2 files changed, 224 insertions, 0 deletions
diff --git a/packages/backend/src/server/api/openapi/OpenApiServerService.ts b/packages/backend/src/server/api/openapi/OpenApiServerService.ts
new file mode 100644
index 0000000000..e804ba276c
--- /dev/null
+++ b/packages/backend/src/server/api/openapi/OpenApiServerService.ts
@@ -0,0 +1,31 @@
+import { fileURLToPath } from 'node:url';
+import { Inject, Injectable } from '@nestjs/common';
+import type { Config } from '@/config.js';
+import { DI } from '@/di-symbols.js';
+import { bindThis } from '@/decorators.js';
+import { genOpenapiSpec } from './gen-spec.js';
+import type { FastifyInstance, FastifyPluginOptions } from 'fastify';
+
+const staticAssets = fileURLToPath(new URL('../../../../assets/', import.meta.url));
+
+@Injectable()
+export class OpenApiServerService {
+	constructor(
+		@Inject(DI.config)
+		private config: Config,
+	) {
+	}
+
+	@bindThis
+	public createServer(fastify: FastifyInstance, _options: FastifyPluginOptions, done: (err?: Error) => void) {
+		fastify.get('/api-doc', async (_request, reply) => {
+			reply.header('Cache-Control', 'public, max-age=86400');
+			return await reply.sendFile('/redoc.html', staticAssets);
+		});
+		fastify.get('/api.json', (_request, reply) => {
+			reply.header('Cache-Control', 'public, max-age=600');
+			reply.send(genOpenapiSpec(this.config));
+		});
+		done();
+	}
+}
diff --git a/packages/backend/src/server/api/openapi/gen-spec.ts b/packages/backend/src/server/api/openapi/gen-spec.ts
new file mode 100644
index 0000000000..fa62480c02
--- /dev/null
+++ b/packages/backend/src/server/api/openapi/gen-spec.ts
@@ -0,0 +1,193 @@
+import type { Config } from '@/config.js';
+import endpoints from '../endpoints.js';
+import { errors as basicErrors } from './errors.js';
+import { schemas, convertSchemaToOpenApiSchema } from './schemas.js';
+
+export function genOpenapiSpec(config: Config) {
+	const spec = {
+		openapi: '3.0.0',
+
+		info: {
+			version: config.version,
+			title: 'Misskey API',
+			'x-logo': { url: '/static-assets/api-doc.png' },
+		},
+
+		externalDocs: {
+			description: 'Repository',
+			url: 'https://github.com/misskey-dev/misskey',
+		},
+
+		servers: [{
+			url: config.apiUrl,
+		}],
+
+		paths: {} as any,
+
+		components: {
+			schemas: schemas,
+
+			securitySchemes: {
+				ApiKeyAuth: {
+					type: 'apiKey',
+					in: 'body',
+					name: 'i',
+				},
+			},
+		},
+	};
+
+	for (const endpoint of endpoints.filter(ep => !ep.meta.secure)) {
+		const errors = {} as any;
+
+		if (endpoint.meta.errors) {
+			for (const e of Object.values(endpoint.meta.errors)) {
+				errors[e.code] = {
+					value: {
+						error: e,
+					},
+				};
+			}
+		}
+
+		const resSchema = endpoint.meta.res ? convertSchemaToOpenApiSchema(endpoint.meta.res) : {};
+
+		let desc = (endpoint.meta.description ? endpoint.meta.description : 'No description provided.') + '\n\n';
+		desc += `**Credential required**: *${endpoint.meta.requireCredential ? 'Yes' : 'No'}*`;
+		if (endpoint.meta.kind) {
+			const kind = endpoint.meta.kind;
+			desc += ` / **Permission**: *${kind}*`;
+		}
+
+		const requestType = endpoint.meta.requireFile ? 'multipart/form-data' : 'application/json';
+		const schema = { ...endpoint.params };
+
+		if (endpoint.meta.requireFile) {
+			schema.properties = {
+				...schema.properties,
+				file: {
+					type: 'string',
+					format: 'binary',
+					description: 'The file contents.',
+				},
+			};
+			schema.required = [...schema.required ?? [], 'file'];
+		}
+
+		const info = {
+			operationId: endpoint.name,
+			summary: endpoint.name,
+			description: desc,
+			externalDocs: {
+				description: 'Source code',
+				url: `https://github.com/misskey-dev/misskey/blob/develop/packages/backend/src/server/api/endpoints/${endpoint.name}.ts`,
+			},
+			...(endpoint.meta.tags ? {
+				tags: [endpoint.meta.tags[0]],
+			} : {}),
+			...(endpoint.meta.requireCredential ? {
+				security: [{
+					ApiKeyAuth: [],
+				}],
+			} : {}),
+			requestBody: {
+				required: true,
+				content: {
+					[requestType]: {
+						schema,
+					},
+				},
+			},
+			responses: {
+				...(endpoint.meta.res ? {
+					'200': {
+						description: 'OK (with results)',
+						content: {
+							'application/json': {
+								schema: resSchema,
+							},
+						},
+					},
+				} : {
+					'204': {
+						description: 'OK (without any results)',
+					},
+				}),
+				'400': {
+					description: 'Client error',
+					content: {
+						'application/json': {
+							schema: {
+								$ref: '#/components/schemas/Error',
+							},
+							examples: { ...errors, ...basicErrors['400'] },
+						},
+					},
+				},
+				'401': {
+					description: 'Authentication error',
+					content: {
+						'application/json': {
+							schema: {
+								$ref: '#/components/schemas/Error',
+							},
+							examples: basicErrors['401'],
+						},
+					},
+				},
+				'403': {
+					description: 'Forbidden error',
+					content: {
+						'application/json': {
+							schema: {
+								$ref: '#/components/schemas/Error',
+							},
+							examples: basicErrors['403'],
+						},
+					},
+				},
+				'418': {
+					description: 'I\'m Ai',
+					content: {
+						'application/json': {
+							schema: {
+								$ref: '#/components/schemas/Error',
+							},
+							examples: basicErrors['418'],
+						},
+					},
+				},
+				...(endpoint.meta.limit ? {
+					'429': {
+						description: 'To many requests',
+						content: {
+							'application/json': {
+								schema: {
+									$ref: '#/components/schemas/Error',
+								},
+								examples: basicErrors['429'],
+							},
+						},
+					},
+				} : {}),
+				'500': {
+					description: 'Internal server error',
+					content: {
+						'application/json': {
+							schema: {
+								$ref: '#/components/schemas/Error',
+							},
+							examples: basicErrors['500'],
+						},
+					},
+				},
+			},
+		};
+
+		spec.paths['/' + endpoint.name] = {
+			post: info,
+		};
+	}
+
+	return spec;
+}