/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

// -*- c++ -*-

#ifndef FAISS_INDEX_IVF_FLAT_H
#define FAISS_INDEX_IVF_FLAT_H

#include <stdint.h>
#include <unordered_map>

#include <faiss/IndexIVF.h>

namespace faiss {

/** Inverted file with stored vectors. Here the inverted file
 * pre-selects the vectors to be searched, but they are not otherwise
 * encoded, the code array just contains the raw float entries.
 */
struct IndexIVFFlat : IndexIVF {
    IndexIVFFlat(
            Index* quantizer,
            size_t d,
            size_t nlist_,
            MetricType = METRIC_L2,
            bool own_invlists = true);

    void add_core(
            idx_t n,
            const float* x,
            const idx_t* xids,
            const idx_t* precomputed_idx,
            void* inverted_list_context = nullptr) override;

    void encode_vectors(
            idx_t n,
            const float* x,
            const idx_t* list_nos,
            uint8_t* codes,
            bool include_listnos = false) const override;

    void decode_vectors(
            idx_t n,
            const uint8_t* codes,
            const idx_t* list_nos,
            float* x) const override;

    InvertedListScanner* get_InvertedListScanner(
            bool store_pairs,
            const IDSelector* sel,
            const IVFSearchParameters* params) const override;

    void reconstruct_from_offset(int64_t list_no, int64_t offset, float* recons)
            const override;

    void sa_decode(idx_t n, const uint8_t* bytes, float* x) const override;

    IndexIVFFlat();
};

template <typename VectorDistance>
struct IVFFlatScanner : InvertedListScanner {
    VectorDistance vd;
    using C = typename VectorDistance::C;

    IVFFlatScanner(
            const VectorDistance& vd,
            bool store_pairs,
            const IDSelector* sel)
            : InvertedListScanner(store_pairs, sel), vd(vd) {
        keep_max = vd.is_similarity;
        code_size = vd.d * sizeof(float);
    }

    const float* xi = nullptr;
    void set_query(const float* query) override {
        this->xi = query;
    }

    void set_list(idx_t list_no, float /* coarse_dis */) override {
        this->list_no = list_no;
    }

    float distance_to_code(const uint8_t* code) const final;

    size_t scan_codes(
            size_t list_size,
            const uint8_t* codes,
            const idx_t* ids,
            ResultHandler& handler) const override;
};

struct IndexIVFFlatDedup : IndexIVFFlat {
    /** Maps ids stored in the index to the ids of vectors that are
     *  the same. When a vector is unique, it does not appear in the
     *  instances map */
    std::unordered_multimap<idx_t, idx_t> instances;

    IndexIVFFlatDedup(
            Index* quantizer,
            size_t d,
            size_t nlist_,
            MetricType = METRIC_L2,
            bool own_invlists = true);

    /// also dedups the training set
    void train(idx_t n, const float* x) override;

    /// implemented for all IndexIVF* classes
    void add_with_ids(idx_t n, const float* x, const idx_t* xids) override;

    void search_preassigned(
            idx_t n,
            const float* x,
            idx_t k,
            const idx_t* assign,
            const float* centroid_dis,
            float* distances,
            idx_t* labels,
            bool store_pairs,
            const IVFSearchParameters* params = nullptr,
            IndexIVFStats* stats = nullptr) const override;

    size_t remove_ids(const IDSelector& sel) override;

    /// not implemented
    void range_search(
            idx_t n,
            const float* x,
            float radius,
            RangeSearchResult* result,
            const SearchParameters* params = nullptr) const override;

    /// not implemented
    void update_vectors(int nv, const idx_t* idx, const float* v) override;

    /// not implemented
    void reconstruct_from_offset(int64_t list_no, int64_t offset, float* recons)
            const override;

    IndexIVFFlatDedup() {}
};

} // namespace faiss

#endif
