#!/usr/bin/env python3
"""Fetch messages from a Zulip web-public channel via spectator access.

Given a standard Zulip narrow URL, fetches messages using the
unauthenticated spectator API endpoint. Only works for web-public channels.

Usage:
    fetch-zulip-web-public-messages URL
    fetch-zulip-web-public-messages --num-before 200 --num-after 50 URL
    fetch-zulip-web-public-messages --json URL
"""

import argparse
import re
import sys
import urllib.parse
from datetime import datetime, timezone
from typing import Any

import orjson
import requests


def decode_zulip_hash_component(encoded: str) -> str:
    """Decode a Zulip URL hash component.

    Mirrors web/src/internal_url.ts:decodeHashComponent:
    replace all '.' with '%', then percent-decode.
    """
    return urllib.parse.unquote(encoded.replace(".", "%"), encoding="utf-8")


def parse_zulip_url(url: str) -> tuple[str, int, str, str | None]:
    """Parse a Zulip narrow URL into its components.

    Returns (server_url, channel_id, topic, anchor_message_id).
    anchor_message_id is None if not present in the URL.
    """
    parsed = urllib.parse.urlsplit(url)
    server_url = f"{parsed.scheme}://{parsed.netloc}"
    fragment = parsed.fragment

    # Parse the narrow fragment: narrow/channel/ID-slug/topic/encoded-topic[/with|near/ID]
    match = re.match(
        r"^narrow/(?:channel|stream)/(\d+)-([^/]*)/topic/([^/]+)(?:/(?:with|near)/(\d+))?$",
        fragment,
    )
    if not match:
        print(f"Error: Could not parse Zulip narrow URL: {url}", file=sys.stderr)
        print(
            "Expected format: https://HOSTNAME/#narrow/channel/ID-name/topic/TOPIC[/with|near/MSG_ID]",
            file=sys.stderr,
        )
        sys.exit(1)

    channel_id = int(match.group(1))
    topic = decode_zulip_hash_component(match.group(3))
    anchor: str | None = match.group(4)

    return server_url, channel_id, topic, anchor


def fetch_messages(
    server_url: str,
    channel_id: int,
    topic: str,
    anchor: str | None,
    num_before: int,
    num_after: int,
) -> dict[str, Any]:
    """Fetch messages from the Zulip spectator API."""
    narrow = [
        {"operator": "channels", "operand": "web-public"},
        {"operator": "channel", "operand": channel_id},
        {"operator": "topic", "operand": topic},
    ]
    params = {
        "anchor": anchor if anchor is not None else "newest",
        "num_before": str(num_before),
        "num_after": str(num_after),
        "narrow": orjson.dumps(narrow).decode(),
    }

    response = requests.get(
        f"{server_url}/json/messages",
        params=params,
        timeout=30,
    )

    if response.status_code != 200:
        print(f"Error: API returned status {response.status_code}", file=sys.stderr)
        try:
            error_data = orjson.loads(response.content)
            print(f"  {error_data.get('msg', response.text)}", file=sys.stderr)
        except orjson.JSONDecodeError:
            print(f"  {response.text}", file=sys.stderr)
        sys.exit(1)

    return orjson.loads(response.content)


def format_messages(data: dict[str, Any]) -> str:
    """Format API response messages for human-readable output."""
    messages = data.get("messages", [])
    if not messages:
        return "No messages found."

    blocks = []
    for msg in messages:
        timestamp = datetime.fromtimestamp(msg["timestamp"], tz=timezone.utc).strftime(
            "%Y-%m-%d %H:%M UTC"
        )
        header = f"--- {msg['sender_full_name']} ({timestamp}) [{msg['id']}] ---"
        blocks.append(f"{header}\n{msg['content']}")

    return "\n\n".join(blocks) + "\n"


def main() -> None:
    parser = argparse.ArgumentParser(
        description="Fetch messages from a Zulip web-public channel via spectator access."
    )
    parser.add_argument("url", help="Zulip narrow URL to fetch messages from")
    parser.add_argument(
        "--num-before",
        type=int,
        default=100,
        help="Number of messages before the anchor (default: 100)",
    )
    parser.add_argument(
        "--num-after",
        type=int,
        default=100,
        help="Number of messages after the anchor (default: 100)",
    )
    parser.add_argument(
        "--json",
        action="store_true",
        help="Output raw JSON response",
    )
    args = parser.parse_args()

    server_url, channel_id, topic, anchor = parse_zulip_url(args.url)
    data = fetch_messages(server_url, channel_id, topic, anchor, args.num_before, args.num_after)

    if args.json:
        sys.stdout.buffer.write(orjson.dumps(data, option=orjson.OPT_INDENT_2) + b"\n")
    else:
        print(format_messages(data), end="")


if __name__ == "__main__":
    main()