Add utils functions for calculating how similar two names are.

Copied from cerebrum, uses restricted damarau levenshtein.

Issue: GREG-68

gregui/utils.py

+
+def restricted_damarau_levenshtein(first: str, second:str) -> int:
+    """
+    Calculate the edit distance between two string using restricted damarau
+    levenshtein. Allowing deletion, insertion, substitution and transposition
+    of characters.
+    """
+    first = ' ' + first
+    second = ' ' + second
+    dist_matrix = [[0 for i in range(len(first))] for b in range(len(second))]
+
+    for i in range(len(second)):
+        dist_matrix[i][0] = i
+
+    for j in range(len(first)):
+        dist_matrix[0][j] = j
+
+    for i in range(1, len(dist_matrix)):
+        for j in range(1, len(dist_matrix[0])):
+            possible_choices = [dist_matrix[i-1][j] + 1,           #del
+                                dist_matrix[i][j-1] + 1]           #ins
+            if first[j] == second[i]:
+                possible_choices.append(dist_matrix[i-1][j-1])     #equal
+            elif first[j] == second[i-1] and first[j-1] == second[i]:
+                possible_choices.append(dist_matrix[i-2][j-2] + 1) #trans
+            else:
+                possible_choices.append(dist_matrix[i-1][j-1] + 1) #sub
+            dist_matrix[i][j] = min(possible_choices)
+
+    return dist_matrix[-1][-1]
+
+
+def name_diff(full_name1:str, full_name2:str, threshold:int=2) -> int:
+    """
+    Calculate the difference between two names, allowing one name to be
+    longer than the other by only checking whether all names in the shortest
+    seem to be included in the longest.
+    e.g. name_diff('foo bar', 'foo test bar') = 0
+
+    If the total difference is larger than a given threshold after any part of
+    the name, the function will return early. Useful when only close matches
+    are interesting.
+    """
+    total_difference = 0
+    names1 = full_name1.split()
+    names2 = full_name2.split()
+    if len(names1) > len(names2):
+        names1, names2 = names2, names1
+
+    for n1 in names1:
+        best_match = (0, 5)
+        for i, n2 in enumerate(names2, 1):
+            diff = restricted_damarau_levenshtein(n1, n2)
+            if diff < best_match[1]:
+                best_match = (i, diff)
+
+        total_difference += best_match[1]
+        names2 = names2[best_match[0]:]
+        if total_difference > threshold:
+            break
+    return total_difference
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