/* ============================================================================
   FORM PARSING AND VALIDATION - pure
   ----------------------------------------------------------------------------
   Actions validate, components render. The action returns error CODES, never
   sentences, so the same result is correct on /en and /ar and the message
   catalogue stays the only place a wording lives.

   Both forms work without JavaScript: they are plain <Form method="post">
   submissions, so validation has to be complete on the server. There is no
   client mirror of these rules to drift out of sync.
   ========================================================================= */

import type { TranslationKey } from "~/i18n";

/**
 * The failures a reader can act on. Codes, not sentences.
 *
 * `consent` is its own code because "This field is required." is the wrong
 * sentence for an unticked checkbox: an unticked box is a decision, not an
 * omission, so it gets its own wording.
 */
export type FieldErrorCode = "required" | "email" | "consent";

export type FieldErrors = Readonly<Record<string, FieldErrorCode>>;

/**
 * Message catalogue key for each code - TOTAL over `FieldErrorCode`, so a new
 * code cannot be added without giving it a sentence in both languages. The
 * catalogue is the only place a wording lives (see the header), which is why
 * `consent` resolves here and not out of this section's own copy.
 */
export const FIELD_ERROR_KEYS: Readonly<
  Record<FieldErrorCode, TranslationKey>
> = {
  required: "form.errorRequired",
  email: "form.errorEmail",
  consent: "form.errorConsent",
};

/**
 * A field no human fills in. A bot that fills every input gets a 200 and an
 * acknowledgement, and nothing is written to the CMS.
 */
export const HONEYPOT_FIELD = "website";

/* Deliberately permissive: one @, no spaces, a dot in the domain. Anything
   stricter rejects valid addresses, and only a delivered email proves one. */
const EMAIL = /^[^\s@]+@[^\s@]+\.[^\s@]{2,}$/;

/** Upper bounds, applied by truncation rather than by an error message. */
const LIMITS = {
  name: 120,
  organisation: 160,
  email: 254,
  phone: 40,
  message: 4000,
} as const;

function field(form: FormData, name: string, limit: number): string {
  const value = form.get(name);
  return typeof value === "string" ? value.trim().slice(0, limit) : "";
}

export function isHoneypotFilled(form: FormData): boolean {
  const value = form.get(HONEYPOT_FIELD);
  return typeof value === "string" && value.trim().length > 0;
}

/* ---------------------------------------------------------------------------
   EVENT REGISTRATION - draft 4
   ------------------------------------------------------------------------ */

export interface RegistrationValues {
  readonly fullName: string;
  readonly email: string;
  readonly organisation: string;
  readonly phone: string;
  /**
   * `event-registration.consentGdpr` is REQUIRED in the CMS: a submission
   * without it is rejected with a 400, so the checkbox is a real, labelled
   * control on the form and a real validation rule here - never a hidden
   * input that consents on the reader's behalf.
   */
  readonly consentGdpr: boolean;
}

/** The name of the consent checkbox, shared by the form and the validator. */
export const CONSENT_FIELD = "consentGdpr";

/** A checkbox is either absent or carries its value ("on" by default). */
function checkbox(form: FormData, name: string): boolean {
  const value = form.get(name);
  return typeof value === "string" && value.length > 0 && value !== "false";
}

export interface Validated<T> {
  readonly values: T;
  readonly errors: FieldErrors;
  readonly valid: boolean;
}

export function validateRegistration(
  form: FormData,
): Validated<RegistrationValues> {
  const values: RegistrationValues = {
    fullName: field(form, "fullName", LIMITS.name),
    email: field(form, "email", LIMITS.email),
    organisation: field(form, "organisation", LIMITS.organisation),
    phone: field(form, "phone", LIMITS.phone),
    consentGdpr: checkbox(form, CONSENT_FIELD),
  };

  const errors: Record<string, FieldErrorCode> = {};

  if (!values.fullName) errors.fullName = "required";
  if (!values.email) errors.email = "required";
  else if (!EMAIL.test(values.email)) errors.email = "email";
  if (!values.consentGdpr) errors[CONSENT_FIELD] = "consent";

  return { values, errors, valid: Object.keys(errors).length === 0 };
}

/* ---------------------------------------------------------------------------
   OPPORTUNITY APPLICATION - draft 8
   ------------------------------------------------------------------------ */

export interface ApplicationValues {
  readonly fullName: string;
  readonly email: string;
  readonly organisation: string;
  readonly message: string;
}

export function validateApplication(
  form: FormData,
): Validated<ApplicationValues> {
  const values: ApplicationValues = {
    fullName: field(form, "fullName", LIMITS.name),
    email: field(form, "email", LIMITS.email),
    organisation: field(form, "organisation", LIMITS.organisation),
    message: field(form, "message", LIMITS.message),
  };

  const errors: Record<string, FieldErrorCode> = {};

  if (!values.fullName) errors.fullName = "required";
  if (!values.email) errors.email = "required";
  else if (!EMAIL.test(values.email)) errors.email = "email";
  if (!values.message) errors.message = "required";

  return { values, errors, valid: Object.keys(errors).length === 0 };
}