refactor: started work on porting socket methods to write API [breaking]

The following socket calls have been removed:

* `posts.getRawPost`
* `posts.getPostSummaryByPid`

Two new Write API routes have been added:

- `GET /api/v3/posts/:pid/raw`
- `GET /api/v3/posts/:pid/summary`

src/api/posts.js

@@ -8,6 +8,7 @@ const user = require('../user');
 const posts = require('../posts');
 const topics = require('../topics');
 const groups = require('../groups');
+const plugins = require('../plugins');
 const meta = require('../meta');
 const events = require('../events');
 const privileges = require('../privileges');
@@ -23,17 +24,15 @@ postsAPI.get = async function (caller, data) {
 		posts.getPostData(data.pid),
 		posts.hasVoted(data.pid, caller.uid),
 	]);
-	if (!post) {
-		return null;
-	}
-	Object.assign(post, voted);
-
 	const userPrivilege = userPrivileges[0];
-	if (!userPrivilege.read || !userPrivilege['topics:read']) {
+
+	if (!post || !userPrivilege.read || !userPrivilege['topics:read']) {
 		return null;
 	}
 
+	Object.assign(post, voted);
 	post.ip = userPrivilege.isAdminOrMod ? post.ip : undefined;
+
 	const selfPost = caller.uid && caller.uid === parseInt(post.uid, 10);
 	if (post.deleted && !(userPrivilege.isAdminOrMod || selfPost)) {
 		post.content = '[[topic:post_is_deleted]]';
@@ -42,6 +41,36 @@ postsAPI.get = async function (caller, data) {
 	return post;
 };
 
+postsAPI.getSummary = async (caller, { pid }) => {
+	const tid = await posts.getPostField(pid, 'tid');
+	const topicPrivileges = await privileges.topics.get(tid, caller.uid);
+	if (!topicPrivileges.read || !topicPrivileges['topics:read']) {
+		return null;
+	}
+
+	const postsData = await posts.getPostSummaryByPids([pid], caller.uid, { stripTags: false });
+	posts.modifyPostByPrivilege(postsData[0], topicPrivileges);
+	return postsData[0];
+};
+
+postsAPI.getRaw = async (caller, { pid }) => {
+	const userPrivileges = await privileges.posts.get([pid], caller.uid);
+	const userPrivilege = userPrivileges[0];
+	if (!userPrivilege['topics:read']) {
+		return null;
+	}
+
+	const postData = await posts.getPostFields(pid, ['content', 'deleted']);
+	const selfPost = caller.uid && caller.uid === parseInt(postData.uid, 10);
+
+	if (postData.deleted && !(userPrivilege.isAdminOrMod || selfPost)) {
+		return null;
+	}
+	postData.pid = pid;
+	const result = await plugins.hooks.fire('filter:post.getRawPost', { uid: caller.uid, postData: postData });
+	return result.postData.content;
+};
+
 postsAPI.edit = async function (caller, data) {
 	if (!data || !data.pid || (meta.config.minimumPostLength !== 0 && !data.content)) {
 		throw new Error('[[error:invalid-data]]');