How to convert a string containing 2 numbers to currency with powershell?

I have text files that contain 2 numbers separated by a '+' sign. Trying to figure out how to replace them with currency equivalent .
Example Strings:

20+2 would be converted to $0.20+$0.02 USD

1379+121 would be> $13.79+$1.21 USD

400+20 would be $4.00+$0.20 USD

and so on.

I have tried using a few angles but they do not work or provide odd results. I tried to do it here by attempting to find by all patterns I think would come up .

.\Replace-FileString.ps1 "100+10" '$1.00+$0.10' $path1\*.txt -Overwrite
.\Replace-FileString.ps1 "1000+100" '$10.00+$1.00' $path1\*.txt -Overwrite
.\Replace-FileString.ps1 "300+30" '$3.00+$0.30' $path1\*.txt -Overwrite
.\Replace-FileString.ps1 "400+20" '$4.00+$0.20' $path1\*.txt -Overwrite

or this which just doesn't work.

Select-String -Path .\*txt -Pattern '[0-9][0-9]?[0-9]?[0-9]?[0-9]?\+[0-9][0-9]?[0-9]?[0-9]?[0-9]?' | ForEach-Object  {$_ -replace ", ", $"}  {$_ -replace "+", "+$"}

Solution

I tried to do it here by attempting to find by all patterns I think would come up

Don't try this - we're humans, and we won't think of all edge cases and even if we did, the amount of code we needed to write (or generate) would be ridiculous.

We need a more general solution here, and regex might indeed be helpful with this.

The pattern you describe could be expressed as three distinct parts:

1 or more consecutive digits
1 plus sign (+)
1 or more consecutive digits

With this in mind, let's start to simplifying the regex pattern to use:

\b\d+\+\d+\b

or, written out with explanations:

\b       # a word boundary
  \d+    # 1 or more digits
  \+     # 1 literal plus sign
  \d+    # 1 or more digits
\b       # a word boundary

Now, in order to transform an absolute value of cents into dollars, we'll need to capture the digits on either side of the +, so let's add capture groups:

\b(\d+)\+(\d+)\b

Now, in order to do anything interesting with the captured groups, we can utilize the Regex.Replace() method - it can take a scriptblock as its substitution argument:

$InputString  = '1000+10'
$RegexPattern = '\b(\d+)\+(\d+)\b'
$Substitution = {
    param($Match)

    $Results = foreach($Amount in $Match.Groups[1,2].Value){
        $Dollars = [Math]::Floor(($Amount / 100))
        $Cents   = $Amount % 100
        '${0:0}.{1:00}' -f $Dollars,$Cents
    }
    return $Results -join '+'
}

In the scriptblock above, we expect the two capture groups ($Match.Groups[1,2]), calculate the amount of dollars and cents, and then finally use the -f string format operator to make sure that the cents value is always two digits wide.

To do the substitution, invoke the Replace() method:

[regex]::Replace($InputString,$RegexPattern,$Substitution)

And there you go!

Applying to to a bunch of files is as easy as:

$RegexPattern = '\b(\d+)\+(\d+)\b'
$Substitution = {
    param($Match)

    $Results = foreach($Amount in $Match.Groups[1,2].Value){
        $Dollars = [Math]::Floor(($Amount / 100))
        $Cents   = $Amount % 100
        '${0:0}.{1:00}' -f $Dollars,$Cents
    }
    return $Results -join '+'
}

foreach($file in Get-ChildItem $path *.txt){
    $Lines = Get-Content $file.FullName
    $Lines |ForEach-Object {
        [regex]::Replace($_, $RegexPattern, $Substitution)
    } |Set-Content $file.FullName
}