param(
    [Parameter(Mandatory = $true)]
    [string]$ProjectDir,
    [string]$GowinRoot = ""
)

$ErrorActionPreference = "Stop"

if (-not $GowinRoot) {
    $GowinRoot = Join-Path (Split-Path (Split-Path $PSScriptRoot -Parent) -Parent) `
        "tool-chain\Gowin\Gowin_V1.9.11.03_Education_x64"
    if (-not (Test-Path $GowinRoot)) {
        $GowinRoot = "C:\Users\Administrator\Documents\fpga\tool-chain\Gowin\Gowin_V1.9.11.03_Education_x64"
    }
}

$ProjectDir = (Resolve-Path $ProjectDir).Path
$gwSh = Join-Path $GowinRoot "IDE\bin\gw_sh.exe"
$buildTcl = Join-Path $ProjectDir "build.tcl"

if (-not (Test-Path $gwSh)) { throw "gw_sh.exe not found: $gwSh" }
if (-not (Test-Path $buildTcl)) { throw "build.tcl not found: $buildTcl" }

$env:PATH = "$(Join-Path $GowinRoot 'IDE\bin');$(Join-Path $GowinRoot 'Programmer\bin');$env:PATH"

Write-Host "Building: $ProjectDir"
Push-Location $ProjectDir
try {
    cmd /c "type build.tcl | gw_sh.exe"
    if ($LASTEXITCODE -ne 0) { throw "gw_sh failed with exit $LASTEXITCODE" }
} finally {
    Pop-Location
}

$fs = Get-ChildItem (Join-Path $ProjectDir "impl\pnr\*.fs") -ErrorAction SilentlyContinue |
    Sort-Object LastWriteTime -Descending | Select-Object -First 1
if (-not $fs) { throw "No bitstream (.fs) under impl\pnr" }

Write-Host "OK bitstream: $($fs.FullName)"
return $fs.FullName