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// 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.

//! Execution plan for reading line-delimited Avro files

use std::any::Any;
use std::sync::Arc;

use crate::avro_to_arrow::Reader as AvroReader;

use datafusion_common::error::Result;
use datafusion_datasource::TableSchema;
use datafusion_datasource::file::FileSource;
use datafusion_datasource::file_scan_config::FileScanConfig;
use datafusion_datasource::file_stream::FileOpener;
use datafusion_datasource::projection::{ProjectionOpener, SplitProjection};
use datafusion_physical_expr_common::sort_expr::LexOrdering;
use datafusion_physical_plan::metrics::ExecutionPlanMetricsSet;
use datafusion_physical_plan::projection::ProjectionExprs;

use object_store::ObjectStore;

/// AvroSource holds the extra configuration that is necessary for opening avro files
#[derive(Clone)]
pub struct AvroSource {
    table_schema: TableSchema,
    batch_size: Option<usize>,
    projection: SplitProjection,
    metrics: ExecutionPlanMetricsSet,
}

impl AvroSource {
    /// Initialize an AvroSource with the provided schema
    pub fn new(table_schema: impl Into<TableSchema>) -> Self {
        let table_schema = table_schema.into();
        Self {
            projection: SplitProjection::unprojected(&table_schema),
            table_schema,
            batch_size: None,
            metrics: ExecutionPlanMetricsSet::new(),
        }
    }

    fn open<R: std::io::Read>(&self, reader: R) -> Result<AvroReader<'static, R>> {
        let file_schema = self.table_schema.file_schema();
        let projection = Some(
            self.projection
                .file_indices
                .iter()
                .map(|&idx| file_schema.field(idx).name().clone())
                .collect::<Vec<_>>(),
        );
        AvroReader::try_new(
            reader,
            &Arc::clone(self.table_schema.file_schema()),
            self.batch_size.expect("Batch size must set before open"),
            projection.as_ref(),
        )
    }
}

impl FileSource for AvroSource {
    fn create_file_opener(
        &self,
        object_store: Arc<dyn ObjectStore>,
        _base_config: &FileScanConfig,
        _partition: usize,
    ) -> Result<Arc<dyn FileOpener>> {
        let mut opener = Arc::new(private::AvroOpener {
            config: Arc::new(self.clone()),
            object_store,
        }) as Arc<dyn FileOpener>;
        opener = ProjectionOpener::try_new(
            self.projection.clone(),
            Arc::clone(&opener),
            self.table_schema.file_schema(),
        )?;
        Ok(opener)
    }

    fn as_any(&self) -> &dyn Any {
        self
    }

    fn table_schema(&self) -> &TableSchema {
        &self.table_schema
    }

    fn with_batch_size(&self, batch_size: usize) -> Arc<dyn FileSource> {
        let mut conf = self.clone();
        conf.batch_size = Some(batch_size);
        Arc::new(conf)
    }

    fn try_pushdown_projection(
        &self,
        projection: &ProjectionExprs,
    ) -> Result<Option<Arc<dyn FileSource>>> {
        let mut source = self.clone();
        let new_projection = self.projection.source.try_merge(projection)?;
        let split_projection =
            SplitProjection::new(self.table_schema.file_schema(), &new_projection);
        source.projection = split_projection;
        Ok(Some(Arc::new(source)))
    }

    fn projection(&self) -> Option<&ProjectionExprs> {
        Some(&self.projection.source)
    }

    fn metrics(&self) -> &ExecutionPlanMetricsSet {
        &self.metrics
    }

    fn file_type(&self) -> &str {
        "avro"
    }

    fn repartitioned(
        &self,
        _target_partitions: usize,
        _repartition_file_min_size: usize,
        _output_ordering: Option<LexOrdering>,
        _config: &FileScanConfig,
    ) -> Result<Option<FileScanConfig>> {
        Ok(None)
    }
}

mod private {
    use super::*;

    use bytes::Buf;
    use datafusion_datasource::{PartitionedFile, file_stream::FileOpenFuture};
    use futures::StreamExt;
    use object_store::{GetResultPayload, ObjectStore, ObjectStoreExt};

    pub struct AvroOpener {
        pub config: Arc<AvroSource>,
        pub object_store: Arc<dyn ObjectStore>,
    }

    impl FileOpener for AvroOpener {
        fn open(&self, partitioned_file: PartitionedFile) -> Result<FileOpenFuture> {
            let config = Arc::clone(&self.config);
            let object_store = Arc::clone(&self.object_store);
            Ok(Box::pin(async move {
                let r = object_store
                    .get(&partitioned_file.object_meta.location)
                    .await?;
                match r.payload {
                    GetResultPayload::File(file, _) => {
                        let reader = config.open(file)?;
                        Ok(futures::stream::iter(reader)
                            .map(|r| r.map_err(Into::into))
                            .boxed())
                    }
                    GetResultPayload::Stream(_) => {
                        let bytes = r.bytes().await?;
                        let reader = config.open(bytes.reader())?;
                        Ok(futures::stream::iter(reader)
                            .map(|r| r.map_err(Into::into))
                            .boxed())
                    }
                }
            }))
        }
    }
}
