1 files changed, 154 insertions, 0 deletions
diff --git a/server/continuedev/libs/util/calculate_diff.py b/server/continuedev/libs/util/calculate_diff.py
new file mode 100644
index 00000000..99301ae7
--- /dev/null
+++ b/server/continuedev/libs/util/calculate_diff.py
@@ -0,0 +1,154 @@
+import difflib
+from typing import List
+
+from ...models.filesystem import FileEdit
+from ...models.main import Position, Range
+
+
+def calculate_diff(filepath: str, original: str, updated: str) -> List[FileEdit]:
+    s = difflib.SequenceMatcher(None, original, updated)
+    offset = 0  # The indices are offset by previous deletions/insertions
+    edits = []
+    for tag, i1, i2, j1, j2 in s.get_opcodes():
+        i1, i2, j1, j2 = i1 + offset, i2 + offset, j1 + offset, j2 + offset
+        replacement = updated[j1:j2]
+        if tag == "equal":
+            pass
+        elif tag == "delete":
+            edits.append(
+                FileEdit.from_deletion(filepath, Range.from_indices(original, i1, i2))
+            )
+            offset -= i2 - i1
+        elif tag == "insert":
+            edits.append(
+                FileEdit.from_insertion(
+                    filepath, Position.from_index(original, i1), replacement
+                )
+            )
+            offset += j2 - j1
+        elif tag == "replace":
+            edits.append(
+                FileEdit(
+                    filepath=filepath,
+                    range=Range.from_indices(original, i1, i2),
+                    replacement=replacement,
+                )
+            )
+            offset += (j2 - j1) - (i2 - i1)
+        else:
+            raise Exception("Unexpected difflib.SequenceMatcher tag: " + tag)
+
+    return edits
+
+
+def calculate_diff2(filepath: str, original: str, updated: str) -> List[FileEdit]:
+    # original_lines = original.splitlines()
+    # updated_lines = updated.splitlines()
+    # offset = 0
+    # while len(original_lines) and len(updated_lines) and original_lines[0] == updated_lines[0]:
+    #     original_lines = original_lines[1:]
+    #     updated_lines = updated_lines[1:]
+
+    # while len(original_lines) and len(updated_lines) and original_lines[-1] == updated_lines[-1]:
+    #     original_lines = original_lines[:-1]
+    #     updated_lines = updated_lines[:-1]
+
+    # original = "\n".join(original_lines)
+    # updated = "\n".join(updated_lines)
+
+    edits = []
+    max_iterations = 1000
+    i = 0
+    while not original == updated:
+        # TODO - For some reason it can't handle a single newline at the end of the file?
+        s = difflib.SequenceMatcher(None, original, updated)
+        opcodes = s.get_opcodes()
+        for edit_index in range(len(opcodes)):
+            tag, i1, i2, j1, j2 = s.get_opcodes()[edit_index]
+            replacement = updated[j1:j2]
+            if tag == "equal":
+                continue  # ;)
+            elif tag == "delete":
+                edits.append(
+                    FileEdit.from_deletion(
+                        filepath, Range.from_indices(original, i1, i2)
+                    )
+                )
+            elif tag == "insert":
+                edits.append(
+                    FileEdit.from_insertion(
+                        filepath, Position.from_index(original, i1), replacement
+                    )
+                )
+            elif tag == "replace":
+                edits.append(
+                    FileEdit(
+                        filepath=filepath,
+                        range=Range.from_indices(original, i1, i2),
+                        replacement=replacement,
+                    )
+                )
+            else:
+                raise Exception("Unexpected difflib.SequenceMatcher tag: " + tag)
+            break
+
+        original = apply_edit_to_str(original, edits[-1])
+
+        i += 1
+        if i > max_iterations:
+            raise Exception("Max iterations reached")
+
+    return edits
+
+
+def read_range_in_str(s: str, r: Range) -> str:
+    lines = s.splitlines()[r.start.line : r.end.line + 1]
+    if len(lines) == 0:
+        return ""
+
+    lines[0] = lines[0][r.start.character :]
+    lines[-1] = lines[-1][: r.end.character + 1]
+    return "\n".join(lines)
+
+
+def apply_edit_to_str(s: str, edit: FileEdit) -> str:
+    read_range_in_str(s, edit.range)
+
+    # Split lines and deal with some edge cases (could obviously be nicer)
+    lines = s.splitlines()
+    if s.startswith("\n"):
+        lines.insert(0, "")
+    if s.endswith("\n"):
+        lines.append("")
+
+    if len(lines) == 0:
+        lines = [""]
+
+    end = Position(line=edit.range.end.line, character=edit.range.end.character)
+    if edit.range.end.line == len(lines) and edit.range.end.character == 0:
+        end = Position(
+            line=edit.range.end.line - 1,
+            character=len(lines[min(len(lines) - 1, edit.range.end.line - 1)]),
+        )
+
+    before_lines = lines[: edit.range.start.line]
+    after_lines = lines[end.line + 1 :]
+    between_str = (
+        lines[min(len(lines) - 1, edit.range.start.line)][: edit.range.start.character]
+        + edit.replacement
+        + lines[min(len(lines) - 1, end.line)][end.character + 1 :]
+    )
+
+    Range(
+        start=edit.range.start,
+        end=Position(
+            line=edit.range.start.line + len(edit.replacement.splitlines()) - 1,
+            character=edit.range.start.character
+            + len(edit.replacement.splitlines()[-1])
+            if edit.replacement != ""
+            else 0,
+        ),
+    )
+
+    lines = before_lines + between_str.splitlines() + after_lines
+    return "\n".join(lines)