[CmdletBinding()]
param(
    [Parameter(Position = 0)]
    [ValidateSet('menu', 'start', 'restart', 'stop', 'status')]
    [string]$Action = 'menu',

    [ValidateSet('split', 'wails')]
    [string]$Mode = 'split'
)

$ErrorActionPreference = 'Stop'
$Root = (Resolve-Path (Join-Path $PSScriptRoot '..')).Path
$RunDir = Join-Path $Root '.run'
$StatePath = Join-Path $RunDir 'project-processes.json'
$BackendExe = Join-Path $RunDir 'smart-parking-backend.exe'
$WailsGoCache = Join-Path $Root '.gocache-wails'
$BackendBuildLog = Join-Path $RunDir 'backend-build.log'
$BackendStdout = Join-Path $RunDir 'backend.stdout.log'
$BackendStderr = Join-Path $RunDir 'backend.stderr.log'
$FrontendStdout = Join-Path $RunDir 'frontend.stdout.log'
$FrontendStderr = Join-Path $RunDir 'frontend.stderr.log'
$WailsStdout = Join-Path $RunDir 'wails.stdout.log'
$WailsStderr = Join-Path $RunDir 'wails.stderr.log'

function Ensure-RunDirectory {
    if (-not (Test-Path -LiteralPath $RunDir)) {
        New-Item -ItemType Directory -Path $RunDir | Out-Null
    }
}

function Read-State {
    if (-not (Test-Path -LiteralPath $StatePath)) { return $null }
    try {
        return Get-Content -LiteralPath $StatePath -Raw | ConvertFrom-Json
    } catch {
        Write-Warning "Ignoring invalid state file: $StatePath"
        return $null
    }
}

function Write-State([string]$RunMode, [array]$Processes) {
    Ensure-RunDirectory
    [ordered]@{
        root = $Root
        mode = $RunMode
        started_at = (Get-Date).ToString('o')
        processes = $Processes
    } | ConvertTo-Json -Depth 4 | Set-Content -LiteralPath $StatePath -Encoding UTF8
}

function Remove-State {
    if (Test-Path -LiteralPath $StatePath) {
        Remove-Item -LiteralPath $StatePath -Force
    }
}

function Stop-ProcessTree([int]$ProcessId) {
    if ($ProcessId -le 0) { return }
    $process = Get-Process -Id $ProcessId -ErrorAction SilentlyContinue
    if ($null -eq $process) { return }
    Write-Host "Stopping $($process.ProcessName) (PID $ProcessId)"
    & taskkill.exe /PID $ProcessId /T /F 2>$null | Out-Null
}

function Stop-ManagedProcesses {
    $state = Read-State
    if ($null -eq $state) {
        Write-Host 'No managed project state found.'
        return
    }
    foreach ($item in @($state.processes)) {
        Stop-ProcessTree ([int]$item.pid)
    }
    Remove-State
    Write-Host 'Project processes stopped.'
}

function Assert-Command([string]$Name) {
    if ($null -eq (Get-Command $Name -ErrorAction SilentlyContinue)) {
        throw "Required command not found: $Name"
    }
}

function Wait-Http([string]$Url, [int]$TimeoutSeconds = 30) {
    for ($i = 0; $i -lt $TimeoutSeconds; $i++) {
        try {
            $response = Invoke-WebRequest -Uri $Url -UseBasicParsing -TimeoutSec 2 -ErrorAction Stop
            if ($response.StatusCode -ge 200 -and $response.StatusCode -lt 500) { return $true }
        } catch { }
        Start-Sleep -Seconds 1
    }
    return $false
}

function Start-SplitMode {
    Assert-Command 'go'
    Assert-Command 'npm'
    Ensure-RunDirectory

    Write-Host 'Building backend...'
    Push-Location $Root
    try {
        & go build -o $BackendExe .\cmd_backend_only\ 2>&1 | Tee-Object -FilePath $BackendBuildLog
        if ($LASTEXITCODE -ne 0) { throw 'Backend build failed.' }
    } finally {
        Pop-Location
    }

    $backend = Start-Process -FilePath $BackendExe -WorkingDirectory $Root `
        -RedirectStandardOutput $BackendStdout -RedirectStandardError $BackendStderr -PassThru
    $frontend = Start-Process -FilePath 'npm.cmd' -ArgumentList @('run', 'dev') `
        -WorkingDirectory (Join-Path $Root 'frontend') `
        -RedirectStandardOutput $FrontendStdout -RedirectStandardError $FrontendStderr -PassThru
    Write-State 'split' @(
        [ordered]@{ name = 'backend'; pid = $backend.Id; port = 8888 },
        [ordered]@{ name = 'frontend'; pid = $frontend.Id; port = 5173 }
    )

    if (-not (Wait-Http 'http://127.0.0.1:8888/health')) {
        Stop-ManagedProcesses
        throw "Backend did not become ready. See $BackendStdout and $BackendStderr"
    }
    Write-Host 'Backend ready: http://127.0.0.1:8888'
    Write-Host 'Frontend:      http://localhost:5173'
}

function Start-WailsMode {
    Assert-Command 'wails'
    Ensure-RunDirectory
    New-Item -ItemType Directory -Path $WailsGoCache -Force | Out-Null
    # Keep Wails/Go build artifacts in the project workspace. The default
    # user cache can be inaccessible on locked-down Windows installations.
    $env:GOCACHE = $WailsGoCache
    $wails = Start-Process -FilePath 'wails' -ArgumentList @('dev') `
        -WorkingDirectory $Root -RedirectStandardOutput $WailsStdout `
        -RedirectStandardError $WailsStderr -PassThru
    Write-State 'wails' @([ordered]@{ name = 'wails'; pid = $wails.Id; port = 5173 })
    Write-Host "Wails dev started (PID $($wails.Id)). See $WailsStdout and $WailsStderr"
}

function Show-Status {
    $state = Read-State
    if ($null -eq $state) {
        Write-Host 'Project is not managed by this script.'
        return
    }
    Write-Host "Mode: $($state.mode)"
    Write-Host "Started: $($state.started_at)"
    foreach ($item in @($state.processes)) {
        $process = Get-Process -Id ([int]$item.pid) -ErrorAction SilentlyContinue
        $status = if ($null -eq $process) { 'stopped' } else { 'running' }
        Write-Host ("{0}: PID {1}, port {2}, {3}" -f $item.name, $item.pid, $item.port, $status)
    }
}

function Show-Menu {
    while ($true) {
        Clear-Host
        Write-Host '========================================' -ForegroundColor Cyan
        Write-Host '       Smart Parking Project Manager' -ForegroundColor Cyan
        Write-Host '========================================'
        Write-Host '1. Start project'
        Write-Host '2. Stop project'
        Write-Host '3. Restart project'
        Write-Host '4. Show status'
        Write-Host '0. Exit'
        Write-Host ''

        $choice = Read-Host 'Select action'
        if ($choice -eq '1') {
            if ($null -ne (Read-State)) {
                Write-Host 'Project is already running; use stop or restart.' -ForegroundColor Yellow
            } elseif ($Mode -eq 'wails') {
                Start-WailsMode
            } else {
                Start-SplitMode
            }
        } elseif ($choice -eq '2') {
            Stop-ManagedProcesses
        } elseif ($choice -eq '3') {
            Stop-ManagedProcesses
            if ($Mode -eq 'wails') { Start-WailsMode } else { Start-SplitMode }
        } elseif ($choice -eq '4') {
            Show-Status
        } elseif ($choice -eq '0') {
            return
        } else {
            Write-Host 'Invalid option.' -ForegroundColor Red
        }

        if ($choice -ne '0') {
            Write-Host ''
            Read-Host 'Press Enter to return to menu'
        }
    }
}

switch ($Action) {
    'menu' {
        Show-Menu
    }
    'stop' {
        Stop-ManagedProcesses
    }
    'status' {
        Show-Status
    }
    'restart' {
        Stop-ManagedProcesses
        if ($Mode -eq 'wails') { Start-WailsMode } else { Start-SplitMode }
    }
    'start' {
        if ($null -ne (Read-State)) {
            Write-Host 'A managed instance already exists; use restart or stop first.'
            exit 1
        }
        if ($Mode -eq 'wails') { Start-WailsMode } else { Start-SplitMode }
    }
}