import "server-only";
import { Resend } from "resend";
import { APP_URL } from "@/lib/env";
import { log } from "@/lib/log";
import * as T from "./templates";

export interface SendResult {
  id: string | null;
  skipped?: boolean;
}

class EmailService {
  private resend: Resend | null;
  private from: string;
  private dryRun: boolean;
  private siteUrl = APP_URL;

  constructor() {
    const apiKey = process.env.RESEND_API_KEY;
    this.from = process.env.RESEND_FROM_EMAIL ?? "PolyLLM <polyllm@mail.spboucher.ai>";
    this.dryRun = !apiKey || process.env.EMAIL_DRY_RUN === "1";
    this.resend = apiKey ? new Resend(apiKey) : null;
  }

  private async send(to: string, content: T.EmailContent, kind: string): Promise<SendResult> {
    if (this.dryRun || !this.resend) {
      log.info("email dry-run", { kind, to: to.replace(/(.).+(@.*)/, "$1***$2") });
      if (process.env.EMAIL_DRY_RUN_PRINT === "1") console.log(content.text);
      return { id: null, skipped: true };
    }
    const { data, error } = await this.resend.emails.send({
      from: this.from,
      to: [to],
      subject: content.subject,
      html: content.html,
      text: content.text,
    });
    if (error) {
      log.error("email send failed", { kind, error: error.message, name: error.name });
      throw new Error(`Email delivery failed: ${error.message}`);
    }
    log.info("email sent", { kind, id: data?.id });
    return { id: data?.id ?? null };
  }

  sendVerification(to: string, url: string) {
    return this.send(to, T.verificationEmail(this.siteUrl, url), "verification");
  }
  sendWelcome(to: string, name: string) {
    return this.send(to, T.welcomeEmail(this.siteUrl, name), "welcome");
  }
  sendPasswordReset(to: string, url: string) {
    return this.send(to, T.passwordResetEmail(this.siteUrl, url), "password-reset");
  }
  sendPasswordChanged(to: string, ip?: string | null) {
    return this.send(to, T.passwordChangedEmail(this.siteUrl, new Date().toUTCString(), ip), "password-changed");
  }
  sendEmailChangeApproval(to: string, url: string, newEmail: string) {
    return this.send(to, T.emailChangeApprovalEmail(this.siteUrl, url, newEmail), "email-change-approval");
  }
  sendEmailChanged(to: string, newEmail: string) {
    return this.send(to, T.emailChangedEmail(this.siteUrl, newEmail), "email-changed");
  }
  sendAccountDeletion(to: string, url: string) {
    return this.send(to, T.accountDeletionEmail(this.siteUrl, url), "account-deletion");
  }
  sendNewLogin(to: string, ip?: string | null, userAgent?: string | null) {
    return this.send(to, T.newLoginEmail(this.siteUrl, new Date().toUTCString(), ip, userAgent), "new-login");
  }
}

let service: EmailService | null = null;
export function getEmailService(): EmailService {
  return (service ??= new EmailService());
}