From ed246ce434f811a61495fcdd953607acd6300010 Mon Sep 17 00:00:00 2001
From: "Dhanji R. Prasanna" <d@wideplay.com>
Date: Tue, 23 Dec 2025 16:22:12 +1100
Subject: [PATCH] consolidate .g3/session -> .g3/sessions/*

---
 crates/g3-core/src/session_continuation.rs    | 130 +++++++++++++++---
 .../tests/test_session_continuation.rs        |  87 ++++++++++--
 2 files changed, 183 insertions(+), 34 deletions(-)

diff --git a/crates/g3-core/src/session_continuation.rs b/crates/g3-core/src/session_continuation.rs
index 171fcbb..4cd41d5 100644
--- a/crates/g3-core/src/session_continuation.rs
+++ b/crates/g3-core/src/session_continuation.rs
@@ -2,8 +2,13 @@
 //!
 //! This module provides functionality to save and restore session state,
 //! allowing users to resume work across multiple g3 invocations.
+//!
+//! The session continuation uses a symlink-based approach:
+//! - `.g3/session` is a symlink pointing to the current session directory
+//! - `latest.json` is stored inside each session directory (`.g3/sessions/<session_id>/latest.json`)
+//! - Following the symlink gives access to the current session's continuation data
 
-use anyhow::Result;
+use anyhow::{Context, Result};
 use serde::{Deserialize, Serialize};
 use std::path::{Path, PathBuf};
 use tracing::{debug, error, warn};
@@ -11,6 +16,9 @@ use tracing::{debug, error, warn};
 /// Version of the session continuation format
 const CONTINUATION_VERSION: &str = "1.0";
 
+/// Name of the continuation file within each session directory
+const CONTINUATION_FILENAME: &str = "latest.json";
+
 /// Session continuation artifact containing all information needed to resume a session
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct SessionContinuation {
@@ -60,42 +68,117 @@ impl SessionContinuation {
     }
 }
 
-/// Get the path to the .g3/session directory
+/// Get the path to the .g3 directory
+fn get_g3_dir() -> PathBuf {
+    crate::get_g3_dir()
+}
+
+/// Get the path to the .g3/session symlink
 pub fn get_session_dir() -> PathBuf {
-    let current_dir = std::env::current_dir().unwrap_or_else(|_| PathBuf::from("."));
-    current_dir.join(".g3").join("session")
+    get_g3_dir().join("session")
+}
+
+/// Get the path to the .g3/sessions directory (where all sessions are stored)
+fn get_sessions_dir() -> PathBuf {
+    get_g3_dir().join("sessions")
+}
+
+/// Get the path to a specific session's directory
+fn get_session_path(session_id: &str) -> PathBuf {
+    get_sessions_dir().join(session_id)
 }
 
 /// Get the path to the latest.json continuation file
+/// This follows the symlink to get the actual path
 pub fn get_latest_continuation_path() -> PathBuf {
-    get_session_dir().join("latest.json")
+    get_session_dir().join(CONTINUATION_FILENAME)
 }
 
-/// Ensure the .g3/session directory exists
+/// Ensure the .g3 directory exists (but not the session symlink)
 pub fn ensure_session_dir() -> Result<PathBuf> {
-    let session_dir = get_session_dir();
-    if !session_dir.exists() {
-        std::fs::create_dir_all(&session_dir)?;
-        debug!("Created session directory: {:?}", session_dir);
+    let g3_dir = get_g3_dir();
+    if !g3_dir.exists() {
+        std::fs::create_dir_all(&g3_dir)?;
+        debug!("Created .g3 directory: {:?}", g3_dir);
     }
-    Ok(session_dir)
+    Ok(get_session_dir())
+}
+
+/// Update the .g3/session symlink to point to the given session directory
+fn update_session_symlink(session_id: &str) -> Result<()> {
+    let symlink_path = get_session_dir();
+    let target_path = get_session_path(session_id);
+    
+    // Remove existing symlink or directory if it exists
+    if symlink_path.exists() || symlink_path.is_symlink() {
+        if symlink_path.is_symlink() {
+            std::fs::remove_file(&symlink_path)
+                .context("Failed to remove existing session symlink")?;
+        } else if symlink_path.is_dir() {
+            // Migration: if it's an old-style directory, remove it
+            std::fs::remove_dir_all(&symlink_path)
+                .context("Failed to remove old session directory")?;
+            debug!("Migrated old .g3/session directory to symlink");
+        }
+    }
+    
+    // Create the symlink
+    #[cfg(unix)]
+    std::os::unix::fs::symlink(&target_path, &symlink_path)
+        .context("Failed to create session symlink")?;
+    
+    #[cfg(windows)]
+    std::os::windows::fs::symlink_dir(&target_path, &symlink_path)
+        .context("Failed to create session symlink")?;
+    
+    debug!("Updated session symlink: {:?} -> {:?}", symlink_path, target_path);
+    Ok(())
 }
 
 /// Save a session continuation artifact
+/// This saves latest.json in the session's directory and updates the symlink
 pub fn save_continuation(continuation: &SessionContinuation) -> Result<PathBuf> {
-    let session_dir = ensure_session_dir()?;
-    let latest_path = session_dir.join("latest.json");
+    let session_id = &continuation.session_id;
+    let session_path = get_session_path(session_id);
     
+    // Ensure the session directory exists
+    if !session_path.exists() {
+        std::fs::create_dir_all(&session_path)
+            .context("Failed to create session directory")?;
+    }
+    
+    // Save latest.json in the session directory
+    let latest_path = session_path.join(CONTINUATION_FILENAME);
     let json = serde_json::to_string_pretty(continuation)?;
     std::fs::write(&latest_path, &json)?;
     
+    // Update the symlink to point to this session
+    update_session_symlink(session_id)?;
+    
     debug!("Saved session continuation to {:?}", latest_path);
     Ok(latest_path)
 }
 
 /// Load the latest session continuation artifact if it exists
 pub fn load_continuation() -> Result<Option<SessionContinuation>> {
-    let latest_path = get_latest_continuation_path();
+    let symlink_path = get_session_dir();
+    
+    // Check if the symlink exists and is valid
+    if !symlink_path.is_symlink() && !symlink_path.exists() {
+        debug!("No session symlink found at {:?}", symlink_path);
+        return Ok(None);
+    }
+    
+    // If it's a symlink, check if the target exists
+    if symlink_path.is_symlink() {
+        let target = std::fs::read_link(&symlink_path)?;
+        if !target.exists() && !symlink_path.exists() {
+            debug!("Session symlink target does not exist: {:?}", target);
+            return Ok(None);
+        }
+    }
+    
+    let latest_path = symlink_path.join(CONTINUATION_FILENAME);
     
     if !latest_path.exists() {
         debug!("No continuation file found at {:?}", latest_path);
@@ -117,13 +200,17 @@ pub fn load_continuation() -> Result<Option<SessionContinuation>> {
     Ok(Some(continuation))
 }
 
-/// Clear all session continuation artifacts (for /clear command)
+/// Clear the session continuation symlink (for /clear command)
+/// This only removes the symlink, not the actual session data
 pub fn clear_continuation() -> Result<()> {
-    let session_dir = get_session_dir();
+    let symlink_path = get_session_dir();
     
-    if session_dir.exists() {
-        // Remove all files in the session directory
-        for entry in std::fs::read_dir(&session_dir)? {
+    if symlink_path.is_symlink() {
+        std::fs::remove_file(&symlink_path)?;
+        debug!("Removed session symlink: {:?}", symlink_path);
+    } else if symlink_path.is_dir() {
+        // Handle old-style directory (migration case)
+        for entry in std::fs::read_dir(&symlink_path)? {
             let entry = entry?;
             let path = entry.path();
             if path.is_file() {
@@ -131,9 +218,11 @@ pub fn clear_continuation() -> Result<()> {
                 debug!("Removed session file: {:?}", path);
             }
         }
-        debug!("Cleared session continuation artifacts");
+        std::fs::remove_dir(&symlink_path)?;
+        debug!("Removed old session directory: {:?}", symlink_path);
     }
     
+    debug!("Cleared session continuation");
     Ok(())
 }
 
@@ -186,7 +275,6 @@ pub fn load_context_from_session_log(session_log_path: &Path) -> Result<Option<s
 #[cfg(test)]
 mod tests {
     use super::*;
-    use tempfile::TempDir;
 
     #[test]
     fn test_session_continuation_creation() {
diff --git a/crates/g3-core/tests/test_session_continuation.rs b/crates/g3-core/tests/test_session_continuation.rs
index 03399c9..cc2ff5a 100644
--- a/crates/g3-core/tests/test_session_continuation.rs
+++ b/crates/g3-core/tests/test_session_continuation.rs
@@ -98,6 +98,10 @@ fn test_save_and_load_continuation() {
     let saved_path = save_continuation(&original).expect("Failed to save continuation");
     assert!(saved_path.exists());
 
+    // Verify the symlink was created
+    let session_dir = get_session_dir();
+    assert!(session_dir.is_symlink(), "session should be a symlink");
+
     // Load it back
     let loaded = load_continuation()
         .expect("Failed to load continuation")
@@ -141,14 +145,15 @@ fn test_clear_continuation() {
     );
     save_continuation(&continuation).expect("Failed to save");
 
-    // Verify it exists
-    assert!(get_latest_continuation_path().exists());
+    // Verify the symlink exists
+    let session_dir = get_session_dir();
+    assert!(session_dir.is_symlink(), "session should be a symlink after save");
 
     // Clear it
     clear_continuation().expect("Failed to clear");
 
-    // Verify it's gone
-    assert!(!get_latest_continuation_path().exists());
+    // Verify the symlink is gone
+    assert!(!session_dir.exists() && !session_dir.is_symlink(), "symlink should be removed");
 
     // Loading should return None
     let result = load_continuation().expect("load should not error");
@@ -158,17 +163,23 @@ fn test_clear_continuation() {
 }
 
 #[test]
-fn test_ensure_session_dir_creates_directory() {
+fn test_ensure_session_dir_creates_g3_directory() {
     let _lock = TEST_MUTEX.lock().unwrap();
-    let (_temp_dir, original_dir) = setup_test_env();
+    let (temp_dir, original_dir) = setup_test_env();
 
-    let session_dir = get_session_dir();
-    assert!(!session_dir.exists());
+    let g3_dir = temp_dir.path().join(".g3");
+    assert!(!g3_dir.exists());
 
     ensure_session_dir().expect("Failed to ensure session dir");
 
-    assert!(session_dir.exists());
-    assert!(session_dir.is_dir());
+    // The .g3 directory should exist, but not the session symlink
+    assert!(g3_dir.exists(), ".g3 directory should be created");
+    assert!(g3_dir.is_dir(), ".g3 should be a directory");
+    
+    // The session symlink should NOT exist until save_continuation is called
+    let session_dir = get_session_dir();
+    assert!(!session_dir.exists() && !session_dir.is_symlink(), 
+            "session symlink should not exist until save_continuation is called");
 
     teardown_test_env(original_dir);
 }
@@ -257,9 +268,9 @@ fn test_continuation_serialization_format() {
 }
 
 #[test]
-fn test_multiple_saves_overwrite() {
+fn test_multiple_saves_update_symlink() {
     let _lock = TEST_MUTEX.lock().unwrap();
-    let (_temp_dir, original_dir) = setup_test_env();
+    let (temp_dir, original_dir) = setup_test_env();
 
     // Save first continuation
     let first = SessionContinuation::new(
@@ -272,7 +283,12 @@ fn test_multiple_saves_overwrite() {
     );
     save_continuation(&first).expect("Failed to save first");
 
-    // Save second continuation (should overwrite)
+    // Verify symlink points to first session
+    let session_dir = get_session_dir();
+    let first_target = fs::read_link(&session_dir).expect("Failed to read symlink");
+    assert!(first_target.to_string_lossy().contains("first_session"));
+
+    // Save second continuation (should update symlink)
     let second = SessionContinuation::new(
         "second_session".to_string(),
         Some("Second summary".to_string()),
@@ -283,6 +299,10 @@ fn test_multiple_saves_overwrite() {
     );
     save_continuation(&second).expect("Failed to save second");
 
+    // Verify symlink now points to second session
+    let second_target = fs::read_link(&session_dir).expect("Failed to read symlink");
+    assert!(second_target.to_string_lossy().contains("second_session"));
+
     // Load should return the second one
     let loaded = load_continuation()
         .expect("Failed to load")
@@ -293,5 +313,46 @@ fn test_multiple_saves_overwrite() {
         Some("Second summary".to_string())
     );
 
+    // Both session directories should exist with their own latest.json
+    let sessions_dir = temp_dir.path().join(".g3").join("sessions");
+    assert!(sessions_dir.join("first_session").join("latest.json").exists());
+    assert!(sessions_dir.join("second_session").join("latest.json").exists());
+
+    teardown_test_env(original_dir);
+}
+
+#[test]
+fn test_symlink_migration_from_old_directory() {
+    let _lock = TEST_MUTEX.lock().unwrap();
+    let (temp_dir, original_dir) = setup_test_env();
+
+    // Create an old-style .g3/session directory with latest.json
+    let old_session_dir = temp_dir.path().join(".g3").join("session");
+    fs::create_dir_all(&old_session_dir).expect("Failed to create old session dir");
+    let old_latest = old_session_dir.join("latest.json");
+    fs::write(&old_latest, r#"{"version":"1.0","session_id":"old"}"#)
+        .expect("Failed to write old latest.json");
+
+    // Save a new continuation - this should migrate the old directory to a symlink
+    let continuation = SessionContinuation::new(
+        "new_session".to_string(),
+        Some("New summary".to_string()),
+        "/path/to/session.json".to_string(),
+        50.0,
+        None,
+        ".".to_string(),
+    );
+    save_continuation(&continuation).expect("Failed to save");
+
+    // The session path should now be a symlink, not a directory
+    let session_dir = get_session_dir();
+    assert!(session_dir.is_symlink(), "session should be a symlink after migration");
+
+    // Load should return the new session
+    let loaded = load_continuation()
+        .expect("Failed to load")
+        .expect("No continuation");
+    assert_eq!(loaded.session_id, "new_session");
+
     teardown_test_env(original_dir);
 }