/* 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 https://mozilla.org/MPL/2.0/. */

use std::fmt;

use embedder_traits::UntrustedNodeAddress;
use euclid::default::Point2D;
use layout_api::{NodesFromPointQueryType, QueryMsg};
use servo_arc::Arc;
use style::invalidation::media_queries::{MediaListKey, ToMediaListKey};
use style::media_queries::MediaList;
use style::shared_lock::{SharedRwLock as StyleSharedRwLock, SharedRwLockReadGuard};
use style::stylesheets::scope_rule::ImplicitScopeRoot;
use style::stylesheets::{Stylesheet, StylesheetContents};
use stylo_atoms::Atom;

use super::bindings::trace::HashMapTracedValues;
use crate::dom::bindings::cell::DomRefCell;
use crate::dom::bindings::codegen::Bindings::NodeBinding::Node_Binding::NodeMethods;
use crate::dom::bindings::codegen::Bindings::ShadowRootBinding::ShadowRootMethods;
use crate::dom::bindings::inheritance::Castable;
use crate::dom::bindings::num::Finite;
use crate::dom::bindings::root::{Dom, DomRoot};
use crate::dom::element::Element;
use crate::dom::htmlelement::HTMLElement;
use crate::dom::node::{self, Node, VecPreOrderInsertionHelper};
use crate::dom::shadowroot::ShadowRoot;
use crate::dom::types::CSSStyleSheet;
use crate::dom::window::Window;
use crate::script_runtime::CanGc;
use crate::stylesheet_set::StylesheetSetRef;

/// Stylesheet could be constructed by a CSSOM object CSSStylesheet or parsed
/// from HTML element such as `<style>` or `<link>`.
#[derive(Clone, JSTraceable, MallocSizeOf)]
#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
pub(crate) enum StylesheetSource {
    Element(Dom<Element>),
    // TODO(stevennovaryo): This type of enum would not be used until we implement adopted stylesheet
    #[allow(dead_code)]
    Constructed(Dom<CSSStyleSheet>),
}

impl StylesheetSource {
    pub(crate) fn get_cssom_object(&self) -> Option<DomRoot<CSSStyleSheet>> {
        match self {
            StylesheetSource::Element(el) => el.upcast::<Node>().get_cssom_stylesheet(),
            StylesheetSource::Constructed(ss) => Some(ss.as_rooted()),
        }
    }

    pub(crate) fn is_a_valid_owner(&self) -> bool {
        match self {
            StylesheetSource::Element(el) => el.as_stylesheet_owner().is_some(),
            StylesheetSource::Constructed(ss) => ss.is_constructed(),
        }
    }
}

#[derive(Clone, JSTraceable, MallocSizeOf)]
#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
pub(crate) struct ServoStylesheetInDocument {
    #[ignore_malloc_size_of = "Arc"]
    #[no_trace]
    pub(crate) sheet: Arc<Stylesheet>,
    /// The object that owns this stylesheet. For constructed stylesheet, it would be the
    /// CSSOM object itself, and for stylesheet generated by an element, it would be the
    /// html element. This is used to get the CSSOM Stylesheet within a DocumentOrShadowDOM.
    pub(crate) owner: StylesheetSource,
}

// This is necessary because this type is contained within a Stylo type which needs
// Stylo's version of MallocSizeOf.
impl stylo_malloc_size_of::MallocSizeOf for ServoStylesheetInDocument {
    fn size_of(&self, ops: &mut stylo_malloc_size_of::MallocSizeOfOps) -> usize {
        <ServoStylesheetInDocument as malloc_size_of::MallocSizeOf>::size_of(self, ops)
    }
}

impl fmt::Debug for ServoStylesheetInDocument {
    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
        self.sheet.fmt(formatter)
    }
}

impl PartialEq for ServoStylesheetInDocument {
    fn eq(&self, other: &Self) -> bool {
        Arc::ptr_eq(&self.sheet, &other.sheet)
    }
}

impl ToMediaListKey for ServoStylesheetInDocument {
    fn to_media_list_key(&self) -> MediaListKey {
        self.sheet.contents.to_media_list_key()
    }
}

impl ::style::stylesheets::StylesheetInDocument for ServoStylesheetInDocument {
    fn enabled(&self) -> bool {
        self.sheet.enabled()
    }

    fn media<'a>(&'a self, guard: &'a SharedRwLockReadGuard) -> Option<&'a MediaList> {
        self.sheet.media(guard)
    }

    fn contents(&self) -> &StylesheetContents {
        self.sheet.contents()
    }

    fn implicit_scope_root(&self) -> Option<ImplicitScopeRoot> {
        None
    }
}

// https://w3c.github.io/webcomponents/spec/shadow/#extensions-to-the-documentorshadowroot-mixin
#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
#[derive(Clone, JSTraceable, MallocSizeOf)]
pub(crate) struct DocumentOrShadowRoot {
    window: Dom<Window>,
}

impl DocumentOrShadowRoot {
    pub(crate) fn new(window: &Window) -> Self {
        Self {
            window: Dom::from_ref(window),
        }
    }

    pub(crate) fn nodes_from_point(
        &self,
        client_point: &Point2D<f32>,
        query_type: NodesFromPointQueryType,
        can_gc: CanGc,
    ) -> Vec<UntrustedNodeAddress> {
        self.window
            .layout_reflow(QueryMsg::NodesFromPointQuery, can_gc);
        self.window
            .layout()
            .query_nodes_from_point(*client_point, query_type)
    }

    #[allow(unsafe_code)]
    // https://drafts.csswg.org/cssom-view/#dom-document-elementfrompoint
    pub(crate) fn element_from_point(
        &self,
        x: Finite<f64>,
        y: Finite<f64>,
        document_element: Option<DomRoot<Element>>,
        has_browsing_context: bool,
        can_gc: CanGc,
    ) -> Option<DomRoot<Element>> {
        let x = *x as f32;
        let y = *y as f32;
        let point = &Point2D::new(x, y);
        let viewport = self.window.viewport_details().size;

        if !has_browsing_context {
            return None;
        }

        if x < 0.0 || y < 0.0 || x > viewport.width || y > viewport.height {
            return None;
        }

        match self
            .nodes_from_point(point, NodesFromPointQueryType::Topmost, can_gc)
            .first()
        {
            Some(address) => {
                let node = unsafe { node::from_untrusted_node_address(*address) };
                let parent_node = node.GetParentNode().unwrap();
                let shadow_host = parent_node
                    .downcast::<ShadowRoot>()
                    .map(ShadowRootMethods::Host);
                let element_ref = node
                    .downcast::<Element>()
                    .or(shadow_host.as_deref())
                    .unwrap_or_else(|| {
                        parent_node
                            .downcast::<Element>()
                            .expect("Hit node should have an element or shadowroot parent")
                    });

                Some(DomRoot::from_ref(element_ref))
            },
            None => document_element,
        }
    }

    #[allow(unsafe_code)]
    // https://drafts.csswg.org/cssom-view/#dom-document-elementsfrompoint
    pub(crate) fn elements_from_point(
        &self,
        x: Finite<f64>,
        y: Finite<f64>,
        document_element: Option<DomRoot<Element>>,
        has_browsing_context: bool,
        can_gc: CanGc,
    ) -> Vec<DomRoot<Element>> {
        let x = *x as f32;
        let y = *y as f32;
        let point = &Point2D::new(x, y);
        let viewport = self.window.viewport_details().size;

        if !has_browsing_context {
            return vec![];
        }

        // Step 2
        if x < 0.0 || y < 0.0 || x > viewport.width || y > viewport.height {
            return vec![];
        }

        // Step 1 and Step 3
        let nodes = self.nodes_from_point(point, NodesFromPointQueryType::All, can_gc);
        let mut elements: Vec<DomRoot<Element>> = nodes
            .iter()
            .flat_map(|&untrusted_node_address| {
                let node = unsafe { node::from_untrusted_node_address(untrusted_node_address) };
                DomRoot::downcast::<Element>(node)
            })
            .collect();

        // Step 4
        if let Some(root_element) = document_element {
            if elements.last() != Some(&root_element) {
                elements.push(root_element);
            }
        }

        // Step 5
        elements
    }

    // https://html.spec.whatwg.org/multipage/#dom-document-activeelement
    pub(crate) fn get_active_element(
        &self,
        focused_element: Option<DomRoot<Element>>,
        body: Option<DomRoot<HTMLElement>>,
        document_element: Option<DomRoot<Element>>,
    ) -> Option<DomRoot<Element>> {
        // TODO: Step 2.

        match focused_element {
            Some(element) => Some(element), // Step 3. and 4.
            None => match body {
                // Step 5.
                Some(body) => Some(DomRoot::upcast(body)),
                None => document_element,
            },
        }
    }

    /// Remove a stylesheet owned by `owner` from the list of document sheets.
    #[cfg_attr(crown, allow(crown::unrooted_must_root))] // Owner needs to be rooted already necessarily.
    pub(crate) fn remove_stylesheet(
        owner: StylesheetSource,
        s: &Arc<Stylesheet>,
        mut stylesheets: StylesheetSetRef<ServoStylesheetInDocument>,
    ) {
        let guard = s.shared_lock.read();

        // FIXME(emilio): Would be nice to remove the clone, etc.
        stylesheets.remove_stylesheet(
            None,
            ServoStylesheetInDocument {
                sheet: s.clone(),
                owner,
            },
            &guard,
        );
    }

    /// Add a stylesheet owned by `owner` to the list of document sheets, in the
    /// correct tree position.
    #[cfg_attr(crown, allow(crown::unrooted_must_root))] // Owner needs to be rooted already necessarily.
    pub(crate) fn add_stylesheet(
        owner: StylesheetSource,
        mut stylesheets: StylesheetSetRef<ServoStylesheetInDocument>,
        sheet: Arc<Stylesheet>,
        insertion_point: Option<ServoStylesheetInDocument>,
        style_shared_lock: &StyleSharedRwLock,
    ) {
        debug_assert!(owner.is_a_valid_owner(), "Wat");

        let sheet = ServoStylesheetInDocument { sheet, owner };

        let guard = style_shared_lock.read();

        match insertion_point {
            Some(ip) => {
                stylesheets.insert_stylesheet_before(None, sheet, ip, &guard);
            },
            None => {
                stylesheets.append_stylesheet(None, sheet, &guard);
            },
        }
    }

    /// Remove any existing association between the provided id/name and any elements in this document.
    pub(crate) fn unregister_named_element(
        &self,
        id_map: &DomRefCell<HashMapTracedValues<Atom, Vec<Dom<Element>>>>,
        to_unregister: &Element,
        id: &Atom,
    ) {
        debug!(
            "Removing named element {:p}: {:p} id={}",
            self, to_unregister, id
        );
        let mut id_map = id_map.borrow_mut();
        let is_empty = match id_map.get_mut(id) {
            None => false,
            Some(elements) => {
                let position = elements
                    .iter()
                    .position(|element| &**element == to_unregister)
                    .expect("This element should be in registered.");
                elements.remove(position);
                elements.is_empty()
            },
        };
        if is_empty {
            id_map.remove(id);
        }
    }

    /// Associate an element present in this document with the provided id/name.
    pub(crate) fn register_named_element(
        &self,
        id_map: &DomRefCell<HashMapTracedValues<Atom, Vec<Dom<Element>>>>,
        element: &Element,
        id: &Atom,
        root: DomRoot<Node>,
    ) {
        debug!("Adding named element {:p}: {:p} id={}", self, element, id);
        assert!(
            element.upcast::<Node>().is_in_a_document_tree() ||
                element.upcast::<Node>().is_in_a_shadow_tree()
        );
        assert!(!id.is_empty());
        let mut id_map = id_map.borrow_mut();
        let elements = id_map.entry(id.clone()).or_default();
        elements.insert_pre_order(element, &root);
    }
}