/* ============================================================================
   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,
  /** Free text - "Tripoli", "Sabha and the south". Not a taxonomy. */
  region: 160,
  /** Free text on purpose: "4", "under a year", "since 2016" are all answers. */
  years: 40,
} 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 };
}

/* ---------------------------------------------------------------------------
   GET INVOLVED - the application form on the section's own page
   ----------------------------------------------------------------------------
   The redesign draft puts a single application form under the three pathway
   cards, with five fields and a proposal summary. It is the same contract as
   the per-call form above, plus the two answers the draft asks for (region of
   operation, years of operating history) and the pathway being applied under.

   WHAT IS REQUIRED, AND WHY EXACTLY THOSE THREE
   `application.applicantName` and `application.email` are `required: true` in
   the CMS, so a submission without them is a 400 that costs the applicant
   everything they typed - they are validated here first. The summary is
   required because an application with no case in it cannot be reviewed.

   Everything else is optional BY DESIGN, not by omission: the page invites
   "a civil society organisation or an individual", so an organisation name, a
   region and a number of years of operating history cannot be demanded
   without shutting the individuals out of the form that invites them.

   `yearsOperating` is a STRING, deliberately. "4", "under a year" and "since
   2016" are all true answers to the draft's question, and a number input would
   reject two of them; it reaches the CMS inside `answers`, where a reviewer
   reads it, and nothing computes on it.
   ------------------------------------------------------------------------ */

/**
 * The three ways in, as the draft names them. The value is carried in the
 * query string (`?route=`) so a pathway card can open the form already set to
 * its own route, and it is submitted as a real `<select>` so the reader can
 * correct it - and so the choice still travels with scripting off.
 */
export type ApplicationRoute = "calls" | "network" | "sessions";

export const APPLICATION_ROUTES = [
  "calls",
  "network",
  "sessions",
] as const satisfies readonly ApplicationRoute[];

export function isApplicationRoute(value: unknown): value is ApplicationRoute {
  return (
    typeof value === "string" &&
    (APPLICATION_ROUTES as readonly string[]).includes(value)
  );
}

export interface PathwayApplicationValues {
  readonly route: ApplicationRoute;
  readonly organisation: string;
  readonly fullName: string;
  readonly email: string;
  readonly region: string;
  readonly yearsOperating: string;
  readonly summary: string;
}

/** The field name of the pathway select, shared by the form and the parser. */
export const ROUTE_FIELD = "route";

export function validatePathwayApplication(
  form: FormData,
  fallbackRoute: ApplicationRoute = "calls",
): Validated<PathwayApplicationValues> {
  const submittedRoute = form.get(ROUTE_FIELD);

  const values: PathwayApplicationValues = {
    // An unknown value is not an error the reader can act on - it cannot be
    // produced by the select - so it falls back rather than blocking a submit.
    route: isApplicationRoute(submittedRoute) ? submittedRoute : fallbackRoute,
    organisation: field(form, "organisation", LIMITS.organisation),
    fullName: field(form, "fullName", LIMITS.name),
    email: field(form, "email", LIMITS.email),
    region: field(form, "region", LIMITS.region),
    yearsOperating: field(form, "yearsOperating", LIMITS.years),
    summary: field(form, "summary", 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.summary) errors.summary = "required";

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

/** The form's fields in reading order - the error summary lists them in it. */
export const PATHWAY_APPLICATION_FIELDS = [
  "organisation",
  "fullName",
  "email",
  "region",
  "yearsOperating",
  "summary",
] as const;

export type PathwayApplicationField =
  (typeof PATHWAY_APPLICATION_FIELDS)[number];