// @ts-check

// いじりやすいようにここに変数を集約させたい
const BLOCKLIST = ["hacker@example.com", "spammer@example.com"];
const FORWARD_TO = "mymail@example.com";
const WEBHOOK_URL = "https://discord.com/api/webhooks/xxx/xxx";
// trendcreate icon
const WEBHOOK_ICON =
  "https://git.v-sli.me/HidemaruOwO/email-worker/raw/branch/main/assets/webhook_icon.jpg";
// mail letter icon
const AUTHOR_ICON =
  "https://git.v-sli.me/HidemaruOwO/email-worker/raw/branch/main/assets/email_icon.png";
// cloudflare icon
const FOOTER_ICON =
  "https://git.v-sli.me/HidemaruOwO/email-worker/raw/branch/main/assets/cloudflare_icon.ico";

export default {
  async email(message, env, ctx) {
    if (BLOCKLIST.includes(message.from)) {
      message.setReject("Address is blocked");
      return;
    }

    try {
      const [result] = await Promise.all([
        notify(message),
        message.forward(FORWARD_TO),
      ]);

      if (!result.ok) {
        console.log(await result.text());
        console.log(await result.json());
        return;
      }
    } catch (err) {
      console.error("処理エラー:", err);
    }
  },
};

// async function notify(from, subject, text, date) {
async function notify(message) {
  const from = message.headers.get("from");
  const subject = message.headers.get("subject");
  const date = message.headers.get("date");
  const text = await getMailText(message);

  const payload = {
    username: "contact@trendcreate.net",
    avatar_url: WEBHOOK_ICON,
    content: `**${from}**からお問い合わせメールが届いております。`,
    embeds: [
      {
        author: { name: from || "名前なし", icon_url: AUTHOR_ICON },
        title: `**${subject || "件名なし"}**`,
        description: text || "本文はありません。",
        timestamp: new Date(date).toISOString(),
        footer: {
          text: "Powered by Cloudflare Worker and Email Routing",
          icon_url: FOOTER_ICON,
        },
      },
    ],
  };

  // console.log(JSON.stringify(payload))

  try {
    const result = await fetch(WEBHOOK_URL, {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify(payload),
    });
    return result;
  } catch (err) {
    console.log(err);
    throw new Error(err);
  }
}

async function getMailText(message) {
  try {
    const buf = await readStream(message.raw);
    if (buf === "NO_CONTENT") {
      return "";
    }
    return parseEmail(buf);
  } catch (err) {
    return `エラー: ${err.message}`;
  }
}

async function readStream(stream) {
  if (typeof stream === "undefined") {
    return "NO_CONTENT";
  }

  const chunks = [];
  const reader = stream.getReader();

  while (true) {
    const { done, value } = await reader.read();
    if (done) break;
    chunks.push(value);
  }

  const size = chunks.reduce((sum, chunk) => sum + chunk.length, 0);
  const result = new Uint8Array(size);

  let pos = 0;
  for (const chunk of chunks) {
    result.set(chunk, pos);
    pos += chunk.length;
  }

  return result;
}

function parseEmail(buffer) {
  const text = new TextDecoder().decode(buffer);
  const headerEnd = text.indexOf("\r\n\r\n");

  if (headerEnd === -1) return "";

  const header = text.substring(0, headerEnd);
  const body = text.substring(headerEnd + 4);

  const boundaryMatch = header.match(/boundary="?([^"\r\n]+)"?/i);

  if (!boundaryMatch) return body.trim();

  const boundary = `--${boundaryMatch[1]}`;
  const parts = body.split(boundary);

  for (const part of parts) {
    if (part.includes("Content-Type: text/plain")) {
      const isBase64 = part.includes("Content-Transfer-Encoding: base64");
      const partBody = part.split("\r\n\r\n")[1]?.trim();

      if (!partBody) continue;

      if (isBase64) {
        try {
          const cleanBase64 = partBody.replace(/[\r\n\s]/g, "");
          return decodeBase64(cleanBase64);
        } catch {
          continue;
        }
      } else {
        return partBody;
      }
    }
  }

  return "";
}

function decodeBase64(base64) {
  const binary = atob(base64);
  const bytes = new Uint8Array(binary.length);

  for (let i = 0; i < binary.length; i++) {
    bytes[i] = binary.charCodeAt(i);
  }

  return new TextDecoder().decode(bytes);
}