terraform_case.py

#!/usr/bin/python3

"""
A tool to convert camelcase field names in JSON to snake case. Helps with converting
AWS dumps to terraform HCL. For example:

```
$ aws cloudfront get-distribution --id <id> --query Distribution > dist.json
$ python3 terraform_case.py dist.json dist.tf
```
"""
import argparse
import re
import json


def camel2snake(name):
    s1 = re.sub('(.)([A-Z][a-z]+)', r'\1_\2', name)
    return re.sub('([a-z0-9])([A-Z])', r'\1_\2', s1).lower()


def convert_obj(obj):
    out = {}
    if isinstance(obj, str):
        return obj

    for k, v in obj.items():
        if isinstance(v, dict):
            out[camel2snake(k)] = convert_obj(v)
        elif isinstance(v, list):
            out[camel2snake(k)] = [
                convert_obj(i) for i in v
            ]
        else:
            out[camel2snake(k)] = v
    return out


def main():

    parser = argparse.ArgumentParser()
    parser.add_argument('file', type=argparse.FileType('r'))
    parser.add_argument('dest', type=argparse.FileType('w'))
    args = parser.parse_args()

    with args.file as fh:
        args.dest.write(
            json.dumps(
                convert_obj(
                    json.load(fh)
                )
            )
        )


main()