# Shared helpers for the sequential Nova128 editor/compiler launchers (E07-S02).
#   Import-Module (Join-Path $PSScriptRoot "lib\Nova128Launcher.psm1") -Force

$script:ViceBin = "C:\Program Files\GTK3VICE-3.10-win64\bin"

function Get-Nova128ViceTool([string]$Name) {
    $path = Join-Path $script:ViceBin "$Name.exe"
    if (-not (Test-Path -LiteralPath $path)) { throw "$Name.exe not found at $path" }
    return $path
}

# One writable session per image directory. The lock holds the owning PID and
# kind; a lock whose process is gone is stale and is replaced.
function Enter-Nova128ImageSession {
    param(
        [Parameter(Mandatory)][string]$Image,
        [Parameter(Mandatory)][ValidateSet("editor", "compiler")][string]$Kind
    )
    $folder = Split-Path ([IO.Path]::GetFullPath($Image)) -Parent
    New-Item -ItemType Directory -Force -Path $folder | Out-Null
    $lockPath = Join-Path $folder ".newlang-session.lock"

    if (Test-Path -LiteralPath $lockPath) {
        # A live holder keeps the file open without sharing, so even reading it
        # can fail. That is the same answer as a readable live PID.
        $text = ""
        try {
            $text = Get-Content -Raw -LiteralPath $lockPath
        } catch {
            throw "another Nova128 session already holds $Image"
        }
        $owner = 0
        $ownerKind = "another"
        if ($text -match '(?m)^(\d+)\s+(\S+)') {
            $owner = [int]$Matches[1]
            $ownerKind = $Matches[2]
        }
        $alive = $owner -gt 0 -and $null -ne (Get-Process -Id $owner -ErrorAction SilentlyContinue)
        if ($alive) {
            throw "the $ownerKind session (pid $owner) still owns $Image; close it before starting another"
        }
        Remove-Item -LiteralPath $lockPath -Force
    }

    try {
        $stream = [IO.File]::Open($lockPath, [IO.FileMode]::CreateNew,
            [IO.FileAccess]::Write, [IO.FileShare]::None)
    } catch {
        throw "another Nova128 session already holds $Image"
    }
    $writer = [IO.StreamWriter]::new($stream)
    $writer.WriteLine("$PID $Kind")
    $writer.Flush()
    return [pscustomobject]@{ Path = $lockPath; Stream = $stream; Writer = $writer
        Image = $Image; Kind = $Kind }
}

function Exit-Nova128ImageSession {
    param([Parameter(Mandatory)]$Session)
    try {
        $Session.Writer.Dispose()
        $Session.Stream.Dispose()
    } finally {
        if (Test-Path -LiteralPath $Session.Path) {
            Remove-Item -LiteralPath $Session.Path -Force
        }
        if ($Session.Image) {
            Wait-Nova128ImageFlush -Image $Session.Image
        }
    }
}

# The emulator has exited, but DOS writes may still be in flight. Return only
# when the image can be opened exclusively.
function Wait-Nova128ImageFlush {
    param(
        [Parameter(Mandatory)][string]$Image,
        [int]$TimeoutSeconds = 30
    )
    if (-not (Test-Path -LiteralPath $Image)) { return }
    $deadline = [DateTime]::UtcNow.AddSeconds($TimeoutSeconds)
    while ($true) {
        try {
            $stream = [IO.File]::Open($Image, [IO.FileMode]::Open,
                [IO.FileAccess]::Read, [IO.FileShare]::None)
            $stream.Dispose()
            return
        } catch {
            if ([DateTime]::UtcNow -ge $deadline) {
                throw "the emulator exited but $Image is still locked (image not flushed)"
            }
            Start-Sleep -Milliseconds 200
        }
    }
}

# Start an emulator and wait for it to exit. Autostart uses the host program
# path, so the program is deterministic; the disk image stays attached for the
# session's own reads and writes.
# Write one file into a disk image and prove it appears in the directory.
function Add-Nova128DiskFile {
    param(
        [Parameter(Mandatory)][string]$Image,
        [Parameter(Mandatory)][string]$HostPath,
        [Parameter(Mandatory)][string]$DiskName,
        [ValidateSet("prg", "seq")][string]$Type = "prg"
    )
    $c1541 = Get-Nova128ViceTool "c1541"
    if (-not (Test-Path -LiteralPath $HostPath -PathType Leaf)) {
        throw "file not found: $HostPath"
    }
    $destination = if ($Type -eq "seq") { "$DiskName,s" } else { $DiskName }
    $output = (& $c1541 $Image -write $HostPath $destination 2>&1) -join "`n"
    if ($LASTEXITCODE -ne 0) {
        throw "c1541 could not write '$DiskName' to $Image`n$output"
    }
    $listing = (& $c1541 $Image -list 2>&1) -join "`n"
    $pattern = '(?im)"' + [regex]::Escape($DiskName) + '"\s+' + $Type
    if ($listing -notmatch $pattern) {
        throw "$DiskName ($Type) is missing from $Image after writing"
    }
}

function Invoke-Nova128Emulator {
    param(
        [Parameter(Mandatory)][ValidateSet("x64sc", "x128")][string]$Emulator,
        [Parameter(Mandatory)][string]$Program,
        [string]$DiskImage,
        [string]$Screenshot,
        [int]$LimitCycles = 0,
        [switch]$Warp,
        [switch]$EightyColumn,
        [switch]$ProgramOnDisk
    )
    $tool = Get-Nova128ViceTool $Emulator
    $workingDirectory = $null
    $autostart = $Program
    if ($ProgramOnDisk) {
        # The editor takes its write device from the disk it was loaded from.
        # Autostarting the copy on the session disk is what makes its saves
        # reach the image; a host-injected program has no such device.
        if (-not $DiskImage) { throw "a disk-resident program needs -DiskImage" }
        $autostart = [IO.Path]::GetFileName($DiskImage) + ":" + $Program
        $workingDirectory = Split-Path ([IO.Path]::GetFullPath($DiskImage)) -Parent
    } elseif (-not (Test-Path -LiteralPath $Program)) {
        throw "program not found: $Program"
    }

    $arguments = @()
    if ($DiskImage) {
        if (-not (Test-Path -LiteralPath $DiskImage)) {
            throw "disk image not found: $DiskImage"
        }
        $arguments += @("-drive8type", "1581", "-drive8truedrive", "-8",
            ('"' + $DiskImage + '"'))
    }
    if ($EightyColumn) { $arguments += "-80col" }
    $arguments += @("-autostart", ('"' + $autostart + '"'), "-autostart-warp",
        "-sounddev", "dummy")
    if ($Warp) { $arguments += "-warp" }
    if ($LimitCycles -gt 0) { $arguments += @("-limitcycles", "$LimitCycles") }
    if ($Screenshot) {
        if (Test-Path -LiteralPath $Screenshot) {
            Remove-Item -LiteralPath $Screenshot -Force
        }
        # x64sc's plain -exitscreenshot is the VIC-II screen. On x128 the
        # 80-column editor draws on the VDC, which only the plain option
        # captures; -exitscreenshotvicii would save a blank 40-column screen.
        $shotOption = if ($Emulator -eq "x64sc" -or $EightyColumn) {
            "-exitscreenshot"
        } else {
            "-exitscreenshotvicii"
        }
        $arguments += @($shotOption, ('"' + $Screenshot + '"'))
    }

    Write-Host ("launching {0} with {1}" -f $Emulator, $autostart)
    $startArgs = @{ FilePath = $tool; ArgumentList = $arguments; PassThru = $true; Wait = $true }
    if ($workingDirectory) { $startArgs.WorkingDirectory = $workingDirectory }
    $process = Start-Process @startArgs
    if ($Screenshot -and -not (Test-Path -LiteralPath $Screenshot)) {
        throw "$Emulator did not create the exit screenshot $Screenshot"
    }
    if ($DiskImage) { Wait-Nova128ImageFlush -Image $DiskImage }
    return $process.ExitCode
}

Export-ModuleMember -Function Get-Nova128ViceTool, Enter-Nova128ImageSession,
    Exit-Nova128ImageSession, Wait-Nova128ImageFlush, Add-Nova128DiskFile,
    Invoke-Nova128Emulator