use crate::{
    annotation::is_gnomad_and_constit_alt,
    create_should_run_normal_tumoral, init_solo_callers_normal_tumoral,
    io::bed::read_bed,
    pipes::{Initialize, InitializeSolo, ShouldRun},
    positions::{GenomeRange, GenomeRangeExt},
    scan::scan::SomaticScan,
    variant::{
        variants_stats::somatic_depth_quality_ranges,
        vcf_variant::{run_if_required, ShouldRunBox},
    },
};
use log::info;
use rayon::slice::ParallelSliceMut;
use serde::Serialize;
use std::{
    collections::BTreeMap,
    fs::{self, File},
    path::{Path, PathBuf},
};

use crate::{
    annotation::{Annotation, Annotations, AnnotationsStats, Sample},
    callers::{
        clairs::ClairS, deep_somatic::DeepSomatic, deep_variant::DeepVariant, nanomonsv::NanomonSV,
        savana::Savana, severus::Severus,
    },
    config::Config,
    create_should_run, init_somatic_callers,
    runners::Run,
    variant::{
        variant_collection::{ExternalAnnotation, VariantCollection, Variants},
        variants_stats::VariantsStats,
        vcf_variant::{load_variants, CallerBox},
    },
};

/// Runs the full somatic variant calling pipeline for a single sample (`id`).
///
/// This function orchestrates the entire somatic variant discovery process,
/// starting from raw variant caller outputs (`PASSED VCF`) and applying multiple filtering
/// and annotation steps to produce high-confidence somatic variants.
///
/// This function orchestrates the end-to-end somatic variant discovery process:
/// - Executes and verifies upstream components if necessary
/// - Loads variants from multiple callers (tumor and normal samples)
/// - Applies several annotation and filtering steps (e.g. depth, population frequency, entropy)
/// - Tracks filtering statistics at each step
/// - Outputs high-confidence somatic variants in both `.json.gz` and `.bit` formats
///
/// ## Output Overview
/// The final output includes:
/// - `{tumoral_dir}/{id}_somatic_variants.json.gz`: annotated somatic variants
/// - `{tumoral_dir}/{id}_somatic_variants.bit`: compact binary variant representation
/// - `{stats_dir}/`: multiple intermediate JSON files with annotations and statistics
///
/// ## Steps
///
/// This pipeline performs the following high-level steps:
///
/// ### 1. Output Existence Check
/// If the final JSON result already exists and [`Config::somatic_pipe_force`] is not set,
/// the pipeline aborts early to avoid overwriting results.
///
/// ### 2. Initialization
/// - Prepares statistics and output directories.
/// - Initializes variant annotations.
///
/// ### 3. Pre-requisite Tool Execution
/// Runs any required upstream components (e.g., alignment, basecalling, variant callers) if
/// their outputs are missing, using the [`run_if_required`] logic.
///
/// ### 4. Load Variant Collections
/// - Initializes the configured somatic variant callers and loads their output variants from PASSED VCF.
/// - Also loads germline variants (from [`ClairS::germline`]) for comparative germline filtering.
///
/// ### 5. Statistics Initialization
/// - Initializes a [`SomaticPipeStats`] object to track the number of variants at each step.
/// - Captures initial variant counts before filtering.
/// - Aggregates variant counts from all sources and stores initial annotations for quality control and
///   comparison before filtering.
///
/// ### 6. Filter: Germline & Solo Constitutional Variants
/// - Removes variants labeled as either Germline or Solo Constitutional, assuming they are unlikely to be somatic.
/// - Records count of removed variants in [`SomaticPipeStats::n_constit_germline`].
///
/// ### 7. Annotation: BAM Read Depth and Alt Allele Counts
/// - Uses the constitutional BAM file to annotate each variant with read depth and the number of alternate reads observed.
/// - Flags variants with low depth or excessive alt reads for filtering as specified in [`Config`].
///
/// ### 8. Filtering: Low Depth / High Alt Alleles
/// - Removes variants with low coverage in the constitutional sample, or excessive alt allele support (suggestive of germline origin).
/// - Updates stats:
///   - [`SomaticPipeStats::n_low_constit`]
///   - [`SomaticPipeStats::n_high_alt_constit`]
///
/// ### 9. Annotation: Sequence Entropy
/// Adds Shannon entropy annotation based on the reference sequence context
/// around each variant (cf. [`Config::entropy_seq_len`]) to flag low-complexity regions (often repetitive).
///
/// ### 10. Annotation: External Databases (COSMIC, GnomAD):
///  - Uses external resources to annotate variants with:
///    - COSMIC hits (somatic mutation database)
///    - GnomAD allele frequencies
///
/// ### 11. Filtering: GnomAD + Alt Support in Constitutional Sample
///  - Removes variants that are both present in GnomAD **and** show
///    alternate allele support in the constitutional BAM.
///    These are highly likely to be non-somatic germline polymorphisms.
///  - Updates [`SomaticPipeStats::n_high_alt_constit_gnomad`] stat.
///
/// ### 12. Filtering: Low Shannon Entropy:
///  - Removes variants from low-complexity regions with entropy below the configured threshold
///    (cf. [`Config::min_shannon_entropy`]).
///  - Updates [`SomaticPipeStats::n_low_entropies`].
///
/// ### 13. Annotation: VEP (Variant Effect Predictor)
///  Adds transcript-level annotations from Ensembl VEP, providing functional consequences,
///  impacted genes, and regulatory features.
///
/// ### 14. Merging
///  Merges variant collections into a unified [`Variants`] structure,
///  preserving annotations and applying deduplication logic.
///
/// ### 15. Final Statistics and Saving
///  - Saves final annotation stats, VEP summaries, and variant-level statistics.
///  - Exports the final somatic variant set to both compressed JSON and `.bit` formats.
///
/// # Returns
/// - `Ok(())` if all steps completed successfully.
/// - `Err` if any tool fails, if file I/O fails, or if logical conditions are violated (e.g., pre-existing output).
///
/// # Errors
/// - Returns early if the output file already exists and [`Config::somatic_pipe_force`] is `false`.
/// - Wraps all component-specific errors using `anyhow::Result` with context.
///
/// # Side Effects
/// - Runs external tools conditionally (e.g., [`ClairS`], [`DeepSomatic`]).
/// - Creates intermediate directories and annotation JSONs for debugging/QC.
/// - May consume significant compute time depending on the number of callers, annotations, and variants.
///
/// # TODOs
/// - Support compressed intermediate files (`// TODO: GZ !!!`)
/// - Improve filtering metrics reporting (currently not all filtered variants are tracked in final stats).
///
/// # Example Output Files
/// - `tumoral_dir/sample123_somatic_variants.json.gz`
/// - `tumoral_dir/sample123_somatic_variants.bit`
/// - `stats_dir/sample123_annotations_*.json` (intermediate annotation snapshots)
///
/// # See Also
/// - [`Annotations`] – core structure for managing per-variant metadata
/// - [`Variants`] – the merged final variant structure
/// - [`SomaticPipeStats`] – used for tracking variant counts throughout filtering
///
pub struct SomaticPipe {
    /// Unique identifier for the sample.
    pub id: String,
    /// Configuration parameters for the pipeline.
    pub config: Config,
}

impl Initialize for SomaticPipe {
    /// Initializes a new `Somatic` instance with default annotations.
    fn initialize(id: &str, config: &crate::config::Config) -> anyhow::Result<Self> {
        let id = id.to_string();
        Ok(Self {
            id,
            config: config.clone(),
        })
    }
}

impl ShouldRun for SomaticPipe {
    fn should_run(&self) -> bool {
        // path to the existing “.bit” file
        let tumoral_dir = self.config.tumoral_dir(&self.id);
        let bit_path = Path::new(&tumoral_dir).join(format!("{}_somatic_variants.bit", self.id));

        // if we can’t read its modification time, re-run
        let res_meta = match fs::metadata(&bit_path).and_then(|m| m.modified()) {
            Ok(ts) => ts,
            Err(_) => return true,
        };

        let deps: [PathBuf; 5] = [
            Path::new(&self.config.normal_bam(&self.id)).to_path_buf(),
            Path::new(&self.config.tumoral_bam(&self.id)).to_path_buf(),
            Path::new(&self.config.reference).to_path_buf(),
            Path::new(&self.config.vntrs_bed).to_path_buf(),
            Path::new(&self.config.repeats_bed).to_path_buf(),
        ];

        deps.iter().any(|p| {
            fs::metadata(p)
                .and_then(|m| m.modified())
                .map_or(true, |ts| ts > res_meta)
        })
    }
}

impl Run for SomaticPipe {
    /// Executes the full somatic variant analysis pipeline.
    fn run(&mut self) -> anyhow::Result<()> {
        let config = self.config.clone();
        let id = self.id.clone();
        info!("Running somatic pipe for {id}.");

        // Define output paths for the final somatic variants
        let result_json = format!("{}/{id}_somatic_variants.json.gz", config.tumoral_dir(&id));
        let result_bit = format!("{}/{id}_somatic_variants.bit", config.tumoral_dir(&id));
        let result_vcf = format!("{}/{id}_somatic_variants.vcf.gz", config.tumoral_dir(&id));

        let outputs = [&result_json, &result_bit, &result_vcf];
        if !config.somatic_pipe_force && outputs.iter().any(|p| Path::new(p).exists()) {
            return Err(anyhow::anyhow!(
                "Somatic Pipe output already exists for {id}."
            ));
        }

        let mut annotations = Annotations::default();

        // Create stats directory if it doesn't exist
        let stats_dir = config.somatic_pipe_stats(&id);
        if !Path::new(&stats_dir).exists() {
            fs::create_dir(&stats_dir)?;
        }

        // Initialize and run any pre-required input if necessary
        info!("Initialization prerequired pipe inputs...");

        let mut to_run_if_req = create_should_run!(
            &id,
            &config,
            SomaticScan,
            ClairS,
            NanomonSV,
            Severus,
            Savana,
            DeepSomatic
        );
        to_run_if_req.extend(create_should_run_normal_tumoral!(&id, &config, DeepVariant));

        info!("Running prerequired pipe components.");
        run_if_required(&mut to_run_if_req).map_err(|e| {
            anyhow::anyhow!("Failed to run a prerequired component of somatic pipe for {id}.\n{e}")
        })?;

        // Initialize variant callers
        let mut callers = init_somatic_callers!(
            &id,
            &config,
            ClairS,
            NanomonSV,
            Severus,
            Savana,
            DeepSomatic
        );

        callers.extend(init_solo_callers_normal_tumoral!(&id, &config, DeepVariant,));

        // Load variants from each caller
        info!("Loading variants.");
        let mut variants_collections = load_variants(&mut callers, &annotations)
            .map_err(|e| anyhow::anyhow!("Error while loading variants\n{e}"))?;

        // Load germline variants using ClairS
        info!("Loading germline variants.");
        let clairs_germline =
            ClairS::initialize(&id, &self.config.clone())?.germline(&annotations)?;
        variants_collections.push(clairs_germline);

        // Initialize statistics
        let mut somatic_stats = SomaticPipeStats::init(&variants_collections);
        info!(
            "Variants collections loaded from {} vcf (total of {} variants loaded)",
            variants_collections.len(),
            variants_collections
                .iter()
                .map(|v| v.variants.len())
                .sum::<usize>()
        );

        // Initial annotation stats (caller annotations only)
        let caller_cat_anns = |v: &Annotation| matches!(v, Annotation::Callers(_, _));
        let annot_init = annotations.callers_stat(Some(Box::new(caller_cat_anns)));
        somatic_stats.annot_init(
            &annot_init,
            &format!("{stats_dir}/{id}_germline_filter.json"),
        )?;
        annot_init.save_to_json(&format!("{stats_dir}/{id}_annotations_01.json"))?;

        // Filter out germline and solo constitutional variants
        info!(
            "Keeping somatic variants (variants neither in solo normal {} nor in germline).",
            config.normal_name
        );
        somatic_stats.n_constit_germline =
            annotations.retain_variants(&mut variants_collections, |anns| {
                !anns.iter().any(|ann| {
                    matches!(
                        ann,
                        Annotation::Callers(_, Sample::Germline)
                            | Annotation::Callers(_, Sample::SoloConstit)
                    )
                })
            });
        annotations
            .callers_stat(Some(Box::new(caller_cat_anns)))
            .save_to_json(&format!(
                "{stats_dir}/{id}_annotations_02_post_germline.json"
            ))?;

        // Remove deletions stretch
        // info!("Removing deletions stretchs:");
        // variants_collections.iter_mut().for_each(|coll| {
        //     let rm = coll.remove_strech();
        //     info!("\t - {} {}: {}", coll.vcf.caller, coll.vcf.time, rm);
        // });

        // MASK mapq
        let (mut high_depth_ranges, mut low_quality_ranges) =
            somatic_depth_quality_ranges(&id, &config)?;

        high_depth_ranges.par_sort_by_key(|r| (r.contig, r.range.start));
        low_quality_ranges.par_sort_by_key(|r| (r.contig, r.range.start));

        info!(
            "High-depth ranges: n={} bp={}",
            high_depth_ranges.len(),
            high_depth_ranges.total_len(),
        );

        info!(
            "LowQ ranges: n={} bp={}",
            low_quality_ranges.len(),
            low_quality_ranges.total_len(),
        );

        variants_collections.iter_mut().for_each(|e| {
            let _ = e.annotate_with_ranges(&low_quality_ranges, &annotations, Annotation::LowMAPQ);
        });
        let n_masked_lowqual = annotations.retain_variants(&mut variants_collections, |anns| {
            !anns.contains(&Annotation::LowMAPQ)
        });
        info!("N low mapq filtered: {}", n_masked_lowqual);

        // Annotate with depth and number of alternate reads from constitutional BAM
        info!("Reading Constit BAM file for depth and pileup annotation.");
        variants_collections.iter().try_for_each(|c| {
            c.annotate_with_constit_bam(&annotations, &self.config.normal_bam(&id), 150)
        })?;
        annotations.somatic_constit_boundaries(
            self.config.somatic_max_alt_constit,
            self.config.somatic_min_constit_depth,
        );
        annotations
            .callers_stat(Some(Box::new(|v| {
                matches!(
                    v,
                    Annotation::Callers(_, _)
                        | Annotation::ConstitAlt(_)
                        | Annotation::ConstitDepth(_)
                        | Annotation::HighConstitAlt
                        | Annotation::LowConstitDepth
                )
            })))
            .save_to_json(&format!("{stats_dir}/{id}_annotations_03_bam.json"))?;

        // Filter based on low constitutional depth
        info!(
            "Removing variants when depth in constit bam < {}.",
            self.config.somatic_min_constit_depth
        );
        somatic_stats.n_low_constit = annotations
            .retain_variants(&mut variants_collections, |anns| {
                !anns.contains(&Annotation::LowConstitDepth)
            });
        info!(
            "{} variants removed when depth in constit bam < {}.",
            somatic_stats.n_low_constit, self.config.somatic_min_constit_depth
        );

        // Filter: remove HighConstitAlt
        info!(
            "Removing variants with SNP/indel inside the constit alignements > {}",
            self.config.somatic_max_alt_constit
        );
        somatic_stats.n_high_alt_constit = annotations
            .retain_variants(&mut variants_collections, |anns| {
                !anns.contains(&Annotation::HighConstitAlt)
            });
        info!(
            "{} variants removed with SNP/indel inside the constit alignements > {}",
            somatic_stats.n_high_alt_constit, self.config.somatic_max_alt_constit
        );

        annotations
            .callers_stat(Some(Box::new(|v| {
                matches!(
                    v,
                    Annotation::Callers(_, _)
                        | Annotation::ConstitAlt(_)
                        | Annotation::ConstitDepth(_)
                )
            })))
            .save_to_json(&format!("{stats_dir}/{id}_annotations_04_bam_filter.json"))?;

        // Annotate variants with sequence context (entropy + trinucleotide)
        info!(
            "Annotating variants with sequence context using reference: {}",
            self.config.reference
        );

        variants_collections.iter().try_for_each(|c| {
            c.annotate_with_sequence_context(
                &annotations,
                &self.config.reference,
                self.config.entropy_seq_len,
                self.config.somatic_pipe_threads,
            )
        })?;

        // Annotate with external databases like COSMIC and GnomAD
        info!("Annotation with external databases like COSMIC and GnomAD.");
        variants_collections
            .iter()
            .try_for_each(|c| -> anyhow::Result<()> {
                let ext_annot = ExternalAnnotation::init(&config)?;
                ext_annot.annotate(&c.variants, &annotations)?;
                Ok(())
            })?;
        annotations
            .callers_stat(Some(Box::new(|v| {
                matches!(
                    v,
                    Annotation::Callers(_, _) | Annotation::ConstitAlt(_) | Annotation::GnomAD(_)
                )
            })))
            .save_to_json(&format!("{stats_dir}/{id}_annotations_05_gnomad.json"))?;

        // Filter: Remove variants present in GnomAD and have alt reads in constitutional sample
        info!("Filtering out variants in GnomAD and in constit bam at low AF.");
        somatic_stats.n_high_alt_constit_gnomad = annotations
            .retain_variants(&mut variants_collections, |anns| {
                !is_gnomad_and_constit_alt(anns)
            });

        info!(
            "{} variants filtered, with constit alt <= max contig alt ({}) and in GnomAD.",
            somatic_stats.n_high_alt_constit_gnomad, self.config.somatic_max_alt_constit
        );

        // TODO: These stats doesn't capture filter metrics !!!
        annotations
            .callers_stat(Some(Box::new(|v| {
                matches!(
                    v,
                    Annotation::Callers(_, _) | Annotation::ConstitAlt(_) | Annotation::GnomAD(_)
                )
            })))
            .save_to_json(&format!(
                "{stats_dir}/{id}_annotations_06_gnomad_filter.json"
            ))?;

        // Filter low entropy variants
        annotations.low_shannon_entropy(self.config.min_shannon_entropy);

        info!(
            "Filtering out variants with low entropies ({})",
            config.min_shannon_entropy
        );
        annotations
            .callers_stat(Some(Box::new(|v| {
                matches!(v, Annotation::Callers(_, _) | Annotation::LowEntropy)
            })))
            .save_to_json(&format!("{stats_dir}/{id}_annotations_07_entropy.json"))?;

        somatic_stats.n_low_entropies = annotations
            .retain_variants(&mut variants_collections, |anns| {
                !anns.contains(&Annotation::LowEntropy)
            });

        annotations
            .callers_stat(Some(Box::new(|v| matches!(v, Annotation::Callers(_, _)))))
            .save_to_json(&format!(
                "{stats_dir}/{id}_annotations_08_entropy_filter.json"
            ))?;

        // Final VEP annotation
        info!("Annotation with VEP.");
        variants_collections
            .iter()
            .try_for_each(|c| -> anyhow::Result<()> {
                let ext_annot = ExternalAnnotation::init(&config)?;
                ext_annot.annotate_vep(&c.variants, &annotations)?;
                Ok(())
            })?;

        annotations
            .callers_stat(Some(Box::new(caller_cat_anns)))
            .save_to_json(&format!("{stats_dir}/{id}_annotations_09_vep.json"))?;

        // Merge all variants into a final collection
        let mut variants = variants_collections.into_iter().fold(
            Variants::default(),
            |mut acc, variants_collection| {
                acc.merge(variants_collection, &annotations);
                acc
            },
        );

        let vep_stats = annotations.vep_stats()?;
        vep_stats.save_to_json(&format!("{stats_dir}/{id}_annotations_10_vep.json"))?;

        VariantsStats::new(&mut variants, &id, &config, &high_depth_ranges)?
            .save_to_json(&format!("{stats_dir}/{id}_variants_stats_final.json.gz"))?;

        info!("Final unique variants: {}", variants.data.len());

        // Ensure sorted (should already be sorted)
        variants.sort();

        let vntrs: Vec<GenomeRange> = read_bed(&config.vntrs_bed)?
            .iter()
            .map(|r| r.range.clone())
            .collect();
        variants.annotate_with_ranges(&vntrs, Some(Annotation::VNTR), 0, Vec::new());

        let repeat_masker: Vec<GenomeRange> = read_bed(&config.repeats_bed)?
            .iter()
            .map(|r| r.range.clone())
            .collect();
        variants.annotate_with_ranges(&repeat_masker, Some(Annotation::Repeat), 0, Vec::new());

        variants.save_to_json(&result_json)?;
        variants.save_to_file(&result_bit)?;
        variants.write_vcf(&result_vcf, &config.dict_file, config.somatic_pipe_force)?;

        Ok(())
    }
}

pub fn const_stats(id: String, config: Config) -> anyhow::Result<()> {
    info!("Loading Germline");
    let annotations = Annotations::default();
    let clairs_germline = ClairS::initialize(&id, &config.clone())?.germline(&annotations)?;

    info!("Annotation with Cosmic and GnomAD.");
    let ext_annot = ExternalAnnotation::init(&config)?;
    ext_annot.annotate(&clairs_germline.variants, &annotations)?;

    let mut variants = Variants::default();
    variants.merge(clairs_germline, &annotations);
    info!("-- {}", variants.data.len());

    // let u = VariantsStats::new(&mut variants, &id, &config)?;
    // info!("++ {}", u.n);

    Ok(())
}

/// Holds statistical data for somatic variant pipeline processing,
/// including summary counts and input categorization.
#[derive(Debug, Default, Clone)]
pub struct SomaticPipeStats {
    /// Summary of input variant collections grouped by sample type.
    pub input: InputStats,

    /// Number of variants removed because they were classified as germline
    /// by at least one caller, or detected in the normal-only (solo constitutional)
    /// callset (including variants classified as both).
    pub n_constit_germline: usize,

    /// Number of variants removed due to low depth in the constitutional (normal) BAM
    /// (i.e. annotated with [`Annotation::LowConstitDepth`]).
    pub n_low_constit: usize,

    /// Number of variants removed due to excessive alternate-allele support in the
    /// constitutional (normal) BAM (i.e. annotated with [`Annotation::HighConstitAlt`]).
    pub n_high_alt_constit: usize,

    /// Number of variants removed because they are present in gnomAD and also show
    /// alternate-allele support in the constitutional (normal) BAM, according to
    /// [`is_gnomad_and_constit_alt`].
    pub n_high_alt_constit_gnomad: usize,

    /// Number of variants removed due to low sequence complexity (Shannon entropy),
    /// i.e. annotated with [`Annotation::LowEntropy`].
    pub n_low_entropies: usize,
}

impl SomaticPipeStats {
    /// Initializes a `SomaticPipeStats` object with populated `InputStats` based on the
    /// provided `VariantCollection`s.
    pub fn init(collections: &[VariantCollection]) -> Self {
        Self {
            input: InputStats::from_collections(collections),
            ..Default::default()
        }
    }

    /// Generates a tumor-vs-germline annotation matrix and writes it to a JSON file.
    ///
    /// This method analyzes co-occurrence patterns between tumor and germline/constit
    /// variant callers by iterating through annotation statistics from `AnnotationsStats`.
    /// It builds a matrix where each row corresponds to a **tumor caller** and each column
    /// corresponds to a **germline or constitutional caller**. Each cell contains the number
    /// of variant calls that were annotated by both the tumor and the germline/constit caller.
    ///
    /// In addition to writing a structured JSON file to the specified path, the function also
    /// prints a tab-separated human-readable matrix to stdout for convenience.
    ///
    /// # Parameters
    ///
    /// - `stats`: A reference to [`AnnotationsStats`] containing categorical annotations.
    ///   This object holds a frequency map where keys are combinations of `Annotation`
    ///   values (serialized as strings) and values are occurrence counts.
    /// - `json_path`: The path where the resulting JSON output file should be written.
    ///
    /// # Output Formats
    ///
    /// ## JSON Output (`json_path`)
    ///
    /// The output JSON is an **array of tumor caller records**, each containing:
    /// - `caller_name`: The name of the tumor caller (as a string).
    /// - `germline`: An array of JSON objects, each with one key-value pair,
    ///   where the key is a germline/constit caller (or combination) and the value is the count.
    ///
    /// ### Example
    /// ```json
    /// [
    ///   {
    ///     "caller_name": "DeepVariant SoloTumor",
    ///     "germline": {
    ///       "ClairS Germline": 99978,
    ///       "ClairS Germline + DeepVariant SoloConstit": 4710570
    ///     }
    ///   },
    ///   {
    ///     "caller_name": "ClairS Somatic",
    ///     "germline": {
    ///       "ClairS Germline": 944,
    ///       "ClairS Germline + DeepVariant SoloConstit": 362
    ///     }
    ///   }
    /// ]
    /// ```
    ///
    /// ## Console Output (TSV)
    ///
    /// A tab-separated matrix is printed to stdout. Each row begins with a tumor caller,
    /// followed by columns showing germline/constit caller combinations and their counts.
    ///
    /// # Notes
    /// - Tumor callers are collected from `self.input.somatic` and `self.input.solo_tumor`.
    /// - Germline/constit callers are collected from `self.input.germline` and `self.input.solo_constit`.
    /// - Keys in the original `AnnotationsStats` map are split using `" + "` and parsed into `Annotation` enums.
    /// - Germline keys are sorted and joined to form canonical column labels.
    /// - Tumor and germline annotations are matched by exact `Annotation` equality.
    ///
    /// # Errors
    /// Returns an error if:
    /// - Any annotation key in `AnnotationsStats` fails to parse into a valid `Annotation`.
    /// - The JSON output file cannot be created or written to.
    ///
    /// # Dependencies
    /// Requires that `Annotation` implements `FromStr`, `ToString`, `PartialEq`, and `Clone`.
    ///
    /// # Example Usage
    /// ```rust
    /// let mut stats = SomaticPipeStats::init(&collections);
    /// stats.annot_init(&annotation_stats, "output/matrix.json")?;
    /// ```
    pub fn annot_init(&self, stats: &AnnotationsStats, json_path: &str) -> anyhow::Result<()> {
        #[derive(Serialize)]
        struct TumorRow {
            caller_name: String,
            germline: BTreeMap<String, u64>,
        }

        // Parse stats keys into Vec<Annotation> once
        let parsed: Vec<(Vec<Annotation>, u64)> = stats
            .categorical
            .iter()
            .map(|e| {
                let anns = e
                    .key()
                    .split(" + ")
                    .map(|k| k.parse::<Annotation>())
                    .collect::<anyhow::Result<Vec<_>>>()
                    .map_err(|err| {
                        anyhow::anyhow!("Error while parsing AnnotationsStats key: {err}")
                    })?;
                Ok((anns, *e.value()))
            })
            .collect::<anyhow::Result<_>>()?;

        // Collect caller labels
        let tumor_callers: Vec<Annotation> = self
            .input
            .somatic
            .iter()
            .map(|(a, _)| a.clone())
            .chain(self.input.solo_tumor.iter().map(|(a, _)| a.clone()))
            .collect();

        let germ_callers: Vec<Annotation> = self
            .input
            .germline
            .iter()
            .map(|(a, _)| a.clone())
            .chain(self.input.solo_constit.iter().map(|(a, _)| a.clone()))
            .collect();

        // Matrix: tumor -> (germline label -> count), deterministic by construction
        let mut matrix: BTreeMap<String, BTreeMap<String, u64>> = BTreeMap::new();

        for (anns, v) in parsed.iter() {
            // only rows that include any germline/constit label
            if !anns.iter().any(|a| {
                matches!(
                    a,
                    Annotation::Callers(_, Sample::SoloConstit)
                        | Annotation::Callers(_, Sample::Germline)
                )
            }) {
                continue;
            }

            // Which tumor callers are present in this set?
            let present_tumors: Vec<String> = tumor_callers
                .iter()
                .filter(|t| anns.contains(t))
                .map(|t| t.to_string())
                .collect();

            if present_tumors.is_empty() {
                continue;
            }

            // Canonical germline key: sorted labels joined by " + "
            let mut present_germs: Vec<String> = germ_callers
                .iter()
                .filter(|g| anns.contains(g))
                .map(|g| g.to_string())
                .collect();
            present_germs.sort();
            let germ_key = present_germs.join(" + ");

            for tumor in present_tumors {
                *matrix
                    .entry(tumor)
                    .or_default()
                    .entry(germ_key.clone())
                    .or_default() += *v;
            }
        }

        // Collect all germline columns (deterministic)
        let mut germ_cols: Vec<String> = matrix
            .values()
            .flat_map(|row| row.keys().cloned())
            .collect();
        germ_cols.sort();
        germ_cols.dedup();

        // TSV output (deterministic ordering)
        let mut lines: Vec<String> = Vec::with_capacity(matrix.len());
        for (tumor, row) in matrix.iter() {
            let line = format!(
                "{tumor}\t{}",
                germ_cols
                    .iter()
                    .map(|g| format!("{g}: {}", row.get(g).copied().unwrap_or(0)))
                    .collect::<Vec<_>>()
                    .join("\t")
            );
            lines.push(line);
        }
        println!("{}", lines.join("\n"));

        // JSON output: list of rows with all columns filled (0 if absent)
        let json_rows: Vec<TumorRow> = matrix
            .iter()
            .map(|(tumor, row)| {
                let mut full = BTreeMap::new();
                for g in germ_cols.iter() {
                    full.insert(g.clone(), row.get(g).copied().unwrap_or(0));
                }
                TumorRow {
                    caller_name: tumor.clone(),
                    germline: full,
                }
            })
            .collect();

        let file = File::create(json_path)?;
        serde_json::to_writer_pretty(file, &json_rows)?;

        Ok(())
    }
}

/// Aggregated statistics on variant collections, grouped by sample type.
///
/// The `InputStats` struct stores the number of variants observed for each
/// caller, categorized by biological sample type:
///
/// - `solo_tumor`: Variants from tumor-only samples.
/// - `solo_constit`: Variants from normal-only (constitutional) samples.
/// - `germline`: Variants classified as germline (shared between normal and tumor).
/// - `somatic`: Variants classified as somatic (tumor-specific).
///
/// Each vector contains tuples of the form `(Annotation, usize)`, where:
/// - `Annotation` identifies the caller and sample type.
/// - `usize` represents the number of variants for that annotation.
#[derive(Debug, Default, Clone)]
pub struct InputStats {
    /// Variants from tumor-only samples.
    pub solo_tumor: Vec<(Annotation, usize)>,

    /// Variants from normal-only (constitutional) samples.
    pub solo_constit: Vec<(Annotation, usize)>,

    /// Germline variants (present in both normal and tumor).
    pub germline: Vec<(Annotation, usize)>,

    /// Somatic variants (specific to tumor).
    pub somatic: Vec<(Annotation, usize)>,
}

impl InputStats {
    /// Constructs an `InputStats` instance by aggregating variant counts
    /// from a list of [`VariantCollection`]s.
    ///
    /// Each `VariantCollection` is inspected to determine its sample type,
    /// as indicated by the `Annotation::Callers(_, Sample)` variant. The
    /// number of variants (`collection.variants.len()`) is recorded in the
    /// appropriate field of `InputStats`, grouped by `Sample`.
    ///
    /// # Parameters
    ///
    /// - `collections`: A slice of [`VariantCollection`] objects containing
    ///   variants annotated with a caller and sample type.
    ///
    /// # Returns
    ///
    /// A populated `InputStats` instance with counts per (caller, sample type).
    ///
    /// # Examples
    ///
    /// ```
    /// let collections: Vec<VariantCollection> = load_collections();
    /// let stats = InputStats::from_collections(&collections);
    /// println!("Somatic calls: {:?}", stats.somatic);
    /// ```
    pub fn from_collections(collections: &[VariantCollection]) -> Self {
        let mut stats = Self::default();
        for collection in collections.iter() {
            match collection.caller {
                Annotation::Callers(_, Sample::SoloTumor) => stats
                    .solo_tumor
                    .push((collection.caller.clone(), collection.variants.len())),
                Annotation::Callers(_, Sample::SoloConstit) => stats
                    .solo_constit
                    .push((collection.caller.clone(), collection.variants.len())),
                Annotation::Callers(_, Sample::Germline) => stats
                    .germline
                    .push((collection.caller.clone(), collection.variants.len())),
                Annotation::Callers(_, Sample::Somatic) => stats
                    .somatic
                    .push((collection.caller.clone(), collection.variants.len())),
                _ => (),
            };
        }
        stats
    }
}

#[cfg(test)]
mod tests {
    use rayon::ThreadPoolBuilder;

    use super::*;
    use crate::helpers::test_init;

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

        let pool = ThreadPoolBuilder::new()
            .num_threads(config.threads.into())
            .build()?;

        pool.install(|| SomaticPipe::initialize("CHAHA", &config)?.run())?;
        Ok(())
    }
}