import { logger } from '@rareindex/shared';

export interface Mail {
  to: string | string[];
  subject: string;
  html: string;
  text: string;
  replyTo?: string;
  tags?: Array<{ name: string; value: string }>;
  /** idempotency key to avoid double-sends on retries */
  idempotencyKey?: string;
}

export interface SendResult {
  ok: boolean;
  id: string | null;
  transport: 'resend' | 'console' | 'noop';
  error: string | null;
}

/**
 * Transactional e-mail transport. `EMAIL_TRANSPORT=console` logs mails instead of sending (used in
 * development and tests); `resend` (default when RESEND_API_KEY is set) posts to the Resend API.
 * The API key is read server-side only and never logged.
 */
export function resolveTransport(): 'resend' | 'console' | 'noop' {
  const forced = process.env.EMAIL_TRANSPORT;
  if (forced === 'console' || forced === 'noop' || forced === 'resend') return forced;
  return process.env.RESEND_API_KEY ? 'resend' : 'console';
}

export async function sendMail(mail: Mail): Promise<SendResult> {
  const transport = resolveTransport();
  const from = process.env.EMAIL_FROM ?? 'RareIndex <no-reply@rareindex.io>';
  const to = Array.isArray(mail.to) ? mail.to : [mail.to];
  if (transport === 'console') {
    // eslint-disable-next-line no-console
    console.log(`\n──── MAIL (console transport) ────\nTo: ${to.join(', ')}\nSubject: ${mail.subject}\n\n${mail.text}\n──────────────────────────────────\n`);
    return { ok: true, id: `console_${Date.now()}`, transport, error: null };
  }
  if (transport === 'noop') return { ok: true, id: null, transport, error: null };
  const key = process.env.RESEND_API_KEY;
  if (!key) return { ok: false, id: null, transport, error: 'RESEND_API_KEY missing' };
  try {
    const res = await fetch('https://api.resend.com/emails', {
      method: 'POST',
      headers: {
        authorization: `Bearer ${key}`,
        'content-type': 'application/json',
        ...(mail.idempotencyKey ? { 'idempotency-key': mail.idempotencyKey } : {}),
      },
      body: JSON.stringify({ from, to, subject: mail.subject, html: mail.html, text: mail.text, reply_to: mail.replyTo, tags: mail.tags }),
    });
    const body = (await res.json().catch(() => ({}))) as { id?: string; message?: string; name?: string };
    if (!res.ok) {
      logger.error({ status: res.status, err: body.message ?? body.name }, 'resend send failed');
      return { ok: false, id: null, transport, error: body.message ?? `HTTP ${res.status}` };
    }
    return { ok: true, id: body.id ?? null, transport, error: null };
  } catch (err) {
    const msg = err instanceof Error ? err.message : String(err);
    logger.error({ err: msg }, 'resend send threw');
    return { ok: false, id: null, transport, error: msg };
  }
}