//! Virtual Node Support
//! --------------------
//! VNodes represent lazily-constructed VDom trees that support diffing and event handlers.
//!
//! These VNodes should be *very* cheap and *very* fast to construct - building a full tree should be insanely quick.
use crate::{
    events::VirtualEvent,
    innerlude::{empty_cell, Context, DomTree, ElementId, Properties, Scope, ScopeId, FC},
};
use bumpalo::{boxed::Box as BumpBox, Bump};
use std::{
    cell::{Cell, RefCell},
    fmt::{Arguments, Debug, Formatter},
    marker::PhantomData,
    mem::ManuallyDrop,
    rc::Rc,
};

pub struct VNode<'src> {
    pub kind: VNodeKind<'src>,

    pub(crate) key: Option<&'src str>,
}

impl<'src> VNode<'src> {
    pub fn key(&self) -> Option<&'src str> {
        self.key
    }
    pub fn direct_id(&self) -> ElementId {
        self.try_direct_id().unwrap()
    }
    pub fn try_direct_id(&self) -> Option<ElementId> {
        match &self.kind {
            VNodeKind::Text(el) => el.dom_id.get(),
            VNodeKind::Element(el) => el.dom_id.get(),
            VNodeKind::Anchor(el) => el.dom_id.get(),
            VNodeKind::Fragment(_) => None,
            VNodeKind::Component(_) => None,
            VNodeKind::Suspended(_) => None,
        }
    }
}

/// Tools for the base unit of the virtual dom - the VNode
/// VNodes are intended to be quickly-allocated, lightweight enum values.
///
/// Components will be generating a lot of these very quickly, so we want to
/// limit the amount of heap allocations / overly large enum sizes.
pub enum VNodeKind<'src> {
    Text(VText<'src>),

    Element(&'src VElement<'src>),

    Fragment(VFragment<'src>),

    Component(&'src VComponent<'src>),

    Suspended(VSuspended),

    Anchor(VAnchor),
}

pub struct VAnchor {
    pub dom_id: Cell<Option<ElementId>>,
}

pub struct VText<'src> {
    pub text: &'src str,
    pub dom_id: Cell<Option<ElementId>>,
    pub is_static: bool,
}

pub struct VFragment<'src> {
    pub children: &'src [VNode<'src>],
    pub is_static: bool,
}

pub trait DioxusElement {
    const TAG_NAME: &'static str;
    const NAME_SPACE: Option<&'static str>;
    #[inline]
    fn tag_name(&self) -> &'static str {
        Self::TAG_NAME
    }
    #[inline]
    fn namespace(&self) -> Option<&'static str> {
        Self::NAME_SPACE
    }
}

pub struct VElement<'a> {
    // tag is always static
    pub tag_name: &'static str,
    pub namespace: Option<&'static str>,
    pub dom_id: Cell<Option<ElementId>>,

    pub static_listeners: bool,
    pub listeners: &'a [Listener<'a>],

    pub static_attrs: bool,
    pub attributes: &'a [Attribute<'a>],

    pub static_children: bool,
    pub children: &'a [VNode<'a>],
}

/// An attribute on a DOM node, such as `id="my-thing"` or
/// `href="https://example.com"`.
#[derive(Clone, Debug)]
pub struct Attribute<'a> {
    pub name: &'static str,

    pub value: &'a str,

    pub is_static: bool,

    pub is_volatile: bool,

    // Doesn't exist in the html spec, mostly used to denote "style" tags - could be for any type of group
    pub namespace: Option<&'static str>,
}

/// An event listener.
/// IE onclick, onkeydown, etc
pub struct Listener<'bump> {
    /// The type of event to listen for.
    pub(crate) event: &'static str,

    pub mounted_node: Cell<Option<ElementId>>,

    pub(crate) callback: RefCell<Option<BumpBox<'bump, dyn FnMut(VirtualEvent) + 'bump>>>,
}

impl Listener<'_> {
    // serialize the listener event stuff to a string
    pub fn serialize(&self) {
        //
    }
    pub fn deserialize() {
        //
    }
}

/// Virtual Components for custom user-defined components
/// Only supports the functional syntax
pub struct VComponent<'src> {
    pub ass_scope: Cell<Option<ScopeId>>,

    pub(crate) caller: Rc<dyn Fn(&Scope) -> DomTree>,

    pub(crate) children: &'src [VNode<'src>],

    pub(crate) comparator: Option<&'src dyn Fn(&VComponent) -> bool>,

    pub(crate) drop_props: RefCell<Option<BumpBox<'src, dyn FnMut()>>>,

    pub is_static: bool,

    pub can_memoize: bool,

    // a pointer into the bump arena (given by the 'src lifetime)
    pub(crate) raw_props: *const (),

    // a pointer to the raw fn typ
    pub(crate) user_fc: *const (),
}

pub struct VSuspended {
    pub node: Rc<Cell<Option<ElementId>>>,
}

/// This struct provides an ergonomic API to quickly build VNodes.
///
/// NodeFactory is used to build VNodes in the component's memory space.
/// This struct adds metadata to the final VNode about listeners, attributes, and children
#[derive(Copy, Clone)]
pub struct NodeFactory<'a> {
    pub(crate) bump: &'a Bump,
}

impl<'a> NodeFactory<'a> {
    pub fn new(bump: &'a Bump) -> NodeFactory<'a> {
        NodeFactory { bump }
    }

    #[inline]
    pub fn bump(&self) -> &'a bumpalo::Bump {
        &self.bump
    }

    pub fn render_directly<F>(&self, lazy_nodes: LazyNodes<'a, F>) -> DomTree<'a>
    where
        F: FnOnce(NodeFactory<'a>) -> VNode<'a>,
    {
        Some(lazy_nodes.into_vnode(NodeFactory { bump: self.bump }))
    }

    pub fn unstable_place_holder() -> VNode<'static> {
        VNode {
            key: None,
            kind: VNodeKind::Text(VText {
                text: "",
                dom_id: empty_cell(),
                is_static: true,
            }),
        }
    }

    /// Used in a place or two to make it easier to build vnodes from dummy text
    pub fn static_text(&self, text: &'static str) -> VNode<'a> {
        VNode {
            key: None,
            kind: VNodeKind::Text(VText {
                dom_id: empty_cell(),
                text,
                is_static: true,
            }),
        }
    }

    /// Parses a lazy text Arguments and returns a string and a flag indicating if the text is 'static
    ///
    /// Text that's static may be pointer compared, making it cheaper to diff
    pub fn raw_text(&self, args: Arguments) -> (&'a str, bool) {
        match args.as_str() {
            Some(static_str) => (static_str, true),
            None => {
                use bumpalo::core_alloc::fmt::Write;
                let mut s = bumpalo::collections::String::new_in(self.bump());
                s.write_fmt(args).unwrap();
                (s.into_bump_str(), false)
            }
        }
    }

    /// Create some text that's allocated along with the other vnodes
    ///
    pub fn text(&self, args: Arguments) -> VNode<'a> {
        let (text, is_static) = self.raw_text(args);
        VNode {
            key: None,
            kind: VNodeKind::Text(VText {
                text,
                is_static,
                dom_id: empty_cell(),
            }),
        }
    }

    pub fn element<L, A, V>(
        &self,
        el: impl DioxusElement,
        listeners: L,
        attributes: A,
        children: V,
        key: Option<Arguments>,
    ) -> VNode<'a>
    where
        L: 'a + AsRef<[Listener<'a>]>,
        A: 'a + AsRef<[Attribute<'a>]>,
        V: 'a + AsRef<[VNode<'a>]>,
    {
        self.raw_element(
            el.tag_name(),
            el.namespace(),
            listeners,
            attributes,
            children,
            key,
        )
    }

    pub fn raw_element<L, A, V>(
        &self,
        tag: &'static str,
        namespace: Option<&'static str>,
        listeners: L,
        attributes: A,
        children: V,
        key: Option<Arguments>,
    ) -> VNode<'a>
    where
        L: 'a + AsRef<[Listener<'a>]>,
        A: 'a + AsRef<[Attribute<'a>]>,
        V: 'a + AsRef<[VNode<'a>]>,
    {
        let listeners: &'a L = self.bump().alloc(listeners);
        let listeners = listeners.as_ref();

        let attributes: &'a A = self.bump().alloc(attributes);
        let attributes = attributes.as_ref();

        let children: &'a V = self.bump().alloc(children);
        let children = children.as_ref();

        let key = key.map(|f| self.raw_text(f).0);

        VNode {
            key,
            kind: VNodeKind::Element(self.bump().alloc(VElement {
                tag_name: tag,
                namespace,
                listeners,
                attributes,
                children,
                dom_id: empty_cell(),

                // todo: wire up more constization
                static_listeners: false,
                static_attrs: false,
                static_children: false,
            })),
        }
    }

    pub fn suspended() -> VNode<'static> {
        VNode {
            key: None,
            kind: VNodeKind::Suspended(VSuspended {
                node: Rc::new(empty_cell()),
            }),
        }
    }

    pub fn attr(
        &self,
        name: &'static str,
        val: Arguments,
        namespace: Option<&'static str>,
        is_volatile: bool,
    ) -> Attribute<'a> {
        let (value, is_static) = self.raw_text(val);
        Attribute {
            name,
            value,
            is_static,
            namespace,
            is_volatile,
        }
    }

    pub fn attr_with_alloc_val(
        &self,
        name: &'static str,
        val: &'a str,
        namespace: Option<&'static str>,
        is_volatile: bool,
    ) -> Attribute<'a> {
        Attribute {
            name,
            value: val,
            is_static: false,
            namespace,
            is_volatile,
        }
    }

    pub fn component<P, V>(
        &self,
        component: FC<P>,
        props: P,
        key: Option<Arguments>,
        children: V,
    ) -> VNode<'a>
    where
        P: Properties + 'a,
        V: 'a + AsRef<[VNode<'a>]>,
    {
        let bump = self.bump();

        // We don't want the fat part of the fat pointer
        // This function does static dispatch so we don't need any VTable stuff
        let children: &'a V = bump.alloc(children);
        let children = children.as_ref();

        let props = bump.alloc(props);

        let raw_props = props as *mut P as *mut ();
        let user_fc = component as *const ();

        let comparator: Option<&dyn Fn(&VComponent) -> bool> = Some(bump.alloc_with(|| {
            move |other: &VComponent| {
                if user_fc == other.user_fc {
                    // Safety
                    // - We guarantee that FC<P> is the same by function pointer
                    // - Because FC<P> is the same, then P must be the same (even with generics)
                    // - Non-static P are autoderived to memoize as false
                    // - This comparator is only called on a corresponding set of bumpframes
                    let props_memoized = unsafe {
                        let real_other: &P = &*(other.raw_props as *const _ as *const P);
                        props.memoize(&real_other)
                    };

                    // It's only okay to memoize if there are no children and the props can be memoized
                    // Implementing memoize is unsafe and done automatically with the props trait
                    match (props_memoized, children.len() == 0) {
                        (true, true) => true,
                        _ => false,
                    }
                } else {
                    false
                }
            }
        }));

        // create a closure to drop the props
        let mut has_dropped = false;
        let drop_props: &mut dyn FnMut() = bump.alloc_with(|| {
            move || unsafe {
                if !has_dropped {
                    let real_other = raw_props as *mut _ as *mut P;
                    let b = BumpBox::from_raw(real_other);
                    std::mem::drop(b);

                    has_dropped = true;
                }
            }
        });
        let drop_props = unsafe { BumpBox::from_raw(drop_props) };

        let is_static = children.len() == 0 && P::IS_STATIC && key.is_none();

        let key = key.map(|f| self.raw_text(f).0);

        VNode {
            key,
            kind: VNodeKind::Component(bump.alloc_with(|| VComponent {
                user_fc,
                comparator,
                raw_props,
                children,
                caller: NodeFactory::create_component_caller(component, raw_props),
                is_static,
                drop_props: RefCell::new(Some(drop_props)),
                can_memoize: P::IS_STATIC,
                ass_scope: Cell::new(None),
            })),
        }
    }

    pub fn create_component_caller<'g, P: 'g>(
        component: FC<P>,
        raw_props: *const (),
    ) -> Rc<dyn for<'r> Fn(&'r Scope) -> DomTree<'r>> {
        type Captured<'a> = Rc<dyn for<'r> Fn(&'r Scope) -> DomTree<'r> + 'a>;
        let caller: Captured = Rc::new(move |scp: &Scope| -> DomTree {
            // cast back into the right lifetime
            let safe_props: &'_ P = unsafe { &*(raw_props as *const P) };
            let cx: Context<P> = Context {
                props: safe_props,
                scope: scp,
            };

            let res = component(cx);

            let g2 = unsafe { std::mem::transmute(res) };

            g2
        });
        unsafe { std::mem::transmute::<_, Captured<'static>>(caller) }
    }

    pub fn fragment_from_iter(self, node_iter: impl IntoVNodeList<'a>) -> VNode<'a> {
        let children = node_iter.into_vnode_list(self);

        VNode {
            key: None,
            kind: VNodeKind::Fragment(VFragment {
                children,
                is_static: false,
            }),
        }
    }
}

/// Trait implementations for use in the rsx! and html! macros.
///
/// ## Details
///
/// This section provides convenience methods and trait implementations for converting common structs into a format accepted
/// by the macros.
///
/// All dynamic content in the macros must flow in through `fragment_from_iter`. Everything else must be statically layed out.
/// We pipe basically everything through `fragment_from_iter`, so we expect a very specific type:
/// ```
/// impl IntoIterator<Item = impl IntoVNode<'a>>
/// ```
///
/// As such, all node creation must go through the factory, which is only availble in the component context.
/// These strict requirements make it possible to manage lifetimes and state.
pub trait IntoVNode<'a> {
    fn into_vnode(self, cx: NodeFactory<'a>) -> VNode<'a>;
}

pub trait IntoVNodeList<'a> {
    fn into_vnode_list(self, cx: NodeFactory<'a>) -> &'a [VNode<'a>];
}

impl<'a, T, V> IntoVNodeList<'a> for T
where
    T: IntoIterator<Item = V>,
    V: IntoVNode<'a>,
{
    fn into_vnode_list(self, cx: NodeFactory<'a>) -> &'a [VNode<'a>] {
        let mut nodes = bumpalo::collections::Vec::new_in(cx.bump());

        for node in self.into_iter() {
            nodes.push(node.into_vnode(cx));
        }

        if cfg!(debug_assertions) {
            if nodes.len() > 1 {
                if nodes.last().unwrap().key().is_none() {
                    log::error!(
                        r#"
        Warning: Each child in an array or iterator should have a unique "key" prop.
        Not providing a key will lead to poor performance with lists.
        See docs.rs/dioxus for more information.
        ---
        To help you identify where this error is coming from, we've generated a backtrace.
                                "#,
                    );
                }
            }
        }

        if nodes.len() == 0 {
            nodes.push(VNode {
                kind: VNodeKind::Anchor(VAnchor {
                    dom_id: empty_cell(),
                }),
                key: None,
            });
        }

        nodes.into_bump_slice()
    }
}

pub struct ScopeChildren<'a>(pub &'a [VNode<'a>]);
impl Copy for ScopeChildren<'_> {}
impl<'a> Clone for ScopeChildren<'a> {
    fn clone(&self) -> Self {
        ScopeChildren(self.0)
    }
}
impl ScopeChildren<'_> {
    pub unsafe fn extend_lifetime(self) -> ScopeChildren<'static> {
        std::mem::transmute(self)
    }
    pub unsafe fn unextend_lfetime<'a>(self) -> ScopeChildren<'a> {
        std::mem::transmute(self)
    }
}
impl<'a> IntoVNodeList<'a> for ScopeChildren<'a> {
    fn into_vnode_list(self, _: NodeFactory<'a>) -> &'a [VNode<'a>] {
        self.0
    }
}

// For the case where a rendered VNode is passed into the rsx! macro through curly braces
impl<'a> IntoIterator for VNode<'a> {
    type Item = VNode<'a>;
    type IntoIter = std::iter::Once<Self::Item>;
    fn into_iter(self) -> Self::IntoIter {
        std::iter::once(self)
    }
}

// For the case where a rendered VNode is passed into the rsx! macro through curly braces
impl<'a> IntoVNode<'a> for VNode<'a> {
    fn into_vnode(self, _: NodeFactory<'a>) -> VNode<'a> {
        self
    }
}

/// A concrete type provider for closures that build VNode structures.
///
/// This struct wraps lazy structs that build VNode trees Normally, we cannot perform a blanket implementation over
/// closures, but if we wrap the closure in a concrete type, we can maintain separate implementations of IntoVNode.
///
///
/// ```rust
/// LazyNodes::new(|f| f.element("div", [], [], [] None))
/// ```
pub struct LazyNodes<'a, G>
where
    G: FnOnce(NodeFactory<'a>) -> VNode<'a>,
{
    inner: G,
    _p: PhantomData<&'a ()>,
}

impl<'a, G> LazyNodes<'a, G>
where
    G: FnOnce(NodeFactory<'a>) -> VNode<'a>,
{
    pub fn new(f: G) -> Self {
        Self {
            inner: f,
            _p: PhantomData {},
        }
    }
}

// Our blanket impl
impl<'a, G> IntoVNode<'a> for LazyNodes<'a, G>
where
    G: FnOnce(NodeFactory<'a>) -> VNode<'a>,
{
    fn into_vnode(self, cx: NodeFactory<'a>) -> VNode<'a> {
        (self.inner)(cx)
    }
}

// Our blanket impl
impl<'a, G> IntoIterator for LazyNodes<'a, G>
where
    G: FnOnce(NodeFactory<'a>) -> VNode<'a>,
{
    type Item = Self;
    type IntoIter = std::iter::Once<Self::Item>;
    fn into_iter(self) -> Self::IntoIter {
        std::iter::once(self)
    }
}

// Conveniently, we also support "null" (nothing) passed in
impl IntoVNode<'_> for () {
    fn into_vnode<'a>(self, cx: NodeFactory<'a>) -> VNode<'a> {
        cx.fragment_from_iter(None as Option<VNode>)
    }
}

// Conveniently, we also support "None"
impl IntoVNode<'_> for Option<()> {
    fn into_vnode<'a>(self, cx: NodeFactory<'a>) -> VNode<'a> {
        cx.fragment_from_iter(None as Option<VNode>)
    }
}
impl<'a> IntoVNode<'a> for Option<VNode<'a>> {
    fn into_vnode(self, cx: NodeFactory<'a>) -> VNode<'a> {
        match self {
            Some(n) => n,
            None => cx.fragment_from_iter(None as Option<VNode>),
        }
    }
}

impl IntoVNode<'_> for &'static str {
    fn into_vnode<'a>(self, cx: NodeFactory<'a>) -> VNode<'a> {
        cx.static_text(self)
    }
}
impl IntoVNode<'_> for Arguments<'_> {
    fn into_vnode<'a>(self, cx: NodeFactory<'a>) -> VNode<'a> {
        cx.text(self)
    }
}

impl Debug for NodeFactory<'_> {
    fn fmt(&self, _: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        Ok(())
    }
}

impl Debug for VNode<'_> {
    fn fmt(&self, s: &mut Formatter<'_>) -> std::result::Result<(), std::fmt::Error> {
        match &self.kind {
            VNodeKind::Element(el) => write!(s, "VElement {{ name: {} }}", el.tag_name),
            VNodeKind::Text(t) => write!(s, "VText {{ text: {} }}", t.text),
            VNodeKind::Anchor(a) => write!(s, "VAnchor"),

            VNodeKind::Fragment(_) => write!(s, "fragment"),
            VNodeKind::Suspended { .. } => write!(s, "suspended"),
            VNodeKind::Component(_) => write!(s, "component"),
        }
    }
}