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use std::iter;
use std::sync::{Arc, RwLock};

use futures_util::{stream, StreamExt};
use vortex_array::ArrayData;
use vortex_error::VortexResult;
use vortex_io::{IoDispatcher, VortexReadAt};

use super::{LayoutMessageCache, LayoutReader};
use crate::read::buffered::{BufferedLayoutReader, ReadMasked};
use crate::{PollRead, RowMask};

struct MetadataMaskReader {
    layout: Box<dyn LayoutReader>,
}

impl MetadataMaskReader {
    pub fn new(layout: Box<dyn LayoutReader>) -> Self {
        Self { layout }
    }
}

impl ReadMasked for MetadataMaskReader {
    type Value = Vec<Option<ArrayData>>;

    fn read_masked(
        &self,
        _mask: &RowMask,
    ) -> VortexResult<Option<PollRead<Vec<Option<ArrayData>>>>> {
        self.layout.poll_metadata()
    }
}

pub async fn fetch_metadata<R: VortexReadAt + Unpin>(
    input: R,
    dispatcher: Arc<IoDispatcher>,
    root_layout: Box<dyn LayoutReader>,
    layout_cache: Arc<RwLock<LayoutMessageCache>>,
) -> VortexResult<Option<Vec<Option<ArrayData>>>> {
    let mut metadata_reader = BufferedLayoutReader::new(
        input,
        dispatcher,
        stream::iter(iter::once(Ok(RowMask::new_valid_between(0, 1)))),
        MetadataMaskReader::new(root_layout),
        layout_cache,
    );

    metadata_reader.next().await.transpose()
}

#[cfg(test)]
mod test {
    use std::sync::{Arc, RwLock};

    use vortex_array::array::{ChunkedArray, StructArray};
    use vortex_array::compute::scalar_at;
    use vortex_array::{ArrayDType as _, ArrayData, IntoArrayData as _};
    use vortex_buffer::{Buffer, BufferString};
    use vortex_io::IoDispatcher;

    use crate::metadata::fetch_metadata;
    use crate::{
        read_initial_bytes, LayoutDeserializer, LayoutMessageCache, RelativeLayoutCache, Scan,
        VortexFileWriter,
    };

    #[tokio::test]
    #[cfg_attr(miri, ignore)]
    async fn read_metadata_works() {
        let name_chunk1 = ArrayData::from_iter(vec![
            Some("Joseph".to_owned()),
            Some("James".to_owned()),
            Some("Angela".to_owned()),
        ]);
        let age_chunk1 = ArrayData::from_iter(vec![Some(25_i32), Some(31), None]);
        let name_chunk2 = ArrayData::from_iter(vec![
            Some("Pharrell".to_owned()),
            Some("Khalil".to_owned()),
            Some("Mikhail".to_owned()),
            None,
        ]);
        let age_chunk2 = ArrayData::from_iter(vec![Some(57_i32), Some(18), None, Some(32)]);

        let chunk1 = StructArray::from_fields(&[("name", name_chunk1), ("age", age_chunk1)])
            .unwrap()
            .into_array();
        let chunk2 = StructArray::from_fields(&[("name", name_chunk2), ("age", age_chunk2)])
            .unwrap()
            .into_array();
        let dtype = chunk1.dtype().clone();

        let array = ChunkedArray::try_new(vec![chunk1, chunk2], dtype)
            .unwrap()
            .into_array();

        let buffer = Vec::new();
        let written_bytes = VortexFileWriter::new(buffer)
            .write_array_columns(array)
            .await
            .unwrap()
            .finalize()
            .await
            .unwrap();
        let written_bytes = Buffer::from(written_bytes);

        let n_bytes = written_bytes.len();
        let initial_read = read_initial_bytes(&written_bytes, n_bytes as u64)
            .await
            .unwrap();
        let lazy_dtype = Arc::new(initial_read.lazy_dtype());
        let layout_deserializer = LayoutDeserializer::default();
        let layout_message_cache = Arc::new(RwLock::new(LayoutMessageCache::default()));
        let layout_reader = layout_deserializer
            .read_layout(
                initial_read.fb_layout(),
                Scan::empty(),
                RelativeLayoutCache::new(layout_message_cache.clone(), lazy_dtype.clone()),
            )
            .unwrap();
        let io = IoDispatcher::default();
        let metadata_table = fetch_metadata(
            written_bytes,
            io.into(),
            layout_reader,
            layout_message_cache,
        )
        .await
        .unwrap();

        assert!(metadata_table.is_some());
        let metadata_table = metadata_table.unwrap();
        assert_eq!(metadata_table.len(), 2);
        assert!(metadata_table.iter().all(Option::is_some));

        let name_metadata_table = metadata_table[0]
            .as_ref()
            .unwrap()
            .as_struct_array()
            .unwrap();

        let min = name_metadata_table.field_by_name("min").unwrap();
        let chunk1_min = scalar_at(&min, 0).unwrap();
        let chunk2_min = scalar_at(&min, 1).unwrap();
        assert_eq!(
            chunk1_min.as_utf8().value(),
            Some(BufferString::from("Angela"))
        );
        assert_eq!(
            chunk2_min.as_utf8().value(),
            Some(BufferString::from("Khalil"))
        );

        let max = name_metadata_table.field_by_name("max").unwrap();
        let chunk1_max = scalar_at(&max, 0).unwrap();
        let chunk2_max = scalar_at(&max, 1).unwrap();
        assert_eq!(
            chunk1_max.as_utf8().value(),
            Some(BufferString::from("Joseph"))
        );
        assert_eq!(
            chunk2_max.as_utf8().value(),
            Some(BufferString::from("Pharrell"))
        );

        let null_count = name_metadata_table.field_by_name("null_count").unwrap();
        let chunk1_null_count = scalar_at(&null_count, 0).unwrap();
        let chunk2_null_count = scalar_at(&null_count, 1).unwrap();
        assert_eq!(
            chunk1_null_count.as_primitive().typed_value::<u64>(),
            Some(0)
        );
        assert_eq!(
            chunk2_null_count.as_primitive().typed_value::<u64>(),
            Some(1)
        );

        let age_metadata_table = metadata_table[1]
            .as_ref()
            .unwrap()
            .as_struct_array()
            .unwrap();

        let min = age_metadata_table.field_by_name("min").unwrap();
        let chunk1_min = scalar_at(&min, 0).unwrap();
        let chunk2_min = scalar_at(&min, 1).unwrap();
        assert_eq!(chunk1_min.as_primitive().typed_value::<i32>(), Some(25));
        assert_eq!(chunk2_min.as_primitive().typed_value::<i32>(), Some(18));

        let max = age_metadata_table.field_by_name("max").unwrap();
        let chunk1_max = scalar_at(&max, 0).unwrap();
        let chunk2_max = scalar_at(&max, 1).unwrap();
        assert_eq!(chunk1_max.as_primitive().typed_value::<i32>(), Some(31));
        assert_eq!(chunk2_max.as_primitive().typed_value::<i32>(), Some(57));

        let null_count = age_metadata_table.field_by_name("null_count").unwrap();
        let chunk1_null_count = scalar_at(&null_count, 0).unwrap();
        let chunk2_null_count = scalar_at(&null_count, 1).unwrap();
        assert_eq!(
            chunk1_null_count.as_primitive().typed_value::<u64>(),
            Some(1)
        );
        assert_eq!(
            chunk2_null_count.as_primitive().typed_value::<u64>(),
            Some(1)
        );
    }
}