import { fetchJson } from "../../http.ts";
import { type OpenMeetEvent } from "../../openmeet/openmeet.ts";
import type { Channel } from "./channel.ts";

const WEEKDAYS = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"] as const;

function formatEventDate(iso: string): string {
  const date = Temporal.Instant.from(iso).toZonedDateTimeISO("UTC").toPlainDate();
  const day = WEEKDAYS[date.dayOfWeek - 1]!;
  const mm = String(date.month).padStart(2, "0");
  const dd = String(date.day).padStart(2, "0");
  return `${day} ${mm}/${dd}`;
}

function formatEvent(e: OpenMeetEvent): string {
  const dateStr = formatEventDate(e.startDate);
  const url = `https://platform.openmeet.net/events/${e.slug}`;
  return `[${e.name}](${url}) (${dateStr})`;
}

export const slackOne = (e: OpenMeetEvent): string =>
  `:sparkles: *New event posted:* ${formatEvent(e)}`;

export const slackMany = (events: OpenMeetEvent[]): string =>
  events.length === 0
    ? ":goose-honk-sob: No events this week."
    : [":goose-honk-right: **Events this week**", ...events.map((e) => `- ${formatEvent(e)}`)].join(
        "\n",
      );

export function slackChannel(
  token: string,
  channel: string,
  apiBase = "https://slack.com/api",
): Channel {
  const post = async (text: string): Promise<void> => {
    const result = await fetchJson<{ ok: boolean; error?: string }>(
      "slack post",
      `${apiBase}/chat.postMessage`,
      {
        method: "POST",
        headers: {
          Authorization: `Bearer ${token}`,
          "Content-Type": "application/json; charset=utf-8",
        },
        body: JSON.stringify({
          channel,
          markdown_text: text,
          unfurl_links: false,
          unfurl_media: false,
        }),
      },
    );
    // Slack returns 200 with {"ok": false, "error": "..."} for API-level
    // failures (bad token, channel not found, etc.).
    if (!result.ok) throw new Error(`slack API error: ${result.error}`);
  };
  return {
    name: "slack",
    notifyOne: (e) => post(slackOne(e)),
    notifyMany: (events) => post(slackMany(events)),
  };
}