//
// Check input samplesheet and get read channels
//


include { FASTP as FASTP_SINGLE       } from '../../modules/nf-core/modules/fastp/main'
include { FASTP as FASTP_PAIRED       } from '../../modules/nf-core/modules/fastp/main'
include { FASTQC as FASTQC_POST       } from '../../modules/nf-core/modules/fastqc/main'

workflow FASTQ_PREPROCESSING {
    take:
    reads // file: /path/to/samplesheet.csv

    main:
    ch_versions = Channel.empty()
    ch_multiqc_files      = Channel.empty()

    //
    // STEP: Read clipping and merging
    //
    // TODO give option to clip only and retain pairs
    // TODO give option to retain singletons (probably fastp option likely)
    // TODO move to subworkflow


    if ( params.fastp_clip_merge ) {

        ch_input_for_fastp = reads
                                .dump(tag: "pre-fastp_branch")
                                .branch{
                                    single: it[0]['single_end'] == true
                                    paired: it[0]['single_end'] == false
                                }

        ch_input_for_fastp.single.dump(tag: "input_fastp_single")
        ch_input_for_fastp.paired.dump(tag: "input_fastp_paired")

        FASTP_SINGLE ( ch_input_for_fastp.single, false, false )
        FASTP_PAIRED ( ch_input_for_fastp.paired, false, true )

        ch_fastp_reads_prepped = FASTP_PAIRED.out.reads_merged
                                    .mix( FASTP_SINGLE.out.reads )
                                    .map {
                                        meta, reads ->
                                        def meta_new = meta.clone()
                                        meta_new['single_end'] = 1
                                        [ meta_new, reads ]
                                    }

        FASTQC_POST ( ch_fastp_reads_prepped )

        ch_versions = ch_versions.mix(FASTP_SINGLE.out.versions.first())
        ch_versions = ch_versions.mix(FASTP_PAIRED.out.versions.first())

        ch_processed_reads = ch_fastp_reads_prepped

        ch_multiqc_files = ch_multiqc_files.mix( FASTQC_POST.out.zip.collect{it[1]} )
        ch_multiqc_files = ch_multiqc_files.mix( FASTP_SINGLE.out.json.collect{it[1]} )
        ch_multiqc_files = ch_multiqc_files.mix( FASTP_PAIRED.out.json.collect{it[1]} )

        ch_multiqc_files.dump(tag: "preprocessing_mqc_final")

    } else {
        ch_processed_reads = reads
    }


    emit:
    reads    = ch_processed_reads   // channel: [ val(meta), [ reads ] ]
    versions = ch_versions          // channel: [ versions.yml ]
    mqc      = ch_multiqc_files
}