use crate::core::{Segment, SegmentComponent};
use crate::fastfield::CompositeFastFieldSerializer;
use crate::fieldnorm::FieldNormsSerializer;
use crate::postings::InvertedIndexSerializer;
use crate::store::StoreWriter;

/// Segment serializer is in charge of laying out on disk
/// the data accumulated and sorted by the `SegmentWriter`.
pub struct SegmentSerializer {
    segment: Segment,
    pub(crate) store_writer: StoreWriter,
    fast_field_serializer: CompositeFastFieldSerializer,
    fieldnorms_serializer: Option<FieldNormsSerializer>,
    postings_serializer: InvertedIndexSerializer,
}

impl SegmentSerializer {
    /// Creates a new `SegmentSerializer`.
    pub fn for_segment(
        mut segment: Segment,
        is_in_merge: bool,
    ) -> crate::Result<SegmentSerializer> {
        // If the segment is going to be sorted, we stream the docs first to a temporary file.
        // In the merge case this is not necessary because we can kmerge the already sorted
        // segments
        let remapping_required = segment.index().settings().sort_by_field.is_some() && !is_in_merge;
        let store_component = if remapping_required {
            SegmentComponent::TempStore
        } else {
            SegmentComponent::Store
        };
        let store_write = segment.open_write(store_component)?;

        let fast_field_write = segment.open_write(SegmentComponent::FastFields)?;
        let fast_field_serializer = CompositeFastFieldSerializer::from_write(fast_field_write)?;

        let fieldnorms_write = segment.open_write(SegmentComponent::FieldNorms)?;
        let fieldnorms_serializer = FieldNormsSerializer::from_write(fieldnorms_write)?;

        let postings_serializer = InvertedIndexSerializer::open(&mut segment)?;
        let compressor = segment.index().settings().docstore_compression;
        Ok(SegmentSerializer {
            segment,
            store_writer: StoreWriter::new(store_write, compressor),
            fast_field_serializer,
            fieldnorms_serializer: Some(fieldnorms_serializer),
            postings_serializer,
        })
    }

    /// The memory used (inclusive childs)
    pub fn mem_usage(&self) -> usize {
        self.store_writer.mem_usage()
    }

    pub fn segment(&self) -> &Segment {
        &self.segment
    }

    pub fn segment_mut(&mut self) -> &mut Segment {
        &mut self.segment
    }

    /// Accessor to the `PostingsSerializer`.
    pub fn get_postings_serializer(&mut self) -> &mut InvertedIndexSerializer {
        &mut self.postings_serializer
    }

    /// Accessor to the `FastFieldSerializer`.
    pub fn get_fast_field_serializer(&mut self) -> &mut CompositeFastFieldSerializer {
        &mut self.fast_field_serializer
    }

    /// Extract the field norm serializer.
    ///
    /// Note the fieldnorms serializer can only be extracted once.
    pub fn extract_fieldnorms_serializer(&mut self) -> Option<FieldNormsSerializer> {
        self.fieldnorms_serializer.take()
    }

    /// Accessor to the `StoreWriter`.
    pub fn get_store_writer(&mut self) -> &mut StoreWriter {
        &mut self.store_writer
    }

    /// Finalize the segment serialization.
    pub fn close(mut self) -> crate::Result<()> {
        if let Some(fieldnorms_serializer) = self.extract_fieldnorms_serializer() {
            fieldnorms_serializer.close()?;
        }
        self.fast_field_serializer.close()?;
        self.postings_serializer.close()?;
        self.store_writer.close()?;
        Ok(())
    }
}