param(
    [Parameter(Mandatory = $true)]
    [string]$PackagePath,
    [string]$ProgramRoot = "",
    [string]$DataRoot = "",
    [switch]$SkipBackup = $false,
    [switch]$NoStart = $false
)

$ErrorActionPreference = "Stop"
. "$PSScriptRoot\_common.ps1"

$prog = Get-NetxProgramRoot -Override $ProgramRoot
$data = Get-NetxDataRoot -ProgramRoot $prog -Override $DataRoot

if (-not (Test-Path $PackagePath)) {
    throw "package_not_found: $PackagePath"
}

$work = Join-Path $env:TEMP ("netx-update-" + [guid]::NewGuid().ToString("n"))
New-Item -ItemType Directory -Path $work -Force | Out-Null

try {
    Write-Host "==> Extracting update package"
    if ($PackagePath.ToLowerInvariant().EndsWith(".zip")) {
        Expand-Archive -Path $PackagePath -DestinationPath $work -Force
    } else {
        throw "unsupported_package: use a .zip built by build_release.ps1"
    }

    $src = $work
    # If zip has a single top-level folder, use it.
    $kids = @(Get-ChildItem -Path $work -Directory)
    if ($kids.Count -eq 1 -and (Test-Path (Join-Path $kids[0].FullName "version.json"))) {
        $src = $kids[0].FullName
    } elseif (-not (Test-Path (Join-Path $work "version.json"))) {
        $nested = Get-ChildItem -Path $work -Recurse -Filter "version.json" | Select-Object -First 1
        if ($nested) { $src = Split-Path -Parent $nested.FullName }
    }

    $newVerFile = Join-Path $src "version.json"
    if (-not (Test-Path $newVerFile)) {
        throw "version.json missing in package"
    }
    $newVer = (Get-Content -Raw $newVerFile | ConvertFrom-Json).version
    $oldVer = Get-NetxVersion -ProgramRoot $prog
    Write-Host "==> Updating $oldVer -> $newVer"

    if (-not $SkipBackup) {
        $stamp = Get-Date -Format "yyyyMMdd_HHmmss"
        $bak = Join-Path $data "backups\pre-update-$stamp"
        New-Item -ItemType Directory -Path $bak -Force | Out-Null
        $envFile = Join-Path $data ".env"
        if (Test-Path $envFile) {
            Copy-Item $envFile (Join-Path $bak ".env")
        }
        Write-Host "==> Backup marker: $bak (data/pgdata left in place; optional pg_dump not run)"
    }

    Write-Host "==> Stopping services"
    & powershell -ExecutionPolicy Bypass -File (Join-Path $PSScriptRoot "stop_netx_app.ps1") `
        -ProgramRoot $prog -DataRoot $data

    # Replace program layers only — never wipe data root.
    $replaceDirs = @("netx_api", "alembic", "web", "packaging", "scripts", "postgres", "packages")
    foreach ($name in $replaceDirs) {
        $from = Join-Path $src $name
        $to = Join-Path $prog $name
        if (-not (Test-Path $from)) { continue }
        Write-Host "==> Replacing $name"
        if (Test-Path $to) {
            Remove-Item -Recurse -Force $to
        }
        Copy-Item -Path $from -Destination $to -Recurse -Force
    }
    foreach ($f in @("requirements.txt", "pyproject.toml", "alembic.ini", "version.json", "README.md", "LICENSE")) {
        $from = Join-Path $src $f
        if (Test-Path $from) {
            Copy-Item -Path $from -Destination (Join-Path $prog $f) -Force
        }
    }
    # Optional runtime / .venv shipped in package
    if (Test-Path (Join-Path $src "runtime")) {
        $rt = Join-Path $prog "runtime"
        if (Test-Path $rt) { Remove-Item -Recurse -Force $rt }
        Copy-Item -Path (Join-Path $src "runtime") -Destination $rt -Recurse -Force
    }
    if (Test-Path (Join-Path $src ".venv")) {
        Write-Host "==> Replacing .venv from package"
        $venvTo = Join-Path $prog ".venv"
        if (Test-Path $venvTo) { Remove-Item -Recurse -Force $venvTo }
        Copy-Item -Path (Join-Path $src ".venv") -Destination $venvTo -Recurse -Force
    }

    Write-Host "==> Update files applied" -ForegroundColor Green
    if (-not $NoStart) {
        & powershell -ExecutionPolicy Bypass -File (Join-Path $PSScriptRoot "start_netx_app.ps1") `
            -ProgramRoot $prog -DataRoot $data -SkipBrowser
    }
} finally {
    if (Test-Path $work) {
        Remove-Item -Recurse -Force $work -ErrorAction SilentlyContinue
    }
}