"""Slack integration for daily-scan candidates.

Posts a Block Kit message per candidate paper with Approve/Reject buttons via
an Incoming Webhook, verifies Slack's request signature on the interactivity
callback, and edits the message in place (via the interaction's response_url)
once a decision is made. No bot token needed — posting goes through the
webhook, and updates go through response_url, which Slack hands back on
every interaction regardless of how the original message was posted. Two
callers:

  - daily_scan.py calls post_candidate() after creating a job in the store.
  - app.py's /slack/interactions route calls verify_signature() then
    handle_interaction() when a button is clicked.
"""

from __future__ import annotations

import hashlib
import hmac
import os
import time

import requests

try:
    from dotenv import load_dotenv

    load_dotenv()
except ImportError:
    pass

try:
    # Works when this file lives inside the deployed Space (flat layout,
    # store.py a sibling module).
    import store
except ImportError:
    # Works when imported as repropapers.slack_bot from the outer monorepo
    # (e.g. daily_scan.py at the repo root).
    from repropapers import store

APPROVE_ACTION = "approve_candidate"
REJECT_ACTION = "reject_candidate"

# Slack rejects signatures on requests older than this; we mirror the check.
MAX_REQUEST_AGE_SECONDS = 60 * 5


def _signing_secret() -> str:
    secret = os.environ.get("SLACK_SIGNING_SECRET")
    if not secret:
        raise RuntimeError("SLACK_SIGNING_SECRET is not set.")
    return secret


def _webhook_url() -> str:
    url = os.environ.get("SLACK_WEBHOOK_URL")
    if not url:
        raise RuntimeError("SLACK_WEBHOOK_URL is not set.")
    return url


def verify_signature(timestamp: str, body: str, signature: str) -> bool:
    """Verify Slack's HMAC request signature. See Slack's "Verifying requests" docs."""
    if not timestamp or not signature:
        return False
    try:
        if abs(time.time() - int(timestamp)) > MAX_REQUEST_AGE_SECONDS:
            return False
    except ValueError:
        return False

    basestring = f"v0:{timestamp}:{body}".encode()
    digest = hmac.new(_signing_secret().encode(), basestring, hashlib.sha256).hexdigest()
    expected = f"v0={digest}"
    return hmac.compare_digest(expected, signature)


def _links_line(job: dict) -> str:
    parts = [f"<{job['paper_url']}|paper>", f"<{job['code_url']}|code>"]
    if job.get("data_url"):
        parts.append(f"<{job['data_url']}|data>")
    return " · ".join(parts)


def _candidate_blocks(job: dict, decision: dict | None = None) -> list[dict]:
    blocks = [
        {
            "type": "section",
            "text": {
                "type": "mrkdwn",
                "text": f"🔬 *New reproduction candidate*\n*{job['title']}*",
            },
        },
        {
            "type": "section",
            "text": {"type": "mrkdwn", "text": f"Why: {job.get('repro_summary') or '_no summary_'}"},
        },
        {
            "type": "context",
            "elements": [
                {
                    "type": "mrkdwn",
                    "text": (
                        f"score {job.get('repro_score', '?')}/100 · "
                        f"{job.get('upvotes', 0)} upvotes · {_links_line(job)}"
                    ),
                }
            ],
        },
    ]
    if decision:
        icon = "✅" if decision["status"] == "approved" else "✕"
        blocks.append(
            {
                "type": "context",
                "elements": [
                    {"type": "mrkdwn", "text": f"{icon} *{decision['status'].capitalize()}* by <@{decision['user_id']}>"}
                ],
            }
        )
    else:
        blocks.append(
            {
                "type": "actions",
                "elements": [
                    {
                        "type": "button",
                        "text": {"type": "plain_text", "text": "✓ Approve"},
                        "style": "primary",
                        "action_id": APPROVE_ACTION,
                        "value": job["id"],
                    },
                    {
                        "type": "button",
                        "text": {"type": "plain_text", "text": "✕ Reject"},
                        "style": "danger",
                        "action_id": REJECT_ACTION,
                        "value": job["id"],
                    },
                ],
            }
        )
    return blocks


def post_candidate(job: dict) -> None:
    """Post a candidate to Slack via the Incoming Webhook."""
    resp = requests.post(
        _webhook_url(),
        json={
            "text": f"New reproduction candidate: {job['title']}",  # fallback for notifications
            "blocks": _candidate_blocks(job),
        },
        timeout=15,
    )
    resp.raise_for_status()


def handle_interaction(payload: dict) -> None:
    """Handle a Slack block_actions payload: flip the job's status and edit the message."""
    if payload.get("type") != "block_actions":
        return
    actions = payload.get("actions") or []
    if not actions:
        return

    action = actions[0]
    job_id = action.get("value")
    action_id = action.get("action_id")
    if not job_id or action_id not in (APPROVE_ACTION, REJECT_ACTION):
        return

    job = store.get_job(job_id)
    if job is None:
        return

    status = "approved" if action_id == APPROVE_ACTION else "rejected"
    user_id = (payload.get("user") or {}).get("id", "")
    fields = {"decided_by": user_id}
    if status == "approved":
        from datetime import datetime, timezone

        fields["approved_at"] = datetime.now(timezone.utc).isoformat()
    job = store.set_status(job_id, status, **fields)

    response_url = payload.get("response_url")
    if response_url:
        requests.post(
            response_url,
            json={
                "replace_original": True,
                "text": f"{job['title']} — {status}",
                "blocks": _candidate_blocks(job, decision={"status": status, "user_id": user_id}),
            },
            timeout=15,
        )