import hashlib
import urllib3

import os


class Hashi:

    url_headers = {"user-agent": "hashi (a file hash checker)/0.1"}
    hash_algorithm = hashlib.sha256()
    encoded = "utf-8"

    def __init__(self):
        """Initialise libraries."""
        self.http = urllib3.PoolManager(headers=self.url_headers)
        urllib3.disable_warnings()
        self.hash_update = self.hash_algorithm.update
        self.hash_hex = self.hash_algorithm.hexdigest

    def fetch_url(self, url, path):
        """Fetch a remote text url and save the contents as an UTF-8 file."""
        resp = self.http.request("GET", url)
        os.makedirs(path.rsplit("/", 1)[0], exist_ok=True)
        with open(path, "w", encoding=self.encoded) as fh:
            fh.write(resp.data.decode(self.encoded))

    def get_hash(self, file_path):
        """Given a text file path, get the hash of the file contents."""
        with open(file_path, "r") as fh:
            bf = fh.read()
        self.hash_update(bf.encode(self.encoded))
        return self.hash_hex()

    def check_hash(self, file_path, hash_path):
        """Compare a file hash with another previously saved hash. Return a
        dictionary with a boolean indicating whether the file hash has changed,
        the old and new hashes."""
        has_change = {"changed": False, "old": "", "new": ""}
        cached_hash = ""
        new_hash = self.get_hash(file_path)
        try:
            with open(hash_path, "r") as fh:
                cached_hash = fh.read()
        except FileNotFoundError:
            # Treat as changed (a call to update)
            has_change = {"changed": True, "old": "", "new": new_hash}
        if new_hash != cached_hash:
            has_change = {"changed": True, "old": cached_hash, "new": new_hash}
        return has_change