use {
    crate::{
        core::{
            type_term::{TypeDict, TypeTerm, TypeID},
            AnyOuterViewPort, OuterViewPort, View,
        },
        Nested
    },
    std::{
        collections::HashMap,
        sync::{Arc, RwLock},
    },
};

//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>

#[derive(Clone)]
pub struct ReprTree {
    type_tag: TypeTerm,
    port: Option<AnyOuterViewPort>,
    branches: HashMap<TypeTerm, Arc<RwLock<ReprTree>>>,
}

impl ReprTree {
    pub fn new(type_tag: TypeTerm) -> Self {
        ReprTree {
            type_tag,
            port: None,
            branches: HashMap::new(),
        }
    }

    pub fn new_leaf(type_tag: TypeTerm, port: AnyOuterViewPort) -> Arc<RwLock<Self>> {
        let mut tree = ReprTree::new(type_tag);
        tree.insert_leaf(vec![].into_iter(), port);
        Arc::new(RwLock::new(tree))
    }

    pub fn insert_branch(&mut self, repr: Arc<RwLock<ReprTree>>) {
        self.branches.insert(repr.clone().read().unwrap().type_tag.clone(), repr.clone());
    }

    pub fn insert_leaf(
        &mut self,
        mut type_ladder: impl Iterator<Item = TypeTerm>,
        port: AnyOuterViewPort,
    ) {
        if let Some(type_term) = type_ladder.next() {
            if let Some(next_repr) = self.branches.get(&type_term) {
                next_repr.write().unwrap().insert_leaf(type_ladder, port);
            } else {
                let mut next_repr = ReprTree::new(type_term.clone());
                next_repr.insert_leaf(type_ladder, port);
                self.insert_branch(Arc::new(RwLock::new(next_repr)));
            }
        } else {
            self.port = Some(port);
        }
    }

    //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>

    pub fn get_port<V: View + ?Sized + 'static>(&self) -> Option<OuterViewPort<V>>
    where
        V::Msg: Clone,
    {
        Some(
            self.port
                .clone()?
                .downcast::<V>()
                .ok()
                .unwrap()
        )
    }

    pub fn get_view<V: View + ?Sized + 'static>(&self) -> Option<Arc<V>>
    where
        V::Msg: Clone,
    {
            self.get_port::<V>()?
                .get_view()
    }

    // descend
    pub fn downcast(&self, dst_type: &TypeTerm) -> Option<Arc<RwLock<ReprTree>>> {
        self.branches.get(dst_type).cloned()
    }

    pub fn downcast_ladder(&self, mut repr_ladder: impl Iterator<Item = TypeTerm>) -> Option<Arc<RwLock<ReprTree>>> {
        let first = repr_ladder.next()?;
        repr_ladder.fold(
            self.downcast(&first),
            |s, t| s?.read().unwrap().downcast(&t))
    }

    // ascend
    pub fn upcast(rt: &Arc<RwLock<Self>>, type_term: TypeTerm) -> Arc<RwLock<ReprTree>> {
        let mut n = Self::new(type_term);
        n.insert_branch(rt.clone());
        Arc::new(RwLock::new(n))
    }

/*
    pub fn add_iso_repr(
        &self,
        type_ladder: impl Iterator<Item = TypeTerm>,
        morphism_constructors: &HashMap<MorphismType, Box<dyn Fn(Object) -> Object>>,
    ) {
        let mut cur_repr = self.repr.clone();

        for dst_type in type_ladder {
            if let Some(next_repr) = self.repr.read().unwrap().branches.get(&dst_type) {
                // go deeper
                cur_repr = next_repr.clone();
            } else {
                // search for morphism constructor and insert new repr
                let mut obj = None;

                for src_type in cur_repr.read().unwrap().branches.keys() {
                    if let Some(ctor) = morphism_constructors.get(&MorphismType {
                        mode: MorphismMode::Iso,
                        src_type: src_type.clone(),
                        dst_type: dst_type.clone(),
                    }) {
                        let new_obj = ctor(Object {
                            type_tag: src_type.clone(),
                            repr: cur_repr
                                .read()
                                .unwrap()
                                .branches
                                .get(&src_type)
                                .unwrap()
                                .clone(),
                        });

                        assert!(new_obj.type_tag == dst_type);

                        obj = Some(new_obj);
                        break;
                    }
                }

                if let Some(obj) = obj {
                    cur_repr
                        .write()
                        .unwrap()
                        .insert_branch(obj.type_tag, obj.repr);
                } else {
                    panic!("could not find matching isomorphism!");
                }
            }
        }
    }

    pub fn add_mono_repr<'a>(
        &self,
        type_ladder: impl Iterator<Item = TypeTerm>,
        morphism_constructors: &HashMap<MorphismType, Box<dyn Fn(Object) -> Object>>,
    ) {
        let mut cur_type = self.type_tag.clone();
        let mut cur_repr = self.repr.clone();   

        for dst_type in type_ladder {
            if let Some(next_repr) = self.repr.read().unwrap().branches.get(&dst_type) {
                // go deeper
                cur_type = dst_type;
                cur_repr = next_repr.clone();
            } else {
                if let Some(constructor) = morphism_constructors.get(&MorphismType {
                    mode: MorphismMode::Mono,
                    src_type: cur_type.clone(),
                    dst_type: dst_type.clone(),
                }) {
                    let new_obj = constructor(Object {
                        type_tag: cur_type.clone(),
                        repr: cur_repr
                            .read()
                            .unwrap()
                            .branches
                            .get(&cur_type)
                            .unwrap()
                            .clone(),
                    });

                    assert!(new_obj.type_tag == dst_type);
                    cur_repr
                        .write()
                        .unwrap()
                        .insert_branch(new_obj.type_tag.clone(), new_obj.repr.clone());

                    cur_type = new_obj.type_tag;
                    cur_repr = new_obj.repr;
                }
            }
        }
    }

    // replace with higher-level type in which self is a repr branch
    pub fn epi_cast<'a>(
        &self,
        _type_ladder: impl Iterator<Item = TypeTerm>,
        _morphism_constructors: &HashMap<MorphismType, Box<dyn Fn(Object) -> Object>>,
    ) {
        // todo
        
}
    */
}

//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>

pub struct TypeLadder(Vec<TypeTerm>);

#[derive(Clone, Copy, Hash, PartialEq, Eq)]
pub enum MorphismMode {
    /// Isomorphism
    /// e.g. `( PositionalInteger 10 BigEndian ) <~> ( PositionalInteger 16 LittleEndian )`
    Iso,

    /// Monomorphism, i.e. injective functions,
    /// upcast-view, downcast-control, semantic gain
    /// e.g. `( Sequence ( Digit 16 ) ) ~> ( PositionalInteger 16 LittleEndian )`
    Mono,

    /// Epimorphsim, i.e. surjective functions,
    /// upcast-control, downcast-view, possible loss of entropy
    /// e.g. `( Ascii ) ~> ( Digit 16 )`
    Epi,

    /// Any other function
    Any,
}

#[derive(Clone, Hash, PartialEq, Eq)]
pub struct MorphismType {
    pub mode: MorphismMode,
    pub src_type: TypeTerm,
    pub dst_type: TypeTerm,
}

//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>

pub struct Context {
    /// assigns a name to every type
    type_dict: Arc<RwLock<TypeDict>>,

    /// objects
    objects: HashMap<String, Arc<RwLock<ReprTree>>>,

    /// editors
    editor_ctors: HashMap<TypeID, Arc<dyn Fn(Arc<RwLock<Self>>, TypeTerm, usize) -> Option<Arc<RwLock<dyn Nested + Send + Sync>>> + Send + Sync>>,

    /// morphisms
    default_constructors: HashMap<TypeTerm, Box<dyn Fn() -> Arc<RwLock<ReprTree>> + Send + Sync>>,
    morphism_constructors: HashMap<MorphismType, Box<dyn Fn(Arc<RwLock<ReprTree>>) -> Arc<RwLock<ReprTree>> + Send + Sync>>,

    /// recursion
    parent: Option<Arc<RwLock<Context>>>,
}

impl Context {
    pub fn with_parent(parent: Option<Arc<RwLock<Context>>>) -> Self {
        Context {
            type_dict: match parent.as_ref() {
                Some(p) => p.read().unwrap().type_dict.clone(),
                None => Arc::new(RwLock::new(TypeDict::new()))
            },
            editor_ctors: HashMap::new(),
            default_constructors: HashMap::new(),
            morphism_constructors: HashMap::new(),
            objects: HashMap::new(),
            parent,
        }
    }

    pub fn new() -> Self {
        Context::with_parent(None)
    }

    pub fn add_typename(&mut self, tn: String) {
        self.type_dict.write().unwrap().add_typename(tn);
    }

    pub fn type_term_from_str(&self, tn: &str) -> Option<TypeTerm> {
        self.type_dict.read().unwrap().type_term_from_str(&tn)
    }

    pub fn type_term_to_str(&self, t: &TypeTerm) -> String {
        self.type_dict.read().unwrap().type_term_to_str(&t)
    }

    pub fn add_editor_ctor(&mut self, tn: &str, mk_editor: Arc<dyn Fn(Arc<RwLock<Self>>, TypeTerm, usize) -> Option<Arc<RwLock<dyn Nested + Send + Sync>>> + Send + Sync>) {
        let mut dict = self.type_dict.write().unwrap();
        let tyid = dict.get_typeid(&tn.into()).unwrap_or( dict.add_typename(tn.into()) );
        self.editor_ctors.insert(tyid, mk_editor);
    }

    pub fn get_editor_ctor(&self, ty: &TypeTerm) -> Option<Arc<dyn Fn(Arc<RwLock<Self>>, TypeTerm, usize) -> Option<Arc<RwLock<dyn Nested + Send + Sync>>> + Send + Sync>> {
        if let TypeTerm::Type{ id, args: _ } = ty.clone() {
            if let Some(m) = self.editor_ctors.get(&id).cloned() {
                Some(m)
            } else {
                self.parent.as_ref()?
                    .read().unwrap()
                    .get_editor_ctor(&ty)
            }
        } else {
            None
        }
    }

    pub fn make_editor(ctx: Arc<RwLock<Self>>, type_term: TypeTerm, depth: usize) -> Option<Arc<RwLock<dyn Nested + Send + Sync>>> {
        let mk_editor = ctx.read().unwrap().get_editor_ctor(&type_term)?;
        mk_editor(ctx, type_term, depth)
    }

    pub fn add_morphism(
        &mut self,
        morph_type: MorphismType,
        morph_fn: Box<dyn Fn(Arc<RwLock<ReprTree>>) -> Arc<RwLock<ReprTree>> + Send + Sync>,
    ) {
        self.morphism_constructors.insert(morph_type, morph_fn);
    }

    /// adds an object without any representations
    pub fn add_obj(&mut self, name: String, typename: &str) {
        let type_tag = self.type_dict.read().unwrap().type_term_from_str(typename).unwrap();

        self.objects.insert(
            name,
            if let Some(ctor) = self.default_constructors.get(&type_tag) {
                ctor()
            } else {
                Arc::new(RwLock::new(ReprTree::new(type_tag)))
            },
        );
    }

    pub fn get_obj(&self, name: &String) -> Option<Arc<RwLock<ReprTree>>> {
        if let Some(obj) = self.objects.get(name) {
            Some(obj.clone())
        } else if let Some(parent) = self.parent.as_ref() {
            parent.read().unwrap().get_obj(name)
        } else {
            None
        }
    }

/*
    pub fn get_obj_port<'a, V: View + ?Sized + 'static>(
        &self,
        name: &str,
        type_ladder: impl Iterator<Item = &'a str>,
    ) -> Option<OuterViewPort<V>>
    where
        V::Msg: Clone,
    {
        self.get_obj(&name.into())?
            .downcast_ladder(type_ladder.map(|tn| self.type_dict.type_term_from_str(tn).unwrap()))?
            .get_port()
    }

    pub fn insert_repr<'a>(
        &mut self,
        name: &str,
        type_ladder: impl Iterator<Item = &'a str>,
        port: AnyOuterViewPort,
    ) {
        self.get_obj(&name.to_string())
            .unwrap()
            .repr
            .write()
            .unwrap()
            .insert_leaf(
                type_ladder.map(|tn| self.type_dict.type_term_from_str(tn).unwrap()),
                port,
            );
    }

    pub fn epi_cast(&mut self, name: &str, typename: &str) {
        let dst_type = self.type_dict.type_term_from_str(typename).unwrap();
        let old_obj = self.objects.get(&name.to_string()).unwrap().clone();
        let new_obj = if let Some(ctor) = self.morphism_constructors.get(&MorphismType {
            mode: MorphismMode::Epi,
            src_type: old_obj.type_tag.clone(),
            dst_type: dst_type.clone(),
        }) {
            ctor(old_obj.clone())
        } else {
            Arc::new(RwLock::new(ReprTree::new(dst_type)))
        };

        new_obj
            .repr
            .write()
            .unwrap()
            .insert_branch(old_obj.type_tag, old_obj.repr);

        self.objects.insert(name.to_string(), new_obj);
    }

    pub fn mono_view<'a, V: View + ?Sized + 'static>(
        &mut self,
        name: &str,
        type_ladder: impl Iterator<Item = &'a str>,
    ) -> Option<OuterViewPort<V>>
    where
        V::Msg: Clone,
    {
        if let Some(p) = self.get_obj_port(name, type_ladder) {
            Some(p)
        } else {
            // todo : add repr with morphism constructor (if one exists)
            /*
            if let Some(ctor) = self.morphism_constructors.get(
                &MorphismType {
                    mode: MorphismMode::Mono,
                    src_type: old_obj.type_tag.clone(),
                    dst_type:
                }
            )
            */
            None
        }
}
    */
}

//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>