/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

//! Abstractions for global scopes.
//!
//! This module contains smart pointers to global scopes, to simplify writing
//! code that works in workers as well as window scopes.

use devtools_traits::{ScriptToDevtoolsControlMsg, WorkerId};
use dom::bindings::codegen::Bindings::WindowBinding::WindowMethods;
use dom::bindings::conversions::root_from_object;
use dom::bindings::js::Root;
use dom::bindings::reflector::{Reflectable, Reflector};
use dom::window::{self, ScriptHelpers};
use dom::workerglobalscope::WorkerGlobalScope;
use ipc_channel::ipc::IpcSender;
use js::jsapi::{CurrentGlobalOrNull, GetGlobalForObjectCrossCompartment};
use js::jsapi::{JSContext, JSObject, JS_GetClass, MutableHandleValue};
use js::{JSCLASS_IS_DOMJSCLASS, JSCLASS_IS_GLOBAL};
use msg::constellation_msg::{PipelineId, PanicMsg};
use net_traits::{CoreResourceThread, RequestSource};
use profile_traits::{mem, time};
use script_runtime::{CommonScriptMsg, ScriptChan, ScriptPort};
use script_thread::{MainThreadScriptChan, ScriptThread};
use script_traits::{MsDuration, ScriptMsg as ConstellationMsg, TimerEventRequest};
use task_source::TaskSource;
use task_source::dom_manipulation::DOMManipulationTask;
use timers::{OneshotTimerCallback, OneshotTimerHandle};
use url::Url;

/// A freely-copyable reference to a rooted global object.
#[derive(Copy, Clone)]
pub enum GlobalRef<'a> {
    /// A reference to a `Window` object.
    Window(&'a window::Window),
    /// A reference to a `WorkerGlobalScope` object.
    Worker(&'a WorkerGlobalScope),
}

/// A stack-based rooted reference to a global object.
pub enum GlobalRoot {
    /// A root for a `Window` object.
    Window(Root<window::Window>),
    /// A root for a `WorkerGlobalScope` object.
    Worker(Root<WorkerGlobalScope>),
}

impl<'a> GlobalRef<'a> {
    /// Get the `JSContext` for the `JSRuntime` associated with the thread
    /// this global object is on.
    pub fn get_cx(&self) -> *mut JSContext {
        match *self {
            GlobalRef::Window(ref window) => window.get_cx(),
            GlobalRef::Worker(ref worker) => worker.get_cx(),
        }
    }

    /// Extract a `Window`, causing thread failure if the global object is not
    /// a `Window`.
    pub fn as_window(&self) -> &window::Window {
        match *self {
            GlobalRef::Window(window) => window,
            GlobalRef::Worker(_) => panic!("expected a Window scope"),
        }
    }

    /// gets the custom message channel associated with global object
    pub fn request_source(&self) -> RequestSource {
        match *self {
            GlobalRef::Window(ref window) => RequestSource::Window(window.custom_message_chan()),
            GlobalRef::Worker(ref worker) => RequestSource::Worker(worker.custom_message_chan()),
        }
    }

    /// Get the `PipelineId` for this global scope.
    pub fn pipeline(&self) -> PipelineId {
        match *self {
            GlobalRef::Window(window) => window.pipeline(),
            GlobalRef::Worker(worker) => worker.pipeline(),
        }
    }

    /// Get a `mem::ProfilerChan` to send messages to the memory profiler thread.
    pub fn mem_profiler_chan(&self) -> &mem::ProfilerChan {
        match *self {
            GlobalRef::Window(window) => window.mem_profiler_chan(),
            GlobalRef::Worker(worker) => worker.mem_profiler_chan(),
        }
    }

    /// Get a `time::ProfilerChan` to send messages to the time profiler thread.
    pub fn time_profiler_chan(&self) -> &time::ProfilerChan {
        match *self {
            GlobalRef::Window(window) => window.time_profiler_chan(),
            GlobalRef::Worker(worker) => worker.time_profiler_chan(),
        }
    }

    /// Get a `IpcSender` to send messages to the constellation when available.
    pub fn constellation_chan(&self) -> &IpcSender<ConstellationMsg> {
        match *self {
            GlobalRef::Window(window) => window.constellation_chan(),
            GlobalRef::Worker(worker) => worker.constellation_chan(),
        }
    }

    /// Get the scheduler channel to request timer events.
    pub fn scheduler_chan(&self) -> &IpcSender<TimerEventRequest> {
        match *self {
            GlobalRef::Window(window) => window.scheduler_chan(),
            GlobalRef::Worker(worker) => worker.scheduler_chan(),
        }
    }

    /// Get an `IpcSender<ScriptToDevtoolsControlMsg>` to send messages to Devtools
    /// thread when available.
    pub fn devtools_chan(&self) -> Option<IpcSender<ScriptToDevtoolsControlMsg>> {
        match *self {
            GlobalRef::Window(window) => window.devtools_chan(),
            GlobalRef::Worker(worker) => worker.devtools_chan(),
        }
    }

    /// Get the `CoreResourceThread` for this global scope.
    pub fn core_resource_thread(&self) -> CoreResourceThread {
        match *self {
            GlobalRef::Window(ref window) => {
                let doc = window.Document();
                let doc = doc.r();
                let loader = doc.loader();
                (*loader.resource_thread).clone()
            }
            GlobalRef::Worker(ref worker) => worker.core_resource_thread().clone(),
        }
    }

    /// Get the worker's id.
    pub fn get_worker_id(&self) -> Option<WorkerId> {
        match *self {
            GlobalRef::Window(_) => None,
            GlobalRef::Worker(ref worker) => Some(worker.get_worker_id()),
        }
    }

    /// Get next worker id.
    pub fn get_next_worker_id(&self) -> WorkerId {
        match *self {
            GlobalRef::Window(ref window) => window.get_next_worker_id(),
            GlobalRef::Worker(ref worker) => worker.get_next_worker_id(),
        }
    }

    /// Get the URL for this global scope.
    pub fn get_url(&self) -> Url {
        match *self {
            GlobalRef::Window(ref window) => window.get_url(),
            GlobalRef::Worker(ref worker) => worker.get_url().clone(),
        }
    }

    /// Get the [base url](https://html.spec.whatwg.org/multipage/#api-base-url)
    /// for this global scope.
    pub fn api_base_url(&self) -> Url {
        match *self {
            // https://html.spec.whatwg.org/multipage/#script-settings-for-browsing-contexts:api-base-url
            GlobalRef::Window(ref window) => window.Document().base_url(),
            // https://html.spec.whatwg.org/multipage/#script-settings-for-workers:api-base-url
            GlobalRef::Worker(ref worker) => worker.get_url().clone(),
        }
    }

    /// `ScriptChan` used to send messages to the event loop of this global's
    /// thread.
    pub fn script_chan(&self) -> Box<ScriptChan + Send> {
        match *self {
            GlobalRef::Window(ref window) =>
                MainThreadScriptChan(window.main_thread_script_chan().clone()).clone(),
            GlobalRef::Worker(ref worker) => worker.script_chan(),
        }
    }

    /// `TaskSource` used to queue DOM manipulation messages to the event loop of this global's
    /// thread.
    pub fn dom_manipulation_task_source(&self) -> Box<TaskSource<DOMManipulationTask> + Send> {
        match *self {
            GlobalRef::Window(ref window) => window.dom_manipulation_task_source(),
            GlobalRef::Worker(_) => unimplemented!(),
        }
    }

    /// `ScriptChan` used to send messages to the event loop of this global's
    /// thread.
    pub fn networking_task_source(&self) -> Box<ScriptChan + Send> {
        match *self {
            GlobalRef::Window(ref window) => window.networking_task_source(),
            GlobalRef::Worker(ref worker) => worker.script_chan(),
        }
    }

    /// `ScriptChan` used to send messages to the event loop of this global's
    /// thread.
    pub fn history_traversal_task_source(&self) -> Box<ScriptChan + Send> {
        match *self {
            GlobalRef::Window(ref window) => window.history_traversal_task_source(),
            GlobalRef::Worker(ref worker) => worker.script_chan(),
        }
    }

    /// `ScriptChan` used to send messages to the event loop of this global's
    /// thread.
    pub fn file_reading_task_source(&self) -> Box<ScriptChan + Send> {
        match *self {
            GlobalRef::Window(ref window) => window.file_reading_task_source(),
            GlobalRef::Worker(ref worker) => worker.script_chan(),
        }
    }

    /// Create a new sender/receiver pair that can be used to implement an on-demand
    /// event loop. Used for implementing web APIs that require blocking semantics
    /// without resorting to nested event loops.
    pub fn new_script_pair(&self) -> (Box<ScriptChan + Send>, Box<ScriptPort + Send>) {
        match *self {
            GlobalRef::Window(ref window) => window.new_script_pair(),
            GlobalRef::Worker(ref worker) => worker.new_script_pair(),
        }
    }

    /// Process a single event as if it were the next event in the thread queue for
    /// this global.
    pub fn process_event(&self, msg: CommonScriptMsg) {
        match *self {
            GlobalRef::Window(_) => ScriptThread::process_event(msg),
            GlobalRef::Worker(ref worker) => worker.process_event(msg),
        }
    }

    /// Evaluate the JS messages on the `RootedValue` of this global
    pub fn evaluate_js_on_global_with_result(&self, code: &str, rval: MutableHandleValue) {
        match *self {
            GlobalRef::Window(window) => window.evaluate_js_on_global_with_result(code, rval),
            GlobalRef::Worker(worker) => worker.evaluate_js_on_global_with_result(code, rval),
        }
    }

    /// Set the `bool` value to indicate whether developer tools has requested
    /// updates from the global
    pub fn set_devtools_wants_updates(&self, send_updates: bool) {
        match *self {
            GlobalRef::Window(window) => window.set_devtools_wants_updates(send_updates),
            GlobalRef::Worker(worker) => worker.set_devtools_wants_updates(send_updates),
        }
    }

    /// Schedule the given `callback` to be invoked after at least `duration` milliseconds have
    /// passed.
    pub fn schedule_callback(&self,
                             callback: OneshotTimerCallback,
                             duration: MsDuration)
                             -> OneshotTimerHandle {
        match *self {
            GlobalRef::Window(window) => window.schedule_callback(callback, duration),
            GlobalRef::Worker(worker) => worker.schedule_callback(callback, duration),
        }
    }

    /// Unschedule a previously-scheduled callback.
    pub fn unschedule_callback(&self, handle: OneshotTimerHandle) {
        match *self {
            GlobalRef::Window(window) => window.unschedule_callback(handle),
            GlobalRef::Worker(worker) => worker.unschedule_callback(handle),
        }
    }

    /// Returns the receiver's reflector.
    pub fn reflector(&self) -> &Reflector {
        match *self {
            GlobalRef::Window(ref window) => window.reflector(),
            GlobalRef::Worker(ref worker) => worker.reflector(),
        }
    }

    /// Returns an `IpcSender` to report panics on.
    pub fn panic_chan(&self) -> &IpcSender<PanicMsg> {
        match *self {
            GlobalRef::Window(ref window) => window.panic_chan(),
            GlobalRef::Worker(ref worker) => worker.panic_chan(),
        }
    }
}

impl GlobalRoot {
    /// Obtain a safe reference to the global object that cannot outlive the
    /// lifetime of this root.
    pub fn r(&self) -> GlobalRef {
        match *self {
            GlobalRoot::Window(ref window) => GlobalRef::Window(window.r()),
            GlobalRoot::Worker(ref worker) => GlobalRef::Worker(worker.r()),
        }
    }
}

/// Returns the global object of the realm that the given DOM object's reflector was created in.
pub fn global_root_from_reflector<T: Reflectable>(reflector: &T) -> GlobalRoot {
    global_root_from_object(*reflector.reflector().get_jsobject())
}

/// Returns the Rust global object from a JS global object.
#[allow(unrooted_must_root)]
pub fn global_root_from_global(global: *mut JSObject) -> GlobalRoot {
    unsafe {
        let clasp = JS_GetClass(global);
        assert!(((*clasp).flags & (JSCLASS_IS_DOMJSCLASS | JSCLASS_IS_GLOBAL)) != 0);
        match root_from_object(global) {
            Ok(window) => return GlobalRoot::Window(window),
            Err(_) => (),
        }

        match root_from_object(global) {
            Ok(worker) => return GlobalRoot::Worker(worker),
            Err(_) => (),
        }

        panic!("found DOM global that doesn't unwrap to Window or WorkerGlobalScope")
    }
}

/// Returns the global object of the realm that the given JS object was created in.
#[allow(unrooted_must_root)]
pub fn global_root_from_object(obj: *mut JSObject) -> GlobalRoot {
    unsafe {
        let global = GetGlobalForObjectCrossCompartment(obj);
        global_root_from_global(global)
    }
}

/// Returns the global object for the given JSContext
#[allow(unrooted_must_root)]
pub fn global_root_from_context(cx: *mut JSContext) -> GlobalRoot {
    unsafe {
        let global = CurrentGlobalOrNull(cx);
        assert!(!global.is_null());
        global_root_from_global(global)
    }
}