feat: Add demo-generator crate for Semantic Drift demonstration

Author: varshith-Git

.gitignore

@@ -55,3 +55,4 @@ Thumbs.db
 .agent/
 *.log
 *.log
+demo_db/

Cargo.lock

@@ -21,6 +21,7 @@ members = [
     "crates/persistence",
     "crates/cli",
     "crates/kernel",
+    "crates/demo-generator",
 ]
 
 # Firmware requires abort on panic (no unwinding support in no_std)

Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "demo-generator"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+valori-kernel = { path = "../kernel" }
+valori-persistence = { path = "../persistence" }
+byteorder = "1.5"
+crc64fast = "1.0"
+anyhow = "1.0"

crates/demo-generator/Cargo.toml

@@ -0,0 +1,102 @@
+use anyhow::Result;
+use byteorder::{LittleEndian, WriteBytesExt};
+use crc64fast::Digest;
+use std::path::Path;
+use valori_kernel::ValoriKernel;
+use valori_persistence::{snapshot, wal};
+use valori_persistence::snapshot::SnapshotHeader;
+
+fn main() -> Result<()> {
+    let out_dir = Path::new("demo_db");
+    if out_dir.exists() {
+        std::fs::remove_dir_all(out_dir)?;
+    }
+    std::fs::create_dir_all(&out_dir)?;
+
+    let mut kernel = ValoriKernel::new();
+
+    println!("🎬 Generating 'Semantic Drift' Dataset...");
+
+    // --- SCENE 1: The "Red" Cluster (ID 1-100) ---
+    // Center: [1000, 1000]
+    println!("1. Ingesting 100 'Red' vectors...");
+    for i in 1..=100 {
+        let x = 1000 + rand_diff(i);
+        let y = 1000 + rand_diff(i + 1000); // Different seed
+        let payload = create_insert_payload(i, vec![x, y]);
+        kernel.apply_event(&payload)?;
+    }
+
+    // --- CHECKPOINT 1: SNAPSHOT ---
+    println!("2. Taking Snapshot (Checkpoint 1)...");
+    let snap_body = kernel.save_snapshot()?;
+    
+    // Compute Hash
+    let mut digest = Digest::new();
+    digest.write(&snap_body);
+    let checksum = digest.sum64();
+    let mut state_hash = [0u8; 16];
+    state_hash[0..8].copy_from_slice(&checksum.to_le_bytes());
+
+    let header = SnapshotHeader::new(100, 1700000000, state_hash); 
+    
+    snapshot::write_to(out_dir.join("snapshot.val"), header, &snap_body)?;
+
+    // --- SCENE 2: The "Blue" Intrusion (ID 101-200) ---
+    // Center: [3000, 3000] (Far away from Red)
+    println!("3. Ingesting 100 'Blue' vectors (Drift)...");
+    
+    let wal_path = out_dir.join("events.log");
+    
+    // We will append to WAL directly.
+    for i in 101..=200 {
+        let x = 3000 + rand_diff(i);
+        let y = 3000 + rand_diff(i + 2000);
+        let payload = create_insert_payload(i, vec![x, y]);
+        
+        // Append to WAL
+        wal::append_entry(&wal_path, i, &payload)?;
+    }
+
+    // --- SCENE 3: The "Purple" Influencer (ID 201) ---
+    // Position: [1500, 1500] (Exact match for the query)
+    println!("4. Ingesting 1 'Purple' Influencer...");
+    let x = 1500;
+    let y = 1500;
+    let payload = create_insert_payload(201, vec![x, y]);
+    wal::append_entry(&wal_path, 201, &payload)?;
+
+    // Create a dummy metadata index
+    let idx_path = out_dir.join("metadata.idx");
+    valori_persistence::idx::append_metadata(&idx_path, 100, None, "snapshot".to_string())?;
+    valori_persistence::idx::append_metadata(&idx_path, 150, None, "blue_wave".to_string())?;
+    valori_persistence::idx::append_metadata(&idx_path, 201, None, "purple_event".to_string())?;
+
+    println!("✅ Demo Database generated at: {:?}", out_dir.canonicalize()?);
+    println!("📊 Story: Red (0-100) -> Blue (101-200) -> Purple (201)");
+    println!("   Try: valori diff --dir demo_db --from 100 --to 201 --query '[1500, 1500]'");
+
+    Ok(())
+}
+
+fn create_insert_payload(id: u64, values: Vec<i32>) -> Vec<u8> {
+    let dim = values.len() as u16;
+    let mut wtr = Vec::new();
+    wtr.write_u8(1).unwrap(); // CMD_INSERT
+    wtr.write_u64::<LittleEndian>(id).unwrap();
+    wtr.write_u16::<LittleEndian>(dim).unwrap();
+    for v in values {
+        wtr.write_i32::<LittleEndian>(v).unwrap();
+    }
+    wtr
+}
+
+// Deterministic Pseudo-Random
+fn rand_diff(seed: u64) -> i32 {
+    let mut x = seed;
+    x ^= x << 13;
+    x ^= x >> 7;
+    x ^= x << 17;
+    // Range -100 to 100
+    ((x % 200) as i32) - 100
+}