//! Unit tests for installation rollback functionality
//!
//! Tests cover:
//! - Rollback on failure
//! - Partial installation cleanup
//! - State restoration
//! - Transaction atomicity

use std::collections::HashMap;
use std::path::PathBuf;

#[derive(Debug, Clone)]
pub struct InstallationState {
    pub installed_files: Vec<PathBuf>,
    pub created_directories: Vec<PathBuf>,
    pub modified_configs: HashMap<String, String>,
}

#[derive(Debug, Clone, PartialEq)]
pub enum RollbackError {
    StateNotFound,
    PartialRollback,
    FileLocked,
    PermissionDenied,
}

impl std::fmt::Display for RollbackError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::StateNotFound => write!(f, "Installation state not found"),
            Self::PartialRollback => write!(f, "Partial rollback occurred"),
            Self::FileLocked => write!(f, "File is locked"),
            Self::PermissionDenied => write!(f, "Permission denied"),
        }
    }
}

impl std::error::Error for RollbackError {}

pub struct InstallationManager {
    state_stack: Vec<InstallationState>,
}

impl InstallationManager {
    pub fn new() -> Self {
        Self {
            state_stack: Vec::new(),
        }
    }

    pub fn begin_transaction(&mut self) {
        self.state_stack.push(InstallationState {
            installed_files: Vec::new(),
            created_directories: Vec::new(),
            modified_configs: HashMap::new(),
        });
    }

    pub fn record_file_install(&mut self, path: PathBuf) {
        if let Some(state) = self.state_stack.last_mut() {
            state.installed_files.push(path);
        }
    }

    pub fn record_directory_create(&mut self, path: PathBuf) {
        if let Some(state) = self.state_stack.last_mut() {
            state.created_directories.push(path);
        }
    }

    pub fn record_config_change(&mut self, key: String, old_value: String) {
        if let Some(state) = self.state_stack.last_mut() {
            state.modified_configs.insert(key, old_value);
        }
    }

    pub fn commit(&mut self) -> Result<(), RollbackError> {
        if self.state_stack.is_empty() {
            return Err(RollbackError::StateNotFound);
        }
        self.state_stack.pop();
        Ok(())
    }

    pub fn rollback(&mut self) -> Result<(), RollbackError> {
        let state = self.state_stack.pop().ok_or(RollbackError::StateNotFound)?;

        // Remove installed files (in reverse order)
        for file in state.installed_files.iter().rev() {
            // In real implementation: std::fs::remove_file(file)?
            println!("Removing file: {:?}", file);
        }

        // Remove created directories (in reverse order)
        for dir in state.created_directories.iter().rev() {
            // In real implementation: std::fs::remove_dir_all(dir)?
            println!("Removing directory: {:?}", dir);
        }

        // Restore configs
        for (key, old_value) in state.modified_configs {
            // In real implementation: restore config
            println!("Restoring config: {} = {}", key, old_value);
        }

        Ok(())
    }

    pub fn get_current_state(&self) -> Option<&InstallationState> {
        self.state_stack.last()
    }
}

// ============================================================================
// UNIT TESTS - Transaction Management
// ============================================================================

#[test]
fn test_begin_transaction() {
    let mut manager = InstallationManager::new();

    assert_eq!(manager.state_stack.len(), 0);

    manager.begin_transaction();

    assert_eq!(manager.state_stack.len(), 1);
    assert!(manager.get_current_state().is_some());
}

#[test]
fn test_commit_transaction() {
    let mut manager = InstallationManager::new();

    manager.begin_transaction();
    manager.record_file_install(PathBuf::from("/tmp/test.txt"));

    let result = manager.commit();

    assert!(result.is_ok());
    assert_eq!(manager.state_stack.len(), 0);
}

#[test]
fn test_commit_without_transaction() {
    let mut manager = InstallationManager::new();

    let result = manager.commit();

    assert!(result.is_err());
    assert_eq!(result.unwrap_err(), RollbackError::StateNotFound);
}

// ============================================================================
// UNIT TESTS - State Recording
// ============================================================================

#[test]
fn test_record_file_install() {
    let mut manager = InstallationManager::new();
    manager.begin_transaction();

    manager.record_file_install(PathBuf::from("/tmp/file1.txt"));
    manager.record_file_install(PathBuf::from("/tmp/file2.txt"));

    let state = manager.get_current_state().unwrap();
    assert_eq!(state.installed_files.len(), 2);
    assert_eq!(state.installed_files[0], PathBuf::from("/tmp/file1.txt"));
    assert_eq!(state.installed_files[1], PathBuf::from("/tmp/file2.txt"));
}

#[test]
fn test_record_directory_create() {
    let mut manager = InstallationManager::new();
    manager.begin_transaction();

    manager.record_directory_create(PathBuf::from("/tmp/dir1"));
    manager.record_directory_create(PathBuf::from("/tmp/dir2"));

    let state = manager.get_current_state().unwrap();
    assert_eq!(state.created_directories.len(), 2);
}

#[test]
fn test_record_config_change() {
    let mut manager = InstallationManager::new();
    manager.begin_transaction();

    manager.record_config_change("setting1".to_string(), "old_value1".to_string());
    manager.record_config_change("setting2".to_string(), "old_value2".to_string());

    let state = manager.get_current_state().unwrap();
    assert_eq!(state.modified_configs.len(), 2);
    assert_eq!(
        state.modified_configs.get("setting1"),
        Some(&"old_value1".to_string())
    );
}

// ============================================================================
// UNIT TESTS - Rollback Functionality
// ============================================================================

#[test]
fn test_rollback_simple() {
    let mut manager = InstallationManager::new();
    manager.begin_transaction();

    manager.record_file_install(PathBuf::from("/tmp/test.txt"));
    manager.record_directory_create(PathBuf::from("/tmp/testdir"));

    let result = manager.rollback();

    assert!(result.is_ok());
    assert_eq!(manager.state_stack.len(), 0);
}

#[test]
fn test_rollback_without_transaction() {
    let mut manager = InstallationManager::new();

    let result = manager.rollback();

    assert!(result.is_err());
    assert_eq!(result.unwrap_err(), RollbackError::StateNotFound);
}

#[test]
fn test_rollback_multiple_files() {
    let mut manager = InstallationManager::new();
    manager.begin_transaction();

    for i in 0..10 {
        manager.record_file_install(PathBuf::from(format!("/tmp/file{}.txt", i)));
    }

    let state_before = manager.get_current_state().unwrap().installed_files.len();
    assert_eq!(state_before, 10);

    let result = manager.rollback();

    assert!(result.is_ok());
    assert_eq!(manager.state_stack.len(), 0);
}

// ============================================================================
// INTEGRATION TESTS - Complete Workflow
// ============================================================================

#[test]
fn test_successful_installation_workflow() {
    let mut manager = InstallationManager::new();

    // Start transaction
    manager.begin_transaction();

    // Simulate installation steps
    manager.record_directory_create(PathBuf::from("/opt/myapp"));
    manager.record_file_install(PathBuf::from("/opt/myapp/binary"));
    manager.record_file_install(PathBuf::from("/opt/myapp/config.toml"));
    manager.record_config_change("app.enabled".to_string(), "false".to_string());

    // Verify state
    let state = manager.get_current_state().unwrap();
    assert_eq!(state.created_directories.len(), 1);
    assert_eq!(state.installed_files.len(), 2);
    assert_eq!(state.modified_configs.len(), 1);

    // Commit successful installation
    let result = manager.commit();
    assert!(result.is_ok());
}

#[test]
fn test_failed_installation_workflow_with_rollback() {
    let mut manager = InstallationManager::new();

    // Start transaction
    manager.begin_transaction();

    // Simulate partial installation
    manager.record_directory_create(PathBuf::from("/opt/myapp"));
    manager.record_file_install(PathBuf::from("/opt/myapp/binary"));

    // Simulate failure (e.g., network error, disk full)
    // Rollback to clean state
    let result = manager.rollback();
    assert!(result.is_ok());

    // State should be clean
    assert_eq!(manager.state_stack.len(), 0);
}

// ============================================================================
// NESTED TRANSACTION TESTS
// ============================================================================

#[test]
fn test_nested_transactions() {
    let mut manager = InstallationManager::new();

    // Outer transaction
    manager.begin_transaction();
    manager.record_file_install(PathBuf::from("/tmp/outer.txt"));

    // Inner transaction
    manager.begin_transaction();
    manager.record_file_install(PathBuf::from("/tmp/inner.txt"));

    // Verify stack depth
    assert_eq!(manager.state_stack.len(), 2);

    // Rollback inner
    manager.rollback().unwrap();
    assert_eq!(manager.state_stack.len(), 1);

    // Commit outer
    manager.commit().unwrap();
    assert_eq!(manager.state_stack.len(), 0);
}

// ============================================================================
// FMEA MAPPING TESTS
// ============================================================================

#[test]
fn test_fmea_installation_failure_rollback() {
    // FMEA Failure Mode: Installation failure mid-process (RPN 60)
    // Mitigation: Atomic transaction with full rollback

    let mut manager = InstallationManager::new();
    manager.begin_transaction();

    // Simulate installing 5 files before failure
    for i in 0..5 {
        manager.record_file_install(PathBuf::from(format!("/opt/app/file{}.dat", i)));
    }

    // Failure occurs (disk full, permission denied, etc.)
    // System must rollback all changes

    let result = manager.rollback();
    assert!(result.is_ok());

    // Verify system is in clean state
    assert_eq!(manager.state_stack.len(), 0);
}

#[test]
fn test_fmea_partial_installation_detection() {
    // FMEA Failure Mode: Partial installation leaves system dirty (RPN 56)
    // Mitigation: Transaction state tracking

    let mut manager = InstallationManager::new();
    manager.begin_transaction();

    manager.record_file_install(PathBuf::from("/opt/app/critical.bin"));
    manager.record_config_change("app.version".to_string(), "1.0.0".to_string());

    // System must know what needs cleanup
    let state = manager.get_current_state().unwrap();
    assert_eq!(state.installed_files.len(), 1);
    assert_eq!(state.modified_configs.len(), 1);

    // Full rollback possible
    let result = manager.rollback();
    assert!(result.is_ok());
}

#[test]
fn test_fmea_dependency_installation_atomicity() {
    // FMEA Failure Mode: Dependency installation leaves partial state (RPN 54)
    // Mitigation: Multi-package atomic transaction

    let mut manager = InstallationManager::new();

    // Install package A and its dependencies as single transaction
    manager.begin_transaction();

    // Package A
    manager.record_file_install(PathBuf::from("/opt/pkgA/bin"));

    // Dependency B
    manager.record_file_install(PathBuf::from("/opt/pkgB/lib.so"));

    // Dependency C
    manager.record_file_install(PathBuf::from("/opt/pkgC/data.db"));

    // If ANY package fails, ALL must rollback
    // Simulate failure during dependency C installation
    let result = manager.rollback();
    assert!(result.is_ok());

    // System should have no packages installed
    assert_eq!(manager.state_stack.len(), 0);
}

#[test]
fn test_fmea_config_restoration_on_failure() {
    // FMEA Failure Mode: Failed installation corrupts config files (RPN 48)
    // Mitigation: Config backup and restoration

    let mut manager = InstallationManager::new();
    manager.begin_transaction();

    // Backup original configs before modification
    manager.record_config_change("database.url".to_string(), "postgres://old".to_string());
    manager.record_config_change("cache.enabled".to_string(), "true".to_string());

    // Simulate installation failure
    let result = manager.rollback();
    assert!(result.is_ok());

    // Configs should be restored to original values
    // (in real implementation, would verify actual config file contents)
}
