Cleanup rebalance sendinvoiceless (#33)

* doc: cleanup and key-value for optional parameters

* rebalance: cleanup and refinements

* sendinvoiceless: cleanup and refinements

* summary: reflects upcoming changes of pylightning to_approx_str

* rebalance: check peer connection on local channels

summary/summary.py

@@ -48,29 +48,43 @@ def to_fiatstr(msat: Millisatoshi):
     return "{}{:.2f}".format(plugin.currency_prefix,
                               int(msat) / 10**11 * plugin.fiat_per_btc)
 
-# this is included here for backwards compatibility to old pylightning version
-def msat_to_short_str(msat, digits: int = 3):
-    """
-    Returns the shortmost string using common units representation.
+
+# This is part of pylightning, but its just merged,
+# so old releases wont have it yet.
+def msat_to_approx_str(msat, digits: int = 3):
+    """Returns the shortmost string using common units representation.
+
     Rounds to significant `digits`. Default: 3
     """
-    # first round everything down 3 effective digits
     round_to_n = lambda x, n: round(x, -int(floor(log10(x))) + (n - 1))
-    amount_eff = round_to_n(msat, digits)
+    result = None
 
-    # try different units and take shortest resulting normalized string
-    amounts = [
-        "%gbtc"  % (amount_eff / 1000 / 10**8),
-        "%gmbtc" % (amount_eff / 1000 / 10**5),
-        "%gµbtc" % (amount_eff / 1000 / 10**2),
-        "%gsat"  % (amount_eff / 1000),
-        "%gmsat"  % (amount_eff),
-    ]
-    return min(amounts, key=len)
+    # we try to increase digits to check if we did loose out on precision
+    # without gaining a shorter string, since this is a rarely used UI
+    # function, performance is not an issue. Adds at least one iteration.
+    while True:
+        # first round everything down to effective digits
+        amount_rounded = round_to_n(msat.millisatoshis, digits)
+        # try different units and take shortest resulting normalized string
+        amounts_str = [
+            "%gbtc" % (amount_rounded / 1000 / 10**8),
+            "%gsat" % (amount_rounded / 1000),
+            "%gmsat" % (amount_rounded),
+        ]
+        test_result = min(amounts_str, key=len)
+
+        # check result and do another run if necessary
+        if test_result == result:
+            return result
+        elif not result or len(test_result) <= len(result):
+            digits = digits + 1
+            result = test_result
+        else:
+            return result
 
 # appends an output table header that explains fields and capacity
 def append_header(table, max_msat):
-    short_str = msat_to_short_str(max_msat)
+    short_str = msat_to_approx_str(Millisatoshi(max_msat))
     table.append("%c%-13sOUT/OURS %c IN/THEIRS%12s%c SCID           FLAG ALIAS"
             % (draw.left, short_str, draw.mid, short_str, draw.right))