#!/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. This script is a modified version
of the one created by the Kafka project (https://github.com/apache/kafka/blob/trunk/kafka-merge-pr.py).

  Usage: ./samza-merge-pr.py (see config env vars below)

This utility assumes you already have local a samza git folder and that you have added remotes corresponding to both:
  (i) the github apache samza mirror and
  (ii) the apache samza git repo.

Note:
    This script has been borrowed from the Apache Kafka team that can be found here:
    https://github.com/apache/kafka/blob/trunk/kafka-merge-pr.py
    It has been modified for the Apache Samza project.
"""

import json
import os
import re
import subprocess
import sys
import urllib2

try:
    import jira.client

    JIRA_IMPORTED = True
except ImportError:
    JIRA_IMPORTED = False

PROJECT_NAME = "samza"
CAPITALIZED_PROJECT_NAME = "samza".upper()

# Remote name which points to the GitHub site
PR_REMOTE_NAME = os.environ.get("PR_REMOTE_NAME", "samza-github")
# Remote name which points to Apache git
PUSH_REMOTE_NAME = os.environ.get("PUSH_REMOTE_NAME", "samza-apache")
# ASF JIRA username
JIRA_USERNAME = os.environ.get("JIRA_USERNAME", "")
# ASF JIRA password
JIRA_PASSWORD = os.environ.get("JIRA_PASSWORD", "")

"""
OAuth key used for issuing requests against the GitHub API. If this is not defined, then requests
will be unauthenticated. You should only need to configure this if you find yourself regularly
exceeding your IP's unauthenticated request rate limit. You can create an OAuth key at
https://github.com/settings/tokens. This script only requires the "public_repo" scope.
"""
GITHUB_OAUTH_KEY = os.environ.get("GITHUB_OAUTH_KEY", "")

GITHUB_BASE = "https://github.com/apache/%s/pull" % (PROJECT_NAME)
GITHUB_API_BASE = "https://api.github.com/repos/apache/%s" % (PROJECT_NAME)
JIRA_BASE = "https://issues.apache.org/jira/browse"
JIRA_API_BASE = "https://issues.apache.org/jira"
# Prefix added to temporary branches
TEMP_BRANCH_PREFIX = "PR_TOOL"


def get_json(url):
    try:
        request = urllib2.Request(url)
        if GITHUB_OAUTH_KEY:
            request.add_header('Authorization', 'token %s' % GITHUB_OAUTH_KEY)
        return json.load(urllib2.urlopen(request))
    except urllib2.HTTPError as e:
        if "X-RateLimit-Remaining" in e.headers and e.headers["X-RateLimit-Remaining"] == '0':
            print "Exceeded the GitHub API rate limit; see the instructions in " + \
                  "samza-merge-pr.py to configure an OAuth token for making authenticated " + \
                  "GitHub requests."
        else:
            print "Unable to fetch URL, exiting: %s" % url
        sys.exit(-1)


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


def run_cmd(cmd):
    if isinstance(cmd, list):
        # Add debugging information on the command being run.
        print " ".join(cmd)
        return subprocess.check_output(cmd)
    else:
        print cmd
        return subprocess.check_output(cmd.split(" "))


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


def clean_up():
    if original_head != get_current_branch():
        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(TEMP_BRANCH_PREFIX), branches):
        print "Deleting local branch %s" % branch
        run_cmd("git branch -D %s" % branch)


def get_current_branch():
    return run_cmd("git rev-parse --abbrev-ref HEAD").replace("\n", "")

def merge_pr(pr_num, target_ref, title, body, pr_repo_desc):
    """
    Merge the requested Pull Request number
    Returns the Merge Hash

    :param pr_num: Pull Request Number
    :param target_ref:
    :param title: Commit title
    :param body:
    :param pr_repo_desc:
    :return:
    """
    pr_branch_name = "%s_MERGE_PR_%s" % (TEMP_BRANCH_PREFIX, pr_num)
    target_branch_name = "%s_MERGE_PR_%s_%s" % (TEMP_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 = raw_input(
        "Enter primary author in the format of \"name <email>\" [%s]: " %
        distinct_authors[0])
    if primary_author == "":
        primary_author = distinct_authors[0]

    reviewers = raw_input(
        "Enter reviewers in the format of \"name1 <email1>, name2 <email2>\": ").strip()

    commits = run_cmd(['git', 'log', 'HEAD..%s' % pr_branch_name,
                       '--pretty=format:%h [%an] %s']).split("\n")

    if len(commits) > 1:
        result = raw_input("List pull request commits in squashed commit message? (y/n): ")
        if result.lower() == "y":
            should_list_commits = True
        else:
            should_list_commits = False
    else:
        should_list_commits = False

    merge_message_flags = []

    merge_message_flags += ["-m", title]
    if body is not None:
        # We remove @ symbols from the body to avoid triggering e-mails
        # to people every time someone creates a public fork of the project.
        merge_message_flags += ["-m", body.replace("@", "")]

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

    merge_message_flags += ["-m", authors]

    if (reviewers != ""):
        merge_message_flags += ["-m", "Reviewers: %s" % reviewers]

    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
    close_line = "Closes #%s from %s" % (pr_num, pr_repo_desc)
    if should_list_commits:
        close_line += " and squashes the following commits:"
    merge_message_flags += ["-m", close_line]

    if should_list_commits:
        merge_message_flags += ["-m", "\n".join(commits)]

    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" % (TEMP_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)

    try:
        run_cmd("git cherry-pick -sx %s" % merge_hash)
    except Exception as e:
        msg = "Error cherry-picking: %s\nWould you like to manually fix-up this merge?" % e
        continue_maybe(msg)
        msg = "Okay, please fix any conflicts and finish the cherry-pick. Finished?"
        continue_maybe(msg)

    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):
    """
    Returns fix-version from the branch names
    :param branch:
    :param versions: List of sorted (newest->oldest) list of unrelease versions (includes "master" branch)
    :return: Returns "master" if the current branch is master. Otherwise, it returns the oldest branch version
            that starts with "master". Else, it returns None.
    """
    if branch == "master":
        if len(versions) > 0:
            return versions[0]
        else:
            return None
    else:
        return filter(lambda x: x.startswith(branch), versions)[-1]


def resolve_jira_issue(title, merge_branches, comment):
    """
    Updates the assignee (if not already provided) and fix-versions before resolving the JIRA

    :param title: Standardized commit title
    :param merge_branches: Default fix-versions for this JIRA
    :param comment: Comment added to the JIRA
    """
    asf_jira = jira.client.JIRA({'server': JIRA_API_BASE},
                                basic_auth=(JIRA_USERNAME, JIRA_PASSWORD))
    default_jira_id = ""
    jira_ids = re.findall("%s-[0-9]{4,5}" % CAPITALIZED_PROJECT_NAME, title)
    if len(jira_ids) > 0:
        default_jira_id = jira_ids[0]

    jira_id = raw_input("Enter a JIRA id [%s]: " % default_jira_id)
    if jira_id == "":
        jira_id = default_jira_id

    try:
        issue = asf_jira.issue(jira_id)
    except Exception as e:
        fail("ASF JIRA could not find %s\n%s" % (jira_id, e))

    cur_status = issue.fields.status.name
    cur_summary = issue.fields.summary
    cur_assignee = issue.fields.assignee
    if cur_assignee is None:
        cur_assignee = "NOT ASSIGNED!!!"
    else:
        cur_assignee = cur_assignee.displayName

    if cur_status == "Resolved" or cur_status == "Closed":
        fail("JIRA issue %s already has status '%s'" % (jira_id, cur_status))
    print ("=== JIRA %s ===" % jira_id)
    print ("summary\t\t%s\nassignee\t%s\nstatus\t\t%s\nurl\t\t%s/%s\n" % (
        cur_summary, cur_assignee, cur_status, JIRA_BASE, jira_id))

    versions = asf_jira.project_versions(CAPITALIZED_PROJECT_NAME)
    versions = sorted(versions, key=lambda x: x.name, reverse=True)
    versions = filter(lambda x: x.raw['released'] is False, versions)

    version_names = map(lambda x: x.name, versions)
    default_fix_versions = map(lambda x: fix_version_from_branch(x, version_names), merge_branches)
    default_fix_versions = filter(lambda x: x != None, default_fix_versions)
    default_fix_versions = ",".join(default_fix_versions)

    fix_versions = raw_input("Enter comma-separated fix version(s) [%s]: " % default_fix_versions)
    if fix_versions == "":
        fix_versions = default_fix_versions
    fix_versions = fix_versions.replace(" ", "").split(",")

    def get_version_json(version_str):
        return filter(lambda v: v.name == version_str, versions)[0].raw

    jira_fix_versions = map(lambda v: get_version_json(v), fix_versions)

    resolve = filter(lambda a: a['name'] == "Resolve Issue", asf_jira.transitions(jira_id))[0]
    resolution = filter(lambda r: r.raw['name'] == "Fixed", asf_jira.resolutions())[0]
    asf_jira.transition_issue(
        jira_id, resolve["id"], fixVersions=jira_fix_versions,
        comment=comment, resolution={'id': resolution.raw['id']})

    print "Successfully resolved %s with fixVersions=%s!" % (jira_id, fix_versions)


def standardize_jira_ref(text):
    """
    Standardize the jira reference commit message prefix to "PROJECT_NAME-XXX: Issue"
    >>> standardize_jira_ref("%s-5954: Top by key" % CAPITALIZED_PROJECT_NAME)
    'SAMZA-5954: Top by key'
    >>> standardize_jira_ref("%s-5821: ParquetRelation2 CTAS should check if delete is successful" % PROJECT_NAME)
    'SAMZA-5821: ParquetRelation2 CTAS should check if delete is successful'
    >>> standardize_jira_ref("%s-4123 [WIP] Show new dependencies added in pull requests" % PROJECT_NAME)
    'SAMZA-4123: [WIP] Show new dependencies added in pull requests'
    >>> standardize_jira_ref("%s  5954: Top by key" % PROJECT_NAME)
    'SAMZA-5954: Top by key'
    >>> standardize_jira_ref("%s-979 a LRU scheduler for load balancing in TaskSchedulerImpl" % PROJECT_NAME)
    'SAMZA-979: a LRU scheduler for load balancing in TaskSchedulerImpl'
    >>> standardize_jira_ref("%s-1094 Support MiMa for reporting binary compatibility across versions." % CAPITALIZED_PROJECT_NAME)
    'SAMZA-1094: Support MiMa for reporting binary compatibility across versions.'
    >>> standardize_jira_ref("[WIP] %s-1146: Vagrant support" % CAPITALIZED_PROJECT_NAME)
    'SAMZA-1146: [WIP] Vagrant support'
    >>> standardize_jira_ref("%s-1032. If Yarn app fails before registering, app master stays aroun..." % PROJECT_NAME)
    'SAMZA-1032: If Yarn app fails before registering, app master stays aroun...'
    >>> standardize_jira_ref("%s-6250 %s-6146 %s-5911: Types are now reserved words in DDL parser." % (PROJECT_NAME, PROJECT_NAME, CAPITALIZED_PROJECT_NAME))
    'SAMZA-6250 SAMZA-6146 SAMZA-5911: Types are now reserved words in DDL parser.'
    >>> standardize_jira_ref("Additional information for users building from source code")
    'Additional information for users building from source code'

    :param text: Text provided that will be used a commit message
    :return: Standardized commit message that includes the JIRA number as well
    """
    jira_refs = []
    components = []

    # Extract JIRA ref(s):
    pattern = re.compile(r'(%s[-\s]*[0-9]{3,6})+' % CAPITALIZED_PROJECT_NAME, re.IGNORECASE)
    for ref in pattern.findall(text):
        # Add brackets, replace spaces with a dash, & convert to uppercase
        jira_refs.append(re.sub(r'\s+', '-', ref.upper()))
        text = text.replace(ref, '')

    # Extract project name component(s):
    # Look for alphanumeric chars, spaces, dashes, periods, and/or commas
    pattern = re.compile(r'(\[[\w\s,-\.]+\])', re.IGNORECASE)
    for component in pattern.findall(text):
        components.append(component.upper())
        text = text.replace(component, '')

    # Cleanup any remaining symbols:
    pattern = re.compile(r'^\W+(.*)', re.IGNORECASE)
    if (pattern.search(text) is not None):
        text = pattern.search(text).groups()[0]

    # Assemble full text (JIRA ref(s), module(s), remaining text)
    jira_prefix = ' '.join(jira_refs).strip()
    if jira_prefix:
        jira_prefix = jira_prefix + ": "
    clean_text = jira_prefix + ' '.join(components).strip() + " " + text.strip()

    # Replace multiple spaces with a single space, e.g. if no jira refs and/or components were included
    clean_text = re.sub(r'\s+', ' ', clean_text.strip())

    return clean_text


def main():
    global original_head

    original_head = get_current_branch()

    latest_branch = "master"

    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))
    pr_events = get_json("%s/issues/%s/events" % (GITHUB_API_BASE, pr_num))

    url = pr["url"]

    pr_title = pr["title"]
    commit_title = raw_input("Commit title [%s]: " % pr_title.encode("utf-8")).decode("utf-8")
    if commit_title == "":
        commit_title = pr_title

    # Decide whether to use the modified title or not
    modified_title = standardize_jira_ref(commit_title)
    if modified_title != commit_title:
        print "I've re-written the title as follows to match the standard format:"
        print "Original: %s" % commit_title
        print "Modified: %s" % modified_title
        result = raw_input("Would you like to use the modified title? (y/n): ")
        if result.lower() == "y":
            commit_title = modified_title
            print "Using modified title:"
        else:
            print "Using original title:"
        print commit_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)

    # Merged pull requests don't appear as merged in the GitHub API;
    # Instead, they're closed by asfgit.
    merge_commits = \
        [e for e in pr_events if e["actor"]["login"] == "asfgit" and e["event"] == "closed"]

    if merge_commits:
        merge_hash = merge_commits[0]["commit_id"]
        message = get_json("%s/commits/%s" % (GITHUB_API_BASE, merge_hash))["commit"]["message"]

        print "Pull request %s has already been merged, assuming you want to backport" % pr_num
        commit_is_downloaded = run_cmd(['git', 'rev-parse', '--quiet', '--verify',
                                        "%s^{commit}" % merge_hash]).strip() != ""
        if not commit_is_downloaded:
            fail("Couldn't find any merge commit for #%s, you may need to update HEAD." % pr_num)

        print "Found commit %s:\n%s" % (merge_hash, message)
        cherry_pick(pr_num, merge_hash, latest_branch)
        sys.exit(0)

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

    print ("\n=== Pull Request #%s ===" % pr_num)
    print ("PR title\t%s\nCommit title\t%s\nSource\t\t%s\nTarget\t\t%s\nURL\t\t%s" % (
        pr_title, commit_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, commit_title, body, pr_repo_desc)

    pick_prompt = "Would you like to pick %s into another branch?" % merge_hash
    while raw_input("\n%s (y/n): " % pick_prompt).lower() == "y":
        merged_refs = merged_refs + [cherry_pick(pr_num, merge_hash, latest_branch)]

    if JIRA_IMPORTED:
        if JIRA_USERNAME and JIRA_PASSWORD:
            continue_maybe("Would you like to update an associated JIRA?")
            jira_comment = "Issue resolved by pull request %s\n[%s/%s]" % (pr_num, GITHUB_BASE, pr_num)
            resolve_jira_issue(commit_title, merged_refs, jira_comment)
        else:
            print "JIRA_USERNAME and JIRA_PASSWORD not set"
            print "Exiting without trying to close the associated JIRA."
    else:
        print "Could not find jira-python library. Run 'sudo pip install jira' to install."
        print "Exiting without trying to close the associated JIRA."


if __name__ == "__main__":
    main()