heartbit-core 2026.613.1

use std::future::Future;
use std::path::PathBuf;
use std::pin::Pin;
use std::sync::Arc;

use serde_json::json;

use crate::error::Error;
use crate::llm::types::ToolDefinition;
use crate::sandbox::CorePathPolicy;
use crate::tool::{Tool, ToolOutput};

use super::file_tracker::FileTracker;

/// Builtin tool that writes full file contents (create or overwrite).
///
/// Requires the target file to have been read first via `ReadTool` in the same
/// session (mtime-based guard in `FileTracker`), preventing the agent from
/// overwriting files it has never seen. Protected paths and an optional
/// `CorePathPolicy` act as additional guardrails. Prefer `EditTool` for
/// targeted in-place modifications and `PatchTool` for unified-diff patches;
/// use `WriteTool` only when creating a new file or rewriting the entire content.
pub struct WriteTool {
    file_tracker: Arc<FileTracker>,
    workspace: Option<PathBuf>,
    protected_paths: Arc<Vec<PathBuf>>,
    path_policy: Option<Arc<CorePathPolicy>>,
}

impl WriteTool {
    pub fn new(
        file_tracker: Arc<FileTracker>,
        workspace: Option<PathBuf>,
        protected_paths: Arc<Vec<PathBuf>>,
    ) -> Self {
        Self {
            file_tracker,
            workspace,
            protected_paths,
            path_policy: None,
        }
    }

    /// Set a `CorePathPolicy` that restricts file paths beyond what the
    /// workspace + protected_paths combination already enforces. The policy's
    /// `check_path` is called before any I/O.
    pub fn with_path_policy(mut self, policy: Arc<CorePathPolicy>) -> Self {
        self.path_policy = Some(policy);
        self
    }
}

impl Tool for WriteTool {
    fn definition(&self) -> ToolDefinition {
        ToolDefinition {
            name: "write".into(),
            description: "Write content to a file. Creates parent directories if needed. \
                          If the file already exists, it must have been read first (read-before-write guard)."
                .into(),
            input_schema: json!({
                "type": "object",
                "properties": {
                    "file_path": {
                        "type": "string",
                        "description": super::path_param_description(self.workspace.as_deref())
                    },
                    "content": {
                        "type": "string",
                        "description": "The content to write to the file"
                    }
                },
                "required": ["file_path", "content"]
            }),
        }
    }

    fn execute(
        &self,
        _ctx: &crate::ExecutionContext,
        input: serde_json::Value,
    ) -> Pin<Box<dyn Future<Output = Result<ToolOutput, Error>> + Send + '_>> {
        Box::pin(async move {
            let file_path = input
                .get("file_path")
                .and_then(|v| v.as_str())
                .ok_or_else(|| Error::Agent("file_path is required".into()))?;

            let content = input
                .get("content")
                .and_then(|v| v.as_str())
                .ok_or_else(|| Error::Agent("content is required".into()))?;

            let path = match super::resolve_path(
                file_path,
                self.workspace.as_deref(),
                &self.protected_paths,
            ) {
                Ok(p) => p,
                Err(msg) => return Ok(ToolOutput::error(msg)),
            };

            // SECURITY (F-FS-1): when a policy is configured, canonicalize the
            // parent and recompose `parent.canonical + filename` to get the
            // *real* target, then write it via the symlink-safe component walk
            // (`write_beneath_root`). The previous code discarded the canonical
            // path and wrote the original via `write_no_follow`, which only
            // guards the trailing component — leaving an intermediate-directory
            // symlink swap (by a parallel tool call dispatched via
            // tokio::JoinSet) able to redirect the write outside the workspace.
            let (target, write_root) = match &self.path_policy {
                Some(policy) => match policy.check_path_for_create(&path) {
                    Ok(canonical) => {
                        let root = policy
                            .allowed_root_for(&canonical)
                            .map(std::path::Path::to_path_buf);
                        (canonical, root)
                    }
                    Err(e) => return Ok(ToolOutput::error(format!("path policy: {e}"))),
                },
                None => (path.clone(), None),
            };

            // If file exists, enforce read-before-write guard
            if target.exists() {
                if let Err(msg) = self.file_tracker.check_unmodified(&target) {
                    return Ok(ToolOutput::error(msg));
                }

                // Skip write if content identical. The message is deliberately
                // emphatic: a model that keeps re-writing the same content
                // usually believes the write FAILED — when it actually
                // succeeded and the file is fine, just not where the model is
                // looking (live finding 6a25d21b: bash cwd drift made the file
                // invisible, so the model rewrote it in a doom loop).
                if let Ok(existing) = tokio::fs::read_to_string(&target).await
                    && existing == content
                {
                    return Ok(ToolOutput::success(format!(
                        "File already has EXACTLY this content — the write SUCCEEDED, \
                         nothing to do: {file_path}. Do NOT write it again. If you can't \
                         find or run it, the problem is your working directory or path, not \
                         the write — check `pwd` and use an absolute path."
                    )));
                }
            }

            let bytes = content.len();
            match write_root {
                // Policy active: symlink-safe walk from the trusted root. The
                // canonical parent already exists, so no dir creation needed.
                Some(root) => {
                    super::write_beneath_root(&root, &target, content.as_bytes())
                        .await
                        .map_err(|e| Error::Agent(format!("Cannot write file: {e}")))?;
                }
                // No policy: preserve prior behaviour (create parents, then
                // O_NOFOLLOW write of the trailing component).
                None => {
                    if let Some(parent) = target.parent()
                        && !parent.exists()
                    {
                        tokio::fs::create_dir_all(parent)
                            .await
                            .map_err(|e| Error::Agent(format!("Cannot create directories: {e}")))?;
                    }
                    super::write_no_follow(&target, content.as_bytes())
                        .await
                        .map_err(|e| Error::Agent(format!("Cannot write file: {e}")))?;
                }
            }

            // Update tracker (so subsequent edits pass the guard)
            let _ = self.file_tracker.record_read(&target);

            Ok(ToolOutput::success(format!(
                "File written: {file_path} ({bytes} bytes)"
            )))
        })
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn definition_has_correct_name() {
        let tracker = Arc::new(FileTracker::new());
        let tool = WriteTool::new(tracker, None, Arc::new(Vec::new()));
        assert_eq!(tool.definition().name, "write");
    }

    // The path description must match the actual policy: with a workspace set,
    // absolute paths are REJECTED — the old "Absolute path, or relative to
    // workspace" wording actively invited the failure (live /analyze finding:
    // an agent burned 7 tool errors trying absolute /tmp paths).
    #[test]
    fn path_description_matches_workspace_policy() {
        let tracker = Arc::new(FileTracker::new());
        let sandboxed = WriteTool::new(
            tracker.clone(),
            Some(std::path::PathBuf::from("/ws")),
            Arc::new(Vec::new()),
        );
        let desc = sandboxed.definition().input_schema["properties"]["file_path"]["description"]
            .as_str()
            .unwrap()
            .to_string();
        assert!(
            desc.contains("relative to the workspace") && desc.contains("rejected"),
            "workspace-set description must warn absolute is rejected: {desc}"
        );
        let open = WriteTool::new(tracker, None, Arc::new(Vec::new()));
        let desc = open.definition().input_schema["properties"]["file_path"]["description"]
            .as_str()
            .unwrap()
            .to_string();
        assert!(
            desc.contains("Absolute"),
            "no-workspace description allows absolute: {desc}"
        );
    }

    #[tokio::test]
    async fn write_new_file() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("new.txt");

        let tracker = Arc::new(FileTracker::new());
        let tool = WriteTool::new(tracker.clone(), None, Arc::new(Vec::new()));

        let result = tool
            .execute(
                &crate::ExecutionContext::default(),
                json!({"file_path": path.to_str().unwrap(), "content": "hello world"}),
            )
            .await
            .unwrap();
        assert!(!result.is_error);
        assert!(result.content.contains("File written"));
        assert!(result.content.contains("11 bytes"));

        // Verify content
        let written = std::fs::read_to_string(&path).unwrap();
        assert_eq!(written, "hello world");

        // File should be tracked
        assert!(tracker.was_read(&path));
    }

    #[tokio::test]
    async fn write_creates_parent_dirs() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("sub").join("deep").join("file.txt");

        let tracker = Arc::new(FileTracker::new());
        let tool = WriteTool::new(tracker, None, Arc::new(Vec::new()));

        let result = tool
            .execute(
                &crate::ExecutionContext::default(),
                json!({"file_path": path.to_str().unwrap(), "content": "nested"}),
            )
            .await
            .unwrap();
        assert!(!result.is_error);
        assert_eq!(std::fs::read_to_string(&path).unwrap(), "nested");
    }

    #[tokio::test]
    async fn write_existing_file_requires_read_first() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("existing.txt");
        std::fs::write(&path, "original").unwrap();

        let tracker = Arc::new(FileTracker::new());
        let tool = WriteTool::new(tracker, None, Arc::new(Vec::new()));

        // Try to write without reading first
        let result = tool
            .execute(
                &crate::ExecutionContext::default(),
                json!({"file_path": path.to_str().unwrap(), "content": "new content"}),
            )
            .await
            .unwrap();
        assert!(result.is_error);
        assert!(result.content.contains("has not been read yet"));
    }

    #[tokio::test]
    async fn write_skips_when_content_identical() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("same.txt");
        std::fs::write(&path, "same content").unwrap();

        let tracker = Arc::new(FileTracker::new());
        tracker.record_read(&path).unwrap();

        let tool = WriteTool::new(tracker, None, Arc::new(Vec::new()));
        let result = tool
            .execute(
                &crate::ExecutionContext::default(),
                json!({"file_path": path.to_str().unwrap(), "content": "same content"}),
            )
            .await
            .unwrap();
        assert!(!result.is_error);
        // Emphatic "already succeeded" message (anti doom-loop, finding 6a25d21b).
        assert!(result.content.contains("write SUCCEEDED"));
        assert!(result.content.contains("Do NOT write it again"));
    }

    #[tokio::test]
    async fn write_existing_file_after_read() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("existing.txt");
        std::fs::write(&path, "original").unwrap();

        let tracker = Arc::new(FileTracker::new());
        tracker.record_read(&path).unwrap();

        let tool = WriteTool::new(tracker, None, Arc::new(Vec::new()));
        let result = tool
            .execute(
                &crate::ExecutionContext::default(),
                json!({"file_path": path.to_str().unwrap(), "content": "updated"}),
            )
            .await
            .unwrap();
        assert!(!result.is_error);
        assert_eq!(std::fs::read_to_string(&path).unwrap(), "updated");
    }

    #[tokio::test]
    async fn write_tool_rejects_path_outside_policy() {
        use crate::sandbox::CorePathPolicy;

        let allowed = tempfile::tempdir().unwrap();
        let outside = tempfile::tempdir().unwrap();
        let policy = Arc::new(
            CorePathPolicy::builder()
                .allow_dir(allowed.path())
                .build()
                .unwrap(),
        );

        // No workspace — absolute paths are accepted by resolve_path
        let tool = WriteTool::new(Arc::new(FileTracker::new()), None, Arc::new(Vec::new()))
            .with_path_policy(policy);

        let target = outside.path().join("evil.txt");
        let result = tool
            .execute(
                &crate::ExecutionContext::default(),
                serde_json::json!({
                    "file_path": target.to_string_lossy(),
                    "content": "x"
                }),
            )
            .await
            .unwrap();
        assert!(
            result.is_error,
            "expected sandbox violation, got: {:?}",
            result.content
        );
        assert!(
            result.content.contains("path policy"),
            "expected path policy error, got: {:?}",
            result.content
        );
    }

    #[tokio::test]
    async fn write_tool_allows_path_inside_policy() {
        use crate::sandbox::CorePathPolicy;

        let allowed = tempfile::tempdir().unwrap();
        let policy = Arc::new(
            CorePathPolicy::builder()
                .allow_dir(allowed.path())
                .build()
                .unwrap(),
        );

        // No workspace — absolute paths are accepted by resolve_path
        let tool = WriteTool::new(Arc::new(FileTracker::new()), None, Arc::new(Vec::new()))
            .with_path_policy(policy);

        let target = allowed.path().join("ok.txt");
        let result = tool
            .execute(
                &crate::ExecutionContext::default(),
                serde_json::json!({
                    "file_path": target.to_string_lossy(),
                    "content": "x"
                }),
            )
            .await
            .unwrap();
        assert!(
            !result.is_error,
            "expected success, got: {:?}",
            result.content
        );
    }

    /// SECURITY (F-FS-1): if the target path is a symlink pointing outside the
    /// allowed directory, the open syscall must fail with `O_NOFOLLOW` rather
    /// than follow the link and write through it. This protects against TOCTOU
    /// where a parallel tool call swaps in a symlink between policy check and
    /// open.
    #[cfg(unix)]
    #[tokio::test]
    async fn write_refuses_to_follow_symlink_pointing_outside_workspace() {
        use crate::sandbox::CorePathPolicy;
        use std::os::unix::fs::symlink;

        let allowed = tempfile::tempdir().unwrap();
        let outside = tempfile::tempdir().unwrap();

        // Create a "victim" file that the LLM should NOT be able to overwrite.
        let victim = outside.path().join("victim.txt");
        std::fs::write(&victim, "ORIGINAL CONTENT").unwrap();

        // Inside the allowed dir, create a symlink pointing to the victim file.
        let link = allowed.path().join("link.txt");
        symlink(&victim, &link).unwrap();

        let policy = Arc::new(
            CorePathPolicy::builder()
                .allow_dir(allowed.path())
                .build()
                .unwrap(),
        );
        let tracker = Arc::new(FileTracker::new());
        // Must record the symlink target as read so the read-before-write
        // guard doesn't preempt the security check we are testing.
        let _ = tracker.record_read(&link);
        let tool = WriteTool::new(tracker, None, Arc::new(Vec::new())).with_path_policy(policy);

        // Attempt to overwrite via the symlink path — must fail. The error
        // can surface as either `Err(Error::Agent("Cannot write file: ..."))`
        // (from the failed open syscall propagating up through `?`) or as
        // `Ok(ToolOutput::error)` from the policy reject. Both prove the
        // security invariant; the victim file must remain untouched.
        let outcome = tool
            .execute(
                &crate::ExecutionContext::default(),
                serde_json::json!({
                    "file_path": link.to_string_lossy(),
                    "content": "PWNED"
                }),
            )
            .await;
        match outcome {
            Ok(r) => assert!(
                r.is_error,
                "expected error tool output; got success: {:?}",
                r.content
            ),
            Err(e) => {
                let s = e.to_string().to_lowercase();
                assert!(
                    s.contains("symbolic")
                        || s.contains("symlink")
                        || s.contains("nofollow")
                        || s.contains("loop"),
                    "expected symlink-related error; got: {e}"
                );
            }
        }

        // Victim must remain untouched — that's the security invariant.
        let after = std::fs::read_to_string(&victim).unwrap();
        assert_eq!(
            after, "ORIGINAL CONTENT",
            "victim file was modified despite symlink rejection"
        );
    }

    // SECURITY (F-FS-1): end-to-end through WriteTool. An INTERMEDIATE
    // directory swapped for a symlink (the TOCTOU that O_NOFOLLOW-on-the-final-
    // component alone misses) must be refused and must not write outside the
    // workspace. Before the fix the canonical target was discarded and the
    // original path written via write_no_follow, letting the write escape.
    #[cfg(unix)]
    #[tokio::test]
    async fn write_tool_refuses_intermediate_symlink_escape() {
        use crate::sandbox::CorePathPolicy;
        use std::os::unix::fs::symlink;

        let allowed = tempfile::tempdir().unwrap();
        let outside = tempfile::tempdir().unwrap();
        let allowed_c = allowed.path().canonicalize().unwrap();
        let outside_c = outside.path().canonicalize().unwrap();

        // A real intermediate dir inside the workspace, swapped for a symlink
        // pointing outside it.
        std::fs::create_dir(allowed_c.join("sub")).unwrap();
        std::fs::remove_dir(allowed_c.join("sub")).unwrap();
        symlink(&outside_c, allowed_c.join("sub")).unwrap();

        let policy = Arc::new(
            CorePathPolicy::builder()
                .allow_dir(&allowed_c)
                .build()
                .unwrap(),
        );
        let tool = WriteTool::new(Arc::new(FileTracker::new()), None, Arc::new(Vec::new()))
            .with_path_policy(policy);

        let target = allowed_c.join("sub/evil.txt");
        let outcome = tool
            .execute(
                &crate::ExecutionContext::default(),
                serde_json::json!({
                    "file_path": target.to_string_lossy(),
                    "content": "PWNED"
                }),
            )
            .await;
        // Either a policy reject (Ok error) or a failed open (Err) — both prove
        // the invariant. The decisive assertion is that nothing escaped.
        if let Ok(r) = outcome {
            assert!(r.is_error, "expected error; got success: {:?}", r.content);
        }
        assert!(
            !outside_c.join("evil.txt").exists(),
            "write escaped the workspace through a symlinked intermediate dir"
        );
    }
}