use std::hash::BuildHasher;

use arrow::bitmap::MutableBitmap;
use either::Either;
use parking_lot::RwLock;
use polars::prelude::*;
use polars_ffi::version_0::SeriesExport;
use pyo3::exceptions::PyIndexError;
use pyo3::prelude::*;
use pyo3::pybacked::PyBackedStr;
use pyo3::types::{PyList, PyType};

use self::row_encode::{_get_rows_encoded_ca, _get_rows_encoded_ca_unordered};
use super::PyDataFrame;
use crate::PyLazyFrame;
use crate::conversion::Wrap;
use crate::error::PyPolarsErr;
use crate::prelude::strings_to_pl_smallstr;
use crate::py_modules::polars;
use crate::series::{PySeries, ToPySeries, ToSeries};
use crate::utils::{EnterPolarsExt, to_py_err};

#[pymethods]
impl PyDataFrame {
    #[new]
    pub fn __init__(columns: Vec<PySeries>) -> PyResult<Self> {
        let columns = columns.to_series();
        // @scalar-opt
        let columns = columns.into_iter().map(|s| s.into()).collect();
        let df = DataFrame::new_infer_height(columns).map_err(PyPolarsErr::from)?;
        Ok(PyDataFrame::new(df))
    }

    #[staticmethod]
    pub fn empty_with_height(height: u64) -> PyResult<Self> {
        Ok(PyDataFrame::new(DataFrame::empty_with_height(
            IdxSize::try_from(height)
                .map_err(|_| polars_err!(bigidx, ctx = "DataFrame(height = _)", size = height))
                .map_err(to_py_err)? as usize,
        )))
    }

    pub fn estimated_size(&self) -> usize {
        self.df.read().estimated_size()
    }

    pub fn dtype_strings(&self) -> Vec<String> {
        self.df
            .read()
            .columns()
            .iter()
            .map(|s| format!("{}", s.dtype()))
            .collect()
    }

    pub fn add(&self, py: Python<'_>, s: &PySeries) -> PyResult<Self> {
        py.enter_polars_df(|| &*self.df.read() + &*s.series.read())
    }

    pub fn sub(&self, py: Python<'_>, s: &PySeries) -> PyResult<Self> {
        py.enter_polars_df(|| &*self.df.read() - &*s.series.read())
    }

    pub fn mul(&self, py: Python<'_>, s: &PySeries) -> PyResult<Self> {
        py.enter_polars_df(|| &*self.df.read() * &*s.series.read())
    }

    pub fn div(&self, py: Python<'_>, s: &PySeries) -> PyResult<Self> {
        py.enter_polars_df(|| &*self.df.read() / &*s.series.read())
    }

    pub fn rem(&self, py: Python<'_>, s: &PySeries) -> PyResult<Self> {
        py.enter_polars_df(|| &*self.df.read() % &*s.series.read())
    }

    pub fn add_df(&self, py: Python<'_>, s: &Self) -> PyResult<Self> {
        py.enter_polars_df(|| &*self.df.read() + &*s.df.read())
    }

    pub fn sub_df(&self, py: Python<'_>, s: &Self) -> PyResult<Self> {
        py.enter_polars_df(|| &*self.df.read() - &*s.df.read())
    }

    pub fn mul_df(&self, py: Python<'_>, s: &Self) -> PyResult<Self> {
        py.enter_polars_df(|| &*self.df.read() * &*s.df.read())
    }

    pub fn div_df(&self, py: Python<'_>, s: &Self) -> PyResult<Self> {
        py.enter_polars_df(|| &*self.df.read() / &*s.df.read())
    }

    pub fn rem_df(&self, py: Python<'_>, s: &Self) -> PyResult<Self> {
        py.enter_polars_df(|| &*self.df.read() % &*s.df.read())
    }

    #[pyo3(signature = (n, with_replacement, shuffle, seed=None))]
    pub fn sample_n(
        &self,
        py: Python<'_>,
        n: &PySeries,
        with_replacement: bool,
        shuffle: bool,
        seed: Option<u64>,
    ) -> PyResult<Self> {
        py.enter_polars_df(|| {
            self.df
                .read()
                .sample_n(&n.series.read(), with_replacement, shuffle, seed)
        })
    }

    #[pyo3(signature = (frac, with_replacement, shuffle, seed=None))]
    pub fn sample_frac(
        &self,
        py: Python<'_>,
        frac: &PySeries,
        with_replacement: bool,
        shuffle: bool,
        seed: Option<u64>,
    ) -> PyResult<Self> {
        py.enter_polars_df(|| {
            self.df
                .read()
                .sample_frac(&frac.series.read(), with_replacement, shuffle, seed)
        })
    }

    pub fn rechunk(&self, py: Python) -> PyResult<Self> {
        py.enter_polars_df(|| {
            let mut df = self.df.read().clone();
            df.rechunk_mut_par();
            Ok(df)
        })
    }

    /// Format `DataFrame` as String
    pub fn as_str(&self) -> String {
        format!("{:?}", self.df.read())
    }

    pub fn get_columns(&self) -> Vec<PySeries> {
        let cols = self.df.read().columns().to_vec();
        cols.to_pyseries()
    }

    /// Get column names
    pub fn columns(&self) -> Vec<String> {
        self.df
            .read()
            .columns()
            .iter()
            .map(|s| s.name().to_string())
            .collect()
    }

    /// set column names
    pub fn set_column_names(&self, names: Vec<PyBackedStr>) -> PyResult<()> {
        self.df
            .write()
            .set_column_names(&names)
            .map_err(PyPolarsErr::from)?;
        Ok(())
    }

    /// Get datatypes
    pub fn dtypes<'py>(&self, py: Python<'py>) -> PyResult<Bound<'py, PyList>> {
        let df = self.df.read();
        let iter = df
            .columns()
            .iter()
            .map(|s| Wrap(s.dtype().clone()).into_pyobject(py).unwrap());
        PyList::new(py, iter)
    }

    pub fn n_chunks(&self) -> usize {
        self.df.read().first_col_n_chunks()
    }

    pub fn shape(&self) -> (usize, usize) {
        self.df.read().shape()
    }

    pub fn height(&self) -> usize {
        self.df.read().height()
    }

    pub fn width(&self) -> usize {
        self.df.read().width()
    }

    pub fn is_empty(&self) -> bool {
        self.df.read().shape_has_zero()
    }

    pub fn hstack(&self, py: Python<'_>, columns: Vec<PySeries>) -> PyResult<Self> {
        let columns = columns.to_series();
        // @scalar-opt
        let columns = columns.into_iter().map(Into::into).collect::<Vec<_>>();
        py.enter_polars_df(|| self.df.read().hstack(&columns))
    }

    pub fn hstack_mut(&self, py: Python<'_>, columns: Vec<PySeries>) -> PyResult<()> {
        let columns = columns.to_series();
        // @scalar-opt
        let columns = columns.into_iter().map(Into::into).collect::<Vec<_>>();
        py.enter_polars(|| self.df.write().hstack_mut(&columns).map(drop))?;
        Ok(())
    }

    pub fn vstack(&self, py: Python<'_>, other: &PyDataFrame) -> PyResult<Self> {
        py.enter_polars_df(|| self.df.read().vstack(&other.df.read()))
    }

    pub fn vstack_mut(&self, py: Python<'_>, other: &PyDataFrame) -> PyResult<()> {
        py.enter_polars(|| {
            // Prevent self-vstack deadlocks.
            let other = other.df.read().clone();
            self.df.write().vstack_mut_owned(other)?;
            PolarsResult::Ok(())
        })?;
        Ok(())
    }

    pub fn extend(&self, py: Python<'_>, other: &PyDataFrame) -> PyResult<()> {
        py.enter_polars(|| {
            // Prevent self-extend deadlocks.
            let other = other.df.read().clone();
            self.df.write().extend(&other)
        })?;
        Ok(())
    }

    pub fn drop_in_place(&self, name: &str) -> PyResult<PySeries> {
        let s = self
            .df
            .write()
            .drop_in_place(name)
            .map_err(PyPolarsErr::from)?;
        let s = s.take_materialized_series();
        Ok(PySeries::from(s))
    }

    pub fn to_series(&self, index: isize) -> PyResult<PySeries> {
        let df = &self.df.read();

        let index_adjusted = if index < 0 {
            df.width().checked_sub(index.unsigned_abs())
        } else {
            Some(usize::try_from(index).unwrap())
        };

        let s = index_adjusted.and_then(|i| df.select_at_idx(i));
        match s {
            Some(s) => Ok(PySeries::new(s.as_materialized_series().clone())),
            None => Err(PyIndexError::new_err(
                polars_err!(oob = index, df.width()).to_string(),
            )),
        }
    }

    pub fn get_column_index(&self, name: &str) -> PyResult<usize> {
        Ok(self
            .df
            .read()
            .try_get_column_index(name)
            .map_err(PyPolarsErr::from)?)
    }

    pub fn get_column(&self, name: &str) -> PyResult<PySeries> {
        let series = self
            .df
            .read()
            .column(name)
            .map(|s| PySeries::new(s.as_materialized_series().clone()))
            .map_err(PyPolarsErr::from)?;
        Ok(series)
    }

    pub fn select(&self, py: Python<'_>, columns: Vec<PyBackedStr>) -> PyResult<Self> {
        py.enter_polars_df(|| self.df.read().select(columns.iter().map(|x| &**x)))
    }

    pub fn gather(&self, py: Python<'_>, indices: Wrap<Vec<IdxSize>>) -> PyResult<Self> {
        let indices = indices.0;
        let indices = IdxCa::from_vec("".into(), indices);
        py.enter_polars_df(|| self.df.read().take(&indices))
    }

    pub fn gather_with_series(&self, py: Python<'_>, indices: &PySeries) -> PyResult<Self> {
        let idx_s = indices.series.read();
        let indices = idx_s.idx().map_err(PyPolarsErr::from)?;
        py.enter_polars_df(|| self.df.read().take(indices))
    }

    pub fn replace(&self, column: &str, new_col: PySeries) -> PyResult<()> {
        self.df
            .write()
            .replace(column, new_col.series.into_inner().into_column())
            .map_err(PyPolarsErr::from)?;
        Ok(())
    }

    pub fn replace_column(&self, index: usize, new_column: PySeries) -> PyResult<()> {
        self.df
            .write()
            .replace_column(index, new_column.series.into_inner().into_column())
            .map_err(PyPolarsErr::from)?;
        Ok(())
    }

    pub fn insert_column(&self, index: usize, column: PySeries) -> PyResult<()> {
        self.df
            .write()
            .insert_column(index, column.series.into_inner().into_column())
            .map_err(PyPolarsErr::from)?;
        Ok(())
    }

    #[pyo3(signature = (offset, length))]
    pub fn slice(&self, py: Python<'_>, offset: i64, length: Option<usize>) -> PyResult<Self> {
        py.enter_polars_df(|| {
            let df = self.df.read();
            Ok(df.slice(offset, length.unwrap_or_else(|| df.height())))
        })
    }

    pub fn head(&self, py: Python<'_>, n: usize) -> PyResult<Self> {
        py.enter_polars_df(|| Ok(self.df.read().head(Some(n))))
    }

    pub fn tail(&self, py: Python<'_>, n: usize) -> PyResult<Self> {
        py.enter_polars_df(|| Ok(self.df.read().tail(Some(n))))
    }

    pub fn is_unique(&self, py: Python) -> PyResult<PySeries> {
        py.enter_polars_series(|| self.df.read().is_unique())
    }

    pub fn is_duplicated(&self, py: Python) -> PyResult<PySeries> {
        py.enter_polars_series(|| self.df.read().is_duplicated())
    }

    pub fn equals(&self, py: Python<'_>, other: &PyDataFrame, null_equal: bool) -> PyResult<bool> {
        if null_equal {
            py.enter_polars_ok(|| self.df.read().equals_missing(&other.df.read()))
        } else {
            py.enter_polars_ok(|| self.df.read().equals(&other.df.read()))
        }
    }

    #[pyo3(signature = (name, offset=None))]
    pub fn with_row_index(
        &self,
        py: Python<'_>,
        name: &str,
        offset: Option<IdxSize>,
    ) -> PyResult<Self> {
        py.enter_polars_df(|| self.df.read().with_row_index(name.into(), offset))
    }

    pub fn _to_metadata(&self) -> Self {
        Self {
            df: RwLock::new(self.df.read()._to_metadata()),
        }
    }

    pub fn group_by_map_groups(
        &self,
        py: Python<'_>,
        by: Vec<PyBackedStr>,
        lambda: Py<PyAny>,
        maintain_order: bool,
    ) -> PyResult<Self> {
        py.enter_polars_df(|| {
            let df = self.df.read().clone(); // Clone so we can't deadlock on re-entrance from lambda.
            let gb = if maintain_order {
                df.group_by_stable(by.iter().map(|x| &**x))
            } else {
                df.group_by(by.iter().map(|x| &**x))
            }?;

            let function = move |df: DataFrame| {
                Python::attach(|py| {
                    let pypolars = polars(py).bind(py);
                    let pydf = PyDataFrame::new(df);
                    let python_df_wrapper =
                        pypolars.getattr("wrap_df").unwrap().call1((pydf,)).unwrap();

                    // Call the lambda and get a python-side DataFrame wrapper.
                    let result_df_wrapper = match lambda.call1(py, (python_df_wrapper,)) {
                        Ok(pyobj) => pyobj,
                        Err(e) => panic!("UDF failed: {}", e.value(py)),
                    };
                    let py_pydf = result_df_wrapper.getattr(py, "_df").expect(
                        "Could not get DataFrame attribute '_df'. Make sure that you return a DataFrame object.",
                    );

                    let pydf = py_pydf.extract::<PyDataFrame>(py).unwrap();
                    Ok(pydf.df.into_inner())
                })
            };

            gb.apply(function)
        })
    }

    #[allow(clippy::should_implement_trait)]
    pub fn clone(&self) -> Self {
        Clone::clone(self)
    }

    #[cfg(feature = "pivot")]
    #[pyo3(signature = (on, index, value_name=None, variable_name=None))]
    pub fn unpivot(
        &self,
        py: Python<'_>,
        on: Option<Vec<PyBackedStr>>,
        index: Vec<PyBackedStr>,
        value_name: Option<&str>,
        variable_name: Option<&str>,
    ) -> PyResult<Self> {
        use polars_ops::unpivot::UnpivotDF;
        let args = UnpivotArgsIR::new(
            self.df.read().get_column_names_owned(),
            on.map(strings_to_pl_smallstr),
            strings_to_pl_smallstr(index),
            value_name.map(|s| s.into()),
            variable_name.map(|s| s.into()),
        );

        py.enter_polars_df(|| self.df.read().unpivot2(args))
    }

    pub fn partition_by(
        &self,
        py: Python<'_>,
        by: Vec<String>,
        maintain_order: bool,
        include_key: bool,
    ) -> PyResult<Vec<Self>> {
        let out = py.enter_polars(|| {
            if maintain_order {
                self.df.read().partition_by_stable(by, include_key)
            } else {
                self.df.read().partition_by(by, include_key)
            }
        })?;

        Ok(out.into_iter().map(PyDataFrame::from).collect())
    }

    pub fn lazy(&self) -> PyLazyFrame {
        self.df.read().clone().lazy().into()
    }

    #[pyo3(signature = (columns, separator, drop_first, drop_nulls))]
    pub fn to_dummies(
        &self,
        py: Python<'_>,
        columns: Option<Vec<String>>,
        separator: Option<&str>,
        drop_first: bool,
        drop_nulls: bool,
    ) -> PyResult<Self> {
        py.enter_polars_df(|| match columns {
            Some(cols) => self.df.read().columns_to_dummies(
                cols.iter().map(|x| x as &str).collect(),
                separator,
                drop_first,
                drop_nulls,
            ),
            None => self.df.read().to_dummies(separator, drop_first, drop_nulls),
        })
    }

    pub fn null_count(&self, py: Python) -> PyResult<Self> {
        py.enter_polars_df(|| Ok(self.df.read().null_count()))
    }

    pub fn shrink_to_fit(&self, py: Python) -> PyResult<()> {
        py.enter_polars_ok(|| self.df.write().shrink_to_fit())
    }

    pub fn hash_rows(
        &self,
        py: Python<'_>,
        k0: u64,
        k1: u64,
        k2: u64,
        k3: u64,
    ) -> PyResult<PySeries> {
        // TODO: don't expose all these seeds.
        let seed = PlFixedStateQuality::default().hash_one((k0, k1, k2, k3));
        let hb = PlSeedableRandomStateQuality::seed_from_u64(seed);
        py.enter_polars_series(|| self.df.write().hash_rows(Some(hb)))
    }

    #[pyo3(signature = (keep_names_as, column_names))]
    pub fn transpose(
        &self,
        py: Python<'_>,
        keep_names_as: Option<&str>,
        column_names: &Bound<PyAny>,
    ) -> PyResult<Self> {
        let new_col_names = if let Ok(name) = column_names.extract::<Vec<String>>() {
            Some(Either::Right(name))
        } else if let Ok(name) = column_names.extract::<String>() {
            Some(Either::Left(name))
        } else {
            None
        };
        py.enter_polars_df(|| self.df.write().transpose(keep_names_as, new_col_names))
    }

    pub fn upsample(
        &self,
        py: Python<'_>,
        by: Vec<String>,
        index_column: &str,
        every: &str,
        stable: bool,
    ) -> PyResult<Self> {
        let every = Duration::try_parse(every).map_err(PyPolarsErr::from)?;
        py.enter_polars_df(|| {
            if stable {
                self.df.read().upsample_stable(by, index_column, every)
            } else {
                self.df.read().upsample(by, index_column, every)
            }
        })
    }

    pub fn to_struct(
        &self,
        py: Python<'_>,
        name: &str,
        invalid_indices: Vec<usize>,
    ) -> PyResult<PySeries> {
        py.enter_polars_series(|| {
            let mut ca = self.df.read().clone().into_struct(name.into());

            if !invalid_indices.is_empty() {
                let mut validity = MutableBitmap::with_capacity(ca.len());
                validity.extend_constant(ca.len(), true);
                for i in invalid_indices {
                    validity.set(i, false);
                }
                ca.rechunk_mut();
                Ok(ca.with_outer_validity(Some(validity.freeze())))
            } else {
                Ok(ca)
            }
        })
    }

    pub fn clear(&self, py: Python) -> PyResult<Self> {
        py.enter_polars_df(|| Ok(self.df.read().clear()))
    }

    /// Export the columns via polars-ffi
    /// # Safety
    /// Needs a preallocated *mut SeriesExport that has allocated space for n_columns.
    pub unsafe fn _export_columns(&self, location: usize) {
        use polars_ffi::version_0::export_column;

        let df = self.df.read();
        let cols = df.columns();

        let location = location as *mut SeriesExport;

        for (i, col) in cols.iter().enumerate() {
            let e = export_column(col);
            // SAFETY:
            // Caller should ensure address is allocated.
            // Be careful not to drop `e` here as that should be dropped by the ffi consumer
            unsafe { core::ptr::write(location.add(i), e) };
        }
    }

    /// Import [`Self`] via polars-ffi
    /// # Safety
    /// [`location`] should be an address that contains [`width`] properly initialized
    /// [`SeriesExport`]s
    #[classmethod]
    pub unsafe fn _import_columns(
        _cls: &Bound<PyType>,
        location: usize,
        width: usize,
    ) -> PyResult<Self> {
        use polars_ffi::version_0::import_df;

        let location = location as *mut SeriesExport;

        let df = unsafe { import_df(location, width) }.map_err(PyPolarsErr::from)?;
        Ok(PyDataFrame::from(df))
    }

    /// Internal utility function to allow direct access to the row encoding from python.
    #[pyo3(signature = (opts))]
    fn _row_encode(&self, py: Python<'_>, opts: Vec<(bool, bool, bool)>) -> PyResult<PySeries> {
        py.enter_polars_series(|| {
            let name = PlSmallStr::from_static("row_enc");
            let is_unordered = opts.first().is_some_and(|(_, _, v)| *v);

            let ca = if is_unordered {
                _get_rows_encoded_ca_unordered(name, self.df.read().columns())
            } else {
                let descending = opts.iter().map(|(v, _, _)| *v).collect::<Vec<_>>();
                let nulls_last = opts.iter().map(|(_, v, _)| *v).collect::<Vec<_>>();

                _get_rows_encoded_ca(
                    name,
                    self.df.read().columns(),
                    descending.as_slice(),
                    nulls_last.as_slice(),
                    false,
                )
            }?;

            Ok(ca)
        })
    }
}
