use crate::proxy_storage::{
  delete_proxy_config, generate_proxy_id, get_proxy_config, is_process_running, list_proxy_configs,
  save_proxy_config, ProxyConfig,
};
use std::path::{Path, PathBuf};
use std::process::Stdio;
use std::sync::atomic::{AtomicBool, Ordering};
static PROXY_PROCESSES: std::sync::LazyLock<
  std::sync::Mutex<std::collections::HashMap<String, u32>>,
> = std::sync::LazyLock::new(|| std::sync::Mutex::new(std::collections::HashMap::new()));

static SIDECAR_VERSION_VERIFIED: AtomicBool = AtomicBool::new(false);
const RETAINED_PROXY_LOGS: usize = 20;

fn prune_stale_proxy_logs(temp_dir: &Path, retain: usize) {
  let active_ids = PROXY_PROCESSES
    .lock()
    .map(|processes| processes.keys().cloned().collect::<Vec<_>>())
    .unwrap_or_default();
  let Ok(entries) = std::fs::read_dir(temp_dir) else {
    return;
  };
  let mut logs = entries
    .flatten()
    .filter_map(|entry| {
      let file_name = entry.file_name();
      let file_name = file_name.to_str()?;
      let id = file_name
        .strip_prefix("donut-proxy-")?
        .strip_suffix(".log")?;
      if active_ids.iter().any(|active_id| active_id == id) {
        return None;
      }
      let modified = entry
        .metadata()
        .and_then(|metadata| metadata.modified())
        .unwrap_or(std::time::UNIX_EPOCH);
      Some((modified, entry.path()))
    })
    .collect::<Vec<_>>();
  logs.sort_unstable_by_key(|entry| std::cmp::Reverse(entry.0));
  for (_, path) in logs.into_iter().skip(retain) {
    if let Err(error) = std::fs::remove_file(&path) {
      log::debug!(
        "Stale proxy log prune failed path={} err=\"{error}\"",
        path.display()
      );
    }
  }
}

fn target_binary_name(base_name: &str) -> String {
  let target = env!("DONUT_BUILD_TARGET");
  #[cfg(windows)]
  {
    format!("{base_name}-{target}.exe")
  }

  #[cfg(not(windows))]
  {
    format!("{base_name}-{target}")
  }
}

fn unsuffixed_binary_name(base_name: &str) -> String {
  #[cfg(windows)]
  {
    format!("{base_name}.exe")
  }

  #[cfg(not(windows))]
  {
    base_name.to_string()
  }
}

fn is_executable_file(path: &Path) -> bool {
  let Ok(metadata) = path.metadata() else {
    return false;
  };
  if !metadata.is_file() {
    return false;
  }
  #[cfg(unix)]
  {
    use std::os::unix::fs::PermissionsExt;
    metadata.permissions().mode() & 0o111 != 0
  }
  #[cfg(windows)]
  {
    path
      .extension()
      .and_then(|extension| extension.to_str())
      .is_some_and(|extension| extension.eq_ignore_ascii_case("exe"))
  }
}

fn push_candidate_dir(dirs: &mut Vec<PathBuf>, dir: Option<PathBuf>) {
  if let Some(dir) = dir {
    if !dirs.iter().any(|existing| existing == &dir) {
      dirs.push(dir);
    }
  }
}

pub(crate) fn find_sidecar_executable(
  base_name: &str,
) -> Result<PathBuf, Box<dyn std::error::Error>> {
  let current_exe = std::env::current_exe()?;
  let current_dir = current_exe
    .parent()
    .ok_or("Failed to get parent directory of current executable")?;

  if current_exe
    .file_stem()
    .and_then(|stem| stem.to_str())
    .is_some_and(|stem| stem == base_name)
  {
    return Ok(current_exe);
  }

  let manifest_dir = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
  let mut search_dirs = Vec::new();

  push_candidate_dir(&mut search_dirs, Some(current_dir.to_path_buf()));
  push_candidate_dir(
    &mut search_dirs,
    current_dir.parent().map(std::path::Path::to_path_buf),
  );
  push_candidate_dir(
    &mut search_dirs,
    current_dir
      .parent()
      .and_then(|parent| parent.parent())
      .map(Path::to_path_buf),
  );
  push_candidate_dir(&mut search_dirs, Some(current_dir.join("binaries")));
  push_candidate_dir(
    &mut search_dirs,
    current_dir.parent().map(|parent| parent.join("binaries")),
  );
  push_candidate_dir(
    &mut search_dirs,
    current_dir
      .parent()
      .and_then(|parent| parent.parent())
      .map(|parent| parent.join("binaries")),
  );
  push_candidate_dir(&mut search_dirs, Some(manifest_dir.join("binaries")));
  push_candidate_dir(
    &mut search_dirs,
    Some(manifest_dir.join("target").join("debug")),
  );
  push_candidate_dir(
    &mut search_dirs,
    Some(manifest_dir.join("target").join("release")),
  );

  let exact_names = [
    unsuffixed_binary_name(base_name),
    target_binary_name(base_name),
  ];

  for dir in &search_dirs {
    for name in &exact_names {
      if name.is_empty() {
        continue;
      }

      let candidate = dir.join(name);
      if is_executable_file(&candidate) {
        return Ok(candidate);
      }
    }
  }

  Err(
    format!(
      "Failed to locate '{}' executable. Searched in: {}",
      base_name,
      search_dirs
        .iter()
        .map(|dir| dir.display().to_string())
        .collect::<Vec<_>>()
        .join(", ")
    )
    .into(),
  )
}

fn parse_sidecar_version(stdout: &[u8]) -> Option<String> {
  let output = std::str::from_utf8(stdout).ok()?.trim();
  output
    .strip_prefix("donut-proxy ")
    .map(str::trim)
    .filter(|version| !version.is_empty() && !version.contains(char::is_whitespace))
    .map(str::to_string)
}

fn sidecar_version_mismatch_error() -> Box<dyn std::error::Error> {
  serde_json::json!({
    "code": "PROXY_SIDECAR_VERSION_MISMATCH"
  })
  .to_string()
  .into()
}

/// Verify that the installed sidecar was built for the same release as the
/// main app. Windows can otherwise retain an executing, locked sidecar while
/// NSIS replaces the app, leaving an incompatible mixed-version installation.
pub(crate) async fn ensure_sidecar_version() -> Result<(), Box<dyn std::error::Error>> {
  if SIDECAR_VERSION_VERIFIED.load(Ordering::Acquire) {
    return Ok(());
  }

  let executable = match find_sidecar_executable("donut-proxy") {
    Ok(executable) => executable,
    Err(e) => {
      log::error!("donut-proxy not found for version check err=\"{e}\"");
      return Err(sidecar_version_mismatch_error());
    }
  };
  let checked = std::time::Instant::now();
  let mut command = std::process::Command::new(&executable);
  command.arg("--version");

  #[cfg(windows)]
  {
    use std::os::windows::process::CommandExt;
    const CREATE_NO_WINDOW: u32 = 0x08000000;
    command.creation_flags(CREATE_NO_WINDOW);
  }

  let output = match command.output() {
    Ok(output) => output,
    Err(e) => {
      log::error!(
        "donut-proxy version check failed to run path={} err=\"{e}\"",
        executable.display()
      );
      return Err(sidecar_version_mismatch_error());
    }
  };
  let actual_version = parse_sidecar_version(&output.stdout);
  let expected_version = env!("BUILD_VERSION");
  log::debug!(
    "Sidecar version checked path={} elapsed_ms={}",
    executable.display(),
    checked.elapsed().as_millis()
  );

  if output.status.success() && actual_version.as_deref() == Some(expected_version) {
    SIDECAR_VERSION_VERIFIED.store(true, Ordering::Release);
    return Ok(());
  }

  log::error!(
    "donut-proxy version mismatch expected={} actual={:?} status=\"{}\" stdout={:?} stderr={:?}",
    expected_version,
    actual_version,
    output.status,
    String::from_utf8_lossy(&output.stdout),
    String::from_utf8_lossy(&output.stderr)
  );
  Err(sidecar_version_mismatch_error())
}

pub async fn start_proxy_process(
  upstream_url: Option<String>,
  port: Option<u16>,
) -> Result<ProxyConfig, Box<dyn std::error::Error>> {
  start_proxy_process_with_profile(
    upstream_url,
    port,
    None,
    Vec::new(),
    None,
    false,
    None,
    None,
    true,
  )
  .await
}

#[allow(clippy::too_many_arguments)]
pub async fn start_proxy_process_with_profile(
  upstream_url: Option<String>,
  port: Option<u16>,
  profile_id: Option<String>,
  bypass_rules: Vec<String>,
  blocklist_file: Option<String>,
  dns_allowlist_mode: bool,
  dns_server: Option<String>,
  local_protocol: Option<String>,
  record_domains: bool,
) -> Result<ProxyConfig, Box<dyn std::error::Error>> {
  let dns_server = crate::profile_dns::normalize_dns_server(dns_server)?;
  ensure_sidecar_version().await?;

  let id = generate_proxy_id();
  let upstream = upstream_url.unwrap_or_else(|| "DIRECT".to_string());

  // Get available port if not specified
  let local_port = port.unwrap_or_else(|| {
    // Find an available port
    let listener = std::net::TcpListener::bind("127.0.0.1:0").unwrap();
    listener.local_addr().unwrap().port()
  });

  let config = ProxyConfig::new(id.clone(), upstream, Some(local_port))
    .with_profile_id(profile_id.clone())
    .with_bypass_rules(bypass_rules)
    .with_blocklist_file(blocklist_file)
    .with_dns_allowlist_mode(dns_allowlist_mode)
    .with_dns_server(dns_server)
    .with_local_protocol(local_protocol)
    .with_record_domains(record_domains);
  save_proxy_config(&config)?;

  spawn_proxy_worker(&config, false).await
}

/// Restart only a dead worker whose browser is still alive. Keep its full
/// route and listening port: the running browser cannot use a new port.
pub async fn recover_proxy_process(
  id: &str,
) -> Result<Option<ProxyConfig>, Box<dyn std::error::Error>> {
  let Some(config) = get_proxy_config(id) else {
    return Ok(None);
  };
  if !proxy_needs_recovery(&config) {
    return Ok(None);
  }
  ensure_sidecar_version().await?;
  spawn_proxy_worker(&config, true).await.map(Some)
}

pub(crate) fn proxy_needs_recovery(config: &ProxyConfig) -> bool {
  config.profile_id.is_some()
    && config.local_port.is_some_and(|port| port != 0)
    && config.pid.is_some_and(|pid| !is_process_running(pid))
    && crate::proxy_storage::browser_owner_is_alive(config)
}

async fn spawn_proxy_worker(
  config: &ProxyConfig,
  recovering: bool,
) -> Result<ProxyConfig, Box<dyn std::error::Error>> {
  let started = std::time::Instant::now();
  let id = config.id.clone();
  let profile_id = config.profile_id.as_deref().unwrap_or("none");
  let upstream_kind = upstream_scheme(&config.upstream_url);

  // Spawn proxy worker process in the background using std::process::Command
  // This ensures proper process detachment on Unix systems
  let exe = find_sidecar_executable("donut-proxy")?;
  let temp_dir = std::env::temp_dir();
  let log_path = temp_dir.join(format!("donut-proxy-{id}.log"));
  let log_file = if recovering && log_path.exists() {
    crate::app_dirs::restrict_to_owner(&log_path);
    std::fs::OpenOptions::new().append(true).open(&log_path)
  } else {
    crate::app_dirs::create_owner_only(&log_path)
  };
  prune_stale_proxy_logs(&temp_dir, RETAINED_PROXY_LOGS);
  let spawned_pid: u32;

  #[cfg(unix)]
  {
    use std::os::unix::process::CommandExt;
    use std::process::Command as StdCommand;

    let mut cmd = StdCommand::new(&exe);
    cmd.arg("proxy-worker");
    cmd.arg("start");
    cmd.arg("--id");
    cmd.arg(&id);
    cmd.env_remove("DONUT_PROXY_USERNAME");
    cmd.env_remove("DONUT_PROXY_PASSWORD");

    cmd.stdin(Stdio::null());
    cmd.stdout(Stdio::null());

    // Always log to file for diagnostics (both debug and release builds)
    if let Ok(file) = log_file {
      cmd.stderr(Stdio::from(file));
    } else {
      cmd.stderr(Stdio::null());
    }

    // Properly detach the process on Unix by creating a new session
    unsafe {
      cmd.pre_exec(|| {
        // Create a new process group so the process survives parent exit
        libc::setsid();

        // Set high priority so the proxy is killed last under resource pressure
        // Negative nice value = higher priority. Try -10, fall back to -5 if it fails.
        if libc::setpriority(libc::PRIO_PROCESS, 0, -10) != 0 {
          let _ = libc::setpriority(libc::PRIO_PROCESS, 0, -5);
        }

        Ok(())
      });
    }

    // Spawn detached process
    let child = cmd.spawn()?;
    let pid = child.id();
    spawned_pid = pid;
    log::debug!("Proxy worker spawned id={id} pid={pid}");

    // Store PID
    {
      let mut processes = PROXY_PROCESSES.lock().unwrap();
      processes.insert(id.clone(), pid);
    }

    watch_proxy_exit(child, id.clone());
  }

  #[cfg(windows)]
  {
    use std::os::windows::io::AsRawHandle;
    use std::os::windows::process::CommandExt;
    use std::process::Command as StdCommand;
    use windows::Win32::Foundation::{CloseHandle, SetHandleInformation, HANDLE, HANDLE_FLAGS};
    use windows::Win32::System::Threading::{
      OpenProcess, SetPriorityClass, ABOVE_NORMAL_PRIORITY_CLASS, PROCESS_SET_INFORMATION,
    };

    // Mark current stdout/stderr as non-inheritable so the spawned worker process
    // does not inherit pipe handles from our parent (prevents blocking when parent exits).
    let stdout_handle = std::io::stdout().as_raw_handle();
    let stderr_handle = std::io::stderr().as_raw_handle();
    const HANDLE_FLAG_INHERIT: u32 = 0x00000001;
    unsafe {
      if !stdout_handle.is_null() {
        let _ = SetHandleInformation(HANDLE(stdout_handle), HANDLE_FLAG_INHERIT, HANDLE_FLAGS(0));
      }
      if !stderr_handle.is_null() {
        let _ = SetHandleInformation(HANDLE(stderr_handle), HANDLE_FLAG_INHERIT, HANDLE_FLAGS(0));
      }
    }

    let mut cmd = StdCommand::new(&exe);
    cmd.arg("proxy-worker");
    cmd.arg("start");
    cmd.arg("--id");
    cmd.arg(&id);
    cmd.env_remove("DONUT_PROXY_USERNAME");
    cmd.env_remove("DONUT_PROXY_PASSWORD");

    cmd.stdin(Stdio::null());
    cmd.stdout(Stdio::null());

    // Log to file for diagnostics (matching Unix behavior)
    if let Ok(file) = log_file {
      cmd.stderr(Stdio::from(file));
    } else {
      cmd.stderr(Stdio::null());
    }

    // On Windows, use DETACHED_PROCESS | CREATE_NEW_PROCESS_GROUP for proper detachment.
    const DETACHED_PROCESS: u32 = 0x00000008;
    const CREATE_NEW_PROCESS_GROUP: u32 = 0x00000200;
    cmd.creation_flags(DETACHED_PROCESS | CREATE_NEW_PROCESS_GROUP);

    let child = cmd.spawn()?;
    let pid = child.id();
    spawned_pid = pid;

    // Set high priority so the proxy is killed last under resource pressure
    unsafe {
      if let Ok(handle) = OpenProcess(PROCESS_SET_INFORMATION, false, pid) {
        let _ = SetPriorityClass(handle, ABOVE_NORMAL_PRIORITY_CLASS);
        let _ = CloseHandle(handle);
      }
    }

    // Store PID
    {
      let mut processes = PROXY_PROCESSES.lock().unwrap();
      processes.insert(id.clone(), pid);
    }

    watch_proxy_exit(child, id.clone());
  }

  // Give the process a moment to start up before checking
  tokio::time::sleep(tokio::time::Duration::from_millis(100)).await;

  // Wait for the worker to bind to the port and update config
  // Since we pre-allocated the port, the worker should bind immediately
  // We check quickly with short intervals to make startup fast
  let mut attempts = 0;
  let max_attempts = 40; // 4 seconds max (40 * 100ms) - give it more time to start

  loop {
    // Use shorter sleep for faster startup
    tokio::time::sleep(tokio::time::Duration::from_millis(100)).await;

    if let Some(updated_config) = get_proxy_config(&id).filter(|c| c.pid == Some(spawned_pid)) {
      // Check if local_url is set (worker has bound and updated config)
      if let Some(ref local_url) = updated_config.local_url {
        if !local_url.is_empty() {
          if let Some(port) = updated_config.local_port {
            // Try to connect immediately - port should be ready since we pre-allocated it
            match tokio::time::timeout(
              tokio::time::Duration::from_millis(100),
              tokio::net::TcpStream::connect(("127.0.0.1", port)),
            )
            .await
            {
              Ok(Ok(_stream)) => {
                log::info!(
                  "Proxy worker started id={id} pid={spawned_pid} port={port} profile={} upstream={upstream_kind} elapsed_ms={}",
                  profile_id,
                  started.elapsed().as_millis()
                );
                return Ok(updated_config);
              }
              Ok(Err(_)) | Err(_) => {
                // Port not ready yet, continue waiting
              }
            }
          }
        }
      }
    }

    attempts += 1;
    if attempts >= max_attempts {
      // Try to get the config one more time for better error message
      let detail = if let Some(config) = get_proxy_config(&id) {
        // Check if process is still running
        let process_running = config.pid.map(is_process_running).unwrap_or(false);
        format!(
          "Config: id={}, local_url={:?}, local_port={:?}, pid={:?}, process_running={}",
          config.id, config.local_url, config.local_port, config.pid, process_running
        )
      } else {
        format!("Config not found for id: {}", id)
      };
      // The detached worker (if it did spawn) would otherwise outlive this
      // failed start with nothing tracking it — callers only get an error
      // string, so this is the last place that can still kill it.
      let _ = stop_proxy_process_inner(&id, "start_timeout", !recovering).await;
      return Err(format!("Proxy worker failed to start in time. {detail}").into());
    }
  }
}

fn watch_proxy_exit(mut child: std::process::Child, id: String) {
  let pid = child.id();
  // A recovered worker is a child of the long-lived GUI. Reap it off the
  // runtime so repeated failures do not leave zombies until the GUI exits.
  std::thread::spawn(move || match child.wait() {
    Ok(status) => log::info!("Proxy worker exited id={id} pid={pid} status=\"{status}\""),
    Err(error) => log::warn!("Proxy worker wait failed id={id} pid={pid} err=\"{error}\""),
  });
}

pub async fn stop_proxy_process(id: &str) -> Result<bool, Box<dyn std::error::Error>> {
  stop_proxy_process_because(id, "requested").await
}

/// `reason` names why the worker is stopped, for its one stop line.
pub(crate) async fn stop_proxy_process_because(
  id: &str,
  reason: &str,
) -> Result<bool, Box<dyn std::error::Error>> {
  stop_proxy_process_inner(id, reason, true).await
}

async fn stop_proxy_process_inner(
  id: &str,
  reason: &str,
  remove_config: bool,
) -> Result<bool, Box<dyn std::error::Error>> {
  let config = get_proxy_config(id);
  let pid = PROXY_PROCESSES
    .lock()
    .unwrap()
    .get(id)
    .copied()
    .or_else(|| config.as_ref().and_then(|config| config.pid));

  if let Some(pid) = pid {
    let was_running = is_process_running(pid);
    // Kill the process
    #[cfg(unix)]
    {
      use std::process::Command;
      let _ = Command::new("kill")
        .arg("-TERM")
        .arg(pid.to_string())
        .output();
    }
    #[cfg(windows)]
    {
      use std::os::windows::process::CommandExt;
      use std::process::Command;
      const CREATE_NO_WINDOW: u32 = 0x08000000;
      let _ = Command::new("taskkill")
        .args(["/F", "/PID", &pid.to_string()])
        .creation_flags(CREATE_NO_WINDOW)
        .output();
    }

    // Wait a bit for the process to exit
    tokio::time::sleep(tokio::time::Duration::from_millis(500)).await;

    // Remove from tracking
    {
      let mut processes = PROXY_PROCESSES.lock().unwrap();
      processes.remove(id);
    }

    // Delete the config file
    if remove_config {
      delete_proxy_config(id);
    }

    let how = if !was_running {
      "already_gone"
    } else if is_process_running(pid) {
      "still_running"
    } else {
      "terminated"
    };
    let profile = config
      .as_ref()
      .and_then(|config| config.profile_id.as_deref())
      .unwrap_or("none");
    let browser_pid = config
      .as_ref()
      .and_then(|config| config.browser_pid)
      .map(|pid| pid.to_string())
      .unwrap_or_else(|| "none".to_string());
    log::info!(
      "Proxy worker stopped id={id} pid={pid} profile={profile} browser_pid={browser_pid} reason={reason} how={how}"
    );
    return Ok(true);
  }

  Ok(false)
}

/// The scheme of an upstream URL, never its host or credentials.
fn upstream_scheme(upstream: &str) -> &str {
  match upstream.split_once("://") {
    Some((scheme, _)) => scheme,
    None if upstream == "DIRECT" => "direct",
    None => "unknown",
  }
}

pub async fn stop_all_proxy_processes() -> Result<(), Box<dyn std::error::Error>> {
  let configs = list_proxy_configs();
  for config in configs {
    let _ = stop_proxy_process(&config.id).await;
  }
  Ok(())
}

#[cfg(test)]
mod tests {
  use super::{
    is_executable_file, parse_sidecar_version, prune_stale_proxy_logs, target_binary_name,
  };
  use std::fs;
  use std::time::Duration;

  #[test]
  fn parses_exact_sidecar_version_output() {
    assert_eq!(
      parse_sidecar_version(b"donut-proxy v0.28.2\n").as_deref(),
      Some("v0.28.2")
    );
    assert_eq!(
      parse_sidecar_version(b"donut-proxy nightly-2026-07-19-a4ed5c8\r\n").as_deref(),
      Some("nightly-2026-07-19-a4ed5c8")
    );
  }

  #[test]
  fn rejects_missing_or_ambiguous_sidecar_version_output() {
    assert_eq!(parse_sidecar_version(b""), None);
    assert_eq!(parse_sidecar_version(b"donut-proxy"), None);
    assert_eq!(parse_sidecar_version(b"other-proxy v0.28.2"), None);
    assert_eq!(
      parse_sidecar_version(b"donut-proxy v0.28.2\nunexpected"),
      None
    );
  }

  #[test]
  fn sidecar_target_name_is_exact_and_metadata_files_are_not_executables() {
    let target_name = target_binary_name("xray");
    assert!(target_name.starts_with("xray-"));
    assert!(target_name.contains(env!("DONUT_BUILD_TARGET")));

    let temp = tempfile::tempdir().unwrap();
    let marker = temp.path().join(format!("{target_name}.source.json"));
    fs::write(&marker, "{}").unwrap();
    assert!(!is_executable_file(&marker));

    let executable = temp.path().join(target_name);
    fs::write(&executable, "binary").unwrap();
    #[cfg(unix)]
    {
      use std::os::unix::fs::PermissionsExt;
      fs::set_permissions(&executable, fs::Permissions::from_mode(0o755)).unwrap();
    }
    assert!(is_executable_file(&executable));
  }

  #[test]
  fn prunes_only_old_proxy_logs() {
    let temp = tempfile::tempdir().unwrap();
    for id in ["oldest", "middle", "newest"] {
      fs::write(temp.path().join(format!("donut-proxy-{id}.log")), id).unwrap();
      std::thread::sleep(Duration::from_millis(10));
    }
    fs::write(temp.path().join("unrelated.log"), "keep").unwrap();

    prune_stale_proxy_logs(temp.path(), 2);

    assert!(!temp.path().join("donut-proxy-oldest.log").exists());
    assert!(temp.path().join("donut-proxy-middle.log").exists());
    assert!(temp.path().join("donut-proxy-newest.log").exists());
    assert!(temp.path().join("unrelated.log").exists());
  }
}