import json
import sys

def usage():
    print("python mod_layer.py <source layout JSON file> <destination layout JSON file> <layer index>")
    sys.exit(1)

if len(sys.argv) != 4:
    usage()

try:
     layer = int(sys.argv[3])
except ValueError:
    usage()

if layer < 0 or layer > 9:
    print("Layer must be between 0 and 9")
    usage()

layout = json.load(open(sys.argv[1]))
for k in layout['keymaps'][layer]:
    if 'categories' in k:
        continue
    # Offset from https://github.com/keyboardio/Chrysalis/blob/master/src/api/keymap/db/modifiers.js#L19
    # This is the offset for shift. Switch to another offset from Chrysalis to get a different mod
    k['code'] += 1 << 11
json.dump(layout, open(sys.argv[2], 'w'), sort_keys=True, indent=4)