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

import jinja2
import yaml


J2_MODULES_DEFAULT = 'os os.path sys netaddr psutil re wcmatch'
J2_SUFFIX_DEFAULT = '.j2'
J2_CFG_PATHS = [
    '/angie/jinja',
    '/etc/angie/jinja',
]
J2_CFG_EXTS = [
    'yml',
    'yaml',
    'json',
]
J2_SEARCH_PATH = [
    '.',
    '/etc/angie',
]
J2_EXT_LIST = [
    'jinja2.ext.do',
    'jinja2.ext.loopcontrols',
]


J2_MODULES = sorted(set(os.getenv('NGX_JINJA_MODULES', J2_MODULES_DEFAULT).split(sep=' ')))

ME = sys.argv[0]

J2_SUFFIX = os.getenv('NGX_JINJA_SUFFIX', J2_SUFFIX_DEFAULT)
if J2_SUFFIX == '':
    raise ValueError('NGX_JINJA_SUFFIX is empty')
if not J2_SUFFIX.startswith('.'):
    raise ValueError('NGX_JINJA_SUFFIX does not start with dot (".")')

J2_CONFIG = os.getenv('NGX_JINJA_CONFIG', '')
if (J2_CONFIG != '') and (not os.path.exists(J2_CONFIG)):
    print(f'{ME}: config does not exist, skipping: {J2_CONFIG}', file=sys.stderr)


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 != J2_SUFFIX:
        raise ValueError(f'input file name extension mismatch (not a "{J2_SUFFIX}")')

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

kwargs = {}
for m in J2_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


if (J2_CONFIG != '') and (os.path.isfile(J2_CONFIG)):
    merge_dict_from_file(J2_CONFIG)
else:
    for base in J2_CFG_PATHS:
        for full in [ base + '.' + ext for ext in J2_CFG_EXTS ]:
            if merge_dict_from_file(full):
                break
            continue


j2_loader = jinja2.FileSystemLoader(J2_SEARCH_PATH, followlinks=True)
j2_environ = jinja2.Environment(loader=j2_loader, extensions=J2_EXT_LIST)
j2_template = j2_environ.get_template(input_file)
j2_stream = j2_template.stream(**kwargs)
j2_stream.disable_buffering()
j2_stream.dump(output_file, encoding='utf-8')