// SPDX-License-Identifier: Apache-2.0
// SPDX-FileCopyrightText: Copyright The LanceDB Authors

use lancedb::index::vector::IvfFlatIndexBuilder;
use lancedb::index::{
    scalar::{BTreeIndexBuilder, FtsIndexBuilder},
    vector::{IvfHnswPqIndexBuilder, IvfHnswSqIndexBuilder, IvfPqIndexBuilder},
    Index as LanceDbIndex,
};
use pyo3::types::PyStringMethods;
use pyo3::IntoPyObject;
use pyo3::{
    exceptions::{PyKeyError, PyValueError},
    intern, pyclass, pymethods,
    types::PyAnyMethods,
    Bound, FromPyObject, PyAny, PyResult, Python,
};

use crate::util::parse_distance_type;

pub fn class_name(ob: &'_ Bound<'_, PyAny>) -> PyResult<String> {
    let full_name = ob
        .getattr(intern!(ob.py(), "__class__"))?
        .getattr(intern!(ob.py(), "__name__"))?;
    let full_name = full_name.downcast()?.to_string_lossy();

    match full_name.rsplit_once('.') {
        Some((_, name)) => Ok(name.to_string()),
        None => Ok(full_name.to_string()),
    }
}

pub fn extract_index_params(source: &Option<Bound<'_, PyAny>>) -> PyResult<LanceDbIndex> {
    if let Some(source) = source {
        match class_name(source)?.as_str() {
            "BTree" => Ok(LanceDbIndex::BTree(BTreeIndexBuilder::default())),
            "Bitmap" => Ok(LanceDbIndex::Bitmap(Default::default())),
            "LabelList" => Ok(LanceDbIndex::LabelList(Default::default())),
            "FTS" => {
                let params = source.extract::<FtsParams>()?;
                let inner_opts = FtsIndexBuilder::default()
                    .base_tokenizer(params.base_tokenizer)
                    .language(&params.language)
                    .map_err(|_| PyValueError::new_err(format!("LanceDB does not support the requested language: '{}'", params.language)))?
                    .with_position(params.with_position)
                    .lower_case(params.lower_case)
                    .max_token_length(params.max_token_length)
                    .remove_stop_words(params.remove_stop_words)
                    .stem(params.stem)
                    .ascii_folding(params.ascii_folding);
                Ok(LanceDbIndex::FTS(inner_opts))
            },
            "IvfFlat" => {
                let params = source.extract::<IvfFlatParams>()?;
                let distance_type = parse_distance_type(params.distance_type)?;
                let mut ivf_flat_builder = IvfFlatIndexBuilder::default()
                    .distance_type(distance_type)
                    .max_iterations(params.max_iterations)
                    .sample_rate(params.sample_rate);
                if let Some(num_partitions) = params.num_partitions {
                    ivf_flat_builder = ivf_flat_builder.num_partitions(num_partitions);
                }
                Ok(LanceDbIndex::IvfFlat(ivf_flat_builder))
            },
            "IvfPq" => {
                let params = source.extract::<IvfPqParams>()?;
                let distance_type = parse_distance_type(params.distance_type)?;
                let mut ivf_pq_builder = IvfPqIndexBuilder::default()
                    .distance_type(distance_type)
                    .max_iterations(params.max_iterations)
                    .sample_rate(params.sample_rate)
                    .num_bits(params.num_bits);
                if let Some(num_partitions) = params.num_partitions {
                    ivf_pq_builder = ivf_pq_builder.num_partitions(num_partitions);
                }
                if let Some(num_sub_vectors) = params.num_sub_vectors {
                    ivf_pq_builder = ivf_pq_builder.num_sub_vectors(num_sub_vectors);
                }
                Ok(LanceDbIndex::IvfPq(ivf_pq_builder))
            },
            "HnswPq" => {
                let params = source.extract::<IvfHnswPqParams>()?;
                let distance_type = parse_distance_type(params.distance_type)?;
                let mut hnsw_pq_builder = IvfHnswPqIndexBuilder::default()
                    .distance_type(distance_type)
                    .max_iterations(params.max_iterations)
                    .sample_rate(params.sample_rate)
                    .num_edges(params.m)
                    .ef_construction(params.ef_construction)
                    .num_bits(params.num_bits);
                if let Some(num_partitions) = params.num_partitions {
                    hnsw_pq_builder = hnsw_pq_builder.num_partitions(num_partitions);
                }
                if let Some(num_sub_vectors) = params.num_sub_vectors {
                    hnsw_pq_builder = hnsw_pq_builder.num_sub_vectors(num_sub_vectors);
                }
                Ok(LanceDbIndex::IvfHnswPq(hnsw_pq_builder))
            },
            "HnswSq" => {
                let params = source.extract::<IvfHnswSqParams>()?;
                let distance_type = parse_distance_type(params.distance_type)?;
                let mut hnsw_sq_builder = IvfHnswSqIndexBuilder::default()
                    .distance_type(distance_type)
                    .max_iterations(params.max_iterations)
                    .sample_rate(params.sample_rate)
                    .num_edges(params.m)
                    .ef_construction(params.ef_construction);
                if let Some(num_partitions) = params.num_partitions {
                    hnsw_sq_builder = hnsw_sq_builder.num_partitions(num_partitions);
                }
                Ok(LanceDbIndex::IvfHnswSq(hnsw_sq_builder))
            },
            not_supported => Err(PyValueError::new_err(format!(
                "Invalid index type '{}'.  Must be one of BTree, Bitmap, LabelList, FTS, IvfPq, IvfHnswPq, or IvfHnswSq",
                not_supported
            ))),
        }
    } else {
        Ok(LanceDbIndex::Auto)
    }
}

#[derive(FromPyObject)]
struct FtsParams {
    with_position: bool,
    base_tokenizer: String,
    language: String,
    max_token_length: Option<usize>,
    lower_case: bool,
    stem: bool,
    remove_stop_words: bool,
    ascii_folding: bool,
}

#[derive(FromPyObject)]
struct IvfFlatParams {
    distance_type: String,
    num_partitions: Option<u32>,
    max_iterations: u32,
    sample_rate: u32,
}

#[derive(FromPyObject)]
struct IvfPqParams {
    distance_type: String,
    num_partitions: Option<u32>,
    num_sub_vectors: Option<u32>,
    num_bits: u32,
    max_iterations: u32,
    sample_rate: u32,
}

#[derive(FromPyObject)]
struct IvfHnswPqParams {
    distance_type: String,
    num_partitions: Option<u32>,
    num_sub_vectors: Option<u32>,
    num_bits: u32,
    max_iterations: u32,
    sample_rate: u32,
    m: u32,
    ef_construction: u32,
}

#[derive(FromPyObject)]
struct IvfHnswSqParams {
    distance_type: String,
    num_partitions: Option<u32>,
    max_iterations: u32,
    sample_rate: u32,
    m: u32,
    ef_construction: u32,
}

#[pyclass(get_all)]
/// A description of an index currently configured on a column
pub struct IndexConfig {
    /// The type of the index
    pub index_type: String,
    /// The columns in the index
    ///
    /// Currently this is always a list of size 1.  In the future there may
    /// be more columns to represent composite indices.
    pub columns: Vec<String>,
    /// Name of the index.
    pub name: String,
}

#[pymethods]
impl IndexConfig {
    pub fn __repr__(&self) -> String {
        format!(
            "Index({}, columns={:?}, name=\"{}\")",
            self.index_type, self.columns, self.name
        )
    }

    // For backwards-compatibility with the old sync SDK, we also support getting
    // attributes via __getitem__.
    pub fn __getitem__<'a>(&self, key: String, py: Python<'a>) -> PyResult<Bound<'a, PyAny>> {
        match key.as_str() {
            "index_type" => Ok(self.index_type.clone().into_pyobject(py)?.into_any()),
            "columns" => Ok(self.columns.clone().into_pyobject(py)?.into_any()),
            "name" | "index_name" => Ok(self.name.clone().into_pyobject(py)?.into_any()),
            _ => Err(PyKeyError::new_err(format!("Invalid key: {}", key))),
        }
    }
}

impl From<lancedb::index::IndexConfig> for IndexConfig {
    fn from(value: lancedb::index::IndexConfig) -> Self {
        let index_type = format!("{:?}", value.index_type);
        Self {
            index_type,
            columns: value.columns,
            name: value.name,
        }
    }
}