singleResourceHook.ts ➔ reducer - Code Metrics - Inspection of "Bump @storybook/addons from 6.1.14 to 6.1.15" - GCTC-NTGC/TalentCloud - Measure and Improve Code Quality continuously with Scrutinizer

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created 2021-01-22 15:25 UTC

singleResourceHook.ts ➔ reducer A

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

Complexity

Conditions

Size

Total Lines	32
Code Lines	29

Duplication

Lines	0
Ratio	0 %

Importance

Changes

Metric	Value
eloc	29
dl	0
loc	32
c	0
b	0
f	0
rs	9.184
cc	4

import { Reducer, useCallback, useEffect, useReducer, useRef } from "react";
import {
  FetchError,
  getRequest,
  processJsonResponse,
  putRequest,
} from "../../helpers/httpRequests";
import { decrement, identity } from "../../helpers/queries";
import { Json, ResourceStatus } from "./types";

export interface ResourceState<T> {
  value: T;
  status: ResourceStatus;
  pendingCount: number;
  error: Error | FetchError | undefined;
}

export enum ActionTypes {
  GetStart = "GET_START",
  GetFulfill = "GET_FULFILL",
  GetReject = "GET_REJECT",

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

export type GetStartAction = { type: ActionTypes.GetStart };
export type GetFulfillAction<T> = {
  type: ActionTypes.GetFulfill;
  payload: T;
};
export type GetRejectAction = {
  type: ActionTypes.GetReject;
  payload: Error | FetchError;
};

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

export function initialState<T>(initialValue: T): ResourceState<T> {
  return {
    value: initialValue,
    status: "initial",
    pendingCount: 0,
    error: undefined,
  };
}

export function reducer<T>(
  state: ResourceState<T>,
  action: AsyncAction<T>,
): ResourceState<T> {
  switch (action.type) {
    case ActionTypes.GetStart:
    case ActionTypes.UpdateStart: // TODO: For now GET and UPDATE actions can be treated the same. If we want to add optimistic updates, this can change.
      return {
        value: state.value,
        status: "pending",
        pendingCount: state.pendingCount + 1,
        error: undefined,
      };
    case ActionTypes.GetFulfill:
    case ActionTypes.UpdateFulfill:
      return {
        value: action.payload,
        status: state.pendingCount <= 1 ? "fulfilled" : "pending",
        pendingCount: decrement(state.pendingCount),
        error: undefined,
      };
    case ActionTypes.GetReject:
    case ActionTypes.UpdateReject:
      return {
        value: state.value,
        status: state.pendingCount <= 1 ? "rejected" : "pending",
        pendingCount: decrement(state.pendingCount),
        error: action.payload,
      };
    default:
      return state;
  }
}

function doNothing(): void {
  /* do nothing */
}

export function useResource<T>(
  endpoint: string,
  initialValue: T,
  overrides?: {
    parseResponse?: (response: Json) => T; // Defaults to the identity function.
    skipInitialFetch?: boolean; // Defaults to false. Override if you want to keep the initialValue until refresh is called manually.
    handleError?: (error: Error | FetchError) => void; // In addition to using the error returned by the hook, you may provide a callback called on every new error.
  },
): {
  value: T;
  status: ResourceStatus;
  error: undefined | Error | FetchError;
  update: (newValue: T) => Promise<T>;
  refresh: () => Promise<T>;
} {
  const parseResponse = overrides?.parseResponse ?? identity;
  const doInitialRefresh = overrides?.skipInitialFetch !== true;
  const handleError = overrides?.handleError ?? doNothing;
  const isSubscribed = useRef(true);

  const [state, dispatch] = useReducer<
    Reducer<ResourceState<T>, AsyncAction<T>>
  >(reducer, initialState(initialValue));

  const refresh = useCallback(async (): Promise<T> => {
    dispatch({ type: ActionTypes.GetStart });
    let json: Json;
    try {
      json = await getRequest(endpoint).then(processJsonResponse);
    } catch (error) {
      if (isSubscribed.current) {
        dispatch({
          type: ActionTypes.GetReject,
          payload: error,
        });
        handleError(error);
      }
      throw error;
    }
    const responseValue = parseResponse(json) as T;
    if (isSubscribed.current) {
      dispatch({
        type: ActionTypes.GetFulfill,
        payload: responseValue,
      });
    }
    return responseValue;
  }, [endpoint, parseResponse, handleError]);

  const update = useCallback(
    async (newValue): Promise<T> => {
      dispatch({ type: ActionTypes.UpdateStart, meta: { item: newValue } });
      let json: Json;
      try {
        json = await putRequest(endpoint, newValue).then(processJsonResponse);
      } catch (error) {
        if (isSubscribed.current) {
          dispatch({
            type: ActionTypes.UpdateReject,
            payload: error,
            meta: { item: newValue },
          });
          handleError(error);
        }
        throw error;
      }
      const responseValue = parseResponse(json) as T;
      if (isSubscribed.current) {
        dispatch({
          type: ActionTypes.UpdateFulfill,
          payload: responseValue,
          meta: { item: newValue },
        });
      }
      return responseValue;
    },
    [endpoint, parseResponse, handleError],
  );

  // Despite the usual guidlines, this should only be reconsidered if endpoint changes.
  // Changing doInitialRefresh after the first run (or the refresh function) should not cause this to rerun.
  useEffect(() => {
    if (doInitialRefresh) {
      refresh().catch(doNothing);
    }

    // Unsubscribe from promises when this hook is unmounted.
    return (): void => {
      isSubscribed.current = false;
    };

    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [endpoint]);

  return {
    value: state.value,
    status: state.status,
    error: state.error,
    update,
    refresh,
  };
}

export default useResource;


1			import { Reducer, useCallback, useEffect, useReducer, useRef } from "react";
2			import {
3			FetchError,
4			getRequest,
5			processJsonResponse,
6			putRequest,
7			} from "../../helpers/httpRequests";
8			import { decrement, identity } from "../../helpers/queries";
9			import { Json, ResourceStatus } from "./types";
10
11			export interface ResourceState<T> {
12			value: T;
13			status: ResourceStatus;
14			pendingCount: number;
15			error: Error \| FetchError \| undefined;
16			}
17
18			export enum ActionTypes {
19			GetStart = "GET_START",
20			GetFulfill = "GET_FULFILL",
21			GetReject = "GET_REJECT",
22
23			UpdateStart = "UPDATE_START",
24			UpdateFulfill = "UPDATE_FULFILL",
25			UpdateReject = "UPDATE_REJECT",
26			}
27
28			export type GetStartAction = { type: ActionTypes.GetStart };
29			export type GetFulfillAction<T> = {
30			type: ActionTypes.GetFulfill;
31			payload: T;
32			};
33			export type GetRejectAction = {
34			type: ActionTypes.GetReject;
35			payload: Error \| FetchError;
36			};
37
38			export type UpdateStartAction<T> = {
39			type: ActionTypes.UpdateStart;
40			meta: { item: T };
41			};
42			export type UpdateFulfillAction<T> = {
43			type: ActionTypes.UpdateFulfill;
44			payload: T;
45			meta: { item: T };
46			};
47			export type UpdateRejectAction<T> = {
48			type: ActionTypes.UpdateReject;
49			payload: Error \| FetchError;
50			meta: { item: T };
51			};
52			export type AsyncAction<T> =
53			\| GetStartAction
54			\| GetFulfillAction<T>
55			\| GetRejectAction
56			\| UpdateStartAction<T>
57			\| UpdateFulfillAction<T>
58			\| UpdateRejectAction<T>;
59
60			export function initialState<T>(initialValue: T): ResourceState<T> {
61			return {
62			value: initialValue,
63			status: "initial",
64			pendingCount: 0,
65			error: undefined,
66			};
67			}
68
69			export function reducer<T>(
70			state: ResourceState<T>,
71			action: AsyncAction<T>,
72			): ResourceState<T> {
73			switch (action.type) {
74			case ActionTypes.GetStart:
75			case ActionTypes.UpdateStart: // TODO: For now GET and UPDATE actions can be treated the same. If we want to add optimistic updates, this can change.
76			return {
77			value: state.value,
78			status: "pending",
79			pendingCount: state.pendingCount + 1,
80			error: undefined,
81			};
82			case ActionTypes.GetFulfill:
83			case ActionTypes.UpdateFulfill:
84			return {
85			value: action.payload,
86			status: state.pendingCount <= 1 ? "fulfilled" : "pending",
87			pendingCount: decrement(state.pendingCount),
88			error: undefined,
89			};
90			case ActionTypes.GetReject:
91			case ActionTypes.UpdateReject:
92			return {
93			value: state.value,
94			status: state.pendingCount <= 1 ? "rejected" : "pending",
95			pendingCount: decrement(state.pendingCount),
96			error: action.payload,
97			};
98			default:
99			return state;
100			}
101			}
102
103			function doNothing(): void {
104			/* do nothing */
105			}
106
107			export function useResource<T>(
108			endpoint: string,
109			initialValue: T,
110			overrides?: {
111			parseResponse?: (response: Json) => T; // Defaults to the identity function.
112			skipInitialFetch?: boolean; // Defaults to false. Override if you want to keep the initialValue until refresh is called manually.
113			handleError?: (error: Error \| FetchError) => void; // In addition to using the error returned by the hook, you may provide a callback called on every new error.
114			},
115			): {
116			value: T;
117			status: ResourceStatus;
118			error: undefined \| Error \| FetchError;
119			update: (newValue: T) => Promise<T>;
120			refresh: () => Promise<T>;
121			} {
122			const parseResponse = overrides?.parseResponse ?? identity;
123			const doInitialRefresh = overrides?.skipInitialFetch !== true;
124			const handleError = overrides?.handleError ?? doNothing;
125			const isSubscribed = useRef(true);
126
127			const [state, dispatch] = useReducer<
128			Reducer<ResourceState<T>, AsyncAction<T>>
129			>(reducer, initialState(initialValue));
130
131			const refresh = useCallback(async (): Promise<T> => {
132			dispatch({ type: ActionTypes.GetStart });
133			let json: Json;
134			try {
135			json = await getRequest(endpoint).then(processJsonResponse);
136			} catch (error) {
137			if (isSubscribed.current) {
138			dispatch({
139			type: ActionTypes.GetReject,
140			payload: error,
141			});
142			handleError(error);
143			}
144			throw error;
145			}
146			const responseValue = parseResponse(json) as T;
147			if (isSubscribed.current) {
148			dispatch({
149			type: ActionTypes.GetFulfill,
150			payload: responseValue,
151			});
152			}
153			return responseValue;
154			}, [endpoint, parseResponse, handleError]);
155
156			const update = useCallback(
157			async (newValue): Promise<T> => {
158			dispatch({ type: ActionTypes.UpdateStart, meta: { item: newValue } });
159			let json: Json;
160			try {
161			json = await putRequest(endpoint, newValue).then(processJsonResponse);
162			} catch (error) {
163			if (isSubscribed.current) {
164			dispatch({
165			type: ActionTypes.UpdateReject,
166			payload: error,
167			meta: { item: newValue },
168			});
169			handleError(error);
170			}
171			throw error;
172			}
173			const responseValue = parseResponse(json) as T;
174			if (isSubscribed.current) {
175			dispatch({
176			type: ActionTypes.UpdateFulfill,
177			payload: responseValue,
178			meta: { item: newValue },
179			});
180			}
181			return responseValue;
182			},
183			[endpoint, parseResponse, handleError],
184			);
185
186			// Despite the usual guidlines, this should only be reconsidered if endpoint changes.
187			// Changing doInitialRefresh after the first run (or the refresh function) should not cause this to rerun.
188			useEffect(() => {
189			if (doInitialRefresh) {
190			refresh().catch(doNothing);
191			}
192
193			// Unsubscribe from promises when this hook is unmounted.
194			return (): void => {
195			isSubscribed.current = false;
196			};
197
198			// eslint-disable-next-line react-hooks/exhaustive-deps
199			}, [endpoint]);
200
201			return {
202			value: state.value,
203			status: state.status,
204			error: state.error,
205			update,
206			refresh,
207			};
208			}
209
210			export default useResource;
211

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Push — dev ( b945d5...f9c292 )

singleResourceHook.ts ➔ reducer A

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