use ahash::AHashSet;
use pyo3::exceptions::PyValueError;
use std::hash::Hash;

use pyo3::exceptions::PyTypeError;
use pyo3::intern;
use pyo3::prelude::*;
use pyo3::types::{PyBool, PyDict, PySet};

use crate::serializers::SerializationState;
use crate::tools::SchemaDict;

#[derive(Debug, Clone, Default)]
pub(crate) struct SchemaFilter<T> {
    include: Option<AHashSet<T>>,
    exclude: Option<AHashSet<T>>,
}

fn map_negative_index<'py>(value: &Bound<'py, PyAny>, len: Option<usize>) -> PyResult<Bound<'py, PyAny>> {
    let py = value.py();
    match len {
        Some(len) => Ok(value
            .call_method1(intern!(py, "__mod__"), (len,))
            .unwrap_or_else(|_| value.clone())),
        None => {
            // check that it's not negative
            if value.lt(0).unwrap_or(false) {
                Err(PyValueError::new_err(
                    "Negative indices cannot be used to exclude items on unsized iterables",
                ))
            } else {
                Ok(value.clone())
            }
        }
    }
}

fn map_negative_indices<'py>(
    include_or_exclude: &Bound<'py, PyAny>,
    len: Option<usize>,
) -> PyResult<Bound<'py, PyAny>> {
    let py = include_or_exclude.py();
    if let Ok(exclude_dict) = include_or_exclude.downcast::<PyDict>() {
        let out = PyDict::new(py);
        for (k, v) in exclude_dict.iter() {
            out.set_item(map_negative_index(&k, len)?, v)?;
        }
        Ok(out.into_any())
    } else if let Ok(exclude_set) = include_or_exclude.downcast::<PySet>() {
        let mut values = Vec::with_capacity(exclude_set.len());
        for v in exclude_set.iter() {
            values.push(map_negative_index(&v, len)?);
        }
        Ok(PySet::new(py, &values)?.into_any())
    } else {
        // return as is and deal with the error later
        Ok(include_or_exclude.clone())
    }
}

type NextFilters<'py> = Option<(Option<Bound<'py, PyAny>>, Option<Bound<'py, PyAny>>)>;

impl SchemaFilter<usize> {
    pub fn from_schema(schema: &Bound<'_, PyDict>) -> PyResult<Self> {
        let py = schema.py();
        match schema.get_as::<Bound<'_, PyDict>>(intern!(py, "serialization"))? {
            Some(ser) => {
                let include = Self::build_set_ints(ser.get_item(intern!(py, "include"))?)?;
                let exclude = Self::build_set_ints(ser.get_item(intern!(py, "exclude"))?)?;
                Ok(Self { include, exclude })
            }
            None => Ok(SchemaFilter::default()),
        }
    }

    fn build_set_ints(v: Option<Bound<'_, PyAny>>) -> PyResult<Option<AHashSet<usize>>> {
        match v {
            Some(value) => {
                if value.is_none() {
                    Ok(None)
                } else {
                    let py_set = value.downcast::<PySet>()?;
                    let mut set: AHashSet<usize> = AHashSet::with_capacity(py_set.len());

                    for item in py_set {
                        set.insert(item.extract()?);
                    }
                    Ok(Some(set))
                }
            }
            None => Ok(None),
        }
    }

    pub fn index_filter<'py>(
        &self,
        index: usize,
        state: &SerializationState<'_, 'py>,
        len: Option<usize>,
    ) -> PyResult<NextFilters<'py>> {
        let include = state.include().map(|v| map_negative_indices(v, len)).transpose()?;
        let exclude = state.exclude().map(|v| map_negative_indices(v, len)).transpose()?;
        self.filter(index, index, include.as_ref(), exclude.as_ref())
    }
}

impl SchemaFilter<isize> {
    pub fn from_set_hash(include: Option<&Bound<'_, PyAny>>, exclude: Option<&Bound<'_, PyAny>>) -> PyResult<Self> {
        let include = Self::build_set_hashes(include)?;
        let exclude = Self::build_set_hashes(exclude)?;
        Ok(Self { include, exclude })
    }

    fn build_set_hashes(v: Option<&Bound<'_, PyAny>>) -> PyResult<Option<AHashSet<isize>>> {
        match v {
            Some(value) => {
                if value.is_none() {
                    Ok(None)
                } else {
                    let py_set = value.downcast::<PySet>()?;
                    let mut set: AHashSet<isize> = AHashSet::with_capacity(py_set.len());

                    for item in py_set.iter() {
                        set.insert(item.hash()?);
                    }
                    Ok(Some(set))
                }
            }
            None => Ok(None),
        }
    }

    pub fn key_filter<'py>(
        &self,
        key: &Bound<'py, PyAny>,
        state: &SerializationState<'_, 'py>,
    ) -> PyResult<NextFilters<'py>> {
        let hash = key.hash()?;
        self.filter(key, hash, state.include(), state.exclude())
    }
}

trait FilterLogic<T: Eq + Copy> {
    /// whether an `index`/`key` is explicitly included, this is combined with call-time `include` below
    fn explicit_include(&self, value: T) -> bool;
    /// default decision on whether to include the item at a given `index`/`key`
    fn default_filter(&self, value: T) -> bool;

    /// this is the somewhat hellish logic for deciding:
    /// 1. whether we should omit a value at a particular index/key - returning `Ok(None)` here
    /// 2. or include it, in which case, what values of `include` and `exclude` should be passed to it
    fn filter<'py>(
        &self,
        py_key: impl IntoPyObject<'py> + Copy,
        int_key: T,
        include: Option<&Bound<'py, PyAny>>,
        exclude: Option<&Bound<'py, PyAny>>,
    ) -> PyResult<NextFilters<'py>> {
        let mut next_exclude = None;
        if let Some(exclude) = exclude {
            if exclude.is_none() {
                // Do nothing; place this check at the top for performance in the common case
            } else if let Ok(exclude_dict) = exclude.downcast::<PyDict>() {
                let op_exc_value = merge_all_value(exclude_dict, py_key)?;
                if let Some(exc_value) = op_exc_value {
                    if is_ellipsis_like(&exc_value) {
                        // if the index is in exclude, and the exclude value is `None`, we want to omit this index/item
                        return Ok(None);
                    }
                    // if the index is in exclude, and the exclude-value is not `None`,
                    // we want to return `Some((..., Some(next_exclude))`
                    next_exclude = Some(exc_value);
                }
            } else if let Ok(exclude_set) = exclude.downcast::<PySet>() {
                if exclude_set.contains(py_key)? || exclude_set.contains(intern!(exclude_set.py(), "__all__"))? {
                    // index is in the exclude set, we return Ok(None) to omit this index
                    return Ok(None);
                }
            } else if let Some(contains) = check_contains(exclude, py_key)? {
                if contains {
                    return Ok(None);
                }
            } else {
                return Err(PyTypeError::new_err("`exclude` argument must be a set or dict."));
            }
        }

        if let Some(include) = include {
            if include.is_none() {
                // Do nothing; place this check at the top for performance in the common case
            } else if let Ok(include_dict) = include.downcast::<PyDict>() {
                let op_inc_value = merge_all_value(include_dict, py_key)?;

                if let Some(inc_value) = op_inc_value {
                    // if the index is in include, we definitely want to include this index
                    return if is_ellipsis_like(&inc_value) {
                        Ok(Some((None, next_exclude)))
                    } else {
                        Ok(Some((Some(inc_value), next_exclude)))
                    };
                } else if !self.explicit_include(int_key) {
                    // if the index is not in include, include exists, AND it's not in schema include,
                    // this index should be omitted
                    return Ok(None);
                }
            } else if let Ok(include_set) = include.downcast::<PySet>() {
                if include_set.contains(py_key)? || include_set.contains(intern!(include_set.py(), "__all__"))? {
                    return Ok(Some((None, next_exclude)));
                } else if !self.explicit_include(int_key) {
                    // if the index is not in include, include exists, AND it's not in schema include,
                    // this index should be omitted
                    return Ok(None);
                }
            } else if let Some(contains) = check_contains(include, py_key)? {
                if contains {
                    return Ok(Some((None, next_exclude)));
                } else if !self.explicit_include(int_key) {
                    // if the index is not in include, include exists, AND it's not in schema include,
                    // this index should be omitted
                    return Ok(None);
                }
            } else {
                return Err(PyTypeError::new_err("`include` argument must be a set or dict."));
            }
        }

        if next_exclude.is_some() {
            Ok(Some((None, next_exclude)))
        } else if self.default_filter(int_key) {
            Ok(Some((None, None)))
        } else {
            Ok(None)
        }
    }
}

impl<T> FilterLogic<T> for SchemaFilter<T>
where
    T: Hash + Eq + Copy,
{
    fn explicit_include(&self, value: T) -> bool {
        match self.include {
            Some(ref include) => include.contains(&value),
            None => false,
        }
    }

    fn default_filter(&self, value: T) -> bool {
        match (&self.include, &self.exclude) {
            (Some(include), Some(exclude)) => include.contains(&value) && !exclude.contains(&value),
            (Some(include), None) => include.contains(&value),
            (None, Some(exclude)) => !exclude.contains(&value),
            (None, None) => true,
        }
    }
}

#[derive(Debug, Clone)]
pub(super) struct AnyFilter;

impl AnyFilter {
    pub fn new() -> Self {
        AnyFilter {}
    }

    pub fn key_filter<'py>(
        &self,
        key: &Bound<'py, PyAny>,
        state: &SerializationState<'_, 'py>,
    ) -> PyResult<NextFilters<'py>> {
        // just use 0 for the int_key, it's always ignored in the implementation here
        self.filter(key, 0, state.include(), state.exclude())
    }

    pub fn index_filter<'py>(
        &self,
        index: usize,
        state: &SerializationState<'_, 'py>,
        len: Option<usize>,
    ) -> PyResult<NextFilters<'py>> {
        let include = state.include().map(|v| map_negative_indices(v, len)).transpose()?;
        let exclude = state.exclude().map(|v| map_negative_indices(v, len)).transpose()?;
        self.filter(index, index, include.as_ref(), exclude.as_ref())
    }
}

/// if a `__contains__` method exists, call it with the key and `__all__`, and return the result
/// if it doesn't exist, or calling it fails (e.g. it's not a function), return `None`
fn check_contains<'py>(obj: &Bound<'py, PyAny>, py_key: impl IntoPyObject<'py> + Copy) -> PyResult<Option<bool>> {
    let py = obj.py();
    match obj.getattr(intern!(py, "__contains__")) {
        Ok(contains_method) => {
            if let Ok(result) = contains_method.call1((py_key,)) {
                Ok(Some(
                    result.is_truthy()? || contains_method.call1((intern!(py, "__all__"),))?.is_truthy()?,
                ))
            } else {
                Ok(None)
            }
        }
        Err(_) => Ok(None),
    }
}

impl<T> FilterLogic<T> for AnyFilter
where
    T: Eq + Copy,
{
    fn explicit_include(&self, _value: T) -> bool {
        false
    }

    fn default_filter(&self, _value: T) -> bool {
        true
    }
}

/// detect both ellipsis and `True` to be compatible with pydantic V1
fn is_ellipsis_like(v: &Bound<'_, PyAny>) -> bool {
    v.is(v.py().Ellipsis())
        || match v.downcast::<PyBool>() {
            Ok(b) => b.is_true(),
            Err(_) => false,
        }
}

/// lookup the dict, for the key and "__all__" key, and merge them following the same rules as pydantic V1
fn merge_all_value<'py>(
    dict: &Bound<'py, PyDict>,
    py_key: impl IntoPyObject<'py> + Copy,
) -> PyResult<Option<Bound<'py, PyAny>>> {
    let op_item_value = dict.get_item(py_key)?;
    let op_all_value = dict.get_item(intern!(dict.py(), "__all__"))?;

    match (op_item_value, op_all_value) {
        (Some(item_value), Some(all_value)) => {
            if is_ellipsis_like(&item_value) || is_ellipsis_like(&all_value) {
                Ok(Some(item_value))
            } else {
                let item_dict = as_dict(&item_value)?;
                let item_dict_merged = merge_dicts(&item_dict, &all_value)?;
                Ok(Some(item_dict_merged.into_any()))
            }
        }
        (op_item_value @ Some(_), None) => Ok(op_item_value),
        (None, op_all_value @ Some(_)) => Ok(op_all_value),
        (None, None) => Ok(None),
    }
}

fn as_dict<'py>(value: &Bound<'py, PyAny>) -> PyResult<Bound<'py, PyDict>> {
    if let Ok(dict) = value.downcast::<PyDict>() {
        dict.copy()
    } else if let Ok(set) = value.downcast::<PySet>() {
        let py = value.py();
        let dict = PyDict::new(py);
        for item in set.iter() {
            dict.set_item(item, py.Ellipsis())?;
        }
        Ok(dict)
    } else {
        Err(PyTypeError::new_err(
            "`include` and `exclude` must be of type `dict[str | int, <recursive> | ...] | set[str | int | ...]`",
        ))
    }
}

fn merge_dicts<'py>(item_dict: &Bound<'py, PyDict>, all_value: &Bound<'py, PyAny>) -> PyResult<Bound<'py, PyDict>> {
    let item_dict = item_dict.copy()?;
    if let Ok(all_dict) = all_value.downcast::<PyDict>() {
        for (all_key, all_value) in all_dict.iter() {
            if let Some(item_value) = item_dict.get_item(&all_key)? {
                if is_ellipsis_like(&item_value) {
                    continue;
                }
                let item_value_dict = as_dict(&item_value)?;
                // if the all value is an ellipsis, we don't overwrite the item value
                if !is_ellipsis_like(&all_value) {
                    item_dict.set_item(all_key, merge_dicts(&item_value_dict, &all_value)?)?;
                }
            } else {
                item_dict.set_item(all_key, all_value)?;
            }
        }
    } else if let Ok(set) = all_value.downcast::<PySet>() {
        for item in set.iter() {
            if !item_dict.contains(&item)? {
                item_dict.set_item(item, set.py().Ellipsis())?;
            }
        }
    } else {
        return Err(PyTypeError::new_err(
            "'__all__' key of `include` and `exclude` must be of type `dict[str | int, <recursive> | ...] | set[str | int | ...]`",
        ));
    }
    Ok(item_dict)
}
