<#
.SYNOPSIS
    Windows equivalent of build_core.sh - builds the Go core binaries.

.DESCRIPTION
    Builds the Android client for every shipped ABI and the Linux client/servers.

    arm64-v8a builds with CGO disabled and needs no NDK. The other Android ABIs
    do: `GOOS=android` requires external linking for arm, amd64 and 386, so an
    NDK toolchain is located automatically. If none is found those ABIs are
    skipped with a warning rather than failing the build - the APK is still
    installable on 64-bit ARM, which is the overwhelming majority of devices.

.EXAMPLE
    .\build_core.ps1
    .\build_core.ps1 -ClientOnly
    .\build_core.ps1 -Abis arm64-v8a,armeabi-v7a
#>
[CmdletBinding()]
param(
    # Only build the Android client (skip the Linux client and servers).
    [switch]$ClientOnly,
    # Root of the APK's lib directory; per-ABI subdirectories are created here.
    [string]$AndroidLibRoot,
    # Which Android ABIs to build.
    [string[]]$Abis = @('arm64-v8a', 'armeabi-v7a', 'x86_64'),
    # NDK root; auto-detected from the SDK when omitted.
    [string]$NdkRoot,
    # Minimum Android API the native cores are built for.
    [int]$MinApi = 24,
    [string]$GoBin = $(if ($env:GO_BIN) { $env:GO_BIN } else { 'go' })
)

$ErrorActionPreference = 'Stop'
$Root = $PSScriptRoot
if (-not $AndroidLibRoot) { $AndroidLibRoot = Join-Path $Root 'android\lib' }

function Invoke-Go {
    param([hashtable]$Env, [string[]]$GoArgs)
    $saved = @{}
    foreach ($k in $Env.Keys) {
        $saved[$k] = [Environment]::GetEnvironmentVariable($k)
        [Environment]::SetEnvironmentVariable($k, $Env[$k])
    }
    try {
        & $GoBin @GoArgs
        if ($LASTEXITCODE -ne 0) { throw "go build failed (exit $LASTEXITCODE)" }
    } finally {
        foreach ($k in $saved.Keys) { [Environment]::SetEnvironmentVariable($k, $saved[$k]) }
    }
}

# Locate an NDK llvm toolchain bin directory, newest first.
function Find-NdkBin {
    param([string]$Explicit)
    $roots = @()
    if ($Explicit) { $roots += $Explicit }
    if ($env:ANDROID_NDK_ROOT) { $roots += $env:ANDROID_NDK_ROOT }
    if ($env:ANDROID_NDK_HOME) { $roots += $env:ANDROID_NDK_HOME }
    foreach ($sdk in $env:ANDROID_SDK_ROOT, $env:ANDROID_HOME, "$env:LOCALAPPDATA\Android\Sdk") {
        if ($sdk -and (Test-Path (Join-Path $sdk 'ndk'))) {
            $roots += (Get-ChildItem (Join-Path $sdk 'ndk') -Directory |
                       Sort-Object { try { [version]$_.Name } catch { [version]'0.0.0' } } -Descending |
                       ForEach-Object { $_.FullName })
        }
    }
    foreach ($r in $roots) {
        if (-not $r) { continue }
        $bin = Join-Path $r 'toolchains\llvm\prebuilt\windows-x86_64\bin'
        if (Test-Path $bin) { return $bin }
    }
    return $null
}

# ABI -> (GOARCH, GOARM, clang triple prefix)
$abiSpec = @{
    'arm64-v8a'   = @{ arch = 'arm64'; arm = '';  cc = 'aarch64-linux-android' }
    'armeabi-v7a' = @{ arch = 'arm';   arm = '7'; cc = 'armv7a-linux-androideabi' }
    'x86_64'      = @{ arch = 'amd64'; arm = '';  cc = 'x86_64-linux-android' }
    'x86'         = @{ arch = '386';   arm = '';  cc = 'i686-linux-android' }
}

$go = Get-Command $GoBin -ErrorAction SilentlyContinue
if (-not $go) { throw "Go compiler not found. Install from https://go.dev/dl/ or set -GoBin." }

$ndkBin = Find-NdkBin $NdkRoot
New-Item -ItemType Directory -Force -Path "$Root\bin" | Out-Null
Push-Location "$Root\core"
try {
    $ldflags = '-ldflags=-s -w'
    $built = @()

    foreach ($abi in $Abis) {
        if (-not $abiSpec.ContainsKey($abi)) { Write-Warning "unknown ABI $abi, skipping"; continue }
        $spec = $abiSpec[$abi]
        $outDir = Join-Path $AndroidLibRoot $abi
        $out = Join-Path $outDir 'libdragontcp_client.so'

        # arm64 links internally; everything else needs the NDK's clang.
        $env = @{ GOOS = 'android'; GOARCH = $spec.arch }
        if ($spec.arm) { $env['GOARM'] = $spec.arm }
        if ($abi -eq 'arm64-v8a') {
            $env['CGO_ENABLED'] = '0'
        } else {
            if (-not $ndkBin) {
                Write-Warning "[core] $abi skipped: no NDK found (set -NdkRoot or ANDROID_NDK_ROOT)"
                continue
            }
            $cc = Join-Path $ndkBin ("{0}{1}-clang.cmd" -f $spec.cc, $MinApi)
            if (-not (Test-Path $cc)) {
                Write-Warning "[core] $abi skipped: $cc not found"
                continue
            }
            $env['CGO_ENABLED'] = '1'
            $env['CC'] = $cc
        }

        Write-Host "[core] Android $abi client..." -ForegroundColor Cyan
        New-Item -ItemType Directory -Force -Path $outDir | Out-Null
        Invoke-Go $env @('build', '-trimpath', $ldflags, '-o', $out, './cmd/dragontcp-client')
        $built += $abi
    }

    if (-not $built) { throw 'No Android ABI was built.' }
    Write-Host "[core] Android ABIs: $($built -join ', ')" -ForegroundColor Green

    # Remove stale ABI directories so the APK never ships an out-of-date core.
    if (Test-Path $AndroidLibRoot) {
        foreach ($dir in Get-ChildItem $AndroidLibRoot -Directory) {
            if ($built -notcontains $dir.Name) {
                Write-Warning "[core] removing stale $($dir.Name) native library"
                Remove-Item $dir.FullName -Recurse -Force
            }
        }
    }

    if (-not $ClientOnly) {
        Write-Host '[core] Linux AMD64 client...' -ForegroundColor Cyan
        Invoke-Go @{ CGO_ENABLED = '0'; GOOS = 'linux'; GOARCH = 'amd64' } `
            @('build', '-trimpath', $ldflags, '-o', "$Root\bin\dragontcp-hybrid-client-linux-amd64", './cmd/dragontcp-client')

        Write-Host '[core] Linux AMD64 server...' -ForegroundColor Cyan
        Invoke-Go @{ CGO_ENABLED = '0'; GOOS = 'linux'; GOARCH = 'amd64' } `
            @('build', '-trimpath', $ldflags, '-o', "$Root\bin\dragontcp-hybrid-server-linux-amd64", './cmd/dragontcp-server')

        Write-Host '[core] Linux ARM64 server...' -ForegroundColor Cyan
        Invoke-Go @{ CGO_ENABLED = '0'; GOOS = 'linux'; GOARCH = 'arm64' } `
            @('build', '-trimpath', $ldflags, '-o', "$Root\bin\dragontcp-hybrid-server-linux-arm64", './cmd/dragontcp-server')
    }
} finally {
    Pop-Location
}

Write-Host 'Core build complete.' -ForegroundColor Green