#!/usr/bin/python3
# -*- coding: utf-8 -*-

# Copyright: (c) 2020, Daniel Anglin <d.n.i.anglin@gmail.com>
# The MIT License (see LICENSE or https://mit-license.org)

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

DOCUMENTATION = '''
---
module: compare_semantic_versions

short_description: Compares two semantic version values.

description:
- This module compares two semantic versions and outputs whether the change is an upgrade, a downgrade or no change.
- The values must use valid semantic versioning in order for a successful comparison.

version_added: "2.9.5"

author: Daniel Anglin (@dananglin)

options:
  new_version:
    description:
    - The semantic version of the new software.
    required: true
    type: string
  old_version:
    description:
    - The semantic version of the old software.
    required: true
    type: string
'''

EXAMPLES = '''
- name: Simple comparison between two semantic versions.
  compare_semantic_versions:
    old_version: "1.7.10"
    new_version: "1.8.0"
  register: output1

- debug:
    msg: "{{ output1.result }}"

- name: Semantic versions with the 'v' prefix are supported.
  compare_semantic_versions:
    old_version: "1.6.7"
    new_version: "v3.5.9"
  register: output2

- debug:
    msg: "{{ output2.result }}"

- name: Semantic versions without minor and/or patch versions are supported.
  compare_semantic_versions:
    old_version: "v1.100.3"
    new_version: "v2"
  register: output3

- debug:
    msg: "{{ output3.result }}"
'''

RETURN = '''
result:
  description:
  - The result of the comparison between the two semantic versions.
  - The value "upgrade" is returned if the new version is higher than the old version.
  - The value "downgrade" is returned if the new version is lower than the old version.
  - The value "noVersionChange" is returned if the new version equals the old version.
  returned: On success
  type: string
  sample: upgrade
'''

from ansible.module_utils.basic import AnsibleModule

UPGRADE = "upgrade"
DOWNGRADE = "downgrade"
NO_VERSION_CHANGE = "noVersionChange"
MAJOR = "major"
MINOR = "minor"
PATCH = "patch"
MAX_VERSION_COMPONENTS = 3

def process(semVer):
    if semVer.startswith('v'):
        semVer = semVer[1:]

    semVerArr = semVer.split(".")

    if len(semVerArr) > MAX_VERSION_COMPONENTS:
        raise ValueError("invalid number of version components in semantic version '{}'.".format(semVer))

    if len(semVerArr) < MAX_VERSION_COMPONENTS:
        diff = MAX_VERSION_COMPONENTS - len(semVerArr)
        for i in range(diff):
            semVerArr.append('0')

    try:
        semVerMap = {
                MAJOR: int(semVerArr[0]),
                MINOR: int(semVerArr[1]),
                PATCH: int(semVerArr[2])
        }
    except ValueError as e:
        raise ValueError("unable to parse an int for semantic version '{}' due to invalid format. ({})".format(semVer, str(e)))

    return semVerMap

def compare_versions(old, new):
    try:
        oldSemVerMap = process(old)
        newSemVerMap = process(new)
    except:
        raise

    versions = [MAJOR, MINOR, PATCH]

    for v in range(len(versions)):
        if newSemVerMap[versions[v]] > oldSemVerMap[versions[v]]:
            return UPGRADE
        elif newSemVerMap[versions[v]] < oldSemVerMap[versions[v]]:
            return DOWNGRADE

    return NO_VERSION_CHANGE

def run_module():
    module_args = dict(
        new_version = dict(type='str', required=True),
        old_version = dict(type='str', required=True)
    )

    module = AnsibleModule(
        argument_spec=module_args,
        supports_check_mode=True
    )

    output = dict(
        changed=False,
        result=''
    )

    try:
        result = compare_versions(module.params['old_version'], module.params['new_version'])
    except ValueError as e:
        module.fail_json(msg="Unable to compare semantic versions: {}".format(str(e)), **output)

    output['result'] = result

    module.exit_json(**output)

def main():
    run_module()

if __name__ == '__main__':
    main()