utxo selection

WALLET.scratch.md

@@ -74,6 +74,29 @@ Uses `btc-wallet-hook`, with max-gap=3
 :: dbug should show re-filled scans: [xpub %1]
 ```
 
+### utxo selection
+```
+=btc -build-file %/lib/btc/hoon
+=bwsl -build-file %/lib/btc-wallet-store/hoon
+=u (utxo:btc [pos=0 (hash256:btc [wid=32 dat=0xc493.f6f1.4668.5f76.b44f.0c77.ca88.120c.b8bc.89f5.34fe.69b6.8288.27b9.74e6.8849]) height=3 value=0])
+=val0 200.000
+=val1 500.000
+=val2 30
+=val3 235.000
+
+=eny1 0v3uc.iuebi.5qilc.l8d87.c1k6n.7iksq.nkobs.8s5he.raq40.9ff0b.5tj3u.kjtg7.aq59e.hatv7.oioam.mlsr4.pqqcd.cnbjn.pnpi2.1m5rt.k4scg
+=eny2 0v1gt.mc4ca.lfs0m.q1dal.lqobu.mmlbd.2umnp.lj9dr.4pf4s.pvclr.dps96.4a6i8.rt6n9.krp0r.11kqu.ckqe4.1tmat.gr754.463aj.a4b41.jj7qg
+
+=inputs ~[[u(value val0) %0 0] [u(value val1) %0 2] [u(value val2) %0 1] [u(value val3) %1 2]]
+(~(single-random-draw sut:bwsl [*walt:bwsl eny1 400.100 100 2]) inputs)
+(~(single-random-draw sut:bwsl [*walt:bwsl eny2 400.100 100 2]) inputs)(~(single-random-draw sut:bwsl [*walt:bwsl eny2 400.100 100 2]) inputs)
+
+```
+Above tests w 2 outputs, total fees with 2 inputs of 27.500. Gives:
+1. 500.000 input
+2. Inputs 0 and 3
+
+
 ## scrys
 ```
 .^((list @t) %gx /=btc-wallet-store=/scanned/noun)

app/btc-wallet-store.hoon

@@ -258,29 +258,4 @@
       |=(=utxo:btc value.utxo)
     add
   (roll values add)
-::  Uses naive random selection. Should switch to branch-and-bound later
-::
-++  select-utxos
-  |=  [target=sats w=walt]
-  ^-  (unit (list input))
-  =/  is=(list input)
-    %-  zing
-    %+  turn  ~(val by wach.w)
-    |=  =addi
-    %+  turn  ~(tap in utxos.addi)
-      |=(=utxo:btc [utxo chyg.addi idx.addi])
-  (single-random-draw target is)
-::
-++  single-random-draw
-  |=  [target=sats is=(list input)]
-  ^-  (unit (list input))
-  =|  [selected=(list input) total=sats:btc]
-  =/  rng  ~(. og eny.bowl)
-  |-  ?~  is  ~
-  =^  n  rng  (rads:rng (lent is))
-  =/  i  (snag n ((list input) is))
-  =/  new-total  (add total value.utxo.i)
-  ?:  (gth new-total target)
-    `[i selected]
-  $(is t.is, total new-total, selected [i selected])
 --

lib/btc-wallet-store.hoon

@@ -89,4 +89,70 @@
       ?:(?=(%0 chyg) [idx q.nixt.w] [p.nixt.w idx])
     --
   --
+::  sut: door to select utxos
+::    targ: target output amount, not including fees
+::    feyb: fee in sats per byte
+::    outs: number of outputs
+::
+++  sut
+|_  [w=walt eny=@uvJ targ=sats feyb=sats outs=@]
+  ++  meta-weight  10
+  ++  output-weight  31
+  ++  base-weight
+    ^-  vbytes
+    %+  add  meta-weight
+    (mul outs output-weight)
+  ++  input-weight
+    ^-  vbytes
+    ?.  ?=(%bip84 bipt.w)
+      ~|("Only bech32 wallets supported" !!)
+    102
+  ::
+  ++  total-vbytes
+    |=  selected=(list input)
+    ^-  vbytes
+    %+  add  base-weight
+    (mul input-weight (lent selected))
+  ::  value of an input after fee
+  ::    0 if net is <= 0
+  ::
+  ++  net-value
+    |=  val=sats  ^-  sats
+    =/  cost  (mul input-weight feyb)
+    ?:  (lte val cost)  0
+    (sub val cost)
+ ::  Uses naive random selection. Should switch to branch-and-bound later
+  ::
+  ++  select-utxos
+    ^-  (unit (list input))
+    =/  is=(list input)
+      %-  zing
+      %+  turn  ~(val by wach.w)
+      |=  =addi
+      %+  turn  ~(tap in utxos.addi)
+        |=(=utxo:btc [utxo chyg.addi idx.addi])
+    (single-random-draw is)
+  ::  single-random-draw
+  ::    randomly choose utxos until target is hit
+  ::    only use an input if its net-value > 0
+  ::
+  ++  single-random-draw
+    |=  is=(list input)
+    ^-  (unit (list input))
+    =/  rng  ~(. og eny)
+    =/  target  (add targ (mul feyb base-weight))     ::  add base fees to target
+    =|  [select=(list input) total=sats:btc]
+    |-  ?~  is  ~
+    =^  n  rng  (rads:rng (lent is))
+    =/  i=input  (snag n ((list input) is))
+    =/  net-val  (net-value value.utxo.i)
+    =?  select  (gth net-val 0)  [i select]           ::  select if net-value > 0
+    =/  new-total  (add total net-val)
+    ?:  (gte new-total target)  `select
+    %=  $
+        is  (oust [n 1] ((list input) is))
+        total  new-total
+    ==
+  ::
+  --
 --

sur/btc.hoon

@@ -6,6 +6,7 @@
 +$  address  ?(legacy-address bech32-address)
 +$  bipt  $?(%bip44 %bip49 %bip84)
 +$  sats  @ud
++$  vbytes  @ud
 +$  hash256  [wid=%32 dat=@ux]
 +$  hash160  [wid=%20 dat=@ux]
 +$  hash  ?(hash256 hash160)