#!/usr/bin/python
# -*- coding: utf-8 -*-

# Copyright: (c) 2013, Evan Kaufman <evan@digitalflophouse.com
# Copyright: (c) 2017, Ansible Project
# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)

from __future__ import absolute_import, division, print_function
__metaclass__ = type

ANSIBLE_METADATA = {'metadata_version': '1.1',
                    'status': ['stableinterface'],
                    'supported_by': 'community'}


DOCUMENTATION = r'''
---
module: replace
author: Evan Kaufman (@EvanK)
extends_documentation_fragment:
    - files
    - validate
short_description: Replace all instances of a particular string in a
                   file using a back-referenced regular expression
description:
  - This module will replace all instances of a pattern within a file.
  - It is up to the user to maintain idempotence by ensuring that the
    same pattern would never match any replacements made.
version_added: "1.6"
options:
  path:
    description:
      - The file to modify.
      - Before Ansible 2.3 this option was only usable as I(dest), I(destfile) and I(name).
    type: path
    required: true
    aliases: [ dest, destfile, name ]
  regexp:
    description:
      - The regular expression to look for in the contents of the file.
      - Uses Python regular expressions; see
        U(http://docs.python.org/2/library/re.html).
      - Uses MULTILINE mode, which means C(^) and C($) match the beginning
        and end of the file, as well as the beginning and end respectively
        of I(each line) of the file.
      - Does not use DOTALL, which means the C(.) special character matches
        any character I(except newlines). A common mistake is to assume that
        a negated character set like C([^#]) will also not match newlines.
      - In order to exclude newlines, they must be added to the set like C([^#\n]).
      - Note that, as of Ansible 2.0, short form tasks should have any escape
        sequences backslash-escaped in order to prevent them being parsed
        as string literal escapes. See the examples.
    type: str
    required: true
  replace:
    description:
      - The string to replace regexp matches.
      - May contain backreferences that will get expanded with the regexp capture groups if the regexp matches.
      - If not set, matches are removed entirely.
    type: str
  after:
    description:
      - If specified, the line after the replace/remove will start.
      - Can be used in combination with C(before).
      - Uses Python regular expressions; see
        U(http://docs.python.org/2/library/re.html).
    type: str
    version_added: "2.4"
  before:
    description:
      - If specified, the line before the replace/remove will occur.
      - Can be used in combination with C(after).
      - Uses Python regular expressions; see
        U(http://docs.python.org/2/library/re.html).
    type: str
    version_added: "2.4"
  backup:
    description:
      - Create a backup file including the timestamp information so you can
        get the original file back if you somehow clobbered it incorrectly.
    type: bool
    default: no
  others:
    description:
      - All arguments accepted by the M(file) module also work here.
    type: str
  encoding:
    description:
      - The character encoding for reading and writing the file.
    type: str
    default: utf-8
    version_added: "2.4"
notes:
  - As of Ansible 2.3, the I(dest) option has been changed to I(path) as default, but I(dest) still works as well.
  - Option I(follow) has been removed in Ansible 2.5, because this module modifies the contents of the file so I(follow=no) doesn't make sense.
'''

EXAMPLES = r'''
# Before Ansible 2.3, option 'dest', 'destfile' or 'name' was used instead of 'path'
- replace:
    path: /etc/hosts
    regexp: '(\s+)old\.host\.name(\s+.*)?$'
    replace: '\1new.host.name\2'
    backup: yes

- name: Replace after the expression till the end of the file (requires Ansible >= 2.4)
  replace:
    path: /etc/hosts
    regexp: '(\s+)old\.host\.name(\s+.*)?$'
    replace: '\1new.host.name\2'
    after: Start after line.*
    backup: yes

- name: Replace before the expression till the begin of the file (requires Ansible >= 2.4)
  replace:
    path: /etc/hosts
    regexp: '(\s+)old\.host\.name(\s+.*)?$'
    replace: '\1new.host.name\2'
    before: 'Start before line.*'
    backup: yes

- name: Replace between the expressions (requires Ansible >= 2.4)
  replace:
    path: /etc/hosts
    regexp: '(\s+)old\.host\.name(\s+.*)?$'
    replace: '\1new.host.name\2'
    after: 'Start after line.*'
    before: 'Start before line.*'
    backup: yes

- replace:
    path: /home/jdoe/.ssh/known_hosts
    regexp: '^old\.host\.name[^\n]*\n'
    owner: jdoe
    group: jdoe
    mode: '0644'

- replace:
    path: /etc/apache/ports
    regexp: '^(NameVirtualHost|Listen)\s+80\s*$'
    replace: '\1 127.0.0.1:8080'
    validate: '/usr/sbin/apache2ctl -f %s -t'

- name: Short form task (in ansible 2+) necessitates backslash-escaped sequences
  replace: dest=/etc/hosts regexp='\\b(localhost)(\\d*)\\b' replace='\\1\\2.localdomain\\2 \\1\\2'

- name: Long form task does not
  replace:
    dest: /etc/hosts
    regexp: '\b(localhost)(\d*)\b'
    replace: '\1\2.localdomain\2 \1\2'
'''

import os
import re
import tempfile

from ansible.module_utils._text import to_text, to_bytes
from ansible.module_utils.basic import AnsibleModule


def write_changes(module, contents, path):

    tmpfd, tmpfile = tempfile.mkstemp(dir=module.tmpdir)
    f = os.fdopen(tmpfd, 'wb')
    f.write(contents)
    f.close()

    validate = module.params.get('validate', None)
    valid = not validate
    if validate:
        if "%s" not in validate:
            module.fail_json(msg="validate must contain %%s: %s" % (validate))
        (rc, out, err) = module.run_command(validate % tmpfile)
        valid = rc == 0
        if rc != 0:
            module.fail_json(msg='failed to validate: '
                                 'rc:%s error:%s' % (rc, err))
    if valid:
        module.atomic_move(tmpfile, path, unsafe_writes=module.params['unsafe_writes'])


def check_file_attrs(module, changed, message):

    file_args = module.load_file_common_arguments(module.params)
    if module.set_file_attributes_if_different(file_args, False):

        if changed:
            message += " and "
        changed = True
        message += "ownership, perms or SE linux context changed"

    return message, changed


def main():
    module = AnsibleModule(
        argument_spec=dict(
            path=dict(type='path', required=True, aliases=['dest', 'destfile', 'name']),
            regexp=dict(type='str', required=True),
            replace=dict(type='str', default=''),
            after=dict(type='str'),
            before=dict(type='str'),
            backup=dict(type='bool', default=False),
            validate=dict(type='str'),
            encoding=dict(type='str', default='utf-8'),
        ),
        add_file_common_args=True,
        supports_check_mode=True,
    )

    params = module.params
    path = params['path']
    encoding = params['encoding']
    res_args = dict()

    params['after'] = to_text(params['after'], errors='surrogate_or_strict', nonstring='passthru')
    params['before'] = to_text(params['before'], errors='surrogate_or_strict', nonstring='passthru')
    params['regexp'] = to_text(params['regexp'], errors='surrogate_or_strict', nonstring='passthru')
    params['replace'] = to_text(params['replace'], errors='surrogate_or_strict', nonstring='passthru')

    if os.path.isdir(path):
        module.fail_json(rc=256, msg='Path %s is a directory !' % path)

    if not os.path.exists(path):
        module.fail_json(rc=257, msg='Path %s does not exist !' % path)
    else:
        f = open(path, 'rb')
        contents = to_text(f.read(), errors='surrogate_or_strict', encoding=encoding)
        f.close()

    pattern = u''
    if params['after'] and params['before']:
        pattern = u'%s(?P<subsection>.*?)%s' % (params['before'], params['after'])
    elif params['after']:
        pattern = u'%s(?P<subsection>.*)' % params['after']
    elif params['before']:
        pattern = u'(?P<subsection>.*)%s' % params['before']

    if pattern:
        section_re = re.compile(pattern, re.DOTALL)
        match = re.search(section_re, contents)
        if match:
            section = match.group('subsection')
        else:
            res_args['msg'] = 'Pattern for before/after params did not match the given file: %s' % pattern
            res_args['changed'] = False
            module.exit_json(**res_args)
    else:
        section = contents

    mre = re.compile(params['regexp'], re.MULTILINE)
    result = re.subn(mre, params['replace'], section, 0)

    if result[1] > 0 and section != result[0]:
        if pattern:
            result = (contents.replace(section, result[0]), result[1])
        msg = '%s replacements made' % result[1]
        changed = True
        if module._diff:
            res_args['diff'] = {
                'before_header': path,
                'before': contents,
                'after_header': path,
                'after': result[0],
            }
    else:
        msg = ''
        changed = False

    if changed and not module.check_mode:
        if params['backup'] and os.path.exists(path):
            res_args['backup_file'] = module.backup_local(path)
        # We should always follow symlinks so that we change the real file
        path = os.path.realpath(path)
        write_changes(module, to_bytes(result[0], encoding=encoding), path)

    res_args['msg'], res_args['changed'] = check_file_attrs(module, changed, msg)
    module.exit_json(**res_args)


if __name__ == '__main__':
    main()