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// Copyright 2023 Lance Developers.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Build IVF model

use std::sync::Arc;

use arrow_array::{Array, FixedSizeListArray};
use snafu::{location, Location};

use lance_core::error::{Error, Result};

/// Parameters to build IVF partitions
#[derive(Debug, Clone)]
pub struct IvfBuildParams {
    /// Number of partitions to build.
    pub num_partitions: usize,

    // ---- kmeans parameters
    /// Max number of iterations to train kmeans.
    pub max_iters: usize,

    /// Use provided IVF centroids.
    pub centroids: Option<Arc<FixedSizeListArray>>,

    pub sample_rate: usize,

    pub precomputed_partitons_file: Option<String>,
}

impl Default for IvfBuildParams {
    fn default() -> Self {
        Self {
            num_partitions: 32,
            max_iters: 50,
            centroids: None,
            sample_rate: 256, // See faiss
            precomputed_partitons_file: None,
        }
    }
}

impl IvfBuildParams {
    /// Create a new instance of `IvfBuildParams`.
    pub fn new(num_partitions: usize) -> Self {
        Self {
            num_partitions,
            ..Default::default()
        }
    }

    /// Create a new instance of [`IvfBuildParams`] with centroids.
    pub fn try_with_centroids(
        num_partitions: usize,
        centroids: Arc<FixedSizeListArray>,
    ) -> Result<Self> {
        if num_partitions != centroids.len() {
            return Err(Error::Index {
                message: format!(
                    "IvfBuildParams::try_with_centroids: num_partitions {} != centroids.len() {}",
                    num_partitions,
                    centroids.len()
                ),
                location: location!(),
            });
        }
        Ok(Self {
            num_partitions,
            centroids: Some(centroids),
            ..Default::default()
        })
    }
}