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Add dew point calculations and display to weather output #30

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46 changes: 40 additions & 6 deletions internal/weather/display.go
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Original file line number Diff line number Diff line change
Expand Up @@ -45,10 +45,28 @@ const (

var directionSymbols = [...]string{"↑", "↗", "→", "↘", "↓", "↙", "←", "↖"}


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@WarningImHack3r WarningImHack3r Oct 5, 2025

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Not necessary unless a godoc is added here

func celsiusToFahrenheit(c float64) float64 {
return c*9/5 + 32
}

// dewPointCelsius calculates dew point in Celsius given temperature (C) and relative humidity (%)
func dewPointCelsius(tempC float64, humidity int) float64 {
t := tempC
rh := float64(humidity)
a := 17.27
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@WarningImHack3r WarningImHack3r Oct 5, 2025

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What are a and b? I think they should be constants

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@sierikov sierikov Nov 16, 2025

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These are from Magnus Tetens formula. And they are often called just a and b.

Where a is constant "Magnus Coefficient" and b is temperature constant. So we can call it so. Or leave it as is, they often appear in this way. What do you prefer?

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@WarningImHack3r WarningImHack3r Nov 16, 2025

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I feel like if it represents something, let’s give it a name, otherwise single letters are fine

b := 237.7
alpha := ((a * t) / (b + t)) + math.Log(rh/100)
return (b * alpha) / (a - alpha)
}

// dewPointFahrenheit calculates dew point in Fahrenheit given temperature (F) and relative humidity (%)
func dewPointFahrenheit(tempF float64, humidity int) float64 {
tempC := (tempF - 32) * 5 / 9
dpC := dewPointCelsius(tempC, humidity)
return celsiusToFahrenheit(dpC)
}

// getWindDirectionSymbol converts wind degrees to a direction symbol
func getWindDirectionSymbol(degrees int) string {
index := int((float64(degrees)+22.5)/45.0) % 8
Expand All @@ -67,21 +85,27 @@ func DisplayWeather(weather *Weather, config Config) {
weatherID = weather.Weather[0].ID
}


// Determine units based on config
var windSpeedUnits, tempUnit string
var windSpeedUnits, tempUnit, dewPointUnit string
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@WarningImHack3r WarningImHack3r Oct 5, 2025

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Can't we just use the tempUnit as it has the same purpose and cannot be different?


// Convert wind speed based on provider and units
windSpeed := weather.Wind.Speed
temperature := weather.Main.Temp
dewPoint := 0.0

switch config.Units {
case UnitImperial:
windSpeedUnits = "mph"
tempUnit = "°F"
dewPointUnit = "°F"

// Convert temperature for both providers
temperature = celsiusToFahrenheit(temperature)

// Calculate dew point in Fahrenheit
dewPoint = dewPointFahrenheit(temperature, weather.Main.Humidity)

// Convert wind speed based on this provider
if config.Provider == ProviderOpenWeatherMap {
windSpeed *= MpsToMph // m/s to mph
Expand All @@ -92,6 +116,10 @@ func DisplayWeather(weather *Weather, config Config) {
default:
windSpeedUnits = "km/h"
tempUnit = "°C"
dewPointUnit = "°C"

// Calculate dew point in Celsius
dewPoint = dewPointCelsius(weather.Main.Temp, weather.Main.Humidity)

// Convert wind speed for OpenWeatherMap provider
if config.Provider == ProviderOpenWeatherMap {
Expand All @@ -110,7 +138,7 @@ func DisplayWeather(weather *Weather, config Config) {
popPercent = int(math.Round(weather.Pop * 100))
}

labels := make([]string, 0, 6)
labels := make([]string, 0, 7)
values := make([]string, 0, cap(labels))

// City name display
Expand All @@ -136,6 +164,9 @@ func DisplayWeather(weather *Weather, config Config) {
labels = append(labels, "Temp ")
values = append(values, fmt.Sprintf("%.1f%s", temperature, tempUnit))

labels = append(labels, "Dew Pt ")
values = append(values, fmt.Sprintf("%.1f%s", dewPoint, dewPointUnit))

labels = append(labels, "Wind ")
values = append(
values, fmt.Sprintf("%.1f %s %s", windSpeed, windSpeedUnits, getWindDirectionSymbol(weather.Wind.Deg)),
Expand All @@ -150,6 +181,7 @@ func DisplayWeather(weather *Weather, config Config) {
// Compact mode doesn't use labels in the same way
weatherDisplay := description
tempDisplay := fmt.Sprintf("%.1f%s", temperature, tempUnit)
dewPointDisplay := fmt.Sprintf("%.1f%s", dewPoint, dewPointUnit)
windDisplay := fmt.Sprintf("%.1f%s %s", windSpeed, windSpeedUnits, getWindDirectionSymbol(weather.Wind.Deg))
humidityDisplay := fmt.Sprintf("%d%%", weather.Main.Humidity)
precipitationDisplay := fmt.Sprintf("%.1fmm | %d%%", precipitationMM, popPercent)
Expand All @@ -161,6 +193,7 @@ func DisplayWeather(weather *Weather, config Config) {
cityName,
weatherDisplay,
tempDisplay,
dewPointDisplay,
windDisplay,
humidityDisplay,
precipitationDisplay,
Expand Down Expand Up @@ -274,11 +307,11 @@ func displayWeatherArtAligned(mainWeather string, weatherID int, labels, values
}

// displayWeatherArtCompact shows ASCII art with compact formatting

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@WarningImHack3r WarningImHack3r Oct 5, 2025

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This one has to be removed to not unlink the godoc from the function

func displayWeatherArtCompact(
mainWeather string, weatherID int, cityName, weatherDisplay,
tempDisplay, windDisplay, humidityDisplay, precipDisplay string, config Config,
tempDisplay, dewPointDisplay, windDisplay, humidityDisplay, precipDisplay string, config Config,
) {

// Get the weather icon
iconLines := getWeatherIcon(mainWeather, weatherID, config.UseColors)

Expand All @@ -289,6 +322,7 @@ func displayWeatherArtCompact(
}
weatherDisplay = getColoredWeatherText(mainWeather, weatherDisplay)
tempDisplay = color.RedString(tempDisplay)
dewPointDisplay = color.CyanString(dewPointDisplay)
windDisplay = color.GreenString(windDisplay)
humidityDisplay = color.CyanString(humidityDisplay)

Expand All @@ -301,14 +335,14 @@ func displayWeatherArtCompact(
}

// Prepare the text lines
textLines := make([]string, 0, 5)
textLines := make([]string, 0, 7)
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@WarningImHack3r WarningImHack3r Oct 5, 2025

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Are you sure it has to be increased by 2?

textLines = append(textLines, "") // Empty line to match icon top spacing

if cityName != "" && config.ShowCityName {
textLines = append(textLines, cityName)
}

textLines = append(textLines, weatherDisplay, tempDisplay, windDisplay, humidityDisplay)
textLines = append(textLines, weatherDisplay, tempDisplay, dewPointDisplay, windDisplay, humidityDisplay)

if precipDisplay != "" {
textLines = append(textLines, precipDisplay)
Expand Down