import os, re
from typing import List

from million.model.fb_export import FacebookExport


def is_file_valid(file_name: str) -> bool:
    """ 
    Check if this file can be parsed into a FacebookExport
    (Actually only check if its a json file atm)
    """
    # NOTE is there a way to peek inside a json file to
    # check its internal structure ?
    return os.path.splitext(file_name)[-1].lower() == '.json'

def valid_dirfiles(file_dir: str) -> List[str]:
    """ 
    Returns a list of parsable files contained
    in this directory
    """
    return [os.path.join(file_dir, file_name)
            for file_name in os.listdir(file_dir)
            if is_file_valid(file_name)]

def parse_file(file_name: str) -> FacebookExport:
    """ 
    Parses a single parsable file into a FacebookExport Object
    """
    if not is_file_valid(file_name): return None

    with open(file_name, 'rb') as f:
        json_data = __read_broken_fb_json(f.read())
        return FacebookExport.model_validate_json(json_data)

def parse_dirfiles(file_dir: str) -> FacebookExport:
    """ 
    Parses every parsable files inside this directory
    into a single FacebookExport Object
    """
    exports = [parse_file(f) for f in valid_dirfiles(file_dir)]
    
    result = exports[0]

    for ex in exports[1:]: 
        result.merge(ex)

    result.sort()
    return result

def __read_broken_fb_json(binary_data):
    # https://stackoverflow.com/questions/50008296/facebook-json-badly-encoded
    repaired = re.sub(
        rb'\\u00([\da-f]{2})',
        lambda m: bytes.fromhex(m.group(1).decode()),
        binary_data
    )

    return repaired.decode('utf8')