param(
    [Parameter(Mandatory = $true)][string]$Executable,
    [Parameter(Mandatory = $true)][string]$ArgumentsJsonPath,
    [Parameter(Mandatory = $true)][string]$CapturePath,
    [Parameter(Mandatory = $true)][string]$StdoutPath,
    [Parameter(Mandatory = $true)][string]$StderrPath,
    [Parameter(Mandatory = $true)][string]$StartedStatusPath,
    [Parameter(Mandatory = $true)][string]$ResultStatusPath
)

$ErrorActionPreference = 'Stop'

function Write-JsonAtomically {
    param(
        [Parameter(Mandatory = $true)][object]$Value,
        [Parameter(Mandatory = $true)][string]$Path
    )

    $temporaryPath = "$Path.tmp"
    $json = $Value | ConvertTo-Json -Depth 8
    $encoding = New-Object System.Text.UTF8Encoding($false)
    [System.IO.File]::WriteAllText($temporaryPath, $json + [Environment]::NewLine, $encoding)
    Move-Item -LiteralPath $temporaryPath -Destination $Path -Force
}

$decodedArguments = Get-Content -Raw -LiteralPath $ArgumentsJsonPath |
    ConvertFrom-Json
if ($decodedArguments -isnot [System.Array]) {
    throw 'ArgumentsJsonPath must contain a JSON array.'
}
$childArguments = @(
    foreach ($argument in $decodedArguments) {
        [string]$argument
    }
)
$startedAt = [DateTimeOffset]::UtcNow
$finishedAt = $null
$childProcess = $null
$exitCode = $null
$runnerError = $null
$captureSize = 0
$sha256 = $null

try {
    $startParameters = @{
        FilePath = $Executable
        ArgumentList = $childArguments
        RedirectStandardOutput = $StdoutPath
        RedirectStandardError = $StderrPath
        PassThru = $true
        WindowStyle = 'Hidden'
    }
    $childProcess = Start-Process @startParameters
    # PowerShell 5 can lose ExitCode for redirected processes unless the
    # underlying process handle is opened before WaitForExit().
    $null = $childProcess.Handle

    Write-JsonAtomically -Path $StartedStatusPath -Value ([ordered]@{
        state = 'RUNNING'
        pid = $childProcess.Id
        started_at = $startedAt.ToString('o')
        capture_path = $CapturePath
    })

    $childProcess.WaitForExit()
    $childProcess.Refresh()
    $exitCode = [int]$childProcess.ExitCode
} catch {
    $runnerError = $_.Exception.ToString()
} finally {
    $finishedAt = [DateTimeOffset]::UtcNow
    if (Test-Path -LiteralPath $CapturePath) {
        try {
            $captureSize = [int64](Get-Item -LiteralPath $CapturePath).Length
            $sha256 = (
                Get-FileHash -LiteralPath $CapturePath -Algorithm SHA256
            ).Hash.ToLowerInvariant()
        } catch {
            $additionalError = $_.Exception.ToString()
            if ([string]::IsNullOrWhiteSpace($runnerError)) {
                $runnerError = $additionalError
            } else {
                $runnerError = $runnerError + [Environment]::NewLine + $additionalError
            }
        }
    }

    Write-JsonAtomically -Path $ResultStatusPath -Value ([ordered]@{
        pid = if ($null -ne $childProcess) { $childProcess.Id } else { $null }
        started_at = $startedAt.ToString('o')
        finished_at = $finishedAt.ToString('o')
        duration = ($finishedAt - $startedAt).TotalSeconds
        exit_code = $exitCode
        capture_path = $CapturePath
        capture_size = $captureSize
        sha256 = $sha256
        runner_error = $runnerError
    })
}

if ($null -eq $exitCode) {
    exit 255
}
exit $exitCode