enter-json.ps1

param(
    [Parameter(ValueFromPipeline)]
    [string]$json
)

$obj = ConvertFrom-Json -InputObject $json -Depth 100 -AsHashtable

$location = "/"

function Test-Location ($path) {
    $paths = $path.Split('/')
    return $true
}

function Get-Json ($filter) {
    $cur = $obj
    foreach ($path in $location.Split('/', [StringSplitOptions]::RemoveEmptyEntries)) {
        $cur = $cur.$path
    }

    return ($cur | Out-String)
}

while($true) {
    $i = Read-Host -Prompt $location
    $command = $i.Split(' ')

    switch ($command[0]) {
        'cd' {
            $newLocation = $command[1]
            if ($newLocation -eq '..') {
                if ($location -eq '/') {
                    Write-Error "At root"
                    continue
                }

                $location = Split-Path $location -Parent
                if ("" -eq $location) {
                    $location = '/'
                }
            }
            elseif (Test-Location $newLocation) {
                $location = Join-Path $location $newLocation
            }
            else {
                Write-Error "Path does not exist"
            }
        }

        'dir' {
            $filter = $command[1]
            Write-Host (Get-Json $filter)
        }

        'exit' {
            return
        }

        default {
            Write-Error "Command not found.  Use 'cd', 'dir', or 'exit'"
        }
    }
}