import React, { createContext, useContext } from "react";

/**
 * The patient portal's navigation, published so that MORE THAN ONE SURFACE CAN RENDER IT.
 *
 * / design decision D6 - "nothing important lives ONLY behind an icon". The patient home
 * carries an "Everything else" list so a patient who never opens the hamburger can still reach every
 * part of the product. That list MUST be the same array the sidebar renders, never a second
 * hand-written one, for two reasons and the second is a safety one:
 *
 * 1. DRIFT - a destination added to the sidebar later would not appear in the home list, and the
 * guarantee ("every part of the product") would be false with nothing failing. This codebase's
 * most common defect is a surface deriving its own answer to a question another surface already
 * answers (claude-4's UI pass named it as one of the three biggest root causes).
 *
 * 2. ADOLESCENT FILTERING - `patientMenuItems` is filtered by `ADOLESCENT_18_PLUS_NAV_IDS`
 * before it reaches the sidebar. A hand-rolled home list would NOT inherit that filter and
 * would surface messaging and collaboration teams to a minor whose own portal deliberately
 * hides them. Consuming the filtered array makes that impossible rather than remembered.
 *
 * The provider carries the array DashboardPage already computed. Nothing is moved and no logic is
 * duplicated - this is a publication point, not a second source.
 */
/**
 * The patient's own profile page. The drawer's "Edit my profile", the home's "My details" door and
 * the record's "My details" row all open it, so they read this one string. The chart's
 * `/dashboard/patient/profile` is a second rendering of the same page inside the record shell,
 * titled as the record, and nothing should link to it.
 */
export const MY_PROFILE_PATH = "/dashboard/profile";

export type SidebarMenuItem = {
  id: string;
  label: string;
  icon: React.ReactNode;
  to?: string;
  onClick?: () => void;
  activeMatch?: "exact" | "prefix";
  activePaths?: string[];
  /** Routes under `activePaths` that belong to another group, so this one stays unlit there. */
  exceptPaths?: string[];
  unreadCount?: number;
  showUnread?: boolean;
  /** Some reads behind the count failed: it is a floor, not an exact number. */
  unreadIncomplete?: boolean;
  isLogout?: boolean;
  children?: SidebarMenuItem[];
};

/** One reachable place in the patient portal, as the home list renders it. */
export type PatientDestination = {
  id: string;
  label: string;
  to: string;
  /** The nearest ancestor group's label ("Clinical Data"), or undefined for a top-level row. */
  section?: string;
  unreadCount?: number;
  showUnread?: boolean;
};

/**
 * The one item the home list must NOT carry. Log Out is a control, not a destination - and it is
 * not a hypothetical: claude-4's nav sweep signed itself out by walking `.dashboard-nav-item`
 * indiscriminately, because Log Out looks exactly like every other row. A list whose stated purpose
 * is "tap anything here to go somewhere" must not contain the one row that ends the session.
 */
const isLogoutItem = (item: SidebarMenuItem) => item.isLogout === true || item.to === "#";

/** The home page itself. Offering a row that reloads the page you are on is noise, not navigation. */
const HOME_ITEM_ID = "overview";

/**
 * Flattens the patient nav into every place a patient can actually go.
 *
 * A GROUP (no `to`, has children) contributes no row of its own - it has no landing page, so a row
 * for it would either dead-end or navigate somewhere arbitrary. Its label becomes the section
 * heading above its own destinations instead, which is what makes a 40-item list readable.
 *
 * The patient's own chart has NO in-page navigation: `PatientChartSidebar` is rendered only on
 * the STAFF side (`!isPatient`), so a patient landing on "My Records" cannot reach Conditions or
 * Medications from there. That is precisely why this flattens all the way to the leaves rather than
 * stopping at the top level and trusting the destination to carry the patient onwards.
 */
export const patientHomeDestinations = (
  items: SidebarMenuItem[],
  section?: string,
): PatientDestination[] =>
  items.flatMap((item) => {
    if (isLogoutItem(item)) return [];
    if (!section && item.id === HOME_ITEM_ID) return [];

    if (item.to) {
      return [
        {
          id: item.id,
          label: item.label,
          to: item.to,
          section,
          unreadCount: item.unreadCount,
          showUnread: item.showUnread,
        },
      ];
    }

    return item.children?.length ? patientHomeDestinations(item.children, item.label) : [];
  });

const PatientNavContext = createContext<SidebarMenuItem[]>([]);

export const PatientNavProvider = ({
  items,
  children,
}: {
  items: SidebarMenuItem[];
  children: React.ReactNode;
}) => <PatientNavContext.Provider value={items}>{children}</PatientNavContext.Provider>;

/**
 * Returns the patient nav, or an empty array outside the dashboard shell.
 *
 * Deliberately does NOT throw when unmounted. The same rule landed on: an optional
 * refinement must never be able to take down a working surface. A missing provider costs the
 * "Everything else" list, not the patient's home page.
 */
export const usePatientNav = (): SidebarMenuItem[] => useContext(PatientNavContext);