import {
  SecretsManagerClient,
  GetSecretValueCommand,
} from "@aws-sdk/client-secrets-manager";

const secrets = new SecretsManagerClient();
const EXPENSE_BOT_TOKEN_SECRET_NAME = process.env.EXPENSE_BOT_TOKEN_SECRET_NAME;

let cachedToken;
async function getBotToken() {
  if (cachedToken) return cachedToken;
  const { SecretString } = await secrets.send(
    new GetSecretValueCommand({ SecretId: EXPENSE_BOT_TOKEN_SECRET_NAME })
  );
  cachedToken = SecretString;
  return cachedToken;
}

const SUBMITTED_CHANNEL = "C0AQ2AWLNEN";

const STAGES = {
  [SUBMITTED_CHANNEL]: { next: "C0APLSGABAB", label: "Processed" },
  C0APLSGABAB: { next: "C0AQ09CDJH4", label: "Authorized" },
  C0AQ09CDJH4: { next: "C0APYUM1JFP", label: "Matched" },
};

const REACT_HINT_RE = /_React_ :white_check_mark: _to advance to \w+_/;

async function slackGet(method, token, params) {
  const qs = new URLSearchParams(params).toString();
  const res = await fetch(`https://slack.com/api/${method}?${qs}`, {
    headers: { Authorization: `Bearer ${token}` },
  });
  const data = await res.json();
  if (!data.ok) throw new Error(`${method} failed: ${data.error}`);
  return data;
}

async function slackPost(method, token, body) {
  const res = await fetch(`https://slack.com/api/${method}`, {
    method: "POST",
    headers: {
      Authorization: `Bearer ${token}`,
      "Content-Type": "application/json; charset=utf-8",
    },
    body: JSON.stringify(body),
  });
  const data = await res.json();
  if (!data.ok) throw new Error(`${method} failed: ${data.error}`);
  return data;
}

export const handler = async (event) => {
  if (event.type !== "reaction_added" || event.reaction !== "white_check_mark") {
    console.log(`Skipping event type=${event.type} reaction=${event.reaction}`);
    return;
  }

  const fromChannel = event.item.channel;
  const messageTs = event.item.ts;

  const route = STAGES[fromChannel];
  if (!route) {
    console.log(`Channel ${fromChannel} not in STAGES, skipping`);
    return;
  }

  const toChannel = route.next;
  const label = route.label;
  const isOrigin = fromChannel === SUBMITTED_CHANNEL;
  const token = await getBotToken();

  const history = await slackGet("conversations.history", token, {
    channel: fromChannel,
    latest: messageTs,
    limit: "1",
    inclusive: "true",
  });
  const originalText = history.messages[0].text;

  const text = originalText.replace(REACT_HINT_RE, "").trim();
  const nextStage = STAGES[toChannel];
  const nextLabel = nextStage ? nextStage.label : null;
  const reactLine = nextLabel
    ? `\n\n_React_ :white_check_mark: _to advance to ${nextLabel}_`
    : "";

  let permalinkLine = "";
  if (isOrigin) {
    const permalinkResp = await slackGet("chat.getPermalink", token, {
      channel: fromChannel,
      message_ts: messageTs,
    });
    permalinkLine = `\n\n:paperclip: *Original Submission:* <${permalinkResp.permalink}|View Original Message>`;
  }
  const fullText = `${text}${permalinkLine}${reactLine}`;

  await slackPost("chat.postMessage", token, {
    channel: toChannel,
    text: fullText,
    mrkdwn: true,
    unfurl_links: false,
    unfurl_media: false,
  });

  if (isOrigin) {
    await slackPost("chat.postMessage", token, {
      channel: fromChannel,
      thread_ts: messageTs,
      text: `➡️ Advanced to ${label}`,
    });
    console.log(`Advanced user submission to ${label} (origin preserved)`);
  } else {
    await slackPost("chat.delete", token, {
      channel: fromChannel,
      ts: messageTs,
    });
    console.log(`Advanced to ${label} and deleted previous copy`);
  }
};