Basic discussions forum framework

Adds the basic structure for the Discussions MFE around which future development
will happen.

src/discussions/comments/data/api.js

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+/* eslint-disable import/prefer-default-export */
+import { getAuthenticatedHttpClient } from '@edx/frontend-platform/auth';
+import { API_BASE_URL } from '../../../data/constants';
+
+export async function getThreadComments(
+  threadId, {
+    commentId, page, pageSize, requestedFields,
+  } = {},
+) {
+  const url = new URL(`${API_BASE_URL}/api/discussion/v1/comments/`);
+  const paramsMap = {
+    thread_id: threadId,
+    comment_id: commentId,
+    page,
+    page_size: pageSize,
+    requested_fields: requestedFields,
+  };
+  Object.keys(paramsMap)
+    .forEach(
+      (param) => {
+        const paramValue = paramsMap[param];
+        if (paramValue) {
+          url.searchParams.append(param, paramValue);
+        }
+      },
+    );
+
+  const { data } = await getAuthenticatedHttpClient()
+    .get(url);
+  return data;
+}

src/discussions/comments/data/index.js

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+export * from './slices';

src/discussions/comments/data/selectors.js

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+/* eslint-disable import/prefer-default-export */
+export const selectTopicComments = topicId => state => state.comments.comments[topicId] || [];
+
+export const courseTopicsStatus = state => state.comments.status;

src/discussions/comments/data/slices.js

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+/* eslint-disable no-param-reassign,import/prefer-default-export */
+import { createSlice } from '@reduxjs/toolkit';
+import { LoadingStatus } from '../../../data/constants';
+
+const commentsSlice = createSlice({
+  name: 'comments',
+  initialState: {
+    status: LoadingStatus.LOADING,
+    page: null,
+    comments: {
+      // Map thread ids to comments
+    },
+    totalPages: null,
+    totalThreads: null,
+  },
+  reducers: {
+    fetchCommentsRequest: (state) => {
+      state.status = LoadingStatus.LOADING;
+    },
+    fetchCommentsSuccess: (state, { payload }) => {
+      const { data, topicId } = payload;
+      state.status = LoadingStatus.LOADED;
+      state.comments[topicId] = data.results;
+      state.page = data.pagination.page;
+      state.totalPages = data.pagination.num_pages;
+      state.totalThreads = data.pagination.count;
+    },
+    fetchCommentsFailed: (state) => {
+      state.status = LoadingStatus.FAILED;
+    },
+    fetchCommentsDenied: (state) => {
+      state.status = LoadingStatus.DENIED;
+    },
+  },
+});
+
+export const {
+  fetchCommentsRequest,
+  fetchCommentsSuccess,
+  fetchCommentsFailed,
+} = commentsSlice.actions;
+
+export const commentsReducer = commentsSlice.reducer;

src/discussions/comments/data/thunks.js

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+/* eslint-disable import/prefer-default-export */
+import { logError } from '@edx/frontend-platform/logging';
+import { getThreadComments } from './api';
+import { fetchCommentsFailed, fetchCommentsRequest, fetchCommentsSuccess } from './slices';
+
+export function fetchTopicComments(topicId) {
+  return async (dispatch) => {
+    try {
+      dispatch(fetchCommentsRequest({ topicId }));
+      const data = await getThreadComments(topicId);
+      dispatch(fetchCommentsSuccess({ topicId, data }));
+    } catch (error) {
+      dispatch(fetchCommentsFailed());
+      logError(error);
+    }
+  };
+}