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

BASE = "https://slack.com/api"


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


def _inputs():
    return json.loads(os.environ.get("INTEGRATION_INPUTS", "{}"))


def call(method_name, cfg, body=None, params=None, http="POST"):
    url = BASE + "/" + method_name
    if params:
        url += "?" + urllib.parse.urlencode({k: v for k, v in params.items() if v not in (None, "")})
    data = json.dumps(body).encode("utf-8") if body is not None else None
    headers = {"Authorization": "Bearer " + str(cfg.get("bot_token", "")), "Accept": "application/json"}
    if data is not None:
        headers["Content-Type"] = "application/json; charset=utf-8"
    req = urllib.request.Request(url, data=data, headers=headers, method=http)
    with urllib.request.urlopen(req, timeout=60) as r:
        resp = json.loads(r.read() or "{}")
    if not resp.get("ok"):
        raise Exception("Slack error: " + str(resp.get("error") or resp))
    return resp


def _run(fn):
    try:
        print(json.dumps(fn(_cfg(), _inputs())))
    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)


def main(cfg, inputs):
    channel = str(inputs.get("channel") or "").strip()
    if not channel:
        raise Exception("channel is required")

    text = str(inputs.get("text") or "").strip()
    blocks_raw = str(inputs.get("blocks") or "").strip()
    thread_ts = str(inputs.get("thread_ts") or "").strip()

    if not text and not blocks_raw:
        raise Exception("text or blocks is required")

    body = {"channel": channel}
    if text:
        body["text"] = text
    if blocks_raw:
        try:
            body["blocks"] = json.loads(blocks_raw)
        except Exception:
            raise Exception("blocks must be a valid JSON array")
    if thread_ts:
        body["thread_ts"] = thread_ts

    return call("chat.postMessage", cfg, body=body)


_run(main)