import json, os, sys, time, urllib.parse, urllib.request, urllib.error

import jwt

import base64

TOKEN_URL = "https://oauth2.googleapis.com/token"


def _cfg():
    return json.loads(os.environ.get("INTEGRATION_SECRETS", "{}"))


def _token(scopes, subject=None):
    cfg = _cfg()
    raw = cfg.get("service_account_json", "")
    sa = json.loads(raw) if isinstance(raw, str) else raw
    if not sa.get("client_email") or not sa.get("private_key"):
        raise Exception("service_account_json must contain client_email and private_key")
    now = int(time.time())
    aud = sa.get("token_uri") or TOKEN_URL
    payload = {
        "iss": sa["client_email"],
        "scope": " ".join(scopes),
        "aud": aud,
        "iat": now,
        "exp": now + 3600,
    }
    sub = subject or cfg.get("user_id") or ""
    if sub:
        payload["sub"] = sub
    assertion = jwt.encode(payload, sa["private_key"], algorithm="RS256")
    data = urllib.parse.urlencode({
        "grant_type": "urn:ietf:params:oauth:grant-type:jwt-bearer",
        "assertion": assertion,
    }).encode("utf-8")
    req = urllib.request.Request(aud, data=data,
                                 headers={"Content-Type": "application/x-www-form-urlencoded"}, method="POST")
    with urllib.request.urlopen(req, timeout=60) as r:
        tok = json.loads(r.read())
    if not tok.get("access_token"):
        raise Exception("Token request failed: " + json.dumps(tok))
    return tok["access_token"]


def request(method, url, scopes, params=None, body=None, subject=None):
    q = {k: str(x) for k, x in (params or {}).items() if x not in (None, "")}
    if q:
        url += ("&" if "?" in url else "?") + urllib.parse.urlencode(q)
    data = json.dumps(body).encode("utf-8") if body is not None else None
    headers = {"Accept": "application/json", "Authorization": "Bearer " + _token(scopes, subject)}
    if data is not None:
        headers["Content-Type"] = "application/json"
    req = urllib.request.Request(url, data=data, headers=headers, method=method)
    with urllib.request.urlopen(req, timeout=90) as r:
        raw = r.read()
        return json.loads(raw) if raw else {}


SCOPES = ["https://www.googleapis.com/auth/drive"]
BASE = "https://www.googleapis.com/drive/v3"


def main():
    inputs = json.loads(os.environ.get("INTEGRATION_INPUTS", "{}"))
    file_id = inputs.get("file_id")
    if not file_id:
        raise Exception("file_id is required")
    subject = inputs.get("user_id")

    meta = request(
        "GET",
        BASE + "/files/" + urllib.parse.quote(file_id, safe=""),
        SCOPES,
        params={"fields": "id,name,mimeType,size", "supportsAllDrives": "true"},
        subject=subject,
    )

    url = (BASE + "/files/" + urllib.parse.quote(file_id, safe="")
           + "?alt=media&supportsAllDrives=true")
    headers = {"Authorization": "Bearer " + _token(SCOPES, subject)}
    req = urllib.request.Request(url, headers=headers, method="GET")
    with urllib.request.urlopen(req, timeout=300) as r:
        content = r.read()

    print(json.dumps({
        "id": meta.get("id"),
        "file_name": meta.get("name"),
        "mime_type": meta.get("mimeType"),
        "size": len(content),
        "content_base64": base64.b64encode(content).decode("ascii"),
    }))


try:
    main()
except urllib.error.HTTPError as e:
    print(json.dumps({"error": "HTTP " + str(e.code), "detail": e.read().decode("utf-8", "replace")}))
    sys.exit(1)
except Exception as e:
    print(json.dumps({"error": str(e)}))
    sys.exit(1)