feat: add stateful multi-turn execution demo binary

Signed-off-by: danbugs <danilochiarlone@gmail.com>

Author: danbugs

host/Cargo.toml

@@ -26,6 +26,10 @@ path = "src/bin/pydriver_run.rs"
 name = "pyhl"
 path = "src/bin/pyhl.rs"
 
+[[bin]]
+name = "stateful-demo"
+path = "src/bin/stateful_demo.rs"
+
 [dependencies]
 # danbugs/hyperlight feat/whp-no-surrogate — testing runtime no-surrogate mode.
 hyperlight-host = { git = "https://github.com/danbugs/hyperlight", rev = "212f20a5", features = ["executable_heap", "hw-interrupts"] }

host/src/bin/stateful_demo.rs

@@ -0,0 +1,97 @@
+use anyhow::{anyhow, Context, Result};
+use hyperlight_unikraft::pyhl;
+use std::path::PathBuf;
+use std::time::Instant;
+
+fn resolve_home() -> Result<PathBuf> {
+    if let Ok(h) = std::env::var("PYHL_HOME") {
+        return Ok(PathBuf::from(h));
+    }
+    let cwd = std::env::current_dir().context("read cwd")?.join(".pyhl");
+    if cwd.join("snapshot").is_dir() {
+        return Ok(cwd);
+    }
+    #[cfg(unix)]
+    {
+        let xdg = std::env::var_os("XDG_DATA_HOME")
+            .map(PathBuf::from)
+            .filter(|p| p.is_absolute())
+            .unwrap_or_else(|| {
+                let home = std::env::var_os("HOME")
+                    .map(PathBuf::from)
+                    .unwrap_or_else(|| PathBuf::from("/"));
+                home.join(".local/share")
+            })
+            .join("pyhl");
+        if xdg.join("snapshot").is_dir() {
+            return Ok(xdg);
+        }
+    }
+    #[cfg(windows)]
+    {
+        if let Ok(local) = std::env::var("LOCALAPPDATA") {
+            let win = PathBuf::from(local).join("pyhl");
+            if win.join("snapshot").is_dir() {
+                return Ok(win);
+            }
+        }
+        let home_dir = std::env::var("USERPROFILE").unwrap_or_else(|_| "C:\\Users\\Default".into());
+        let dotpyhl = PathBuf::from(home_dir).join(".pyhl");
+        if dotpyhl.join("snapshot").is_dir() {
+            return Ok(dotpyhl);
+        }
+    }
+    Err(anyhow!(
+        "no pyhl image found. run `pyhl setup` first, or set PYHL_HOME."
+    ))
+}
+
+fn main() -> Result<()> {
+    let home = resolve_home()?;
+
+    println!("Stateful multi-turn execution demo");
+    println!("==================================\n");
+
+    let t_init = Instant::now();
+    let mut rt = pyhl::Runtime::new(&home, &[], None, None, Some(0))?;
+    println!(
+        "[init] runtime created in {:.0}ms\n",
+        t_init.elapsed().as_secs_f64() * 1000.0
+    );
+
+    let turns: &[(&str, &str)] = &[
+        (
+            "Turn 1: Create variables",
+            "x = 42\ny = 'hello from turn 1'\nprint(f'  x = {x}, y = {y!r}')",
+        ),
+        (
+            "Turn 2: Access previous state + compute",
+            "z = x * 2\nprint(f'  z = x * 2 = {z}')\nprint(f'  y from turn 1: {y!r}')",
+        ),
+        (
+            "Turn 3: Import library, build on prior state",
+            "import pandas as pd\ndf = pd.DataFrame({'val': [x, z, x + z]})\nprint(df.to_string(index=False))",
+        ),
+        (
+            "Turn 4: Use everything from all prior turns",
+            "total = df['val'].sum()\nprint(f'  x={x}, z={z}, df_sum={total}')\nprint(f'  All state persisted across {4} turns!')",
+        ),
+    ];
+
+    for (i, (label, code)) in turns.iter().enumerate() {
+        println!("--- {} ---", label);
+        let t = rt.run_code_stateful(code)?;
+        println!(
+            "  [{:.0}ms{}]\n",
+            t.call_ms,
+            if i == 0 {
+                format!(" (includes initial restore: {:.0}ms)", t.restore_ms)
+            } else {
+                String::new()
+            }
+        );
+    }
+
+    println!("Session complete — sandbox torn down.");
+    Ok(())
+}