param(
    [int] $Port = 7788,
    [string] $Log = "$PSScriptRoot\sc_link.log"
)

function Say($msg) {
    for ($i = 0; $i -lt 5; $i++) {
        try { "$msg" | Out-File -FilePath $Log -Append -Encoding utf8; return }
        catch { Start-Sleep -Milliseconds 100 }
    }
}

"" | Out-File -FilePath $Log -Encoding utf8
Say "[link-sc] starting on 127.0.0.1:$Port"

$listener = New-Object System.Net.Sockets.TcpListener([System.Net.IPAddress]::Loopback, $Port)
$listener.Server.SetSocketOption('Socket', 'ReuseAddress', $true)
$bound = $false
for ($i = 0; $i -lt 30 -and -not $bound; $i++) {
    try { $listener.Start(); $bound = $true } catch { Start-Sleep -Seconds 1 }
}
if (-not $bound) { Say "[link-sc] could not bind"; exit 1 }
Say "[link-sc] listening"

$client = $listener.AcceptTcpClient()
Say "[link-sc] === shard connected ==="
$stream = $client.GetStream()
$reader = New-Object System.IO.StreamReader($stream)
$writer = New-Object System.IO.StreamWriter($stream)
$writer.AutoFlush = $true

$deadline = (Get-Date).AddSeconds(20)
$confirmed = $false

while ((Get-Date) -lt $deadline) {
    if ($stream.DataAvailable) {
        $line = $reader.ReadLine()
        if ($null -eq $line) { break }
        Say "[link-sc] <- $line"

        # When the shard emits a link.request, extract the code and confirm it.
        if (-not $confirmed -and $line -match '"kind":"link\.request"') {
            if ($line -match '"code":"([^"]+)"') {
                $code = $Matches[1]
                $confirm = '{"kind":"link.confirm","code":"' + $code + '","websiteUserId":"web-9931"}'
                $writer.WriteLine($confirm)
                Say "[link-sc] -> $confirm"
                $confirmed = $true
            }
        }
    } else {
        Start-Sleep -Milliseconds 100
    }
}

# Second exchange: send a bad confirm to prove the error path.
$writer.WriteLine('{"kind":"link.confirm","code":"BADCOD","websiteUserId":"web-0000"}')
Say '[link-sc] -> {"kind":"link.confirm","code":"BADCOD","websiteUserId":"web-0000"}'
$t = (Get-Date).AddSeconds(3)
while ((Get-Date) -lt $t) {
    if ($stream.DataAvailable) { $l = $reader.ReadLine(); if ($l) { Say "[link-sc] <- $l" } }
    else { Start-Sleep -Milliseconds 100 }
}

Say "[link-sc] done"
$client.Close(); $listener.Stop()