use crate::dom;
use crate::dom::dom_node;
use crate::dom::dom_node::DomInner;
use crate::dom::DomAttr;
use crate::dom::DomAttrValue;
use crate::dom::DomNode;
use crate::dom::{Application, Program};
use crate::vdom::ComponentEventCallback;
use crate::vdom::EventCallback;
use crate::vdom::TreePath;
use crate::vdom::{Attribute, AttributeValue, Patch, PatchType};
use indexmap::IndexMap;
use wasm_bindgen::closure::Closure;
use wasm_bindgen::JsValue;

/// a Patch where the virtual nodes are all created in the document.
/// This is necessary since the created Node  doesn't contain references
/// as opposed to Patch which contains reference to the vdom, which makes it hard
/// to be included in a struct
#[derive(Debug)]
pub struct DomPatch {
    /// The path to traverse to get to the target_element
    pub patch_path: TreePath,
    /// the target node
    pub target_element: DomNode,
    /// the parent element of the target node
    pub target_parent: DomNode,
    /// the patch variant
    pub patch_variant: PatchVariant,
}

/// patch variant
#[derive(Debug)]
pub enum PatchVariant {
    /// Insert nodes before the target node
    InsertBeforeNode {
        /// nodes to be inserted before the target node
        nodes: Vec<DomNode>,
    },
    /// Insert nodes after the target node
    InsertAfterNode {
        /// the nodes to be inserted after the target node
        nodes: Vec<DomNode>,
    },
    /// Append nodes into the target node
    AppendChildren {
        /// the children nodes to be appended into the target node
        children: Vec<DomNode>,
    },
    /// Add attributes to the target node
    AddAttributes {
        /// the attributes to be added to the target node
        attrs: Vec<DomAttr>,
    },
    /// Remove attributes from the target node
    RemoveAttributes {
        /// the attributes names to be removed
        attrs: Vec<DomAttr>,
    },
    /// Replace the target node with the replacement node
    ReplaceNode {
        /// the replacement node
        replacement: Vec<DomNode>,
    },
    /// Remove the target node
    RemoveNode,
    /// Clear the children of the target node
    ClearChildren,
    /// Move the target node before the node specified in the path location
    MoveBeforeNode {
        /// before the node at this location
        for_moving: Vec<DomNode>,
    },
    /// Move the target node after the node specified in the path location
    MoveAfterNode {
        /// after the node at this location
        for_moving: Vec<DomNode>,
    },
}

impl DomNode {
    pub(crate) fn find_node(&self, path: &mut TreePath) -> Option<DomNode> {
        match &self.inner {
            DomInner::StatefulComponent { .. } => {
                log::info!(
                    "This is a stateful component, should return the element
                inside relative to the child container at this path: {:?}",
                    path
                );
                // just return self and handle its own patches
                Some(self.clone())
            }
            _ => {
                if path.is_empty() {
                    Some(self.clone())
                } else {
                    let idx = path.remove_first();
                    if let Some(children) = self.children() {
                        if let Some(child) = children.get(idx) {
                            child.find_node(path)
                        } else {
                            log::warn!("There is no child at index: {idx}");
                            None
                        }
                    } else {
                        log::warn!("Traversing to a childless node..");
                        None
                    }
                }
            }
        }
    }

    pub(crate) fn find_all_nodes(
        &self,
        nodes_to_find: &[(&TreePath, Option<&&'static str>)],
    ) -> IndexMap<TreePath, (DomNode, DomNode)> {
        let mut nodes_to_patch = IndexMap::with_capacity(nodes_to_find.len());
        for (path, tag) in nodes_to_find {
            let mut traverse_path: TreePath = (*path).clone();
            if let Some(found) = self.find_node(&mut traverse_path) {
                let mut parent_path = path.backtrack();
                let target_parent = self
                    .find_node(&mut parent_path)
                    .expect("must find the parent");
                nodes_to_patch.insert((*path).clone(), (found, target_parent));
            } else {
                log::warn!(
                    "can not find: {:?} {:?} target_node: {:?}",
                    path,
                    tag,
                    &self
                );
                log::info!(
                    "real entire dom: {:#?}",
                    dom_node::render_real_dom_to_string(&self.as_node())
                );
                log::warn!("entire dom: {}", self.render_to_string());
            }
        }
        nodes_to_patch
    }
}

impl<APP> Program<APP>
where
    APP: Application + 'static,
{
    pub(crate) fn convert_attr(&self, attr: &Attribute<APP::MSG>) -> DomAttr {
        DomAttr {
            namespace: attr.namespace,
            name: attr.name,
            value: attr
                .value
                .iter()
                .filter_map(|v| self.convert_attr_value(v))
                .collect(),
        }
    }

    fn convert_attr_value(&self, attr_value: &AttributeValue<APP::MSG>) -> Option<DomAttrValue> {
        match attr_value {
            AttributeValue::Simple(v) => Some(DomAttrValue::Simple(v.clone())),
            AttributeValue::Style(v) => Some(DomAttrValue::Style(v.clone())),
            AttributeValue::EventListener(v) => {
                Some(DomAttrValue::EventListener(self.convert_event_listener(v)))
            }
            AttributeValue::ComponentEventListener(v) => Some(DomAttrValue::EventListener(
                self.convert_component_event_listener(v),
            )),
            AttributeValue::Empty => None,
        }
    }

    fn convert_event_listener(
        &self,
        event_listener: &EventCallback<APP::MSG>,
    ) -> Closure<dyn FnMut(web_sys::Event)> {
        let program = self.downgrade();
        let event_listener = event_listener.clone();
        let closure: Closure<dyn FnMut(web_sys::Event)> =
            Closure::new(move |event: web_sys::Event| {
                let msg = event_listener.emit(dom::Event::from(event));
                let mut program = program.upgrade().expect("must upgrade");
                program.dispatch(msg);
            });
        closure
    }

    fn convert_component_event_listener(
        &self,
        component_callback: &ComponentEventCallback,
    ) -> Closure<dyn FnMut(web_sys::Event)> {
        let component_callback = component_callback.clone();
        let closure: Closure<dyn FnMut(web_sys::Event)> =
            Closure::new(move |event: web_sys::Event| {
                component_callback.emit(dom::Event::from(event));
            });
        closure
    }
    /// get the real DOM target node and make a DomPatch object for each of the Patch
    pub(crate) fn convert_patches(
        &self,
        target_node: &DomNode,
        patches: &[Patch<APP::MSG>],
    ) -> Result<Vec<DomPatch>, JsValue> {
        let nodes_to_find: Vec<(&TreePath, Option<&&'static str>)> = patches
            .iter()
            .map(|patch| (patch.path(), patch.tag()))
            .chain(
                patches
                    .iter()
                    .flat_map(|patch| patch.node_paths())
                    .map(|path| (path, None)),
            )
            .collect();

        let nodes_lookup = target_node.find_all_nodes(&nodes_to_find);

        let dom_patches:Vec<DomPatch> = patches.iter().map(|patch|{
            let patch_path = patch.path();
            let patch_tag = patch.tag();
            if let Some((target_node, target_parent)) = nodes_lookup.get(patch_path) {
                let target_tag = target_node.tag();
                if let (Some(patch_tag), Some(target_tag)) = (patch_tag, target_tag) {
                    if **patch_tag != target_tag{
                        panic!(
                            "expecting a tag: {patch_tag:?}, but found: {target_tag:?}"
                        );
                    }
                }
                self.convert_patch(&nodes_lookup, target_node, target_parent, patch)
            } else {
                unreachable!("Getting here means we didn't find the element of next node that we are supposed to patch, patch_path: {:?}, with tag: {:?}", patch_path, patch_tag);
            }
        }).collect();

        Ok(dom_patches)
    }
    /// convert a virtual DOM Patch into a created DOM node Patch
    pub fn convert_patch(
        &self,
        nodes_lookup: &IndexMap<TreePath, (DomNode, DomNode)>,
        target_element: &DomNode,
        target_parent: &DomNode,
        patch: &Patch<APP::MSG>,
    ) -> DomPatch {
        let target_element = target_element.clone();
        let target_parent = target_parent.clone();
        let Patch {
            patch_path,
            patch_type,
            ..
        } = patch;

        let patch_path = patch_path.clone();

        match patch_type {
            PatchType::InsertBeforeNode { nodes } => {
                let nodes = nodes
                    .iter()
                    .map(|for_insert| self.create_dom_node(for_insert))
                    .collect();
                DomPatch {
                    patch_path,
                    target_element,
                    target_parent,
                    patch_variant: PatchVariant::InsertBeforeNode { nodes },
                }
            }
            PatchType::InsertAfterNode { nodes } => {
                let nodes = nodes
                    .iter()
                    .map(|for_insert| self.create_dom_node(for_insert))
                    .collect();
                DomPatch {
                    patch_path,
                    target_element,
                    target_parent,
                    patch_variant: PatchVariant::InsertAfterNode { nodes },
                }
            }

            PatchType::AddAttributes { attrs } => {
                // we merge the attributes here prior to conversion
                let attrs = Attribute::merge_attributes_of_same_name(attrs.iter().copied());
                DomPatch {
                    patch_path,
                    target_element,
                    target_parent,
                    patch_variant: PatchVariant::AddAttributes {
                        attrs: attrs.iter().map(|a| self.convert_attr(a)).collect(),
                    },
                }
            }
            PatchType::RemoveAttributes { attrs } => DomPatch {
                patch_path,
                target_element,
                target_parent,
                patch_variant: PatchVariant::RemoveAttributes {
                    attrs: attrs.iter().map(|a| self.convert_attr(a)).collect(),
                },
            },

            PatchType::ReplaceNode { replacement } => {
                let replacement = replacement
                    .iter()
                    .map(|node| self.create_dom_node(node))
                    .collect();
                DomPatch {
                    patch_path,
                    target_element,
                    target_parent,
                    patch_variant: PatchVariant::ReplaceNode { replacement },
                }
            }
            PatchType::RemoveNode => DomPatch {
                patch_path,
                target_element,
                target_parent,
                patch_variant: PatchVariant::RemoveNode,
            },
            PatchType::ClearChildren => DomPatch {
                patch_path,
                target_element,
                target_parent,
                patch_variant: PatchVariant::ClearChildren,
            },
            PatchType::MoveBeforeNode { nodes_path } => {
                let for_moving = nodes_path
                    .iter()
                    .map(|path| {
                        let (node, _) = nodes_lookup.get(path).expect("must have found the node");
                        node.clone()
                    })
                    .collect();
                DomPatch {
                    patch_path,
                    target_element,
                    target_parent,
                    patch_variant: PatchVariant::MoveBeforeNode { for_moving },
                }
            }
            PatchType::MoveAfterNode { nodes_path } => {
                let for_moving = nodes_path
                    .iter()
                    .map(|path| {
                        let (node, _) = nodes_lookup.get(path).expect("must have found the node");
                        node.clone()
                    })
                    .collect();
                DomPatch {
                    patch_path,
                    target_element,
                    target_parent,
                    patch_variant: PatchVariant::MoveAfterNode { for_moving },
                }
            }
            PatchType::AppendChildren { children } => {
                let children = children
                    .iter()
                    .map(|for_insert| self.create_dom_node(for_insert))
                    .collect();

                DomPatch {
                    patch_path,
                    target_element,
                    target_parent,
                    patch_variant: PatchVariant::AppendChildren { children },
                }
            }
        }
    }

    /// TODO: this should not have access to root_node, so it can generically
    /// apply patch to any dom node
    pub(crate) fn apply_dom_patches(
        &self,
        dom_patches: impl IntoIterator<Item = DomPatch>,
    ) -> Result<(), JsValue> {
        for dom_patch in dom_patches {
            self.apply_dom_patch(dom_patch)?;
        }
        Ok(())
    }

    /// apply a dom patch to this root node,
    /// return a new root_node if it would replace the original root_node
    /// TODO: this should have no access to root_node, so it can be used in general sense
    pub(crate) fn apply_dom_patch(&self, dom_patch: DomPatch) -> Result<(), JsValue> {
        let DomPatch {
            patch_path,
            target_element,
            target_parent,
            patch_variant,
        } = dom_patch;

        match patch_variant {
            PatchVariant::InsertBeforeNode { nodes } => {
                target_parent.insert_before(&target_element, nodes);
            }

            PatchVariant::InsertAfterNode { nodes } => {
                target_parent.insert_after(&target_element, nodes);
            }
            PatchVariant::AppendChildren { children } => {
                target_element.append_children(children);
            }

            PatchVariant::AddAttributes { attrs } => {
                target_element.set_dom_attrs(attrs).unwrap();
            }
            PatchVariant::RemoveAttributes { attrs } => {
                for attr in attrs.iter() {
                    for att_value in attr.value.iter() {
                        match att_value {
                            DomAttrValue::Simple(_) => {
                                target_element.remove_dom_attr(attr)?;
                            }
                            // it is an event listener
                            DomAttrValue::EventListener(_) => {
                                let DomInner::Element { listeners, .. } = &target_element.inner
                                else {
                                    unreachable!("must be an element");
                                };
                                if let Some(listener) = listeners.borrow_mut().as_mut() {
                                    listener.retain(|event, _| *event != attr.name)
                                }
                            }
                            DomAttrValue::Style(_) => {
                                target_element.remove_dom_attr(attr)?;
                            }
                            DomAttrValue::Empty => (),
                        }
                    }
                }
            }

            // This also removes the associated closures and event listeners to the node being replaced
            // including the associated closures of the descendant of replaced node
            // before it is actully replaced in the DOM
            // TODO: make root node a Vec
            PatchVariant::ReplaceNode { mut replacement } => {
                let first_node = replacement.remove(0);

                if target_element.is_fragment() {
                    assert!(
                        patch_path.is_empty(),
                        "this should only happen to root node"
                    );
                    let mut mount_node = self.mount_node.borrow_mut();
                    let mount_node = mount_node.as_mut().expect("must have a mount node");
                    mount_node.append_children(vec![first_node.clone()]);
                    mount_node.append_children(replacement);
                } else {
                    if patch_path.path.is_empty() {
                        let mut mount_node = self.mount_node.borrow_mut();
                        let mount_node = mount_node.as_mut().expect("must have a mount node");
                        mount_node.replace_child(&target_element, first_node.clone());
                    } else {
                        target_parent.replace_child(&target_element, first_node.clone());
                    }
                    //insert the rest
                    target_parent.insert_after(&first_node, replacement);
                }
                if patch_path.path.is_empty() {
                    *self.root_node.borrow_mut() = Some(first_node);
                }
            }
            PatchVariant::RemoveNode => {
                target_parent.remove_children(&[&target_element]);
            }
            PatchVariant::ClearChildren => {
                target_element.clear_children();
            }
            PatchVariant::MoveBeforeNode { for_moving } => {
                target_parent.remove_children(&for_moving.iter().collect::<Vec<_>>());
                target_parent.insert_before(&target_element, for_moving);
            }

            PatchVariant::MoveAfterNode { for_moving } => {
                target_parent.remove_children(&for_moving.iter().collect::<Vec<_>>());
                target_parent.insert_after(&target_element, for_moving);
            }
        }
        Ok(())
    }
}