use std::borrow::BorrowMut;
use std::{collections::HashMap, collections::HashSet, sync::Arc};

use super::typecheck::type_inferencer::PrimitiveStore;
use super::typecheck::typedef::{SharedUnifier, Type, TypeEnum, Unifier};
use crate::symbol_resolver::SymbolResolver;
use crate::typecheck::typedef::{FunSignature, FuncArg};
use itertools::chain;
use parking_lot::{Mutex, RwLock};
use rustpython_parser::ast::{self, Stmt};

#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Copy)]
pub struct DefinitionId(pub usize);

pub enum TopLevelDef {
    Class {
        // object ID used for TypeEnum
        object_id: DefinitionId,
        // type variables bounded to the class.
        type_vars: Vec<Type>,
        // class fields
        fields: Vec<(String, Type)>,
        // class methods, pointing to the corresponding function definition.
        methods: Vec<(String, Type, DefinitionId)>,
        // ancestor classes, including itself.
        ancestors: Vec<DefinitionId>,
        // symbol resolver of the module defined the class, none if it is built-in type
        resolver: Option<Arc<Mutex<dyn SymbolResolver + Send + Sync>>>,
    },
    Function {
        // prefix for symbol, should be unique globally, and not ending with numbers
        name: String,
        // function signature.
        signature: Type,
        /// Function instance to symbol mapping
        /// Key: string representation of type variable values, sorted by variable ID in ascending
        /// order, including type variables associated with the class.
        /// Value: function symbol name.
        instance_to_symbol: HashMap<String, String>,
        /// Function instances to annotated AST mapping
        /// Key: string representation of type variable values, sorted by variable ID in ascending
        /// order, including type variables associated with the class. Excluding rigid type
        /// variables.
        /// Value: AST annotated with types together with a unification table index. Could contain
        /// rigid type variables that would be substituted when the function is instantiated.
        instance_to_stmt: HashMap<String, (Stmt<Option<Type>>, usize)>,
        // symbol resolver of the module defined the class
        resolver: Option<Arc<Mutex<dyn SymbolResolver + Send + Sync>>>,
    },
    Initializer {
        class_id: DefinitionId,
    },
}

impl TopLevelDef {
    fn get_function_type(&self) -> Result<Type, String> {
        if let Self::Function { signature, .. } = self {
            Ok(*signature)
        } else {
            Err("only expect function def here".into())
        }
    }
}

pub struct TopLevelContext {
    pub definitions: Arc<RwLock<Vec<RwLock<TopLevelDef>>>>,
    pub unifiers: Arc<RwLock<Vec<(SharedUnifier, PrimitiveStore)>>>,
}

pub struct TopLevelComposer {
    // list of top level definitions, same as top level context
    pub definition_list: Arc<RwLock<Vec<RwLock<TopLevelDef>>>>,
    // list of top level ast, the index is same as the field `definition_list` and `ty_list`
    pub ast_list: RwLock<Vec<Option<ast::Stmt<()>>>>,
    // start as a primitive unifier, will add more top_level defs inside
    pub unifier: RwLock<Unifier>,
    // primitive store
    pub primitives: PrimitiveStore,
    // mangled class method name to def_id
    pub class_method_to_def_id: RwLock<HashMap<String, DefinitionId>>,
    // record the def id of the classes whoses fields and methods are to be analyzed
    pub to_be_analyzed_class: RwLock<Vec<DefinitionId>>,
}

impl TopLevelComposer {
    pub fn to_top_level_context(&self) -> TopLevelContext {
        TopLevelContext {
            definitions: self.definition_list.clone(),
            // FIXME: all the big unifier or?
            unifiers: Default::default(),
        }
    }

    fn name_mangling(mut class_name: String, method_name: &str) -> String {
        class_name.push_str(method_name);
        class_name
    }

    pub fn make_primitives() -> (PrimitiveStore, Unifier) {
        let mut unifier = Unifier::new();
        let int32 = unifier.add_ty(TypeEnum::TObj {
            obj_id: DefinitionId(0),
            fields: HashMap::new().into(),
            params: HashMap::new().into(),
        });
        let int64 = unifier.add_ty(TypeEnum::TObj {
            obj_id: DefinitionId(1),
            fields: HashMap::new().into(),
            params: HashMap::new().into(),
        });
        let float = unifier.add_ty(TypeEnum::TObj {
            obj_id: DefinitionId(2),
            fields: HashMap::new().into(),
            params: HashMap::new().into(),
        });
        let bool = unifier.add_ty(TypeEnum::TObj {
            obj_id: DefinitionId(3),
            fields: HashMap::new().into(),
            params: HashMap::new().into(),
        });
        let none = unifier.add_ty(TypeEnum::TObj {
            obj_id: DefinitionId(4),
            fields: HashMap::new().into(),
            params: HashMap::new().into(),
        });
        let primitives = PrimitiveStore { int32, int64, float, bool, none };
        crate::typecheck::magic_methods::set_primitives_magic_methods(&primitives, &mut unifier);
        (primitives, unifier)
    }

    /// return a composer and things to make a "primitive" symbol resolver, so that the symbol
    /// resolver can later figure out primitive type definitions when passed a primitive type name
    pub fn new() -> (Vec<(String, DefinitionId, Type)>, Self) {
        let primitives = Self::make_primitives();

        let top_level_def_list = vec![
            RwLock::new(Self::make_top_level_class_def(0, None)),
            RwLock::new(Self::make_top_level_class_def(1, None)),
            RwLock::new(Self::make_top_level_class_def(2, None)),
            RwLock::new(Self::make_top_level_class_def(3, None)),
            RwLock::new(Self::make_top_level_class_def(4, None)),
        ];

        let ast_list: Vec<Option<ast::Stmt<()>>> = vec![None, None, None, None, None];

        let composer = TopLevelComposer {
            definition_list: RwLock::new(top_level_def_list).into(),
            ast_list: RwLock::new(ast_list),
            primitives: primitives.0,
            unifier: primitives.1.into(),
            class_method_to_def_id: Default::default(),
            to_be_analyzed_class: Default::default(),
        };
        (
            vec![
                ("int32".into(), DefinitionId(0), composer.primitives.int32),
                ("int64".into(), DefinitionId(1), composer.primitives.int64),
                ("float".into(), DefinitionId(2), composer.primitives.float),
                ("bool".into(), DefinitionId(3), composer.primitives.bool),
                ("none".into(), DefinitionId(4), composer.primitives.none),
            ],
            composer,
        )
    }

    /// already include the definition_id of itself inside the ancestors vector
    /// when first regitering, the type_vars, fields, methods, ancestors are invalid
    pub fn make_top_level_class_def(
        index: usize,
        resolver: Option<Arc<Mutex<dyn SymbolResolver + Send + Sync>>>,
    ) -> TopLevelDef {
        TopLevelDef::Class {
            object_id: DefinitionId(index),
            type_vars: Default::default(),
            fields: Default::default(),
            methods: Default::default(),
            ancestors: vec![DefinitionId(index)],
            resolver,
        }
    }

    /// when first registering, the type is a invalid value
    pub fn make_top_level_function_def(
        name: String,
        ty: Type,
        resolver: Option<Arc<Mutex<dyn SymbolResolver + Send + Sync>>>,
    ) -> TopLevelDef {
        TopLevelDef::Function {
            name,
            signature: ty,
            instance_to_symbol: Default::default(),
            instance_to_stmt: Default::default(),
            resolver,
        }
    }

    /// step 0, register, just remeber the names of top level classes/function
    pub fn register_top_level(
        &mut self,
        ast: ast::Stmt<()>,
        resolver: Option<Arc<Mutex<dyn SymbolResolver + Send + Sync>>>,
    ) -> Result<(String, DefinitionId), String> {
        let (
            mut def_list,
            mut ast_list
        ) = (
            self.definition_list.write(),
            self.ast_list.write()
        );
        
        assert_eq!(def_list.len(), ast_list.len());

        match &ast.node {
            ast::StmtKind::ClassDef { name, body, .. } => {
                let class_name = name.to_string();
                let class_def_id = def_list.len();

                // add the class to the definition lists
                def_list
                    .push(Self::make_top_level_class_def(class_def_id, resolver.clone()).into());
                // since later when registering class method, ast will still be used,
                // here push None temporarly, later will move the ast inside
                ast_list.push(None);

                // parse class def body and register class methods into the def list.
                // module's symbol resolver would not know the name of the class methods,
                // thus cannot return their definition_id? so we have to manage it ourselves
                // by using `class_method_to_def_id`
                for b in body {
                    if let ast::StmtKind::FunctionDef { name, .. } = &b.node {
                        let fun_name = Self::name_mangling(class_name.clone(), name);
                        let def_id = def_list.len();

                        // add to the definition list
                        def_list.push(
                            Self::make_top_level_function_def(
                                fun_name.clone(),
                                self.unifier.write().add_ty(TypeEnum::TFunc(FunSignature {
                                    args: Default::default(),
                                    ret: self.primitives.none.into(),
                                    vars: Default::default(),
                                }.into())),
                                resolver.clone(),
                            )
                            .into(),
                        );
                        // the ast of class method is in the class, push None in to the list here
                        ast_list.push(None);

                        // class method, do not let the symbol manager manage it, use our own map
                        self.class_method_to_def_id.write().insert(fun_name, DefinitionId(def_id));
                    }
                }

                // move the ast to the entry of the class in the ast_list
                ast_list[class_def_id] = Some(ast);

                // put the constructor into the def_list
                def_list.push(
                    TopLevelDef::Initializer { class_id: DefinitionId(class_def_id) }
                        .into(),
                );
                ast_list.push(None);

                // class, put its def_id into the to be analyzed set
                let mut to_be_analyzed = self.to_be_analyzed_class.write();
                to_be_analyzed.push(DefinitionId(class_def_id));


                Ok((class_name, DefinitionId(class_def_id)))
            }

            ast::StmtKind::FunctionDef { name, .. } => {
                let fun_name = name.to_string();

                // add to the definition list
                def_list.push(
                    Self::make_top_level_function_def(name.into(), self.primitives.none, resolver)
                        .into(),
                );
                ast_list.push(Some(ast));

                // return
                Ok((fun_name, DefinitionId(def_list.len() - 1)))
            }

            _ => Err("only registrations of top level classes/functions are supprted".into()),
        }
    }

    /// step 1, analyze the type vars associated with top level class
    fn analyze_top_level_class_type_var(&mut self) -> Result<(), String> {
        let mut def_list = self.definition_list.write();
        let ast_list = self.ast_list.read();
        let mut unifier = self.unifier.write();

        for (class_def, class_ast) in def_list
            .iter_mut()
            .zip(ast_list.iter())
            .collect::<Vec<(&mut RwLock<TopLevelDef>, &Option<ast::Stmt<()>>)>>() {
            // only deal with class def here
            let (
                class_bases,
                class_def_type_vars,
                class_resolver
            ) = {
                if let TopLevelDef::Class {
                    type_vars,
                    resolver,
                    ..
                } = class_def.get_mut() {
                    if let Some(ast::Located {node: ast::StmtKind::ClassDef {
                        bases,
                        ..
                    }, .. }) = class_ast {
                        (bases, type_vars, resolver)
                    } else { unreachable!("must be both class") }
                } else { continue } 
            }; 
            
            let mut is_generic = false;
            for b in class_bases {
                match &b.node {
                    // analyze typevars bounded to the class,
                    // only support things like `class A(Generic[T, V])`,
                    // things like `class A(Generic[T, V, ImportedModule.T])` is not supported
                    // i.e. only simple names are allowed in the subscript
                    // should update the TopLevelDef::Class.typevars and the TypeEnum::TObj.params
                    ast::ExprKind::Subscript {value, slice, ..} if {
                        // can only be `Generic[...]` and this can only appear once
                        if let ast::ExprKind::Name { id, .. } = &value.node {
                            if id == "Generic" {
                                if !is_generic {
                                    is_generic = true;
                                    true
                                } else {
                                    return Err("Only single Generic[...] can be in bases".into())
                                }
                            } else { false }
                        } else { false }
                    } => {
                        // if `class A(Generic[T, V, G])`
                        if let ast::ExprKind::Tuple { elts, .. } = &slice.node {
                            // parse the type vars
                            let type_vars = elts
                                .iter()
                                .map(|e| 
                                    class_resolver
                                        .as_ref()
                                        .unwrap()
                                        .lock()
                                        .parse_type_annotation(
                                        &self.to_top_level_context(),
                                        unifier.borrow_mut(),
                                        &self.primitives,
                                        e)
                                )
                                .collect::<Result<Vec<_>, _>>()?;
                            
                            // check if all are unique type vars
                            let mut occured_type_var_id: HashSet<u32> = HashSet::new();
                            let all_unique_type_var = type_vars
                                .iter()
                                .all(|x| {
                                    let ty = unifier.get_ty(*x);
                                    if let TypeEnum::TVar {id, ..} = ty.as_ref() {
                                        occured_type_var_id.insert(*id)
                                    } else { false }
                                });
                            
                            if !all_unique_type_var { return Err("expect unique type variables".into()) }
                            
                            // add to TopLevelDef
                            class_def_type_vars.extend(type_vars);
                        
                        // `class A(Generic[T])`
                        } else {
                            let ty = 
                                class_resolver
                                    .as_ref()
                                    .unwrap()
                                    .lock()
                                    .parse_type_annotation(
                                    &self.to_top_level_context(),
                                    unifier.borrow_mut(),
                                    &self.primitives,
                                    &slice
                                )?;
                            // check if it is type var
                            let is_type_var = matches!(
                                unifier.get_ty(ty).as_ref(),
                                &TypeEnum::TVar { .. }
                            );
                            if !is_type_var {  return Err("expect type variable here".into()) }
                            
                            // add to TopLevelDef
                            class_def_type_vars.push(ty);
                        }
                    }
                    
                    // if others, do nothing in this function
                    _ => continue
                }
            }
            
        };
        Ok(())
    }

    /// step 2, base classes. Need to separate step1 and step2 for this reason:
    /// `class B(Generic[T, V]);
    /// class A(B[int, bool])`
    /// if the type var associated with class `B` has not been handled properly,
    /// the parse of type annotation of `B[int, bool]` will fail
    fn analyze_top_level_class_bases(&mut self) -> Result<(), String> {
        let mut def_list = self.definition_list.write();
        let ast_list = self.ast_list.read();
        let mut unifier = self.unifier.write();

        for (class_def, class_ast) in def_list
            .iter_mut()
            .zip(ast_list.iter())
            .collect::<Vec<(&mut RwLock<TopLevelDef>, &Option<ast::Stmt<()>>)>>() {
            let (
                class_bases,
                class_ancestors,
                class_resolver
            ) = {
                if let TopLevelDef::Class {
                    ancestors,
                    resolver,
                    ..
                } = class_def.get_mut() {
                    if let Some(ast::Located {node: ast::StmtKind::ClassDef {
                        bases,
                        ..
                    }, .. }) = class_ast {
                        (bases, ancestors, resolver)
                    } else { unreachable!("must be both class") }
                } else { continue } 
            }; 
            for b in class_bases {
                // type vars have already been handled, so skip on `Generic[...]`
                if let ast::ExprKind::Subscript {value, ..} = &b.node {
                    if let ast::ExprKind::Name {id, ..} = &value.node {
                        if id == "Generic" { continue }
                    }
                }
                // get the def id of the base class
                let base_ty = class_resolver.as_ref().unwrap().lock().parse_type_annotation(
                    &self.to_top_level_context(),
                    unifier.borrow_mut(),
                    &self.primitives,
                    b
                )?;
                let base_id = 
                    if let TypeEnum::TObj {obj_id, ..} = unifier.get_ty(base_ty).as_ref() {
                        *obj_id
                    } else { return Err("expect concrete class/type to be base class".into()) };
                
                // write to the class ancestors
                class_ancestors.push(base_id);
            }
            
        };
        Ok(())
    }

    /// step 3, class fields and methods
    fn analyze_top_level_class_fields_methods(&mut self) -> Result<(), String> {
        let mut def_list = self.definition_list.write();
        let ast_list = self.ast_list.read();
        let mut unifier = self.unifier.write();
        let class_method_to_def_id = self.class_method_to_def_id.read();
        let mut to_be_analyzed_class = self.to_be_analyzed_class.write();

        while !to_be_analyzed_class.is_empty() {
            let class_ind = to_be_analyzed_class.remove(0).0;
            let (class_name, class_body) = {
                let class_ast = &ast_list[class_ind];
                if let Some(
                    ast::Located { node: 
                        ast::StmtKind::ClassDef {
                            name, 
                            body,
                            ..
                        },
                        ..
                    }
                ) = class_ast {
                    (name, body)
                } else { unreachable!("should be class def ast") }
            };

            let class_methods_parsing_result: Vec<(String, Type, DefinitionId)> = Default::default();
            let class_fields_parsing_result: Vec<(String, Type)> = Default::default();
            for b in class_body {
                if let ast::StmtKind::FunctionDef {
                    args: method_args_ast,
                    body: method_body_ast,
                    name: method_name,
                    returns: method_returns_ast,
                    ..
                } = &b.node {
                    let (class_def, method_def) = {
                        // unwrap should not fail
                        let method_ind = class_method_to_def_id
                        .get(&Self::name_mangling(
                            class_name.into(),
                            method_name)
                        ).unwrap().0;
                
                        // split the def_list to two parts to get the
                        // mutable reference to both the method and the class
                        assert_ne!(method_ind, class_ind);
                        let min_ind = (if method_ind > class_ind { class_ind } else { method_ind }) + 1;
                        let (head_slice,
                            tail_slice
                        ) = def_list.split_at_mut(min_ind);
                        let (new_method_ind, new_class_ind) = (
                            if method_ind >= min_ind { method_ind - min_ind } else { method_ind },
                            if class_ind >= min_ind { class_ind - min_ind } else { class_ind }
                        );
                        if new_class_ind == class_ind {
                            (&mut head_slice[new_class_ind], &mut tail_slice[new_method_ind])
                        } else {
                            (&mut tail_slice[new_class_ind], &mut head_slice[new_method_ind])
                        }
                    };
                    let (
                        class_fields,
                        class_methods,
                        class_resolver
                    ) = {
                        if let TopLevelDef::Class {
                            resolver,
                            fields,
                            methods,
                            ..
                        } = class_def.get_mut() {
                            (fields, methods, resolver)
                        } else { unreachable!("must be class def here") }
                    };

                    let arg_tys = method_args_ast
                        .args
                        .iter()
                        .map(|x| -> Result<Type, String> {
                            let annotation = x
                                .node
                                .annotation
                                .as_ref()
                                .ok_or_else(|| "type annotation for function parameter is needed".to_string())?
                                .as_ref();

                            let ty = class_resolver
                                .as_ref()
                                .unwrap()
                                .lock()
                                .parse_type_annotation(
                                    &self.to_top_level_context(),
                                    unifier.borrow_mut(),
                                    &self.primitives,
                                    annotation
                                )?;
                            Ok(ty)
                        })
                        .collect::<Result<Vec<_>, _>>()?;
                    let ret_ty = method_returns_ast
                        .as_ref()
                        .and_then(|x| {
                            Some(
                                class_resolver
                                .as_ref()
                                .unwrap()
                                .lock()
                                .parse_type_annotation(
                                    &self.to_top_level_context(),
                                    unifier.borrow_mut(),
                                    &self.primitives,
                                    x.as_ref()
                                )
                            )
                        }).unwrap()?;
                    
                    let all_tys_ok = {
                        let ret_ty_iter = vec![ret_ty];
                        let ret_ty_iter = ret_ty_iter.iter();
                        let mut all_tys = chain!(arg_tys.iter(), ret_ty_iter);
                        all_tys.all(|x| {
                                let type_enum = unifier.get_ty(*x);
                                match type_enum.as_ref() {
                                    TypeEnum::TObj {obj_id, ..} => {
                                        !to_be_analyzed_class.contains(obj_id)
                                    },
                                    TypeEnum::TVirtual { ty } => {
                                        if let TypeEnum::TObj {obj_id, ..} = unifier.get_ty(*ty).as_ref() {
                                            !to_be_analyzed_class.contains(obj_id)
                                        } else { unreachable!() }
                                    },
                                    _ => unreachable!()
                                }
                            }
                        )
                    };

                    if all_tys_ok {
                        // TODO: put related value to the `class_methods_parsing_result`
                        unimplemented!()
                    } else {
                        to_be_analyzed_class.push(DefinitionId(class_ind));
                        // TODO: go to the next WHILE loop
                        unimplemented!()
                    }
                } else {
                    // what should we do with `class A: a = 3`?
                    continue
                }
            }

            // TODO: now it should be confirmed that every 
            // methods and fields of the class can be correctly typed, put the results
            // into the actual def_list and the unifier
        }
        Ok(())
    }
    
    fn analyze_top_level_inheritance(&mut self) -> Result<(), String> {
        unimplemented!()
    }
    
    fn analyze_top_level_field_instantiation(&mut self) -> Result<(), String> {
        unimplemented!()
    }
}