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

//! [`WebView`] struct and associated types.

mod web_context;

pub use web_context::WebContext;

#[cfg(any(
  target_os = "linux",
  target_os = "dragonfly",
  target_os = "freebsd",
  target_os = "netbsd",
  target_os = "openbsd"
))]
mod webkitgtk;
#[cfg(any(
  target_os = "linux",
  target_os = "dragonfly",
  target_os = "freebsd",
  target_os = "netbsd",
  target_os = "openbsd"
))]
use webkitgtk::*;
#[cfg(any(target_os = "macos", target_os = "ios"))]
mod wkwebview;
#[cfg(any(target_os = "macos", target_os = "ios"))]
use wkwebview::*;
#[cfg(target_os = "windows")]
mod webview2;
#[cfg(target_os = "windows")]
use self::webview2::*;

use crate::{Error, Result};

use std::{path::PathBuf, rc::Rc};

use serde_json::Value;
use url::Url;

#[cfg(target_os = "windows")]
use crate::application::platform::windows::WindowExtWindows;
use crate::application::window::Window;

pub struct WebViewAttributes {
  /// Whether the WebView window should be visible.
  pub visible: bool,
  /// Whether the WebView should be transparent.
  pub transparent: bool,
  /// Whether load the provided URL to [`WebView`].
  pub url: Option<Url>,
  /// Whether load the provided html string to [`WebView`].
  /// This will be ignored if the `url` is provided.
  ///
  /// # Warning
  /// The loaded from html string will have different Origin on different platforms. And
  /// servers which enforce CORS will need to add exact same Origin header in `Access-Control-Allow-Origin`
  /// if you wish to send requests with native `fetch` and `XmlHttpRequest` APIs. Here are the
  /// different Origin headers across platforms:
  ///
  /// - macOS: `http://localhost`
  /// - Linux: `http://localhost`
  /// - Windows: `null`
  pub html: Option<String>,
  /// Initialize javascript code when loading new pages. When webview load a new page, this
  /// initialization code will be executed. It is guaranteed that code is executed before
  /// `window.onload`.
  pub initialization_scripts: Vec<String>,
  /// Register custom file loading protocols with pairs of scheme uri string and a handling
  /// closure.
  ///
  /// The closure takes a url string slice, and returns a two item tuple of a vector of
  /// bytes which is the content and a mimetype string of the content.
  ///
  /// # Warning
  /// Pages loaded from custom protocol will have different Origin on different platforms. And
  /// servers which enforce CORS will need to add exact same Origin header in `Access-Control-Allow-Origin`
  /// if you wish to send requests with native `fetch` and `XmlHttpRequest` APIs. Here are the
  /// different Origin headers across platforms:
  ///
  /// - macOS: `<scheme_name>://<path>` (so it will be `wry://examples` in `custom_protocol` example)
  /// - Linux: Though it's same as macOS, there's a [bug] that Origin header in the request will be
  /// empty. So the only way to pass the server is setting `Access-Control-Allow-Origin: *`.
  /// - Windows: `https://<scheme_name>.<path>` (so it will be `https://wry.examples` in `custom_protocol` example)
  ///
  /// [bug]: https://bugs.webkit.org/show_bug.cgi?id=229034
  pub custom_protocols: Vec<(String, Box<dyn Fn(&str) -> Result<(Vec<u8>, String)>>)>,
  /// Set the RPC handler to Communicate between the host Rust code and Javascript on webview.
  ///
  /// The communication is done via [JSON-RPC](https://www.jsonrpc.org). Users can use this to register an incoming
  /// request handler and reply with responses that are passed back to Javascript. On the Javascript
  /// side the client is exposed via `window.rpc` with two public methods:
  ///
  /// 1. The `call()` function accepts a method name and parameters and expects a reply.
  /// 2. The `notify()` function accepts a method name and parameters but does not expect a reply.
  ///
  /// Both functions return promises but `notify()` resolves immediately.
  pub rpc_handler: Option<Box<dyn Fn(&Window, RpcRequest) -> Option<RpcResponse>>>,
  /// Set a handler closure to process incoming [`FileDropEvent`] of the webview.
  ///
  /// # Blocking OS Default Behavior
  /// Return `true` in the callback to block the OS' default behavior of handling a file drop.
  ///
  /// Note, that if you do block this behavior, it won't be possible to drop files on `<input type="file">` forms.
  /// Also note, that it's not possible to manually set the value of a `<input type="file">` via JavaScript for security reasons.
  #[cfg(feature = "file-drop")]
  pub file_drop_handler: Option<Box<dyn Fn(&Window, FileDropEvent) -> bool>>,
  #[cfg(not(feature = "file-drop"))]
  file_drop_handler: Option<Box<dyn Fn(&Window, FileDropEvent) -> bool>>,
}

impl Default for WebViewAttributes {
  fn default() -> Self {
    Self {
      visible: true,
      transparent: false,
      url: None,
      html: None,
      initialization_scripts: vec![],
      custom_protocols: vec![],
      rpc_handler: None,
      file_drop_handler: None,
    }
  }
}

/// Builder type of [`WebView`].
///
/// [`WebViewBuilder`] / [`WebView`] are the basic building blocks to constrcut WebView contents and
/// scripts for those who prefer to control fine grained window creation and event handling.
/// [`WebViewBuilder`] privides ability to setup initialization before web engine starts.
pub struct WebViewBuilder<'a> {
  pub webview: WebViewAttributes,
  web_context: Option<&'a mut WebContext>,
  window: Window,
}

impl<'a> WebViewBuilder<'a> {
  /// Create [`WebViewBuilder`] from provided [`Window`].
  pub fn new(window: Window) -> Result<Self> {
    let webview = WebViewAttributes::default();
    let web_context = None;

    Ok(Self {
      webview,
      web_context,
      window,
    })
  }

  /// Sets whether the WebView should be transparent.
  pub fn with_transparent(mut self, transparent: bool) -> Self {
    self.webview.transparent = transparent;
    self
  }

  /// Sets whether the WebView should be transparent.
  pub fn with_visible(mut self, visible: bool) -> Self {
    self.webview.visible = visible;
    self
  }

  /// Initialize javascript code when loading new pages. When webview load a new page, this
  /// initialization code will be executed. It is guaranteed that code is executed before
  /// `window.onload`.
  pub fn with_initialization_script(mut self, js: &str) -> Self {
    self.webview.initialization_scripts.push(js.to_string());
    self
  }

  /// Register custom file loading protocols with pairs of scheme uri string and a handling
  /// closure.
  ///
  /// The closure takes a url string slice, and returns a two item tuple of a
  /// vector of bytes which is the content and a mimetype string of the content.
  ///
  /// # Warning
  /// Pages loaded from custom protocol will have different Origin on different platforms. And
  /// servers which enforce CORS will need to add exact same Origin header in `Access-Control-Allow-Origin`
  /// if you wish to send requests with native `fetch` and `XmlHttpRequest` APIs. Here are the
  /// different Origin headers across platforms:
  ///
  /// - macOS: `<scheme_name>://<path>` (so it will be `wry://examples` in `custom_protocol` example)
  /// - Linux: Though it's same as macOS, there's a [bug] that Origin header in the request will be
  /// empty. So the only way to pass the server is setting `Access-Control-Allow-Origin: *`.
  /// - Windows: `https://<scheme_name>.<path>` (so it will be `https://wry.examples` in `custom_protocol` example)
  ///
  /// [bug]: https://bugs.webkit.org/show_bug.cgi?id=229034
  #[cfg(feature = "protocol")]
  pub fn with_custom_protocol<F>(mut self, name: String, handler: F) -> Self
  where
    F: Fn(&str) -> Result<(Vec<u8>, String)> + 'static,
  {
    self
      .webview
      .custom_protocols
      .push((name, Box::new(handler)));
    self
  }

  /// Set the RPC handler to Communicate between the host Rust code and Javascript on webview.
  ///
  /// The communication is done via [JSON-RPC](https://www.jsonrpc.org). Users can use this to register an incoming
  /// request handler and reply with responses that are passed back to Javascript. On the Javascript
  /// side the client is exposed via `window.rpc` with two public methods:
  ///
  /// 1. The `call()` function accepts a method name and parameters and expects a reply.
  /// 2. The `notify()` function accepts a method name and parameters but does not expect a reply.
  ///
  /// Both functions return promises but `notify()` resolves immediately.
  pub fn with_rpc_handler<F>(mut self, handler: F) -> Self
  where
    F: Fn(&Window, RpcRequest) -> Option<RpcResponse> + 'static,
  {
    self.webview.rpc_handler = Some(Box::new(handler));
    self
  }

  /// Set a handler closure to process incoming [`FileDropEvent`] of the webview.
  ///
  /// # Blocking OS Default Behavior
  /// Return `true` in the callback to block the OS' default behavior of handling a file drop.
  ///
  /// Note, that if you do block this behavior, it won't be possible to drop files on `<input type="file">` forms.
  /// Also note, that it's not possible to manually set the value of a `<input type="file">` via JavaScript for security reasons.
  #[cfg(feature = "file-drop")]
  pub fn with_file_drop_handler<F>(mut self, handler: F) -> Self
  where
    F: Fn(&Window, FileDropEvent) -> bool + 'static,
  {
    self.webview.file_drop_handler = Some(Box::new(handler));
    self
  }

  /// Load the provided URL when the builder calling [`WebViewBuilder::build`] to create the
  /// [`WebView`]. The provided URL must be valid.
  pub fn with_url(mut self, url: &str) -> Result<Self> {
    self.webview.url = Some(Url::parse(url)?);
    Ok(self)
  }

  /// Load the provided HTML string when the builder calling [`WebViewBuilder::build`] to create the
  /// [`WebView`]. This will be ignored if `url` is already provided.
  ///
  /// # Warning
  /// The Page loaded from html string will have different Origin on different platforms. And
  /// servers which enforce CORS will need to add exact same Origin header in `Access-Control-Allow-Origin`
  /// if you wish to send requests with native `fetch` and `XmlHttpRequest` APIs. Here are the
  /// different Origin headers across platforms:
  ///
  /// - macOS: `http://localhost`
  /// - Linux: `http://localhost`
  /// - Windows: `null`
  pub fn with_html(mut self, html: impl Into<String>) -> Result<Self> {
    self.webview.html = Some(html.into());
    Ok(self)
  }

  /// Set the web context that can share with multiple [`WebView`]s.
  pub fn with_web_context(mut self, web_context: &'a mut WebContext) -> Self {
    self.web_context = Some(web_context);
    self
  }

  /// Consume the builder and create the [`WebView`].
  ///
  /// Platform-specific behavior:
  ///
  /// - **Unix:** This method must be called in a gtk thread. Usually this means it should be
  /// called in the same thread with the [`EventLoop`] you create.
  ///
  /// [`EventLoop`]: crate::application::event_loop::EventLoop
  pub fn build(mut self) -> Result<WebView> {
    if self.webview.rpc_handler.is_some() {
      let js = r#"
            (function() {
                function Rpc() {
                    const self = this;
                    this._promises = {};

                    // Private internal function called on error
                    this._error = (id, error) => {
                        if(this._promises[id]){
                            this._promises[id].reject(error);
                            delete this._promises[id];
                        }
                    }

                    // Private internal function called on result
                    this._result = (id, result) => {
                        if(this._promises[id]){
                            this._promises[id].resolve(result);
                            delete this._promises[id];
                        }
                    }

                    // Call remote method and expect a reply from the handler
                    this.call = function(method) {
                        let array = new Uint32Array(1);
                        window.crypto.getRandomValues(array);
                        const id = array[0];
                        const params = Array.prototype.slice.call(arguments, 1);
                        const payload = {jsonrpc: "2.0", id, method, params};
                        const promise = new Promise((resolve, reject) => {
                            self._promises[id] = {resolve, reject};
                        });
                        window.external.invoke(JSON.stringify(payload));
                        return promise;
                    }

                    // Send a notification without an `id` so no reply is expected.
                    this.notify = function(method) {
                        const params = Array.prototype.slice.call(arguments, 1);
                        const payload = {jsonrpc: "2.0", method, params};
                        window.external.invoke(JSON.stringify(payload));
                        return Promise.resolve();
                    }
                }
                window.external = window.external || {};
                window.external.rpc = new Rpc();
                window.rpc = window.external.rpc;
            })();
            "#;

      self.webview.initialization_scripts.push(js.to_string());
    }
    let window = Rc::new(self.window);
    let webview = InnerWebView::new(window.clone(), self.webview, self.web_context)?;
    Ok(WebView { window, webview })
  }
}

/// The fundamental type to present a [`WebView`].
///
/// [`WebViewBuilder`] / [`WebView`] are the basic building blocks to constrcut WebView contents and
/// scripts for those who prefer to control fine grained window creation and event handling.
/// [`WebView`] presents the actuall WebView window and let you still able to perform actions
/// during event handling to it. [`WebView`] also contains the associate [`Window`] with it.
pub struct WebView {
  window: Rc<Window>,
  webview: InnerWebView,
}

// Signal the Window to drop on Linux and Windows. On mac, we need to handle several unsafe code
// blocks and raw pointer properly.
impl Drop for WebView {
  fn drop(&mut self) {
    #[cfg(any(
      target_os = "linux",
      target_os = "dragonfly",
      target_os = "freebsd",
      target_os = "netbsd",
      target_os = "openbsd"
    ))]
    unsafe {
      use crate::application::platform::unix::WindowExtUnix;
      use gtk::prelude::WidgetExtManual;
      self.window().gtk_window().destroy();
    }
    #[cfg(target_os = "windows")]
    unsafe {
      use winapi::{shared::windef::HWND, um::winuser::DestroyWindow};
      DestroyWindow(self.window.hwnd() as HWND);
    }
  }
}

impl WebView {
  /// Create a [`WebView`] from provided [`Window`]. Note that calling this directly loses
  /// abilities to initialize scripts, add rpc handler, and many more before starting WebView. To
  /// benefit from above features, create a [`WebViewBuilder`] instead.
  ///
  /// Platform-specific behavior:
  ///
  /// - **Unix:** This method must be called in a gtk thread. Usually this means it should be
  /// called in the same thread with the [`EventLoop`] you create.
  ///
  /// [`EventLoop`]: crate::application::event_loop::EventLoop
  pub fn new(window: Window) -> Result<Self> {
    WebViewBuilder::new(window)?.build()
  }

  /// Get the [`Window`] associate with the [`WebView`]. This can let you perform window related
  /// actions.
  pub fn window(&self) -> &Window {
    &self.window
  }

  /// Evaluate and run javascript code. Must be called on the same thread who created the
  /// [`WebView`]. Use [`EventLoopProxy`] and a custom event to send scripts from other threads.
  ///
  /// [`EventLoopProxy`]: crate::application::event_loop::EventLoopProxy
  pub fn evaluate_script(&self, js: &str) -> Result<()> {
    self.webview.eval(js)
  }

  /// Launch print modal for the webview content.
  pub fn print(&self) -> Result<()> {
    self.webview.print();
    Ok(())
  }

  /// Resize the WebView manually. This is only required on Windows because its WebView API doesn't
  /// provide a way to resize automatically.
  pub fn resize(&self) -> Result<()> {
    #[cfg(target_os = "windows")]
    self.webview.resize(self.window.hwnd())?;
    Ok(())
  }

  /// Moves Focus to the Webview control.
  ///
  /// It's usually safe to call `focus` method on `Window` which would also focus to `WebView` except Windows.
  /// Focussing to `Window` doesn't mean focussing to `WebView` on Windows. For example, if you have
  /// an input field on webview and lost focus, you will have to explicitly click the field even you
  /// re-focus the window. And if you focus to `WebView`, it will lost focus to the `Window`.
  pub fn focus(&self) {
    self.webview.focus();
  }
}

// Helper so all platforms handle RPC messages consistently.
fn rpc_proxy(
  window: &Window,
  js: String,
  handler: &dyn Fn(&Window, RpcRequest) -> Option<RpcResponse>,
) -> Result<Option<String>> {
  let req = serde_json::from_str::<RpcRequest>(&js)
    .map_err(|e| Error::RpcScriptError(e.to_string(), js))?;

  let mut response = (handler)(window, req);
  // Got a synchronous response so convert it to a script to be evaluated
  if let Some(mut response) = response.take() {
    if let Some(id) = response.id {
      let js = if let Some(error) = response.error.take() {
        RpcResponse::get_error_script(id, error)?
      } else if let Some(result) = response.result.take() {
        RpcResponse::get_result_script(id, result)?
      } else {
        // No error or result, assume a positive response
        // with empty result (ACK)
        RpcResponse::get_result_script(id, Value::Null)?
      };
      Ok(Some(js))
    } else {
      Ok(None)
    }
  } else {
    Ok(None)
  }
}

const RPC_VERSION: &str = "2.0";

/// RPC request message.
///
/// This usually passes to the [`RpcHandler`] or [`WindowRpcHandler`](crate::WindowRpcHandler) as
/// the parameter. You don't create this by yourself.
#[derive(Debug, Serialize, Deserialize)]
pub struct RpcRequest {
  jsonrpc: String,
  pub id: Option<Value>,
  pub method: String,
  pub params: Option<Value>,
}

/// RPC response message which being sent back to the Javascript side.
#[derive(Debug, Serialize, Deserialize)]
pub struct RpcResponse {
  jsonrpc: String,
  pub(crate) id: Option<Value>,
  pub(crate) result: Option<Value>,
  pub(crate) error: Option<Value>,
}

impl RpcResponse {
  /// Create a new result response.
  pub fn new_result(id: Option<Value>, result: Option<Value>) -> Self {
    Self {
      jsonrpc: RPC_VERSION.to_string(),
      id,
      result,
      error: None,
    }
  }

  /// Create a new error response.
  pub fn new_error(id: Option<Value>, error: Option<Value>) -> Self {
    Self {
      jsonrpc: RPC_VERSION.to_string(),
      id,
      error,
      result: None,
    }
  }

  /// Get a script that resolves the promise with a result.
  pub fn get_result_script(id: Value, result: Value) -> Result<String> {
    let retval = serde_json::to_string(&result)?;
    Ok(format!(
      "window.external.rpc._result({}, {})",
      id.to_string(),
      retval
    ))
  }

  /// Get a script that rejects the promise with an error.
  pub fn get_error_script(id: Value, result: Value) -> Result<String> {
    let retval = serde_json::to_string(&result)?;
    Ok(format!(
      "window.external.rpc._error({}, {})",
      id.to_string(),
      retval
    ))
  }
}

/// An event enumeration sent to [`FileDropHandler`].
#[non_exhaustive]
#[derive(Debug, Serialize, Clone)]
pub enum FileDropEvent {
  /// The file(s) have been dragged onto the window, but have not been dropped yet.
  Hovered(Vec<PathBuf>),
  /// The file(s) have been dropped onto the window.
  Dropped(Vec<PathBuf>),
  /// The file drop was aborted.
  Cancelled,
}

/// Get Webview/Webkit version on current platform.
pub fn webview_version() -> Result<String> {
  platform_webview_version()
}

/// Additional methods on `WebView` that are specific to Windows.
#[cfg(target_os = "windows")]
pub trait WebviewExtWindows {
  /// Returns WebView2 Controller
  fn controller(&self) -> Option<&::webview2::Controller>;
}

#[cfg(target_os = "windows")]
impl WebviewExtWindows for WebView {
  fn controller(&self) -> Option<&::webview2::Controller> {
    self.webview.controller.get()
  }
}

#[cfg(test)]
mod tests {
  use super::*;

  #[test]
  fn should_get_webview_version() {
    if let Err(error) = webview_version() {
      panic!("{}", error);
    }
  }
}