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// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
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//
//   http://www.apache.org/licenses/LICENSE-2.0
//
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//! Utilities to assist with reading and writing Arrow data as Flight messages

use crate::{FlightData, SchemaAsIpc};
use std::collections::HashMap;
use std::sync::Arc;

use arrow_array::{ArrayRef, RecordBatch};
use arrow_buffer::Buffer;
use arrow_ipc::convert::fb_to_schema;
use arrow_ipc::writer::CompressionContext;
use arrow_ipc::{reader, root_as_message, writer, writer::IpcWriteOptions};
use arrow_schema::{ArrowError, Schema, SchemaRef};

/// Convert a slice of wire protocol `FlightData`s into a vector of `RecordBatch`es
pub fn flight_data_to_batches(flight_data: &[FlightData]) -> Result<Vec<RecordBatch>, ArrowError> {
    let schema = flight_data.first().ok_or_else(|| {
        ArrowError::CastError("Need at least one FlightData for schema".to_string())
    })?;
    let message = root_as_message(&schema.data_header[..])
        .map_err(|_| ArrowError::CastError("Cannot get root as message".to_string()))?;

    let ipc_schema: arrow_ipc::Schema = message
        .header_as_schema()
        .ok_or_else(|| ArrowError::CastError("Cannot get header as Schema".to_string()))?;
    let schema = fb_to_schema(ipc_schema);
    let schema = Arc::new(schema);

    let mut batches = vec![];
    let dictionaries_by_id = HashMap::new();
    for datum in flight_data[1..].iter() {
        let batch = flight_data_to_arrow_batch(datum, schema.clone(), &dictionaries_by_id)?;
        batches.push(batch);
    }
    Ok(batches)
}

/// Convert `FlightData` (with supplied schema and dictionaries) to an arrow `RecordBatch`.
pub fn flight_data_to_arrow_batch(
    data: &FlightData,
    schema: SchemaRef,
    dictionaries_by_id: &HashMap<i64, ArrayRef>,
) -> Result<RecordBatch, ArrowError> {
    // check that the data_header is a record batch message
    let message = arrow_ipc::root_as_message(&data.data_header[..])
        .map_err(|err| ArrowError::ParseError(format!("Unable to get root as message: {err:?}")))?;

    message
        .header_as_record_batch()
        .ok_or_else(|| {
            ArrowError::ParseError(
                "Unable to convert flight data header to a record batch".to_string(),
            )
        })
        .map(|batch| {
            reader::read_record_batch(
                &Buffer::from(data.data_body.as_ref()),
                batch,
                schema,
                dictionaries_by_id,
                None,
                &message.version(),
            )
        })?
}

/// Convert `RecordBatch`es to wire protocol `FlightData`s
pub fn batches_to_flight_data(
    schema: &Schema,
    batches: Vec<RecordBatch>,
) -> Result<Vec<FlightData>, ArrowError> {
    let options = IpcWriteOptions::default();
    let schema_flight_data: FlightData = SchemaAsIpc::new(schema, &options).into();
    let mut dictionaries = vec![];
    let mut flight_data = vec![];

    let data_gen = writer::IpcDataGenerator::default();
    let mut dictionary_tracker = writer::DictionaryTracker::new(false);
    let mut compression_context = CompressionContext::default();

    for batch in batches.iter() {
        let (encoded_dictionaries, encoded_batch) = data_gen.encode(
            batch,
            &mut dictionary_tracker,
            &options,
            &mut compression_context,
        )?;

        dictionaries.extend(encoded_dictionaries.into_iter().map(Into::into));
        flight_data.push(encoded_batch.into());
    }

    let mut stream = Vec::with_capacity(1 + dictionaries.len() + flight_data.len());

    stream.push(schema_flight_data);
    stream.extend(dictionaries);
    stream.extend(flight_data);
    let flight_data = stream;
    Ok(flight_data)
}
