DiscordClone/CONVEX_EXAMPLES.md

# Convex Examples

Reference implementations for common Convex patterns.

---

## Example: Chat App with AI Responses

A real-time chat backend demonstrating:
- User and channel management
- Message storage with proper ordering
- OpenAI integration for AI responses
- Background job scheduling

### Task Requirements
- Allow creating users with names
- Support multiple chat channels
- Enable users to send messages to channels
- Automatically generate AI responses to user messages
- Show recent message history (10 most recent per channel)

### API Design

**Public Mutations:**
- `createUser` - Create user with name
- `createChannel` - Create channel with name
- `sendMessage` - Send message and trigger AI response

**Public Queries:**
- `listMessages` - Get 10 most recent messages (descending)

**Internal Functions:**
- `generateResponse` - Call OpenAI API
- `loadContext` - Load message history for AI context
- `writeAgentResponse` - Save AI response to database

### Schema Design
```
users: { name: string }
channels: { name: string }
messages: { channelId, authorId?, content } + index by_channel
```

---

### Implementation

#### package.json
```json
{
  "name": "chat-app",
  "version": "1.0.0",
  "dependencies": {
    "convex": "^1.31.2",
    "openai": "^4.79.0"
  },
  "devDependencies": {
    "typescript": "^5.7.3"
  }
}
```

#### convex/schema.ts
```typescript
import { defineSchema, defineTable } from "convex/server";
import { v } from "convex/values";

export default defineSchema({
  channels: defineTable({
    name: v.string(),
  }),

  users: defineTable({
    name: v.string(),
  }),

  messages: defineTable({
    channelId: v.id("channels"),
    authorId: v.optional(v.id("users")),
    content: v.string(),
  }).index("by_channel", ["channelId"]),
});
```

#### convex/index.ts
```typescript
import {
  query,
  mutation,
  internalQuery,
  internalMutation,
  internalAction,
} from "./_generated/server";
import { v } from "convex/values";
import OpenAI from "openai";
import { internal } from "./_generated/api";

/**
 * Create a user with a given name.
 */
export const createUser = mutation({
  args: {
    name: v.string(),
  },
  returns: v.id("users"),
  handler: async (ctx, args) => {
    return await ctx.db.insert("users", { name: args.name });
  },
});

/**
 * Create a channel with a given name.
 */
export const createChannel = mutation({
  args: {
    name: v.string(),
  },
  returns: v.id("channels"),
  handler: async (ctx, args) => {
    return await ctx.db.insert("channels", { name: args.name });
  },
});

/**
 * List the 10 most recent messages from a channel in descending creation order.
 */
export const listMessages = query({
  args: {
    channelId: v.id("channels"),
  },
  returns: v.array(
    v.object({
      _id: v.id("messages"),
      _creationTime: v.number(),
      channelId: v.id("channels"),
      authorId: v.optional(v.id("users")),
      content: v.string(),
    }),
  ),
  handler: async (ctx, args) => {
    const messages = await ctx.db
      .query("messages")
      .withIndex("by_channel", (q) => q.eq("channelId", args.channelId))
      .order("desc")
      .take(10);
    return messages;
  },
});

/**
 * Send a message to a channel and schedule a response from the AI.
 */
export const sendMessage = mutation({
  args: {
    channelId: v.id("channels"),
    authorId: v.id("users"),
    content: v.string(),
  },
  returns: v.null(),
  handler: async (ctx, args) => {
    const channel = await ctx.db.get(args.channelId);
    if (!channel) {
      throw new Error("Channel not found");
    }
    const user = await ctx.db.get(args.authorId);
    if (!user) {
      throw new Error("User not found");
    }
    await ctx.db.insert("messages", {
      channelId: args.channelId,
      authorId: args.authorId,
      content: args.content,
    });
    await ctx.scheduler.runAfter(0, internal.index.generateResponse, {
      channelId: args.channelId,
    });
    return null;
  },
});

const openai = new OpenAI();

export const generateResponse = internalAction({
  args: {
    channelId: v.id("channels"),
  },
  returns: v.null(),
  handler: async (ctx, args) => {
    const context = await ctx.runQuery(internal.index.loadContext, {
      channelId: args.channelId,
    });
    const response = await openai.chat.completions.create({
      model: "gpt-4o",
      messages: context,
    });
    const content = response.choices[0].message.content;
    if (!content) {
      throw new Error("No content in response");
    }
    await ctx.runMutation(internal.index.writeAgentResponse, {
      channelId: args.channelId,
      content,
    });
    return null;
  },
});

export const loadContext = internalQuery({
  args: {
    channelId: v.id("channels"),
  },
  returns: v.array(
    v.object({
      role: v.union(v.literal("user"), v.literal("assistant")),
      content: v.string(),
    }),
  ),
  handler: async (ctx, args) => {
    const channel = await ctx.db.get(args.channelId);
    if (!channel) {
      throw new Error("Channel not found");
    }
    const messages = await ctx.db
      .query("messages")
      .withIndex("by_channel", (q) => q.eq("channelId", args.channelId))
      .order("desc")
      .take(10);

    const result = [];
    for (const message of messages) {
      if (message.authorId) {
        const user = await ctx.db.get(message.authorId);
        if (!user) {
          throw new Error("User not found");
        }
        result.push({
          role: "user" as const,
          content: `${user.name}: ${message.content}`,
        });
      } else {
        result.push({ role: "assistant" as const, content: message.content });
      }
    }
    return result;
  },
});

export const writeAgentResponse = internalMutation({
  args: {
    channelId: v.id("channels"),
    content: v.string(),
  },
  returns: v.null(),
  handler: async (ctx, args) => {
    await ctx.db.insert("messages", {
      channelId: args.channelId,
      content: args.content,
    });
    return null;
  },
});
```

#### convex/tsconfig.json
```json
{
  "compilerOptions": {
    "allowJs": true,
    "strict": true,
    "moduleResolution": "Bundler",
    "jsx": "react-jsx",
    "skipLibCheck": true,
    "allowSyntheticDefaultImports": true,
    "target": "ESNext",
    "lib": ["ES2021", "dom"],
    "forceConsistentCasingInFileNames": true,
    "module": "ESNext",
    "isolatedModules": true,
    "noEmit": true
  },
  "include": ["./**/*"],
  "exclude": ["./_generated"]
}
```

#### tsconfig.json (root)
```json
{
  "compilerOptions": {
    "target": "ESNext",
    "lib": ["DOM", "DOM.Iterable", "ESNext"],
    "skipLibCheck": true,
    "allowSyntheticDefaultImports": true,
    "strict": true,
    "forceConsistentCasingInFileNames": true,
    "module": "ESNext",
    "moduleResolution": "Bundler",
    "resolveJsonModule": true,
    "isolatedModules": true,
    "allowImportingTsExtensions": true,
    "noEmit": true,
    "jsx": "react-jsx"
  },
  "exclude": ["convex"],
  "include": ["**/src/**/*.tsx", "**/src/**/*.ts", "vite.config.ts"]
}
```