import functools
import hashlib

from ansible.constants import config
from ansible.errors import AnsibleError
from ansible.plugins.loader import cache_loader, lookup_loader
from ansible.plugins.lookup import LookupBase, display

DOCUMENTATION = """
lookup: cache
author: Dustin C. Hatch <dustin@hatch.name>
options:
  cache_plugin:
    description:
    - Cache plugin to use
    type: str
    required: false
    default: memory
    env:
    - name: ANSIBLE_LOOKUP_CACHE_PLUGIN
    ini:
    - section: lookup
      key: cache_plugin
  cache_timeout:
    description:
    - Cache duration in seconds
    default: 3600
    type: int
    env:
    - name: ANSIBLE_LOOKUP_CACHE_TIMEOUT
    ini:
    - section: lookup
      key: cache_timeout
  cache_connection:
    description:
    - Cache connection data or path, read cache plugin documentation for specifics.
    type: str
    env:
    - name: ANSIBLE_LOOKUP_CACHE_CONNECTION
    ini:
    - section: lookup
      key: cache_connection
  cache_prefix:
    description:
    - Prefix to use for cache plugin files/tables
    default: ''
    env:
    - name: ANSIBLE_LOOKUP_CACHE_PREFIX
    ini:
    - section: lookup
      key: cache_prefix
"""


def _get_option(key: str):
    return config.get_config_value(
        key, plugin_type='lookup', plugin_name='cache'
    )


@functools.cache
def _get_cache():
    cache_plugin = _get_option('cache_plugin')
    cache_options = {}
    if cache_connection := _get_option('cache_connection'):
        cache_options['_uri'] = cache_connection
    if cache_timeout := _get_option('cache_timeout'):
        cache_options['_timeout'] = cache_timeout
    if cache_prefix := _get_option('cache_prefix'):
        cache_options['_prefix'] = cache_prefix
    return cache_loader.get(cache_plugin, **cache_options)


class LookupModule(LookupBase):
    def run(self, terms, variables=None, **kwargs):
        cache = _get_cache()
        display.v(f'lookup cache: using cache plugin {cache.plugin_name}')
        h = hashlib.sha1()
        h.update(str((terms, kwargs)).encode('utf-8'))
        key = h.hexdigest()
        try:
            result = cache.get(key)
        except KeyError:
            result = None
        if result is None:
            lookup_name, terms = terms[0], terms[1:]
            lookup = lookup_loader.get(
                lookup_name, loader=self._loader, templar=self._templar
            )
            if lookup is None:
                raise AnsibleError(
                    f'Could not find lookup plugin {lookup_name!r}'
                )
            result = lookup.run(terms, variables=variables, **kwargs)
            cache.set(key, result)
        else:
            str_terms = ', '.join(repr(t) for t in terms)
            str_kwargs = ', '.join(f'{k}={v!r}' for k, v in kwargs.items())
            display.v(
                'lookup cache: found cached value for'
                f' lookup({str_terms}, {str_kwargs})'
            )
        return result