needs lib/struct lib/psrs lib/time lib/diag io/log
unit mem/logroll

struct LogRollItem {
  uint ts ;
  *LogEvent event ;
  [void,0] args ;
}

struct LogRoll {
  uint maxargs rowcnt logcnt ;
  [void,0] buf( ;
}

: rowsz ( lr -- n ) maxargs 4* 8+ ;
: bufsz ( lr -- n ) bi rowcnt | rowsz * ;
: newlogroll ( rowcnt maxargs -- lr ) 0 rot> 3 n,@ dup bufsz allot ;
: idx>item ( idx lr -- lri A=lr ) A! rowcnt mod A> rowsz * A> buf( + ;
: actualnargs ( event lr -- ) maxargs swap nargs min ;
: logroll ( ... logevent lr -- ... logevent )
  doto logcnt dup 1+ | ( ... event olcnt A=lr )
  A> idx>item
  over A> actualnargs ( ... event a nargs )
  now rot !+ ( ... event nargs a+4 )
  >A 1+ ps[] A> swap move ;

: .logroll ( n lr -- )
  r! rowcnt min V1 logcnt tuck swap- max0 ( maxidx idx V1=lr )
  do i V1 idx>item dup ts .time spc> ( lri V1=lr )
    dup event LogEvent.name stype spc>
    dup args swap event V1 actualnargs spit[] nl> loop rdrop ;