt.Errorf("openweather_observation %q: params are required (need params.url)", cfg.Name)
	}

	// Driver-specific settings live under cfg.Params to keep feedkit domain-agnostic.
	url, ok := cfg.ParamString("url", "URL")
	if !ok {
		return nil, fmt.Errorf("openweather_observation %q: params.url is required", cfg.Name)
	}

	// Optional User-Agent.
	ua := cfg.ParamStringDefault("weatherfeeder (openweather client)", "user_agent", "userAgent")

	return &ObservationSource{
		name:      cfg.Name,
		url:       url,
		userAgent: ua,
		client: &http.Client{
			Timeout: 10 * time.Second,
		},
	}, nil
}

func (s *ObservationSource) Name() string { return s.name }

// Kind is used for routing/policy.
func (s *ObservationSource) Kind() event.Kind { return event.Kind("observation") }

func (s *ObservationSource) Poll(ctx context.Context) ([]event.Event, error) {
	obs, eventID, err := s.fetchAndParse(ctx)
	if err != nil {
		return nil, err
	}

	// EffectiveAt is optional. If we have a real observation timestamp, use it.
	// We intentionally take a copy so the pointer is stable and not tied to a struct field.
	var effectiveAt *time.Time
	if !obs.Timestamp.IsZero() {
		t := obs.Timestamp
		effectiveAt = &t
	}

	e := event.Event{
		ID:          eventID,
		Kind:        s.Kind(),
		Source:      s.name,
		EmittedAt:   time.Now().UTC(),
		EffectiveAt: effectiveAt,

		Schema:  "weather.observation.v1",
		Payload: obs,
	}

	if err := e.Validate(); err != nil {
		return nil, err
	}

	return []event.Event{e}, nil
}

// --- OpenWeather JSON parsing (minimal subset) ---

type owmResponse struct {
	Coord struct {
		Lon float64 `json:"lon"`
		Lat float64 `json:"lat"`
	} `json:"coord"`

	Weather []struct {
		ID          int    `json:"id"`
		Main        string `json:"main"`
		Description string `json:"description"`
		Icon        string `json:"icon"` // e.g. "04d" or "01n"
	} `json:"weather"`

	Main struct {
		Temp     float64  `json:"temp"`
		Pressure float64  `json:"pressure"`  // hPa
		Humidity float64  `json:"humidity"`  // %
		SeaLevel *float64 `json:"sea_level"` // hPa (optional)
	} `json:"main"`

	Visibility *float64 `json:"visibility"` // meters (optional)

	Wind struct {
		Speed float64  `json:"speed"` // units depend on `units=...`
		Deg   *float64 `json:"deg"`
		Gust  *float64 `json:"gust"` // units depend on `units=...`
	} `json:"wind"`

	Clouds struct {
		All *float64 `json:"all"` // cloudiness %
	} `json:"clouds"`

	Dt int64 `json:"dt"` // unix seconds, UTC

	Sys struct {
		Country string `json:"country"`
		Sunrise int64  `json:"sunrise"` // unix, UTC
		Sunset  int64  `json:"sunset"`  // unix, UTC
	} `json:"sys"`

	Timezone int    `json:"timezone"` // seconds offset from UTC
	ID       int64  `json:"id"`       // city id
	Name     string `json:"name"`     // city name
	Cod      int    `json:"cod"`
}

func (s *ObservationSource) fetchAndParse(ctx context.Context) (model.WeatherObservation, string, error) {
	req, err := http.NewRequestWithContext(ctx, "GET", s.url, nil)
	if err != nil {
		return model.WeatherObservation{}, "", err
	}

	req.Header.Set("User-Agent", s.userAgent)
	req.Header.Set("Accept", "application/json")

	res, err := s.client.Do(req)
	if err != nil {
		return model.WeatherObservation{}, "", err
	}
	defer res.Body.Close()

	if res.StatusCode < 200 || res.StatusCode >= 300 {
		return model.WeatherObservation{}, "", fmt.Errorf("openweather_observation %q: HTTP %s", s.name, res.Status)
	}

	var parsed owmResponse
	if err := json.NewDecoder(res.Body).Decode(&parsed); err != nil {
		return model.WeatherObservation{}, "", err
	}

	// Timestamp: dt is unix seconds, UTC.
	ts := time.Unix(parsed.Dt, 0).UTC()

	// Primary weather condition: OpenWeather returns a list; we treat [0] as primary.
	// If missing, we degrade gracefully.
	owmID := 0
	rawDesc := ""
	icon := ""
	if len(parsed.Weather) > 0 {
		owmID = parsed.Weather[0].ID
		rawDesc = strings.TrimSpace(parsed.Weather[0].Description)
		icon = strings.TrimSpace(parsed.Weather[0].Icon)
	}

	// Day/night inference:
	// - Prefer icon suffix if present ("d" or "n")
	// - Else fall back to sunrise/sunset bounds
	var isDay *bool
	if icon != "" {
		last := icon[len(icon)-1]
		switch last {
		case 'd':
			v := true
			isDay = &v
		case 'n':
			v := false
			isDay = &v
		}
	}
	if isDay == nil && parsed.Sys.Sunrise > 0 && parsed.Sys.Sunset > 0 {
		v := parsed.Dt >= parsed.Sys.Sunrise && parsed.Dt < parsed.Sys.Sunset
		isDay = &v
	}

	// Units handling based on the request URL.
	unitSystem := getUnitsFromURL(s.url)

	// Temperature normalization to Celsius.
	tempC := normalizeTempToC(parsed.Main.Temp, unitSystem)

	// Humidity is already percent.
	rh := parsed.Main.Humidity

	// Pressure hPa -> Pa
	surfacePa := parsed.Main.Pressure * 100.0
	var seaLevelPa *float64
	if parsed.Main.SeaLevel != nil {
		v := (*parsed.Main.SeaLevel) * 100.0
		seaLevelPa = &v
	}

	// Wind speed normalization to km/h
	wsKmh := normalizeSpeedToKmh(parsed.Wind.Speed, unitSystem)

	var wgKmh *float64
	if parsed.Wind.Gust != nil {
		v := normalizeSpeedToKmh(*parsed.Wind.Gust, unitSystem)
		wgKmh = &v
	}

	// Visibility in meters (already matches our model)
	var visM *float64
	if parsed.Visibility != nil {
		v := *parsed.Visibility
		visM = &v
	}

	// Map OpenWeather condition IDs -> canonical WMO code (our internal vocabulary).
	wmo := mapOpenWeatherToWMO(owmID)

	// Canonical text from our shared table.
	canonicalText := standards.WMOText(wmo, isDay)

	// Icon URL (optional).
	iconURL := ""
	if icon != "" {
		iconURL = fmt.Sprintf("https://openweathermap.org/img/wn/%s@2x.png", icon)
	}

	stationID := ""
	if parsed.ID != 0 {
		stationID = fmt.Sprintf("OPENWEATHER(%d)", parsed.ID)
	} else {
		stationID = fmt.Sprintf("OPENWEATHER(%.5f,%.5f)", parsed.Coord.Lat, parsed.Coord.Lon)
	}

	stationName := strings.TrimSpace(parsed.Name)
	if stationName == "" {
		stationName = "OpenWeatherMap"
	}

	obs := model.WeatherObservation{
		StationID:   stationID,
		StationName: stationName,
		Timestamp:   ts,

		// Canonical internal representation
		ConditionCode: wmo,
		ConditionText: canonicalText,
		IsDay:         isDay,

		// Provider evidence for troubleshooting mappings
		ProviderRawDescription: rawDesc,

		// Human-facing legacy fields: we populate with canonical text for consistency
		TextDescription: canonicalText,
		IconURL:         iconURL,

		TemperatureC: &tempC,

		WindDirectionDegrees: parsed.Wind.Deg,
		WindSpeedKmh:         &wsKmh,
		WindGustKmh:          wgKmh,

		BarometricPressurePa: &surfacePa,
		SeaLevelPressurePa:   seaLevelPa,
		VisibilityMeters:     visM,

		RelativeHumidityPercent: &rh,
	}

	// Stable event ID: key by source + timestamp.
	eventID := fmt.Sprintf("openweather:%s:%s", s.name, obs.Timestamp.UTC().Format(time.RFC3339Nano))

	return obs, eventID, nil
}

func getUnitsFromURL(raw string) string {
	u, err := url.Parse(raw)
	if err != nil {
		return "standard"
	}
	q := u.Query()
	units := strings.TrimSpace(strings.ToLower(q.Get("units")))
	if units == "" {
		return "standard"
	}
	switch units {
	case "standard", "metric", "imperial":
		return units
	default:
		return "standard"
	}
}

func normalizeTempToC(v float64, unitSystem string) float64 {
	switch unitSystem {
	case "metric":
		// Already °C
		return v
	case "imperial":
		// °F -> °C
		return (v - 32.0) * 5.0 / 9.0
	default:
		// "standard" => Kelvin -> °C
		return v - 273.15
	}
}

func normalizeSpeedToKmh(v float64, unitSystem string) float64 {
	switch unitSystem {
	case "imperial":
		// mph -> km/h
		return v * 1.609344
	default:
		// m/s -> km/h
		return v * 3.6
	}
}

// mapOpenWeatherToWMO maps OpenWeather weather condition IDs into your internal WMO code vocabulary.
//
// This is an approximate semantic mapping between two different code systems.
// Your current canonical WMO table is intentionally small and text-focused,
// so we map into that set (0/1/2/3/45/48/51/.../99) conservatively.
func mapOpenWeatherToWMO(owmID int) model.WMOCode {
	switch {
	// 2xx Thunderstorm
	case owmID >= 200 && owmID <= 232:
		return model.WMOCode(95)

	// 3xx Drizzle
	case owmID >= 300 && owmID <= 321:
		if owmID == 300 {
			return model.WMOCode(51)
		}
		if owmID == 302 {
			return model.WMOCode(55)
		}
		return model.WMOCode(53)

	// 5xx Rain
	case owmID >= 500 && owmID <= 531:
		// 511 is "freezing rain"
		if owmID == 511 {
			return model.WMOCode(67)
		}

		// showers bucket (520-531)
		if owmID >= 520 && owmID <= 531 {
			if owmID == 520 {
				return model.WMOCode(80)
			}
			if owmID == 522 {
				return model.WMOCode(82)
			}
			return model.WMOCode(81)
		}

		// normal rain intensity
		if owmID == 500 {
			return model.WMOCode(61)
		}
		if owmID == 501 {
			return model.WMOCode(63)
		}
		if owmID >= 502 && owmID <= 504 {
			return model.WMOCode(65)
		}
		return model.WMOCode(63)

	// 6xx Snow
	case owmID >= 600 && owmID <= 622:
		if owmID == 600 {
			return model.WMOCode(71)
		}
		if owmID == 601 {
			return model.WMOCode(73)
		}
		if owmID == 602 {
			return model.WMOCode(75)
		}

		// Snow showers bucket (620-622)
		if owmID == 620 {
			return model.WMOCode(85)
		}
		if owmID == 621 || owmID == 622 {
			return model.WMOCode(86)
		}

		return model.WMOCode(73)

	// 7xx Atmosphere (mist/smoke/haze/dust/fog/etc.)
	case owmID >= 701 && owmID <= 781:
		return model.WMOCode(45)

	// 800 Clear
	case owmID == 800:
		return model.WMOCode(0)

	// 80x Clouds
	case owmID == 801:
		return model.WMOCode(1)
	case owmID == 802:
		return model.WMOCode(2)
	case owmID == 803 || owmID == 804:
		return model.WMOCode(3)

	default:
		return model.WMOUnknown
	}
}