moved the process_diff_method from gitless to gitpylib

gitpylib/file.py

@@ -5,7 +5,9 @@
 """Module for dealing with Git files."""
 
 
+import collections
 import os.path
+import re
 
 import common
 
@@ -14,6 +16,12 @@
 FILE_NOT_FOUND = 2
 FILE_NOT_FOUND_AT_CP = 3
 
+# Possible diff output lines.
+DIFF_INFO = 4  # line carrying diff info for new hunk.
+DIFF_SAME = 5  # line that git diff includes for context.
+DIFF_ADDED = 6
+DIFF_MINUS = 7
+
 
 def stage(fp):
   """Stages the given file.
@@ -118,7 +126,7 @@ def diff(fp):
   fp = common.real_case(fp)
 
   out, unused_err = common.safe_git_call('diff -- "%s"' % fp)
-  return out
+  return _process_diff_output(_strip_diff_header(out.splitlines()))
 
 
 def staged_diff(fp):
@@ -133,4 +141,75 @@ def staged_diff(fp):
   fp = common.real_case(fp)
 
   out, unused_err = common.safe_git_call('diff --cached -- "%s"' % fp)
-  return out
+  return _process_diff_output(_strip_diff_header(out.splitlines()))
+
+
+# Private functions.
+
+
+def _strip_diff_header(diff_out):
+  """Removes the diff header lines."""
+  first_non_header_line = 0
+  for line in diff_out:
+    if line.startswith('@@'):
+      break
+    first_non_header_line += 1
+  return diff_out[first_non_header_line:]
+
+
+def _process_diff_output(diff_out):
+  """Process the git diff output.
+
+  Args:
+    diff_out: a list of lines output by the git diff command.
+
+  Returns:
+    a 2-tuple of:
+      - a list of namedtuples with fields 'line', 'status', 'old_line_number'
+      and 'new_line_number' where 'status' is one of DIFF_INFO, DIFF_SAME,
+      DIFF_ADDED or DIFF_MINUS and 'old_line_number', 'new_line_number'
+      correspond to the line's old line number and new line number respectively.
+      (Note that, for example, if the line is DIFF_ADDED, then 'old_line_number'
+      is None since that line is not present in the old file).
+      - max_line_digits: return the maximum amount of line digits found while
+      parsing the git diff output, this is useful for padding.
+  """
+  MIN_LINE_PADDING = 8
+  LineData = collections.namedtuple(
+      'LineData',
+      ['line', 'status', 'old_line_number', 'new_line_number'])
+
+  resulting = []  # accumulates line information for formatting.
+  max_line_digits = 0
+  old_line_number = 1
+  new_line_number = 1
+
+  for line in diff_out:
+    # @@ -(start of old),(length of old) +(start of new),(length of new) @@
+    new_hunk_regex = "^@@ -([0-9]+),([0-9]+) \+([0-9]+),([0-9]+) @@"
+    new_hunk_info = re.search(new_hunk_regex, line)
+    if new_hunk_info:
+      old_line_number = int(new_hunk_info.group(1))
+      old_diff_length = int(new_hunk_info.group(2))
+      new_line_number = int(new_hunk_info.group(3))
+      new_diff_length = int(new_hunk_info.group(4))
+      resulting.append(
+          LineData(line, DIFF_INFO, old_line_number, new_line_number))
+      max_line_digits = max([old_line_number + old_diff_length,
+                             new_line_number + new_diff_length,
+                             max_line_digits])  # start + length of each diff.
+    elif line.startswith(' '):
+      resulting.append(
+          LineData(line, DIFF_SAME,  old_line_number, new_line_number))
+      old_line_number += 1
+      new_line_number += 1
+    elif line.startswith('-'):
+      resulting.append(LineData(line, DIFF_MINUS, old_line_number, None))
+      old_line_number += 1
+    elif line.startswith('+'):
+      resulting.append(LineData(line, DIFF_ADDED, None, new_line_number))
+      new_line_number += 1
+
+  max_line_digits = len(str(max_line_digits))  # digits = len(string of number).
+  max_line_digits = max(MIN_LINE_PADDING, max_line_digits + 1)
+  return resulting, max_line_digits