function Get-ManagedManifestPath {
    param([Parameter(Mandatory=$true)][string]$Destination)
    return (Join-Path $Destination '.ai-config-manifest.tsv')
}

function Get-ManagedBackupRoot {
    param([Parameter(Mandatory=$true)][string]$Destination)
    if ((Split-Path $Destination -Leaf) -eq 'skills' -and (Split-Path (Split-Path $Destination -Parent) -Leaf) -eq '.agents') {
        return (Resolve-ManagedPath -Destination (Split-Path $Destination -Parent) -Relative '.ai-config-skill-backups')
    }
    return (Resolve-ManagedPath -Destination $Destination -Relative 'backups')
}

function Resolve-ManagedPath {
    param([Parameter(Mandatory=$true)][string]$Destination, [Parameter(Mandatory=$true)][string]$Relative)
    $parts = $Relative -split '/', 0, 'SimpleMatch'
    if ($Relative.StartsWith('/') -or $Relative.Contains('\') -or $Relative.Contains(':') -or $Relative.Contains("`t") -or $Relative.Contains("`r") -or $Relative.Contains("`n") -or @($parts | Where-Object { $_ -in @('', '.', '..') }).Count -gt 0) {
        throw "Invalid managed path: $Relative"
    }
    $target = $Destination
    foreach ($part in $parts) { $target = Join-Path $target $part }
    $probe = $target
    while ($true) {
        $item = Get-Item -LiteralPath $probe -Force -ErrorAction SilentlyContinue
        if ($item -and ($item.Attributes -band [IO.FileAttributes]::ReparsePoint)) { throw "Managed path contains a link: $probe" }
        if ($probe -eq $Destination) { break }
        $probe = Split-Path $probe -Parent
    }
    return $target
}

function Get-Sha256Hash {
    param([Parameter(Mandatory=$true)][string]$Path)
    # Lowercase to match sha256sum's output, since the manifest must be readable by
    # both this module and its Bash equivalent regardless of which one wrote it.
    return (Get-FileHash -LiteralPath $Path -Algorithm SHA256).Hash.ToLowerInvariant()
}

function Get-Sha256HashOfBytes {
    param([Parameter(Mandatory=$true)][AllowEmptyCollection()][byte[]]$Bytes)
    $sha256 = [System.Security.Cryptography.SHA256]::Create()
    try { return ([System.BitConverter]::ToString($sha256.ComputeHash($Bytes))).Replace('-', '').ToLowerInvariant() }
    finally { $sha256.Dispose() }
}

function Write-ManagedFileAtomically {
    param([Parameter(Mandatory=$true)][string]$Path,[Parameter(Mandatory=$true)][AllowEmptyCollection()][byte[]]$Bytes)
    $temporary = Join-Path (Split-Path $Path -Parent) ('.ai-config-write-' + [Guid]::NewGuid().ToString('N') + '.tmp')
    $backup = "$temporary.bak"
    try {
        [System.IO.File]::WriteAllBytes($temporary, $Bytes)
        if ([System.IO.File]::Exists($Path)) {
            [System.IO.File]::Replace($temporary, $Path, $backup)
        } else {
            [System.IO.File]::Move($temporary, $Path)
        }
    } finally {
        if ([System.IO.File]::Exists($temporary)) { [System.IO.File]::Delete($temporary) }
        if ([System.IO.File]::Exists($backup)) { [System.IO.File]::Delete($backup) }
    }
}

function Read-ManagedManifest {
    param([Parameter(Mandatory=$true)][string]$ManifestPath)
    $entries = @{}
    if (Test-Path -LiteralPath $ManifestPath) {
        # Lowercase to tolerate an older manifest written before hashes were normalized.
        Import-Csv -LiteralPath $ManifestPath -Delimiter ([char]9) | ForEach-Object {
            $null = Resolve-ManagedPath -Destination (Split-Path $ManifestPath -Parent) -Relative $_.path
            $entries[$_.path] = $_.sha256.ToLowerInvariant()
        }
    }
    return $entries
}

function Write-ManagedManifest {
    param([Parameter(Mandatory=$true)][string]$ManifestPath, [Parameter(Mandatory=$true)][hashtable]$Entries)
    $lines = @("path`tsha256")
    foreach ($path in ($Entries.Keys | Sort-Object)) { $lines += "$path`t$($Entries[$path])" }
    New-Item (Split-Path $ManifestPath -Parent) -ItemType Directory -Force | Out-Null
    # Windows PowerShell 5.1's -Encoding UTF8 always prepends a BOM, which Bash's plain
    # `read` would otherwise fold into the first field of the header line. Write UTF-8
    # without BOM and with LF line endings so either implementation can read the file
    # regardless of which one wrote it.
    $content = ($lines -join "`n") + "`n"
    Write-ManagedFileAtomically -Path $ManifestPath -Bytes ((New-Object System.Text.UTF8Encoding($false)).GetBytes($content))
}

function Enter-ManagedLock {
    param([Parameter(Mandatory=$true)][string]$Destination)
    New-Item $Destination -ItemType Directory -Force | Out-Null
    $lockPath = Join-Path $Destination '.ai-config.lock'
    $owner = "powershell $([Environment]::MachineName) $PID"
    foreach ($attempt in 1, 2) {
        try {
            $stream = [System.IO.File]::Open($lockPath, [System.IO.FileMode]::CreateNew, [System.IO.FileAccess]::Write, [System.IO.FileShare]::None)
            try { $bytes = [System.Text.Encoding]::UTF8.GetBytes("$owner`n"); $stream.Write($bytes, 0, $bytes.Length) } finally { $stream.Dispose() }
            return $lockPath
        } catch [System.IO.IOException] {
            $holder = @(([System.IO.File]::ReadAllText($lockPath)).Trim() -split ' ')
            # ponytail: only same-shell, same-host owners are checked for staleness; other stale locks need manual removal.
            $stale = $attempt -eq 1 -and $holder.Count -eq 3 -and $holder[0] -eq 'powershell' -and $holder[1] -eq [Environment]::MachineName -and -not (Get-Process -Id ([int]$holder[2]) -ErrorAction SilentlyContinue)
            if (-not $stale) { throw "Another installation or update holds $lockPath; wait for it to finish, or remove the file if no update is running." }
            [System.IO.File]::Delete($lockPath)
        }
    }
}

function Invoke-InstallOptions {
    param([Parameter(Mandatory=$true)][string[]]$Arguments, [byte[]]$Managed, [Parameter(Mandatory=$true)][string]$ErrorMessage)
    # Exchange content through UTF-8 files: Windows PowerShell pipes re-encode text by console code page.
    $outputPath = [System.IO.Path]::GetTempFileName()
    $managedPath = $null
    try {
        if ($null -ne $Managed) {
            $managedPath = [System.IO.Path]::GetTempFileName()
            [System.IO.File]::WriteAllBytes($managedPath, $Managed)
            $Arguments += @('--managed', $managedPath)
        }
        & python (Join-Path $PSScriptRoot 'install-options.py') @Arguments --output $outputPath
        if ($LASTEXITCODE -ne 0) { throw $ErrorMessage }
        return [System.IO.File]::ReadAllText($outputPath, (New-Object System.Text.UTF8Encoding($false)))
    } finally {
        Remove-Item -LiteralPath $outputPath -Force -ErrorAction SilentlyContinue
        if ($managedPath) { Remove-Item -LiteralPath $managedPath -Force -ErrorAction SilentlyContinue }
    }
}

function Sync-ManagedDestination {
    <#
    .SYNOPSIS
        Runs Invoke-ManagedSync while holding the destination lock, so parallel
        installs or updates cannot interleave writes to the same destination.
    #>
    param(
        [Parameter(Mandatory=$true)][string]$Source,
        [Parameter(Mandatory=$true)][string]$Destination,
        [Parameter(Mandatory=$true)][string]$Stamp,
        [string]$AiConfigRoot,
        [string]$ShellCommand,
        [string]$PowerShellCommand,
        [string]$ClaudeConcurrency = '5',
        [bool]$FlashbangEnabled = $true,
        [bool]$StatusLineEnabled = $true,
        [bool]$SemanticRetrievalEnabled = $true,
        [switch]$DryRun,
        [switch]$Summary
    )
    if ($DryRun) { return Invoke-ManagedSync @PSBoundParameters }
    $lockPath = Enter-ManagedLock $Destination
    try { Invoke-ManagedSync @PSBoundParameters } finally { [System.IO.File]::Delete($lockPath) }
}

function Invoke-ManagedSync {
    <#
    .SYNOPSIS
        Installs one generated source tree into a destination directory, tracking
        every installed file in a manifest so a later run can detect files this
        setup previously managed that were since removed from the source (stale)
        or changed on disk by the user (locally modified), without ever touching
        a file it never installed.
    #>
    param(
        [Parameter(Mandatory=$true)][string]$Source,
        [Parameter(Mandatory=$true)][string]$Destination,
        [Parameter(Mandatory=$true)][string]$Stamp,
        [string]$AiConfigRoot,
        [string]$ShellCommand,
        [string]$PowerShellCommand,
        [string]$ClaudeConcurrency = '5',
        [bool]$FlashbangEnabled = $true,
        [bool]$StatusLineEnabled = $true,
        [bool]$SemanticRetrievalEnabled = $true,
        [switch]$DryRun,
        [switch]$Summary
    )
    if (-not $Summary) { Write-Output "SOURCE $Source -> $Destination" }
    $manifestPath = Get-ManagedManifestPath $Destination
    $null = Resolve-ManagedPath -Destination $Destination -Relative '.ai-config-manifest.tsv'
    $oldManifest = Read-ManagedManifest $manifestPath
    $newManifest = @{}
    $backupRoot = Get-ManagedBackupRoot $Destination
    $tally = @{ Created = 0; Updated = 0; Unchanged = 0; Removed = 0; Warned = 0 }
    $journalPath = Resolve-ManagedPath -Destination $Destination -Relative '.ai-config-transaction.json'
    if (Test-Path -LiteralPath $journalPath) {
        # An earlier run was interrupted after it started writing; undo its changes before syncing.
        $journal = [System.IO.File]::ReadAllText($journalPath, (New-Object System.Text.UTF8Encoding($false))) | ConvertFrom-Json
        if ($DryRun) {
            Write-Output "DRYRUN ROLLBACK $Destination $($journal.stamp)"
        } else {
            foreach ($entry in @($journal.files)) {
                $target = Resolve-ManagedPath -Destination $Destination -Relative $entry.path
                if ($entry.action -eq 'create') {
                    if (-not (Test-Path -LiteralPath $target)) { continue }
                    if ((Get-Sha256Hash $target) -eq "$($entry.sha256)".ToLowerInvariant()) { [System.IO.File]::Delete($target) }
                    else { Write-Output "WARN $target was created by an interrupted run and has changed since; it was left in place."; $tally.Warned++ }
                } elseif ($entry.action -in @('update', 'remove')) {
                    # A missing backup means the interrupted run never reached this file.
                    $backup = Resolve-ManagedPath -Destination $backupRoot -Relative $entry.backup
                    if (-not (Test-Path -LiteralPath $backup)) { continue }
                    New-Item (Split-Path $target -Parent) -ItemType Directory -Force | Out-Null
                    Write-ManagedFileAtomically -Path $target -Bytes ([System.IO.File]::ReadAllBytes($backup))
                } else {
                    throw "Invalid transaction journal action in ${journalPath}: $($entry.action)"
                }
            }
            Write-Output "ROLLBACK $Destination $($journal.stamp)"
            [System.IO.File]::Delete($journalPath)
        }
    }
    $oldBackupRoot = Resolve-ManagedPath -Destination $Destination -Relative 'backups'
    if ($backupRoot -ne $oldBackupRoot -and (Test-Path -LiteralPath $oldBackupRoot)) {
        if ($DryRun) {
            if (-not $Summary) { Write-Output "DRYRUN MOVE $oldBackupRoot -> $backupRoot" }
        } else {
            New-Item -ItemType Directory -Path $backupRoot -Force | Out-Null
            Move-Item -LiteralPath $oldBackupRoot -Destination (Join-Path $backupRoot ('legacy-' + [Guid]::NewGuid().ToString('N')))
        }
    }

    # Plan every change before writing anything, so the journal can describe the whole run.
    $plan = New-Object System.Collections.ArrayList
    Get-ChildItem $Source -File -Recurse | ForEach-Object {
        $relative = $_.FullName.Substring($Source.Length).TrimStart([char[]]@('\','/')).Replace('\','/')
        if ((Split-Path $Destination -Leaf) -eq '.codex' -and $relative.StartsWith('skills/')) { return }
        if ((Split-Path $Destination -Leaf) -eq '.claude' -and -not $StatusLineEnabled -and $relative.StartsWith('statusline/')) { return }
        if (-not $SemanticRetrievalEnabled -and $relative -match '(^|/)semantic-search/') { return }
        $target = Resolve-ManagedPath -Destination $Destination -Relative $relative
        $rawContent = Get-Content -LiteralPath $_.FullName -Raw -Encoding UTF8
        $filterOptions = ((-not $FlashbangEnabled) -or (-not $StatusLineEnabled) -or (-not $SemanticRetrievalEnabled)) -and $relative -in @('settings.json', 'config.toml')
        if ($filterOptions) {
            $flashbangOption = if ($FlashbangEnabled) { 'true' } else { 'false' }
            $statusLineOption = if ($StatusLineEnabled) { 'true' } else { 'false' }
            $rawContent = Invoke-InstallOptions -Arguments @('filter', '--path', $_.FullName, '--flashbang', $flashbangOption, '--statusline', $statusLineOption, '--semantic-retrieval', $(if ($SemanticRetrievalEnabled) { 'true' } else { 'false' })) -ErrorMessage 'Could not configure install options.'
        }
        $filterInstructions = $relative -in @('CLAUDE.md', 'AGENTS.md') -or ((-not $SemanticRetrievalEnabled) -and $relative -eq 'rules/general.md')
        if ($filterInstructions) {
            $rawContent = Invoke-InstallOptions -Arguments @('filter-instructions', '--path', $_.FullName, '--destination', $Destination, '--semantic-retrieval', $(if ($SemanticRetrievalEnabled) { 'true' } else { 'false' })) -ErrorMessage 'Could not configure install options.'
        }
        $needsSubstitution = $filterOptions -or $filterInstructions -or $rawContent.Contains('__AI_CONFIG_ROOT__') -or $rawContent.Contains('__HOOK_COMMAND__') -or $rawContent.Contains('__POWERSHELL_HOOK_COMMAND__') -or $rawContent.Contains('__POWERSHELL_COMMAND__') -or $rawContent.Contains('__CLAUDE_CODE_MAX_TOOL_USE_CONCURRENCY__')
        if ($needsSubstitution) {
            $finalContent = $rawContent.Replace('__AI_CONFIG_ROOT__', $AiConfigRoot).Replace('__HOOK_COMMAND__', $ShellCommand).Replace('__POWERSHELL_HOOK_COMMAND__', $PowerShellCommand).Replace('__POWERSHELL_COMMAND__', $PowerShellCommand).Replace('__CLAUDE_CODE_MAX_TOOL_USE_CONCURRENCY__', $ClaudeConcurrency).Replace('__HOOK_SCRIPT__', 'flashbang.ps1').Replace('__POWERSHELL_HOOK_SCRIPT__', 'flashbang.ps1')
            $newBytes = [System.Text.Encoding]::UTF8.GetBytes($finalContent)
        } else {
            $newBytes = [System.IO.File]::ReadAllBytes($_.FullName)
        }
        if ($relative -eq 'config.toml' -and (Test-Path -LiteralPath $target)) {
            $statusLineFlag = if ($StatusLineEnabled) { 'true' } else { 'false' }
            $content = Invoke-InstallOptions -Arguments @('merge-toml', '--current', $target, '--statusline', $statusLineFlag) -Managed $newBytes -ErrorMessage 'Could not merge managed config.toml keys.'
            $newBytes = [System.Text.Encoding]::UTF8.GetBytes($content)
        }
        if ($relative -eq 'settings.json' -and (Test-Path -LiteralPath $target)) {
            $finalContent = Invoke-InstallOptions -Arguments @('merge-json', '--current', $target) -Managed $newBytes -ErrorMessage 'Could not merge managed settings.json keys.'
            $newBytes = [System.Text.Encoding]::UTF8.GetBytes($finalContent)
        }
        $newHash = Get-Sha256HashOfBytes $newBytes
        $newManifest[$relative] = $newHash

        $exists = Test-Path -LiteralPath $target
        $action = if (-not $exists) { 'CREATE' } elseif ((Get-Sha256Hash $target) -eq $newHash) { 'UNCHANGED' } else { 'UPDATE' }
        $null = $plan.Add([pscustomobject]@{ Relative = $relative; Target = $target; Action = $action; Bytes = $newBytes; Hash = $newHash })
    }
    foreach ($relative in @($oldManifest.Keys | Where-Object { -not $newManifest.ContainsKey($_) })) {
        $target = Resolve-ManagedPath -Destination $Destination -Relative $relative
        if (-not (Test-Path -LiteralPath $target)) { continue }
        # A stale file changed locally is backed up but kept; only an unmodified one is removed.
        $action = if ((Get-Sha256Hash $target) -eq $oldManifest[$relative]) { 'REMOVE' } else { 'KEEP' }
        $null = $plan.Add([pscustomobject]@{ Relative = $relative; Target = $target; Action = $action; Bytes = $null; Hash = $null })
    }

    if (-not $DryRun) {
        $journalEntries = @(foreach ($item in $plan) {
            switch ($item.Action) {
                'CREATE' { [ordered]@{ path = $item.Relative; action = 'create'; sha256 = $item.Hash } }
                'UPDATE' { [ordered]@{ path = $item.Relative; action = 'update'; backup = "$Stamp/$($item.Relative)"; sha256 = $item.Hash } }
                'REMOVE' { [ordered]@{ path = $item.Relative; action = 'remove'; backup = "$Stamp/$($item.Relative)" } }
            }
        })
        $journalJson = ConvertTo-Json -InputObject ([ordered]@{ stamp = $Stamp; files = $journalEntries }) -Depth 4
        New-Item $Destination -ItemType Directory -Force | Out-Null
        Write-ManagedFileAtomically -Path $journalPath -Bytes ((New-Object System.Text.UTF8Encoding($false)).GetBytes($journalJson + "`n"))
    }

    foreach ($item in $plan) {
        $target = $item.Target
        if ($item.Action -eq 'UNCHANGED') { $tally.Unchanged++; if (-not $Summary) { Write-Output "UNCHANGED $target" }; continue }
        $isRemoval = $item.Action -in @('REMOVE', 'KEEP')
        if ($DryRun) {
            if ($isRemoval) { if (-not $Summary) { Write-Output "DRYRUN REMOVE $target" }; $tally.Removed++ }
            else { if (-not $Summary) { Write-Output "DRYRUN $($item.Action) $target" }; if ($item.Action -eq 'CREATE') { $tally.Created++ } else { $tally.Updated++ } }
            continue
        }
        if ($item.Action -ne 'CREATE') {
            $backup = Resolve-ManagedPath -Destination $backupRoot -Relative "$Stamp/$($item.Relative)"
            New-Item (Split-Path $backup -Parent) -ItemType Directory -Force | Out-Null
            # Atomic, so a rollback after an interruption never restores a truncated backup.
            Write-ManagedFileAtomically -Path $backup -Bytes ([System.IO.File]::ReadAllBytes($target))
            if (-not $Summary) { Write-Output "BACKUP $target -> $backup" }
        }
        if ($item.Action -eq 'REMOVE') {
            Remove-Item -LiteralPath $target -Force
            if (-not $Summary) { Write-Output "REMOVE $target" }
            $tally.Removed++
            continue
        }
        if ($item.Action -eq 'KEEP') {
            Write-Output "WARN $target was managed by a previous installation and has changed locally; it was backed up but left in place instead of being removed."
            $tally.Warned++
            continue
        }
        if ($item.Action -eq 'UPDATE' -and -not $oldManifest.ContainsKey($item.Relative)) { Write-Output "WARN $target existed before this installation but was not tracked by a previous run; it was backed up before being overwritten."; $tally.Warned++ }
        New-Item (Split-Path $target -Parent) -ItemType Directory -Force | Out-Null
        Write-ManagedFileAtomically -Path $target -Bytes $item.Bytes
        if (-not $Summary) { Write-Output "$($item.Action) $target" }
        if ($item.Action -eq 'CREATE') { $tally.Created++ } else { $tally.Updated++ }
    }

    if (-not $DryRun) {
        Write-ManagedManifest $manifestPath $newManifest
        [System.IO.File]::Delete($journalPath)
    }
    if ($Summary) { Write-Output ("SYNC {0}: {1} created, {2} updated, {3} unchanged, {4} removed, {5} warnings" -f $Destination, $tally.Created, $tally.Updated, $tally.Unchanged, $tally.Removed, $tally.Warned) }
}