/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

#ifndef READER_CHUNK_ALIGNED_READER_H
#define READER_CHUNK_ALIGNED_READER_H

#include "common/allocator/my_string.h"
#include "common/tsfile_common.h"
#include "compress/compressor.h"
#include "encoding/decoder.h"
#include "file/read_file.h"
#include "reader/filter/filter.h"
#include "reader/ichunk_reader.h"

#ifdef ENABLE_THREADS
namespace common {
class ThreadPool;
}
#endif

namespace storage {

// Page classification for chunk-level parallel decode.
enum class PagePassType { SKIP, FULL_PASS, BOUNDARY };

// Metadata collected per page during the chunk scan phase.
struct ChunkPageInfo {
    PagePassType pass_type = PagePassType::SKIP;
    // File offsets of compressed data for time and each value column.
    int64_t time_file_offset = 0;
    uint32_t time_compressed_size = 0;
    uint32_t time_uncompressed_size = 0;
    int32_t row_begin = 0;  // inclusive
    int32_t row_end = 0;    // exclusive
    std::vector<int64_t> value_file_offsets;
    std::vector<uint32_t> value_compressed_sizes;
    std::vector<uint32_t> value_uncompressed_sizes;
};

// Decoded state for one (column, page) slot.  Populated by chunk-level
// parallel decode; consumed by the scatter loop.
struct PageDecodedState {
    std::vector<uint8_t> notnull_bitmap;
    std::vector<char> predecoded_values;
    std::vector<common::String> predecoded_strings;
    common::PageArena predecode_pa;
    int32_t predecoded_count = 0;
    int32_t predecoded_read_pos = 0;
};

// Per-value-column state for multi-value AlignedChunkReader.
struct ValueColumnState {
    ChunkMeta* chunk_meta = nullptr;
    ChunkHeader chunk_header;
    Decoder* decoder = nullptr;
    Compressor* compressor = nullptr;
    common::ByteStream in_stream;  // raw data from file
    common::ByteStream in;         // decompressed data
    char* uncompressed_buf = nullptr;
    int32_t file_data_buf_size = 0;
    uint32_t chunk_visit_offset = 0;
    PageHeader cur_page_header;
    std::vector<uint8_t> notnull_bitmap;
    int32_t cur_value_index = -1;

    // Per-page decoded state for chunk-level parallel decode.
    std::vector<PageDecodedState> per_page_state;

    // Pre-decoded value buffer for the CURRENT page, filled by
    // decompress_and_parse_value_page when the dense-multi path predecodes
    // values in worker threads.  Consumed by multi_DECODE_TV_BATCH instead of
    // calling the decoder inline.  Holds nonnull values only.
    std::vector<char> pending_decoded_values;
    int32_t pending_decoded_count = 0;
    int32_t pending_decoded_cursor = 0;
    bool pending_decoded = false;
};

class AlignedChunkReader : public IChunkReader {
   public:
    AlignedChunkReader()
        : read_file_(nullptr),
          time_chunk_meta_(nullptr),
          value_chunk_meta_(nullptr),
          measurement_name_(),
          time_chunk_header_(),
          value_chunk_header_(),
          cur_time_page_header_(),
          cur_value_page_header_(),
          time_in_stream_(),
          value_in_stream_(),
          file_data_time_buf_size_(0),
          file_data_value_buf_size_(0),
          time_chunk_visit_offset_(0),
          value_chunk_visit_offset_(0),
          time_compressor_(nullptr),
          value_compressor_(nullptr),
          time_filter_(nullptr),
          time_decoder_(nullptr),
          value_decoder_(nullptr),
          time_in_(),
          value_in_(),
          time_uncompressed_buf_(nullptr),
          value_uncompressed_buf_(nullptr),
          cur_value_index(-1) {}
    int init(ReadFile* read_file, common::String m_name,
             common::TSDataType data_type, Filter* time_filter) override;
    void reset() override;
    void destroy() override;
    ~AlignedChunkReader() override = default;

    bool has_more_data() const override {
        if (multi_value_mode_) {
            return has_more_data_multi();
        }
        return prev_value_page_not_finish() || prev_time_page_not_finish() ||
               (value_chunk_visit_offset_ -
                    value_chunk_header_.serialized_size_ <
                value_chunk_header_.data_size_) ||
               (time_chunk_visit_offset_ - time_chunk_header_.serialized_size_ <
                time_chunk_header_.data_size_);
    }
    ChunkHeader& get_chunk_header() override { return value_chunk_header_; }
    int load_by_aligned_meta(ChunkMeta* time_meta,
                             ChunkMeta* value_meta) override;

    // Multi-value: load one time chunk + N value chunks.
    int load_by_aligned_meta_multi(ChunkMeta* time_meta,
                                   const std::vector<ChunkMeta*>& value_metas);

    int get_next_page(common::TsBlock* tsblock, Filter* oneshoot_filter,
                      common::PageArena& pa) override;
    int get_next_page(common::TsBlock* tsblock, Filter* oneshoot_filter,
                      common::PageArena& pa, int64_t min_time_hint,
                      int& row_offset, int& row_limit) override;

    // Multi-value: get the number of value columns.
    uint32_t get_value_column_count() const {
        return multi_value_mode_ ? value_columns_.size() : 1;
    }

    // Multi-value: get chunk header for a specific value column.
    ChunkHeader& get_value_chunk_header(uint32_t col) {
        if (multi_value_mode_ && col < value_columns_.size()) {
            return value_columns_[col]->chunk_header;
        }
        return value_chunk_header_;
    }

    bool is_multi_value_mode() const { return multi_value_mode_; }

#ifdef ENABLE_THREADS
    // Set external thread pool for parallel decode (not owned).
    void set_decode_pool(common::ThreadPool* pool) { decode_pool_ = pool; }
#endif

   private:
    bool should_skip_page_by_time(int64_t min_time_hint);
    bool should_skip_page_by_offset(int& row_offset);
    FORCE_INLINE bool chunk_has_only_one_page(
        const ChunkHeader& chunk_header) const {
        return (chunk_header.chunk_type_ & ONLY_ONE_PAGE_CHUNK_HEADER_MARKER) ==
               ONLY_ONE_PAGE_CHUNK_HEADER_MARKER;
    }
    int alloc_compressor_and_decoder(storage::Decoder*& decoder,
                                     storage::Compressor*& compressor,
                                     common::TSEncoding encoding,
                                     common::TSDataType data_type,
                                     common::CompressionType compression_type);
    int get_cur_page_header(ChunkMeta*& chunk_meta,
                            common::ByteStream& in_stream_,
                            PageHeader& cur_page_header_,
                            uint32_t& chunk_visit_offset,
                            ChunkHeader& chunk_header,
                            int32_t* override_buf_size = nullptr);
    int read_from_file_and_rewrap(common::ByteStream& in_stream_,
                                  ChunkMeta*& chunk_meta,
                                  uint32_t& chunk_visit_offset,
                                  int32_t& file_data_buf_size,
                                  int want_size = 0, bool may_shrink = true);
    bool cur_page_statisify_filter(Filter* filter);
    int skip_cur_page();
    int decode_cur_time_page_data();
    int decode_cur_value_page_data();
    int decode_time_value_buf_into_tsblock(common::TsBlock*& ret_tsblock,
                                           Filter* filter,
                                           common::PageArena* pa);
    bool prev_time_page_not_finish() const {
        if (time_predecoded_) return page_time_cursor_ < page_time_count_;
        return (time_decoder_ && time_decoder_->has_remaining(time_in_)) ||
               time_in_.has_remaining();
    }

    bool prev_value_page_not_finish() const {
        return (value_decoder_ && value_decoder_->has_remaining(value_in_)) ||
               value_in_.has_remaining();
    }

    int decode_tv_buf_into_tsblock_by_datatype(common::ByteStream& time_in,
                                               common::ByteStream& value_in,
                                               common::TsBlock* ret_tsblock,
                                               Filter* filter,
                                               common::PageArena* pa);
    int i32_DECODE_TYPED_TV_INTO_TSBLOCK(common::ByteStream& time_in,
                                         common::ByteStream& value_in,
                                         common::RowAppender& row_appender,
                                         Filter* filter);
    // Unified fixed-width aligned time+value page decode for
    // INT32/INT64/FLOAT/DOUBLE.  Defined in the .cc; instantiated there for
    // each value type by decode_tv_buf_into_tsblock_by_datatype().
    template <typename T>
    int decode_tv_batch(common::ByteStream& time_in,
                        common::ByteStream& value_in,
                        common::RowAppender& row_appender, Filter* filter);
    int STRING_DECODE_TYPED_TV_INTO_TSBLOCK(common::ByteStream& time_in,
                                            common::ByteStream& value_in,
                                            common::RowAppender& row_appender,
                                            common::PageArena& pa,
                                            Filter* filter);

    // ── Multi-value private methods (page-level, serial fallback) ────────
    bool has_more_data_multi() const;
    bool prev_any_value_page_not_finish_multi() const;
    int get_next_page_multi(common::TsBlock* ret_tsblock,
                            Filter* oneshoot_filter, common::PageArena& pa);
    int get_next_page_multi_serial(common::TsBlock* ret_tsblock, Filter* filter,
                                   common::PageArena& pa);
    int skip_cur_page_multi();
    bool cur_page_statisify_filter_multi(Filter* filter);
    int decode_cur_value_pages_multi();
    int decode_cur_value_page_data_for(ValueColumnState& col);
    int ensure_value_page_loaded(ValueColumnState& col);
    static int decompress_and_parse_value_page(ValueColumnState& col,
                                               bool predecode);
    void predecode_all_timestamps();
    int decode_time_value_buf_into_tsblock_multi(common::TsBlock*& ret_tsblock,
                                                 Filter* filter,
                                                 common::PageArena* pa);
    int multi_DECODE_TV_BATCH(common::TsBlock* ret_tsblock,
                              common::RowAppender& row_appender, Filter* filter,
                              common::PageArena* pa);
    int build_page_plan(Filter* filter);
    int decode_time_page_direct(const ChunkPageInfo& page_info,
                                std::vector<int64_t>& out_times);
    int decode_time_page_with(const ChunkPageInfo& page_info,
                              std::vector<int64_t>& out_times, Decoder* decoder,
                              Compressor* compressor);
    int decode_all_planned_pages();
    int decode_value_page_for_slot(uint32_t col_idx, size_t page_idx);
    int decode_page_lazy(size_t page_idx);
    void release_page_slot(size_t page_idx);
    void release_current_page_state();
    bool has_variable_length_value_column() const;
    int count_non_null_prefix(const std::vector<uint8_t>& bitmap,
                              int32_t row_limit) const;

   private:
    ReadFile* read_file_;
    // ── Single-value mode fields (kept for backward compat) ──────────────
    ChunkMeta* time_chunk_meta_;
    ChunkMeta* value_chunk_meta_;
    common::String measurement_name_;
    ChunkHeader time_chunk_header_;
    ChunkHeader value_chunk_header_;
    PageHeader cur_time_page_header_;
    PageHeader cur_value_page_header_;

    common::ByteStream time_in_stream_;
    common::ByteStream value_in_stream_;
    int32_t file_data_time_buf_size_;
    int32_t file_data_value_buf_size_;
    uint32_t time_chunk_visit_offset_;
    uint32_t value_chunk_visit_offset_;

    Compressor* time_compressor_;
    Compressor* value_compressor_;
    Filter* time_filter_;

    Decoder* time_decoder_;
    Decoder* value_decoder_;
    common::ByteStream time_in_;
    common::ByteStream value_in_;
    char* time_uncompressed_buf_;
    char* value_uncompressed_buf_;
    std::vector<uint8_t> value_page_col_notnull_bitmap_;
    uint32_t value_page_data_num_;
    int32_t cur_value_index;

    // ── Multi-value mode fields ──────────────────────────────────────────
    bool multi_value_mode_ = false;
    std::vector<ValueColumnState*> value_columns_;

    // Pre-decoded timestamps for page-level parallel decode.
    std::vector<int64_t> page_all_times_;
    int page_time_count_ = 0;
    int page_time_cursor_ = 0;
    bool time_predecoded_ = false;

    // ── Page-plan state ────────────────────────────────────────────────
    std::vector<ChunkPageInfo> chunk_pages_;
    std::vector<std::vector<int64_t>> per_page_times_;
    bool page_plan_built_ = false;
    bool current_page_loaded_ = false;
    size_t current_page_plan_index_ = 0;

#ifdef ENABLE_THREADS
    common::ThreadPool* decode_pool_ = nullptr;  // borrowed, not owned
    // Per-worker time decoder + compressor pool for parallel time-page decode.
    // Sized to decode_pool_->num_threads() on first use, owned by this reader.
    std::vector<Decoder*> time_decoder_pool_;
    std::vector<Compressor*> time_compressor_pool_;
#endif
};

}  // end namespace storage
#endif  // READER_CHUNK_ALIGNED_READER_H