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/gmail.readonly"]


def flatten_message(msg):
    payload = msg.get("payload", {})
    headers = {h.get("name", "").lower(): h.get("value", "") for h in payload.get("headers", [])}
    acc = {"body_text": "", "body_html": "", "attachments": []}

    def walk(part):
        for sub in part.get("parts", []) or []:
            walk(sub)
        mime = part.get("mimeType", "")
        data = part.get("body", {}).get("data")
        if part.get("filename"):
            acc["attachments"].append({
                "id": part.get("body", {}).get("attachmentId", ""),
                "name": part.get("filename", ""),
                "mime_type": mime,
            })
        elif data:
            text = base64.urlsafe_b64decode(data.encode("ascii")).decode("utf-8", "replace")
            if mime == "text/html":
                acc["body_html"] += text
            else:
                acc["body_text"] += text

    walk(payload)
    return {
        "id": msg.get("id"),
        "thread_id": msg.get("threadId"),
        "labels": msg.get("labelIds", []),
        "snippet": msg.get("snippet", ""),
        "internal_date": msg.get("internalDate"),
        "subject": headers.get("subject", ""),
        "from": headers.get("from", ""),
        "to": headers.get("to", ""),
        "cc": headers.get("cc", ""),
        "date": headers.get("date", ""),
        "message_id_header": headers.get("message-id", ""),
        "body_text": acc["body_text"],
        "body_html": acc["body_html"],
        "attachments": acc["attachments"],
    }


def main():
    inputs = json.loads(os.environ.get("INTEGRATION_INPUTS", "{}"))
    mailbox = str(inputs.get("user_id") or _cfg().get("user_id") or "me")
    base = "https://gmail.googleapis.com/gmail/v1/users/" + urllib.parse.quote(mailbox, safe="")

    thread_id = str(inputs.get("thread_id") or "").strip()
    if not thread_id:
        raise Exception("thread_id is required")

    thread = request("GET", base + "/threads/" + urllib.parse.quote(thread_id, safe=""),
                     SCOPES, params={"format": "full"}, subject=mailbox)
    messages = [flatten_message(m) for m in thread.get("messages", []) or []]
    print(json.dumps({"id": thread_id, "messages": messages}))


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)
