weatherfeeder/standards/wmo.go

package standards

// This file provides small, shared helper functions for reasoning about WMO codes.
// These are intentionally "coarse" categories that are useful for business logic,
// dashboards, and alerting decisions.
//
// Example uses:
// - jogging suitability: precipitation? thunderstorm? freezing precip?
// - quick glance: "is it cloudy?" "is there any precip?"
// - downstream normalizers / aggregators

import (
	"fmt"

	"gitea.maximumdirect.net/ejr/weatherfeeder/model"
)

type WMODescription struct {
	Day   string
	Night string
}

// WMODescriptions is the canonical internal mapping of WMO code -> day/night text.
// These are used to populate model.WeatherObservation.ConditionText.
var WMODescriptions = map[model.WMOCode]WMODescription{
	0:  {Day: "Sunny", Night: "Clear"},
	1:  {Day: "Mainly Sunny", Night: "Mainly Clear"},
	2:  {Day: "Partly Cloudy", Night: "Partly Cloudy"},
	3:  {Day: "Cloudy", Night: "Cloudy"},
	45: {Day: "Foggy", Night: "Foggy"},
	48: {Day: "Rime Fog", Night: "Rime Fog"},
	51: {Day: "Light Drizzle", Night: "Light Drizzle"},
	53: {Day: "Drizzle", Night: "Drizzle"},
	55: {Day: "Heavy Drizzle", Night: "Heavy Drizzle"},
	56: {Day: "Light Freezing Drizzle", Night: "Light Freezing Drizzle"},
	57: {Day: "Freezing Drizzle", Night: "Freezing Drizzle"},
	61: {Day: "Light Rain", Night: "Light Rain"},
	63: {Day: "Rain", Night: "Rain"},
	65: {Day: "Heavy Rain", Night: "Heavy Rain"},
	66: {Day: "Light Freezing Rain", Night: "Light Freezing Rain"},
	67: {Day: "Freezing Rain", Night: "Freezing Rain"},
	71: {Day: "Light Snow", Night: "Light Snow"},
	73: {Day: "Snow", Night: "Snow"},
	75: {Day: "Heavy Snow", Night: "Heavy Snow"},
	77: {Day: "Snow Grains", Night: "Snow Grains"},
	80: {Day: "Light Showers", Night: "Light Showers"},
	81: {Day: "Showers", Night: "Showers"},
	82: {Day: "Heavy Showers", Night: "Heavy Showers"},
	85: {Day: "Light Snow Showers", Night: "Light Snow Showers"},
	86: {Day: "Snow Showers", Night: "Snow Showers"},
	95: {Day: "Thunderstorm", Night: "Thunderstorm"},
	96: {Day: "Light Thunderstorms With Hail", Night: "Light Thunderstorms With Hail"},
	99: {Day: "Thunderstorm With Hail", Night: "Thunderstorm With Hail"},
}

// WMOText returns the canonical text description for a WMO code.
// If isDay is nil, it prefers the Day description (if present).
//
// This is intended to be used by drivers after they set ConditionCode.
func WMOText(code model.WMOCode, isDay *bool) string {
	if code == model.WMOUnknown {
		return "Unknown"
	}

	desc, ok := WMODescriptions[code]
	if !ok {
		// Preserve the code in the message so it's diagnosable.
		return fmt.Sprintf("Unknown (WMO %d)", int(code))
	}

	// If day/night is unknown, default to Day if it exists.
	if isDay == nil {
		if desc.Day != "" {
			return desc.Day
		}
		if desc.Night != "" {
			return desc.Night
		}
		return fmt.Sprintf("Unknown (WMO %d)", int(code))
	}

	if *isDay {
		if desc.Day != "" {
			return desc.Day
		}
		// Fallback
		if desc.Night != "" {
			return desc.Night
		}
		return fmt.Sprintf("Unknown (WMO %d)", int(code))
	}

	// Night
	if desc.Night != "" {
		return desc.Night
	}
	// Fallback
	if desc.Day != "" {
		return desc.Day
	}
	return fmt.Sprintf("Unknown (WMO %d)", int(code))
}

// IsKnownWMO returns true if the code exists in our mapping table.
func IsKnownWMO(code model.WMOCode) bool {
	if code == model.WMOUnknown {
		return false
	}
	_, ok := WMODescriptions[code]
	return ok
}

func IsThunderstorm(code model.WMOCode) bool {
	switch code {
	case 95, 96, 99:
		return true
	default:
		return false
	}
}

func IsHail(code model.WMOCode) bool {
	switch code {
	case 96, 99:
		return true
	default:
		return false
	}
}

func IsFog(code model.WMOCode) bool {
	switch code {
	case 45, 48:
		return true
	default:
		return false
	}
}

// IsPrecipitation returns true if the code represents any precipitation
// (drizzle, rain, snow, showers, etc.).
func IsPrecipitation(code model.WMOCode) bool {
	switch code {
	// Drizzle
	case 51, 53, 55, 56, 57:
		return true

	// Rain
	case 61, 63, 65, 66, 67:
		return true

	// Snow
	case 71, 73, 75, 77:
		return true

	// Showers
	case 80, 81, 82, 85, 86:
		return true

	// Thunderstorm (often includes rain/hail)
	case 95, 96, 99:
		return true

	default:
		return false
	}
}

func IsRainFamily(code model.WMOCode) bool {
	switch code {
	// Drizzle + freezing drizzle
	case 51, 53, 55, 56, 57:
		return true

	// Rain + freezing rain
	case 61, 63, 65, 66, 67:
		return true

	// Rain showers
	case 80, 81, 82:
		return true

	// Thunderstorm often implies rain
	case 95, 96, 99:
		return true

	default:
		return false
	}
}

func IsSnowFamily(code model.WMOCode) bool {
	switch code {
	// Snow and related
	case 71, 73, 75, 77:
		return true

	// Snow showers
	case 85, 86:
		return true

	default:
		return false
	}
}

// IsFreezingPrecip returns true if the code represents freezing drizzle/rain.
func IsFreezingPrecip(code model.WMOCode) bool {
	switch code {
	case 56, 57, 66, 67:
		return true
	default:
		return false
	}
}

// IsSkyOnly returns true for codes that represent "sky condition only"
// (clear/mostly/partly/cloudy) rather than fog/precip/etc.
func IsSkyOnly(code model.WMOCode) bool {
	switch code {
	case 0, 1, 2, 3:
		return true
	default:
		return false
	}
}