┌─────────┐  ┌─────────┐  ┌─────────┐
│Telegram  │  │Discord  │  │Feishu   │  ...more platforms
└───┬─────┘  └───┬─────┘  └───┬─────┘
    │            │            │
    ▼            ▼            ▼
┌───────────────────────────────────┐
│         AgentIM (Axum)            │
│  ┌──────────┐ ┌────────────────┐  │
│  │Ingress   │ │Session Store   │  │
│  │(webhooks │ │(DashMap)       │  │
│  │+polling) │ │                │  │
│  └──────────┘ └────────────────┘  │
│  ┌──────────┐ ┌────────────────┐  │
│  │Router    │ │Context Trimmer │  │
│  │(rules)   │ │                │  │
│  └──────────┘ └────────────────┘  │
└───────────┬───────────────────────┘
            │
            ▼
┌───────────────────┐
│   Codex Backend   │
│   (app-server)    │
└───────────────────┘

#[async_trait]
pub trait PlatformHandler: Send + Sync {
    async fn handle_inbound(&self, msg: InboundMessage) -> Result<()>;
    async fn send_response(&self, target: ReplyTarget, text: &str) -> Result<()>;
}

use dashmap::DashMap;

pub struct SessionStore {
    sessions: DashMap<String, Session>,
}

pub struct Session {
    pub user_id: String,
    pub platform: Platform,
    pub history: Vec<Message>,
    pub created_at: DateTime<Utc>,
}

pub fn trim_context(history: &mut Vec<Message>, max_tokens: usize) {
    // Keep the most recent messages that fit within max_tokens
    let mut token_count = 0;
    let cutoff = history.iter().rev().position(|msg| {
        token_count += estimate_tokens(&msg.text);
        token_count > max_tokens
    }).unwrap_or(history.len());

    history.drain(0..cutoff);
}

// Discord: Ed25519
pub fn verify_discord_signature(body: &[u8], signature: &str, timestamp: &str, public_key: &str) -> bool {
    let message = format!("{}{}", timestamp, body);
    ed25519_verify(message.as_bytes(), signature, public_key)
}

// Slack / DingTalk: HMAC-SHA256
pub fn verify_hmac_signature(body: &[u8], signature: &str, secret: &str) -> bool {
    let expected = hmac_sha256(body, secret);
    signature == expected
}

pub struct RoutingRule {
    pub channel_pattern: String, // Regex
    pub user_pattern: Option<String>,
    pub target: ReplyTarget,
}

// Example: route all #help channel messages to a FAQ bot
// Example: route DMs from specific users to a custom agent

# docker-compose.yml
services:
  agentim:
    build: .
    ports:
      - "8080:8080"
    environment:
      - TELEGRAM_BOT_TOKEN=${TELEGRAM_BOT_TOKEN}
      - DISCORD_PUBLIC_KEY=${DISCORD_PUBLIC_KEY}
      - CODEX_API_URL=http://codex:3002
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:8080/health"]
      interval: 30s

// /health — service status
// /ready   — can process requests
// /review  — pending human-review items (optional)