#requires -Version 7.0
[CmdletBinding()]
param(
    [ValidateSet('Check', 'Install', 'Restore')]
    [string]$Action = 'Check',
    [Parameter(Mandatory=$true)]
    [ValidateNotNullOrEmpty()]
    [string[]]$GameDirectory
)

$ErrorActionPreference = 'Stop'
$originalHash = '8F90A4A3856540CB97D03CA07B4BB10B7A08F7B4AB3C524BE2BEC1AFDD29FECA'
$patchedHash = '62B2079A988D23EB251D4E83366AC04068A6F47E0D38EFE92A76DF022826F9F0'
$offset = 0x115F0
$originalCode = [Convert]::FromHexString('4885C97403895104C3CCCCCCCCCCCCCC')
$patchedCode = [Convert]::FromHexString('4885C97407C7410400000000C3CCCCCC')

function Get-BytesHash([byte[]]$Bytes) {
    [Convert]::ToHexString([Security.Cryptography.SHA256]::HashData($Bytes))
}

if ($Action -ne 'Check' -and (Get-Process -Name 'oriwotw' -ErrorAction SilentlyContinue)) {
    throw '请先退出所有奥日 2 游戏窗口，再安装或还原补丁。'
}

# Preflight every selected directory before any mutation. Unknown builds,
# unrelated modifications and conflicting backups are never overwritten.
$plans = foreach ($directory in $GameDirectory) {
    $root = (Resolve-Path -LiteralPath $directory).Path
    $target = Join-Path $root 'oriwotw_Data\Plugins\AkSoundEngine.dll'
    $backup = $target + '.before-ori-affinity-fix'
    $bytes = [IO.File]::ReadAllBytes($target)
    $hash = Get-BytesHash $bytes
    if ($hash -notin @($originalHash, $patchedHash)) {
        throw "文件版本或内容不匹配，未修改：$target；SHA256=$hash"
    }
    if (Test-Path -LiteralPath $backup) {
        if ((Get-FileHash -LiteralPath $backup -Algorithm SHA256).Hash -ne $originalHash) {
            throw "现有备份不匹配，未覆盖：$backup"
        }
    }
    if ($Action -eq 'Restore' -and $hash -eq $patchedHash -and -not (Test-Path -LiteralPath $backup)) {
        throw "找不到经过校验的原文件备份，无法还原：$backup"
    }
    if ($hash -eq $originalHash) {
        for ($i = 0; $i -lt $originalCode.Length; $i++) {
            if ($bytes[$offset + $i] -ne $originalCode[$i]) { throw '原始指令校验失败。' }
        }
        $candidate = [byte[]]$bytes.Clone()
        [Array]::Copy($patchedCode, 0, $candidate, $offset, $patchedCode.Length)
        if ((Get-BytesHash $candidate) -ne $patchedHash) { throw '补丁结果校验失败。' }
    } else {
        $candidate = $bytes
    }
    [pscustomobject]@{ Root=$root; Target=$target; Backup=$backup; Hash=$hash; Candidate=$candidate }
}

foreach ($plan in $plans) {
    if ($Action -eq 'Check') {
        [pscustomobject]@{
            Directory=$plan.Root
            State=if ($plan.Hash -eq $patchedHash) { '已安装补丁' } else { '原版，符合补丁要求' }
            SHA256=$plan.Hash
            BackupExists=(Test-Path -LiteralPath $plan.Backup)
        }
        continue
    }
    if ($Action -eq 'Install' -and $plan.Hash -eq $patchedHash) {
        Write-Host "已安装，无需重复修改：$($plan.Root)"
        continue
    }
    if ($Action -eq 'Restore' -and $plan.Hash -eq $originalHash) {
        Write-Host "已经是原文件：$($plan.Root)"
        continue
    }
    if ($Action -eq 'Install') {
        if (-not (Test-Path -LiteralPath $plan.Backup)) {
            [IO.File]::Copy($plan.Target, $plan.Backup, $false)
        }
        if ((Get-FileHash -LiteralPath $plan.Backup -Algorithm SHA256).Hash -ne $originalHash) {
            throw '备份验证失败；未覆盖游戏 DLL。'
        }
        $newBytes = $plan.Candidate
        $expected = $patchedHash
    } else {
        $newBytes = [IO.File]::ReadAllBytes($plan.Backup)
        $expected = $originalHash
    }
    # Detect changes made by another program since preflight.
    if ((Get-FileHash -LiteralPath $plan.Target -Algorithm SHA256).Hash -ne $plan.Hash) {
        throw "检查后文件发生变化，停止修改：$($plan.Target)"
    }
    if (Get-Process -Name 'oriwotw' -ErrorAction SilentlyContinue) {
        throw '游戏刚刚启动，已停止修改；请先退出游戏。'
    }
    $staging = $plan.Target + '.ori-fix-' + [Guid]::NewGuid().ToString('N') + '.tmp'
    try {
        $stream = [IO.File]::Open($staging, [IO.FileMode]::CreateNew, [IO.FileAccess]::Write, [IO.FileShare]::None)
        try { $stream.Write($newBytes); $stream.Flush($true) } finally { $stream.Dispose() }
        if ((Get-FileHash -LiteralPath $staging -Algorithm SHA256).Hash -ne $expected) {
            throw '临时文件验证失败，未覆盖游戏 DLL。'
        }
        [IO.File]::Move($staging, $plan.Target, $true)
        if ((Get-FileHash -LiteralPath $plan.Target -Algorithm SHA256).Hash -ne $expected) {
            throw '写入后的校验失败，请保留备份并停止启动游戏。'
        }
    } finally {
        if (Test-Path -LiteralPath $staging) { Remove-Item -LiteralPath $staging }
    }
    Write-Host "${Action} 成功：$($plan.Target)"
    Write-Host "原文件备份：$($plan.Backup)"
}