export const supportedMailProviders = ["custom", "ovh", "gmail", "outlook"] as const;

export type SupportedMailProvider = typeof supportedMailProviders[number];

export type MailEnvInput = {
  smtpProvider?: string;
  smtpHost?: string;
  smtpPort?: string;
  smtpUser?: string;
  smtpPass?: string;
  smtpFrom?: string;
  smtpSecure?: string;
  smtpRequireTls?: string;
};

export type ResolvedMailConfig = {
  provider: SupportedMailProvider;
  host: string;
  port: number | null;
  secure: boolean;
  requireTLS: boolean;
  user: string;
  pass: string;
  from: string;
  missing: string[];
  ready: boolean;
};

export const providerDefaults: Record<
  Exclude<SupportedMailProvider, "custom">,
  { host: string; port: number; secure: boolean; requireTLS: boolean }
> = {
  ovh: {
    host: "smtp.mail.ovh.net",
    port: 465,
    secure: true,
    requireTLS: false,
  },
  gmail: {
    host: "smtp.gmail.com",
    port: 465,
    secure: true,
    requireTLS: false,
  },
  outlook: {
    host: "smtp.office365.com",
    port: 587,
    secure: false,
    requireTLS: true,
  },
};

function normalizeProvider(value?: string): SupportedMailProvider {
  const normalized = String(value || "")
    .trim()
    .toLowerCase();
  if (normalized === "ovh" || normalized === "gmail" || normalized === "outlook") {
    return normalized;
  }
  return "custom";
}

function parseBoolean(value?: string, fallback = false): boolean {
  const normalized = String(value || "")
    .trim()
    .toLowerCase();
  if (!normalized) {
    return fallback;
  }
  return ["1", "true", "yes", "oui", "on"].includes(normalized);
}

function parsePort(value?: string, fallback: number | null = null): number | null {
  const trimmed = String(value || "").trim();
  if (!trimmed) {
    return fallback;
  }
  const port = Number(trimmed);
  if (!Number.isFinite(port) || port <= 0) {
    return fallback;
  }
  return port;
}

export function resolveMailConfig(input: MailEnvInput): ResolvedMailConfig {
  const provider = normalizeProvider(input.smtpProvider);
  const defaults = provider === "custom" ? null : providerDefaults[provider];
  const host = String(input.smtpHost || defaults?.host || "").trim();
  const port = parsePort(input.smtpPort, defaults?.port ?? null);
  const secure = parseBoolean(input.smtpSecure, defaults?.secure ?? false);
  const requireTLS = parseBoolean(input.smtpRequireTls, defaults?.requireTLS ?? false);
  const user = String(input.smtpUser || "").trim();
  const pass = String(input.smtpPass || "").trim();
  const from = String(input.smtpFrom || "").trim();

  const missing: string[] = [];
  if (!host) {
    missing.push("SMTP_HOST");
  }
  if (!port) {
    missing.push("SMTP_PORT");
  }
  if (!from) {
    missing.push("SMTP_FROM");
  }
  if (user && !pass) {
    missing.push("SMTP_PASS");
  }
  if (pass && !user) {
    missing.push("SMTP_USER");
  }

  return {
    provider,
    host,
    port,
    secure,
    requireTLS,
    user,
    pass,
    from,
    missing,
    ready: missing.length === 0,
  };
}