From d8e22705e60191e36d21abae7676bfeb4df8ba40 Mon Sep 17 00:00:00 2001
From: Sven Sauleau <sven@cloudflare.com>
Date: Mon, 13 Feb 2023 12:13:54 +0000
Subject: [PATCH] view single tag

---
 backend/src/errors/index.ts        |  4 ++++
 backend/src/mastodon/hashtag.ts    | 21 +++++++++++++++++
 backend/src/types/tag.ts           |  6 +++++
 backend/test/mastodon/tags.spec.ts | 36 ++++++++++++++++++++++++++++++
 functions/api/v1/tags/[tag].ts     | 25 +++++++++++++++++++++
 5 files changed, 92 insertions(+)
 create mode 100644 backend/src/types/tag.ts
 create mode 100644 backend/test/mastodon/tags.spec.ts
 create mode 100644 functions/api/v1/tags/[tag].ts

diff --git a/backend/src/errors/index.ts b/backend/src/errors/index.ts
index b402830..e129e78 100644
--- a/backend/src/errors/index.ts
+++ b/backend/src/errors/index.ts
@@ -46,6 +46,10 @@ export function mediaNotFound(id: string): Response {
 	return generateErrorResponse('Resource not found', 404, `Media "${id}" not found`)
 }
 
+export function tagNotFound(tag: string): Response {
+	return generateErrorResponse('Resource not found', 404, `Tag "${tag}" not found`)
+}
+
 export function exceededLimit(detail: string): Response {
 	return generateErrorResponse('Limit exceeded', 400, detail)
 }
diff --git a/backend/src/mastodon/hashtag.ts b/backend/src/mastodon/hashtag.ts
index 8d9131d..5f8aff0 100644
--- a/backend/src/mastodon/hashtag.ts
+++ b/backend/src/mastodon/hashtag.ts
@@ -1,4 +1,5 @@
 import type { Note } from 'wildebeest/backend/src/activitypub/objects/note'
+import type { Tag } from 'wildebeest/backend/src/types/tag'
 
 export type Hashtag = string
 
@@ -27,3 +28,23 @@ export async function insertHashtags(db: D1Database, note: Note, values: Array<H
 
 	await db.batch(queries)
 }
+
+export async function getTag(db: D1Database, domain: string, tag: string): Promise<Tag | null> {
+	const query = `
+        SELECT * FROM note_hashtags WHERE value=?
+    `
+	const { results, success, error } = await db.prepare(query).bind(tag).all<{ value: string }>()
+	if (!success) {
+		throw new Error('SQL error: ' + error)
+	}
+
+	if (!results || results.length === 0) {
+		return null
+	}
+
+	return {
+		name: results[0].value,
+		url: new URL(`/tags/${results[0].value}`, `https://${domain}`),
+		history: [],
+	}
+}
diff --git a/backend/src/types/tag.ts b/backend/src/types/tag.ts
new file mode 100644
index 0000000..0b44dfe
--- /dev/null
+++ b/backend/src/types/tag.ts
@@ -0,0 +1,6 @@
+export type Tag = {
+	name: string
+	url: URL
+	history: Array<void>
+	following?: boolean
+}
diff --git a/backend/test/mastodon/tags.spec.ts b/backend/test/mastodon/tags.spec.ts
new file mode 100644
index 0000000..58737f1
--- /dev/null
+++ b/backend/test/mastodon/tags.spec.ts
@@ -0,0 +1,36 @@
+import { strict as assert } from 'node:assert/strict'
+import { createPerson } from 'wildebeest/backend/src/activitypub/actors'
+import { createPublicNote } from 'wildebeest/backend/src/activitypub/objects/note'
+import { makeDB, assertCORS, isUrlValid } from '../utils'
+import * as tag_id from 'wildebeest/functions/api/v1/tags/[tag]'
+import { insertHashtags } from 'wildebeest/backend/src/mastodon/hashtag'
+
+const domain = 'cloudflare.com'
+const userKEK = 'test_kek20'
+
+describe('Mastodon APIs', () => {
+	describe('tags', () => {
+		test('return 404 when non existent tag', async () => {
+			const db = await makeDB()
+			const res = await tag_id.handleRequestGet(db, domain, 'non-existent-tag')
+			assertCORS(res)
+			assert.equal(res.status, 404)
+		})
+
+		test('return tag', async () => {
+			const db = await makeDB()
+			const actor = await createPerson(domain, db, userKEK, 'sven@cloudflare.com')
+
+			const note = await createPublicNote(domain, db, 'my localnote status', actor)
+			await insertHashtags(db, note, ['test'])
+
+			const res = await tag_id.handleRequestGet(db, domain, 'test')
+			assertCORS(res)
+			assert.equal(res.status, 200)
+
+			const data = await res.json<any>()
+			assert.equal(data.name, 'test')
+			assert(isUrlValid(data.url))
+		})
+	})
+})
diff --git a/functions/api/v1/tags/[tag].ts b/functions/api/v1/tags/[tag].ts
new file mode 100644
index 0000000..dd1b65d
--- /dev/null
+++ b/functions/api/v1/tags/[tag].ts
@@ -0,0 +1,25 @@
+// https://docs.joinmastodon.org/methods/tags/#get
+
+import type { ContextData } from 'wildebeest/backend/src/types/context'
+import type { Env } from 'wildebeest/backend/src/types/env'
+import { getTag } from 'wildebeest/backend/src/mastodon/hashtag'
+import * as errors from 'wildebeest/backend/src/errors'
+import { cors } from 'wildebeest/backend/src/utils/cors'
+
+const headers = {
+	...cors(),
+	'content-type': 'application/json',
+} as const
+
+export const onRequestGet: PagesFunction<Env, any, ContextData> = async ({ params, env, request }) => {
+	const domain = new URL(request.url).hostname
+	return handleRequestGet(env.DATABASE, domain, params.tag as string)
+}
+
+export async function handleRequestGet(db: D1Database, domain: string, value: string): Promise<Response> {
+	const tag = await getTag(db, domain, value)
+	if (tag === null) {
+		return errors.tagNotFound(value)
+	}
+	return new Response(JSON.stringify(tag), { headers })
+}