/*
 * SPDX-FileCopyrightText: Copyright (c) 2024-2026, NVIDIA CORPORATION.
 * SPDX-License-Identifier: Apache-2.0
 */

use crate::distance_type::DistanceType;
use crate::error::{check_cuvs, Result};
use std::fmt;
use std::io::{stderr, Write};

pub use ffi::cuvsIvfPqCodebookGen;
pub use ffi::cuvsIvfPqListLayout;

pub struct IndexParams(pub ffi::cuvsIvfPqIndexParams_t);

impl IndexParams {
    /// Returns a new IndexParams
    pub fn new() -> Result<IndexParams> {
        unsafe {
            let mut params = std::mem::MaybeUninit::<ffi::cuvsIvfPqIndexParams_t>::uninit();
            check_cuvs(ffi::cuvsIvfPqIndexParamsCreate(params.as_mut_ptr()))?;
            Ok(IndexParams(params.assume_init()))
        }
    }

    /// The number of clusters used in the coarse quantizer.
    pub fn set_n_lists(self, n_lists: u32) -> IndexParams {
        unsafe {
            (*self.0).n_lists = n_lists;
        }
        self
    }

    /// DistanceType to use for building the index
    pub fn set_metric(self, metric: DistanceType) -> IndexParams {
        unsafe {
            (*self.0).metric = metric;
        }
        self
    }

    /// The number of iterations searching for kmeans centers during index building.
    pub fn set_metric_arg(self, metric_arg: f32) -> IndexParams {
        unsafe {
            (*self.0).metric_arg = metric_arg;
        }
        self
    }

    /// The number of iterations searching for kmeans centers during index building.
    pub fn set_kmeans_n_iters(self, kmeans_n_iters: u32) -> IndexParams {
        unsafe {
            (*self.0).kmeans_n_iters = kmeans_n_iters;
        }
        self
    }

    /// If kmeans_trainset_fraction is less than 1, then the dataset is
    /// subsampled, and only n_samples * kmeans_trainset_fraction rows
    /// are used for training.
    pub fn set_kmeans_trainset_fraction(self, kmeans_trainset_fraction: f64) -> IndexParams {
        unsafe {
            (*self.0).kmeans_trainset_fraction = kmeans_trainset_fraction;
        }
        self
    }

    /// The bit length of the vector element after quantization.
    pub fn set_pq_bits(self, pq_bits: u32) -> IndexParams {
        unsafe {
            (*self.0).pq_bits = pq_bits;
        }
        self
    }

    /// The dimensionality of a the vector after product quantization.
    /// When zero, an optimal value is selected using a heuristic. Note
    /// pq_dim * pq_bits must be a multiple of 8. Hint: a smaller 'pq_dim'
    /// results in a smaller index size and better search performance, but
    /// lower recall. If 'pq_bits' is 8, 'pq_dim' can be set to any number,
    /// but multiple of 8 are desirable for good performance. If 'pq_bits'
    /// is not 8, 'pq_dim' should be a multiple of 8. For good performance,
    /// it is desirable that 'pq_dim' is a multiple of 32. Ideally,
    /// 'pq_dim' should be also a divisor of the dataset dim.
    pub fn set_pq_dim(self, pq_dim: u32) -> IndexParams {
        unsafe {
            (*self.0).pq_dim = pq_dim;
        }
        self
    }

    pub fn set_codebook_kind(self, codebook_kind: cuvsIvfPqCodebookGen) -> IndexParams {
        unsafe {
            (*self.0).codebook_kind = codebook_kind;
        }
        self
    }

    /// Memory layout of the IVF-PQ list data.
    /// - FLAT: Codes are stored contiguously, one vector's codes after another.
    /// - INTERLEAVED: Codes are interleaved for optimized search performance.
    ///   This is the default and recommended for search workloads.
    pub fn set_codes_layout(self, codes_layout: cuvsIvfPqListLayout) -> IndexParams {
        unsafe {
            (*self.0).codes_layout = codes_layout;
        }
        self
    }

    /// Apply a random rotation matrix on the input data and queries even
    /// if `dim % pq_dim == 0`. Note: if `dim` is not multiple of `pq_dim`,
    /// a random rotation is always applied to the input data and queries
    /// to transform the working space from `dim` to `rot_dim`, which may
    /// be slightly larger than the original space and and is a multiple
    /// of `pq_dim` (`rot_dim % pq_dim == 0`). However, this transform is
    /// not necessary when `dim` is multiple of `pq_dim` (`dim == rot_dim`,
    /// hence no need in adding "extra" data columns / features). By
    /// default, if `dim == rot_dim`, the rotation transform is
    /// initialized with the identity matrix. When
    /// `force_random_rotation == True`, a random orthogonal transform
    pub fn set_force_random_rotation(self, force_random_rotation: bool) -> IndexParams {
        unsafe {
            (*self.0).force_random_rotation = force_random_rotation;
        }
        self
    }

    /// The max number of data points to use per PQ code during PQ codebook training. Using more data
    /// points per PQ code may increase the quality of PQ codebook but may also increase the build
    /// time. The parameter is applied to both PQ codebook generation methods, i.e., PER_SUBSPACE and
    /// PER_CLUSTER. In both cases, we will use `pq_book_size * max_train_points_per_pq_code` training
    /// points to train each codebook.
    pub fn set_max_train_points_per_pq_code(self, max_pq_points: u32) -> IndexParams {
        unsafe {
            (*self.0).max_train_points_per_pq_code = max_pq_points;
        }
        self
    }

    /// After training the coarse and fine quantizers, we will populate
    /// the index with the dataset if add_data_on_build == true, otherwise
    /// the index is left empty, and the extend method can be used
    /// to add new vectors to the index.
    pub fn set_add_data_on_build(self, add_data_on_build: bool) -> IndexParams {
        unsafe {
            (*self.0).add_data_on_build = add_data_on_build;
        }
        self
    }
}

impl fmt::Debug for IndexParams {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        // custom debug trait here, default value will show the pointer address
        // for the inner params object which isn't that useful.
        write!(f, "IndexParams({:?})", unsafe { *self.0 })
    }
}

impl Drop for IndexParams {
    fn drop(&mut self) {
        if let Err(e) = check_cuvs(unsafe { ffi::cuvsIvfPqIndexParamsDestroy(self.0) }) {
            write!(
                stderr(),
                "failed to call cuvsIvfPqIndexParamsDestroy {:?}",
                e
            )
            .expect("failed to write to stderr");
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_index_params() {
        let params = IndexParams::new()
            .unwrap()
            .set_n_lists(128)
            .set_add_data_on_build(false);

        unsafe {
            assert_eq!((*params.0).n_lists, 128);
            assert_eq!((*params.0).add_data_on_build, false);
        }
    }
}
