use std::{
    fs::File,
    io::BufReader,
    str::FromStr,
};

use anyhow::Context;
use pandora_lib_variants::variants::Variant;

use crate::{callers::Caller, io::tsv::TsvLine, variant::vcf_variant::VariantType};

/// A single row from a VCF file (tab-separated, no header row).
#[derive(Debug, Eq, PartialEq, Clone)]
pub struct VCFRow {
    pub chr: String,
    pub pos: u32,
    pub id: String,
    pub reference: String,
    pub alt: String,
    pub qual: String,
    pub filter: String,
    pub info: String,
    pub format: String,
    pub value: String,
}

impl FromStr for VCFRow {
    type Err = anyhow::Error;

    fn from_str(s: &str) -> anyhow::Result<Self> {
        let f: Vec<&str> = s.split('\t').collect();
        let get = |i: usize, name: &str| -> anyhow::Result<&str> {
            f.get(i).copied().ok_or_else(|| anyhow::anyhow!("missing {name} (col {i})"))
        };
        Ok(Self {
            chr:       get(0, "chr")?.to_string(),
            pos:       get(1, "pos")?.parse().context("bad pos")?,
            id:        get(2, "id")?.to_string(),
            reference: get(3, "reference")?.to_string(),
            alt:       get(4, "alt")?.to_string(),
            qual:      get(5, "qual")?.to_string(),
            filter:    get(6, "filter")?.to_string(),
            info:      get(7, "info")?.to_string(),
            format:    get(8, "format")?.to_string(),
            value:     get(9, "value")?.to_string(),
        })
    }
}

pub fn read_vcf(
    path: &str,
    caller: &Caller,
    variant_type: &VariantType,
) -> anyhow::Result<Vec<Variant>> {
    let mut reader = BufReader::new(get_reader(path)?);
    let mut line = TsvLine::new();
    let mut all = Vec::new();

    // should be replaced with bcftools
    while line.read(&mut reader)? {
        if line.as_str().starts_with('#') || line.as_str().is_empty() {
            continue;
        }
        let record: VCFRow = line.as_str().parse()?;

        // Normalize into multirows
        if record.alt.contains(",") {
            let alts = record.alt.split(',').collect::<Vec<&str>>();
            let n = alts.len();

            let vals = record.value.split(':').collect::<Vec<&str>>();
            let ads = vals.get(3).unwrap().split(',').collect::<Vec<&str>>();
            let vafs = vals.get(4).unwrap().split(',').collect::<Vec<&str>>();
            let pls = vals.get(5).unwrap().split(',').collect::<Vec<&str>>();

            for i in 0..n {
                let cp = &pls[(i * 3)..(i * 3 + 3)];
                let nval = format!(
                    "{}:{}:{}:{}:{}:{}",
                    vals[0],
                    vals[1],
                    vals[2],
                    [ads[0], ads[i + 1]].join(","),
                    vafs[i],
                    cp.join(",")
                );

                let mut rec = record.clone();
                rec.value = nval.clone();
                rec.alt = alts[i].to_string();

                all.push(rec);
            }
        } else {
            all.push(record);
        }
    }

    let base_n = "N".to_string();
    let res: Vec<Variant> = all
        .par_iter_mut()
        .map(|row| {
            // for Sniffles normalize insertion/deletion position (after the pos)
            if caller == &VCFSource::Sniffles && row.reference == base_n && row.alt.len() > 1 {
                row.pos -= 1;
            }
            let mut v = Variant::from_vcfrow(row, caller.clone(), variant_type.clone()).unwrap();
            v.get_depth();
            v.get_n_alt();
            v
        })
        .filter(|v| {
            for cd in v.callers_data.iter() {
                if cd.should_filter() {
                    return false;
                }
            }
            true
        })
        .collect();

    Ok(res)
}

pub fn get_reader(path: &str) -> anyhow::Result<Box<dyn std::io::Read>> {
    let file_type = *path.split(".").collect::<Vec<&str>>().last()?;
    assert!(file_type == "gz" || file_type == "vcf");

    let raw_reader: Box<dyn std::io::Read> = Box::new(File::open(path)?);

    match file_type {
        "gz" => {
            let reader = Box::new(BGZFReader::new(raw_reader)?);
            Ok(Box::new(BufReader::new(reader)))
        }
        "vcf" => {
            Ok(Box::new(BufReader::new(raw_reader)))
        }
        t => {
            panic!("unknown file type: {}", t)
        }
    }
}