/**
 * 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.
 */

/**
 * File format description for the parquet file format
 */
namespace cpp parquet
namespace java parquet.format

/**
 * Types supported by Parquet.  These types are intended to be used in combination
 * with the encodings to control the on disk storage format.
 * For example INT16 is not included as a type since a good encoding of INT32
 * would handle this.
 */
enum Type {
  BOOLEAN = 0;
  INT32 = 1;
  INT64 = 2;
  INT96 = 3;
  FLOAT = 4;
  DOUBLE = 5;
  BYTE_ARRAY = 6;
  FIXED_LEN_BYTE_ARRAY = 7;
}

/**
 * Common types used by frameworks(e.g. hive, pig) using parquet.  This helps map
 * between types in those frameworks to the base types in parquet.  This is only
 * metadata and not needed to read or write the data.
 */
enum ConvertedType {
  /** a BYTE_ARRAY actually contains UTF8 encoded chars */
  UTF8 = 0;

  /** a map is converted as an optional field containing a repeated key/value pair */
  MAP = 1;

  /** a key/value pair is converted into a group of two fields */
  MAP_KEY_VALUE = 2;

  /** a list is converted into an optional field containing a repeated field for its 
   * values */
  LIST = 3;

  /** an enum is converted into a binary field */
  ENUM = 4;
}

/** 
 * Representation of Schemas
 */
enum FieldRepetitionType {
  /** This field is required (can not be null) and each record has exactly 1 value. */
  REQUIRED = 0;

  /** The field is optional (can be null) and each record has 0 or 1 values. */
  OPTIONAL = 1;

  /** The field is repeated and can contain 0 or more values */
  REPEATED = 2;
}

/**
 * Represents a element inside a schema definition.
 *  - if it is a group (inner node) then type is undefined and num_children is defined
 *  - if it is a primitive type (leaf) then type is defined and num_children is undefined
 * the nodes are listed in depth first traversal order.
 */
struct SchemaElement {
  /** Data type for this field. Not set if the current element is a non-leaf node */
  1: optional Type type;

  /** If type is FIXED_LEN_BYTE_ARRAY, this is the byte length of the vales.
   * Otherwise, if specified, this is the maximum bit length to store any of the values.
   * (e.g. a low cardinality INT col could have this set to 3).  Note that this is
   * in the schema, and therefore fixed for the entire file.
   */
  2: optional i32 type_length;

  /** repetition of the field. The root of the schema does not have a repetition_type.
   * All other nodes must have one */
  3: optional FieldRepetitionType repetition_type;

  /** Name of the field in the schema */
  4: required string name;

  /** Nested fields.  Since thrift does not support nested fields,
   * the nesting is flattened to a single list by a depth-first traversal.
   * The children count is used to construct the nested relationship.
   * This field is not set when the element is a primitive type
   */
  5: optional i32 num_children;

  /** When the schema is the result of a conversion from another model
   * Used to record the original type to help with cross conversion.
   */
  6: optional ConvertedType converted_type;
}

/**
 * Encodings supported by Parquet.  Not all encodings are valid for all types.  These
 * enums are also used to specify the encoding of definition and repetition levels.
 * See the accompanying doc for the details of the more complicated encodings.
 */
enum Encoding {
  /** Default encoding.
   * BOOLEAN - 1 bit per value. 0 is false; 1 is true.
   * INT32 - 4 bytes per value.  Stored as little-endian.
   * INT64 - 8 bytes per value.  Stored as little-endian.
   * FLOAT - 4 bytes per value.  IEEE. Stored as little-endian.
   * DOUBLE - 8 bytes per value.  IEEE. Stored as little-endian.
   * BYTE_ARRAY - 4 byte length stored as little endian, followed by bytes.  
   * FIXED_LEN_BYTE_ARRAY - Just the bytes.
   */
  PLAIN = 0;

  /** Group VarInt encoding for INT32/INT64. */
  GROUP_VAR_INT = 1;

  /** Dictionary encoding. The values in the dictionary are encoded in the 
   * plain type. 
   */
  PLAIN_DICTIONARY = 2;

  /** Group packed run length encoding. Usable for definition/reptition levels
   * encoding */
  RLE = 3;

  /** Bit packed encoding.  This can only be used if the data has a known max
   * width.  Usable for definition/repetition levels encoding.  **/
  BIT_PACKED = 4;

  /** Delta encoding for integers. This can be used for int columns and works best 
   * on sorted data */
  DELTA_BINARY_PACKED = 5;
}

/**
 * Supported compression algorithms.  
 */
enum CompressionCodec {
  UNCOMPRESSED = 0;
  SNAPPY = 1;
  GZIP = 2;
  LZO = 3;
}

enum PageType {
  DATA_PAGE = 0;
  INDEX_PAGE = 1;
  DICTIONARY_PAGE = 2;
}

/** Data page header */
struct DataPageHeader {
  /** Number of values, including NULLs, in this data page. **/
  1: required i32 num_values

  /** Encoding used for this data page **/
  2: required Encoding encoding

  /** Encoding used for definition levels **/
  3: required Encoding definition_level_encoding;

  /** Encoding used for repetition levels **/
  4: required Encoding repetition_level_encoding;
}

struct IndexPageHeader {
  /** TODO: **/
}

struct DictionaryPageHeader {
  /** Number of values in the dictionary **/
  1: required i32 num_values;

  /** Encoding using this dictionary page **/
  2: required Encoding encoding
}

struct PageHeader {
  /** the type of the page: indicates which of the *_header fields is set **/
  1: required PageType type

  /** Uncompressed page size in bytes (not including this header) **/
  2: required i32 uncompressed_page_size

  /** Compressed page size in bytes (not including this header) **/
  3: required i32 compressed_page_size

  /** 32bit crc for the data below. This allows for disabling checksumming in HDFS
   *  if only a few pages needs to be read 
   **/
  4: optional i32 crc

  // Headers for page specific data.  One only will be set.
  5: optional DataPageHeader data_page_header;
  6: optional IndexPageHeader index_page_header;
  7: optional DictionaryPageHeader dictionary_page_header;
}

/** 
 * Wrapper struct to store key values
 */
 struct KeyValue {
  1: required string key
  2: optional string value
}

/**
 * Wrapper struct to specify sort order
 */
struct SortingColumn {
  /** The column index (in this row group) **/
  1: required i32 column_idx

  /** If true, indicates this column is sorted in descending order. **/
  2: required bool descending

  /** If true, nulls will come before non-null values, otherwise,
   * nulls go at the end. */
  3: required bool nulls_first
}

/**
 * Description for column metadata
 */
struct ColumnMetaData {
  /** Type of this column **/
  1: required Type type

  /** Set of all encodings used for this column. The purpose is to validate 
   * whether we can decode those pages. **/
  2: required list<Encoding> encodings

  /** Path in schema **/
  3: required list<string> path_in_schema

  /** Compression codec **/
  4: required CompressionCodec codec

  /** Number of values in this column **/
  5: required i64 num_values

  /** total byte size of all uncompressed pages in this column chunk (including the headers) **/
  6: required i64 total_uncompressed_size

  /** total byte size of all compressed pages in this column chunk (including the headers) **/
  7: required i64 total_compressed_size

  /** Optional key/value metadata **/
  8: optional list<KeyValue> key_value_metadata

  /** Byte offset from beginning of file to first data page **/
  9: required i64 data_page_offset

  /** Byte offset from beginning of file to root index page **/
  10: optional i64 index_page_offset

  /** Byte offset from the beginning of file to first (only) dictionary page **/
  11: optional i64 dictionary_page_offset
}

struct ColumnChunk {
  /** File where column data is stored.  If not set, assumed to be same file as 
    * metadata.  This path is relative to the current file.
    **/
  1: optional string file_path

  /** Byte offset in file_path to the ColumnMetaData **/
  2: required i64 file_offset

  /** Column metadata for this chunk. This is the same content as what is at
   * file_path/file_offset.  Having it here has it replicated in the file
   * metadata. 
   **/
  3: optional ColumnMetaData meta_data
}
  
struct RowGroup {
  1: required list<ColumnChunk> columns

  /** Total byte size of all the uncompressed column data in this row group **/
  2: required i64 total_byte_size

  /** Number of rows in this row group **/
  3: required i64 num_rows

  /** If set, specifies a sort ordering of the rows in this RowGroup.
   * The sorting columns can be a subset of all the columns.
   */
  4: optional list<SortingColumn> sorting_columns
}

/**
 * Description for file metadata
 */
struct FileMetaData {
  /** Version of this file **/
  1: required i32 version

  /** Parquet schema for this file.  This schema contains metadata for all the columns.
   * The schema is represented as a tree with a single root.  The nodes of the tree
   * are flattened to a list by doing a depth-first traversal.
   * The column metadata contains the path in the schema for that column which can be
   * used to map columns to nodes in the schema.
   * The first element is the root **/
  2: required list<SchemaElement> schema;

  /** Number of rows in this file **/
  3: required i64 num_rows

  /** Row groups in this file **/
  4: required list<RowGroup> row_groups

  /** Optional key/value metadata **/
  5: optional list<KeyValue> key_value_metadata

  /** String for application that wrote this file.  This should be in the format
   * <Application> version <App Version> (build <App Build Hash>).  
   * e.g. impala version 1.0 (build 6cf94d29b2b7115df4de2c06e2ab4326d721eb55)
   **/
  6: optional string created_by
}