// Copyright 2019-2021 Tauri Programme within The Commons Conservancy
// SPDX-License-Identifier: Apache-2.0
// SPDX-License-Identifier: MIT

use std::{
  collections::{HashMap, HashSet},
  fmt,
  path::{Path, PathBuf},
  sync::{Arc, Mutex},
};

pub use glob::Pattern;
use tauri_utils::{
  config::{Config, FsAllowlistScope},
  Env, PackageInfo,
};
use uuid::Uuid;

use crate::api::path::parse as parse_path;

/// Scope change event.
#[derive(Debug, Clone)]
pub enum Event {
  /// A path has been allowed.
  PathAllowed(PathBuf),
  /// A path has been forbidden.
  PathForbidden(PathBuf),
}

type EventListener = Box<dyn Fn(&Event) + Send>;

/// Scope for filesystem access.
#[derive(Clone)]
pub struct Scope {
  alllowed_patterns: Arc<Mutex<HashSet<Pattern>>>,
  forbidden_patterns: Arc<Mutex<HashSet<Pattern>>>,
  event_listeners: Arc<Mutex<HashMap<Uuid, EventListener>>>,
}

impl fmt::Debug for Scope {
  fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
    f.debug_struct("Scope")
      .field(
        "alllowed_patterns",
        &self
          .alllowed_patterns
          .lock()
          .unwrap()
          .iter()
          .map(|p| p.as_str())
          .collect::<Vec<&str>>(),
      )
      .field(
        "forbidden_patterns",
        &self
          .forbidden_patterns
          .lock()
          .unwrap()
          .iter()
          .map(|p| p.as_str())
          .collect::<Vec<&str>>(),
      )
      .finish()
  }
}

fn push_pattern<P: AsRef<Path>>(list: &mut HashSet<Pattern>, pattern: P) -> crate::Result<()> {
  let path: PathBuf = pattern.as_ref().components().collect();
  list.insert(Pattern::new(&path.to_string_lossy())?);
  #[cfg(windows)]
  {
    if let Ok(p) = std::fs::canonicalize(&path) {
      list.insert(Pattern::new(&p.to_string_lossy())?);
    } else {
      list.insert(Pattern::new(&format!("\\\\?\\{}", path.display()))?);
    }
  }
  Ok(())
}

impl Scope {
  /// Creates a new scope from a `FsAllowlistScope` configuration.
  pub(crate) fn for_fs_api(
    config: &Config,
    package_info: &PackageInfo,
    env: &Env,
    scope: &FsAllowlistScope,
  ) -> crate::Result<Self> {
    let mut alllowed_patterns = HashSet::new();
    for path in scope.allowed_paths() {
      if let Ok(path) = parse_path(config, package_info, env, path) {
        push_pattern(&mut alllowed_patterns, path)?;
      }
    }

    let mut forbidden_patterns = HashSet::new();
    if let Some(forbidden_paths) = scope.forbidden_paths() {
      for path in forbidden_paths {
        if let Ok(path) = parse_path(config, package_info, env, path) {
          push_pattern(&mut forbidden_patterns, path)?;
        }
      }
    }

    Ok(Self {
      alllowed_patterns: Arc::new(Mutex::new(alllowed_patterns)),
      forbidden_patterns: Arc::new(Mutex::new(forbidden_patterns)),
      event_listeners: Default::default(),
    })
  }

  /// The list of allowed patterns.
  pub fn allowed_patterns(&self) -> HashSet<Pattern> {
    self.alllowed_patterns.lock().unwrap().clone()
  }

  /// The list of forbidden patterns.
  pub fn forbidden_patterns(&self) -> HashSet<Pattern> {
    self.forbidden_patterns.lock().unwrap().clone()
  }

  /// Listen to an event on this scope.
  pub fn listen<F: Fn(&Event) + Send + 'static>(&self, f: F) -> Uuid {
    let id = Uuid::new_v4();
    self.event_listeners.lock().unwrap().insert(id, Box::new(f));
    id
  }

  fn trigger(&self, event: Event) {
    let listeners = self.event_listeners.lock().unwrap();
    let handlers = listeners.values();
    for listener in handlers {
      listener(&event);
    }
  }

  /// Extend the allowed patterns with the given directory.
  ///
  /// After this function has been called, the frontend will be able to use the Tauri API to read
  /// the directory and all of its files and subdirectories.
  pub fn allow_directory<P: AsRef<Path>>(&self, path: P, recursive: bool) -> crate::Result<()> {
    let path = path.as_ref().to_path_buf();
    {
      let mut list = self.alllowed_patterns.lock().unwrap();

      // allow the directory to be read
      push_pattern(&mut list, &path)?;
      // allow its files and subdirectories to be read
      push_pattern(&mut list, path.join(if recursive { "**" } else { "*" }))?;
    }
    self.trigger(Event::PathAllowed(path));
    Ok(())
  }

  /// Extend the allowed patterns with the given file path.
  ///
  /// After this function has been called, the frontend will be able to use the Tauri API to read the contents of this file.
  pub fn allow_file<P: AsRef<Path>>(&self, path: P) -> crate::Result<()> {
    let path = path.as_ref();
    push_pattern(&mut self.alllowed_patterns.lock().unwrap(), &path)?;
    self.trigger(Event::PathAllowed(path.to_path_buf()));
    Ok(())
  }

  /// Set the given directory path to be forbidden by this scope.
  ///
  /// **Note:** this takes precedence over allowed paths, so its access gets denied **always**.
  pub fn forbid_directory<P: AsRef<Path>>(&self, path: P, recursive: bool) -> crate::Result<()> {
    let path = path.as_ref().to_path_buf();
    {
      let mut list = self.forbidden_patterns.lock().unwrap();

      // allow the directory to be read
      push_pattern(&mut list, &path)?;
      // allow its files and subdirectories to be read
      push_pattern(&mut list, path.join(if recursive { "**" } else { "*" }))?;
    }
    self.trigger(Event::PathForbidden(path));
    Ok(())
  }

  /// Set the given file path to be forbidden by this scope.
  ///
  /// **Note:** this takes precedence over allowed paths, so its access gets denied **always**.
  pub fn forbid_file<P: AsRef<Path>>(&self, path: P) -> crate::Result<()> {
    let path = path.as_ref();
    push_pattern(&mut self.forbidden_patterns.lock().unwrap(), &path)?;
    self.trigger(Event::PathForbidden(path.to_path_buf()));
    Ok(())
  }

  /// Determines if the given path is allowed on this scope.
  pub fn is_allowed<P: AsRef<Path>>(&self, path: P) -> bool {
    let path = path.as_ref();
    let path = if !path.exists() {
      crate::Result::Ok(path.to_path_buf())
    } else {
      std::fs::canonicalize(path).map_err(Into::into)
    };

    if let Ok(path) = path {
      let path: PathBuf = path.components().collect();

      let forbidden = self
        .forbidden_patterns
        .lock()
        .unwrap()
        .iter()
        .any(|p| p.matches_path(&path));

      if forbidden {
        false
      } else {
        let allowed = self
          .alllowed_patterns
          .lock()
          .unwrap()
          .iter()
          .any(|p| p.matches_path(&path));
        allowed
      }
    } else {
      false
    }
  }
}