#!/usr/bin/env python3
#
# ======- github-automation - LLVM GitHub Automation Routines--*- python -*--==#
#
# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
# See https://llvm.org/LICENSE.txt for license information.
# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#
# ==-------------------------------------------------------------------------==#

import argparse
from git import Repo  # type: ignore
import html
import github
import os
import re
import requests
import sys
import time
from typing import List, Optional

beginner_comment = """
Hi!

This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:

1. In the comments of the issue, request for it to be assigned to you.
2. Fix the issue locally.
3. [Run the test suite](https://llvm.org/docs/TestingGuide.html#unit-and-regression-tests) locally. Remember that the subdirectories under `test/` create fine-grained testing targets, so you can e.g. use `make check-clang-ast` to only run Clang's AST tests.
4. Create a Git commit.
5. Run [`git clang-format HEAD~1`](https://clang.llvm.org/docs/ClangFormat.html#git-integration) to format your changes.
6. Open a [pull request](https://github.com/llvm/llvm-project/pulls) to the [upstream repository](https://github.com/llvm/llvm-project) on GitHub. Detailed instructions can be found [in GitHub's documentation](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/creating-a-pull-request).

If you have any further questions about this issue, don't hesitate to ask via a comment in the thread below.
"""


def _get_curent_team(team_name, teams) -> Optional[github.Team.Team]:
    for team in teams:
        if team_name == team.name.lower():
            return team
    return None


def escape_description(str):
    # If the description of an issue/pull request is empty, the Github API
    # library returns None instead of an empty string. Handle this here to
    # avoid failures from trying to manipulate None.
    if str is None:
        return ""
    # https://github.com/github/markup/issues/1168#issuecomment-494946168
    str = html.escape(str, False)
    # '@' followed by alphanum is a user name
    str = re.sub("@(?=\w)", "@<!-- -->", str)
    # '#' followed by digits is considered an issue number
    str = re.sub("#(?=\d)", "#<!-- -->", str)
    return str


class IssueSubscriber:
    @property
    def team_name(self) -> str:
        return self._team_name

    def __init__(self, token: str, repo: str, issue_number: int, label_name: str):
        self.repo = github.Github(token).get_repo(repo)
        self.org = github.Github(token).get_organization(self.repo.organization.login)
        self.issue = self.repo.get_issue(issue_number)
        self._team_name = "issue-subscribers-{}".format(label_name).lower()

    def run(self) -> bool:
        team = _get_curent_team(self.team_name, self.org.get_teams())
        if not team:
            print(f"couldn't find team named {self.team_name}")
            return False

        comment = ""
        if team.slug == "issue-subscribers-good-first-issue":
            comment = "{}\n".format(beginner_comment)
            self.issue.create_comment(comment)

        body = escape_description(self.issue.body)
        comment = f"""
@llvm/{team.slug}

Author: {self.issue.user.name} ({self.issue.user.login})

<details>
{body}
</details>
"""

        self.issue.create_comment(comment)
        return True


def human_readable_size(size, decimal_places=2):
    for unit in ["B", "KiB", "MiB", "GiB", "TiB", "PiB"]:
        if size < 1024.0 or unit == "PiB":
            break
        size /= 1024.0
    return f"{size:.{decimal_places}f} {unit}"


class PRSubscriber:
    @property
    def team_name(self) -> str:
        return self._team_name

    def __init__(self, token: str, repo: str, pr_number: int, label_name: str):
        self.repo = github.Github(token).get_repo(repo)
        self.org = github.Github(token).get_organization(self.repo.organization.login)
        self.pr = self.repo.get_issue(pr_number).as_pull_request()
        self._team_name = "pr-subscribers-{}".format(
            label_name.replace("+", "x")
        ).lower()
        self.COMMENT_TAG = "<!--LLVM PR SUMMARY COMMENT-->\n"

    def get_summary_comment(self) -> github.IssueComment.IssueComment:
        for comment in self.pr.as_issue().get_comments():
            if self.COMMENT_TAG in comment.body:
                return comment
        return None

    def run(self) -> bool:
        patch = None
        team = _get_curent_team(self.team_name, self.org.get_teams())
        if not team:
            print(f"couldn't find team named {self.team_name}")
            return False

        # GitHub limits comments to 65,536 characters, let's limit the diff
        # and the file list to 20kB each.
        STAT_LIMIT = 20 * 1024
        DIFF_LIMIT = 20 * 1024

        # Get statistics for each file
        diff_stats = f"{self.pr.changed_files} Files Affected:\n\n"
        for file in self.pr.get_files():
            diff_stats += f"- ({file.status}) {file.filename} ("
            if file.additions:
                diff_stats += f"+{file.additions}"
            if file.deletions:
                diff_stats += f"-{file.deletions}"
            diff_stats += ") "
            if file.status == "renamed":
                print(f"(from {file.previous_filename})")
            diff_stats += "\n"
            if len(diff_stats) > STAT_LIMIT:
                break

        # Get the diff
        try:
            patch = requests.get(self.pr.diff_url).text
        except:
            patch = ""

        patch_link = f"Full diff: {self.pr.diff_url}\n"
        if len(patch) > DIFF_LIMIT:
            patch_link = f"\nPatch is {human_readable_size(len(patch))}, truncated to {human_readable_size(DIFF_LIMIT)} below, full version: {self.pr.diff_url}\n"
            patch = patch[0:DIFF_LIMIT] + "...\n[truncated]\n"
        team_mention = "@llvm/{}".format(team.slug)

        body = escape_description(self.pr.body)
        # Note: the comment is in markdown and the code below
        # is sensible to line break
        comment = f"""
{self.COMMENT_TAG}
{team_mention}

Author: {self.pr.user.name} ({self.pr.user.login})

<details>
<summary>Changes</summary>

{body}

---
{patch_link}

{diff_stats}

``````````diff
{patch}
``````````

</details>
"""

        summary_comment = self.get_summary_comment()
        if not summary_comment:
            self.pr.as_issue().create_comment(comment)
        elif team_mention + "\n" in summary_comment.body:
            print("Team {} already mentioned.".format(team.slug))
        else:
            summary_comment.edit(
                summary_comment.body.replace(
                    self.COMMENT_TAG, self.COMMENT_TAG + team_mention + "\n"
                )
            )
        return True

    def _get_curent_team(self) -> Optional[github.Team.Team]:
        for team in self.org.get_teams():
            if self.team_name == team.name.lower():
                return team
        return None


class PRGreeter:
    def __init__(self, token: str, repo: str, pr_number: int):
        repo = github.Github(token).get_repo(repo)
        self.pr = repo.get_issue(pr_number).as_pull_request()

    def run(self) -> bool:
        # We assume that this is only called for a PR that has just been opened
        # by a user new to LLVM and/or GitHub itself.

        # This text is using Markdown formatting.
        comment = f"""\
Thank you for submitting a Pull Request (PR) to the LLVM Project!

This PR will be automatically labeled and the relevant teams will be
notified.

If you wish to, you can add reviewers by using the "Reviewers" section on this page.

If this is not working for you, it is probably because you do not have write
permissions for the repository. In which case you can instead tag reviewers by
name in a comment by using `@` followed by their GitHub username.

If you have received no comments on your PR for a week, you can request a review
by "ping"ing the PR by adding a comment “Ping”. The common courtesy "ping" rate
is once a week. Please remember that you are asking for valuable time from other developers.

If you have further questions, they may be answered by the [LLVM GitHub User Guide](https://llvm.org/docs/GitHub.html).

You can also ask questions in a comment on this PR, on the [LLVM Discord](https://discord.com/invite/xS7Z362) or on the [forums](https://discourse.llvm.org/)."""
        self.pr.as_issue().create_comment(comment)
        return True


def setup_llvmbot_git(git_dir="."):
    """
    Configure the git repo in `git_dir` with the llvmbot account so
    commits are attributed to llvmbot.
    """
    repo = Repo(git_dir)
    with repo.config_writer() as config:
        config.set_value("user", "name", "llvmbot")
        config.set_value("user", "email", "llvmbot@llvm.org")


def phab_api_call(phab_token: str, url: str, args: dict) -> dict:
    """
    Make an API call to the Phabricator web service and return a dictionary
    containing the json response.
    """
    data = {"api.token": phab_token}
    data.update(args)
    response = requests.post(url, data=data)
    return response.json()


def phab_login_to_github_login(
    phab_token: str, repo: github.Repository.Repository, phab_login: str
) -> Optional[str]:
    """
    Tries to translate a Phabricator login to a github login by
    finding a commit made in Phabricator's Differential.
    The commit's SHA1 is then looked up in the github repo and
    the committer's login associated with that commit is returned.

    :param str phab_token: The Conduit API token to use for communication with Pabricator
    :param github.Repository.Repository repo: The github repo to use when looking for the SHA1 found in Differential
    :param str phab_login: The Phabricator login to be translated.
    """

    args = {
        "constraints[authors][0]": phab_login,
        # PHID for "LLVM Github Monorepo" repository
        "constraints[repositories][0]": "PHID-REPO-f4scjekhnkmh7qilxlcy",
        "limit": 1,
    }
    # API documentation: https://reviews.llvm.org/conduit/method/diffusion.commit.search/
    r = phab_api_call(
        phab_token, "https://reviews.llvm.org/api/diffusion.commit.search", args
    )
    data = r["result"]["data"]
    if len(data) == 0:
        # Can't find any commits associated with this user
        return None

    commit_sha = data[0]["fields"]["identifier"]
    committer = repo.get_commit(commit_sha).committer
    if not committer:
        # This committer had an email address GitHub could not recognize, so
        # it can't link the user to a GitHub account.
        print(f"Warning: Can't find github account for {phab_login}")
        return None
    return committer.login


def phab_get_commit_approvers(phab_token: str, commit: github.Commit.Commit) -> list:
    args = {"corpus": commit.commit.message}
    # API documentation: https://reviews.llvm.org/conduit/method/differential.parsecommitmessage/
    r = phab_api_call(
        phab_token, "https://reviews.llvm.org/api/differential.parsecommitmessage", args
    )
    review_id = r["result"]["revisionIDFieldInfo"]["value"]
    if not review_id:
        # No Phabricator revision for this commit
        return []

    args = {"constraints[ids][0]": review_id, "attachments[reviewers]": True}
    # API documentation: https://reviews.llvm.org/conduit/method/differential.revision.search/
    r = phab_api_call(
        phab_token, "https://reviews.llvm.org/api/differential.revision.search", args
    )
    reviewers = r["result"]["data"][0]["attachments"]["reviewers"]["reviewers"]
    accepted = []
    for reviewer in reviewers:
        if reviewer["status"] != "accepted":
            continue
        phid = reviewer["reviewerPHID"]
        args = {"constraints[phids][0]": phid}
        # API documentation: https://reviews.llvm.org/conduit/method/user.search/
        r = phab_api_call(phab_token, "https://reviews.llvm.org/api/user.search", args)
        accepted.append(r["result"]["data"][0]["fields"]["username"])
    return accepted


def extract_commit_hash(arg: str):
    """
    Extract the commit hash from the argument passed to /action github
    comment actions. We currently only support passing the commit hash
    directly or use the github URL, such as
    https://github.com/llvm/llvm-project/commit/2832d7941f4207f1fcf813b27cf08cecc3086959
    """
    github_prefix = "https://github.com/llvm/llvm-project/commit/"
    if arg.startswith(github_prefix):
        return arg[len(github_prefix) :]
    return arg


class ReleaseWorkflow:
    CHERRY_PICK_FAILED_LABEL = "release:cherry-pick-failed"

    """
    This class implements the sub-commands for the release-workflow command.
    The current sub-commands are:
        * create-branch
        * create-pull-request

    The execute_command method will automatically choose the correct sub-command
    based on the text in stdin.
    """

    def __init__(
        self,
        token: str,
        repo: str,
        issue_number: int,
        branch_repo_name: str,
        branch_repo_token: str,
        llvm_project_dir: str,
        phab_token: str,
    ) -> None:
        self._token = token
        self._repo_name = repo
        self._issue_number = issue_number
        self._branch_repo_name = branch_repo_name
        if branch_repo_token:
            self._branch_repo_token = branch_repo_token
        else:
            self._branch_repo_token = self.token
        self._llvm_project_dir = llvm_project_dir
        self._phab_token = phab_token

    @property
    def token(self) -> str:
        return self._token

    @property
    def repo_name(self) -> str:
        return self._repo_name

    @property
    def issue_number(self) -> int:
        return self._issue_number

    @property
    def branch_repo_name(self) -> str:
        return self._branch_repo_name

    @property
    def branch_repo_token(self) -> str:
        return self._branch_repo_token

    @property
    def llvm_project_dir(self) -> str:
        return self._llvm_project_dir

    @property
    def phab_token(self) -> str:
        return self._phab_token

    @property
    def repo(self) -> github.Repository.Repository:
        return github.Github(self.token).get_repo(self.repo_name)

    @property
    def issue(self) -> github.Issue.Issue:
        return self.repo.get_issue(self.issue_number)

    @property
    def push_url(self) -> str:
        return "https://{}@github.com/{}".format(
            self.branch_repo_token, self.branch_repo_name
        )

    @property
    def branch_name(self) -> str:
        return "issue{}".format(self.issue_number)

    @property
    def release_branch_for_issue(self) -> Optional[str]:
        issue = self.issue
        milestone = issue.milestone
        if milestone is None:
            return None
        m = re.search("branch: (.+)", milestone.description)
        if m:
            return m.group(1)
        return None

    def print_release_branch(self) -> None:
        print(self.release_branch_for_issue)

    def issue_notify_branch(self) -> None:
        self.issue.create_comment(
            "/branch {}/{}".format(self.branch_repo_name, self.branch_name)
        )

    def issue_notify_pull_request(self, pull: github.PullRequest.PullRequest) -> None:
        self.issue.create_comment(
            "/pull-request {}#{}".format(self.branch_repo_name, pull.number)
        )

    def make_ignore_comment(self, comment: str) -> str:
        """
        Returns the comment string with a prefix that will cause
        a Github workflow to skip parsing this comment.

        :param str comment: The comment to ignore
        """
        return "<!--IGNORE-->\n" + comment

    def issue_notify_no_milestone(self, comment: List[str]) -> None:
        message = "{}\n\nError: Command failed due to missing milestone.".format(
            "".join([">" + line for line in comment])
        )
        self.issue.create_comment(self.make_ignore_comment(message))

    @property
    def action_url(self) -> str:
        if os.getenv("CI"):
            return "https://github.com/{}/actions/runs/{}".format(
                os.getenv("GITHUB_REPOSITORY"), os.getenv("GITHUB_RUN_ID")
            )
        return ""

    def issue_notify_cherry_pick_failure(
        self, commit: str
    ) -> github.IssueComment.IssueComment:
        message = self.make_ignore_comment(
            "Failed to cherry-pick: {}\n\n".format(commit)
        )
        action_url = self.action_url
        if action_url:
            message += action_url + "\n\n"
        message += "Please manually backport the fix and push it to your github fork.  Once this is done, please add a comment like this:\n\n`/branch <user>/<repo>/<branch>`"
        issue = self.issue
        comment = issue.create_comment(message)
        issue.add_to_labels(self.CHERRY_PICK_FAILED_LABEL)
        return comment

    def issue_notify_pull_request_failure(
        self, branch: str
    ) -> github.IssueComment.IssueComment:
        message = "Failed to create pull request for {} ".format(branch)
        message += self.action_url
        return self.issue.create_comment(message)

    def issue_remove_cherry_pick_failed_label(self):
        if self.CHERRY_PICK_FAILED_LABEL in [l.name for l in self.issue.labels]:
            self.issue.remove_from_labels(self.CHERRY_PICK_FAILED_LABEL)

    def pr_request_review(self, pr: github.PullRequest.PullRequest):
        """
        This function will try to find the best reviewers for `commits` and
        then add a comment requesting review of the backport and assign the
        pull request to the selected reviewers.

        The reviewers selected are those users who approved the patch in
        Phabricator.
        """
        reviewers = []
        for commit in pr.get_commits():
            approvers = phab_get_commit_approvers(self.phab_token, commit)
            for a in approvers:
                login = phab_login_to_github_login(self.phab_token, self.repo, a)
                if not login:
                    continue
                reviewers.append(login)
        if len(reviewers):
            message = "{} What do you think about merging this PR to the release branch?".format(
                " ".join(["@" + r for r in reviewers])
            )
            pr.create_issue_comment(message)
            pr.add_to_assignees(*reviewers)

    def create_branch(self, commits: List[str]) -> bool:
        """
        This function attempts to backport `commits` into the branch associated
        with `self.issue_number`.

        If this is successful, then the branch is pushed to `self.branch_repo_name`, if not,
        a comment is added to the issue saying that the cherry-pick failed.

        :param list commits: List of commits to cherry-pick.

        """
        print("cherry-picking", commits)
        branch_name = self.branch_name
        local_repo = Repo(self.llvm_project_dir)
        local_repo.git.checkout(self.release_branch_for_issue)

        for c in commits:
            try:
                local_repo.git.cherry_pick("-x", c)
            except Exception as e:
                self.issue_notify_cherry_pick_failure(c)
                raise e

        push_url = self.push_url
        print("Pushing to {} {}".format(push_url, branch_name))
        local_repo.git.push(push_url, "HEAD:{}".format(branch_name), force=True)

        self.issue_notify_branch()
        self.issue_remove_cherry_pick_failed_label()
        return True

    def check_if_pull_request_exists(
        self, repo: github.Repository.Repository, head: str
    ) -> bool:
        pulls = repo.get_pulls(head=head)
        return pulls.totalCount != 0

    def create_pull_request(self, owner: str, repo_name: str, branch: str) -> bool:
        """
        reate a pull request in `self.branch_repo_name`.  The base branch of the
        pull request will be chosen based on the the milestone attached to
        the issue represented by `self.issue_number`  For example if the milestone
        is Release 13.0.1, then the base branch will be release/13.x. `branch`
        will be used as the compare branch.
        https://docs.github.com/en/get-started/quickstart/github-glossary#base-branch
        https://docs.github.com/en/get-started/quickstart/github-glossary#compare-branch
        """
        repo = github.Github(self.token).get_repo(self.branch_repo_name)
        issue_ref = "{}#{}".format(self.repo_name, self.issue_number)
        pull = None
        release_branch_for_issue = self.release_branch_for_issue
        if release_branch_for_issue is None:
            return False
        head_branch = branch
        if not repo.fork:
            # If the target repo is not a fork of llvm-project, we need to copy
            # the branch into the target repo.  GitHub only supports cross-repo pull
            # requests on forked repos.
            head_branch = f"{owner}-{branch}"
            local_repo = Repo(self.llvm_project_dir)
            push_done = False
            for _ in range(0, 5):
                try:
                    local_repo.git.fetch(
                        f"https://github.com/{owner}/{repo_name}", f"{branch}:{branch}"
                    )
                    local_repo.git.push(
                        self.push_url, f"{branch}:{head_branch}", force=True
                    )
                    push_done = True
                    break
                except Exception as e:
                    print(e)
                    time.sleep(30)
                    continue
            if not push_done:
                raise Exception("Failed to mirror branch into {}".format(self.push_url))
            owner = repo.owner.login

        head = f"{owner}:{head_branch}"
        if self.check_if_pull_request_exists(repo, head):
            print("PR already exists...")
            return True
        try:
            pull = repo.create_pull(
                title=f"PR for {issue_ref}",
                body="resolves {}".format(issue_ref),
                base=release_branch_for_issue,
                head=head,
                maintainer_can_modify=False,
            )

            try:
                if self.phab_token:
                    self.pr_request_review(pull)
            except Exception as e:
                print("error: Failed while searching for reviewers", e)

        except Exception as e:
            self.issue_notify_pull_request_failure(branch)
            raise e

        if pull is None:
            return False

        self.issue_notify_pull_request(pull)
        self.issue_remove_cherry_pick_failed_label()

        # TODO(tstellar): Do you really want to always return True?
        return True

    def execute_command(self) -> bool:
        """
        This function reads lines from STDIN and executes the first command
        that it finds.  The 2 supported commands are:
        /cherry-pick commit0 <commit1> <commit2> <...>
        /branch <owner>/<repo>/<branch>
        """
        for line in sys.stdin:
            line.rstrip()
            m = re.search(r"/([a-z-]+)\s(.+)", line)
            if not m:
                continue
            command = m.group(1)
            args = m.group(2)

            if command == "cherry-pick":
                arg_list = args.split()
                commits = list(map(lambda a: extract_commit_hash(a), arg_list))
                return self.create_branch(commits)

            if command == "branch":
                m = re.match("([^/]+)/([^/]+)/(.+)", args)
                if m:
                    owner = m.group(1)
                    repo = m.group(2)
                    branch = m.group(3)
                    return self.create_pull_request(owner, repo, branch)

        print("Do not understand input:")
        print(sys.stdin.readlines())
        return False


parser = argparse.ArgumentParser()
parser.add_argument(
    "--token", type=str, required=True, help="GitHub authentiation token"
)
parser.add_argument(
    "--repo",
    type=str,
    default=os.getenv("GITHUB_REPOSITORY", "llvm/llvm-project"),
    help="The GitHub repository that we are working with in the form of <owner>/<repo> (e.g. llvm/llvm-project)",
)
subparsers = parser.add_subparsers(dest="command")

issue_subscriber_parser = subparsers.add_parser("issue-subscriber")
issue_subscriber_parser.add_argument("--label-name", type=str, required=True)
issue_subscriber_parser.add_argument("--issue-number", type=int, required=True)

pr_subscriber_parser = subparsers.add_parser("pr-subscriber")
pr_subscriber_parser.add_argument("--label-name", type=str, required=True)
pr_subscriber_parser.add_argument("--issue-number", type=int, required=True)

pr_greeter_parser = subparsers.add_parser("pr-greeter")
pr_greeter_parser.add_argument("--issue-number", type=int, required=True)

release_workflow_parser = subparsers.add_parser("release-workflow")
release_workflow_parser.add_argument(
    "--llvm-project-dir",
    type=str,
    default=".",
    help="directory containing the llvm-project checout",
)
release_workflow_parser.add_argument(
    "--issue-number", type=int, required=True, help="The issue number to update"
)
release_workflow_parser.add_argument(
    "--phab-token",
    type=str,
    help="Phabricator conduit API token. See https://reviews.llvm.org/settings/user/<USER>/page/apitokens/",
)
release_workflow_parser.add_argument(
    "--branch-repo-token",
    type=str,
    help="GitHub authentication token to use for the repository where new branches will be pushed. Defaults to TOKEN.",
)
release_workflow_parser.add_argument(
    "--branch-repo",
    type=str,
    default="llvm/llvm-project-release-prs",
    help="The name of the repo where new branches will be pushed (e.g. llvm/llvm-project)",
)
release_workflow_parser.add_argument(
    "sub_command",
    type=str,
    choices=["print-release-branch", "auto"],
    help="Print to stdout the name of the release branch ISSUE_NUMBER should be backported to",
)

llvmbot_git_config_parser = subparsers.add_parser(
    "setup-llvmbot-git",
    help="Set the default user and email for the git repo in LLVM_PROJECT_DIR to llvmbot",
)

args = parser.parse_args()

if args.command == "issue-subscriber":
    issue_subscriber = IssueSubscriber(
        args.token, args.repo, args.issue_number, args.label_name
    )
    issue_subscriber.run()
elif args.command == "pr-subscriber":
    pr_subscriber = PRSubscriber(
        args.token, args.repo, args.issue_number, args.label_name
    )
    pr_subscriber.run()
elif args.command == "pr-greeter":
    pr_greeter = PRGreeter(args.token, args.repo, args.issue_number)
    pr_greeter.run()
elif args.command == "release-workflow":
    release_workflow = ReleaseWorkflow(
        args.token,
        args.repo,
        args.issue_number,
        args.branch_repo,
        args.branch_repo_token,
        args.llvm_project_dir,
        args.phab_token,
    )
    if not release_workflow.release_branch_for_issue:
        release_workflow.issue_notify_no_milestone(sys.stdin.readlines())
        sys.exit(1)
    if args.sub_command == "print-release-branch":
        release_workflow.print_release_branch()
    else:
        if not release_workflow.execute_command():
            sys.exit(1)
elif args.command == "setup-llvmbot-git":
    setup_llvmbot_git()