import functools
import os
import re

from jinja2 import Environment, FileSystemLoader


def facts_prod_mapping(db_schema='facts.prod'):
    """
    Converts ref to dbt-models to actual tables/views in the schema.
    Example: 'base_dim_sometheing' => 'facts.prod.dim_something'

    :param db_schema: snowflake database and schema, '.' separated
    :return: callable which can be used as ref_function in jinja_environment
    """
    return functools.partial(re.sub, 'base_(.+)', f'{db_schema}.\\1')


def jinja_environment(templates_path='.', ref_function=facts_prod_mapping()):
    """
    Builds jinja2 environment which can be used to expand dbt templates with macros.

    :param templates_path: path to your template files
    :param ref_function: callable which will be used for resolving {{ ref('table') }}
    :return: jinja2 Environment
    """
    my_dir = os.path.dirname(os.path.realpath(__file__))
    macros_dir = os.path.join(os.path.dirname(my_dir), 'macros')
    env = Environment(
        loader=FileSystemLoader([templates_path, macros_dir]),
    )
    env.globals.update(ref=ref_function)
    return env