# SchOS launcher (Windows side).
#
# Why this exists: without it you have to hand-type a QEMU command line, and a
# hand-typed one drifts -- notably onto a stale fs.img, which boots to
# "fsinit: invalid file system" because the wrong disk is attached as hdb.
#
# The build no longer goes through WSL. WSL2 runs a real Linux kernel inside a
# Hyper-V VM, so it hard-requires virtualisation, and enabling that puts the
# Hyper-V hypervisor underneath the whole machine -- which makes VMware run
# nested on top of it and slows the box down permanently. Not a trade worth
# making for a build environment.
#
# Instead it builds natively: clang/lld cross-compile the kernel to bare-metal
# ELF, mingw-w64 builds the host tools, and Git Bash supplies make, perl, sed
# and dd. See the Toolchain section of the Makefile.
#
#   .\run.ps1              build (native) then boot, windowed
#   .\run.ps1 -NoBuild     boot whatever is already built
#   .\run.ps1 -Headless    no window; serial captured to build\serial.log
#   .\run.ps1 -Gdb         wait for a debugger on :26000 before executing

#   .\run.ps1 -SchFS       boot the ramdisk-root kernel with a SchFS volume
#                          attached as hdb; then run  cat /proc/schfs

param(
    [switch]$NoBuild,
    [switch]$Headless,
    [switch]$Gdb,
    [switch]$SchFS,
    [string]$Qemu   = "$env:USERPROFILE\scoop\apps\qemu\current\qemu-system-x86_64.exe"
)

$ErrorActionPreference = 'Stop'
$root = $PSScriptRoot

# The two images QEMU needs. These paths are the single source of truth --
# keep them in sync with the 'qemu' and 'qemu-schfs' targets in the Makefile.
$hda = Join-Path $root 'schos.img'
$hdb = if ($SchFS) { Join-Path $root 'build\schfs.img' }
       else        { Join-Path $root 'build\fs.img' }

if (-not $NoBuild) {
    Write-Host '==> building (native, no WSL)' -ForegroundColor Cyan

    # The three toolchain directories, prepended so the build sees them whether
    # or not the current shell happened to inherit them: scoop's shims (make),
    # mingw-w64 (host gcc), and LLVM (clang, ld.lld, llvm-objcopy/objdump).
    $bash = Join-Path $env:ProgramFiles 'Git\bin\bash.exe'
    if (-not (Test-Path $bash)) { throw "Git Bash not found at $bash" }
    $toolPath = @(
        "$env:USERPROFILE\scoop\shims"
        "$env:USERPROFILE\scoop\apps\mingw\current\bin"
        "$env:ProgramFiles\LLVM\bin"
    ) -join ';'
    $env:PATH = "$toolPath;$env:PATH"

    # -SchFS needs the ramdisk-root kernel: the root filesystem then comes out
    # of memory, which leaves device 1 free for the SchFS volume. Booting the
    # normal kernel with a SchFS disk as hdb would leave it with no root.
    $target = if ($SchFS) { 'make ramroot && make build/schfs.img' } else { 'make' }
    & $bash -lc "cd /d/DEV/SchOS && $target"
    if ($LASTEXITCODE -ne 0) { throw "build failed (exit $LASTEXITCODE)" }
}

foreach ($img in @($hda, $hdb)) {
    if (-not (Test-Path $img)) { throw "missing image: $img  (run without -NoBuild)" }
}

# Guard against the exact failure this script exists to prevent: booting against
# a stale or empty hdb. Each format has its own magic in its own place.
$fs = [System.IO.File]::OpenRead($hdb)
try {
    $buf = New-Object byte[] 4
    # v1: superblock in block 1 with BSIZE 1024, FSMAGIC 0x10203040.
    # SchFS: first uberblock in block 1 with SCHFS_BLKSIZE 4096, magic "SchF".
    $null = $fs.Seek($(if ($SchFS) { 4096 } else { 1024 }), 'Begin')
    $null = $fs.Read($buf, 0, 4)
} finally { $fs.Close() }

if ($SchFS) {
    # 0x53636846 little-endian on disk: 46 68 63 53  ("FhcS" byte order).
    if ($buf[0] -ne 0x46 -or $buf[1] -ne 0x68 -or $buf[2] -ne 0x63 -or $buf[3] -ne 0x53) {
        throw "$hdb is not a valid SchFS image (bad uberblock magic). Rebuild it: make build/schfs.img"
    }
} else {
    if ($buf[0] -ne 0x40 -or $buf[1] -ne 0x30 -or $buf[2] -ne 0x20 -or $buf[3] -ne 0x10) {
        throw "$hdb is not a valid SCHFS image (bad superblock magic). Rebuild it: rm -f build/fs.img && make"
    }
}

$qemuArgs = @(
    '-drive', "file=$hda,format=raw,index=0,media=disk"
    '-drive', "file=$hdb,format=raw,index=1,media=disk"
    '-m', '1G'
    '-smp', '2'
    '-cpu', 'qemu64,+rdtscp'
    '-machine', 'pc-i440fx-9.2'
)

if ($Headless) {
    $log = Join-Path $root 'build\serial.log'
    $qemuArgs += @('-display', 'none', '-serial', "file:$log")
    Write-Host "==> headless; serial -> $log" -ForegroundColor Cyan
} else {
    $qemuArgs += @('-vga', 'std', '-serial', 'stdio')
}

if ($Gdb) {
    $qemuArgs += @('-gdb', 'tcp::26000', '-S')
    Write-Host '==> paused for gdb on localhost:26000' -ForegroundColor Yellow
}

& $Qemu @qemuArgs