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)