# SchOS launcher (Windows side).
#
# Why this exists: without it you hand-type a QEMU command line, and a
# hand-typed one drifts -- notably onto the wrong disk as hdb, which boots
# straight into a PSOGM reading "no SchFS volume on the root device".
#
# The build runs natively rather than 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: 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, and docs/building.md.
#
#   .\run.ps1              build 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
#
# There is no -SchFS switch. SchFS is the root filesystem now, not an extra
# volume to attach, so every boot is a SchFS boot.

param(
    [switch]$NoBuild,
    [switch]$Headless,
    [switch]$Gdb,
    [string]$Qemu
)

$ErrorActionPreference = 'Stop'
$root = $PSScriptRoot

if (-not $Qemu) {
    $found = Get-Command 'qemu-system-x86_64.exe' -ErrorAction SilentlyContinue
    if ($found) {
        $Qemu = $found.Source
    } else {
        $Qemu = Join-Path $env:USERPROFILE 'scoop/apps/qemu/current/qemu-system-x86_64.exe'
    }
}
if (-not (Test-Path $Qemu)) { throw "QEMU not found: $Qemu  (install it, or pass -Qemu <path>)" }

# The two images QEMU needs. Keep in sync with the 'qemu' target in the
# Makefile.
#
#   hda  the boot disk: bootblock, stage 2 and the kernel
#   hdb  the root filesystem, mounted as / by forkret()
#
# hdb was build/fs.img until SchFS became the root. Nothing builds fs.img on
# the default path any more, so the old default pointed at a file that no
# longer exists -- QEMU came up with no usable disk on device 1 and the kernel
# panicked with SCHFS_ROOT. That is the failure this script is supposed to
# prevent, so it is worth naming.
$hda = Join-Path $root 'schos.img'
$hdb = Join-Path $root 'build/schfs.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).
    $bashCandidates = @(
        (Join-Path $env:ProgramFiles 'Git/bin/bash.exe')
        (Join-Path ${env:ProgramFiles(x86)} 'Git/bin/bash.exe')
        (Join-Path $env:USERPROFILE 'scoop/apps/git/current/bin/bash.exe')
        (Join-Path $env:LOCALAPPDATA 'Programs/Git/bin/bash.exe')
    )
    $bash = $bashCandidates | Where-Object { $_ -and (Test-Path $_) } | Select-Object -First 1
    if (-not $bash) { throw "Git Bash not found; looked in:`n  $($bashCandidates -join "`n  ")" }

    $toolPath = @(
        "$env:USERPROFILE\scoop\shims"
        "$env:USERPROFILE\scoop\apps\mingw\current\bin"
        "$env:ProgramFiles\LLVM\bin"
    ) -join ';'
    $env:PATH = "$toolPath;$env:PATH"

    # The repo's own path, not a hardcoded one. This used to say
    # `cd /d/DEV/SchOS`, which survived the Schunix -> SchOS rename only by
    # luck and would break the moment the tree is cloned anywhere else.
    $posixRoot = ($root -replace '\\', '/') -replace '^([A-Za-z]):', '/$1'
    $posixRoot = $posixRoot.Substring(0, 2).ToLower() + $posixRoot.Substring(2)

    & $bash -lc "cd '$posixRoot' && make"
    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, or: make)"
    }
}

# Guard against the exact failure this script exists to prevent: booting
# against a stale, empty or wrong-format root disk. The first uberblock sits in
# block 1 at SCHFS_BLKSIZE 4096, and starts with the magic "SchF" -- stored
# little-endian, so the bytes on disk read 46 68 63 53.
$fs = [System.IO.File]::OpenRead($hdb)
try {
    $buf = New-Object byte[] 4
    $null = $fs.Seek(4096, 'Begin')
    $null = $fs.Read($buf, 0, 4)
} finally { $fs.Close() }

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 SchFS volume (bad uberblock magic: " +
           ('{0:x2} {1:x2} {2:x2} {3:x2}' -f $buf[0], $buf[1], $buf[2], $buf[3]) +
           ").`n  Rebuild it:  rm -f build/schfs.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 {
    # Both display devices, matching QEMU_DISPLAY in the Makefile: the
    # bootloader draws its splash through VBE in 16-bit real mode and there is
    # no virtio path that early, so stdvga carries the splash and the text
    # console while virtio-gpu is what the display class binds.
    $qemuArgs += @('-vga', 'std', '-device', 'virtio-gpu-pci', '-serial', 'stdio')
}

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

& $Qemu @qemuArgs