param(
  [switch]$NoPause
)

$ErrorActionPreference = "Stop"
$Root = Split-Path -Parent $PSScriptRoot
$Venv = Join-Path $Root ".venv"
$VenvPython = Join-Path $Venv "Scripts\python.exe"
$WheelDir = Join-Path $Root "vendor\wheels"
$Req = Join-Path $Root "requirements.txt"

function Write-Step {
  param([string]$Message)
  Write-Host ""
  Write-Host "==> $Message" -ForegroundColor Cyan
}

function Wait-BeforeExit {
  if (-not $NoPause) {
    Write-Host ""
    Read-Host "Press Enter to exit"
  }
}

function Get-PythonCandidate {
  $candidates = @(
    @{ Exe = "py"; Args = @("-3") },
    @{ Exe = "python"; Args = @() },
    @{ Exe = "python3"; Args = @() }
  )

  foreach ($candidate in $candidates) {
    $command = Get-Command $candidate.Exe -ErrorAction SilentlyContinue
    if (-not $command) {
      continue
    }

    try {
      $args = @($candidate.Args) + @("-c", "import sys; print(sys.executable); print(sys.version_info.major); print(sys.version_info.minor)")
      $output = & $candidate.Exe @args 2>$null
      if ($LASTEXITCODE -ne 0 -or $output.Count -lt 3) {
        continue
      }
      $major = [int]$output[1]
      $minor = [int]$output[2]
      if ($major -gt 3 -or ($major -eq 3 -and $minor -ge 10)) {
        return [pscustomobject]@{
          Exe = $candidate.Exe
          Args = $candidate.Args
          Path = $output[0]
          Version = "$major.$minor"
        }
      }
    } catch {
      continue
    }
  }

  return $null
}

function Install-PythonWithWinget {
  $winget = Get-Command winget -ErrorAction SilentlyContinue
  if (-not $winget) {
    throw "Python 3.10+ was not found, and winget is not available. Install Python 3.10+ manually and run this script again."
  }

  Write-Step "Python was not found. Installing Python 3.12 with winget"
  & winget install --id Python.Python.3.12 -e --source winget --accept-package-agreements --accept-source-agreements
  if ($LASTEXITCODE -ne 0) {
    throw "winget failed to install Python. Check network access or install Python 3.10+ manually."
  }
}

function Ensure-Python {
  $python = Get-PythonCandidate
  if ($python) {
    Write-Host "Python found: $($python.Path), version $($python.Version)"
    return $python
  }

  Install-PythonWithWinget
  $python = Get-PythonCandidate
  if (-not $python) {
    throw "Python is still unavailable after installation. Reopen PowerShell or check PATH."
  }
  Write-Host "Python ready: $($python.Path), version $($python.Version)"
  return $python
}

function Invoke-Python {
  param(
    [object]$Python,
    [string[]]$Arguments
  )
  $allArgs = @($Python.Args) + $Arguments
  & $Python.Exe @allArgs
  if ($LASTEXITCODE -ne 0) {
    throw "Python command failed: $($Python.Exe) $($allArgs -join ' ')"
  }
}

function Ensure-Venv {
  param([object]$Python)
  if (-not (Test-Path $VenvPython)) {
    Write-Step "Creating virtual environment"
    Invoke-Python -Python $Python -Arguments @("-m", "venv", $Venv)
  } else {
    Write-Host "Virtual environment already exists: $Venv"
  }

  if (-not (Test-Path $VenvPython)) {
    throw "Failed to create virtual environment: $VenvPython does not exist."
  }
}

function Install-Requirements {
  if (-not (Test-Path $Req)) {
    throw "requirements.txt was not found: $Req"
  }

  Write-Step "Installing dependencies"
  $wheels = @()
  if (Test-Path $WheelDir) {
    $wheels = Get-ChildItem -Path $WheelDir -Filter *.whl -File -ErrorAction SilentlyContinue
  }

  if ($wheels.Count -gt 0) {
    Write-Host "Offline wheel directory found: $WheelDir"
    & $VenvPython -m pip install --no-index --find-links $WheelDir -r $Req
  } else {
    Write-Host "No offline wheels found. Installing dependencies from the network."
    & $VenvPython -m pip install -r $Req
  }

  if ($LASTEXITCODE -ne 0) {
    throw "Dependency installation failed. If the server is offline, run scripts\download_wheels.ps1 on an online machine first and copy vendor\wheels to this server."
  }
}

function Test-ApplicationImport {
  Write-Step "Verifying environment"
  & $VenvPython -c "import fastapi, uvicorn, xlrd, xlwt, xlutils, httpx, yaml; print('Dependency verification passed')"
  if ($LASTEXITCODE -ne 0) {
    throw "Dependency verification failed."
  }
}

try {
  Set-Location $Root
  Write-Step "Preparing PCFAnalysis environment"
  $python = Ensure-Python
  Ensure-Venv -Python $python
  Install-Requirements
  Test-ApplicationImport
  Write-Host ""
  Write-Host "Environment installation completed. Run scripts\run.ps1 to start the service." -ForegroundColor Green
} catch {
  Write-Host ""
  Write-Host "Installation failed:" -ForegroundColor Red
  Write-Host $_.Exception.Message -ForegroundColor Red
  exit 1
} finally {
  Wait-BeforeExit
}