#!/usr/bin/env python

__metaclass__ = type

import os
import traceback
import random, string
from ansible.module_utils.basic import AnsibleModule, missing_required_lib

from dataclasses import asdict

LIB_IMPORT_ERR = None
try:
    from signedjson.key import *
    HAS_LIB = True
except:
    HAS_LIB = False
    LIB_IMPORT_ERR = traceback.format_exc()

DOCUMENTION = r"""
---
module: synapse_signing_key
author:
    - transcaffeine (transcaffeine@finally.coffee)
requirements:
    - python >= 3.9
    - signed_json >= 1.1.4
short_description: Generate and persist a synapse signing key
description:
    - "Allows to generate, save and manipulate synapse signing keys"
options:
    path:
        description: "Where the signing key is saved or read from"
        type: str
        required: false
    state:
        description: "State of the key to enforce, can be used to remove keys or generate them"
        type: str
        choices: [present, absent]
        default: present
        required: false
"""

EXAMPLES = r"""
- name: Read existing signing key from filesystem
  finallycoffee.matrix.synapse_signing_key:
    path: "/path/to/existing-synapse.signing.key"
- name: Delete existing signing key
  finallycoffee.matrix.synapse.signing_key:
    path: "/this/signing/key/will/be/deleted.signing.key"
    state: absent
"""

RETURN = r"""
signing_key:
  description: Complete synapse signing key
  returned: always
  type: str
"""

def main() -> None:
    _ = dict
    module = AnsibleModule(
        argument_spec=_(
            path=_(required=False, type="str"),
            state=_(
                required=False,
                type="str",
                default="present",
                choices=["present", "absent"],
            ),
        ),
        supports_check_mode=True,
    )

    result = _(changed=False, diff={}, msg="")
    failed = False

    if not HAS_LIB:
        module.fail_json(msg=missing_required_lib("signed_json"), exception=LIB_IMPORT_ERR)

    path = module.params['path']
    state = module.params['state']
    existing_key_found = False
    if path:
        try:
            keys = _read_signing_keys(module.params['path'])
            existing_key_found = True
        except FileNotFoundError:
            existing_key_found = False
    if not existing_key_found:
        keys = _generate_signing_key()
        result['changed'] = True

    if not module.check_mode:
        if state == 'present' and not existing_key_found and path:
            _write_signing_keys(path, keys)
        if state == 'absent' and existing_key_found:
            os.remove(path)
            result['changed'] = True

    result['diff'] = {
        "before_header": path,
        "after_header": path,
        "before": _render_signing_keys(keys) if existing_key_found else "",
        "after": "" if state == 'absent' else _render_signing_keys(keys),
    }
    result['signing_key'] = _render_signing_keys(keys)

    if failed:
        module.fail_json(**result)
    else:
        module.exit_json(**result)
    
def _render_signing_keys(keys) -> str:
    return "\n".join(_render_signing_key(k) for k in keys)

def _render_signing_key(key) -> str:
    key_b64 = encode_signing_key_base64(key)
    return f"{key.alg} {key.version} {key_b64}"

def _read_signing_keys(file):
    with open(file, "r", opener=lambda path, f: os.open(path, f)) as stream:
        return read_signing_keys(stream)

def _write_signing_keys(file, keys) -> None:
    with open(file, "w", opener=lambda path, f: os.open(path, f, mode=0o640)) as stream:
        write_signing_keys(stream, keys)

def _generate_signing_key():
    id = ''
    for i in range(0, 4):
        id += random.choice(string.ascii_letters)
    key_id = "a_" + id
    key = generate_signing_key(key_id)
    return [key]

if __name__ == "__main__":
    main()