indexCrudReducer.ts ➔ reducer - Code Metrics - Inspection of "Merge branch 'dev' into task/explore-skills-ui" - GCTC-NTGC/TalentCloud - Measure and Improve Code Quality continuously with Scrutinizer

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Push — task/explore-skills-ui ( d41a63...af1244 )

by Yonathan

created 2021-01-21 15:47 UTC

indexCrudReducer.ts ➔ reducer C

↳ Parent: resources/assets/js/hooks/webResourceHooks/indexCrudReducer.ts

Complexity

Conditions

Size

Total Lines	135
Code Lines	81

Duplication

Lines	0
Ratio	0 %

Importance

Changes

Metric	Value
eloc	81
dl	0
loc	135
rs	6.6884
c	0
b	0
f	0
cc	6

How to fix Long Method

import { FetchError } from "../../helpers/httpRequests";
import {
  decrement,
  deleteProperty,
  filterObjectProps,
  getId,
  hasKey,
  mapToObjectTrans,
} from "../../helpers/queries";
import { ResourceStatus } from "./types";

export enum ActionTypes {
  IndexStart = "INDEX_START",
  IndexFulfill = "INDEX_FULFILL",
  IndexReject = "INDEX_REJECT",

  CreateStart = "CREATE_START",
  CreateFulfill = "CREATE_FULFILL",
  CreateReject = "CREATE_REJECT",

  UpdateStart = "UPDATE_START",
  UpdateFulfill = "UPDATE_FULFILL",
  UpdateReject = "UPDATE_REJECT",

  DeleteStart = "DELETE_START",
  DeleteFulfill = "DELETE_FULFILL",
  DeleteReject = "DELETE_REJECT",
}

export type IndexStartAction = { type: ActionTypes.IndexStart };
export type IndexFulfillAction<T> = {
  type: ActionTypes.IndexFulfill;
  payload: T[];
};
export type IndexRejectAction = {
  type: ActionTypes.IndexReject;
  payload: Error | FetchError;
};

export type CreateStartAction<T> = {
  type: ActionTypes.CreateStart;
  meta: { item: T };
};
export type CreateFulfillAction<T> = {
  type: ActionTypes.CreateFulfill;
  payload: T;
  meta: { item: T };
};
export type CreateRejectAction<T> = {
  type: ActionTypes.CreateReject;
  payload: Error | FetchError;
  meta: { item: T };
};

export type UpdateStartAction<T> = {
  type: ActionTypes.UpdateStart;
  meta: { id: number; item: T };
};
export type UpdateFulfillAction<T> = {
  type: ActionTypes.UpdateFulfill;
  payload: T;
  meta: { id: number; item: T };
};
export type UpdateRejectAction<T> = {
  type: ActionTypes.UpdateReject;
  payload: Error | FetchError;
  meta: { id: number; item: T };
};

export type DeleteStartAction = {
  type: ActionTypes.DeleteStart;
  meta: { id: number };
};
export type DeleteFulfillAction = {
  type: ActionTypes.DeleteFulfill;
  meta: { id: number };
};
export type DeleteRejectAction = {
  type: ActionTypes.DeleteReject;
  payload: Error | FetchError;
  meta: { id: number };
};
export type AsyncAction<T> =
  | IndexStartAction
  | IndexFulfillAction<T>
  | IndexRejectAction
  | CreateStartAction<T>
  | CreateFulfillAction<T>
  | CreateRejectAction<T>
  | UpdateStartAction<T>
  | UpdateFulfillAction<T>
  | UpdateRejectAction<T>
  | DeleteStartAction
  | DeleteFulfillAction
  | DeleteRejectAction;

export interface ResourceState<T> {
  indexMeta: {
    status: ResourceStatus;
    pendingCount: number;
    error: Error | FetchError | undefined;
  };
  createMeta: {
    status: ResourceStatus;
    pendingCount: number;
    error: Error | FetchError | undefined; // Only stores the most recent error;
  };
  values: {
    [id: string]: {
      value: T;
      error: Error | FetchError | undefined;
      status: ResourceStatus;
      pendingCount: number;
    };
  };
}

export function initializeState<T extends { id: number }>(
  items: T[],
): ResourceState<T> {
  return {
    indexMeta: {
      status: "initial",
      pendingCount: 0,
      error: undefined,
    },
    createMeta: {
      status: "initial",
      pendingCount: 0,
      error: undefined,
    },
    values: mapToObjectTrans(items, getId, (item) => ({
      value: item,
      error: undefined,
      status: "initial",
      pendingCount: 0,
    })),
  };
}

type StateValues<T> = ResourceState<T>["values"];

function mergeIndexItem<T extends { id: number }>(
  values: StateValues<T>,
  item: T,
): StateValues<T> {
  if (hasKey(values, item.id)) {
    // We leave the pending count as is, in case an update or delete is in progress for this item.
    // We do overwrite errors, and set status to "fulfilled" if it was "initial" or "rejected"
    return {
      ...values,
      [item.id]: {
        ...values[item.id],
        value: item,
        status: values[item.id].status === "pending" ? "pending" : "fulfilled",
        error: undefined,
      },
    };
  }
  return {
    ...values,
    [item.id]: {
      value: item,
      error: undefined,
      status: "fulfilled",
      pendingCount: 0,
    },
  };
}

/**
 * Updates values in response to INDEX FULFILLED action:
 *   - Updates the value of existing items without modifying item-specific metadata (related to UPDATE and DELETE requests).
 *   - Creates new items (with "fulfilled" status metadata).
 *   - Deletes existing state items that are not part of the new payload.
 * @param values
 * @param payload
 */
function mergeIndexPayload<T extends { id: number }>(
  values: StateValues<T>,
  payload: T[],
): StateValues<T> {
  // Update or create a values entry for each item in the payload.
  const newValues = payload.reduce(mergeIndexItem, values);
  // Delete any values entries that don't exist in the new payload.
  const payloadIds = payload.map(getId);
  return filterObjectProps(newValues, (item) =>
    payloadIds.includes(item.value.id),
  );
}

/**
 * Updates values in response to CREATE FULFILLED action.
 * - Adds the new item to values, with "fulfilled" status.
 * - Note: If newly created item has the same id as an existing item, update that item instead.
 *    This should never happen during normal interaction with a REST api.
 * @param values
 * @param payload
 */
function mergeCreatePayload<T extends { id: number }>(
  values: StateValues<T>,
  payload: T,
): StateValues<T> {
  if (hasKey(values, payload.id)) {
    // It doesn't really make sense for the result of a create request to already exist...
    // But we have to trust the latest response from the server. Update the existing item.
    return {
      ...values,
      [payload.id]: {
        value: payload,
        status: values[payload.id].pendingCount <= 1 ? "fulfilled" : "pending",
        pendingCount: decrement(values[payload.id].pendingCount),
        error: undefined,
      },
    };
  }
  return {
    ...values,
    [payload.id]: {
      value: payload,
      error: undefined,
      status: "fulfilled",
      pendingCount: 0,
    },
  };
}

/**
 * Updates values in response to UPDATE START action.
 * - Updates metadata for updated item.
 * - Does nothing if the item does not yet exist.
 * @param values
 * @param action
 */
function mergeUpdateStart<T extends { id: number }>(
  values: StateValues<T>,
  action: UpdateStartAction<T>,
): StateValues<T> {
  if (!hasKey(values, action.meta.id)) {
    // Do not update values. We don't want to create a new value in case the request fails and it doesn't represent anything on the server.
    // NOTE: if we move to optimistic updates, we should add to values here.
    return values;
  }
  return {
    ...values,
    [action.meta.id]: {
      // TODO: if we wanted to do an optimistic update, we could save action.payload.item here.
      // But we would need some way to reverse it if it failed.
      ...values[action.meta.id],
      status: "pending",
      pendingCount: values[action.meta.id].pendingCount + 1,
      error: undefined,
    },
  };
}
/**
 * Updates values in response to UPDATE FULFILLED action.
 * - Updates metadata for updated item and overwrites value with payload.
 * @param values
 * @param action
 */
function mergeUpdateFulfill<T extends { id: number }>(
  values: StateValues<T>,
  action: UpdateFulfillAction<T>,
): StateValues<T> {
  if (!hasKey(values, action.meta.id)) {
    // Even though it didn't exist in local state yet, if the server says it exists, it exists.
    return {
      ...values,
      [action.meta.id]: {
        value: action.payload,
        status: "fulfilled",
        pendingCount: 0,
        error: undefined,
      },
    };
  }
  return {
    ...values,
    [action.meta.id]: {
      value: action.payload,
      status:
        values[action.meta.id].pendingCount <= 1 ? "fulfilled" : "pending",
      pendingCount: decrement(values[action.meta.id].pendingCount),
      error: undefined,
    },
  };
}
/**
 * Updates values in response to UPDATE REJECTED action.
 * - DOES NOT throw error if item does exist, unlike other update mergeUpdate functions.
 *   UPDATE REJECTED action already represents a graceful response to an error.
 *   There is no relevant metadata to update, and nowhere to store the error, so return state as is.
 * - Otherwise updates metdata for item and overwrites error with payload.f
 * @param values
 * @param action
 */
function mergeUpdateReject<T extends { id: number }>(
  values: StateValues<T>,
  action: UpdateRejectAction<T>,
): StateValues<T> {
  if (!hasKey(values, action.meta.id)) {
    return values;
  }
  return {
    ...values,
    [action.meta.id]: {
      ...values[action.meta.id],
      status: values[action.meta.id].pendingCount <= 1 ? "rejected" : "pending",
      pendingCount: decrement(values[action.meta.id].pendingCount),
      error: action.payload,
    },
  };
}
/**
 * Updates values in response to DELETE START action.
 * Updates metadata for item if it exists.
 *
 * Does not throw an error if item does not exist, as there are plausible scenarios (eg mupliple queued DELETE requests) that could cause this.
 * @param values
 * @param action
 */
function mergeDeleteStart<T extends { id: number }>(
  values: StateValues<T>,
  action: DeleteStartAction,
): StateValues<T> {
  if (!hasKey(values, action.meta.id)) {
    return values;
  }
  return {
    ...values,
    [action.meta.id]: {
      ...values[action.meta.id],
      status: "pending",
      pendingCount: values[action.meta.id].pendingCount + 1,
      error: undefined,
    },
  };
}
/**
 * Updates values in response to DELETE FULFILLED action.
 * Deletes the entire value entry, metadata included. (No effect if entry already doesn't exist.)
 *
 * Note: We can safely delete the metadata because any subsequent DELETE or UPDATE requests
 *   on the same item will presumably be REJECTED by the REST api.
 *   DELETE REJECTED and UPDATE REJECTED actions are gracefully handled by the reducer,
 *   even when no metadata is present.
 * @param values
 * @param action
 */
function mergeDeleteFulfill<T extends { id: number }>(
  values: StateValues<T>,
  action: DeleteFulfillAction,
): StateValues<T> {
  return deleteProperty(values, action.meta.id);
}

/**
 * Updates values in response to DELETE REJECTED action.
 * Updates metadata for item if it exists.
 *
 * Does not throw an error if item does not exist, as there are plausible scenarios (eg mupliple queued DELETE requests) that could cause this.
 * @param values
 * @param action
 */
function mergeDeleteReject<T extends { id: number }>(
  values: StateValues<T>,
  action: DeleteRejectAction,
): StateValues<T> {
  if (!hasKey(values, action.meta.id)) {
    return values;
  }
  return {
    ...values,
    [action.meta.id]: {
      ...values[action.meta.id],
      status: values[action.meta.id].pendingCount <= 1 ? "rejected" : "pending",
      pendingCount: decrement(values[action.meta.id].pendingCount),
      error: action.payload,
    },
  };
}

/**
 * This Reducer manages the lifecycle of several http requests related to a single type of resource.
 * It helps keep a local version of a list of entities in sync with a REST server.
 *
 * There are 4 types of request:
 *   - INDEX requests fetch a list of items from the server.
 *   - CREATE requests create add a new item to the list.
 *   - UPDATE requests modify a single existing item in the list.
 *   - DELETE requests remove a single existing item from the list.
 * Every request has a lifecycle reflected by 3 possible states, resulting in a total of 12 possible reducer Actions.
 *   - START: every request begins with a START action.
 *   - FULFILLED: a successful request dispatches a FULFILLED action, with the response as its payload.
 *   - REJECTED: a request that fails for any reason dispatches a REJECTED action, with the Error as its payload.
 * Any data sent with the requests is included in the actions (in all three states) as metadata.
 *
 * The Reducer's State contains:
 *   - values: a map of items and associated request metadata (specifically UPDATE and DELETE request metadata)
 *   - indexMeta: metadata associated with INDEX requests, as they don't relate to specific items
 *   - createMeta: metadata associated with CREATE requests, as they don't relate to existing items
 *
 * The metadata associated with a request includes:
 *   - status: one of four values:
 *     - "initial" if a request has never been made
 *     - "pending" if ANY request is in progress which could modify this resource
 *     - "fulfilled" if the last completed request succeeded and no other request is in progress
 *     - "rejected" if the last completed request failed and no other request is in progress
 *   - pendingCount: stores the number of requests in progress. This helps account for the possibility of multiple requests being started in succession, and means one request could finish and the resource still be considered "pending".
 *   - error: stores the last error recieved from a REJECTED action. Overwritten with undefined if a later request is STARTed or FULFILLED.
 *
 * Notes about item values:
 *   - Its possible to include items in the initial state and then not begin any requests, in which case there will be existing values with the "initial" status.
 *   - REJECTED actions do not overwrite the value. Therefore when a request fails and status becomes "rejected", the last good value is still available (though it may become out-of-sync with the REST api).
 * @param state
 * @param action
 */
export function reducer<T extends { id: number }>(
  state: ResourceState<T>,
  action: AsyncAction<T>,
): ResourceState<T> {
  switch (action.type) {
    case ActionTypes.IndexStart:
      return {
        ...state,
        indexMeta: {
          ...state.indexMeta,
          status: "pending",
          pendingCount: state.indexMeta.pendingCount + 1,
          error: undefined,
        },
      };
    case ActionTypes.IndexFulfill:
      return {
        ...state,
        indexMeta: {
          ...state.indexMeta,
          status: state.indexMeta.pendingCount <= 1 ? "fulfilled" : "pending",
          pendingCount: decrement(state.indexMeta.pendingCount),
          error: undefined,
        },
        values: mergeIndexPayload(state.values, action.payload),
      };
    case ActionTypes.IndexReject:
      return {
        ...state,
        indexMeta: {
          ...state.indexMeta,
          status: state.indexMeta.pendingCount <= 1 ? "rejected" : "pending",
          pendingCount: decrement(state.indexMeta.pendingCount),
          error: action.payload,
        },
      };
    case ActionTypes.CreateStart:
      // TODO: We could add an optimistic update here.
      return {
        ...state,
        createMeta: {
          ...state.createMeta,
          status: "pending",
          pendingCount: state.createMeta.pendingCount + 1,
          error: undefined,
        },
      };
    case ActionTypes.CreateFulfill:
      return {
        ...state,
        createMeta: {
          status: state.createMeta.pendingCount <= 1 ? "fulfilled" : "pending",
          pendingCount: decrement(state.createMeta.pendingCount),
          error: undefined,
        },
        values: mergeCreatePayload(state.values, action.payload),
      };
    case ActionTypes.CreateReject:
      return {
        ...state,
        createMeta: {
          status: state.createMeta.pendingCount <= 1 ? "rejected" : "pending",
          pendingCount: decrement(state.createMeta.pendingCount),
          error: action.payload,
        },
      };
    case ActionTypes.UpdateStart:
      return {
        ...state,
        values: mergeUpdateStart(state.values, action),
      };
    case ActionTypes.UpdateFulfill:
      return {
        ...state,
        values: mergeUpdateFulfill(state.values, action),
      };
    case ActionTypes.UpdateReject:
      return {
        ...state,
        values: mergeUpdateReject(state.values, action),
      };
    case ActionTypes.DeleteStart:
      return {
        ...state,
        values: mergeDeleteStart(state.values, action),
      };
    case ActionTypes.DeleteFulfill:
      return {
        ...state,
        values: mergeDeleteFulfill(state.values, action),
      };
    case ActionTypes.DeleteReject:
      return {
        ...state,
        values: mergeDeleteReject(state.values, action),
      };

    default:
      return state;
  }
}

export default reducer;


1			import { FetchError } from "../../helpers/httpRequests";
2			import {
3			decrement,
4			deleteProperty,
5			filterObjectProps,
6			getId,
7			hasKey,
8			mapToObjectTrans,
9			} from "../../helpers/queries";
10			import { ResourceStatus } from "./types";
11
12			export enum ActionTypes {
13			IndexStart = "INDEX_START",
14			IndexFulfill = "INDEX_FULFILL",
15			IndexReject = "INDEX_REJECT",
16
17			CreateStart = "CREATE_START",
18			CreateFulfill = "CREATE_FULFILL",
19			CreateReject = "CREATE_REJECT",
20
21			UpdateStart = "UPDATE_START",
22			UpdateFulfill = "UPDATE_FULFILL",
23			UpdateReject = "UPDATE_REJECT",
24
25			DeleteStart = "DELETE_START",
26			DeleteFulfill = "DELETE_FULFILL",
27			DeleteReject = "DELETE_REJECT",
28			}
29
30			export type IndexStartAction = { type: ActionTypes.IndexStart };
31			export type IndexFulfillAction<T> = {
32			type: ActionTypes.IndexFulfill;
33			payload: T[];
34			};
35			export type IndexRejectAction = {
36			type: ActionTypes.IndexReject;
37			payload: Error \| FetchError;
38			};
39
40			export type CreateStartAction<T> = {
41			type: ActionTypes.CreateStart;
42			meta: { item: T };
43			};
44			export type CreateFulfillAction<T> = {
45			type: ActionTypes.CreateFulfill;
46			payload: T;
47			meta: { item: T };
48			};
49			export type CreateRejectAction<T> = {
50			type: ActionTypes.CreateReject;
51			payload: Error \| FetchError;
52			meta: { item: T };
53			};
54
55			export type UpdateStartAction<T> = {
56			type: ActionTypes.UpdateStart;
57			meta: { id: number; item: T };
58			};
59			export type UpdateFulfillAction<T> = {
60			type: ActionTypes.UpdateFulfill;
61			payload: T;
62			meta: { id: number; item: T };
63			};
64			export type UpdateRejectAction<T> = {
65			type: ActionTypes.UpdateReject;
66			payload: Error \| FetchError;
67			meta: { id: number; item: T };
68			};
69
70			export type DeleteStartAction = {
71			type: ActionTypes.DeleteStart;
72			meta: { id: number };
73			};
74			export type DeleteFulfillAction = {
75			type: ActionTypes.DeleteFulfill;
76			meta: { id: number };
77			};
78			export type DeleteRejectAction = {
79			type: ActionTypes.DeleteReject;
80			payload: Error \| FetchError;
81			meta: { id: number };
82			};
83			export type AsyncAction<T> =
84			\| IndexStartAction
85			\| IndexFulfillAction<T>
86			\| IndexRejectAction
87			\| CreateStartAction<T>
88			\| CreateFulfillAction<T>
89			\| CreateRejectAction<T>
90			\| UpdateStartAction<T>
91			\| UpdateFulfillAction<T>
92			\| UpdateRejectAction<T>
93			\| DeleteStartAction
94			\| DeleteFulfillAction
95			\| DeleteRejectAction;
96
97			export interface ResourceState<T> {
98			indexMeta: {
99			status: ResourceStatus;
100			pendingCount: number;
101			error: Error \| FetchError \| undefined;
102			};
103			createMeta: {
104			status: ResourceStatus;
105			pendingCount: number;
106			error: Error \| FetchError \| undefined; // Only stores the most recent error;
107			};
108			values: {
109			[id: string]: {
110			value: T;
111			error: Error \| FetchError \| undefined;
112			status: ResourceStatus;
113			pendingCount: number;
114			};
115			};
116			}
117
118			export function initializeState<T extends { id: number }>(
119			items: T[],
120			): ResourceState<T> {
121			return {
122			indexMeta: {
123			status: "initial",
124			pendingCount: 0,
125			error: undefined,
126			},
127			createMeta: {
128			status: "initial",
129			pendingCount: 0,
130			error: undefined,
131			},
132			values: mapToObjectTrans(items, getId, (item) => ({
133			value: item,
134			error: undefined,
135			status: "initial",
136			pendingCount: 0,
137			})),
138			};
139			}
140
141			type StateValues<T> = ResourceState<T>["values"];
142
143			function mergeIndexItem<T extends { id: number }>(
144			values: StateValues<T>,
145			item: T,
146			): StateValues<T> {
147			if (hasKey(values, item.id)) {
148			// We leave the pending count as is, in case an update or delete is in progress for this item.
149			// We do overwrite errors, and set status to "fulfilled" if it was "initial" or "rejected"
150			return {
151			...values,
152			[item.id]: {
153			...values[item.id],
154			value: item,
155			status: values[item.id].status === "pending" ? "pending" : "fulfilled",
156			error: undefined,
157			},
158			};
159			}
160			return {
161			...values,
162			[item.id]: {
163			value: item,
164			error: undefined,
165			status: "fulfilled",
166			pendingCount: 0,
167			},
168			};
169			}
170
171			/**
172			* Updates values in response to INDEX FULFILLED action:
173			* - Updates the value of existing items without modifying item-specific metadata (related to UPDATE and DELETE requests).
174			* - Creates new items (with "fulfilled" status metadata).
175			* - Deletes existing state items that are not part of the new payload.
176			* @param values
177			* @param payload
178			*/
179			function mergeIndexPayload<T extends { id: number }>(
180			values: StateValues<T>,
181			payload: T[],
182			): StateValues<T> {
183			// Update or create a values entry for each item in the payload.
184			const newValues = payload.reduce(mergeIndexItem, values);
185			// Delete any values entries that don't exist in the new payload.
186			const payloadIds = payload.map(getId);
187			return filterObjectProps(newValues, (item) =>
188			payloadIds.includes(item.value.id),
189			);
190			}
191
192			/**
193			* Updates values in response to CREATE FULFILLED action.
194			* - Adds the new item to values, with "fulfilled" status.
195			* - Note: If newly created item has the same id as an existing item, update that item instead.
196			* This should never happen during normal interaction with a REST api.
197			* @param values
198			* @param payload
199			*/
200			function mergeCreatePayload<T extends { id: number }>(
201			values: StateValues<T>,
202			payload: T,
203			): StateValues<T> {
204			if (hasKey(values, payload.id)) {
205			// It doesn't really make sense for the result of a create request to already exist...
206			// But we have to trust the latest response from the server. Update the existing item.
207			return {
208			...values,
209			[payload.id]: {
210			value: payload,
211			status: values[payload.id].pendingCount <= 1 ? "fulfilled" : "pending",
212			pendingCount: decrement(values[payload.id].pendingCount),
213			error: undefined,
214			},
215			};
216			}
217			return {
218			...values,
219			[payload.id]: {
220			value: payload,
221			error: undefined,
222			status: "fulfilled",
223			pendingCount: 0,
224			},
225			};
226			}
227
228			/**
229			* Updates values in response to UPDATE START action.
230			* - Updates metadata for updated item.
231			* - Does nothing if the item does not yet exist.
232			* @param values
233			* @param action
234			*/
235			function mergeUpdateStart<T extends { id: number }>(
236			values: StateValues<T>,
237			action: UpdateStartAction<T>,
238			): StateValues<T> {
239			if (!hasKey(values, action.meta.id)) {
240			// Do not update values. We don't want to create a new value in case the request fails and it doesn't represent anything on the server.
241			// NOTE: if we move to optimistic updates, we should add to values here.
242			return values;
243			}
244			return {
245			...values,
246			[action.meta.id]: {
247			// TODO: if we wanted to do an optimistic update, we could save action.payload.item here.
248			// But we would need some way to reverse it if it failed.
249			...values[action.meta.id],
250			status: "pending",
251			pendingCount: values[action.meta.id].pendingCount + 1,
252			error: undefined,
253			},
254			};
255			}
256			/**
257			* Updates values in response to UPDATE FULFILLED action.
258			* - Updates metadata for updated item and overwrites value with payload.
259			* @param values
260			* @param action
261			*/
262			function mergeUpdateFulfill<T extends { id: number }>(
263			values: StateValues<T>,
264			action: UpdateFulfillAction<T>,
265			): StateValues<T> {
266			if (!hasKey(values, action.meta.id)) {
267			// Even though it didn't exist in local state yet, if the server says it exists, it exists.
268			return {
269			...values,
270			[action.meta.id]: {
271			value: action.payload,
272			status: "fulfilled",
273			pendingCount: 0,
274			error: undefined,
275			},
276			};
277			}
278			return {
279			...values,
280			[action.meta.id]: {
281			value: action.payload,
282			status:
283			values[action.meta.id].pendingCount <= 1 ? "fulfilled" : "pending",
284			pendingCount: decrement(values[action.meta.id].pendingCount),
285			error: undefined,
286			},
287			};
288			}
289			/**
290			* Updates values in response to UPDATE REJECTED action.
291			* - DOES NOT throw error if item does exist, unlike other update mergeUpdate functions.
292			* UPDATE REJECTED action already represents a graceful response to an error.
293			* There is no relevant metadata to update, and nowhere to store the error, so return state as is.
294			* - Otherwise updates metdata for item and overwrites error with payload.f
295			* @param values
296			* @param action
297			*/
298			function mergeUpdateReject<T extends { id: number }>(
299			values: StateValues<T>,
300			action: UpdateRejectAction<T>,
301			): StateValues<T> {
302			if (!hasKey(values, action.meta.id)) {
303			return values;
304			}
305			return {
306			...values,
307			[action.meta.id]: {
308			...values[action.meta.id],
309			status: values[action.meta.id].pendingCount <= 1 ? "rejected" : "pending",
310			pendingCount: decrement(values[action.meta.id].pendingCount),
311			error: action.payload,
312			},
313			};
314			}
315			/**
316			* Updates values in response to DELETE START action.
317			* Updates metadata for item if it exists.
318			*
319			* Does not throw an error if item does not exist, as there are plausible scenarios (eg mupliple queued DELETE requests) that could cause this.
320			* @param values
321			* @param action
322			*/
323			function mergeDeleteStart<T extends { id: number }>(
324			values: StateValues<T>,
325			action: DeleteStartAction,
326			): StateValues<T> {
327			if (!hasKey(values, action.meta.id)) {
328			return values;
329			}
330			return {
331			...values,
332			[action.meta.id]: {
333			...values[action.meta.id],
334			status: "pending",
335			pendingCount: values[action.meta.id].pendingCount + 1,
336			error: undefined,
337			},
338			};
339			}
340			/**
341			* Updates values in response to DELETE FULFILLED action.
342			* Deletes the entire value entry, metadata included. (No effect if entry already doesn't exist.)
343			*
344			* Note: We can safely delete the metadata because any subsequent DELETE or UPDATE requests
345			* on the same item will presumably be REJECTED by the REST api.
346			* DELETE REJECTED and UPDATE REJECTED actions are gracefully handled by the reducer,
347			* even when no metadata is present.
348			* @param values
349			* @param action
350			*/
351			function mergeDeleteFulfill<T extends { id: number }>(
352			values: StateValues<T>,
353			action: DeleteFulfillAction,
354			): StateValues<T> {
355			return deleteProperty(values, action.meta.id);
356			}
357
358			/**
359			* Updates values in response to DELETE REJECTED action.
360			* Updates metadata for item if it exists.
361			*
362			* Does not throw an error if item does not exist, as there are plausible scenarios (eg mupliple queued DELETE requests) that could cause this.
363			* @param values
364			* @param action
365			*/
366			function mergeDeleteReject<T extends { id: number }>(
367			values: StateValues<T>,
368			action: DeleteRejectAction,
369			): StateValues<T> {
370			if (!hasKey(values, action.meta.id)) {
371			return values;
372			}
373			return {
374			...values,
375			[action.meta.id]: {
376			...values[action.meta.id],
377			status: values[action.meta.id].pendingCount <= 1 ? "rejected" : "pending",
378			pendingCount: decrement(values[action.meta.id].pendingCount),
379			error: action.payload,
380			},
381			};
382			}
383
384			/**
385			* This Reducer manages the lifecycle of several http requests related to a single type of resource.
386			* It helps keep a local version of a list of entities in sync with a REST server.
387			*
388			* There are 4 types of request:
389			* - INDEX requests fetch a list of items from the server.
390			* - CREATE requests create add a new item to the list.
391			* - UPDATE requests modify a single existing item in the list.
392			* - DELETE requests remove a single existing item from the list.
393			* Every request has a lifecycle reflected by 3 possible states, resulting in a total of 12 possible reducer Actions.
394			* - START: every request begins with a START action.
395			* - FULFILLED: a successful request dispatches a FULFILLED action, with the response as its payload.
396			* - REJECTED: a request that fails for any reason dispatches a REJECTED action, with the Error as its payload.
397			* Any data sent with the requests is included in the actions (in all three states) as metadata.
398			*
399			* The Reducer's State contains:
400			* - values: a map of items and associated request metadata (specifically UPDATE and DELETE request metadata)
401			* - indexMeta: metadata associated with INDEX requests, as they don't relate to specific items
402			* - createMeta: metadata associated with CREATE requests, as they don't relate to existing items
403			*
404			* The metadata associated with a request includes:
405			* - status: one of four values:
406			* - "initial" if a request has never been made
407			* - "pending" if ANY request is in progress which could modify this resource
408			* - "fulfilled" if the last completed request succeeded and no other request is in progress
409			* - "rejected" if the last completed request failed and no other request is in progress
410			* - pendingCount: stores the number of requests in progress. This helps account for the possibility of multiple requests being started in succession, and means one request could finish and the resource still be considered "pending".
411			* - error: stores the last error recieved from a REJECTED action. Overwritten with undefined if a later request is STARTed or FULFILLED.
412			*
413			* Notes about item values:
414			* - Its possible to include items in the initial state and then not begin any requests, in which case there will be existing values with the "initial" status.
415			* - REJECTED actions do not overwrite the value. Therefore when a request fails and status becomes "rejected", the last good value is still available (though it may become out-of-sync with the REST api).
416			* @param state
417			* @param action
418			*/
419			export function reducer<T extends { id: number }>(
420			state: ResourceState<T>,
421			action: AsyncAction<T>,
422			): ResourceState<T> {
423			switch (action.type) {
424			case ActionTypes.IndexStart:
425			return {
426			...state,
427			indexMeta: {
428			...state.indexMeta,
429			status: "pending",
430			pendingCount: state.indexMeta.pendingCount + 1,
431			error: undefined,
432			},
433			};
434			case ActionTypes.IndexFulfill:
435			return {
436			...state,
437			indexMeta: {
438			...state.indexMeta,
439			status: state.indexMeta.pendingCount <= 1 ? "fulfilled" : "pending",
440			pendingCount: decrement(state.indexMeta.pendingCount),
441			error: undefined,
442			},
443			values: mergeIndexPayload(state.values, action.payload),
444			};
445			case ActionTypes.IndexReject:
446			return {
447			...state,
448			indexMeta: {
449			...state.indexMeta,
450			status: state.indexMeta.pendingCount <= 1 ? "rejected" : "pending",
451			pendingCount: decrement(state.indexMeta.pendingCount),
452			error: action.payload,
453			},
454			};
455			case ActionTypes.CreateStart:
456			// TODO: We could add an optimistic update here.
457			return {
458			...state,
459			createMeta: {
460			...state.createMeta,
461			status: "pending",
462			pendingCount: state.createMeta.pendingCount + 1,
463			error: undefined,
464			},
465			};
466			case ActionTypes.CreateFulfill:
467			return {
468			...state,
469			createMeta: {
470			status: state.createMeta.pendingCount <= 1 ? "fulfilled" : "pending",
471			pendingCount: decrement(state.createMeta.pendingCount),
472			error: undefined,
473			},
474			values: mergeCreatePayload(state.values, action.payload),
475			};
476			case ActionTypes.CreateReject:
477			return {
478			...state,
479			createMeta: {
480			status: state.createMeta.pendingCount <= 1 ? "rejected" : "pending",
481			pendingCount: decrement(state.createMeta.pendingCount),
482			error: action.payload,
483			},
484			};
485			case ActionTypes.UpdateStart:
486			return {
487			...state,
488			values: mergeUpdateStart(state.values, action),
489			};
490			case ActionTypes.UpdateFulfill:
491			return {
492			...state,
493			values: mergeUpdateFulfill(state.values, action),
494			};
495			case ActionTypes.UpdateReject:
496			return {
497			...state,
498			values: mergeUpdateReject(state.values, action),
499			};
500			case ActionTypes.DeleteStart:
501			return {
502			...state,
503			values: mergeDeleteStart(state.values, action),
504			};
505			case ActionTypes.DeleteFulfill:
506			return {
507			...state,
508			values: mergeDeleteFulfill(state.values, action),
509			};
510			case ActionTypes.DeleteReject:
511			return {
512			...state,
513			values: mergeDeleteReject(state.values, action),
514			};
515
516			default:
517			return state;
518			}
519			}
520
521			export default reducer;
522

GCTC-NTGC / TalentCloud

Push — task/explore-skills-ui ( d41a63...af1244 )

indexCrudReducer.ts ➔ reducer C

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