use std::collections::HashSet;

use rayon::prelude::*;

use super::variant::{AlterationCategory, VcfVariant};
use crate::{
    annotation::{Annotation, Annotations},
    collection::{bam::{counts_at, counts_ins_at}, vcf::Vcf},
    helpers::estimate_shannon_entropy,
    pipes::somatic::sequence_at,
};

#[derive(Debug, Clone)]
pub struct VariantCollection {
    pub variants: Vec<VcfVariant>,
    pub vcf: Vcf,
}

impl VariantCollection {
    pub fn keys(&self) -> Vec<u128> {
        self.variants.iter().map(|v| v.hash_variant()).collect()
    }

    pub fn retain_keys(&mut self, keys_to_keep: &HashSet<u128>) {
        self.variants
            .retain(|v| keys_to_keep.contains(&v.hash_variant()));
    }

    pub fn chunk_size(&self, max_threads: u8) -> usize {
        let total_items = self.variants.len();
        let min_chunk_size = 1000;
        let max_chunks = max_threads;

        let optimal_chunk_size = total_items.div_ceil(max_chunks as usize);
        optimal_chunk_size.max(min_chunk_size)
    }

    pub fn annotate_with_sequence_entropy(
        &self,
        annotations: &Annotations,
        reference: &str,
        seq_len: usize,
        max_threads: u8,
    ) {
        self.variants
            .par_chunks(self.chunk_size(max_threads))
            .for_each(|chunk| {
                let mut fasta_reader = noodles_fasta::indexed_reader::Builder::default()
                    .build_from_path(reference)
                    .unwrap();

                for c in chunk {
                    let key = c.hash_variant();
                    let mut anns = annotations.store.entry(key).or_default();

                    if !anns
                        .iter()
                        .any(|e| matches!(e, Annotation::ShannonEntropy(_)))
                    {
                        if let Ok(r) = sequence_at(
                            &mut fasta_reader,
                            &c.position.contig(),
                            c.position.position as usize,
                            seq_len,
                        ) {
                            let ent = estimate_shannon_entropy(r.as_str());
                            anns.push(Annotation::ShannonEntropy(ent));
                        }
                    }
                }
            });
    }

    pub fn annotate_with_constit_bam(
        &self,
        annotations: &Annotations,
        constit_bam_path: &str,
        max_threads: u8,
    ) -> anyhow::Result<()> {
        self.variants
            .par_chunks(self.chunk_size(max_threads))
            .try_for_each(|chunk| {
                let mut bam = rust_htslib::bam::IndexedReader::from_path(constit_bam_path)
                    .map_err(|e| anyhow::anyhow!("Failed to open BAM file: {e}"))?;

                for var in chunk {
                    let key = var.hash_variant();
                    let mut anns = annotations.store.entry(key).or_default();

                    if anns
                        .iter()
                        .filter(|e| {
                            matches!(e, Annotation::ConstitAlt(_) | Annotation::ConstitDepth(_))
                        })
                        .count()
                        != 2
                    {
                        let mut n_alt = 0;
                        let mut depth = 0;
                        let mut alt_seq = var.alternative.to_string();

                        let c = if var.alteration_category() == AlterationCategory::Ins {
                            alt_seq = alt_seq.split_off(1);
                            counts_ins_at(&mut bam, &var.position.contig(), var.position.position)?
                        } else {
                            counts_at(&mut bam, &var.position.contig(), var.position.position)?
                        };

                        for (seq, n) in c {
                            if seq == alt_seq {
                                n_alt = n;
                            }
                            depth += n;
                        }


                        anns.push(Annotation::ConstitAlt(n_alt as u16));
                        anns.push(Annotation::ConstitDepth(depth as u16));
                    }
                }
                anyhow::Ok(())
            })?;
        Ok(())
    }
}