# Pair a LIGHTSPEED mouse to the G903 receiver (046D:C539) via HID++ register 0xB2.
Add-Type -Path (Join-Path $PSScriptRoot 'Hidpp.cs')
$rx = New-Object HidppReceiver (, [HidppReceiver]::Find('vid_046d&pid_c539'))

function Reg([byte[]]$req) {
    while ($rx.Next(0)) {}
    $rx.Send($req)
    $deadline = (Get-Date).AddSeconds(2)
    while ((Get-Date) -lt $deadline) {
        $r = $rx.Next(200)
        if ($r -and $r[1] -eq 0xFF -and ($r[2] -eq $req[2] -or $r[2] -eq 0x8F)) { return ,$r }
    }
    return $null
}
function SlotInfo {
    $p = Reg ([byte[]](0x10,0xFF,0x83,0xB5,0x20,0,0))
    $n = Reg ([byte[]](0x10,0xFF,0x83,0xB5,0x40,0,0))
    if ($p -and $p[2] -eq 0x83) {
        $name = if ($n -and $n[2] -eq 0x83) { [Text.Encoding]::ASCII.GetString($n, 6, $n[5]) } else { '?' }
        "Slot 1: wpid 0x{0:X2}{1:X2}  name '{2}'" -f $p[7], $p[8], $name
    } else { "Slot 1: empty ({0})" -f [HidppReceiver]::Hex($p) }
}

try {
    Write-Host ""
    Write-Host "Before: $(SlotInfo)"
    Write-Host ""
    Write-Host "STEP 1: Unplug the USB cable from the G903 and switch the mouse OFF (switch on the underside)." -ForegroundColor Yellow
    Read-Host  "        Press Enter when it's off"

    for ($attempt = 1; $attempt -le 2; $attempt++) {
        $r = Reg ([byte[]](0x10,0xFF,0x80,0xB2,0x01,0x00,0x00))   # open pairing lock, default timeout
        if (-not $r) { throw "No reply to open-lock request" }
        if ($r[2] -eq 0x8F -and $r[5] -eq 0x05) {
            # 0x05 = too many devices: this receiver holds one device, so drop the old (broken) mouse first
            Write-Host "Receiver is full - unpairing the old (broken) mouse from slot 1..." -ForegroundColor Yellow
            $u = Reg ([byte[]](0x10,0xFF,0x80,0xB2,0x03,0x01,0x00))
            Write-Host ("   unpair reply " + [HidppReceiver]::Hex($u))
            if (-not $u -or $u[2] -eq 0x8F) { throw "Receiver refused to unpair slot 1" }
            Start-Sleep -Milliseconds 500
            Write-Host "   now: $(SlotInfo)"
            $r = Reg ([byte[]](0x10,0xFF,0x80,0xB2,0x01,0x00,0x00))
            if (-not $r) { throw "No reply to open-lock request" }
        }
        if ($r[2] -eq 0x8F) { throw ("Receiver rejected open-lock: " + [HidppReceiver]::Hex($r)) }

        Write-Host ""
        Write-Host "STEP 2: Pairing window is OPEN. Switch the G903 ON now (cable stays unplugged)." -ForegroundColor Green
        $connected = $false; $lockError = $null
        $deadline = (Get-Date).AddSeconds(45)
        while ((Get-Date) -lt $deadline) {
            $m = $rx.Next(500)
            if (-not $m) { continue }
            Write-Host ("   rx " + [HidppReceiver]::Hex($m)) -ForegroundColor DarkGray
            if ($m[0] -eq 0x10 -and $m[2] -eq 0x41) {
                $linked = -not ($m[4] -band 0x40)
                Write-Host ("   device on slot {0}: wpid 0x{1:X2}{2:X2}, link {3}" -f $m[1], $m[6], $m[5], $(if ($linked) {'UP'} else {'down'}))
                if ($linked) { $connected = $true }
            }
            if ($m[0] -eq 0x10 -and $m[2] -eq 0x4A -and -not ($m[3] -band 1)) { $lockError = $m[4]; break }
        }
        if ($lockError -eq 3 -and $attempt -eq 1) {
            Write-Host "Receiver is full - unpairing the old (broken) mouse from slot 1 and retrying..." -ForegroundColor Yellow
            $u = Reg ([byte[]](0x10,0xFF,0x80,0xB2,0x03,0x01,0x00))
            Write-Host ("   unpair reply " + [HidppReceiver]::Hex($u))
            Write-Host "Switch the mouse OFF again." -ForegroundColor Yellow
            Read-Host  "Press Enter when it's off"
            continue
        }
        break
    }

    Write-Host ""
    switch ($lockError) {
        0       { Write-Host "Pairing lock closed normally." }
        1       { Write-Host "Pairing window timed out (mouse not seen)." -ForegroundColor Red }
        $null   { Write-Host "Pairing window still open after 45 s; closing it." -ForegroundColor Red
                  $null = Reg ([byte[]](0x10,0xFF,0x80,0xB2,0x02,0x00,0x00)) }
        default { Write-Host ("Pairing lock closed with error code {0}." -f $lockError) -ForegroundColor Red }
    }
    Write-Host "After:  $(SlotInfo)"
    if ($connected) { Write-Host "SUCCESS - move the mouse; it should work through the dongle now." -ForegroundColor Green }
    else { Write-Host "No link-up notification seen. Try moving the mouse anyway; if it doesn't work, rerun this script." -ForegroundColor Yellow }
} finally { $rx.Dispose() }