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node
typescript
hono
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atproto
refactor(appview): implement dependency injection pattern (#11)
Introduces a proper dependency injection pattern to make the appview
more testable and configurable. This change improves separation of
concerns and enables easier mocking in tests.
Changes:
- Add AppContext interface and factory (app-context.ts)
- Extract app creation logic to createApp() (create-app.ts)
- Add test helper createTestContext() (test-context.ts)
- Refactor index.ts to use composition root pattern
- Wrap startup in async main() for better error handling
Benefits:
- Dependencies can be easily swapped for testing
- Clear composition root at application startup
- Proper lifecycle management (creation and cleanup)
- More testable architecture with explicit dependencies
+131
-49
+49
-49
apps/appview/src/index.ts
+49
-49
apps/appview/src/index.ts
···
1
-
import { Hono } from "hono";
2
1
import { serve } from "@hono/node-server";
3
-
import { logger } from "hono/logger";
4
-
import { apiRoutes } from "./routes/index.js";
5
2
import { loadConfig } from "./lib/config.js";
6
-
import { FirehoseService } from "./lib/firehose.js";
7
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import { createDb } from "@atbb/db";
3
+
import { createAppContext, destroyAppContext } from "./lib/app-context.js";
4
+
import { createApp } from "./lib/create-app.js";
8
5
9
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const config = loadConfig();
10
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const db = createDb(config.databaseUrl);
11
-
const app = new Hono();
6
+
async function main() {
7
+
// Load configuration
8
+
const config = loadConfig();
12
9
13
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app.use("*", logger());
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app.route("/api", apiRoutes);
10
+
// Create application context with all dependencies
11
+
const ctx = await createAppContext(config);
15
12
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-
// Initialize firehose service
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const firehose = new FirehoseService(db, config.jetstreamUrl);
13
+
// Create Hono app
14
+
const app = createApp(ctx);
18
15
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// Start the server
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const server = serve(
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{
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fetch: app.fetch,
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port: config.port,
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},
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(info) => {
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console.log(`atBB AppView listening on http://localhost:${info.port}`);
27
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}
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);
16
+
// Start HTTP server
17
+
const server = serve(
18
+
{
19
+
fetch: app.fetch,
20
+
port: config.port,
21
+
},
22
+
(info) => {
23
+
console.log(`atBB AppView listening on http://localhost:${info.port}`);
24
+
}
25
+
);
29
26
30
-
// Start the firehose subscription
31
-
firehose.start().catch((error) => {
32
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console.error("Failed to start firehose:", error);
33
-
process.exit(1);
34
-
});
27
+
// Start firehose subscription
28
+
ctx.firehose.start().catch((error) => {
29
+
console.error("Failed to start firehose:", error);
30
+
process.exit(1);
31
+
});
35
32
36
-
// Handle graceful shutdown
37
-
const shutdown = async (signal: string) => {
38
-
console.log(`\nReceived ${signal}, shutting down gracefully...`);
33
+
// Graceful shutdown handler
34
+
const shutdown = async (signal: string) => {
35
+
console.log(`\nReceived ${signal}, shutting down gracefully...`);
39
36
40
-
try {
41
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// Stop the firehose
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await firehose.stop();
37
+
try {
38
+
await destroyAppContext(ctx);
43
39
44
-
// Close the server
45
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server.close(() => {
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console.log("Server closed");
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process.exit(0);
48
-
});
40
+
server.close(() => {
41
+
console.log("Server closed");
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+
process.exit(0);
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+
});
49
44
50
-
// Force exit after 10 seconds
51
-
setTimeout(() => {
52
-
console.error("Forced shutdown after timeout");
45
+
setTimeout(() => {
46
+
console.error("Forced shutdown after timeout");
47
+
process.exit(1);
48
+
}, 10000);
49
+
} catch (error) {
50
+
console.error("Error during shutdown:", error);
53
51
process.exit(1);
54
-
}, 10000);
55
-
} catch (error) {
56
-
console.error("Error during shutdown:", error);
57
-
process.exit(1);
58
-
}
59
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};
52
+
}
53
+
};
60
54
61
-
process.on("SIGTERM", () => shutdown("SIGTERM"));
62
-
process.on("SIGINT", () => shutdown("SIGINT"));
55
+
process.on("SIGTERM", () => shutdown("SIGTERM"));
56
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process.on("SIGINT", () => shutdown("SIGINT"));
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+
}
58
+
59
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main().catch((error) => {
60
+
console.error("Fatal error during startup:", error);
61
+
process.exit(1);
62
+
});
+28
apps/appview/src/lib/__tests__/test-context.ts
+28
apps/appview/src/lib/__tests__/test-context.ts
···
1
+
import { createDb } from "@atbb/db";
2
+
import { FirehoseService } from "../firehose.js";
3
+
import type { AppContext } from "../app-context.js";
4
+
import type { AppConfig } from "../config.js";
5
+
6
+
/**
7
+
* Create a test application context with in-memory database.
8
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* Useful for integration tests.
9
+
*/
10
+
export function createTestContext(overrides?: Partial<AppConfig>): AppContext {
11
+
const config: AppConfig = {
12
+
port: 3000,
13
+
forumDid: "did:plc:test",
14
+
pdsUrl: "https://test.pds",
15
+
databaseUrl: process.env.DATABASE_URL ?? "",
16
+
jetstreamUrl: "wss://test.jetstream",
17
+
...overrides,
18
+
};
19
+
20
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const db = createDb(config.databaseUrl);
21
+
const firehose = new FirehoseService(db, config.jetstreamUrl);
22
+
23
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return {
24
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config,
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+
db,
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firehose,
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};
28
+
}
+37
apps/appview/src/lib/app-context.ts
+37
apps/appview/src/lib/app-context.ts
···
1
+
import type { Database } from "@atbb/db";
2
+
import { createDb } from "@atbb/db";
3
+
import { FirehoseService } from "./firehose.js";
4
+
import type { AppConfig } from "./config.js";
5
+
6
+
/**
7
+
* Application context holding all shared dependencies.
8
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* This interface defines the contract for dependency injection.
9
+
*/
10
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export interface AppContext {
11
+
config: AppConfig;
12
+
db: Database;
13
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firehose: FirehoseService;
14
+
}
15
+
16
+
/**
17
+
* Create and initialize the application context with all dependencies.
18
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* This is the composition root where we wire up all dependencies.
19
+
*/
20
+
export async function createAppContext(config: AppConfig): Promise<AppContext> {
21
+
const db = createDb(config.databaseUrl);
22
+
const firehose = new FirehoseService(db, config.jetstreamUrl);
23
+
24
+
return {
25
+
config,
26
+
db,
27
+
firehose,
28
+
};
29
+
}
30
+
31
+
/**
32
+
* Cleanup and release resources held by the application context.
33
+
*/
34
+
export async function destroyAppContext(ctx: AppContext): Promise<void> {
35
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await ctx.firehose.stop();
36
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// Future: close database connection when needed
37
+
}
+17
apps/appview/src/lib/create-app.ts
+17
apps/appview/src/lib/create-app.ts
···
1
+
import { Hono } from "hono";
2
+
import { logger } from "hono/logger";
3
+
import { apiRoutes } from "../routes/index.js";
4
+
import type { AppContext } from "./app-context.js";
5
+
6
+
/**
7
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* Create the Hono application with routes and middleware.
8
+
* Routes can access the context via c.env or closure.
9
+
*/
10
+
export function createApp(ctx: AppContext) {
11
+
const app = new Hono();
12
+
13
+
app.use("*", logger());
14
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app.route("/api", apiRoutes);
15
+
16
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return app;
17
+
}