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| 1 | +/** |
| 2 | + * Provides context for managing focus within a menu component. |
| 3 | + * This context allows for tracking expanded items, focusing on specific items, |
| 4 | + * and moving focus in various directions (next, previous, parent, first child, last child). |
| 5 | + */ |
| 6 | +import React, { useCallback, useRef, useState } from "react"; |
| 7 | + |
| 8 | +interface MenuFocusContextType { |
| 9 | + expandedItems: string[]; |
| 10 | + expandItem: (id: string, expand: boolean) => void; |
| 11 | + focusedItemId: string | null; |
| 12 | + getRegisteredItems: () => Array<{ |
| 13 | + id: string; |
| 14 | + ref: React.RefObject<HTMLElement>; |
| 15 | + parentId?: string; |
| 16 | + }>; |
| 17 | + focusItem: (id: string) => void; |
| 18 | + moveFocus: ( |
| 19 | + direction: "next" | "prev" | "parent" | "firstChild" | "lastChild", |
| 20 | + ) => void; |
| 21 | + registerMenuItem: ( |
| 22 | + id: string, |
| 23 | + ref: React.RefObject<HTMLElement>, |
| 24 | + parentId?: string, |
| 25 | + ) => void; |
| 26 | +} |
| 27 | + |
| 28 | +// Create a context for menu focus |
| 29 | +const MenuFocusContext = React.createContext<MenuFocusContextType | undefined>( |
| 30 | + undefined, |
| 31 | +); |
| 32 | + |
| 33 | +// Custom hook to use the MenuFocusContext |
| 34 | +export const useMenuFocus = () => { |
| 35 | + // Get the current context value |
| 36 | + const context = React.useContext(MenuFocusContext); |
| 37 | + |
| 38 | + // If context is undefined, it means the hook is being used outside of a MenuFocusProvider |
| 39 | + /* istanbul ignore next */ |
| 40 | + if (!context) { |
| 41 | + throw new Error("useMenuFocus must be used within a MenuFocusProvider"); |
| 42 | + } |
| 43 | + |
| 44 | + // Return the current context value |
| 45 | + return context; |
| 46 | +}; |
| 47 | + |
| 48 | +export const MenuFocusProvider: React.FC<{ children: React.ReactNode }> = ({ |
| 49 | + children, |
| 50 | +}) => { |
| 51 | + // State to track expanded items |
| 52 | + const [expandedItems, setExpandedItems] = useState<string[]>([]); |
| 53 | + // State to track the currently focused item |
| 54 | + const [focusedItemId, setFocusedItemId] = useState<string | null>(null); |
| 55 | + |
| 56 | + // Ref to hold registered menu items |
| 57 | + const menuItemsRef = useRef< |
| 58 | + Map< |
| 59 | + string, |
| 60 | + { |
| 61 | + ref: React.RefObject<HTMLElement>; |
| 62 | + parentId?: string; |
| 63 | + childIds: string[]; |
| 64 | + } |
| 65 | + > |
| 66 | + >(new Map()); |
| 67 | + |
| 68 | + // Function to register a menu item |
| 69 | + // This function takes an id, a ref to the item, and an optional parentId |
| 70 | + // and stores the item in the menuItemsRef map. |
| 71 | + // If a parentId is provided, it also updates the parent's childIds array |
| 72 | + // to include the new item. |
| 73 | + const registerMenuItem = useCallback( |
| 74 | + (id: string, ref: React.RefObject<HTMLElement>, parentId?: string) => { |
| 75 | + menuItemsRef.current.set(id, { |
| 76 | + ref, |
| 77 | + parentId, |
| 78 | + childIds: [], |
| 79 | + }); |
| 80 | + |
| 81 | + if (parentId) { |
| 82 | + const parentItem = menuItemsRef.current.get(parentId); |
| 83 | + /* istanbul ignore else */ |
| 84 | + if (parentItem) { |
| 85 | + parentItem.childIds.push(id); |
| 86 | + } |
| 87 | + } |
| 88 | + }, |
| 89 | + [], |
| 90 | + ); |
| 91 | + |
| 92 | + // Function to get all registered menu items |
| 93 | + // This function returns an array of objects, each containing the id, |
| 94 | + // ref, parentId, and childIds of the registered items. |
| 95 | + const getRegisteredItems = useCallback(() => { |
| 96 | + const items = Array.from(menuItemsRef.current.entries()).map( |
| 97 | + ([id, { ref, parentId, childIds }]) => ({ |
| 98 | + id, |
| 99 | + ref, |
| 100 | + parentId, |
| 101 | + childIds, |
| 102 | + }), |
| 103 | + ); |
| 104 | + return items; |
| 105 | + }, []); |
| 106 | + |
| 107 | + // Function to focus on a specific menu item |
| 108 | + // This function takes an id and focuses the corresponding item |
| 109 | + // by calling the focus method on its ref. |
| 110 | + // It also updates the focusedItemId state to the new id. |
| 111 | + const focusItem = useCallback((id: string) => { |
| 112 | + const item = menuItemsRef.current.get(id); |
| 113 | + /* istanbul ignore else */ |
| 114 | + if (item && item.ref.current) { |
| 115 | + item.ref.current.focus(); |
| 116 | + setFocusedItemId(id); |
| 117 | + } |
| 118 | + }, []); |
| 119 | + |
| 120 | + // Function to expand or collapse a menu item |
| 121 | + // This function takes an id and a boolean value (expand) |
| 122 | + // and updates the expandedItems state accordingly. |
| 123 | + // If expand is true, it adds the id to the expandedItems array; |
| 124 | + // otherwise, it removes the id from the array. |
| 125 | + const expandItem = useCallback((id: string, expand: boolean) => { |
| 126 | + if (expand) { |
| 127 | + setExpandedItems((prev) => [...prev, id]); |
| 128 | + } else { |
| 129 | + setExpandedItems((prev) => prev.filter((itemId) => itemId !== id)); |
| 130 | + } |
| 131 | + }, []); |
| 132 | + |
| 133 | + // Function to move focus in a specific direction |
| 134 | + // This function takes a direction (next, prev, parent, firstChild, lastChild) |
| 135 | + // and moves the focus accordingly. |
| 136 | + // It uses the current focusedItemId to determine the current item |
| 137 | + // and then finds the next item based on the direction. |
| 138 | + // It also handles expanding/collapsing items as needed. |
| 139 | + const moveFocus = useCallback( |
| 140 | + (direction: "next" | "prev" | "parent" | "firstChild" | "lastChild") => { |
| 141 | + /* istanbul ignore if */ |
| 142 | + if (!focusedItemId) return; |
| 143 | + |
| 144 | + let allItems = []; |
| 145 | + let visibleItems = []; |
| 146 | + let currentIndex = -1; |
| 147 | + |
| 148 | + // Get the current item based on the focusedItemId |
| 149 | + const currentItem = menuItemsRef.current.get(focusedItemId); |
| 150 | + |
| 151 | + // If the current item is not found, return early |
| 152 | + /* istanbul ignore if */ |
| 153 | + if (!currentItem) return; |
| 154 | + |
| 155 | + switch (direction) { |
| 156 | + // Move focus to the parent item |
| 157 | + case "parent": |
| 158 | + /* istanbul ignore else */ |
| 159 | + if (currentItem.parentId) { |
| 160 | + focusItem(currentItem.parentId); |
| 161 | + } |
| 162 | + break; |
| 163 | + |
| 164 | + // Move focus to the first child |
| 165 | + // If the current item has children and is not already expanded, |
| 166 | + // expand it and focus on the first child |
| 167 | + case "firstChild": |
| 168 | + /* istanbul ignore else */ |
| 169 | + if (currentItem.childIds.length > 0) { |
| 170 | + if (!expandedItems.includes(focusedItemId)) { |
| 171 | + expandItem(focusedItemId, true); |
| 172 | + } |
| 173 | + focusItem(currentItem.childIds[0]); |
| 174 | + } |
| 175 | + break; |
| 176 | + |
| 177 | + // Move focus to the last child |
| 178 | + // Moving backwards through the menu works slightly differently: |
| 179 | + // If the current item has children, get the last child. Before focusing on it, |
| 180 | + // check if the last child is expanded. If it is, focus on its last child. |
| 181 | + // If the last child is not expanded (i.e. it's just a link), focus on it directly. |
| 182 | + case "lastChild": |
| 183 | + /* istanbul ignore else */ |
| 184 | + if (currentItem.childIds.length > 0) { |
| 185 | + const lastChild = |
| 186 | + currentItem.childIds[currentItem.childIds.length - 1]; |
| 187 | + /* istanbul ignore else */ |
| 188 | + if (lastChild) { |
| 189 | + /* istanbul ignore if */ |
| 190 | + if (expandedItems.includes(lastChild)) { |
| 191 | + const lastChildItem = getRegisteredItems().find( |
| 192 | + (item) => item.id === lastChild, |
| 193 | + ); |
| 194 | + if (lastChildItem) { |
| 195 | + focusItem( |
| 196 | + lastChildItem.childIds[lastChildItem.childIds.length - 1], |
| 197 | + ); |
| 198 | + } |
| 199 | + } else { |
| 200 | + focusItem(lastChild); |
| 201 | + } |
| 202 | + } |
| 203 | + } |
| 204 | + break; |
| 205 | + |
| 206 | + // Move focus to the next or previous item |
| 207 | + // This case handles both next and previous focus movement. |
| 208 | + // Whilst this functionality is not currently used in the menu, |
| 209 | + // it is included for completeness/future-proofing. |
| 210 | + /* istanbul ignore next */ |
| 211 | + default: |
| 212 | + allItems = Array.from(menuItemsRef.current.keys()); |
| 213 | + visibleItems = allItems.filter((id) => { |
| 214 | + const item = menuItemsRef.current.get(id); |
| 215 | + if (!item || !item.parentId) return true; |
| 216 | + |
| 217 | + const parentVisible = expandedItems.includes(item.parentId); |
| 218 | + return parentVisible; |
| 219 | + }); |
| 220 | + |
| 221 | + currentIndex = visibleItems.indexOf(focusedItemId); |
| 222 | + if (currentIndex !== -1) { |
| 223 | + const nextIndex = |
| 224 | + direction === "next" |
| 225 | + ? (currentIndex + 1) % visibleItems.length |
| 226 | + : (currentIndex - 1 + visibleItems.length) % |
| 227 | + visibleItems.length; |
| 228 | + |
| 229 | + focusItem(visibleItems[nextIndex]); |
| 230 | + } |
| 231 | + break; |
| 232 | + } |
| 233 | + }, |
| 234 | + [focusedItemId, focusItem, expandedItems, expandItem, getRegisteredItems], |
| 235 | + ); |
| 236 | + |
| 237 | + const value = { |
| 238 | + expandedItems, |
| 239 | + expandItem, |
| 240 | + focusedItemId, |
| 241 | + focusItem, |
| 242 | + getRegisteredItems, |
| 243 | + registerMenuItem, |
| 244 | + moveFocus, |
| 245 | + }; |
| 246 | + |
| 247 | + // Provide the current context value to the MenuFocusContext |
| 248 | + return ( |
| 249 | + <MenuFocusContext.Provider value={value}> |
| 250 | + {children} |
| 251 | + </MenuFocusContext.Provider> |
| 252 | + ); |
| 253 | +}; |
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