#!/usr/bin/env python3
import importlib
import json
import os
import os.path
import sys

import jinja2
import yaml

NGX_JINJA_MODULES = sorted(set(os.getenv('NGX_JINJA_MODULES', 'os os.path sys netaddr psutil re wcmatch').split(sep=' ')))

ME = sys.argv[0]

NGX_JINJA_SUFFIX = os.getenv('NGX_JINJA_SUFFIX', '.j2')
if NGX_JINJA_SUFFIX == '':
    raise ValueError('NGX_JINJA_SUFFIX is empty')
if not NGX_JINJA_SUFFIX.startswith('.'):
    raise ValueError('NGX_JINJA_SUFFIX does not start with dot (".")')

NGX_JINJA_CONFIG = os.getenv('NGX_JINJA_CONFIG', '')
if (NGX_JINJA_CONFIG != '') and (not os.path.exists(NGX_JINJA_CONFIG)):
    print(f'{ME}: config does not exist, skipping: {NGX_JINJA_CONFIG}', file=sys.stderr)

NGX_JINJA_CONFIG_NAMES = [
    '/angie/jinja',
    '/etc/angie/jinja',
]

if len(sys.argv) < 2:
    raise ValueError('not enough arguments (needed: 2)')
if len(sys.argv) > 3:
    raise ValueError('too many arguments (needed: 2)')

if not sys.argv[1]:
    raise ValueError('specify input file')
input_file = sys.argv[1]
if not os.path.exists(input_file):
    raise ValueError('input file does not exist')

if len(sys.argv) == 3:
    if not sys.argv[2]:
        raise ValueError('specify output file')
    output_file = sys.argv[2]
else:
    output_file, ext = os.path.splitext(input_file)
    if ext != NGX_JINJA_SUFFIX:
        raise ValueError(f'input file name extension mismatch (not a "{NGX_JINJA_SUFFIX}")')

if input_file == output_file:
    raise ValueError('unable to process template inplace')

kwargs = {}
for m in NGX_JINJA_MODULES:
    kwargs[m] = importlib.import_module(m)
kwargs['env'] = os.environ
kwargs['cfg'] = {}


def merge_dict_from_file(filename):
    if not filename:
        return False
    if not isinstance(filename, str):
        return False
    if filename == '':
        return False
    if not os.path.exists(filename):
        return False
    if not os.path.isfile(filename):
        print(f'{ME}: not a file, skipping: {filename}', file=sys.stderr)
        return False
    if filename.endswith('.yml') or filename.endswith('.yaml'):
        with open(filename, mode='r', encoding='utf-8') as fx:
            x = yaml.safe_load(fx)
            kwargs['cfg'] = kwargs['cfg'] | x
        return True
    if filename.endswith('.json'):
        with open(filename, mode='r', encoding='utf-8') as fx:
            x = json.load(fx)
            kwargs['cfg'] = kwargs['cfg'] | x
        return True
    print(f'{ME}: non-recognized name extension: {filename}', file=sys.stderr)
    return False


for base_name in NGX_JINJA_CONFIG_NAMES:
    for file_name in [ base_name + '.' + ext for ext in [ 'yml', 'yaml', 'json' ] ]:
        if merge_dict_from_file(file_name):
            break
        continue
merge_dict_from_file(NGX_JINJA_CONFIG)

with open(input_file, mode='r', encoding='utf-8') as fin:
    template = jinja2.Template(fin.read())
rendered = template.render(**kwargs)

with open(output_file, mode='w', encoding='utf-8') as fout:
    fout.write(rendered)