const CHAR_SET = [ 'nnwwn' , 'wnnnw' , 'nwnnw' , 'wwnnn' , 'nnwnw' , 'wnwnn' , 'nwwnn' , 'nnnww' , 'wnnwn' , 'nwnwn' , ] ; export function decoder ( lines , type ? ) { const code = [ ] ; const barThreshold = Math . ceil ( lines . reduce ( ( pre , item ) => ( pre + item ) / 2 , 0 ) ) ; if ( type === 'interleaved' ) { const startChar = lines . splice ( 0 , 4 ) . map ( ( line ) => ( line > barThreshold ? 'w' : 'n' ) ) . join ( '' ) ; const endChar = lines . splice ( lines . length - 3 , 3 ) . map ( ( line ) => ( line > barThreshold ? 'w' : 'n' ) ) . join ( '' ) ; if ( startChar !== 'nnnn' || endChar !== 'wnn' ) return '' ; while ( lines . length > 0 ) { const seg = lines . splice ( 0 , 10 ) ; const a = seg . filter ( ( item , index ) => index % 2 === 0 ) . map ( line => ( line > barThreshold ? 'w' : 'n' ) ) . join ( '' ) ; code . push ( CHAR_SET . indexOf ( a ) ) ; const b = seg . filter ( ( item , index ) => index % 2 !== 0 ) . map ( line => ( line > barThreshold ? 'w' : 'n' ) ) . join ( '' ) ; code . push ( CHAR_SET . indexOf ( b ) ) ; } } else { const startChar = lines . splice ( 0 , 6 ) . filter ( ( item , index ) => index % 2 === 0 ) . map ( ( line ) => ( line > barThreshold ? 'w' : 'n' ) ) . join ( '' ) ; const endChar = lines . splice ( lines . length - 5 , 5 ) . filter ( ( item , index ) => index % 2 === 0 ) . map ( ( line ) => ( line > barThreshold ? 'w' : 'n' ) ) . join ( '' ) ; if ( startChar !== 'wwn' || endChar !== 'wnw' ) return '' ; while ( lines . length > 0 ) { const a = lines . splice ( 0 , 10 ) . filter ( ( item , index ) => index % 2 === 0 ) . map ( line => ( line > barThreshold ? 'w' : 'n' ) ) . join ( '' ) ; code . push ( CHAR_SET . indexOf ( a ) ) ; } } return code . join ( '' ) ; }