use std::cell::{Cell, RefCell};
use std::fmt;
use std::hash::{Hash, Hasher};

use crate::pyobject::{
    IdProtocol, OptionalArg, PyContext, PyIteratorValue, PyObject, PyObjectRef, PyRef, PyResult,
    PyValue,
};
use crate::vm::{ReprGuard, VirtualMachine};

use super::objbool;
use super::objint;
use super::objsequence::{
    get_elements, get_item, seq_equal, seq_ge, seq_gt, seq_le, seq_lt, seq_mul,
};
use super::objstr;
use super::objtype;

#[derive(Default)]
pub struct PyTuple {
    // TODO: shouldn't be public
    // TODO: tuples are immutable, remove this RefCell
    pub elements: RefCell<Vec<PyObjectRef>>,
}

impl fmt::Debug for PyTuple {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        // TODO: implement more informational, non-recursive Debug formatter
        f.write_str("tuple")
    }
}

impl From<Vec<PyObjectRef>> for PyTuple {
    fn from(elements: Vec<PyObjectRef>) -> Self {
        PyTuple {
            elements: RefCell::new(elements),
        }
    }
}

impl PyValue for PyTuple {
    fn class(ctx: &PyContext) -> PyObjectRef {
        ctx.tuple_type()
    }
}

pub type PyTupleRef = PyRef<PyTuple>;

impl PyTupleRef {
    fn lt(self, other: PyObjectRef, vm: &mut VirtualMachine) -> PyResult<bool> {
        if objtype::isinstance(&other, &vm.ctx.tuple_type()) {
            let zelf = self.elements.borrow();
            let other = get_elements(&other);
            Ok(seq_lt(vm, &zelf, &other)?)
        } else {
            Err(vm.new_type_error(format!("Cannot compare {} and {} using '<'", self, other)))
        }
    }

    fn gt(self, other: PyObjectRef, vm: &mut VirtualMachine) -> PyResult<bool> {
        if objtype::isinstance(&other, &vm.ctx.tuple_type()) {
            let zelf = self.elements.borrow();
            let other = get_elements(&other);
            Ok(seq_gt(vm, &zelf, &other)?)
        } else {
            Err(vm.new_type_error(format!("Cannot compare {} and {} using '>'", self, other)))
        }
    }

    fn ge(self, other: PyObjectRef, vm: &mut VirtualMachine) -> PyResult<bool> {
        if objtype::isinstance(&other, &vm.ctx.tuple_type()) {
            let zelf = self.elements.borrow();
            let other = get_elements(&other);
            Ok(seq_ge(vm, &zelf, &other)?)
        } else {
            Err(vm.new_type_error(format!("Cannot compare {} and {} using '>='", self, other)))
        }
    }

    fn le(self, other: PyObjectRef, vm: &mut VirtualMachine) -> PyResult<bool> {
        if objtype::isinstance(&other, &vm.ctx.tuple_type()) {
            let zelf = self.elements.borrow();
            let other = get_elements(&other);
            Ok(seq_le(vm, &zelf, &other)?)
        } else {
            Err(vm.new_type_error(format!("Cannot compare {} and {} using '<='", self, other)))
        }
    }

    fn add(self, other: PyObjectRef, vm: &mut VirtualMachine) -> PyResult {
        if objtype::isinstance(&other, &vm.ctx.tuple_type()) {
            let e1 = self.elements.borrow();
            let e2 = get_elements(&other);
            let elements = e1.iter().chain(e2.iter()).cloned().collect();
            Ok(vm.ctx.new_tuple(elements))
        } else {
            Err(vm.new_type_error(format!("Cannot add {} and {}", self, other)))
        }
    }

    fn count(self, needle: PyObjectRef, vm: &mut VirtualMachine) -> PyResult<usize> {
        let mut count: usize = 0;
        for element in self.elements.borrow().iter() {
            if element.is(&needle) {
                count += 1;
            } else {
                let is_eq = vm._eq(element.clone(), needle.clone())?;
                if objbool::boolval(vm, is_eq)? {
                    count += 1;
                }
            }
        }
        Ok(count)
    }

    fn eq(self, other: PyObjectRef, vm: &mut VirtualMachine) -> PyResult<bool> {
        if objtype::isinstance(&other, &vm.ctx.tuple_type()) {
            let zelf = &self.elements.borrow();
            let other = get_elements(&other);
            seq_equal(vm, &zelf, &other)
        } else {
            Ok(false)
        }
    }

    fn hash(self, vm: &mut VirtualMachine) -> PyResult<u64> {
        let mut hasher = std::collections::hash_map::DefaultHasher::new();
        for element in self.elements.borrow().iter() {
            let hash_result = vm.call_method(element, "__hash__", vec![])?;
            let element_hash = objint::get_value(&hash_result);
            element_hash.hash(&mut hasher);
        }
        Ok(hasher.finish())
    }

    fn iter(self, vm: &mut VirtualMachine) -> PyObjectRef {
        PyObject::new(
            PyIteratorValue {
                position: Cell::new(0),
                iterated_obj: self.into_object(),
            },
            vm.ctx.iter_type(),
        )
    }

    fn len(self, _vm: &mut VirtualMachine) -> usize {
        self.elements.borrow().len()
    }

    fn repr(self, vm: &mut VirtualMachine) -> PyResult<String> {
        let s = if let Some(_guard) = ReprGuard::enter(self.as_object()) {
            let mut str_parts = vec![];
            for elem in self.elements.borrow().iter() {
                let s = vm.to_repr(elem)?;
                str_parts.push(objstr::get_value(&s));
            }

            if str_parts.len() == 1 {
                format!("({},)", str_parts[0])
            } else {
                format!("({})", str_parts.join(", "))
            }
        } else {
            "(...)".to_string()
        };
        Ok(s)
    }

    fn mul(self, counter: isize, vm: &mut VirtualMachine) -> PyObjectRef {
        let new_elements = seq_mul(&self.elements.borrow(), counter);
        vm.ctx.new_tuple(new_elements)
    }

    fn getitem(self, needle: PyObjectRef, vm: &mut VirtualMachine) -> PyResult {
        get_item(
            vm,
            self.as_object(),
            &self.elements.borrow(),
            needle.clone(),
        )
    }

    fn index(self, needle: PyObjectRef, vm: &mut VirtualMachine) -> PyResult<usize> {
        for (index, element) in self.elements.borrow().iter().enumerate() {
            if element.is(&needle) {
                return Ok(index);
            }
            let is_eq = vm._eq(needle.clone(), element.clone())?;
            if objbool::boolval(vm, is_eq)? {
                return Ok(index);
            }
        }
        Err(vm.new_value_error("tuple.index(x): x not in tuple".to_string()))
    }

    fn contains(self, needle: PyObjectRef, vm: &mut VirtualMachine) -> PyResult<bool> {
        for element in self.elements.borrow().iter() {
            if element.is(&needle) {
                return Ok(true);
            }
            let is_eq = vm._eq(needle.clone(), element.clone())?;
            if objbool::boolval(vm, is_eq)? {
                return Ok(true);
            }
        }
        Ok(false)
    }
}

fn tuple_new(
    cls: PyRef<objtype::PyClass>,
    iterable: OptionalArg<PyObjectRef>,
    vm: &mut VirtualMachine,
) -> PyResult {
    if !objtype::issubclass(cls.as_object(), &vm.ctx.tuple_type()) {
        return Err(vm.new_type_error(format!("{} is not a subtype of tuple", cls)));
    }

    let elements = if let OptionalArg::Present(iterable) = iterable {
        vm.extract_elements(&iterable)?
    } else {
        vec![]
    };

    Ok(PyObject::new(PyTuple::from(elements), cls.into_object()))
}

#[rustfmt::skip] // to avoid line splitting
pub fn init(context: &PyContext) {
    let tuple_type = &context.tuple_type;
    let tuple_doc = "tuple() -> empty tuple
tuple(iterable) -> tuple initialized from iterable's items

If the argument is a tuple, the return value is the same object.";
    context.set_attr(&tuple_type, "__add__", context.new_rustfunc(PyTupleRef::add));
    context.set_attr(&tuple_type, "__eq__", context.new_rustfunc(PyTupleRef::eq));
    context.set_attr(&tuple_type,"__contains__",context.new_rustfunc(PyTupleRef::contains));
    context.set_attr(&tuple_type,"__getitem__",context.new_rustfunc(PyTupleRef::getitem));
    context.set_attr(&tuple_type, "__hash__", context.new_rustfunc(PyTupleRef::hash));
    context.set_attr(&tuple_type, "__iter__", context.new_rustfunc(PyTupleRef::iter));
    context.set_attr(&tuple_type, "__len__", context.new_rustfunc(PyTupleRef::len));
    context.set_attr(&tuple_type, "__new__", context.new_rustfunc(tuple_new));
    context.set_attr(&tuple_type, "__mul__", context.new_rustfunc(PyTupleRef::mul));
    context.set_attr(&tuple_type, "__repr__", context.new_rustfunc(PyTupleRef::repr));
    context.set_attr(&tuple_type, "count", context.new_rustfunc(PyTupleRef::count));
    context.set_attr(&tuple_type, "__lt__", context.new_rustfunc(PyTupleRef::lt));
    context.set_attr(&tuple_type, "__le__", context.new_rustfunc(PyTupleRef::le));
    context.set_attr(&tuple_type, "__gt__", context.new_rustfunc(PyTupleRef::gt));
    context.set_attr(&tuple_type, "__ge__", context.new_rustfunc(PyTupleRef::ge));
    context.set_attr(&tuple_type,"__doc__",context.new_str(tuple_doc.to_string()));
    context.set_attr(&tuple_type, "index", context.new_rustfunc(PyTupleRef::index));
}