# Build TFS import xlsx from XML parts as a stored (uncompressed) ZIP.
# Pure in-process .NET byte APIs: no external processes, no assembly loading.
# Output file name uses ASCII+char trick to stay encoding-safe.
$ErrorActionPreference = 'Stop'

$parts = Join-Path $PSScriptRoot '_parts'
$outName = 'TFS' + [char]0x5BFC + [char]0x5165 + [char]0x6A21 + [char]0x677F + '.xlsx'
$out = Join-Path $PSScriptRoot $outName

# ---------- CRC32 (IEEE 802.3) ----------
$tbl = New-Object 'System.Int64[]' 256
for ($i = 0; $i -lt 256; $i++) {
    $c = [int64]$i
    for ($k = 0; $k -lt 8; $k++) {
        if (($c -band 1) -eq 1) { $c = (3988292384 -bxor ($c -shr 1)) } else { $c = ($c -shr 1) }
        $c = $c -band 4294967295
    }
    $tbl[$i] = $c
}

function Get-Crc32([byte[]]$data) {
    $crc = [int64]4294967295
    foreach ($b in $data) {
        $idx = [int](($crc -bxor [int64]$b) -band 255)
        $crc = ($tbl[$idx] -bxor ($crc -shr 8)) -band 4294967295
    }
    return ($crc -bxor 4294967295)
}

# ---------- entry list (source relative path, zip entry name) ----------
$entries = @(
    @{ src = '[Content_Types].xml';         zip = '[Content_Types].xml' },
    @{ src = '_rels\.rels';                 zip = '_rels/.rels' },
    @{ src = 'xl\workbook.xml';             zip = 'xl/workbook.xml' },
    @{ src = 'xl\_rels\workbook.xml.rels';  zip = 'xl/_rels/workbook.xml.rels' },
    @{ src = 'xl\styles.xml';               zip = 'xl/styles.xml' },
    @{ src = 'xl\worksheets\sheet1.xml';    zip = 'xl/worksheets/sheet1.xml' }
)

$ms = New-Object System.IO.MemoryStream
$central = New-Object System.Collections.ArrayList

foreach ($e in $entries) {
    $srcPath = Join-Path $parts $e['src']
    $bytes = [System.IO.File]::ReadAllBytes($srcPath)
    $nameBytes = [System.Text.Encoding]::ASCII.GetBytes([string]$e['zip'])
    $crc = Get-Crc32 $bytes
    $offset = $ms.Position

    $ms.Write([BitConverter]::GetBytes([uint32]0x04034b50), 0, 4)   # local header signature
    $ms.Write([BitConverter]::GetBytes([uint16]20), 0, 2)           # version needed
    $ms.Write([BitConverter]::GetBytes([uint16]0), 0, 2)            # flags
    $ms.Write([BitConverter]::GetBytes([uint16]0), 0, 2)            # method: stored
    $ms.Write([BitConverter]::GetBytes([uint16]0), 0, 2)            # mod time
    $ms.Write([BitConverter]::GetBytes([uint16]33), 0, 2)           # mod date 1980-01-01
    $ms.Write([BitConverter]::GetBytes([uint32]$crc), 0, 4)
    $ms.Write([BitConverter]::GetBytes([uint32]$bytes.Length), 0, 4)
    $ms.Write([BitConverter]::GetBytes([uint32]$bytes.Length), 0, 4)
    $ms.Write([BitConverter]::GetBytes([uint16]$nameBytes.Length), 0, 2)
    $ms.Write([BitConverter]::GetBytes([uint16]0), 0, 2)            # extra len
    $ms.Write($nameBytes, 0, $nameBytes.Length)
    $ms.Write($bytes, 0, $bytes.Length)

    [void]$central.Add(@{ name = $nameBytes; crc = $crc; size = $bytes.Length; offset = $offset })
}

# ---------- central directory ----------
$cdStart = $ms.Position
foreach ($c in $central) {
    $ms.Write([BitConverter]::GetBytes([uint32]0x02014b50), 0, 4)   # central header signature
    $ms.Write([BitConverter]::GetBytes([uint16]20), 0, 2)           # made by
    $ms.Write([BitConverter]::GetBytes([uint16]20), 0, 2)           # version needed
    $ms.Write([BitConverter]::GetBytes([uint16]0), 0, 2)            # flags
    $ms.Write([BitConverter]::GetBytes([uint16]0), 0, 2)            # method
    $ms.Write([BitConverter]::GetBytes([uint16]0), 0, 2)            # time
    $ms.Write([BitConverter]::GetBytes([uint16]33), 0, 2)           # date
    $ms.Write([BitConverter]::GetBytes([uint32]$c['crc']), 0, 4)
    $ms.Write([BitConverter]::GetBytes([uint32]$c['size']), 0, 4)
    $ms.Write([BitConverter]::GetBytes([uint32]$c['size']), 0, 4)
    $ms.Write([BitConverter]::GetBytes([uint16]$c['name'].Length), 0, 2)
    $ms.Write([BitConverter]::GetBytes([uint16]0), 0, 2)            # extra len
    $ms.Write([BitConverter]::GetBytes([uint16]0), 0, 2)            # comment len
    $ms.Write([BitConverter]::GetBytes([uint16]0), 0, 2)            # disk start
    $ms.Write([BitConverter]::GetBytes([uint16]0), 0, 2)            # internal attrs
    $ms.Write([BitConverter]::GetBytes([uint32]0), 0, 4)            # external attrs
    $ms.Write([BitConverter]::GetBytes([uint32]$c['offset']), 0, 4)
    $ms.Write($c['name'], 0, $c['name'].Length)
}
$cdSize = $ms.Position - $cdStart

# ---------- end of central directory ----------
$ms.Write([BitConverter]::GetBytes([uint32]0x06054b50), 0, 4)
$ms.Write([BitConverter]::GetBytes([uint16]0), 0, 2)               # disk number
$ms.Write([BitConverter]::GetBytes([uint16]0), 0, 2)               # cd disk
$ms.Write([BitConverter]::GetBytes([uint16]$central.Count), 0, 2)
$ms.Write([BitConverter]::GetBytes([uint16]$central.Count), 0, 2)
$ms.Write([BitConverter]::GetBytes([uint32]$cdSize), 0, 4)
$ms.Write([BitConverter]::GetBytes([uint32]$cdStart), 0, 4)
$ms.Write([BitConverter]::GetBytes([uint16]0), 0, 2)               # comment len

[System.IO.File]::WriteAllBytes($out, $ms.ToArray())
$ms.Dispose()

Write-Output ('CREATED ' + $out + ' size=' + (New-Object System.IO.FileInfo $out).Length)