\ Denial of service protection.
\ TODO: Use hash table instead?

require util.4th

[UNDEFINED] MAX_CONNECTIONS [IF] 32 constant MAX_CONNECTIONS [THEN]

             10 constant DOS_UPDATE_INTERVAL
           1024 constant DOS_BYTES_PER_INTERVAL
             10 constant DOS_LINES_PER_INTERVAL
              3 constant DOS_MAX_CONNECTIONS
MAX_CONNECTIONS constant DOS_MAX_MAPPINGS

\ TODO: is 0 a valid circuit id?
\ TODO: if not, then we could use the circuit id instead of dos.set
0
  cell +field dos.set
  cell +field dos.circuit-id
  cell +field dos.handled
  cell +field dos.connections
  cell +field dos.total-bytes
  cell +field dos.total-lines
  cell +field dos.bytes
  cell +field dos.lines
constant /DOS

/DOS DOS_MAX_MAPPINGS * constant DOS_ARRAY_SIZE
create dos DOS_ARRAY_SIZE alloterase

\ Lookup table: connection index -> dos stats
create doslt DOS_MAX_MAPPINGS cells alloterase

: (translate) ( index-n -- dos-addr )
  /DOS * dos + ;
: (init-dos) ( free-addr circuit-id-n -- dos-addr )
  over dos.circuit-id !
  true over dos.set ! ;
: (find) ( circuit-id-n -- dos-addr )
  0 swap dos DOS_ARRAY_SIZE + dos DO ( -- free-addr circuit-id-n )
    I dos.set @ IF
      dup I dos.circuit-id @ = IF
        2drop I UNLOOP EXIT
      THEN
    ELSE
      over 0= IF
        nip I swap
      THEN
    THEN
  /DOS +LOOP
  (init-dos) ;
: (lttranslate) ( connection-index-n -- lookup-addr )
  cells doslt + ;
: (lookup) ( connection-index-n -- dos-addr )
  (lttranslate) @ ;

: (mod-connections) ( n dos-addr -- ) dos.connections +! ;
: (inc-connections) ( dos-addr -- ) 1 swap (mod-connections) ;
: (dec-connections) ( dos-addr -- ) -1 swap (mod-connections) ;
: dos-add-connection ( circuit-id-n connection-index-n -- )
  (lttranslate) dup @ 0= IF
    swap (find) tuck (inc-connections) !
  ELSE
    2drop EXIT
  THEN ;
: dos-remove-connection ( connection-index-n -- )
\ erase if last connection
  (lttranslate) dup 0<> IF
    dup @ >r 0 swap ! r>
    dup (dec-connections)
    dup dos.connections @ 0= IF
      /DOS erase
    ELSE
      drop
    THEN
  ELSE
    drop
  THEN ;
: dos-add-bytes ( bytes-n connection-index-n -- )
  (lookup) dos.bytes +! ;
: dos-add-lines ( lines-n connection-index-n -- )
  (lookup) dos.lines +! ;
: (update) ( dos-addr -- )
  dup dos.bytes @ over dos.total-bytes +!
  dup dos.lines @ over dos.total-lines +!
  0 over dos.bytes !
  0 over dos.lines !
  drop ;
: dos-update ( -- )
\ add time interval bytes and lines to total and set to 0
  dos DOS_ARRAY_SIZE + dos DO
    I dos.set @ IF
      I (update)
    THEN
  /DOS +LOOP ;

: (check-bytes) ( dos-addr -- flag ) dos.bytes @ DOS_BYTES_PER_INTERVAL > ;
: (check-lines) ( dos-addr -- flag ) dos.lines @ DOS_LINES_PER_INTERVAL > ;
: (check-connections) ( dos-addr -- flag ) dos.connections @ DOS_MAX_CONNECTIONS > ;
: dos-handled! ( flag connection-index-n -- )
  (lttranslate) @ dos.handled ! ;
: dos-handled? ( connection-index-n -- flag )
  (lttranslate) @ dos.handled @ ;
: dos? ( connection-index-n -- flag )
  (lttranslate) @
  dup  (check-bytes) over (check-lines)
  rot  (check-connections) or or ;

: (.dos-info) ( dos-addr -- )
  dup ." CircuitID: " dos.circuit-id @ . cr
  dup ." Connections: " dos.connections @ . cr
  dup ." Total bytes: " dos.total-bytes @ . cr
  dup ." Total lines: " dos.total-lines @ . cr
  dup ." Bytes: " dos.bytes @ . cr
  dup ." Lines: " dos.lines @ . cr
  drop ;
: .dos-info ( connection-index-u -- )
  (lttranslate) @ (.dos-info) ;
: .dos ( -- )
  dos DOS_ARRAY_SIZE + dos DO
    I dos.set @ IF
      cr I (.dos-info)
    THEN
  /DOS +LOOP ;