Simplified bam_bai joining

    SAMTOOLS_INDEX ( out_bam )

    // Join bam/bai

    ch_bam_sample_id = out_bam.map                { row -> [row[0].id, row] }

    ch_bai_sample_id = SAMTOOLS_INDEX.out.bai.map { row -> [row[0].id, row] }

    ch_bam_bai = ch_bam_sample_id.join(ch_bai_sample_id, by: [0]).map {row -> [row[1][0], row[1][1], row[2][1]]}

    out_bam

        .map { row -> [row[0].id, row ].flatten()}

        .join ( SAMTOOLS_INDEX.out.bai.map { row -> [row[0].id, row ].flatten()} )

        .map { row -> [row[1], row[2], row[4]] }

        .set { ch_bam_bai }

    //ch_bam_bai | view

    /*

    * Run samtools stats, flagstat and idxstats