// bounded retransmission protocol [D'AJJL01]
// gxn/dxp 23/05/2001

dtmc

// number of chunks
const int N = 16;
// maximum number of retransmissions
const int MAX = 2;

// reliability of channels
const double pL;
const double pK;

// timeouts
const double TOMsg;
const double TOAck;

module sender

    s : [0..6];
    // 0 idle
    // 1 next_frame 
    // 2 wait_ack
    // 3 retransmit
    // 4 success
    // 5 error
    // 6 wait sync
    srep : [0..3];
    // 0 bottom
    // 1 not ok (nok)
    // 2 do not know (dk)
    // 3 ok (ok)
    nrtr : [0..MAX];
    i : [0..N];
    bs : bool;
    s_ab : bool;
    fs : bool;
    ls : bool;
    
    // idle
    [NewFile] (s=0) -> (s'=1) & (i'=1) & (srep'=0);
    // next_frame
    [aF] (s=1) -> (s'=2) & (fs'=(i=1)) & (ls'=(i=N)) & (bs'=s_ab) & (nrtr'=0);
    // wait_ack
    [aB] (s=2) -> (s'=4) & (s_ab'=!s_ab);
    [TO_Msg] (s=2) -> (s'=3);
    [TO_Ack] (s=2) -> (s'=3);
    // retransmit
    [aF] (s=3) & (nrtr<MAX) -> (s'=2) & (fs'=(i=1)) & (ls'=(i=N)) & (bs'=s_ab) & (nrtr'=nrtr+1);
    [] (s=3) & (nrtr=MAX) & (i<N) -> (s'=5) & (srep'=1);
    [] (s=3) & (nrtr=MAX) & (i=N) -> (s'=5) & (srep'=2);
    // success
    [] (s=4) & (i<N) -> (s'=1) & (i'=i+1);
    [] (s=4) & (i=N) -> (s'=0) & (srep'=3);
    // error
    [SyncWait] (s=5) -> (s'=6); 
    // wait sync
    [SyncWait] (s=6) -> (s'=0) & (s_ab'=false); 
    
endmodule

module receiver

    r : [0..5];
    // 0 new_file
    // 1 fst_safe
    // 2 frame_received
    // 3 frame_reported
    // 4 idle
    // 5 resync
    rrep : [0..4];
    // 0 bottom
    // 1 fst
    // 2 inc
    // 3 ok
    // 4 nok
    fr : bool;
    lr : bool;
    br : bool;
    r_ab : bool;
    recv : bool;
    
    
    // new_file
    [SyncWait] (r=0) -> (r'=0);
    [aG] (r=0) -> (r'=1) & (fr'=fs) & (lr'=ls) & (br'=bs) & (recv'=T);
    // fst_safe_frame
    [] (r=1) -> (r'=2) & (r_ab'=br);
    // frame_received
    [] (r=2) & (r_ab=br) & (fr=true) & (lr=false)  -> (r'=3) & (rrep'=1);
    [] (r=2) & (r_ab=br) & (fr=false) & (lr=false) -> (r'=3) & (rrep'=2);
    [] (r=2) & (r_ab=br) & (fr=false) & (lr=true)  -> (r'=3) & (rrep'=3);
    [aA] (r=2) & !(r_ab=br) -> (r'=4);  
    // frame_reported
    [aA] (r=3) -> (r'=4) & (r_ab'=!r_ab);
    // idle
    [aG] (r=4) -> (r'=2) & (fr'=fs) & (lr'=ls) & (br'=bs) & (recv'=T);
    [SyncWait] (r=4) & (ls=true) -> (r'=5);
    [SyncWait] (r=4) & (ls=false) -> (r'=5) & (rrep'=4);
    // resync
    [SyncWait] (r=5) -> (r'=0) & (rrep'=0);
    
endmodule

// prevents more than one file being sent
module tester 

    T : bool;
    
    [NewFile] (T=false) -> (T'=true);
    
endmodule

module  channelK

    k : [0..2];
    
    // idle
    [aF] (k=0) -> pK : (k'=1) + 1-pK : (k'=2);
    // sending
    [aG] (k=1) -> (k'=0);
    // lost
    [TO_Msg] (k=2) -> (k'=0);
    
endmodule

module  channelL

    l : [0..2];
    
    // idle
    [aA] (l=0) -> pL : (l'=1) + 1-pL : (l'=2);
    // sending
    [aB] (l=1) -> (l'=0);
    // lost
    [TO_Ack] (l=2) -> (l'=0);
    
endmodule

rewards
	[TO_Msg] true : TOMsg;
	[TO_Ack] true : TOAck;
endrewards

label "error" = s=5;
label "success" = (s=0) & (srep=3);
label "target" = (s=5) | (s=0 & srep=3);