Solve 2016:21 p1-2 "Scrambled Letters and Hash"

A good day to utilize lots of unit testing!

For pt 2, the code initially tried to reverse
the scramble algorithm. The final code however
got the unscrambled version by the traditional
method most password crackers would resolve to:
basic brute forcing with permutations as a list
of candidates.

2016-python2/output/day_21.py

@@ -0,0 +1,64 @@
+import re
+from itertools import permutations
+
+from output import ints
+
+
+def solve(data):
+    data = [line.strip() for line in data.splitlines()]
+    p1 = scramble(data, "abcdefgh")
+    p2 = unscramble(data, "fbgdceah")
+    return p1, p2
+
+
+def scramble(data, subject):
+    r_swap = r"(?:letter|position) (.)"
+    for line in data:
+        if line.startswith("rotate right"):
+            x = ints(line)[0]
+            subject = subject[-x:] + subject[:-x]
+        if line.startswith("rotate left"):
+            x = ints(line)[0]
+            subject = subject[x:] + subject[:x]
+        if line.startswith("rotate based"):
+            x = re.findall(r"letter (.)", line)[0]
+            i = subject.index(x)
+            j = i + 1 % len(subject)
+            subject = subject[-j:] + subject[:-j]
+            if i >= 4:
+                subject = subject[-1:] + subject[:-1]
+        if line.startswith("swap letter"):
+            x, y = re.findall(r_swap, line)
+            subject = subject.replace(y, "#")
+            subject = subject.replace(x, y)
+            subject = subject.replace("#", x)
+        if line.startswith("swap position"):
+            x, y = ints(line)
+            v1, v2 = subject[x], subject[y]
+            subject = subject[:x] + v2 + subject[x + 1 :]
+            subject = subject[:y] + v1 + subject[y + 1 :]
+        if line.startswith("move"):
+            x, y = ints(line)
+            v = subject[x]
+            subject = subject[:x] + subject[x + 1 :]
+            subject = subject[:y] + v + subject[y:]
+        if line.startswith("reverse"):
+            x, y = ints(line)
+            subject = subject[:x] + subject[x : y + 1][::-1] + subject[y + 1 :]
+    return subject
+
+
+def unscramble(data, T):
+    for candidate in ["".join(c) for c in permutations(T)]:
+        if scramble(data, candidate) == T:
+            return candidate
+
+
+if __name__ == "__main__":
+    with open("./input/21.txt", "r") as f:
+        inp = f.read().strip()
+
+    p1, p2 = solve(inp)
+
+    print(p1)
+    print(p2)