L4: Applications Layer

pub struct L4Feed {
    pub backend: FeedBackend,
    pub events: EventLog,
    pub index: QueryIndex,
}

pub enum FeedBackend {
    DuckDB,       // Embedded analytics
    LanceDB,      // Vector search
    Libmdbx,      // Single-file storage
}

pub struct Event {
    pub id: EventId,                    // BLAKE3 hash
    pub timestamp: SovereignTimestamp,  // Nanosecond precision
    pub author: Did,                    // Self-sovereign identity
    pub type: EventType,
    pub payload: Vec<u8>,
    pub signature: Ed25519Signature,
    pub parents: Vec<EventId>,          // DAG structure
}

pub enum EventType {
    Message,      // Encrypted content
    State,        // Application state update
    Credential,   // Verifiable credential
    Contract,     // State channel update
}

// GQL: Graph Query Language (ISO/IEC 39075:2024)
let results = feed.query(r#"
    MATCH (e:Event)
    WHERE e.author = "did:libertaria:z8m9n..."
      AND e.timestamp > $since
      AND e.type = "Message"
    RETURN e.id, e.timestamp, e.payload
    ORDER BY e.timestamp DESC
    LIMIT 100
"#, params!{"since": last_check});

// Rust example (libertaria-sdk-rs)
use libertaria::{SoulKey, Chapter, Feed};

#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
    // Generate identity
    let key = SoulKey::generate();
    let did = key.derive_did("identity")?;

    // Join Chapter
    let berlin = Chapter::connect("chapter://berlin/core").await?;
    berlin.join(&key, min_reputation=0.5).await?;

    // Create feed
    let feed = Feed::create(did.clone())?;

    // Publish event
    feed.publish(Event::new(
        author: did,
        type: EventType::Message,
        payload: b"Hello, sovereign world!".to_vec(),
    )).await?;

    Ok(())
}

// C header (libertaria.h)
libertaria_soulkey_t* libertaria_soulkey_generate(
    const uint8_t* seed,
    size_t seed_len
);

libertaria_error_t libertaria_soulkey_derive_did(
    libertaria_soulkey_t* key,
    const char* context,
    char* out_did,
    size_t out_capacity
);

void libertaria_soulkey_free(libertaria_soulkey_t* key);

pub struct AgentRuntime {
    pub wasm_engine: WasmEngine,
    pub capabilities: CapabilitySet,
    pub sandbox: SandboxConfig,
}

pub struct SandboxConfig {
    pub max_memory: usize,        // 100 MB default
    pub max_compute: u64,         // Gas-like limit
    pub allowed_apis: Vec<Api>,
    pub network_access: bool,     // Off by default
}

Components:
  - L4 Feed for timeline
  - QVL for follow recommendations
  - Chapters for communities
  - State channels for direct messages

Properties:
  - No platform can ban you
  - No algorithm controls your feed
  - Your social graph is portable

Components:
  - VCs for reputation
  - State channels for escrow
  - Chapters for marketplace governance
  - QVL for trust scoring vendors

Properties:
  - No payment processor can freeze funds
  - No platform can delist you
  - Dispute resolution by trusted Chapters

Components:
  - L4 Feed for project updates
  - Chapters for team governance
  - State channels for milestone payments
  - QVL for contributor reputation

Properties:
  - No corporate owner can shut down
  - Contributors own their contributions
  - Fork if governance fails