Friday Fun: PowerShell Weather Widget

Recently, someone on Twitter turned me on to an resource that could be used in a PowerShell session to display weather information. This is apparently a well-established and well-regarded source. Once I worked out the basics, I naturally wanted to see what else I could do it with. Here's what I came up with.

Everything I want to talk about today involves consuming a REST API using Invoke-RestMethod. The primary URI, which you can test in your browser is http://wttr.in. Include a location in the URI like http://wttr.in/chicago. But it gets better. The API source and documentation can be found at https://github.com/chubin/wttr.in. Once I spent a little time researching what I could do, I settled on a basic command like this:

Invoke-RestMethod -Uri http://wttr.in/Syracuse?format=2 -UseBasicParsing -DisableKeepAlive

I thought that was pretty cool. Although the emojis only display in a terminal console that supports them, like a PowerShell session running in Windows Terminal. You'll have less luck running this in the PowerShell ISE or a VS Code console.

Now I need to push this concept.

Formatting the Location

It was simple enough to build a quick script to run this command. I even added a location parameter. The location can be a ZIP code or place name. I was hoping to create output that included the location. But I wanted to make sure the location was properly formatted.

if ($Location -match '^([a-zA-Z\s\.\,])+$') {
    $Location = [System.Globalization.CultureInfo]::CurrentCulture.TextInfo.ToTitleCase($location.tolower())
}

If the location is a string, like "chicago", this snippet of text will convert it to "Chicago". A string like "las vegas" becomes "Las Vegas".

Using the Local Time

As I was developing my code, I was including the current date and time. But then I realized that if I was running my script for another location, like Las Vegas, displaying my time in the Eastern time zone, might be confusing. I needed to get the time zone for the location so that I could adjust the time accordingly.

I couldn't find anything in the basic wttr.in request that would include that information until I came across the optional v2 API. The format looks like http://v2.wttr.in/chicago. Unfortunately, there is no way to get the result as structured data like JSON or XML. So I had to resort to a regular expression to parse out the time zone name. I built a helper function to do that.

Function GetTZ {
    Param([string]$location)
    Write-Verbose "Getting v2 data from wttr.in for $location"
    $tmp = Invoke-RestMethod -uri "http://v2.wttr.in/$location" -disableKeepAlive -useBasicParsing
    $rx = [System.Text.RegularExpressions.Regex]::new("\b([a-z_]+\/[a-z_]+)\b","IgnoreCase,Multiline")
    $timezone = $rx.match($tmp).Value
    Write-Verbose "Detected timezone $timezone"
    $timezone
}

This will give me a value like America/Chicago. The next step is to determine the timezone offset. Fortunately, I had another code snippet that uses a REST API at http://worldtimeapi.org. With this API, I create a custom object.

My custom object includes the local time in that time zone which I can then use in my output.

Make It Pretty with ANSI

The last step was to make it pretty. I wanted to draw colored line box around the weather and location information using ANSI and special characters. Normally, this isn't too difficult because I can calculate line lengths.

However, there is a little challenge with emoji-strings. Even though PowerShell might show identical length for two different locations, if the weather emoji was different it could throw off the spacing. This meant my closing | for the line with the weather might be off. I have not found a way to account for kerning issues when using emojis, so I resorted to using Write-Host.

With this approach, I could save the cursor position of the previous line, display the weather line, move the cursor, and then display the closing |.

Write-Host $line1
Write-Host $line2
Write-Host $line3a -NoNewline
#get the cursor position
$pos = $host.ui.RawUI.CursorPosition
#adjust it
$pos.x = $line1.Length - $boxAnsi.Length - 1
#move the cursor
$host.ui.RawUI.CursorPosition = $pos
#write the closing box element
Write-Host $line3b
Write-Host $line4

I'm not proud of the hack, but it works.

The ANSI sequences are written to run in Windows PowerShell or PowerShell 7. Here's the complete script.

#requires -version 5.1

# see https://github.com/chubin/wttr.in for API information

#this must be run in a Windows Terminal session that supports the glyphs
#or use -Force if you know you are.

[cmdletbinding()]
Param([string]$Location = "Syracuse,NY", [switch]$Force)

Function TestWT {
    $parent = Get-CimInstance -ClassName win32_process -Filter "processid=$pid"-Property ParentProcessID
    (Get-Process -Id $parent.ParentProcessId).ProcessName -eq "WindowsTerminal"
}
Function GetTZ {
    Param([string]$location)
    Write-Verbose "Getting v2 data from wttr.in for $location"
    $tmp = Invoke-RestMethod -uri "http://v2.wttr.in/$location" -disableKeepAlive -useBasicParsing
    $rx = [System.Text.RegularExpressions.Regex]::new("\b([a-z_]+\/[a-z_]+)\b","IgnoreCase,Multiline")
    $timezone = $rx.match($tmp).Value
    Write-Verbose "Detected timezone $timezone"
    $timezone
}
Function GetTZData {
    [cmdletbinding()]
    [OutputType("pscustomobject","TimeZoneData")]
    Param(
        [Parameter(Position = 0, Mandatory, ValueFromPipeline,
         HelpMessage = "Enter a timezone location like Pacific/Auckland. It is case sensitive.")]
        [string]$TimeZoneArea,
        [parameter(HelpMessage = "Return raw, unformatted data.")]
        [switch]$Raw
    )
    Begin {
        Write-Verbose "Starting $($myinvocation.mycommand)"
        $base = "http://worldtimeapi.org/api/timezone"
    } #begin

    Process {
        Write-Verbose "Getting time zone information for $TimeZoneArea"
        $target = "$base/$TimeZoneArea"
        Try {
            $data = Invoke-RestMethod -Uri $target -DisableKeepAlive -UseBasicParsing -ErrorAction Stop -ErrorVariable e
        }
        Catch {
            Throw $e.innerexception
        }
        if ($data -AND $Raw) {
            $data
        }
        elseif ($data) {
            if ($data.utc_offset -match "\+") {
                $offset = ($data.utc_offset.substring(1) -as [timespan])
            }
            else {
                $offset = ($data.utc_offset -as [timespan])
            }

            [datetime]$dt = $data.DateTime
            [pscustomobject]@{
                PSTypename         = "TimeZoneData"
                Timezone           = $data.timezone
                Abbreviation       = $data.abbreviation
                Offset             = $offset
                DaylightSavingTime = $data.dst
                Time               = $dt.ToUniversalTime().Addseconds($data.raw_offset)
            }
           # (Get-Date ($data.datetime -split "[\+-]\d{2}:\d{2}")[0])
        }
    } #process

    End {
        Write-Verbose "Ending $($myinvocation.mycommand)"

    } #end

} #close GetTZData

#characters for building a line box
$charHash = @{
    upperLeft  = [char]0x250c
    upperRight = [char]0x2510
    lowerRight = [char]0x2518
    lowerLeft  = [char]0x2514
    horizontal = [char]0x2500
    vertical   = [char]0x2502
}

Write-Verbose "Getting weather summary for $location"

#ANSI sequences
$boxAnsi = "$([char]0x1b)[38;5;11m"
$closeAnsi = "$([char]0x1b)[0m"
$textAnsi = "$([char]0x1b)[38;5;191m"

#convert location to title case if it is words
if ($Location -match '^([a-zA-Z\s\.\,])+$') {
    $Location = [System.Globalization.CultureInfo]::CurrentCulture.TextInfo.ToTitleCase($location.tolower())
}
if ($Force -OR (TestWT)) {
    $w = Invoke-RestMethod -Uri "http://wttr.in/{$location}?format=2"
    Write-Verbose "Getting local time settings for $Location"
    $localtime = gettzdata (gettz $location)
    [string]$date =  "{0:g}" -f $localtime.time

    $data = ($w.trim()) -replace "\s+"," "
    #internal sum of the individual elements. Trying to figure out kerning or spacing
    #$internalLength = $($data.split() | foreach { $_.length} | measure-object -sum).sum
    $header = " {0}" -f $location
    $headerAnsi = "{0}{1}" -f $textAnsi, $header
    $value = "{0} {1}" -f $textAnsi, $data

    $line1 = "{0}{1} {2} {3}{4}" -f $boxAnsi, $charHash.upperleft, $date, ([string]$charHash.horizontal * ($data.length-$date.length)), $charhash.upperRight
    $line2 = "{0}{1}{2}{3}{4}" -f $boxAnsi, $charHash.Vertical,$headerAnsi.padright($line1.length-1), $boxAnsi,$charHash.Vertical
    $line3a = "{0}{1}{2}" -f $boxAnsi, $charHash.Vertical,$value
    #($value.padright($header.length))

    $line3b = "{0}{1}" -f $boxAnsi,$charHash.Vertical
    $line4 = "{0}{1}{2}{3}{4}" -f $boxAnsi, $charHash.Lowerleft, ([string]$charHash.horizontal * ($data.length+2)), $charhash.LowerRight, $closeAnsi

    Write-Host $line1
    Write-Host $line2
    Write-Host $line3a -NoNewline
    #get the cursor position
    $pos = $host.ui.RawUI.CursorPosition
    #adjust it
    $pos.x = $line1.Length - $boxAnsi.Length - 1
    #move the cursor
    $host.ui.RawUI.CursorPosition = $pos
    #write the closing box element
    Write-Host $line3b
    Write-Host $line4
else {
    Write-Warning "This needs to be run in a Windows Terminal session."
}
}

Next Steps

I should turn this into a function with an alias to make it easy to run. I might dig deeper into the source files for wttri.in and see if I can't make some of those calls directly. This might make it easier to grab the time zone information at the same time. I might also try adding this to my PowerShell prompt function and display it in a corner of my session.

Give it a try, have some fun, and let me know what you think.

Update

I have posted an updated version of this function on GitHub at https://gist.github.com/jdhitsolutions/f2fb0184c2dbab107f2416fb775d462b. This version accepts pipeline input.