runtimo-core 0.2.0

//! Backup manager for undo/rollback functionality.
//!
//! Creates timestamped backups of files and directories before mutation,
//! enabling restoration to the pre-mutation state. Backups are organized
//! under a root directory with subdirectories per job ID.
//!
//! # Security
//!
//! ## Backup Directory Symlink Check (FINDING #11)
//! The backup directory is verified to be a real directory (not a symlink)
//! during construction. This prevents an attacker from redirecting backups
//! to an arbitrary location via symlink substitution.
//!
//! ## Symlink Rejection in Copy Operations
//! The `copy_recursive` function explicitly rejects symlinks to prevent
//! symlink attack vectors. If a symlink is encountered during traversal,
//! the copy fails with an error.
//!
//! # Features
//!
//! - Supports both files and directories
//! - Preserves file permissions (including executable bit) on Unix systems
//! - Symlink rejection for security
//! - Automatic backup numbering to preserve multiple versions
//! - Pre-restore backup to prevent data loss on restore
//! - 100MB per-file backup size limit
//! - Post-copy integrity verification
//!
//! # Example
//!
//! ```rust,ignore
//! use runtimo_core::BackupManager;
//! use std::path::PathBuf;
//!
//! let mgr = BackupManager::new(PathBuf::from("/tmp/backups"));
//! let backup = mgr.create_backup(
//!     &PathBuf::from("/tmp/config.toml"),
//!     "job-abc123",
//! ).unwrap();
//!
//! // After a failed mutation, restore:
//! mgr.restore(&backup, &PathBuf::from("/tmp/config.toml")).unwrap();
//! ```

use crate::Result;
use std::path::{Path, PathBuf};

/// Maximum backup size per file/directory tree: 100MB.
const MAX_BACKUP_SIZE: u64 = 100 * 1024 * 1024;

/// Checks that a path is a real directory, not a symlink (FINDING #11).
///
/// Returns `Err` if the path is a symlink, even if the symlink target is
/// a valid directory. This prevents symlink substitution attacks.
fn verify_real_directory(path: &Path) -> Result<()> {
    if path.symlink_metadata()
        .map_err(|e| crate::Error::BackupError(format!("cannot stat {}: {}", path.display(), e)))?
        .file_type()
        .is_symlink()
    {
        return Err(crate::Error::BackupError(format!(
            "backup directory is a symlink: {} (symlink attacks not allowed)",
            path.display()
        )));
    }
    Ok(())
}

/// Manages file backups for undo/rollback operations.
///
/// Backups are stored under `{backup_dir}/{job_id}/{filename}`. The manager
/// creates directories as needed.
pub struct BackupManager {
    backup_dir: PathBuf,
}

impl BackupManager {
    /// Creates a new backup manager rooted at `backup_dir`.
    ///
    /// The directory is created (recursively) if it does not exist.
    ///
    /// # Errors
    ///
    /// Returns [`crate::Error::BackupError`] if the backup
    /// directory cannot be created.
    pub fn new(backup_dir: PathBuf) -> Result<Self> {
        std::fs::create_dir_all(&backup_dir).map_err(|e| {
            crate::Error::BackupError(format!("Failed to create backup directory: {}", e))
        })?;
        verify_real_directory(&backup_dir)?;
        Ok(Self { backup_dir })
    }

    /// Recursively copies a file or directory, rejecting symlinks for security.
    ///
    /// # Security
    ///
    /// This function explicitly rejects symlinks to prevent symlink attack vectors.
    /// If a symlink is encountered during traversal, the copy fails with an error.
    ///
    /// # Metadata
    ///
    /// Preserves file permissions (including executable bit) on Unix systems.
    /// Directory permissions are set to platform defaults.
    #[cfg(unix)]
    fn copy_permissions(src: &Path, dst: &Path) -> std::io::Result<()> {
        let src_meta = std::fs::symlink_metadata(src)?;
        std::fs::set_permissions(dst, src_meta.permissions())?;
        Ok(())
    }

    #[cfg(not(unix))]
    fn copy_permissions(_src: &Path, _dst: &Path) -> std::io::Result<()> {
        Ok(())
    }

    /// Calculates the total size of a file or directory tree.
    /// Uses symlink_metadata to avoid following symlinks.
    fn calculate_size(path: &Path) -> std::io::Result<u64> {
        let meta = path.symlink_metadata()?;
        if meta.file_type().is_symlink() {
            return Err(std::io::Error::new(
                std::io::ErrorKind::InvalidInput,
                format!("symlink detected: {} (symlinks not allowed)", path.display()),
            ));
        }
        if meta.is_file() {
            Ok(meta.len())
        } else if meta.is_dir() {
            let mut total = 0;
            for entry in std::fs::read_dir(path)? {
                let entry = entry?;
                total += Self::calculate_size(&entry.path())?;
            }
            Ok(total)
        } else {
            Ok(0)
        }
    }

    /// Verifies backup integrity by comparing source and destination sizes.
    fn verify_integrity(src: &Path, dst: &Path) -> std::io::Result<()> {
        let src_size = Self::calculate_size(src)?;
        let dst_size = Self::calculate_size(dst)?;
        if src_size != dst_size {
            return Err(std::io::Error::new(
                std::io::ErrorKind::InvalidData,
                format!(
                    "backup integrity check failed: source={} bytes, backup={} bytes",
                    src_size, dst_size
                ),
            ));
        }
        Ok(())
    }

    fn copy_recursive(src: &Path, dst: &Path) -> std::io::Result<()> {
        let metadata = src.symlink_metadata()?;
        if metadata.file_type().is_symlink() {
            return Err(std::io::Error::new(
                std::io::ErrorKind::InvalidInput,
                format!("symlink detected: {} (symlinks not allowed for security)", src.display()),
            ));
        }

        if src.is_dir() {
            std::fs::create_dir_all(dst)?;
            for entry in std::fs::read_dir(src)? {
                let entry = entry?;
                let src_path = entry.path();
                let dst_path = dst.join(entry.file_name());
                Self::copy_recursive(&src_path, &dst_path)?;
            }
            Self::copy_permissions(src, dst)?;
            Ok(())
        } else {
            std::fs::copy(src, dst)?;
            Ok(())
        }
    }

    /// Creates a backup of a file or directory before mutation.
    ///
    /// Copies `file_path` to `{backup_dir}/{job_id}/{filename}`.
    /// If a backup already exists, appends a numeric suffix (`.1`, `.2`, etc.)
    /// to preserve all pre-mutation states. The first backup (no suffix) always
    /// contains the original file state before any writes in this job.
    ///
    /// # Arguments
    ///
    /// * `file_path` — Path to the file or directory to back up
    /// * `job_id` — Job ID used as the backup subdirectory name
    ///
    /// # Returns
    ///
    /// The path to the backup file or directory.
    ///
    /// # Errors
    ///
    /// Returns [`crate::Error::BackupError`] if the source
    /// does not exist, exceeds the 100MB size limit, or the copy fails.
    pub fn create_backup(&self, file_path: &Path, job_id: &str) -> Result<PathBuf> {
        if file_path.symlink_metadata().is_err() {
            return Err(crate::Error::BackupError("File does not exist".to_string()));
        }

        let size = Self::calculate_size(file_path)
            .map_err(|e| crate::Error::BackupError(format!("Cannot calculate size: {}", e)))?;
        if size > MAX_BACKUP_SIZE {
            return Err(crate::Error::BackupError(format!(
                "Backup size {} bytes exceeds limit of {} bytes (100MB)",
                size, MAX_BACKUP_SIZE
            )));
        }

        let base_name = file_path
            .file_name()
            .ok_or_else(|| crate::Error::BackupError("Invalid filename".to_string()))?;

        let job_dir = self.backup_dir.join(job_id);
        let parent = job_dir.clone();
        std::fs::create_dir_all(&parent).map_err(|e| {
            crate::Error::BackupError(format!("Failed to create backup directory: {}", e))
        })?;

        let backup_path = {
            let candidate = job_dir.join(base_name);
            if candidate.symlink_metadata().is_err() {
                candidate
            } else {
                let mut counter = 1;
                loop {
                    let suffixed = job_dir.join(format!("{}.{}", base_name.to_string_lossy(), counter));
                    if suffixed.symlink_metadata().is_err() {
                        break suffixed;
                    }
                    counter += 1;
                }
            }
        };

        Self::copy_recursive(file_path, &backup_path)
            .map_err(|e| crate::Error::BackupError(e.to_string()))?;

        Self::verify_integrity(file_path, &backup_path)
            .map_err(|e| crate::Error::BackupError(format!("Integrity check failed: {}", e)))?;

        Ok(backup_path)
    }

    /// Restores a file or directory from a backup.
    ///
    /// Before overwriting `target_path`, creates a pre-restore backup so the
    /// current state can be recovered if the restore itself causes issues.
    /// Copies `backup_path` to `target_path`, overwriting the target.
    /// Handles both files and directories recursively.
    ///
    /// # Errors
    ///
    /// Returns [`crate::Error::BackupError`] if the backup
    /// does not exist, the pre-restore backup fails, or the copy fails.
    pub fn restore(&self, backup_path: &Path, target_path: &Path) -> Result<()> {
        if backup_path.symlink_metadata().is_err() {
            return Err(crate::Error::BackupError(
                "Backup does not exist".to_string(),
            ));
        }

        if target_path.symlink_metadata().is_ok() {
            let pre_restore_dir = target_path
                .parent()
                .map(|p| p.to_path_buf())
                .unwrap_or_else(|| PathBuf::from("."))
                .join(".runtimo_pre_restore");
            std::fs::create_dir_all(&pre_restore_dir).map_err(|e| {
                crate::Error::BackupError(format!("Cannot create pre-restore backup dir: {}", e))
            })?;
            let target_name = target_path
                .file_name()
                .unwrap_or_else(|| std::ffi::OsStr::new("target"));
            let pre_restore_path = pre_restore_dir.join(target_name);
            let _ = std::fs::remove_dir_all(&pre_restore_path);
            let _ = std::fs::remove_file(&pre_restore_path);
            Self::copy_recursive(target_path, &pre_restore_path)
                .map_err(|e| crate::Error::BackupError(format!("Pre-restore backup failed: {}", e)))?;
        }

        BackupManager::copy_recursive(backup_path, target_path)
            .map_err(|e| crate::Error::BackupError(e.to_string()))?;

        Ok(())
    }

    /// Deletes old backups older than the given age.
    ///
    /// Scans `backup_dir` for job subdirectories and removes those whose
    /// modification time is older than `older_than_secs`.
    ///
    /// # Security
    ///
    /// Uses `symlink_metadata()` to avoid following symlinks during cleanup.
    /// Symlinks are skipped rather than deleted, preventing accidental
    /// deletion of symlink targets (e.g., `remove_dir_all` on a symlink
    /// to `/etc` would be catastrophic).
    pub fn cleanup(&self, older_than_secs: u64) -> Result<()> {
        use std::time::{SystemTime, UNIX_EPOCH};

        let cutoff = SystemTime::now()
            .duration_since(UNIX_EPOCH)
            .unwrap_or_default()
            .as_secs()
            .saturating_sub(older_than_secs);

        if self.backup_dir.symlink_metadata().is_err() {
            return Ok(());
        }

        for entry in std::fs::read_dir(&self.backup_dir)
            .map_err(|e| crate::Error::BackupError(e.to_string()))?
        {
            let entry = entry.map_err(|e| crate::Error::BackupError(e.to_string()))?;
            let path = entry.path();

            let meta = path.symlink_metadata()
                .map_err(|e| crate::Error::BackupError(e.to_string()))?;
            if meta.file_type().is_symlink() {
                continue;
            }
            if !meta.is_dir() {
                continue;
            }

            let mtime = meta
                .modified()
                .map_err(|e| crate::Error::BackupError(e.to_string()))?
                .duration_since(UNIX_EPOCH)
                .unwrap_or_default()
                .as_secs();

            if mtime < cutoff {
                std::fs::remove_dir_all(&path)
                    .map_err(|e| crate::Error::BackupError(e.to_string()))?;
            }
        }

        Ok(())
    }
}

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

    #[test]
    fn test_new_creates_directory() {
        let dir = std::env::temp_dir().join("runtimo_backup_test_new");
        let _ = std::fs::remove_dir_all(&dir);
        let result = BackupManager::new(dir.clone());
        assert!(result.is_ok(), "should create directory");
        assert!(dir.exists());
        std::fs::remove_dir_all(&dir).ok();
    }

    #[test]
    fn test_rejects_symlink_backup_dir() {
        let target = std::env::temp_dir().join("runtimo_backup_target");
        let link = std::env::temp_dir().join("runtimo_backup_link");
        let _ = std::fs::remove_dir_all(&target);
        let _ = std::fs::remove_file(&link);

        std::fs::create_dir_all(&target).unwrap();

        #[cfg(unix)]
        {
            use std::os::unix::fs::symlink;
            if symlink(&target, &link).is_ok() {
                let result = BackupManager::new(link.clone());
                assert!(
                    result.is_err(),
                    "BackupManager should reject symlink backup directory"
                );
                let err = result.err().unwrap().to_string();
                assert!(err.contains("symlink"), "error should mention symlink: {}", err);
                std::fs::remove_file(&link).ok();
            }
        }

        std::fs::remove_dir_all(&target).ok();
    }

    #[test]
    fn test_verify_real_directory() {
        let dir = std::env::temp_dir().join("runtimo_verify_test");
        let _ = std::fs::remove_dir_all(&dir);
        std::fs::create_dir_all(&dir).unwrap();

        let result = verify_real_directory(&dir);
        assert!(result.is_ok(), "real directory should pass: {:?}", result);

        std::fs::remove_dir_all(&dir).ok();
    }

    #[test]
    fn test_backup_directory() {
        use crate::backup::BackupManager;

        let backup_dir = std::env::temp_dir().join("runtimo_backup_dir_test");
        let source_dir = std::env::temp_dir().join("runtimo_source_dir_test");
        let _ = std::fs::remove_dir_all(&backup_dir);
        let _ = std::fs::remove_dir_all(&source_dir);

        std::fs::create_dir_all(&source_dir).unwrap();
        std::fs::write(source_dir.join("file1.txt"), "content1").unwrap();
        std::fs::write(source_dir.join("file2.txt"), "content2").unwrap();

        let mgr = BackupManager::new(backup_dir.clone()).unwrap();
        let result = mgr.create_backup(&source_dir, "job123");

        assert!(result.is_ok(), "should backup directory: {:?}", result);
        let backup_path = result.unwrap();
        assert!(backup_path.exists());
        assert!(backup_path.join("file1.txt").exists());
        assert!(backup_path.join("file2.txt").exists());

        let content1 = std::fs::read_to_string(backup_path.join("file1.txt")).unwrap();
        assert_eq!(content1, "content1");

        std::fs::remove_dir_all(&backup_dir).ok();
        std::fs::remove_dir_all(&source_dir).ok();
    }

    #[test]
    fn test_backup_rejects_symlinks() {
        use crate::backup::BackupManager;

        let backup_dir = std::env::temp_dir().join("runtimo_backup_symlink_test");
        let source_dir = std::env::temp_dir().join("runtimo_source_symlink_test");
        let _ = std::fs::remove_dir_all(&backup_dir);
        let _ = std::fs::remove_dir_all(&source_dir);

        std::fs::create_dir_all(&source_dir).unwrap();
        std::fs::write(source_dir.join("file.txt"), "content").unwrap();

        #[cfg(unix)]
        {
            use std::os::unix::fs::symlink;
            let symlink_path = source_dir.join("evil_symlink");
            if symlink("/etc/passwd", &symlink_path).is_ok() {
                let mgr = BackupManager::new(backup_dir.clone()).unwrap();
                let result = mgr.create_backup(&source_dir, "job123");
                assert!(
                    result.is_err(),
                    "should reject directory containing symlinks"
                );
                let err = result.err().unwrap().to_string();
                assert!(err.contains("symlink"), "error should mention symlink: {}", err);
            }
        }

        std::fs::remove_dir_all(&backup_dir).ok();
        std::fs::remove_dir_all(&source_dir).ok();
    }

    #[test]
    fn test_restore_directory() {
        use crate::backup::BackupManager;

        let backup_dir = std::env::temp_dir().join("runtimo_restore_backup_test");
        let source_dir = std::env::temp_dir().join("runtimo_restore_source_test");
        let restore_dir = std::env::temp_dir().join("runtimo_restore_target_test");
        let _ = std::fs::remove_dir_all(&backup_dir);
        let _ = std::fs::remove_dir_all(&source_dir);
        let _ = std::fs::remove_dir_all(&restore_dir);

        std::fs::create_dir_all(&source_dir).unwrap();
        std::fs::write(source_dir.join("file1.txt"), "content1").unwrap();
        std::fs::write(source_dir.join("file2.txt"), "content2").unwrap();

        let mgr = BackupManager::new(backup_dir.clone()).unwrap();
        let backup_result = mgr.create_backup(&source_dir, "job123");
        assert!(backup_result.is_ok());
        let backup_path = backup_result.unwrap();

        let restore_result = mgr.restore(&backup_path, &restore_dir);
        assert!(restore_result.is_ok(), "should restore directory: {:?}", restore_result);
        assert!(restore_dir.join("file1.txt").exists());
        assert!(restore_dir.join("file2.txt").exists());

        let content1 = std::fs::read_to_string(restore_dir.join("file1.txt")).unwrap();
        assert_eq!(content1, "content1");

        std::fs::remove_dir_all(&backup_dir).ok();
        std::fs::remove_dir_all(&source_dir).ok();
        std::fs::remove_dir_all(&restore_dir).ok();
    }

    #[test]
    #[cfg(unix)]
    fn test_backup_preserves_executable_bit() {
        use crate::backup::BackupManager;
        use std::os::unix::fs::PermissionsExt;

        let backup_dir = std::env::temp_dir().join("runtimo_backup_exec_test");
        let source_dir = std::env::temp_dir().join("runtimo_source_exec_test");
        let _ = std::fs::remove_dir_all(&backup_dir);
        let _ = std::fs::remove_dir_all(&source_dir);

        std::fs::create_dir_all(&source_dir).unwrap();
        let script_path = source_dir.join("script.sh");
        std::fs::write(&script_path, "#!/bin/bash\necho hello").unwrap();
        let mut perms = std::fs::metadata(&script_path).unwrap().permissions();
        perms.set_mode(0o755);
        std::fs::set_permissions(&script_path, perms).unwrap();

        let mgr = BackupManager::new(backup_dir.clone()).unwrap();
        let result = mgr.create_backup(&source_dir, "job123");
        assert!(result.is_ok());

        let backup_path = result.unwrap();
        let backup_script = backup_path.join("script.sh");
        let backup_perms = std::fs::metadata(backup_script).unwrap().permissions();
        assert!(backup_perms.mode() & 0o111 == 0o111, "executable bit should be preserved");

        std::fs::remove_dir_all(&backup_dir).ok();
        std::fs::remove_dir_all(&source_dir).ok();
    }

    #[test]
    fn test_restore_creates_pre_restore_backup() {
        let backup_dir = std::env::temp_dir().join("runtimo_pre_restore_test");
        let source_dir = std::env::temp_dir().join("runtimo_pre_restore_source");
        let target_dir = std::env::temp_dir().join("runtimo_pre_restore_target");
        let _ = std::fs::remove_dir_all(&backup_dir);
        let _ = std::fs::remove_dir_all(&source_dir);
        let _ = std::fs::remove_dir_all(&target_dir);

        std::fs::create_dir_all(&source_dir).unwrap();
        std::fs::write(source_dir.join("original.txt"), "original").unwrap();

        std::fs::create_dir_all(&target_dir).unwrap();
        std::fs::write(target_dir.join("original.txt"), "newer_data").unwrap();

        let mgr = BackupManager::new(backup_dir.clone()).unwrap();
        let backup_path = mgr.create_backup(&source_dir, "job123").unwrap();

        let restore_result = mgr.restore(&backup_path, &target_dir);
        assert!(restore_result.is_ok());

        let content = std::fs::read_to_string(target_dir.join("original.txt")).unwrap();
        assert_eq!(content, "original");

        let pre_restore_path = target_dir
            .parent()
            .unwrap()
            .join(".runtimo_pre_restore")
            .join("runtimo_pre_restore_target");
        assert!(pre_restore_path.exists(), "pre-restore backup should exist");
        let pre_restore_content =
            std::fs::read_to_string(pre_restore_path.join("original.txt")).unwrap();
        assert_eq!(
            pre_restore_content, "newer_data",
            "pre-restore should have the newer data"
        );

        std::fs::remove_dir_all(&backup_dir).ok();
        std::fs::remove_dir_all(&source_dir).ok();
        std::fs::remove_dir_all(&target_dir).ok();
        let _ = std::fs::remove_dir_all(
            target_dir
                .parent()
                .unwrap()
                .join(".runtimo_pre_restore"),
        );
    }

    #[test]
    fn test_create_backup_size_limit_constant() {
        assert_eq!(
            MAX_BACKUP_SIZE,
            100 * 1024 * 1024,
            "MAX_BACKUP_SIZE should be 100MB"
        );

        let backup_dir = std::env::temp_dir().join("runtimo_size_limit_test");
        let source_file = std::env::temp_dir().join("runtimo_size_limit_source");
        let _ = std::fs::remove_dir_all(&backup_dir);
        let _ = std::fs::remove_file(&source_file);

        let mgr = BackupManager::new(backup_dir.clone()).unwrap();
        std::fs::write(&source_file, "small content").unwrap();
        let result = mgr.create_backup(&source_file, "job123");
        assert!(result.is_ok(), "small file should succeed");

        std::fs::remove_dir_all(&backup_dir).ok();
        std::fs::remove_file(&source_file).ok();
    }

    #[test]
    fn test_cleanup_skips_symlinks() {
        let backup_dir = std::env::temp_dir().join("runtimo_cleanup_symlink_test");
        let real_target = std::env::temp_dir().join("runtimo_cleanup_real_target");
        let _ = std::fs::remove_dir_all(&backup_dir);
        let _ = std::fs::remove_dir_all(&real_target);

        std::fs::create_dir_all(&backup_dir).unwrap();
        std::fs::create_dir_all(&real_target).unwrap();
        std::fs::write(real_target.join("important.txt"), "do not delete").unwrap();

        #[cfg(unix)]
        {
            use std::os::unix::fs::symlink;
            let symlink_path = backup_dir.join("evil_link");
            if symlink(&real_target, &symlink_path).is_ok() {
                let mgr = BackupManager::new(backup_dir.clone()).unwrap();
                let result = mgr.cleanup(0);
                assert!(
                    result.is_ok(),
                    "cleanup should succeed even with symlinks"
                );

                assert!(
                    real_target.join("important.txt").exists(),
                    "symlink target should not be deleted"
                );

                std::fs::remove_file(&symlink_path).ok();
            }
        }

        std::fs::remove_dir_all(&backup_dir).ok();
        std::fs::remove_dir_all(&real_target).ok();
    }

    #[test]
    fn test_backup_integrity_verification() {
        let backup_dir = std::env::temp_dir().join("runtimo_integrity_test");
        let source_file = std::env::temp_dir().join("runtimo_integrity_source");
        let _ = std::fs::remove_dir_all(&backup_dir);
        let _ = std::fs::remove_file(&source_file);

        std::fs::write(&source_file, "integrity test content").unwrap();

        let mgr = BackupManager::new(backup_dir.clone()).unwrap();
        let backup_path = mgr.create_backup(&source_file, "job123").unwrap();

        let src_meta = std::fs::symlink_metadata(&source_file).unwrap();
        let bak_meta = std::fs::symlink_metadata(&backup_path).unwrap();
        assert_eq!(
            src_meta.len(),
            bak_meta.len(),
            "backup size should match source"
        );

        std::fs::remove_dir_all(&backup_dir).ok();
        std::fs::remove_file(&source_file).ok();
    }
}