$script:options = [System.Text.RegularExpressions.RegexOptions]
$script:OpenMatcher = [regex]::new('[\{\[]\s*$', ($options::Compiled -bor $options::ExplicitCapture))

function ConvertTo-PrettyJson {
    [CmdletBinding(DefaultParameterSetName="withObject",SupportsShouldProcess=$true)]
    param (
        [parameter(Mandatory,ValueFromPipeline=$true,ParameterSetName="withObject")]
        $InputObject,
        [parameter(Mandatory,ParameterSetName="withJson")]
        [string]
        $Json,
        [ValidateLength(1, 1)]
        [string]
        $IndentChar = ' ',
        [ValidateRange(1, 20)]
        [int]
        $IndentWidth = 4
    )

    switch ($PSCmdlet.ParameterSetName) {
        "withObject" {
            if (! $InputObject) {
                return
            }
            $Json = ConvertTo-Json $InputObject
        }
        "withJson" {
            try {
                $Json = ConvertFrom-Json $Json | ConvertTo-Json $Json
            }
            catch {
                throw 'invalid json format: $Json.'
            }
        }
    }

    if (! $InputObject) { return }

    # unit indent string
    $indent = $IndentChar * $IndentWidth

    # indent stacks for open and close positions
    $indents = @()
    $endIndents = @()

    # current indent
    $lastIndent = -1
    $closeIndent = -1

    # real indent count
    $indentCount = 0

    $Json -split "`r?`n" | ? { $_ } -PipelineVariable line | % {
        $indentSize = $line -match '^ *' | % { $Matches[0].Length }
        switch ($indentSize) {
            $lastIndent {
                # the same indent from previous line
            }
            $closeIndent {
                # parenthesis closed.
                $indents = @($indents | select -Skip 1)
                $endIndents = @($endIndents | select -Skip 1)
                $lastIndent = $indents[0]
                $closeIndent = $endIndents[0]
                $indentCount--
            }
            default {
                # new indent size
                $lastIndent = $indentSize
                $indents = ,$lastIndent + $indents
            }
        }

        # out current line.
        Write-Output (($indent * $indentCount) + $line.Substring($indentSize))

        $match = $script:OpenMatcher.Match($line)
        if ($match.Success) {
            # parenthesis opened.
            $closeIndent = $match.Index
            $endIndents = ,$closeIndent + $endIndents
            $indentCount++
        }
    } | Out-String
}