14 files changed, 1486 insertions, 633 deletions
diff --git a/src/services/graphql/api.ts b/src/services/graphql/api.ts
index a5be026..009aea4 100644
--- a/src/services/graphql/api.ts
+++ b/src/services/graphql/api.ts
@@ -1,25 +1,312 @@
-import { RequestType, VariablesType } from '@ts/types/app';
 import { settings } from '@utils/config';
-import { GraphQLClient } from 'graphql-request';
+import {
+  articleBySlugQuery,
+  articlesCardQuery,
+  articlesEndCursor,
+  articlesQuery,
+  articlesSlugQuery,
+  totalArticlesQuery,
+} from './articles.query';
+import { sendCommentMutation } from './comments.mutation';
+import { commentsQuery } from './comments.query';
+import { sendMailMutation } from './contact.mutation';
+import {
+  thematicBySlugQuery,
+  thematicsListQuery,
+  thematicsSlugQuery,
+  totalThematicsQuery,
+} from './thematics.query';
+import {
+  topicBySlugQuery,
+  topicsListQuery,
+  topicsSlugQuery,
+  totalTopicsQuery,
+} from './topics.query';
 
-export const getGraphQLClient = (): GraphQLClient => {
-  const apiUrl = settings.api.url;
+export type Mutations = typeof sendMailMutation | typeof sendCommentMutation;
 
-  if (!apiUrl) throw new Error('API URL not defined.');
+export type Queries =
+  | typeof articlesQuery
+  | typeof articleBySlugQuery
+  | typeof articlesCardQuery
+  | typeof articlesEndCursor
+  | typeof articlesSlugQuery
+  | typeof commentsQuery
+  | typeof thematicBySlugQuery
+  | typeof thematicsListQuery
+  | typeof thematicsSlugQuery
+  | typeof topicBySlugQuery
+  | typeof topicsListQuery
+  | typeof topicsSlugQuery
+  | typeof totalArticlesQuery
+  | typeof totalThematicsQuery
+  | typeof totalTopicsQuery;
 
-  return new GraphQLClient(apiUrl);
+export type ArticleResponse<T> = {
+  post: T;
 };
 
-export const fetchApi = async <T extends RequestType>(
-  query: string,
-  variables: VariablesType<T>
-): Promise<T> => {
-  const client = getGraphQLClient();
+export type ArticlesResponse<T> = {
+  posts: T;
+};
+
+export type CommentsResponse<T> = {
+  comments: T;
+};
+
+export type SendCommentResponse<T> = {
+  createComment: T;
+};
+
+export type SendMailResponse<T> = {
+  sendEmail: T;
+};
 
-  try {
-    return await client.request(query, variables);
-  } catch (error) {
-    console.error(error, undefined, 2);
-    process.exit(1);
+export type ThematicResponse<T> = {
+  thematic: T;
+};
+
+export type ThematicsResponse<T> = {
+  thematics: T;
+};
+
+export type TopicResponse<T> = {
+  topic: T;
+};
+
+export type TopicsResponse<T> = {
+  topics: T;
+};
+
+export type PageInfo = {
+  endCursor: string;
+  hasNextPage: boolean;
+  total: number;
+};
+
+export type Edges<T> = {
+  cursor: string;
+  node: T;
+};
+
+export type EdgesResponse<T> = {
+  edges: Edges<T>[];
+  pageInfo: PageInfo;
+};
+
+export type NodeResponse<T> = {
+  node: T;
+};
+
+export type NodesResponse<T> = {
+  nodes: T[];
+};
+
+export type EndCursor = Pick<
+  EdgesResponse<Pick<PageInfo, 'endCursor'>>,
+  'pageInfo'
+>;
+
+export type ResponseMap<T> = {
+  [articleBySlugQuery]: ArticleResponse<T>;
+  [articlesCardQuery]: ArticlesResponse<NodesResponse<T>>;
+  [articlesEndCursor]: ArticlesResponse<EndCursor>;
+  [articlesQuery]: ArticlesResponse<EdgesResponse<T>>;
+  [articlesSlugQuery]: ArticlesResponse<EdgesResponse<T>>;
+  [commentsQuery]: CommentsResponse<NodesResponse<T>>;
+  [sendCommentMutation]: SendCommentResponse<T>;
+  [sendMailMutation]: SendMailResponse<T>;
+  [thematicBySlugQuery]: ThematicResponse<T>;
+  [thematicsListQuery]: ThematicsResponse<EdgesResponse<T>>;
+  [thematicsSlugQuery]: ThematicsResponse<EdgesResponse<T>>;
+  [topicBySlugQuery]: TopicResponse<T>;
+  [topicsListQuery]: TopicsResponse<EdgesResponse<T>>;
+  [topicsSlugQuery]: TopicsResponse<EdgesResponse<T>>;
+  [totalArticlesQuery]: ArticlesResponse<T>;
+  [totalThematicsQuery]: ThematicsResponse<T>;
+  [totalTopicsQuery]: TopicsResponse<T>;
+};
+
+export type GraphQLResponse<
+  T extends keyof ResponseMap<U>,
+  U
+> = ResponseMap<U>[T];
+
+export type BySlugVar = {
+  /**
+   * A slug.
+   */
+  slug: string;
+};
+
+export type EdgesVars = {
+  /**
+   * A cursor.
+   */
+  after?: string;
+  /**
+   * The number of items to return.
+   */
+  first: number;
+  /**
+   * A search query.
+   */
+  search?: string;
+};
+
+export type ByContentIdVar = {
+  /**
+   * An article id.
+   */
+  contentId: number;
+};
+
+export type SearchVar = {
+  /**
+   * A search term.
+   */
+  search?: string;
+};
+
+export type SendCommentVars = {
+  /**
+   * The author name.
+   */
+  author: string;
+  /**
+   * The author e-mail address.
+   */
+  authorEmail: string;
+  /**
+   * The author website.
+   */
+  authorUrl: string;
+  /**
+   * A mutation id.
+   */
+  clientMutationId: string;
+  /**
+   * A post or page id.
+   */
+  commentOn: number;
+  /**
+   * The comment body.
+   */
+  content: string;
+  /**
+   * The comment parent.
+   */
+  parent?: number;
+};
+
+export type SendMailVars = {
+  /**
+   * The mail body.
+   */
+  body: string;
+  /**
+   * A mutation id.
+   */
+  clientMutationId: string;
+  /**
+   * The reply to e-mail address.
+   */
+  replyTo: string;
+  /**
+   * The mail subject.
+   */
+  subject: string;
+};
+
+export type VariablesMap = {
+  [articleBySlugQuery]: BySlugVar;
+  [articlesCardQuery]: EdgesVars;
+  [articlesEndCursor]: EdgesVars;
+  [articlesQuery]: EdgesVars;
+  [articlesSlugQuery]: EdgesVars;
+  [commentsQuery]: ByContentIdVar;
+  [sendCommentMutation]: SendCommentVars;
+  [sendMailMutation]: SendMailVars;
+  [thematicBySlugQuery]: BySlugVar;
+  [thematicsListQuery]: EdgesVars;
+  [thematicsSlugQuery]: EdgesVars;
+  [topicBySlugQuery]: BySlugVar;
+  [topicsListQuery]: EdgesVars;
+  [topicsSlugQuery]: EdgesVars;
+  [totalArticlesQuery]: SearchVar;
+  [totalThematicsQuery]: null;
+  [totalTopicsQuery]: null;
+};
+
+export type FetchAPIProps<T extends Queries | Mutations> = {
+  /**
+   * A GraphQL API URL.
+   */
+  api: string;
+  /**
+   * A GraphQL query.
+   */
+  query: T;
+  /**
+   * (Optional) The query variables.
+   */
+  variables?: VariablesMap[T];
+};
+
+/**
+ * Fetch a GraphQL API.
+ * @param {object} obj - An object.
+ * @param {string} obj.api - A GraphQL API URL.
+ * @param {Queries} obj.query - A GraphQL query.
+ * @param {object} [obj.variables] - The query variables.
+ */
+export async function fetchAPI<T, U extends Queries | Mutations>({
+  api,
+  query,
+  variables,
+}: FetchAPIProps<U>): Promise<GraphQLResponse<U, T>> {
+  const response = await fetch(api, {
+    method: 'POST',
+    headers: {
+      'content-type': 'application/json;charset=UTF-8',
+    },
+    body: JSON.stringify({
+      query,
+      variables,
+    }),
+  });
+
+  type JSONResponse = {
+    data?: GraphQLResponse<U, T>;
+    errors?: Array<{ message: string }>;
+  };
+
+  const { data, errors }: JSONResponse = await response.json();
+
+  if (response.ok) {
+    if (!data) return Promise.reject(new Error(`No data found"`));
+
+    return data;
+  } else {
+    console.error('Failed to fetch API');
+    const error = new Error(
+      errors?.map((e) => e.message).join('\n') ?? 'unknown'
+    );
+    return Promise.reject(error);
+  }
+}
+
+/**
+ * Retrieve the API url from settings.
+ *
+ * @returns {string} The API url.
+ */
+export const getAPIUrl = (): string => {
+  const { url } = settings.api;
+
+  if (!url) {
+    throw new Error('API url is not defined.');
   }
+
+  return url;
 };
diff --git a/src/services/graphql/articles.query.ts b/src/services/graphql/articles.query.ts
new file mode 100644
index 0000000..3e1f575
--- /dev/null
+++ b/src/services/graphql/articles.query.ts
@@ -0,0 +1,191 @@
+/**
+ * Query the full article data using its slug.
+ */
+export const articleBySlugQuery = `query PostBy($slug: ID!) {
+  post(id: $slug, idType: SLUG) {
+    acfPosts {
+      postsInThematic {
+        ... on Thematic {
+          databaseId
+          slug
+          title
+        }
+      }
+      postsInTopic {
+        ... on Topic {
+          databaseId
+          featuredImage {
+            node {
+              altText
+              mediaDetails {
+                height
+                width
+              }
+              sourceUrl
+              title
+            }
+          }
+          slug
+          title
+        }
+      }
+    }
+    author {
+      node {
+        gravatarUrl
+        name
+        url
+      }
+    }
+    commentCount
+    contentParts {
+      afterMore
+      beforeMore
+    }
+    databaseId
+    date
+    featuredImage {
+      node {
+        altText
+        mediaDetails {
+          height
+          width
+        }
+        sourceUrl
+        title
+      }
+    }
+    info {
+      wordsCount
+    }
+    modified
+    seo {
+      metaDesc
+      title
+    }
+    slug
+    title
+  }
+}`;
+
+/**
+ * Query an array of partial articles.
+ */
+export const articlesQuery = `query Articles($after: String = "", $first: Int = 10, $search: String = "") {
+  posts(
+    after: $after
+    first: $first
+    where: {orderby: {field: DATE, order: DESC}, search: $search, status: PUBLISH}
+  ) {
+    edges {
+      cursor
+      node {
+        acfPosts {
+          postsInThematic {
+            ... on Thematic {
+              databaseId
+              slug
+              title
+            }
+          }
+        }
+        commentCount
+        contentParts {
+          beforeMore
+        }
+        databaseId
+        date
+        featuredImage {
+          node {
+            altText
+            mediaDetails {
+              height
+              width
+            }
+            sourceUrl
+            title
+          }
+        }
+        info {
+          wordsCount
+        }
+        modified
+        slug
+        title
+      }
+    }
+    pageInfo {
+      endCursor
+      hasNextPage
+      total
+    }
+  }
+}`;
+
+/**
+ * Query an array of articles with only the minimal data.
+ */
+export const articlesCardQuery = `query ArticlesCard($first: Int = 10) {
+  posts(
+    first: $first
+    where: {orderby: {field: DATE, order: DESC}, status: PUBLISH}
+  ) {
+    nodes {
+      databaseId
+      date
+      featuredImage {
+        node {
+          altText
+          mediaDetails {
+            height
+            width
+          }
+          sourceUrl
+          title
+        }
+      }
+      slug
+      title
+    }
+  }
+}`;
+
+/**
+ * Query an array of articles slug.
+ */
+export const articlesSlugQuery = `query ArticlesSlug($first: Int = 10, $after: String = "") {
+  posts(after: $after, first: $first) {
+    edges {
+      cursor
+      node {
+        slug
+      }
+    }
+    pageInfo {
+      total
+    }
+  }
+}`;
+
+/**
+ * Query the total number of articles.
+ */
+export const totalArticlesQuery = `query PostsTotal($search: String = "") {
+  posts(where: {search: $search}) {
+    pageInfo {
+      total
+    }
+  }
+}`;
+
+/**
+ * Query the end cursor based on the queried posts number.
+ */
+export const articlesEndCursor = `query EndCursorAfter($first: Int) {
+  posts(first: $first) {
+    pageInfo {
+      hasNextPage
+      endCursor
+    }
+  }
+}`;
diff --git a/src/services/graphql/articles.ts b/src/services/graphql/articles.ts
new file mode 100644
index 0000000..27406ac
--- /dev/null
+++ b/src/services/graphql/articles.ts
@@ -0,0 +1,200 @@
+import { Slug, type Article, type ArticleCard } from '@ts/types/app';
+import {
+  type RawArticle,
+  type RawArticlePreview,
+  type TotalItems,
+} from '@ts/types/raw-data';
+import { getAuthorFromRawData } from '@utils/helpers/author';
+import { getImageFromRawData } from '@utils/helpers/images';
+import { getPageLinkFromRawData } from '@utils/helpers/pages';
+import {
+  EdgesResponse,
+  EdgesVars,
+  EndCursor,
+  fetchAPI,
+  getAPIUrl,
+  PageInfo,
+} from './api';
+import {
+  articleBySlugQuery,
+  articlesCardQuery,
+  articlesEndCursor,
+  articlesQuery,
+  articlesSlugQuery,
+  totalArticlesQuery,
+} from './articles.query';
+
+/**
+ * Retrieve the total number of articles.
+ *
+ * @returns {Promise<number>} - The articles total number.
+ */
+export const getTotalArticles = async (search?: string): Promise<number> => {
+  const response = await fetchAPI<TotalItems, typeof totalArticlesQuery>({
+    api: getAPIUrl(),
+    query: totalArticlesQuery,
+    variables: { search },
+  });
+
+  return response.posts.pageInfo.total;
+};
+
+export type GetArticlesReturn = {
+  articles: Article[];
+  pageInfo: PageInfo;
+};
+
+/**
+ * Convert raw data to an Article object.
+ *
+ * @param {RawArticle} data - The page raw data.
+ * @returns {Article} The page data.
+ */
+export const getArticleFromRawData = (data: RawArticle): Article => {
+  const {
+    acfPosts,
+    author,
+    commentCount,
+    contentParts,
+    databaseId,
+    date,
+    featuredImage,
+    info,
+    modified,
+    slug,
+    title,
+    seo,
+  } = data;
+
+  return {
+    content: contentParts.afterMore,
+    id: databaseId,
+    intro: contentParts.beforeMore,
+    meta: {
+      author: author && getAuthorFromRawData(author.node, 'page'),
+      commentsCount: commentCount || 0,
+      cover: featuredImage?.node
+        ? getImageFromRawData(featuredImage.node)
+        : undefined,
+      dates: { publication: date, update: modified },
+      seo: {
+        description: seo?.metaDesc || '',
+        title: seo?.title || '',
+      },
+      thematics: acfPosts.postsInThematic?.map((thematic) =>
+        getPageLinkFromRawData(thematic, 'thematic')
+      ),
+      topics: acfPosts.postsInTopic?.map((topic) =>
+        getPageLinkFromRawData(topic, 'topic')
+      ),
+      wordsCount: info.wordsCount,
+    },
+    slug,
+    title,
+  };
+};
+
+/**
+ * Retrieve the given number of articles from API.
+ *
+ * @param {EdgesVars} props - An object of GraphQL variables.
+ * @returns {Promise<EdgesResponse<RawArticle>>} The articles data.
+ */
+export const getArticles = async (
+  props: EdgesVars
+): Promise<EdgesResponse<RawArticle>> => {
+  const response = await fetchAPI<RawArticle, typeof articlesQuery>({
+    api: getAPIUrl(),
+    query: articlesQuery,
+    variables: { ...props },
+  });
+
+  return response.posts;
+};
+
+/**
+ * Convert a raw article preview to an article card.
+ *
+ * @param {RawArticlePreview} data - A raw article preview.
+ * @returns {ArticleCard} An article card.
+ */
+const getArticleCardFromRawData = (data: RawArticlePreview): ArticleCard => {
+  const { databaseId, date, featuredImage, slug, title } = data;
+
+  return {
+    cover: featuredImage ? getImageFromRawData(featuredImage.node) : undefined,
+    dates: { publication: date },
+    id: databaseId,
+    slug,
+    title,
+  };
+};
+
+/**
+ * Retrieve the given number of article cards from API.
+ *
+ * @param {EdgesVars} obj - An object.
+ * @param {number} obj.first - The number of articles.
+ * @returns {Promise<ArticleCard[]>} - The article cards data.
+ */
+export const getArticlesCard = async ({
+  first,
+}: EdgesVars): Promise<ArticleCard[]> => {
+  const response = await fetchAPI<RawArticlePreview, typeof articlesCardQuery>({
+    api: getAPIUrl(),
+    query: articlesCardQuery,
+    variables: { first },
+  });
+
+  return response.posts.nodes.map((node) => getArticleCardFromRawData(node));
+};
+
+/**
+ * Retrieve an Article object by slug.
+ *
+ * @param {string} slug - The article slug.
+ * @returns {Promise<Article>} The requested article.
+ */
+export const getArticleBySlug = async (slug: string): Promise<Article> => {
+  const response = await fetchAPI<RawArticle, typeof articleBySlugQuery>({
+    api: getAPIUrl(),
+    query: articleBySlugQuery,
+    variables: { slug },
+  });
+
+  return getArticleFromRawData(response.post);
+};
+
+/**
+ * Retrieve all the articles slugs.
+ *
+ * @returns {Promise<string[]>} - An array of articles slugs.
+ */
+export const getAllArticlesSlugs = async (): Promise<string[]> => {
+  const totalArticles = await getTotalArticles();
+  const response = await fetchAPI<Slug, typeof articlesSlugQuery>({
+    api: getAPIUrl(),
+    query: articlesSlugQuery,
+    variables: { first: totalArticles },
+  });
+
+  return response.posts.edges.map((edge) => edge.node.slug);
+};
+
+/**
+ * Retrieve the last cursor.
+ *
+ * @param {EdgesVars} props - An object of GraphQL variables.
+ * @returns {Promise<string>} - The end cursor.
+ */
+export const getArticlesEndCursor = async (
+  props: EdgesVars
+): Promise<string> => {
+  const response = await fetchAPI<EndCursor, typeof articlesEndCursor>({
+    api: getAPIUrl(),
+    query: articlesEndCursor,
+    variables: { ...props },
+  });
+
+  return response.posts.pageInfo.endCursor;
+};
diff --git a/src/services/graphql/comments.mutation.ts b/src/services/graphql/comments.mutation.ts
new file mode 100644
index 0000000..f52c7e9
--- /dev/null
+++ b/src/services/graphql/comments.mutation.ts
@@ -0,0 +1,30 @@
+/**
+ * Send comment mutation.
+ */
+export const sendCommentMutation = `mutation CreateComment(
+  $author: String!
+  $authorEmail: String!
+  $authorUrl: String!
+  $content: String!
+  $parent: ID = null
+  $commentOn: Int!
+  $clientMutationId: String!
+) {
+  createComment(
+    input: {
+      author: $author
+      authorEmail: $authorEmail
+      authorUrl: $authorUrl
+      content: $content
+      parent: $parent
+      commentOn: $commentOn
+      clientMutationId: $clientMutationId
+    }
+  ) {
+    clientMutationId
+    success
+    comment {
+      approved
+    }
+  }
+}`;
diff --git a/src/services/graphql/comments.query.ts b/src/services/graphql/comments.query.ts
new file mode 100644
index 0000000..ef93e89
--- /dev/null
+++ b/src/services/graphql/comments.query.ts
@@ -0,0 +1,21 @@
+/**
+ * Query the comments data by post id.
+ */
+export const commentsQuery = `query CommentsByPostId($contentId: ID!) {
+  comments(where: {contentId: $contentId, order: ASC, orderby: COMMENT_DATE}) {
+    nodes {
+      approved
+      author {
+        node {
+          gravatarUrl
+          name
+          url
+        }
+      }
+      content
+      databaseId
+      date
+      parentDatabaseId
+    }
+  }
+}`;
diff --git a/src/services/graphql/comments.ts b/src/services/graphql/comments.ts
new file mode 100644
index 0000000..28ddfd0
--- /dev/null
+++ b/src/services/graphql/comments.ts
@@ -0,0 +1,102 @@
+import { Comment } from '@ts/types/app';
+import { RawComment } from '@ts/types/raw-data';
+import { getAuthorFromRawData } from '@utils/helpers/author';
+import { fetchAPI, getAPIUrl, SendCommentVars } from './api';
+import { sendCommentMutation } from './comments.mutation';
+import { commentsQuery } from './comments.query';
+
+/**
+ * Create a comments tree with replies.
+ *
+ * @param {Comment[]} comments - A flatten comments list.
+ * @returns {Comment[]} An array of comments with replies.
+ */
+export const buildCommentsTree = (comments: Comment[]): Comment[] => {
+  type CommentsHashTable = {
+    [key: string]: Comment;
+  };
+
+  const hashTable: CommentsHashTable = Object.create(null);
+  const commentsTree: Comment[] = [];
+
+  comments.forEach(
+    (comment) => (hashTable[comment.id] = { ...comment, replies: [] })
+  );
+
+  comments.forEach((comment) => {
+    if (!comment.parentId) {
+      commentsTree.push(hashTable[comment.id]);
+    } else {
+      hashTable[comment.parentId].replies.push(hashTable[comment.id]);
+    }
+  });
+
+  return commentsTree;
+};
+
+/**
+ * Convert a comment from RawComment to Comment type.
+ *
+ * @param {RawComment} comment - A raw comment.
+ * @returns {Comment} A formatted comment.
+ */
+export const getCommentFromRawData = (comment: RawComment): Comment => {
+  const { author, databaseId, date, parentDatabaseId, ...data } = comment;
+
+  return {
+    id: databaseId,
+    meta: {
+      author: getAuthorFromRawData(author.node, 'comment'),
+      date,
+    },
+    parentId: parentDatabaseId,
+    replies: [],
+    ...data,
+  };
+};
+
+/**
+ * Retrieve a comments list by post id.
+ *
+ * @param {number} id - A post id.
+ * @returns {Promise<Comment[]>} The comments list.
+ */
+export const getPostComments = async (id: number): Promise<Comment[]> => {
+  const response = await fetchAPI<RawComment, typeof commentsQuery>({
+    api: getAPIUrl(),
+    query: commentsQuery,
+    variables: { contentId: id },
+  });
+
+  const comments = response.comments.nodes.map((comment) =>
+    getCommentFromRawData(comment)
+  );
+
+  return buildCommentsTree(comments);
+};
+
+export type SentComment = {
+  clientMutationId: string;
+  success: boolean;
+  comment: {
+    approved: boolean;
+  } | null;
+};
+
+/**
+ * Send a comment using GraphQL API.
+ *
+ * @param {SendCommentVars} data - The comment data.
+ * @returns {Promise<SentEmail>} The mutation response.
+ */
+export const sendComment = async (
+  data: SendCommentVars
+): Promise<SentComment> => {
+  const response = await fetchAPI<SentComment, typeof sendCommentMutation>({
+    api: getAPIUrl(),
+    query: sendCommentMutation,
+    variables: { ...data },
+  });
+
+  return response.createComment;
+};
diff --git a/src/services/graphql/contact.mutation.ts b/src/services/graphql/contact.mutation.ts
new file mode 100644
index 0000000..b82fc07
--- /dev/null
+++ b/src/services/graphql/contact.mutation.ts
@@ -0,0 +1,25 @@
+/**
+ * Send mail mutation.
+ */
+export const sendMailMutation = `mutation SendEmail(
+  $subject: String!
+  $body: String!
+  $replyTo: String!
+  $clientMutationId: String!
+) {
+  sendEmail(
+    input: {
+      clientMutationId: $clientMutationId
+      body: $body
+      replyTo: $replyTo
+      subject: $subject
+    }
+  ) {
+    clientMutationId
+    message
+    sent
+    origin
+    replyTo
+    to
+  }
+}`;
diff --git a/src/services/graphql/contact.ts b/src/services/graphql/contact.ts
new file mode 100644
index 0000000..00c6ca2
--- /dev/null
+++ b/src/services/graphql/contact.ts
@@ -0,0 +1,26 @@
+import { fetchAPI, getAPIUrl, SendMailVars } from './api';
+import { sendMailMutation } from './contact.mutation';
+
+export type SentEmail = {
+  clientMutationId: string;
+  message: string;
+  origin: string;
+  replyTo: string;
+  sent: boolean;
+};
+
+/**
+ * Send an email using GraphQL API.
+ *
+ * @param {sendMailVars} data - The mail data.
+ * @returns {Promise<SentEmail>} The mutation response.
+ */
+export const sendMail = async (data: SendMailVars): Promise<SentEmail> => {
+  const response = await fetchAPI<SentEmail, typeof sendMailMutation>({
+    api: getAPIUrl(),
+    query: sendMailMutation,
+    variables: { ...data },
+  });
+
+  return response.sendEmail;
+};
diff --git a/src/services/graphql/mutations.ts b/src/services/graphql/mutations.ts
deleted file mode 100644
index c697835..0000000
--- a/src/services/graphql/mutations.ts
+++ /dev/null
@@ -1,82 +0,0 @@
-import { CommentData, CreateComment, CreatedComment } from '@ts/types/comments';
-import { ContactData, SendEmail } from '@ts/types/contact';
-import { gql } from 'graphql-request';
-import { fetchApi } from './api';
-
-//==============================================================================
-// Comment mutation
-//==============================================================================
-
-export const createComment = async (
-  data: CommentData
-): Promise<CreatedComment> => {
-  const mutation = gql`
-    mutation CreateComment(
-      $author: String!
-      $authorEmail: String!
-      $authorUrl: String!
-      $content: String!
-      $parent: ID!
-      $commentOn: Int!
-      $mutationId: String!
-    ) {
-      createComment(
-        input: {
-          author: $author
-          authorEmail: $authorEmail
-          authorUrl: $authorUrl
-          content: $content
-          parent: $parent
-          commentOn: $commentOn
-          clientMutationId: $mutationId
-        }
-      ) {
-        clientMutationId
-        success
-        comment {
-          approved
-        }
-      }
-    }
-  `;
-
-  const variables = { ...data };
-  const response = await fetchApi<CreateComment>(mutation, variables);
-
-  return response.createComment;
-};
-
-//==============================================================================
-// Contact mutation
-//==============================================================================
-
-export const sendMail = async (data: ContactData) => {
-  const mutation = gql`
-    mutation SendEmail(
-      $subject: String!
-      $body: String!
-      $replyTo: String!
-      $mutationId: String!
-    ) {
-      sendEmail(
-        input: {
-          clientMutationId: $mutationId
-          body: $body
-          replyTo: $replyTo
-          subject: $subject
-        }
-      ) {
-        clientMutationId
-        message
-        sent
-        origin
-        replyTo
-        to
-      }
-    }
-  `;
-
-  const variables = { ...data };
-  const response = await fetchApi<SendEmail>(mutation, variables);
-  return response.sendEmail;
-};
diff --git a/src/services/graphql/queries.ts b/src/services/graphql/queries.ts
deleted file mode 100644
index 9caf62b..0000000
--- a/src/services/graphql/queries.ts
+++ /dev/null
@@ -1,535 +0,0 @@
-import { Slug } from '@ts/types/app';
-import { Article, PostBy, TotalArticles } from '@ts/types/articles';
-import {
-  AllPostsSlug,
-  LastPostCursor,
-  PostsList,
-  RawPostsList,
-} from '@ts/types/blog';
-import { Comment, CommentsByPostId } from '@ts/types/comments';
-import {
-  AllTopics,
-  AllTopicsSlug,
-  AllThematics,
-  AllThematicsSlug,
-  Topic,
-  TopicBy,
-  TopicPreview,
-  Thematic,
-  ThematicBy,
-  ThematicPreview,
-} from '@ts/types/taxonomies';
-import {
-  getFormattedPost,
-  getFormattedPostPreview,
-  getFormattedTopic,
-  getFormattedThematic,
-  getFormattedComments,
-  buildCommentsTree,
-} from '@utils/helpers/format';
-import { gql } from 'graphql-request';
-import { fetchApi } from './api';
-
-//==============================================================================
-// Posts list queries
-//==============================================================================
-
-export const getPostsTotal = async (): Promise<number> => {
-  const query = gql`
-    query PostsTotal {
-      posts {
-        pageInfo {
-          total
-        }
-      }
-    }
-  `;
-
-  const response = await fetchApi<TotalArticles>(query, null);
-  return response.posts.pageInfo.total;
-};
-
-export const getPublishedPosts = async ({
-  first = 10,
-  after = '',
-  searchQuery = '',
-}: {
-  first: number;
-  after?: string;
-  searchQuery?: string;
-}): Promise<PostsList> => {
-  const query = gql`
-    query AllPublishedPosts($first: Int, $after: String, $searchQuery: String) {
-      posts(
-        after: $after
-        first: $first
-        where: {
-          status: PUBLISH
-          orderby: { field: DATE, order: DESC }
-          search: $searchQuery
-        }
-      ) {
-        edges {
-          cursor
-          node {
-            acfPosts {
-              postsInTopic {
-                ... on Topic {
-                  databaseId
-                  featuredImage {
-                    node {
-                      altText
-                      sourceUrl
-                      title
-                    }
-                  }
-                  id
-                  slug
-                  title
-                }
-              }
-              postsInThematic {
-                ... on Thematic {
-                  databaseId
-                  id
-                  slug
-                  title
-                }
-              }
-            }
-            commentCount
-            contentParts {
-              beforeMore
-            }
-            date
-            featuredImage {
-              node {
-                altText
-                sourceUrl
-                title
-              }
-            }
-            id
-            info {
-              readingTime
-              wordsCount
-            }
-            databaseId
-            modified
-            slug
-            title
-          }
-        }
-        pageInfo {
-          endCursor
-          hasNextPage
-          total
-        }
-      }
-    }
-  `;
-
-  const variables = { first, after, searchQuery };
-  const response = await fetchApi<RawPostsList>(query, variables);
-  const formattedPosts = response.posts.edges.map((post) => {
-    return getFormattedPostPreview(post.node);
-  });
-
-  return {
-    posts: formattedPosts,
-    pageInfo: response.posts.pageInfo,
-  };
-};
-
-export const getAllPostsSlug = async (): Promise<Slug[]> => {
-  // 10 000 is an arbitrary number that I use for small websites.
-  const query = gql`
-    query AllPostsSlug {
-      posts(first: 10000) {
-        nodes {
-          slug
-        }
-      }
-    }
-  `;
-
-  const response = await fetchApi<AllPostsSlug>(query, null);
-  return response.posts.nodes;
-};
-
-//==============================================================================
-// Single Post query
-//==============================================================================
-
-export const getPostBySlug = async (slug: string): Promise<Article> => {
-  const query = gql`
-    query PostBySlug($slug: ID!) {
-      post(id: $slug, idType: SLUG) {
-        acfPosts {
-          postsInTopic {
-            ... on Topic {
-              id
-              featuredImage {
-                node {
-                  altText
-                  sourceUrl
-                  title
-                }
-              }
-              slug
-              title
-            }
-          }
-          postsInThematic {
-            ... on Thematic {
-              id
-              slug
-              title
-            }
-          }
-        }
-        author {
-          node {
-            firstName
-            lastName
-            name
-          }
-        }
-        commentCount
-        contentParts {
-          afterMore
-          beforeMore
-        }
-        databaseId
-        date
-        featuredImage {
-          node {
-            altText
-            sourceUrl
-            title
-          }
-        }
-        id
-        info {
-          readingTime
-          wordsCount
-        }
-        modified
-        seo {
-          metaDesc
-          title
-        }
-        title
-      }
-    }
-  `;
-  const variables = { slug };
-  const response = await fetchApi<PostBy>(query, variables);
-
-  return getFormattedPost(response.post);
-};
-
-//==============================================================================
-// Comments query
-//==============================================================================
-
-export const getCommentsByPostId = async (id: number): Promise<Comment[]> => {
-  const query = gql`
-    query PostComments($id: ID!) {
-      comments(where: { contentId: $id, order: ASC, orderby: COMMENT_DATE }) {
-        nodes {
-          approved
-          author {
-            node {
-              databaseId
-              gravatarUrl
-              name
-              url
-            }
-          }
-          content
-          databaseId
-          date
-          parentDatabaseId
-        }
-      }
-    }
-  `;
-
-  const variables = { id };
-  const response = await fetchApi<CommentsByPostId>(query, variables);
-  const formattedComments = getFormattedComments(response.comments.nodes);
-
-  return buildCommentsTree(formattedComments);
-};
-
-//==============================================================================
-// Topic query
-//==============================================================================
-
-export const getTopicBySlug = async (slug: string): Promise<Topic> => {
-  const query = gql`
-    query TopicBySlug($slug: ID!) {
-      topic(id: $slug, idType: SLUG) {
-        acfTopics {
-          officialWebsite
-          postsInTopic {
-            ... on Post {
-              acfPosts {
-                postsInTopic {
-                  ... on Topic {
-                    databaseId
-                    featuredImage {
-                      node {
-                        altText
-                        sourceUrl
-                        title
-                      }
-                    }
-                    id
-                    slug
-                    title
-                  }
-                }
-                postsInThematic {
-                  ... on Thematic {
-                    databaseId
-                    id
-                    slug
-                    title
-                  }
-                }
-              }
-              id
-              info {
-                readingTime
-                wordsCount
-              }
-              commentCount
-              contentParts {
-                beforeMore
-              }
-              databaseId
-              date
-              featuredImage {
-                node {
-                  altText
-                  sourceUrl
-                  title
-                }
-              }
-              modified
-              slug
-              title
-            }
-          }
-        }
-        contentParts {
-          afterMore
-          beforeMore
-        }
-        databaseId
-        date
-        featuredImage {
-          node {
-            altText
-            sourceUrl
-            title
-          }
-        }
-        id
-        info {
-          readingTime
-          wordsCount
-        }
-        modified
-        seo {
-          metaDesc
-          title
-        }
-        title
-      }
-    }
-  `;
-  const variables = { slug };
-  const response = await fetchApi<TopicBy>(query, variables);
-
-  return getFormattedTopic(response.topic);
-};
-
-export const getAllTopicsSlug = async (): Promise<Slug[]> => {
-  // 10 000 is an arbitrary number that I use for small websites.
-  const query = gql`
-    query AllTopicsSlug {
-      topics(first: 10000) {
-        nodes {
-          slug
-        }
-      }
-    }
-  `;
-  const response = await fetchApi<AllTopicsSlug>(query, null);
-  return response.topics.nodes;
-};
-
-export const getAllTopics = async (): Promise<TopicPreview[]> => {
-  // 10 000 is an arbitrary number that I use for small websites.
-  const query = gql`
-    query AllTopics {
-      topics(first: 10000, where: { orderby: { field: TITLE, order: ASC } }) {
-        nodes {
-          databaseId
-          slug
-          title
-        }
-      }
-    }
-  `;
-
-  const response = await fetchApi<AllTopics>(query, null);
-  return response.topics.nodes;
-};
-
-//==============================================================================
-// Thematic query
-//==============================================================================
-
-export const getThematicBySlug = async (slug: string): Promise<Thematic> => {
-  const query = gql`
-    query ThematicBySlug($slug: ID!) {
-      thematic(id: $slug, idType: SLUG) {
-        acfThematics {
-          postsInThematic {
-            ... on Post {
-              acfPosts {
-                postsInTopic {
-                  ... on Topic {
-                    databaseId
-                    featuredImage {
-                      node {
-                        altText
-                        sourceUrl
-                        title
-                      }
-                    }
-                    id
-                    slug
-                    title
-                  }
-                }
-                postsInThematic {
-                  ... on Thematic {
-                    databaseId
-                    id
-                    slug
-                    title
-                  }
-                }
-              }
-              id
-              info {
-                readingTime
-                wordsCount
-              }
-              commentCount
-              contentParts {
-                beforeMore
-              }
-              databaseId
-              date
-              featuredImage {
-                node {
-                  altText
-                  sourceUrl
-                  title
-                }
-              }
-              modified
-              slug
-              title
-            }
-          }
-        }
-        contentParts {
-          afterMore
-          beforeMore
-        }
-        databaseId
-        date
-        id
-        info {
-          readingTime
-          wordsCount
-        }
-        modified
-        seo {
-          metaDesc
-          title
-        }
-        title
-      }
-    }
-  `;
-  const variables = { slug };
-  const response = await fetchApi<ThematicBy>(query, variables);
-
-  return getFormattedThematic(response.thematic);
-};
-
-export const getAllThematicsSlug = async (): Promise<Slug[]> => {
-  // 10 000 is an arbitrary number that I use for small websites.
-  const query = gql`
-    query AllThematicsSlug {
-      thematics(first: 10000) {
-        nodes {
-          slug
-        }
-      }
-    }
-  `;
-  const response = await fetchApi<AllThematicsSlug>(query, null);
-  return response.thematics.nodes;
-};
-
-export const getAllThematics = async (): Promise<ThematicPreview[]> => {
-  // 10 000 is an arbitrary number that I use for small websites.
-  const query = gql`
-    query AllThematics {
-      thematics(
-        first: 10000
-        where: { orderby: { field: TITLE, order: ASC } }
-      ) {
-        nodes {
-          databaseId
-          slug
-          title
-        }
-      }
-    }
-  `;
-
-  const response = await fetchApi<AllThematics>(query, null);
-  return response.thematics.nodes;
-};
-
-export const getEndCursor = async ({
-  first = 10,
-}: {
-  first: number;
-}): Promise<string> => {
-  const query = gql`
-    query EndCursorAfter($first: Int) {
-      posts(first: $first) {
-        pageInfo {
-          hasNextPage
-          endCursor
-        }
-      }
-    }
-  `;
-
-  const variables = { first };
-  const response = await fetchApi<LastPostCursor>(query, variables);
-
-  return response.posts.pageInfo.endCursor;
-};
diff --git a/src/services/graphql/thematics.query.ts b/src/services/graphql/thematics.query.ts
new file mode 100644
index 0000000..5a82133
--- /dev/null
+++ b/src/services/graphql/thematics.query.ts
@@ -0,0 +1,125 @@
+/**
+ * Query the full thematic data using its slug.
+ */
+export const thematicBySlugQuery = `query ThematicBy($slug: ID!) {
+  thematic(id: $slug, idType: SLUG) {
+    acfThematics {
+      postsInThematic {
+        ... on Post {
+          acfPosts {
+            postsInTopic {
+              ... on Topic {
+                databaseId
+                slug
+                title
+              }
+            }
+          }
+          commentCount
+          contentParts {
+            beforeMore
+          }
+          databaseId
+          date
+          featuredImage {
+            node {
+              altText
+              mediaDetails {
+                height
+                width
+              }
+              sourceUrl
+              title
+            }
+          }
+          info {
+            wordsCount
+          }
+          modified
+          slug
+          title
+        }
+      }
+    }
+    contentParts {
+      afterMore
+      beforeMore
+    }
+    databaseId
+    date
+    featuredImage {
+      node {
+        altText
+        mediaDetails {
+          height
+          width
+        }
+        sourceUrl
+        title
+      }
+    }
+    info {
+      wordsCount
+    }
+    modified
+    seo {
+      metaDesc
+      title
+    }
+    slug
+    title
+  }
+}`;
+
+/**
+ * Query an array of partial thematics.
+ */
+export const thematicsListQuery = `query ThematicsList($after: String = "", $first: Int = 10) {
+  thematics(
+    after: $after
+    first: $first
+    where: {orderby: {field: TITLE, order: ASC}, status: PUBLISH}
+  ) {
+    edges {
+      cursor
+      node {
+        databaseId
+        slug
+        title
+      }
+    }
+    pageInfo {
+      endCursor
+      hasNextPage
+      total
+    }
+  }
+}`;
+
+/**
+ * Query an array of thematics slug.
+ */
+export const thematicsSlugQuery = `query ThematicsSlug($first: Int = 10, $after: String = "") {
+  thematics(after: $after, first: $first) {
+    edges {
+      cursor
+      node {
+        slug
+      }
+    }
+    pageInfo {
+      total
+    }
+  }
+}`;
+
+/**
+ * Query the total number of thematics.
+ */
+export const totalThematicsQuery = `query ThematicsTotal {
+  thematics {
+    pageInfo {
+      total
+    }
+  }
+}`;
diff --git a/src/services/graphql/thematics.ts b/src/services/graphql/thematics.ts
new file mode 100644
index 0000000..4dc69e7
--- /dev/null
+++ b/src/services/graphql/thematics.ts
@@ -0,0 +1,162 @@
+import { PageLink, Slug, Thematic } from '@ts/types/app';
+import {
+  RawArticle,
+  RawThematic,
+  RawThematicPreview,
+  TotalItems,
+} from '@ts/types/raw-data';
+import { getImageFromRawData } from '@utils/helpers/images';
+import { getPageLinkFromRawData } from '@utils/helpers/pages';
+import { EdgesResponse, EdgesVars, fetchAPI, getAPIUrl } from './api';
+import { getArticleFromRawData } from './articles';
+import {
+  thematicBySlugQuery,
+  thematicsListQuery,
+  thematicsSlugQuery,
+  totalThematicsQuery,
+} from './thematics.query';
+
+/**
+ * Retrieve the total number of thematics.
+ *
+ * @returns {Promise<number>} - The thematics total number.
+ */
+export const getTotalThematics = async (): Promise<number> => {
+  const response = await fetchAPI<TotalItems, typeof totalThematicsQuery>({
+    api: getAPIUrl(),
+    query: totalThematicsQuery,
+  });
+
+  return response.thematics.pageInfo.total;
+};
+
+/**
+ * Retrieve the given number of thematics from API.
+ *
+ * @param {EdgesVars} props - An object of GraphQL variables.
+ * @returns {Promise<EdgesResponse<RawThematicPreview>>} The thematics data.
+ */
+export const getThematicsPreview = async (
+  props: EdgesVars
+): Promise<EdgesResponse<RawThematicPreview>> => {
+  const response = await fetchAPI<
+    RawThematicPreview,
+    typeof thematicsListQuery
+  >({ api: getAPIUrl(), query: thematicsListQuery, variables: props });
+
+  return response.thematics;
+};
+
+/**
+ * Convert raw data to an Thematic object.
+ *
+ * @param {RawThematic} data - The page raw data.
+ * @returns {Thematic} The page data.
+ */
+export const getThematicFromRawData = (data: RawThematic): Thematic => {
+  const {
+    acfThematics,
+    contentParts,
+    databaseId,
+    date,
+    featuredImage,
+    info,
+    modified,
+    slug,
+    title,
+    seo,
+  } = data;
+
+  /**
+   * Retrieve an array of related topics.
+   *
+   * @param posts - The thematic posts.
+   * @returns {PageLink[]} An array of topics links.
+   */
+  const getRelatedTopics = (posts: RawArticle[]): PageLink[] => {
+    const topics: PageLink[] = [];
+
+    posts.forEach((post) => {
+      if (post.acfPosts.postsInTopic) {
+        post.acfPosts.postsInTopic.forEach((topic) =>
+          topics.push(getPageLinkFromRawData(topic, 'topic'))
+        );
+      }
+    });
+
+    const topicsIds = topics.map((topic) => topic.id);
+    const uniqueTopics = topics.filter(
+      ({ id }, index) => !topicsIds.includes(id, index + 1)
+    );
+    const sortTopicByName = (a: PageLink, b: PageLink) => {
+      var nameA = a.name.toUpperCase(); // ignore upper and lowercase
+      var nameB = b.name.toUpperCase(); // ignore upper and lowercase
+      if (nameA < nameB) {
+        return -1;
+      }
+      if (nameA > nameB) {
+        return 1;
+      }
+
+      // names must be equal
+      return 0;
+    };
+
+    return uniqueTopics.sort(sortTopicByName);
+  };
+
+  return {
+    content: contentParts.afterMore,
+    id: databaseId,
+    intro: contentParts.beforeMore,
+    meta: {
+      articles: acfThematics.postsInThematic.map((post) =>
+        getArticleFromRawData(post)
+      ),
+      cover: featuredImage?.node
+        ? getImageFromRawData(featuredImage.node)
+        : undefined,
+      dates: { publication: date, update: modified },
+      seo: {
+        description: seo?.metaDesc || '',
+        title: seo?.title || '',
+      },
+      topics: getRelatedTopics(acfThematics.postsInThematic),
+      wordsCount: info.wordsCount,
+    },
+    slug,
+    title,
+  };
+};
+
+/**
+ * Retrieve a Thematic object by slug.
+ *
+ * @param {string} slug - The thematic slug.
+ * @returns {Promise<Article>} The requested thematic.
+ */
+export const getThematicBySlug = async (slug: string): Promise<Thematic> => {
+  const response = await fetchAPI<RawThematic, typeof thematicBySlugQuery>({
+    api: getAPIUrl(),
+    query: thematicBySlugQuery,
+    variables: { slug },
+  });
+
+  return getThematicFromRawData(response.thematic);
+};
+
+/**
+ * Retrieve all the thematics slugs.
+ *
+ * @returns {Promise<string[]>} - An array of thematics slugs.
+ */
+export const getAllThematicsSlugs = async (): Promise<string[]> => {
+  const totalThematics = await getTotalThematics();
+  const response = await fetchAPI<Slug, typeof thematicsSlugQuery>({
+    api: getAPIUrl(),
+    query: thematicsSlugQuery,
+    variables: { first: totalThematics },
+  });
+
+  return response.thematics.edges.map((edge) => edge.node.slug);
+};
diff --git a/src/services/graphql/topics.query.ts b/src/services/graphql/topics.query.ts
new file mode 100644
index 0000000..57b2569
--- /dev/null
+++ b/src/services/graphql/topics.query.ts
@@ -0,0 +1,137 @@
+/**
+ * Query the full topic data using its slug.
+ */
+export const topicBySlugQuery = `query TopicBy($slug: ID!) {
+  topic(id: $slug, idType: SLUG) {
+    acfTopics {
+      officialWebsite
+      postsInTopic {
+        ... on Post {
+          acfPosts {
+            postsInThematic {
+              ... on Thematic {
+                databaseId
+                slug
+                title
+              }
+            }
+          }
+          commentCount
+          contentParts {
+            beforeMore
+          }
+          databaseId
+          date
+          featuredImage {
+            node {
+              altText
+              mediaDetails {
+                height
+                width
+              }
+              sourceUrl
+              title
+            }
+          }
+          info {
+            wordsCount
+          }
+          modified
+          slug
+          title
+        }
+      }
+    }
+    contentParts {
+      afterMore
+      beforeMore
+    }
+    databaseId
+    date
+    featuredImage {
+      node {
+        altText
+        mediaDetails {
+          height
+          width
+        }
+        sourceUrl
+        title
+      }
+    }
+    info {
+      wordsCount
+    }
+    modified
+    seo {
+      metaDesc
+      title
+    }
+    slug
+    title
+  }
+}`;
+
+/**
+ * Query an array of partial topics.
+ */
+export const topicsListQuery = `query TopicsList($after: String = "", $first: Int = 10) {
+  topics(
+    after: $after
+    first: $first
+    where: {orderby: {field: TITLE, order: ASC}, status: PUBLISH}
+  ) {
+    edges {
+      cursor
+      node {
+        databaseId
+        featuredImage {
+          node {
+            altText
+            mediaDetails {
+              height
+              width
+            }
+            sourceUrl
+            title
+          }
+        }
+        slug
+        title
+      }
+    }
+    pageInfo {
+      endCursor
+      hasNextPage
+      total
+    }
+  }
+}`;
+
+/**
+ * Query an array of topics slug.
+ */
+export const topicsSlugQuery = `query TopicsSlug($first: Int = 10, $after: String = "") {
+  topics(after: $after, first: $first) {
+    edges {
+      cursor
+      node {
+        slug
+      }
+    }
+    pageInfo {
+      total
+    }
+  }
+}`;
+
+/**
+ * Query the total number of topics.
+ */
+export const totalTopicsQuery = `query TopicsTotal {
+  topics {
+    pageInfo {
+      total
+    }
+  }
+}`;
diff --git a/src/services/graphql/topics.ts b/src/services/graphql/topics.ts
new file mode 100644
index 0000000..0b1971b
--- /dev/null
+++ b/src/services/graphql/topics.ts
@@ -0,0 +1,164 @@
+import { PageLink, Slug, Topic } from '@ts/types/app';
+import {
+  RawArticle,
+  RawTopic,
+  RawTopicPreview,
+  TotalItems,
+} from '@ts/types/raw-data';
+import { getImageFromRawData } from '@utils/helpers/images';
+import { getPageLinkFromRawData } from '@utils/helpers/pages';
+import { EdgesResponse, EdgesVars, fetchAPI, getAPIUrl } from './api';
+import { getArticleFromRawData } from './articles';
+import {
+  topicBySlugQuery,
+  topicsListQuery,
+  topicsSlugQuery,
+  totalTopicsQuery,
+} from './topics.query';
+
+/**
+ * Retrieve the total number of topics.
+ *
+ * @returns {Promise<number>} - The topics total number.
+ */
+export const getTotalTopics = async (): Promise<number> => {
+  const response = await fetchAPI<TotalItems, typeof totalTopicsQuery>({
+    api: getAPIUrl(),
+    query: totalTopicsQuery,
+  });
+
+  return response.topics.pageInfo.total;
+};
+
+/**
+ * Retrieve the given number of topics from API.
+ *
+ * @param {EdgesVars} props - An object of GraphQL variables.
+ * @returns {Promise<EdgesResponse<RawTopicPreview>>} The topics data.
+ */
+export const getTopicsPreview = async (
+  props: EdgesVars
+): Promise<EdgesResponse<RawTopicPreview>> => {
+  const response = await fetchAPI<RawTopicPreview, typeof topicsListQuery>({
+    api: getAPIUrl(),
+    query: topicsListQuery,
+    variables: props,
+  });
+
+  return response.topics;
+};
+
+/**
+ * Convert raw data to a Topic object.
+ *
+ * @param {RawTopic} data - The page raw data.
+ * @returns {Topic} The page data.
+ */
+export const getTopicFromRawData = (data: RawTopic): Topic => {
+  const {
+    acfTopics,
+    contentParts,
+    databaseId,
+    date,
+    featuredImage,
+    info,
+    modified,
+    slug,
+    title,
+    seo,
+  } = data;
+
+  /**
+   * Retrieve an array of related topics.
+   *
+   * @param posts - The topic posts.
+   * @returns {PageLink[]} An array of topics links.
+   */
+  const getRelatedThematics = (posts: RawArticle[]): PageLink[] => {
+    const thematics: PageLink[] = [];
+
+    posts.forEach((post) => {
+      if (post.acfPosts.postsInThematic) {
+        post.acfPosts.postsInThematic.forEach((thematic) =>
+          thematics.push(getPageLinkFromRawData(thematic, 'thematic'))
+        );
+      }
+    });
+
+    const thematicsIds = thematics.map((thematic) => thematic.id);
+    const uniqueThematics = thematics.filter(
+      ({ id }, index) => !thematicsIds.includes(id, index + 1)
+    );
+    const sortThematicByName = (a: PageLink, b: PageLink) => {
+      var nameA = a.name.toUpperCase(); // ignore upper and lowercase
+      var nameB = b.name.toUpperCase(); // ignore upper and lowercase
+      if (nameA < nameB) {
+        return -1;
+      }
+      if (nameA > nameB) {
+        return 1;
+      }
+
+      // names must be equal
+      return 0;
+    };
+
+    return uniqueThematics.sort(sortThematicByName);
+  };
+
+  return {
+    content: contentParts.afterMore,
+    id: databaseId,
+    intro: contentParts.beforeMore,
+    meta: {
+      articles: acfTopics.postsInTopic.map((post) =>
+        getArticleFromRawData(post)
+      ),
+      cover: featuredImage?.node
+        ? getImageFromRawData(featuredImage.node)
+        : undefined,
+      dates: { publication: date, update: modified },
+      website: acfTopics.officialWebsite,
+      seo: {
+        description: seo?.metaDesc || '',
+        title: seo?.title || '',
+      },
+      thematics: getRelatedThematics(acfTopics.postsInTopic),
+      wordsCount: info.wordsCount,
+    },
+    slug,
+    title,
+  };
+};
+
+/**
+ * Retrieve a Topic object by slug.
+ *
+ * @param {string} slug - The topic slug.
+ * @returns {Promise<Article>} The requested topic.
+ */
+export const getTopicBySlug = async (slug: string): Promise<Topic> => {
+  const response = await fetchAPI<RawTopic, typeof topicBySlugQuery>({
+    api: getAPIUrl(),
+    query: topicBySlugQuery,
+    variables: { slug },
+  });
+
+  return getTopicFromRawData(response.topic);
+};
+
+/**
+ * Retrieve all the topics slugs.
+ *
+ * @returns {Promise<string[]>} - An array of topics slugs.
+ */
+export const getAllTopicsSlugs = async (): Promise<string[]> => {
+  const totalTopics = await getTotalTopics();
+  const response = await fetchAPI<Slug, typeof topicsSlugQuery>({
+    api: getAPIUrl(),
+    query: topicsSlugQuery,
+    variables: { first: totalTopics },
+  });
+
+  return response.topics.edges.map((edge) => edge.node.slug);
+};