//! # ClairS Somatic Variant Calling Pipeline
//!
//! This module provides a pipeline runner for [ClairS](https://github.com/HKU-BAL/ClairS),
//! a deep learning-based somatic variant caller designed for long-read sequencing data
//! (ONT and PacBio HiFi).
//!
//! ## Overview
//!
//! ClairS performs somatic variant calling on paired tumor-normal samples using:
//!
//! - Haplotype-aware variant calling with LongPhase integration
//! - Separate SNV and indel calling pipelines
//! - Clair3-based germline variant detection on the normal sample
//!
//! ## Key Features
//!
//! - **Deep learning-based** - CNN models trained on long-read data
//! - **Haplotype-aware** - Uses phased germline variants for improved accuracy
//! - **Dual output** - Somatic and germline variants in a single run
//! - **Platform flexibility** - Supports ONT (R9/R10) and PacBio HiFi
//! - **Parallel execution** - Genome chunking for HPC scalability
//!
//! ## Requirements
//!
//! Before running ClairS, ensure:
//! - Tumor and normal BAMs are indexed (`.bai` files present)
//! - Reference genome is accessible
//! - Singularity/Docker image is available
//! - Platform is correctly specified (`config.clairs_platform`)
//!
//! ## Execution Modes
//!
//! The module supports three execution strategies:
//!
//! - **Local** ([`ClairS::run_local`]) — Single-node execution, useful for debugging
//! - **Slurm** ([`ClairS::run_sbatch`]) — Single HPC job submission
//! - **Chunked** ([`run_clairs_chunked_sbatch_with_merge`]) — Parallel execution across genome regions
//!
//! ### Chunked Parallel Execution
//!
//! For large genomes, the chunked mode provides significant speedup:
//!
//! ```text
//! ┌─────────────────────────────────────────────────────────────────┐
//! │                     Genome Splitting                            │
//! │  chr1:1-50M  │  chr1:50M-100M  │  chr2:1-50M  │  ...  │  chrN   │
//! └──────┬───────┴────────┬────────┴───────┬──────┴───────┴────┬────┘
//!        │                │                │                   │
//!        ▼                ▼                ▼                   ▼
//! ┌────────────┐  ┌────────────┐  ┌────────────┐       ┌────────────┐
//! │  ClairS    │  │  ClairS    │  │  ClairS    │  ...  │  ClairS    │
//! │  Part 1    │  │  Part 2    │  │  Part 3    │       │  Part N    │
//! └─────┬──────┘  └─────┬──────┘  └─────┬──────┘       └─────┬──────┘
//!       │               │               │                   │
//!       ▼               ▼               ▼                   ▼
//! ┌────────────┐  ┌────────────┐  ┌────────────┐       ┌────────────┐
//! │ Postprocess│  │ Postprocess│  │ Postprocess│  ...  │ Postprocess│
//! │ SNV+Indel  │  │ SNV+Indel  │  │ SNV+Indel  │       │ SNV+Indel  │
//! │ → PASS     │  │ → PASS     │  │ → PASS     │       │ → PASS     │
//! └─────┬──────┘  └─────┬──────┘  └─────┬──────┘       └─────┬──────┘
//!       │               │               │                   │
//!       └───────────────┴───────┬───────┴───────────────────┘
//!                               ▼
//!                    ┌─────────────────────┐
//!                    │   bcftools concat   │
//!                    │   (somatic PASS)    │
//!                    └──────────┬──────────┘
//!                               ▼
//!                    ┌─────────────────────┐
//!                    │   Final VCF Output  │
//!                    └─────────────────────┘
//! ```
//!
//! ## Output Files
//!
//! Somatic variants (PASS only):
//! ```text
//! {result_dir}/{id}/clairs/{id}_clairs.pass.vcf.gz
//! ```
//!
//! Germline variants (PASS only):
//! ```text
//! {result_dir}/{id}/clairs/clair3_germline.pass.vcf.gz
//! ```
//!
//! ## Post-processing Pipeline
//!
//! Each ClairS run (or part) undergoes automatic post-processing:
//!
//! 1. **Somatic**: Concatenate SNV + indel VCFs → filter PASS variants
//! 2. **Germline**: Filter PASS variants from Clair3 germline output
//!
//! ## Usage
//!
//! ### Basic Slurm Execution
//!
//! ```ignore
//! use crate::config::Config;
//! use crate::pipes::clairs::ClairS;
//! use crate::pipes::Initialize;
//!
//! let config = Config::default();
//! let mut clairs = ClairS::initialize("sample_001", &config)?;
//! let output = clairs.run_sbatch()?;
//! # Ok::<(), anyhow::Error>(())
//! ```
//!
//! ### Chunked Parallel Execution (Recommended for WGS)
//!
//! ```ignore
//! use crate::config::Config;
//! use crate::pipes::clairs::run_clairs_chunked_sbatch_with_merge;
//!
//! let config = Config::default();
//! let outputs = run_clairs_chunked_sbatch_with_merge("sample_001", &config, 20)?;
//! # Ok::<(), anyhow::Error>(())
//! ```
//!
//! ### Loading Variants for Downstream Analysis
//!
//! ```ignore
//! use crate::annotation::Annotations;
//! use crate::variant::vcf_variant::Variants;
//!
//! let annotations = Annotations::new();
//! let somatic = clairs.variants(&annotations)?;
//! let germline = clairs.germline(&annotations)?;
//!
//! println!("Somatic: {} variants", somatic.variants.len());
//! println!("Germline: {} variants", germline.variants.len());
//! # Ok::<(), anyhow::Error>(())
//! ```
//!
//! ## Configuration Requirements
//!
//! The following [`Config`](crate::config::Config) fields must be set:
//!
//! - `singularity_bin` — Path to Singularity executable
//! - `clairs_image` — ClairS container image path
//! - `reference` — Reference genome FASTA
//! - `clairs_threads` — CPU threads per job
//! - `clairs_platform` — Sequencing platform (`ont_r10_dorado_sup_4khz`, `hifi_revio`, etc.)
//! - `clairs_force` — Force re-run even if outputs exist
//!
//! ## Implemented Traits
//!
//! - [`Initialize`](crate::pipes::Initialize) — Setup and directory creation
//! - [`ShouldRun`](crate::pipes::ShouldRun) — Timestamp-based execution gating
//! - [`JobCommand`](crate::commands::Command) — Command string generation
//! - [`LocalRunner`](crate::commands::LocalRunner) — Local execution support
//! - [`SbatchRunner`](crate::commands::SbatchRunner) — Slurm job submission
//! - [`Run`](crate::runners::Run) — Unified execution interface
//! - [`Variants`](crate::variant::vcf_variant::Variants) — Somatic variant loading
//! - [`CallerCat`](crate::annotation::CallerCat) — Caller annotation category
//! - [`Label`](crate::variant::vcf_variant::Label) — Human-readable identifier
//! - [`Version`](crate::pipes::Version) — Tool version extraction
//!
//! ## Dependencies
//!
//! External tools (containerized or system):
//!
//! - **ClairS** — Somatic variant calling
//! - **bcftools** — VCF concatenation and filtering
//!
//! ## References
//!
//! - [ClairS GitHub repository](https://github.com/HKU-BAL/ClairS)
//! - [ClairS publication (Nature Communications, 2024)](https://doi.org/10.1038/s41467-024-52832-2)
use crate::{
    annotation::{Annotation, Annotations, Caller, CallerCat, Sample}, collection::vcf::Vcf, commands::{
        Command as JobCommand, LocalBatchRunner, LocalRunner, SbatchRunner, SlurmParams, SlurmRunner, bcftools::{BcftoolsConcat, BcftoolsKeepPass}, samtools::SamtoolsMergeMany
    }, config::Config, helpers::{
        get_genome_sizes, is_file_older, list_files_recursive, remove_dir_if_exists,
        singularity_bind_flags, split_genome_into_n_regions_exact,
    }, io::vcf::read_vcf, locker::SampleLock, pipes::{Initialize, ShouldRun, Version}, run, run_many, runners::Run, variant::{
        variant_collection::VariantCollection,
        vcf_variant::{Label, Variants},
    }
};

use anyhow::Context;
use log::{debug, info, warn};
use rayon::iter::{IntoParallelRefIterator, ParallelIterator};
use regex::Regex;
use rust_htslib::bam::{self, Read};
use std::{
    fmt, fs,
    path::{Path, PathBuf},
    process::{Command as ProcessCommand, Stdio},
};
use uuid::Uuid;

/// ClairS haplotype-aware somatic variant caller runner.
///
/// Executes ClairS for paired tumor-normal variant calling with automatic
/// post-processing (SNV+indel concatenation, PASS filtering, germline extraction).
///
/// # Fields
///
/// - `id` - Sample identifier (e.g., "34528")
/// - `config` - Global pipeline configuration
/// - `log_dir` - Directory for execution logs (e.g., "{result_dir}/{id}/log/clairs")
/// - `region` - Optional genomic region for targeted calling (e.g., `Some("chr1:1000-2000")`)
/// - `part_index` - Optional chunk index for parallel execution (e.g., `Some(3)` for part 3 of N)
///
/// # Execution Modes
///
/// - **Local** - Direct execution via `run_local()`
/// - **Slurm** - Single job submission via `run_sbatch()`
/// - **Chunked** - Parallel genome-wide execution via [`run_clairs_chunked_sbatch_with_merge`]
///
/// # Output Files
///
/// - Somatic PASS VCF: `{clairs_output_dir}/{id}_clairs.pass.vcf.gz`
/// - Germline PASS VCF: `{clairs_output_dir}/clair3_germline.pass.vcf.gz`
///
/// # Chunked Execution
///
/// For whole-genome sequencing, use [`run_clairs_chunked_sbatch_with_merge`] which:
/// 1. Splits genome into N equal-sized regions
/// 2. Runs ClairS in parallel Slurm jobs (one per region)
/// 3. Post-processes each part (concat SNV+indel, filter PASS)
/// 4. Merges all part PASS VCFs into final output
#[derive(Debug, Clone)]
pub struct ClairS {
    /// Sample identifier
    pub id: String,
    /// Global pipeline configuration
    pub config: Config,
    /// Directory for log file storage
    pub log_dir: String,
    /// Optional genomic region restriction (format: "chr:start-end")
    pub region: Option<String>,
    /// Optional part index for chunked parallel runs (1-indexed)
    pub part_index: Option<usize>,
}

impl fmt::Display for ClairS {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        writeln!(f, "🧬 ClairS {}", self.id)?;
        writeln!(
            f,
            "   Region    : {}",
            self.region.as_deref().unwrap_or("genome-wide")
        )?;
        writeln!(
            f,
            "   Part      : {}",
            self.part_index
                .map_or("full".into(), |n| format!("part{n}"))
        )?;
        writeln!(f, "   Log dir   : {}", self.log_dir)
    }
}

impl Initialize for ClairS {
    fn initialize(id: &str, config: &Config) -> anyhow::Result<Self> {
        let id = id.to_string();

        info!("Initializing ClairS for {id}");
        let log_dir = format!("{}/{}/log/clairs", config.result_dir, &id);

        let clairs = Self {
            id,
            log_dir,
            config: config.clone(),
            region: None,
            part_index: None,
        };

        if clairs.config.clairs_force {
            remove_dir_if_exists(&clairs.config.clairs_output_dir(&clairs.id))?;
        }

        Ok(clairs)
    }
}

impl ShouldRun for ClairS {
    /// Determines whether ClairS should be re-run based on BAM modification timestamps.
    fn should_run(&self) -> bool {
        let passed_vcf = &self.config.clairs_passed_vcf(&self.id);
        let normal_older =
            is_file_older(passed_vcf, &self.config.normal_bam(&self.id), true).unwrap_or(true);
        let tumor_older =
            is_file_older(passed_vcf, &self.config.tumoral_bam(&self.id), true).unwrap_or(true);

        let result = normal_older || tumor_older;
        if result {
            info!("ClairS should run for id: {}.", self.id);
        }
        result
    }
}

impl JobCommand for ClairS {
    fn init(&mut self) -> anyhow::Result<()> {
        let output_dir = self.part_output_dir();

        fs::create_dir_all(&output_dir)
            .with_context(|| format!("Failed to create dir: {output_dir}"))?;

        fs::create_dir_all(&self.log_dir)
            .with_context(|| format!("Failed to create dir: {}", self.log_dir))?;

        Ok(())
    }

    fn cmd(&self) -> String {
        let output_dir = self.part_output_dir();

        let region_arg = self
            .region
            .as_ref()
            .map(|r| format!("-r '{r}'"))
            .unwrap_or_default();

        let sample_name = format!("{}_diag", self.id);

        let bind_flags = singularity_bind_flags([
            &self.config.tumoral_bam(&self.id),
            &self.config.normal_bam(&self.id),
            &self.config.reference,
            &output_dir,
            &self.log_dir,
            &self.config.tmp_dir,
        ]);

        format!(
            "{singularity_bin} exec \
             {binds} \
             --bind {output_dir}:{output_dir} \
             {image} \
             /opt/bin/run_clairs \
             -T {tumor_bam} \
             -N {normal_bam} \
             -R {reference} \
             -t {threads} \
             -p {platform} \
             --enable_indel_calling \
             --include_all_ctgs \
             --print_germline_calls \
             --enable_clair3_germline_output \
             --use_longphase_for_intermediate_haplotagging true \
             --output_dir {output_dir} \
             -s {sample_name} \
             {region_arg}",
            singularity_bin = self.config.singularity_bin,
            binds = bind_flags,
            image = self.config.clairs_image,
            tumor_bam = self.config.tumoral_bam(&self.id),
            normal_bam = self.config.normal_bam(&self.id),
            reference = self.config.reference,
            threads = self.config.clairs_threads,
            platform = self.config.clairs_platform,
            output_dir = output_dir,
            sample_name = sample_name,
            region_arg = region_arg,
        )
    }
}

impl LocalRunner for ClairS {}
impl LocalBatchRunner for ClairS {}

impl SlurmRunner for ClairS {
    fn slurm_args(&self) -> Vec<String> {
        SlurmParams {
            job_name: Some(format!("clairs_{}", self.id)),
            cpus_per_task: Some(self.config.clairs_threads as u32),
            mem: Some("80G".into()),
            partition: Some("shortq".into()),
            gres: None,
        }
        .to_args()
    }
}

impl SbatchRunner for ClairS {
    fn slurm_params(&self) -> SlurmParams {
        SlurmParams {
            job_name: Some(format!("clairs_{}", self.id)),
            cpus_per_task: Some(self.config.clairs_threads as u32),
            mem: Some("70G".into()),
            partition: Some("shortq".into()),
            gres: None,
        }
    }
}

impl Run for ClairS {
    fn run(&mut self) -> anyhow::Result<()> {
        if !self.should_run() {
            info!("ClairS is up-to-date.");
            return Ok(());
        }

        // Acquire lock before any work
        let lock_dir = format!("{}/locks", self.config.result_dir);
        let _lock = SampleLock::acquire(&lock_dir, &self.id, "clairs")
            .with_context(|| format!("Cannot start ClairS for {}", self.id))?;


        if self.config.slurm_runner {
            run_clairs_chunked(&self.id, &self.config, 50)?;
            // merge_haplotaged_tmp_bam(&self.config, &self.id)?;
        } else {
            run!(&self.config, self)?;
            let mut germline = self.process_germline()?;
            let report = run!(&self.config, &mut germline)
                .with_context(|| format!("Failed to filter germline PASS for {}", self.id))?;

            report
                .save_to_file(format!("{}/bcftools_germline_pass_", self.log_dir))
                .context("Failed to save germline PASS logs")?;
            let (mut concat, tmp_path) = self.process_somatic_concat()?;
            let (snv_vcf, indel_vcf) = self.config.clairs_output_vcfs(&self.id);

            let report = run!(&self.config, &mut concat)
                .with_context(|| format!("Failed to concat {} and {}", snv_vcf, indel_vcf))?;

            report
                .save_to_file(format!("{}/bcftools_concat_", self.log_dir))
                .context("Failed to save concat logs")?;

            let mut keep_pass = self.process_somatic_pass(&tmp_path)?;
            let report = run!(&self.config, &mut keep_pass)
                .with_context(|| format!("Failed to filter PASS for {}", self.id))?;

            report
                .save_to_file(format!("{}/bcftools_pass_", self.log_dir))
                .context("Failed to save PASS filter logs")?;

            // Clean up temporary concatenated VCF
            debug!("Removing temporary file: {}", tmp_path);
            if let Err(e) = fs::remove_file(&tmp_path) {
                warn!("Failed to remove temporary file {}: {}", tmp_path, e);
            }
        }
        Ok(())
    }
}

impl ClairS {
    /// Returns the germline PASS VCF path.
    ///
    /// - Part runs: `{part_dir}/clair3_germline.part{N}.pass.vcf.gz`
    /// - Full runs: canonical path from config
    fn germline_passed_vcf_path(&self) -> String {
        match self.part_index {
            Some(idx) => {
                let outdir = self.part_output_dir();
                format!("{outdir}/clair3_germline.part{idx}.pass.vcf.gz")
            }
            None => self.config.clairs_germline_passed_vcf(&self.id),
        }
    }

    fn process_germline(&self) -> anyhow::Result<BcftoolsKeepPass> {
        let germline_passed = self.germline_passed_vcf_path();

        let germline_input = match self.part_index {
            Some(_) => {
                let output_dir = self.part_output_dir();
                let base = self.config.clairs_germline_normal_vcf(&self.id);
                let base_name = Path::new(&base)
                    .file_name()
                    .expect("Germline VCF should have filename")
                    .to_string_lossy();
                format!("{output_dir}/{base_name}")
            }
            None => self.config.clairs_germline_normal_vcf(&self.id),
        };

        info!(
            "Filtering germline PASS variants for {} part {:?}",
            self.id, self.part_index
        );

        let cmd =
            BcftoolsKeepPass::from_config(&self.config, germline_input, germline_passed.clone());

        Ok(cmd)
    }

    fn process_somatic_concat(&self) -> anyhow::Result<(BcftoolsConcat, String)> {
        let output_dir = self.part_output_dir();
        let (snv_vcf_base, indel_vcf_base) = self.config.clairs_output_vcfs(&self.id);

        let snv_vcf = format!(
            "{}/{}",
            output_dir,
            Path::new(&snv_vcf_base)
                .file_name()
                .expect("SNV VCF should have filename")
                .to_string_lossy()
        );
        let indel_vcf = format!(
            "{}/{}",
            output_dir,
            Path::new(&indel_vcf_base)
                .file_name()
                .expect("Indel VCF should have filename")
                .to_string_lossy()
        );

        info!(
            "Concatenating and filtering somatic variants for {} part {:?}",
            self.id, self.part_index
        );

        let tmp_file =
            Path::new(&self.config.tmp_dir).join(format!("pandora-temp-{}.vcf.gz", Uuid::new_v4()));
        let tmp_path = tmp_file
            .to_str()
            .context("Temp path not valid UTF-8")?
            .to_string();

        // Concat SNV + indel
        Ok((
            BcftoolsConcat::from_config(
                &self.config,
                vec![PathBuf::from(&snv_vcf), PathBuf::from(&indel_vcf)],
                &tmp_path,
            ),
            tmp_path,
        ))
    }

    pub fn process_somatic_pass(&self, tmp_path: &str) -> anyhow::Result<BcftoolsKeepPass> {
        let passed_vcf = self.somatic_passed_vcf_path();

        // Filter PASS
        let keep_pass = BcftoolsKeepPass::from_config(&self.config, tmp_path, passed_vcf.clone());

        Ok(keep_pass)
    }

    /// Returns the per-part output directory.
    fn part_output_dir(&self) -> String {
        let base_dir = self.config.clairs_output_dir(&self.id);
        match self.part_index {
            Some(idx) => format!("{base_dir}/part{idx}"),
            None => base_dir,
        }
    }

    /// Returns the somatic PASS VCF path.
    ///
    /// - Part runs: `{part_dir}/clairs.part{N}.pass.vcf.gz`
    /// - Full runs: canonical path from config
    fn somatic_passed_vcf_path(&self) -> String {
        match self.part_index {
            Some(idx) => {
                let outdir = self.part_output_dir();
                format!("{outdir}/clairs.part{idx}.pass.vcf.gz")
            }
            None => self.config.clairs_passed_vcf(&self.id),
        }
    }
}

impl CallerCat for ClairS {
    fn caller_cat(&self) -> Annotation {
        Annotation::Callers(Caller::ClairS, Sample::Somatic)
    }
}

impl Variants for ClairS {
    fn variants(&self, annotations: &Annotations) -> anyhow::Result<VariantCollection> {
        let caller = self.caller_cat();
        let passed_vcf = &self.config.clairs_passed_vcf(&self.id);

        info!("Loading variants from {caller}: {passed_vcf}");

        let variants = read_vcf(passed_vcf)
            .with_context(|| format!("Failed to read ClairS VCF {passed_vcf}"))?;

        variants.par_iter().for_each(|v| {
            annotations.insert_update(v.hash(), std::slice::from_ref(&caller));
        });

        info!("{caller}: {} variants loaded", variants.len());

        Ok(VariantCollection {
            variants,
            vcf: Vcf::new(passed_vcf.into())?,
            caller,
        })
    }
}

impl ClairS {
    /// Loads germline variants from the Clair3 germline output.
    pub fn germline(&self, annotations: &Annotations) -> anyhow::Result<VariantCollection> {
        let caller = Annotation::Callers(Caller::ClairS, Sample::Germline);
        let germline_passed = &self.config.clairs_germline_passed_vcf(&self.id);

        info!("Loading germline variants from {caller}: {germline_passed}");

        let variants = read_vcf(germline_passed)?;

        variants.par_iter().for_each(|v| {
            annotations.insert_update(v.hash(), std::slice::from_ref(&caller));
        });

        info!("{caller}: {} variants loaded", variants.len());

        Ok(VariantCollection {
            variants,
            vcf: Vcf::new(germline_passed.into())?,
            caller,
        })
    }
}

impl Label for ClairS {
    fn label(&self) -> String {
        self.caller_cat().to_string()
    }
}

impl Version for ClairS {
    fn version(config: &Config) -> anyhow::Result<String> {
        let out = ProcessCommand::new("bash")
            .arg("-c")
            .arg(format!(
                "{} exec {} /opt/bin/run_clairs --version",
                config.singularity_bin, config.clairs_image
            ))
            .stdout(Stdio::piped())
            .stderr(Stdio::piped())
            .output()
            .context("Failed to spawn Singularity process")?;

        if !out.status.success() {
            let combined = format!(
                "{}{}",
                String::from_utf8_lossy(&out.stdout),
                String::from_utf8_lossy(&out.stderr)
            );
            anyhow::bail!(
                "Singularity exec failed with status {}: {}",
                out.status,
                combined
            );
        }

        let combined = format!(
            "{}{}",
            String::from_utf8_lossy(&out.stdout),
            String::from_utf8_lossy(&out.stderr)
        );

        parse_clairs_version(&combined)
    }

    fn version_slurm(config: &Config) -> anyhow::Result<String> {
        struct ClairSVersionJob<'a> {
            config: &'a Config,
        }

        impl JobCommand for ClairSVersionJob<'_> {
            fn cmd(&self) -> String {
                format!(
                    "{} exec {} /opt/bin/run_clairs --version",
                    self.config.singularity_bin, self.config.clairs_image
                )
            }
        }

        impl SlurmRunner for ClairSVersionJob<'_> {
            fn slurm_args(&self) -> Vec<String> {
                SlurmParams {
                    job_name: Some("clairs_version".into()),
                    partition: Some("shortq".into()),
                    cpus_per_task: Some(1),
                    mem: Some("10G".into()),
                    gres: None,
                }
                .to_args()
            }
        }

        let mut job = ClairSVersionJob { config };
        let out =
            SlurmRunner::exec(&mut job).context("Failed to run ClairS --version via Slurm")?;

        let mut combined = out.stdout.clone();
        if let Some(epilog) = &out.slurm_epilog {
            combined.push_str(&epilog.to_string());
        }
        combined.push_str(&out.stderr);

        parse_clairs_version(&combined)
    }
}

/// Parses ClairS version from command output.
fn parse_clairs_version(output: &str) -> anyhow::Result<String> {
    let re = Regex::new(r"(?m)run_clairs\s+([^\s]+)").expect("Version regex is valid");

    let caps = re
        .captures(output)
        .context("Could not parse ClairS version from output")?;

    Ok(caps
        .get(1)
        .expect("Regex has capture group 1")
        .as_str()
        .to_string())
}

/// Merges N chunked ClairS PASS VCFs into the final output.
fn merge_clairs_parts(base: &ClairS, n_parts: usize) -> anyhow::Result<()> {
    let mut part_pass_paths: Vec<PathBuf> = Vec::with_capacity(n_parts);

    for i in 1..=n_parts {
        let mut part = base.clone();
        part.part_index = Some(i);
        let part_pass = part.somatic_passed_vcf_path();

        anyhow::ensure!(
            Path::new(&part_pass).exists(),
            "Missing ClairS part {} PASS VCF: {}",
            i,
            part_pass
        );

        part_pass_paths.push(PathBuf::from(part_pass));
    }

    let final_passed_vcf = base.config.clairs_passed_vcf(&base.id);
    let rand = Uuid::new_v4();
    let final_tmp = format!("{final_passed_vcf}_{rand}.tmp");
    let final_tmp_csi = format!("{final_passed_vcf}_{rand}.tmp.csi");

    if let Some(parent) = Path::new(&final_passed_vcf).parent() {
        fs::create_dir_all(parent)?;
    }

    info!(
        "Concatenating {} ClairS part VCFs into {}",
        n_parts, final_passed_vcf
    );

    let mut concat = BcftoolsConcat::from_config(&base.config, part_pass_paths, &final_tmp);
    run!(&base.config, &mut concat).context("Failed to run bcftools concat for ClairS parts")?;

    fs::rename(&final_tmp, &final_passed_vcf).context("Failed to rename merged ClairS PASS VCF")?;
    fs::rename(&final_tmp_csi, format!("{final_passed_vcf}.csi"))
        .context("Failed to rename merged ClairS PASS VCF CSI")?;

    info!(
        "Successfully merged {} ClairS parts into {}",
        n_parts, final_passed_vcf
    );

    Ok(())
}

fn merge_clairs_germline_parts(base: &ClairS, n_parts: usize) -> anyhow::Result<()> {
    let mut part_pass_paths: Vec<PathBuf> = Vec::with_capacity(n_parts);

    for i in 1..=n_parts {
        let mut part = base.clone();
        part.part_index = Some(i);
        let part_pass = part.germline_passed_vcf_path();

        anyhow::ensure!(
            Path::new(&part_pass).exists(),
            "Missing ClairS germline part {} PASS VCF: {}",
            i,
            part_pass
        );

        part_pass_paths.push(PathBuf::from(part_pass));
    }

    let final_passed_vcf = base.config.clairs_germline_passed_vcf(&base.id);
    let rand = Uuid::new_v4();
    let final_tmp = format!("{final_passed_vcf}_{rand}.tmp");
    let final_tmp_csi = format!("{final_passed_vcf}_{rand}.tmp.csi");

    if let Some(parent) = Path::new(&final_passed_vcf).parent() {
        fs::create_dir_all(parent)?;
    }

    info!(
        "Concatenating {} ClairS germline part VCFs into {}",
        n_parts, final_passed_vcf
    );

    let mut concat = BcftoolsConcat::from_config(&base.config, part_pass_paths, &final_tmp);
    run!(&base.config, &mut concat)
        .context("Failed to run bcftools concat for ClairS germline parts")?;

    fs::rename(&final_tmp, &final_passed_vcf)
        .context("Failed to rename merged ClairS germline PASS VCF")?;

    fs::rename(&final_tmp_csi, format!("{final_passed_vcf}.csi"))
        .context("Failed to rename merged ClairS germline PASS VCF CSI")?;

    info!(
        "Successfully merged {} ClairS germline parts into {}",
        n_parts, final_passed_vcf
    );

    Ok(())
}

pub fn merge_haplotaged_tmp_bam(config: &Config, id: &str) -> anyhow::Result<()> {
    let dir = config.clairs_output_dir(id);
    let bams: Vec<PathBuf> = list_files_recursive(dir)
        .into_iter()
        .filter(|f| f.extension().and_then(|e| e.to_str()) == Some("bam"))
        .collect();

    let into = Path::new(&config.tumoral_haplotagged_bam(id)).to_path_buf();
    info!("Merging {} into: {}", bams.len(), into.display());
    let mut merge = SamtoolsMergeMany::from_config(into, bams, config);
    run!(config, &mut merge)?;
    Ok(())
}

/// Runs ClairS in parallel chunks, then merges results.
///
/// Splits the genome into N equal-sized regions, runs ClairS on each region
/// in parallel (local or Slurm based on `config.slurm_runner`), post-processes
/// each part (concatenates SNV+indel, filters PASS), and merges both somatic
/// and germline VCFs.
///
/// # Arguments
///
/// * `id` - Sample identifier
/// * `config` - Global pipeline configuration
/// * `n_parts` - Number of parallel chunks (typically 20-30 for whole-genome)
///
/// # Returns
///
/// `Ok(())` on success, or an error if any step fails.
///
/// # Errors
///
/// Returns an error if:
/// - `n_parts` is 0
/// - Normal BAM file cannot be opened or is corrupted
/// - BAM header is malformed
/// - ClairS execution fails on any part
/// - SNV+indel concatenation fails
/// - PASS filtering fails
/// - Somatic or germline VCF merging fails
/// - Output directory cannot be created
///
/// # Example
///
/// ```ignore
/// let config = Config::default();
/// run_clairs_chunked("sample_001", &config, 30)?;
/// ```
pub fn run_clairs_chunked(id: &str, config: &Config, n_parts: usize) -> anyhow::Result<()> {
    anyhow::ensure!(n_parts > 0, "run_clairs_chunked: n_parts must be > 0");

    let lock_dir = format!("{}/locks", config.result_dir);
    let _lock = SampleLock::acquire(&lock_dir, id, "clairs")
        .with_context(|| format!("Cannot start ClairS chunked for {}", id))?;

    let base = ClairS::initialize(id, config)?;

    if !base.should_run() {
        debug!("ClairS PASS VCF already up-to-date for {id}, skipping.");
        return Ok(());
    }

    let normal_bam = config.normal_bam(id);
    let reader = bam::Reader::from_path(&normal_bam)
        .with_context(|| format!("Failed to open BAM: {normal_bam}"))?;
    let header = bam::Header::from_template(reader.header());
    let genome_sizes = get_genome_sizes(&header)?;
    let regions = split_genome_into_n_regions_exact(&genome_sizes, n_parts)
        .into_iter()
        .flatten()
        .collect::<Vec<String>>();

    let actual_n_parts = regions.len();

    info!(
        "Running ClairS in {} parallel parts for {}",
        actual_n_parts, id
    );

    let mut jobs = Vec::with_capacity(actual_n_parts);
    for (i, region) in regions.into_iter().enumerate() {
        let mut job = base.clone();
        job.part_index = Some(i + 1);
        job.region = Some(region);
        job.log_dir = format!("{}/part{}", base.log_dir, i + 1);
        info!("Planned ClairS job:\n{job}");
        jobs.push(job);
    }

    let outputs = run_many!(config, jobs.clone())?;

    for output in outputs.iter() {
        output.save_to_file(format!("{}/clairs_", base.log_dir))?;
    }

    // 1) Germline PASS filters (one per part)
    let mut germlines = Vec::new();

    // 2a) Somatic SNV+indel concats (one per part)
    let mut somatic_concats = Vec::new();
    let mut somatic_tmp_paths = Vec::new();

    for job in &jobs {
        // germline PASS
        germlines.push(job.process_germline()?);

        // somatic concat (SNV+indel -> tmp VCF)
        let (concat, tmp_path) = job.process_somatic_concat()?;
        somatic_concats.push(concat);
        somatic_tmp_paths.push(tmp_path);
    }

    // Run all germline PASS filters in parallel
    run_many!(config, germlines)?;

    // Run all somatic concats in parallel
    run_many!(config, somatic_concats)?;

    // 2b) Somatic PASS filters (one per part, based on tmp VCFs)
    let mut somatic_pass_filters = Vec::new();
    for (job, tmp_path) in jobs.iter().zip(somatic_tmp_paths.iter()) {
        somatic_pass_filters.push(job.process_somatic_pass(tmp_path)?);
    }

    // Run all somatic PASS filters in parallel
    run_many!(config, somatic_pass_filters)?;

    merge_clairs_parts(&base, actual_n_parts)?;
    merge_clairs_germline_parts(&base, actual_n_parts)?;

    info!(
        "ClairS completed for {}: {} parts merged (somatic + germline)",
        id, actual_n_parts
    );

    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::helpers::test_init;

    #[test]
    fn clairs_version() -> anyhow::Result<()> {
        test_init();
        let vl = ClairS::version(&Config::default())?;
        info!("ClairS local version: {vl}");
        let vs = ClairS::version_slurm(&Config::default())?;
        info!("ClairS slurm version: {vs}");
        assert_eq!(vl, vs);
        Ok(())
    }

    #[test]
    fn clairs_run() -> anyhow::Result<()> {
        test_init();
        let config = Config::default();
        // let clairs = ClairS::initialize("34528", &config)?;
        // info!("{clairs}");

        run_clairs_chunked("CHAHA", &config, 50)?;

        Ok(())
    }

    #[test]
    fn clairs_haplo() -> anyhow::Result<()> {
        test_init();
        let config = Config::default();

        merge_haplotaged_tmp_bam(&config, "DUMCO")?;
        Ok(())
    }
}