use std::fmt;

use crate::builtins::{PyDictRef, PyStr, PyStrRef};
use crate::pyobject::{IntoPyObject, ItemProtocol, TryIntoRef};
use crate::VirtualMachine;

#[derive(Clone)]
pub struct Scope {
    pub locals: PyDictRef,
    pub globals: PyDictRef,
}

impl fmt::Debug for Scope {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        // TODO: have a more informative Debug impl that DOESN'T recurse and cause a stack overflow
        f.write_str("Scope")
    }
}

impl Scope {
    #[inline]
    pub fn new(locals: Option<PyDictRef>, globals: PyDictRef) -> Scope {
        let locals = locals.unwrap_or_else(|| globals.clone());
        Scope { locals, globals }
    }

    pub fn with_builtins(
        locals: Option<PyDictRef>,
        globals: PyDictRef,
        vm: &VirtualMachine,
    ) -> Scope {
        if !globals.contains_key("__builtins__", vm) {
            globals
                .set_item("__builtins__", vm.builtins.clone(), vm)
                .unwrap();
        }
        Scope::new(locals, globals)
    }

    // pub fn get_locals(&self) -> &PyDictRef {
    //     match self.locals.first() {
    //         Some(dict) => dict,
    //         None => &self.globals,
    //     }
    // }

    // pub fn get_only_locals(&self) -> Option<PyDictRef> {
    //     self.locals.first().cloned()
    // }

    // pub fn new_child_scope_with_locals(&self, locals: PyDictRef) -> Scope {
    //     let mut new_locals = Vec::with_capacity(self.locals.len() + 1);
    //     new_locals.push(locals);
    //     new_locals.extend_from_slice(&self.locals);
    //     Scope {
    //         locals: new_locals,
    //         globals: self.globals.clone(),
    //     }
    // }

    // pub fn new_child_scope(&self, ctx: &PyContext) -> Scope {
    //     self.new_child_scope_with_locals(ctx.new_dict())
    // }

    // #[cfg_attr(feature = "flame-it", flame("Scope"))]
    // pub fn load_name(&self, vm: &VirtualMachine, name: impl PyName) -> Option<PyObjectRef> {
    //     for dict in self.locals.iter() {
    //         if let Some(value) = dict.get_item_option(name.clone(), vm).unwrap() {
    //             return Some(value);
    //         }
    //     }

    //     // Fall back to loading a global after all scopes have been searched!
    //     self.load_global(vm, name)
    // }

    // #[cfg_attr(feature = "flame-it", flame("Scope"))]
    // /// Load a local name. Only check the local dictionary for the given name.
    // pub fn load_local(&self, vm: &VirtualMachine, name: impl PyName) -> Option<PyObjectRef> {
    //     self.get_locals().get_item_option(name, vm).unwrap()
    // }

    // #[cfg_attr(feature = "flame-it", flame("Scope"))]
    // pub fn load_cell(&self, vm: &VirtualMachine, name: impl PyName) -> Option<PyObjectRef> {
    //     for dict in self.locals.iter().skip(1) {
    //         if let Some(value) = dict.get_item_option(name.clone(), vm).unwrap() {
    //             return Some(value);
    //         }
    //     }
    //     None
    // }

    // pub fn store_cell(&self, vm: &VirtualMachine, name: impl PyName, value: PyObjectRef) {
    //     // find the innermost outer scope that contains the symbol name
    //     if let Some(locals) = self
    //         .locals
    //         .iter()
    //         .rev()
    //         .find(|l| l.contains_key(name.clone(), vm))
    //     {
    //         // add to the symbol
    //         locals.set_item(name, value, vm).unwrap();
    //     } else {
    //         // somewhat limited solution -> fallback to the old rustpython strategy
    //         // and store the next outer scope
    //         // This case is usually considered as a failure case, but kept for the moment
    //         // to support the scope propagation for named expression assignments to so far
    //         // unknown names in comprehensions. We need to consider here more context
    //         // information for correct handling.
    //         self.locals
    //             .get(1)
    //             .expect("no outer scope for non-local")
    //             .set_item(name, value, vm)
    //             .unwrap();
    //     }
    // }

    // pub fn store_name(&self, vm: &VirtualMachine, key: impl PyName, value: PyObjectRef) {
    //     self.get_locals().set_item(key, value, vm).unwrap();
    // }

    // pub fn delete_name(&self, vm: &VirtualMachine, key: impl PyName) -> PyResult {
    //     self.get_locals().del_item(key, vm)
    // }

    // #[cfg_attr(feature = "flame-it", flame("Scope"))]
    // /// Load a global name.
    // pub fn load_global(&self, vm: &VirtualMachine, name: impl PyName) -> Option<PyObjectRef> {
    //     if let Some(value) = self.globals.get_item_option(name.clone(), vm).unwrap() {
    //         Some(value)
    //     } else {
    //         vm.get_attribute(vm.builtins.clone(), name).ok()
    //     }
    // }

    // pub fn store_global(&self, vm: &VirtualMachine, name: impl PyName, value: PyObjectRef) {
    //     self.globals.set_item(name, value, vm).unwrap();
    // }
}

mod sealed {
    pub trait Sealed {}
    impl Sealed for &str {}
    impl Sealed for super::PyStrRef {}
}
pub trait PyName:
    sealed::Sealed + crate::dictdatatype::DictKey + Clone + IntoPyObject + TryIntoRef<PyStr>
{
}
impl PyName for &str {}
impl PyName for PyStrRef {}