fix awg<->mm2 conversions

Add an inverted dictionary and a lookup function from awg -> mm2. Also
do some minor refactoring. Both sides of the conversion table were
converted to strings, since '0000' and '2/0' are perfectly valid AWG
values.

src/wireviz/wireviz.py

@@ -13,7 +13,7 @@ if __name__== '__main__':
     sys.path.insert(0, os.path.join(os.path.dirname(__file__), '..'))
 
 from wireviz import wv_colors
-from wireviz.wv_helper import nested, int2tuple, awg_equiv, flatten2d, tuplelist2tsv
+from wireviz.wv_helper import nested, int2tuple, mm2_equiv, awg_equiv, flatten2d, tuplelist2tsv
 
 class Harness:
 
@@ -117,8 +117,16 @@ class Harness:
 
         for k, c in self.cables.items():
             # a = attributes
+            if c.show_equiv:
+                if c.gauge_unit == 'mm\u00B2':
+                    gauge_equiv = ' ({} AWG)'.format(awg_equiv(c.gauge))
+                else:
+                    gauge_equiv = ' ({} mm\u00B2)'.format(mm2_equiv(c.gauge))
+            else:
+                gauge_equiv = ''
+
             a = ['{}x'.format(len(c.colors)) if c.show_wirecount else '',
-                 '{} {}{}'.format(c.gauge, c.gauge_unit, ' ({} AWG)'.format(awg_equiv(c.gauge)) if c.gauge_unit == 'mm\u00B2' and c.show_equiv else '') if c.gauge else '', # TODO: show equiv
+                 '{} {}{}'.format(c.gauge, c.gauge_unit, gauge_equiv) if c.gauge else '',
                  '+ S' if c.shield else '',
                  '{} m'.format(c.length) if c.length > 0 else '']
             a = list(filter(None, a))

src/wireviz/wv_helper.py

@@ -1,27 +1,28 @@
-from typing import Any, List
+from typing import List
+
+awg_equiv_table = {
+        '0.09': '28',
+        '0.14': '26',
+        '0.25': '24',
+        '0.34': '22',
+        '0.5' : '21',
+        '0.75': '20',
+        '1'   : '18',
+        '1.5' : '16',
+        '2.5' : '14',
+        '4'   : '12',
+        '6'   : '10',
+        '10'  : '8',
+        '16'  : '6',
+        '25'  : '4',
+        }
+mm2_equiv_table = {v:k for k,v in awg_equiv_table.items()}
 
 def awg_equiv(mm2):
-    awg_equiv_table = {
+    return awg_equiv_table.get(str(mm2), 'Unknown')
-                        '0.09': 28,
+
-                        '0.14': 26,
+def mm2_equiv(awg):
-                        '0.25': 24,
+    return mm2_equiv_table.get(str(awg), 'Unknown')
-                        '0.34': 22,
-                        '0.5': 21,
-                        '0.75': 20,
-                        '1': 18,
-                        '1.5': 16,
-                        '2.5': 14,
-                        '4': 12,
-                        '6': 10,
-                        '10': 8,
-                        '16': 6,
-                        '25': 4,
-                        }
-    k = str(mm2)
-    if k in awg_equiv_table:
-        return awg_equiv_table[k]
-    else:
-        return 'unknown'
 
 def nested(input):
     l = []