#!/usr/bin/env python3
# -*- coding: utf-8 -*-"
#
# Copyright 2020 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Find missing stable and backported mainline fix patches in chromeos."""

from __future__ import print_function
import logging
import os
import subprocess
import sys

import MySQLdb
import common
import cloudsql_interface
import gerrit_interface
import git_interface


# Constant representing number CL's we want created on single new missing patch run
NEW_CL_DAILY_LIMIT_PER_STABLE_BRANCH = 2
NEW_CL_DAILY_LIMIT_PER_BRANCH = 1


def get_status_from_cherrypicking_sha(branch, fixer_upstream_sha):
    """Cherrypick fixer sha into it's linux_chrome branch and determine its Status.

    Return Status Enum:
    MERGED if the patch has already been applied,
    OPEN if the patch is missing and applies cleanly,
    CONFLICT if the patch is missing and fails to apply.
    """
    # Save current working directory
    cwd = os.getcwd()

    # Switch to chrome directory to apply cherry-pick
    chrome_absolute_path = common.get_kernel_absolute_path(common.CHROMEOS_PATH)
    chromeos_branch = common.chromeos_branch(branch)

    os.chdir(chrome_absolute_path)
    git_interface.checkout_and_clean(chrome_absolute_path, chromeos_branch)

    ret = None
    try:
        fix_in_chrome = search_upstream_subject_in_linux_chrome(branch, fixer_upstream_sha)
        if fix_in_chrome:
            ret = common.Status.MERGED
            raise ValueError

        result = subprocess.call(['git', 'cherry-pick', '-n', fixer_upstream_sha],
                stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
        if result:
            ret = common.Status.CONFLICT
            raise ValueError

        diff = subprocess.check_output(['git', 'diff', 'HEAD'])
        if diff:
            ret = common.Status.OPEN
            raise ValueError

        ret = common.Status.MERGED
    except ValueError:
        pass
    except subprocess.CalledProcessError:
        ret = common.Status.CONFLICT
    finally:
        git_interface.checkout_and_clean(chrome_absolute_path, chromeos_branch)
        os.chdir(cwd)

    return ret


def search_upstream_subject_in_linux_chrome(branch, upstream_sha):
    """Check if upstream_sha subject line is in linux_chrome.

    Assumes function is run from correct directory/branch.
    TODO(*): Add more complicated matching between upstream sha's that are merged into chromeos
        i.e fuzzy matching descriptions
    """
    subject = None
    try:
        # Retrieve subject line of upstream_sha.
        cmd = ['git', 'log', '--pretty=format:%s', '-n', '1', upstream_sha]
        subject = subprocess.check_output(cmd, encoding='utf-8', errors='ignore')
    except subprocess.CalledProcessError:
        logging.error('Error locating subject line of upstream sha %s', upstream_sha)
        raise

    try:
        cmd = ['git', 'log', '--no-merges', '--grep', subject, 'v%s..' % branch]
        result = subprocess.check_output(cmd)
        return bool(result)
    except subprocess.CalledProcessError:
        logging.error('Error while searching for subject line %s in linux_chrome', subject)
        raise


def upstream_sha_to_kernel_sha(db, chosen_table, branch, upstream_sha):
    """Retrieves chromeos/stable sha by indexing db.

    Returns sha or None if upstream sha doesn't exist downstream.
    """
    c = db.cursor()

    q = """SELECT sha
            FROM {chosen_table}
            WHERE branch = %s
            AND (upstream_sha = %s
                OR patch_id IN (
                    SELECT patch_id
                    FROM linux_upstream
                    WHERE sha = %s
                ))""".format(chosen_table=chosen_table)
    c.execute(q, [branch, upstream_sha, upstream_sha])
    row = c.fetchone()

    return row[0] if row else None


def insert_by_patch_id(db, branch, fixedby_upstream_sha):
    """Handles case where fixedby_upstream_sha may have changed in kernels.

    Returns True if successful patch_id insertion and False if patch_id not found.
    """
    c = db.cursor()

    # Commit sha may have been modified in cherry-pick, backport, etc.
    # Retrieve SHA in linux_chrome by patch-id by checking for fixedby_upstream_sha
    #  removes entries that are already tracked in chrome_fixes
    q = """SELECT lc.sha
            FROM linux_chrome AS lc
            JOIN linux_upstream AS lu
            ON lc.patch_id = lu.patch_id
            JOIN upstream_fixes as uf
            ON lc.upstream_sha = uf.upstream_sha
            WHERE uf.fixedby_upstream_sha = %s AND branch = %s
            AND (lc.sha, uf.fixedby_upstream_sha)
            NOT IN (
                SELECT kernel_sha, fixedby_upstream_sha
                FROM chrome_fixes
                WHERE branch = %s
            )"""
    c.execute(q, [fixedby_upstream_sha, branch, branch])
    chrome_shas = c.fetchall()

    # fixedby_upstream_sha has already been merged into linux_chrome
    #  chrome shas represent kernel sha for the upstream_sha fixedby_upstream_sha
    if chrome_shas:
        for chrome_sha in chrome_shas:
            entry_time = common.get_current_time()
            cl_status = common.Status.MERGED.name
            reason = 'Already merged into linux_chrome [upstream sha %s]' % fixedby_upstream_sha

            try:
                q = """INSERT INTO chrome_fixes
                        (kernel_sha, fixedby_upstream_sha, branch, entry_time,
                        close_time, initial_status, status, reason)
                        VALUES (%s, %s, %s, %s, %s, %s, %s, %s)"""
                c.execute(q, [chrome_sha, fixedby_upstream_sha, branch, entry_time,
                                entry_time, cl_status, cl_status, reason])
                db.commit()
            except MySQLdb.Error as e: # pylint: disable=no-member
                logging.error(
                    'Failed to insert an already merged entry into chrome_fixes: error %d(%s)',
                    e.args[0], e.args[1])
        return True

    return False


def insert_fix_gerrit(db, chosen_table, chosen_fixes, branch, kernel_sha, fixedby_upstream_sha):
    """Inserts fix row by checking status of applying a fix change.

    Return True if we create a new Gerrit CL, otherwise return False.
    """
    # Check if fix has been merged using it's patch-id since sha's might've changed
    success = insert_by_patch_id(db, branch, fixedby_upstream_sha)
    created_new_change = False
    if success:
        return created_new_change

    c = db.cursor()

    # Try applying patch and get status
    status = get_status_from_cherrypicking_sha(branch, fixedby_upstream_sha)
    cl_status = status.name

    entry_time = common.get_current_time()

    close_time = fix_change_id = reason = None

    q = """INSERT INTO {chosen_fixes}
            (kernel_sha, fixedby_upstream_sha, branch, entry_time, close_time,
            fix_change_id, initial_status, status, reason)
            VALUES (%s, %s, %s, %s, %s, %s, %s, %s, %s)""".format(chosen_fixes=chosen_fixes)

    if status == common.Status.MERGED:
        # Create a row for the merged CL (we don't need to track this), but can be stored
        # to indicate that the changes of this patch are already merged
        # entry_time and close_time are the same since we weren't tracking when it was merged
        fixedby_kernel_sha = upstream_sha_to_kernel_sha(db, chosen_table,
                branch, fixedby_upstream_sha)
        logging.info('%s SHA [%s] already merged bugfix patch [kernel: %s] [upstream: %s]',
                     chosen_fixes, kernel_sha, fixedby_kernel_sha, fixedby_upstream_sha)

        reason = 'Patch applied to linux_chrome before this robot was run'
        close_time = entry_time

        # linux_chrome will have change-id's but stable merged fixes will not
        # Correctly located fixedby_kernel_sha in linux_chrome
        if chosen_table == 'linux_chrome' and fixedby_kernel_sha:
            fix_change_id = git_interface.get_commit_changeid_linux_chrome(fixedby_kernel_sha)
    elif status == common.Status.OPEN:
        fix_change_id = gerrit_interface.create_change(kernel_sha, fixedby_upstream_sha, branch)
        created_new_change = bool(fix_change_id)

        # Checks if change was created successfully
        if not created_new_change:
            logging.error('Failed to create change for kernel_sha %s fixed by %s',
                          kernel_sha, fixedby_upstream_sha)
            return False
    elif status == common.Status.CONFLICT:
        # Register conflict entry_time, do not create gerrit CL
        # Requires engineer to manually explore why CL doesn't apply cleanly
        pass

    try:
        c.execute(q, [kernel_sha, fixedby_upstream_sha, branch, entry_time,
                        close_time, fix_change_id, cl_status, cl_status, reason])
        logging.info('Inserted row into fixes table %s %s %s %s %s %s %s %s %s',
                     chosen_fixes, kernel_sha, fixedby_upstream_sha, branch,
                     entry_time, close_time, fix_change_id, cl_status, reason)

    except MySQLdb.Error as e: # pylint: disable=no-member
        logging.error(
            'Error inserting fix CL into fixes table %s %s %s %s %s %s %s %s %s: error %d(%s)',
            chosen_fixes, kernel_sha, fixedby_upstream_sha, branch,
            entry_time, close_time, fix_change_id, cl_status, reason,
            e.args[0], e.args[1])
    return created_new_change


def fixup_unmerged_patches(db, branch, kernel_metadata):
    """Fixup script that attempts to reapply unmerged fixes to get latest status.

    2 main actions performed by script include:
        1) Handle case where a conflicting CL later can be applied cleanly without merge conflicts
        2) Detect if the fix has been applied to linux_chrome externally
            (i.e not merging through a fix created by this robot)
    """
    c = db.cursor()
    fixes_table = kernel_metadata.kernel_fixes_table

    q = """SELECT kernel_sha, fixedby_upstream_sha, status, fix_change_id
            FROM {fixes_table}
            WHERE status != 'MERGED'
            AND branch = %s""".format(fixes_table=fixes_table)
    c.execute(q, [branch])
    rows = c.fetchall()
    for row in rows:
        kernel_sha, fixedby_upstream_sha, status, fix_change_id = row

        new_status_enum = get_status_from_cherrypicking_sha(branch, fixedby_upstream_sha)
        new_status = new_status_enum.name

        if status == 'CONFLICT' and new_status == 'OPEN':
            fix_change_id = gerrit_interface.create_change(kernel_sha, fixedby_upstream_sha, branch)

            # Check if we successfully created the fix patch before performing update
            if fix_change_id:
                cloudsql_interface.update_conflict_to_open(db, fixes_table,
                                        kernel_sha, fixedby_upstream_sha, fix_change_id)
        elif new_status == 'MERGED':
            reason = 'Fix was merged externally and detected by robot.'
            if fix_change_id:
                gerrit_interface.abandon_change(fix_change_id, branch, reason)
            cloudsql_interface.update_change_merged(db, fixes_table,
                                        kernel_sha, fixedby_upstream_sha, reason)


def update_fixes_in_branch(db, branch, kernel_metadata, limit):
    """Updates fix patch table row by determining if CL merged into linux_chrome."""
    del limit # unused here

    c = db.cursor()
    chosen_fixes = kernel_metadata.kernel_fixes_table

    # Old rows to Update
    q = """UPDATE {chosen_fixes} AS fixes
           JOIN linux_chrome AS lc
           ON fixes.fixedby_upstream_sha = lc.upstream_sha
           SET status = 'MERGED', close_time = %s, reason = %s
           WHERE fixes.branch = %s
           AND lc.branch = %s
           AND (fixes.status = 'OPEN'
                OR fixes.status = 'CONFLICT'
                OR fixes.status = 'ABANDONED')""".format(chosen_fixes=chosen_fixes)

    close_time = common.get_current_time()
    reason = 'Patch has been applied to linux_chome'

    try:
        c.execute(q, [close_time, reason, branch, branch])
        logging.info(
            'Updating rows that have been merged into linux_chrome in table %s / branch %s',
            chosen_fixes, branch)
    except MySQLdb.Error as e: # pylint: disable=no-member
        logging.error('Error updating fixes table for merged commits %s %s %s %s: %d(%s)',
                      chosen_fixes, close_time, reason, branch, e.args[0], e.args[1])
    db.commit()

    # Sync status of unmerged patches in a branch
    fixup_unmerged_patches(db, branch, kernel_metadata)


def create_new_fixes_in_branch(db, branch, kernel_metadata, limit):
    """Look for missing Fixup commits in provided chromeos or stable release."""
    c = db.cursor()
    branch_name = kernel_metadata.get_kernel_branch(branch)

    logging.info('Checking branch %s', branch_name)
    subprocess.run(['git', 'checkout', branch_name], check=True,
            stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)

    # chosen_table is either linux_stable or linux_chrome
    chosen_table = kernel_metadata.path
    chosen_fixes = kernel_metadata.kernel_fixes_table

    # New rows to insert
    # Note: MySQLdb doesn't support inserting table names as parameters
    #   due to sql injection
    q = """SELECT chosen_table.sha, uf.fixedby_upstream_sha
            FROM {chosen_table} AS chosen_table
            JOIN upstream_fixes AS uf
            ON chosen_table.upstream_sha = uf.upstream_sha
            WHERE branch = %s
            AND (chosen_table.sha, uf.fixedby_upstream_sha)
            NOT IN (
                SELECT chosen_fixes.kernel_sha, chosen_fixes.fixedby_upstream_sha
                FROM {chosen_fixes} AS chosen_fixes
                WHERE branch = %s
            )""".format(chosen_table=chosen_table, chosen_fixes=chosen_fixes)
    try:
        c.execute(q, [branch, branch])
        logging.info('Finding new rows to insert into fixes table %s %s %s',
                     chosen_table, chosen_fixes, branch)
    except MySQLdb.Error as e: # pylint: disable=no-member
        logging.error('Error finding new rows to insert %s %s %s: error %d(%s)',
                      chosen_table, chosen_fixes, branch, e.args[0], e.args[1])

    count_new_changes = 0
    # todo(hirthanan): Create an intermediate state in Status that allows us to
    #   create all the patches in chrome/stable fixes tables but does not add reviewers
    #   until quota is available. This should decouple the creation of gerrit CL's
    #   and adding reviewers to those CL's.
    for (kernel_sha, fixedby_upstream_sha) in c.fetchall():
        new_change = insert_fix_gerrit(db, chosen_table, chosen_fixes,
                                        branch, kernel_sha, fixedby_upstream_sha)
        if new_change:
            count_new_changes += 1
        if count_new_changes >= limit:
            break

    db.commit()
    return count_new_changes


def missing_patches_sync(db, kernel_metadata, sync_branch_method, limit=None):
    """Helper to create or update fix patches in stable and chromeos releases."""
    if len(sys.argv) > 1:
        branches = sys.argv[1:]
    else:
        branches = common.CHROMEOS_BRANCHES

    os.chdir(common.get_kernel_absolute_path(kernel_metadata.path))

    for b in branches:
        sync_branch_method(db, b, kernel_metadata, limit)

    os.chdir(common.WORKDIR)


def new_missing_patches():
    """Rate limit calling create_new_fixes_in_branch."""
    cloudsql_db = MySQLdb.Connect(user='linux_patches_robot', host='127.0.0.1', db='linuxdb')
    kernel_metadata = common.get_kernel_metadata(common.Kernel.linux_stable)
    missing_patches_sync(cloudsql_db, kernel_metadata, create_new_fixes_in_branch,
                         NEW_CL_DAILY_LIMIT_PER_STABLE_BRANCH)

    kernel_metadata = common.get_kernel_metadata(common.Kernel.linux_chrome)
    missing_patches_sync(cloudsql_db, kernel_metadata, create_new_fixes_in_branch,
                         NEW_CL_DAILY_LIMIT_PER_BRANCH)
    cloudsql_db.close()


def update_missing_patches():
    """Updates fixes table entries on regular basis."""
    cloudsql_db = MySQLdb.Connect(user='linux_patches_robot', host='127.0.0.1', db='linuxdb')

    kernel_metadata = common.get_kernel_metadata(common.Kernel.linux_stable)
    missing_patches_sync(cloudsql_db, kernel_metadata, update_fixes_in_branch)

    kernel_metadata = common.get_kernel_metadata(common.Kernel.linux_chrome)
    missing_patches_sync(cloudsql_db, kernel_metadata, update_fixes_in_branch)

    cloudsql_db.close()