Scripting Games August 2015 entry

sg-august.2015.ps1

# Works with PowerShell v2, but only works with very simple JSON
function Get-SimpleJSON {
    param(        
        [Parameter(Mandatory=$true,
        ValueFromPipeline=$True)]
        [Alias('Uri')]
        [string]$JSONUri,
        
        [Alias('CamelCase')]
        [switch]$TitleCase
    )
    if ($JSONUri -notlike "*://*") { $JSONUri = "http://$($JSONUri)" }
    
    # Create web client and request the JSON output
    $webClient = New-Object -TypeName System.Net.WebClient
    $rawOutput = $webClient.DownloadString($JSONUri)
    
    # Trim the JSON and make it easier for me to parse
    $rawObject = $rawOutput.trim().trim('{','}').replace(',"',';').replace('":','=').replace('"','').split(';')

    # Dynamically build output object properties hashtable
    $props = @{}
    foreach ($prop in $rawObject) {
        # Split the key=value pair
        $key = $prop.Split('=')[0]
        $value = $prop.Split('=')[1]
        if ($TitleCase) {
            # Convert key name to Title (or Camel) case
            $key = (Get-Culture).TextInfo.ToTitleCase($key.ToLower())
        }
        # Add the current property to the hashtable
        $props.Add($key, $value)
    }
    # Create the object and write it out
    $obj = New-Object -TypeName PSObject -Property $props
    Write-Output -InputObject $obj
}

# And here's it in use:
Get-SimpleJSON -JSONUri www.telize.com/geoip | Select-Object longitude, latitude, continent_code, country_code3 | Format-Table -AutoSize

# Or as a one-liner for PowerShell v3+:
ConvertFrom-Json -InputObject (Invoke-WebRequest -Uri www.telize.com/geoip).Content | Select-Object longitude, latitude, continent_code, country_code3 | Format-Table -AutoSize

Some thoughts behind this:

After playing with this puzzle for a little bit, I realized I could easily solve the basic puzzle with a call to Invoke-WebRequest and passing the "Content" property of that on to ConvertFrom-JSON. That seemed too easy, but then I realized that neither of those cmdlets exist in PowerShell version 2! So, I decided it would be a more interesting challenge to solve the puzzle for PSv2, and make it a functional cmdlet while I'm at it.

So, to start, I created a web client using the .NET class System.Net.WebClient, then used it to download the supplied URI. Then, I trimmed it and replaced certain specific characters that helped make it easier to work with for me, and split the output in to an array of key=value pairs.

Once I had that, I just dynamically built a hash table using those pairs, attached the hash table as a list of properties to a new object, and wrote the object out to the pipeline.

Note: this works with PowerShell version 2 and newer, but unlike ConvertFrom-JSON, it won't work with any complex JSON (basically, anything that is more complicated than a list of key=value pairs, such as if the value is an array or hash table). I tried to come up with a way to handle complex JSON, but it's a lot more work than I'm ready to put into this.