use crate::mutations::Mutation;
use crate::mutations::Mutation::*;
use crate::nodes::VNode;
use crate::nodes::{DynamicNode, DynamicNodeKind, TemplateNode};
use crate::virtualdom::VirtualDom;
use crate::TemplateAttribute;

impl VirtualDom {
    /// Create this template and write its mutations
    pub fn create<'a>(
        &mut self,
        mutations: &mut Vec<Mutation<'a>>,
        template: &'a VNode<'a>,
    ) -> usize {
        // The best renderers will have templates prehydrated
        // Just in case, let's create the template using instructions anyways
        if !self.templates.contains_key(&template.template.id) {
            for node in template.template.roots {
                self.create_static_node(mutations, template, node);
            }

            mutations.push(SaveTemplate {
                name: template.template.id,
                m: template.template.roots.len(),
            });

            self.templates
                .insert(template.template.id, template.template.clone());
        }

        // Walk the roots backwards, creating nodes and assigning IDs
        // todo: adjust dynamic nodes to be in the order of roots and then leaves (ie BFS)
        let mut dynamic_attrs = template.dynamic_attrs.iter().peekable();
        let mut dynamic_nodes = template.dynamic_nodes.iter().peekable();

        let mut on_stack = 0;
        for (root_idx, root) in template.template.roots.iter().enumerate() {
            on_stack += match root {
                TemplateNode::Element { .. } | TemplateNode::Text(_) => {
                    mutations.push(LoadTemplate {
                        name: template.template.id,
                        index: root_idx,
                    });

                    1
                }

                TemplateNode::Dynamic(id) => {
                    self.create_dynamic_node(mutations, template, &template.dynamic_nodes[*id])
                }

                TemplateNode::DynamicText { .. } => 1,
            };

            // we're on top of a node that has a dynamic attribute for a descendant
            // Set that attribute now before the stack gets in a weird state
            while let Some(loc) = dynamic_attrs.next_if(|a| a.path[0] == root_idx as u8) {
                // Attach all the elementIDs to the nodes with dynamic content
                let id = self.next_element(template);

                mutations.push(AssignId {
                    path: &loc.path[1..],
                    id,
                });

                loc.mounted_element.set(id);

                for attr in loc.attrs.iter() {
                    mutations.push(SetAttribute {
                        name: attr.name,
                        value: attr.value,
                        id,
                    });
                }
            }

            // We're on top of a node that has a dynamic child for a descendant
            while let Some(node) = dynamic_nodes.next_if(|f| f.path[0] == root_idx as u8) {
                let m = self.create_dynamic_node(mutations, template, node);
                mutations.push(ReplacePlaceholder {
                    m,
                    path: &node.path[1..],
                });
            }
        }

        on_stack
    }

    fn create_static_node<'a>(
        &mut self,
        mutations: &mut Vec<Mutation<'a>>,
        template: &'a VNode<'a>,
        node: &'a TemplateNode<'static>,
    ) {
        match *node {
            TemplateNode::Dynamic(_) => mutations.push(CreatePlaceholder),
            TemplateNode::Text(value) => mutations.push(CreateText { value }),
            TemplateNode::DynamicText { .. } => mutations.push(CreateText {
                value: "placeholder",
            }),
            TemplateNode::Element {
                attrs,
                children,
                namespace,
                tag,
            } => {
                let id = self.next_element(template);

                mutations.push(CreateElement {
                    name: tag,
                    namespace,
                    id,
                });

                mutations.extend(attrs.into_iter().filter_map(|attr| match attr {
                    TemplateAttribute::Static { name, value, .. } => {
                        Some(SetAttribute { name, value, id })
                    }
                    _ => None,
                }));

                children
                    .into_iter()
                    .for_each(|child| self.create_static_node(mutations, template, child));

                mutations.push(AppendChildren { m: children.len() })
            }
        }
    }

    fn create_dynamic_node<'a>(
        &mut self,
        mutations: &mut Vec<Mutation<'a>>,
        template: &'a VNode<'a>,
        node: &'a DynamicNode<'a>,
    ) -> usize {
        match &node.kind {
            DynamicNodeKind::Text { id, value } => {
                let new_id = self.next_element(template);
                id.set(new_id);
                mutations.push(HydrateText {
                    id: new_id,
                    path: &node.path[1..],
                    value,
                });

                1
            }

            DynamicNodeKind::Component { props, .. } => {
                let id = self.new_scope(*props);

                let template = self.run_scope(id);

                // shut up about lifetimes please, I know what I'm doing
                let template: &VNode = unsafe { std::mem::transmute(template) };

                self.scope_stack.push(id);
                let created = self.create(mutations, template);
                self.scope_stack.pop();

                created
            }

            DynamicNodeKind::Fragment { children } => {
                //
                children
                    .iter()
                    .fold(0, |acc, child| acc + self.create(mutations, child))
            }
        }
    }
}