"""GitHub Label Utilities."""

import json

from functools import lru_cache
from typing import List, Any, Tuple, TYPE_CHECKING, Union
from urllib.request import urlopen, Request

from github_utils import (
    GitHubComment,
    gh_fetch_json,
)

# TODO: this is a temp workaround to avoid circular dependencies,
#       and should be removed once GitHubPR is refactored out of trymerge script.
if TYPE_CHECKING:
    from trymerge import GitHubPR

BOT_AUTHORS = ["github-actions", "pytorchmergebot", "pytorch-bot"]

LABEL_ERR_MSG_TITLE = "This PR needs a label"
LABEL_ERR_MSG = f"""# {LABEL_ERR_MSG_TITLE}
If your changes are user facing and intended to be a part of release notes, please use a label starting with `release notes:`.

If not, please add the `topic: not user facing` label.

For more information, see
https://github.com/pytorch/pytorch/wiki/PyTorch-AutoLabel-Bot#why-categorize-for-release-notes-and-how-does-it-work.
"""

# Modified from https://github.com/pytorch/pytorch/blob/b00206d4737d1f1e7a442c9f8a1cadccd272a386/torch/hub.py#L129
def _read_url(url: Request) -> Tuple[Any, Any]:
    with urlopen(url) as r:
        return r.headers, r.read().decode(r.headers.get_content_charset('utf-8'))


def request_for_labels(url: str) -> Tuple[Any, Any]:
    headers = {'Accept': 'application/vnd.github.v3+json'}
    return _read_url(Request(url, headers=headers))


def update_labels(labels: List[str], info: str) -> None:
    labels_json = json.loads(info)
    labels.extend([x["name"] for x in labels_json])


def get_last_page_num_from_header(header: Any) -> int:
    # Link info looks like: <https://api.github.com/repositories/65600975/labels?per_page=100&page=2>;
    # rel="next", <https://api.github.com/repositories/65600975/labels?per_page=100&page=3>; rel="last"
    link_info = header['link']
    prefix = "&page="
    suffix = ">;"
    return int(link_info[link_info.rindex(prefix) + len(prefix):link_info.rindex(suffix)])


@lru_cache()
def gh_get_labels(org: str, repo: str) -> List[str]:
    prefix = f"https://api.github.com/repos/{org}/{repo}/labels?per_page=100"
    header, info = request_for_labels(prefix + "&page=1")
    labels: List[str] = []
    update_labels(labels, info)

    last_page = get_last_page_num_from_header(header)
    assert last_page > 0, "Error reading header info to determine total number of pages of labels"
    for page_number in range(2, last_page + 1):  # skip page 1
        _, info = request_for_labels(prefix + f"&page={page_number}")
        update_labels(labels, info)

    return labels


def gh_add_labels(org: str, repo: str, pr_num: int, labels: Union[str, List[str]]) -> None:
    gh_fetch_json(
        f'https://api.github.com/repos/{org}/{repo}/issues/{pr_num}/labels',
        data={"labels": labels},
    )


def get_release_notes_labels(org: str, repo: str) -> List[str]:
    return [label for label in gh_get_labels(org, repo) if label.lstrip().startswith("release notes:")]


def has_required_labels(pr: "GitHubPR") -> bool:
    pr_labels = pr.get_labels()
    # Check if PR is not user facing
    is_not_user_facing_pr = any(label.strip() == "topic: not user facing" for label in pr_labels)
    return (
        is_not_user_facing_pr or
        any(label.strip() in get_release_notes_labels(pr.org, pr.project) for label in pr_labels)
    )


def is_label_err_comment(comment: GitHubComment) -> bool:
    return comment.body_text.lstrip(" #").startswith(LABEL_ERR_MSG_TITLE) and comment.author_login in BOT_AUTHORS