import { NextRequest, NextResponse } from "next/server";
import { spawn } from "node:child_process";
import { assertLocalRequest } from "@/lib/api/localOnly";

export const runtime = "nodejs";
export const dynamic = "force-dynamic";

/**
 * Open a native OS folder-picker dialog and return the absolute path the
 * user selected. Works because Pinkudex is local-only — the Next.js
 * server has the same desktop session as the browser. Returns
 * `{ path: null }` if the user cancels.
 *
 * Windows: PowerShell + WinForms FolderBrowserDialog.
 * macOS:   osascript "choose folder".
 * Linux:   zenity (must be installed).
 */
export async function POST(req: NextRequest) {
  const blocked = assertLocalRequest(req);
  if (blocked) return blocked;

  const body = await req.json().catch(() => ({}));
  const startPath = typeof body.start === "string" ? body.start : "";

  try {
    const path = await runPicker(startPath);
    return NextResponse.json({ path });
  } catch (e) {
    return NextResponse.json({ error: (e as Error).message, path: null }, { status: 500 });
  }
}

function runPicker(startPath: string): Promise<string | null> {
  if (process.platform === "win32") return pickerWindows(startPath);
  if (process.platform === "darwin") return pickerMacOS(startPath);
  return pickerLinux(startPath);
}

function pickerWindows(startPath: string): Promise<string | null> {
  // STA threading is required for WinForms dialogs in PowerShell.
  // -Sta keeps it; -NoProfile avoids whatever the user's profile prints.
  // startPath is passed via env var so PowerShell never parses it as code.
  const script = `
    Add-Type -AssemblyName System.Windows.Forms | Out-Null
    $dlg = New-Object System.Windows.Forms.FolderBrowserDialog
    $dlg.Description = 'Pinkudex — pick a folder'
    $dlg.ShowNewFolderButton = $false
    if ($env:PINKUDEX_PICK_START) { try { $dlg.SelectedPath = $env:PINKUDEX_PICK_START } catch {} }
    $owner = New-Object System.Windows.Forms.Form
    $owner.TopMost = $true
    $owner.Opacity = 0
    $owner.ShowInTaskbar = $false
    $result = $dlg.ShowDialog($owner)
    if ($result -eq [System.Windows.Forms.DialogResult]::OK) {
      Write-Output $dlg.SelectedPath
    }
  `.trim();
  return runProcess("powershell.exe", ["-NoProfile", "-Sta", "-Command", script], {
    PINKUDEX_PICK_START: startPath,
  });
}

function pickerMacOS(startPath: string): Promise<string | null> {
  const startClause = startPath
    ? ` default location (POSIX file "${startPath.replace(/"/g, '\\"')}")`
    : "";
  const script = `try
    set f to choose folder with prompt "Pinkudex — pick a folder"${startClause}
    return POSIX path of f
  on error number -128
    return ""
  end try`;
  return runProcess("osascript", ["-e", script]);
}

function pickerLinux(startPath: string): Promise<string | null> {
  const args = ["--file-selection", "--directory", "--title=Pinkudex — pick a folder"];
  if (startPath) args.push(`--filename=${startPath.endsWith("/") ? startPath : startPath + "/"}`);
  return runProcess("zenity", args).catch((e) => {
    throw new Error(`Linux folder pickers require zenity to be installed (${(e as Error).message})`);
  });
}

function runProcess(
  cmd: string,
  args: string[],
  extraEnv?: Record<string, string>,
): Promise<string | null> {
  return new Promise((resolve, reject) => {
    const env = extraEnv ? { ...process.env, ...extraEnv } : process.env;
    const child = spawn(cmd, args, { stdio: ["ignore", "pipe", "pipe"], env });
    let out = "";
    let err = "";
    child.stdout.on("data", (b) => { out += b.toString(); });
    child.stderr.on("data", (b) => { err += b.toString(); });
    child.on("error", (e) => reject(e));
    child.on("close", (code) => {
      // Cancel paths return non-zero (zenity) or empty stdout — treat as null.
      if (code !== 0 && code !== 1 && code !== null) {
        reject(new Error(err.trim() || `picker exited with code ${code}`));
        return;
      }
      const trimmed = out.trim().replace(/\r/g, "");
      resolve(trimmed || null);
    });
  });
}