#!/usr/bin/env python

#
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements.  See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License.  You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

# Utility for creating well-formed pull request merges and pushing them to
# Apache.
#   usage: ./apache-pr-merge.py    (see config env vars below)
#
# Lightly modified from version of this script in incubator-parquet-format

from __future__ import print_function

from requests.auth import HTTPBasicAuth
import requests

import os
import six
import subprocess
import sys
import textwrap

PANDAS_HOME = '.'
PROJECT_NAME = 'pandas'
print("PANDAS_HOME = " + PANDAS_HOME)

# Remote name with the PR
PR_REMOTE_NAME = os.environ.get("PR_REMOTE_NAME", "upstream")

# Remote name where results pushed
PUSH_REMOTE_NAME = os.environ.get("PUSH_REMOTE_NAME", "upstream")

GITHUB_BASE = "https://github.com/pydata/" + PROJECT_NAME + "/pull"
GITHUB_API_BASE = "https://api.github.com/repos/pydata/" + PROJECT_NAME

# Prefix added to temporary branches
BRANCH_PREFIX = "PR_TOOL"

os.chdir(PANDAS_HOME)

auth_required = False

if auth_required:
    GITHUB_USERNAME = os.environ['GITHUB_USER']
    import getpass
    GITHUB_PASSWORD = getpass.getpass('Enter github.com password for %s:'
                                      % GITHUB_USERNAME)

    def get_json_auth(url):
        auth = HTTPBasicAuth(GITHUB_USERNAME, GITHUB_PASSWORD)
        req = requests.get(url, auth=auth)
        return req.json()

    get_json = get_json_auth
else:
    def get_json_no_auth(url):
        req = requests.get(url)
        return req.json()

    get_json = get_json_no_auth


def fail(msg):
    print(msg)
    clean_up()
    sys.exit(-1)


def run_cmd(cmd):
    # py2.6 does not have subprocess.check_output
    if isinstance(cmd, six.string_types):
        cmd = cmd.split(' ')

    popenargs = [cmd]
    kwargs = {}

    process = subprocess.Popen(stdout=subprocess.PIPE, *popenargs)
    output, unused_err = process.communicate()
    retcode = process.poll()
    if retcode:
        cmd = kwargs.get("args")
        if cmd is None:
            cmd = popenargs[0]
        raise subprocess.CalledProcessError(retcode, cmd, output=output)
    return output


def continue_maybe(prompt):
    result = raw_input("\n%s (y/n): " % prompt)
    if result.lower() != "y":
        fail("Okay, exiting")


original_head = run_cmd("git rev-parse HEAD")[:8]


def clean_up():
    print("Restoring head pointer to %s" % original_head)
    run_cmd("git checkout %s" % original_head)

    branches = run_cmd("git branch").replace(" ", "").split("\n")

    for branch in filter(lambda x: x.startswith(BRANCH_PREFIX), branches):
        print("Deleting local branch %s" % branch)
        run_cmd("git branch -D %s" % branch)


# merge the requested PR and return the merge hash
def merge_pr(pr_num, target_ref):
    pr_branch_name = "%s_MERGE_PR_%s" % (BRANCH_PREFIX, pr_num)
    target_branch_name = "%s_MERGE_PR_%s_%s" % (BRANCH_PREFIX, pr_num,
                                                target_ref.upper())
    run_cmd("git fetch %s pull/%s/head:%s" % (PR_REMOTE_NAME, pr_num,
                                              pr_branch_name))
    run_cmd("git fetch %s %s:%s" % (PUSH_REMOTE_NAME, target_ref,
                                    target_branch_name))
    run_cmd("git checkout %s" % target_branch_name)

    had_conflicts = False
    try:
        run_cmd(['git', 'merge', pr_branch_name, '--squash'])
    except Exception as e:
        msg = ("Error merging: %s\nWould you like to manually fix-up "
               "this merge?" % e)
        continue_maybe(msg)
        msg = ("Okay, please fix any conflicts and 'git add' "
               "conflicting files... Finished?")
        continue_maybe(msg)
        had_conflicts = True

    commit_authors = run_cmd(['git', 'log', 'HEAD..%s' % pr_branch_name,
                             '--pretty=format:%an <%ae>']).split("\n")
    distinct_authors = sorted(set(commit_authors),
                              key=lambda x: commit_authors.count(x),
                              reverse=True)
    primary_author = distinct_authors[0]
    commits = run_cmd(['git', 'log', 'HEAD..%s' % pr_branch_name,
                      '--pretty=format:%h [%an] %s']).split("\n\n")

    merge_message_flags = []

    merge_message_flags += ["-m", title]
    if body is not None:
        merge_message_flags += ["-m", '\n'.join(textwrap.wrap(body))]

    authors = "\n".join(["Author: %s" % a for a in distinct_authors])

    merge_message_flags += ["-m", authors]

    if had_conflicts:
        committer_name = run_cmd("git config --get user.name").strip()
        committer_email = run_cmd("git config --get user.email").strip()
        message = ("This patch had conflicts when merged, "
                   "resolved by\nCommitter: %s <%s>"
                   % (committer_name, committer_email))
        merge_message_flags += ["-m", message]

    # The string "Closes #%s" string is required for GitHub to correctly close
    # the PR
    merge_message_flags += [
        "-m",
        "Closes #%s from %s and squashes the following commits:"
        % (pr_num, pr_repo_desc)]
    for c in commits:
        merge_message_flags += ["-m", c]

    run_cmd(['git', 'commit', '--author="%s"' % primary_author] +
            merge_message_flags)

    continue_maybe("Merge complete (local ref %s). Push to %s?" % (
        target_branch_name, PUSH_REMOTE_NAME))

    try:
        run_cmd('git push %s %s:%s' % (PUSH_REMOTE_NAME, target_branch_name,
                                       target_ref))
    except Exception as e:
        clean_up()
        fail("Exception while pushing: %s" % e)

    merge_hash = run_cmd("git rev-parse %s" % target_branch_name)[:8]
    clean_up()
    print("Pull request #%s merged!" % pr_num)
    print("Merge hash: %s" % merge_hash)
    return merge_hash


def cherry_pick(pr_num, merge_hash, default_branch):
    pick_ref = raw_input("Enter a branch name [%s]: " % default_branch)
    if pick_ref == "":
        pick_ref = default_branch

    pick_branch_name = "%s_PICK_PR_%s_%s" % (BRANCH_PREFIX, pr_num,
                                             pick_ref.upper())

    run_cmd("git fetch %s %s:%s" % (PUSH_REMOTE_NAME, pick_ref,
                                    pick_branch_name))
    run_cmd("git checkout %s" % pick_branch_name)
    run_cmd("git cherry-pick -sx %s" % merge_hash)

    continue_maybe("Pick complete (local ref %s). Push to %s?" % (
        pick_branch_name, PUSH_REMOTE_NAME))

    try:
        run_cmd('git push %s %s:%s' % (PUSH_REMOTE_NAME, pick_branch_name,
                                       pick_ref))
    except Exception as e:
        clean_up()
        fail("Exception while pushing: %s" % e)

    pick_hash = run_cmd("git rev-parse %s" % pick_branch_name)[:8]
    clean_up()

    print("Pull request #%s picked into %s!" % (pr_num, pick_ref))
    print("Pick hash: %s" % pick_hash)
    return pick_ref


def fix_version_from_branch(branch, versions):
    #  Note: Assumes this is a sorted (newest->oldest) list of un-released
    #  versions
    if branch == "master":
        return versions[0]
    else:
        branch_ver = branch.replace("branch-", "")
        return filter(lambda x: x.name.startswith(branch_ver), versions)[-1]


# branches = get_json("%s/branches" % GITHUB_API_BASE)
# branch_names = filter(lambda x: x.startswith("branch-"),
#                       [x['name'] for x in branches])
# Assumes branch names can be sorted lexicographically
# latest_branch = sorted(branch_names, reverse=True)[0]

pr_num = raw_input("Which pull request would you like to merge? (e.g. 34): ")
pr = get_json("%s/pulls/%s" % (GITHUB_API_BASE, pr_num))

url = pr["url"]
title = pr["title"]
body = pr["body"]
target_ref = pr["base"]["ref"]
user_login = pr["user"]["login"]
base_ref = pr["head"]["ref"]
pr_repo_desc = "%s/%s" % (user_login, base_ref)

if pr["merged"] is True:
    print("Pull request {0} has already been merged, please backport manually"
          .format(pr_num))
    sys.exit(0)

if not bool(pr["mergeable"]):
    msg = ("Pull request {0} is not mergeable in its current form.\n"
           "Continue? (experts only!)".format(pr_num))
    continue_maybe(msg)

print("\n=== Pull Request #%s ===" % pr_num)
print("title\t%s\nsource\t%s\ntarget\t%s\nurl\t%s"
      % (title, pr_repo_desc, target_ref, url))
continue_maybe("Proceed with merging pull request #%s?" % pr_num)

merged_refs = [target_ref]

merge_hash = merge_pr(pr_num, target_ref)
