sal-postgresclient 0.1.0

use lazy_static::lazy_static;
use postgres::types::ToSql;
use postgres::{Client, Error as PostgresError, NoTls, Row};
use r2d2::Pool;
use r2d2_postgres::PostgresConnectionManager;
use std::env;
use std::sync::{Arc, Mutex, Once};
use std::time::Duration;

// Helper function to create a PostgreSQL error
fn create_postgres_error(_message: &str) -> PostgresError {
    // Since we can't directly create a PostgresError, we'll create one by
    // attempting to connect to an invalid connection string and capturing the error
    let result = Client::connect("invalid-connection-string", NoTls);
    match result {
        Ok(_) => unreachable!(), // This should never happen
        Err(e) => {
            // We have a valid PostgresError now, but we want to customize the message
            // Unfortunately, PostgresError doesn't provide a way to modify the message
            // So we'll just return the error we got
            e
        }
    }
}

// Global PostgreSQL client instance using lazy_static
lazy_static! {
    static ref POSTGRES_CLIENT: Mutex<Option<Arc<PostgresClientWrapper>>> = Mutex::new(None);
    static ref POSTGRES_POOL: Mutex<Option<Arc<Pool<PostgresConnectionManager<NoTls>>>>> =
        Mutex::new(None);
    static ref INIT: Once = Once::new();
}

/// PostgreSQL connection configuration builder
///
/// This struct is used to build a PostgreSQL connection configuration.
/// It follows the builder pattern to allow for flexible configuration.
#[derive(Debug)]
pub struct PostgresConfigBuilder {
    pub host: String,
    pub port: u16,
    pub user: String,
    pub password: Option<String>,
    pub database: String,
    pub application_name: Option<String>,
    pub connect_timeout: Option<u64>,
    pub ssl_mode: Option<String>,
    // Connection pool settings
    pub pool_max_size: Option<u32>,
    pub pool_min_idle: Option<u32>,
    pub pool_idle_timeout: Option<Duration>,
    pub pool_connection_timeout: Option<Duration>,
    pub pool_max_lifetime: Option<Duration>,
    pub use_pool: bool,
}

impl Default for PostgresConfigBuilder {
    fn default() -> Self {
        Self {
            host: "localhost".to_string(),
            port: 5432,
            user: "postgres".to_string(),
            password: None,
            database: "postgres".to_string(),
            application_name: None,
            connect_timeout: None,
            ssl_mode: None,
            // Default pool settings
            pool_max_size: Some(10),
            pool_min_idle: Some(1),
            pool_idle_timeout: Some(Duration::from_secs(300)),
            pool_connection_timeout: Some(Duration::from_secs(30)),
            pool_max_lifetime: Some(Duration::from_secs(1800)),
            use_pool: false,
        }
    }
}

impl PostgresConfigBuilder {
    /// Create a new PostgreSQL connection configuration builder with default values
    pub fn new() -> Self {
        Self::default()
    }

    /// Set the host for the PostgreSQL connection
    pub fn host(mut self, host: &str) -> Self {
        self.host = host.to_string();
        self
    }

    /// Set the port for the PostgreSQL connection
    pub fn port(mut self, port: u16) -> Self {
        self.port = port;
        self
    }

    /// Set the user for the PostgreSQL connection
    pub fn user(mut self, user: &str) -> Self {
        self.user = user.to_string();
        self
    }

    /// Set the password for the PostgreSQL connection
    pub fn password(mut self, password: &str) -> Self {
        self.password = Some(password.to_string());
        self
    }

    /// Set the database for the PostgreSQL connection
    pub fn database(mut self, database: &str) -> Self {
        self.database = database.to_string();
        self
    }

    /// Set the application name for the PostgreSQL connection
    pub fn application_name(mut self, application_name: &str) -> Self {
        self.application_name = Some(application_name.to_string());
        self
    }

    /// Set the connection timeout in seconds
    pub fn connect_timeout(mut self, seconds: u64) -> Self {
        self.connect_timeout = Some(seconds);
        self
    }

    /// Set the SSL mode for the PostgreSQL connection
    pub fn ssl_mode(mut self, ssl_mode: &str) -> Self {
        self.ssl_mode = Some(ssl_mode.to_string());
        self
    }

    /// Enable connection pooling
    pub fn use_pool(mut self, use_pool: bool) -> Self {
        self.use_pool = use_pool;
        self
    }

    /// Set the maximum size of the connection pool
    pub fn pool_max_size(mut self, size: u32) -> Self {
        self.pool_max_size = Some(size);
        self
    }

    /// Set the minimum number of idle connections in the pool
    pub fn pool_min_idle(mut self, size: u32) -> Self {
        self.pool_min_idle = Some(size);
        self
    }

    /// Set the idle timeout for connections in the pool
    pub fn pool_idle_timeout(mut self, timeout: Duration) -> Self {
        self.pool_idle_timeout = Some(timeout);
        self
    }

    /// Set the connection timeout for the pool
    pub fn pool_connection_timeout(mut self, timeout: Duration) -> Self {
        self.pool_connection_timeout = Some(timeout);
        self
    }

    /// Set the maximum lifetime of connections in the pool
    pub fn pool_max_lifetime(mut self, lifetime: Duration) -> Self {
        self.pool_max_lifetime = Some(lifetime);
        self
    }

    /// Build the connection string from the configuration
    pub fn build_connection_string(&self) -> String {
        let mut conn_string = format!(
            "host={} port={} user={} dbname={}",
            self.host, self.port, self.user, self.database
        );

        if let Some(password) = &self.password {
            conn_string.push_str(&format!(" password={}", password));
        }

        if let Some(app_name) = &self.application_name {
            conn_string.push_str(&format!(" application_name={}", app_name));
        }

        if let Some(timeout) = self.connect_timeout {
            conn_string.push_str(&format!(" connect_timeout={}", timeout));
        }

        if let Some(ssl_mode) = &self.ssl_mode {
            conn_string.push_str(&format!(" sslmode={}", ssl_mode));
        }

        conn_string
    }

    /// Build a PostgreSQL client from the configuration
    pub fn build(&self) -> Result<Client, PostgresError> {
        let conn_string = self.build_connection_string();
        Client::connect(&conn_string, NoTls)
    }

    /// Build a PostgreSQL connection pool from the configuration
    pub fn build_pool(&self) -> Result<Pool<PostgresConnectionManager<NoTls>>, r2d2::Error> {
        let conn_string = self.build_connection_string();
        let manager = PostgresConnectionManager::new(conn_string.parse().unwrap(), NoTls);

        let mut pool_builder = r2d2::Pool::builder();

        if let Some(max_size) = self.pool_max_size {
            pool_builder = pool_builder.max_size(max_size);
        }

        if let Some(min_idle) = self.pool_min_idle {
            pool_builder = pool_builder.min_idle(Some(min_idle));
        }

        if let Some(idle_timeout) = self.pool_idle_timeout {
            pool_builder = pool_builder.idle_timeout(Some(idle_timeout));
        }

        if let Some(connection_timeout) = self.pool_connection_timeout {
            pool_builder = pool_builder.connection_timeout(connection_timeout);
        }

        if let Some(max_lifetime) = self.pool_max_lifetime {
            pool_builder = pool_builder.max_lifetime(Some(max_lifetime));
        }

        pool_builder.build(manager)
    }
}

/// Wrapper for PostgreSQL client to handle connection
pub struct PostgresClientWrapper {
    connection_string: String,
    client: Mutex<Option<Client>>,
}

/// Transaction functions for PostgreSQL
///
/// These functions provide a way to execute queries within a transaction.
/// The transaction is automatically committed when the function returns successfully,
/// or rolled back if an error occurs.
///
/// Example:
/// ```no_run
/// use sal_postgresclient::{transaction, QueryParams};
///
/// let result = transaction(|client| {
///     // Execute queries within the transaction
///     client.execute("INSERT INTO users (name) VALUES ($1)", &[&"John"])?;
///     client.execute("UPDATE users SET active = true WHERE name = $1", &[&"John"])?;
///
///     // Return a result from the transaction
///     Ok(())
/// });
/// ```
pub fn transaction<F, T>(operations: F) -> Result<T, PostgresError>
where
    F: FnOnce(&mut Client) -> Result<T, PostgresError>,
{
    let client = get_postgres_client()?;
    let client_mutex = client.get_client()?;
    let mut client_guard = client_mutex.lock().unwrap();

    if let Some(client) = client_guard.as_mut() {
        // Begin transaction
        client.execute("BEGIN", &[])?;

        // Execute operations
        match operations(client) {
            Ok(result) => {
                // Commit transaction
                client.execute("COMMIT", &[])?;
                Ok(result)
            }
            Err(e) => {
                // Rollback transaction
                let _ = client.execute("ROLLBACK", &[]);
                Err(e)
            }
        }
    } else {
        Err(create_postgres_error("Failed to get PostgreSQL client"))
    }
}

/// Transaction functions for PostgreSQL using the connection pool
///
/// These functions provide a way to execute queries within a transaction using the connection pool.
/// The transaction is automatically committed when the function returns successfully,
/// or rolled back if an error occurs.
///
/// Example:
/// ```no_run
/// use sal_postgresclient::{transaction_with_pool, QueryParams};
///
/// let result = transaction_with_pool(|client| {
///     // Execute queries within the transaction
///     client.execute("INSERT INTO users (name) VALUES ($1)", &[&"John"])?;
///     client.execute("UPDATE users SET active = true WHERE name = $1", &[&"John"])?;
///
///     // Return a result from the transaction
///     Ok(())
/// });
/// ```
pub fn transaction_with_pool<F, T>(operations: F) -> Result<T, PostgresError>
where
    F: FnOnce(&mut Client) -> Result<T, PostgresError>,
{
    let pool = get_postgres_pool()?;
    let mut client = pool.get().map_err(|e| {
        create_postgres_error(&format!("Failed to get connection from pool: {}", e))
    })?;

    // Begin transaction
    client.execute("BEGIN", &[])?;

    // Execute operations
    match operations(&mut client) {
        Ok(result) => {
            // Commit transaction
            client.execute("COMMIT", &[])?;
            Ok(result)
        }
        Err(e) => {
            // Rollback transaction
            let _ = client.execute("ROLLBACK", &[]);
            Err(e)
        }
    }
}

impl PostgresClientWrapper {
    /// Create a new PostgreSQL client wrapper
    fn new(connection_string: String) -> Self {
        PostgresClientWrapper {
            connection_string,
            client: Mutex::new(None),
        }
    }

    /// Get a reference to the PostgreSQL client, creating it if it doesn't exist
    fn get_client(&self) -> Result<&Mutex<Option<Client>>, PostgresError> {
        let mut client_guard = self.client.lock().unwrap();

        // If we don't have a client or it's not working, create a new one
        if client_guard.is_none() {
            *client_guard = Some(Client::connect(&self.connection_string, NoTls)?);
        }

        Ok(&self.client)
    }

    /// Execute a query on the PostgreSQL connection
    pub fn execute(
        &self,
        query: &str,
        params: &[&(dyn postgres::types::ToSql + Sync)],
    ) -> Result<u64, PostgresError> {
        let client_mutex = self.get_client()?;
        let mut client_guard = client_mutex.lock().unwrap();

        if let Some(client) = client_guard.as_mut() {
            client.execute(query, params)
        } else {
            Err(create_postgres_error("Failed to get PostgreSQL client"))
        }
    }

    /// Execute a query on the PostgreSQL connection and return the rows
    pub fn query(
        &self,
        query: &str,
        params: &[&(dyn postgres::types::ToSql + Sync)],
    ) -> Result<Vec<Row>, PostgresError> {
        let client_mutex = self.get_client()?;
        let mut client_guard = client_mutex.lock().unwrap();

        if let Some(client) = client_guard.as_mut() {
            client.query(query, params)
        } else {
            Err(create_postgres_error("Failed to get PostgreSQL client"))
        }
    }

    /// Execute a query on the PostgreSQL connection and return a single row
    pub fn query_one(
        &self,
        query: &str,
        params: &[&(dyn postgres::types::ToSql + Sync)],
    ) -> Result<Row, PostgresError> {
        let client_mutex = self.get_client()?;
        let mut client_guard = client_mutex.lock().unwrap();

        if let Some(client) = client_guard.as_mut() {
            client.query_one(query, params)
        } else {
            Err(create_postgres_error("Failed to get PostgreSQL client"))
        }
    }

    /// Execute a query on the PostgreSQL connection and return an optional row
    pub fn query_opt(
        &self,
        query: &str,
        params: &[&(dyn postgres::types::ToSql + Sync)],
    ) -> Result<Option<Row>, PostgresError> {
        let client_mutex = self.get_client()?;
        let mut client_guard = client_mutex.lock().unwrap();

        if let Some(client) = client_guard.as_mut() {
            client.query_opt(query, params)
        } else {
            Err(create_postgres_error("Failed to get PostgreSQL client"))
        }
    }

    /// Ping the PostgreSQL server to check if the connection is alive
    pub fn ping(&self) -> Result<bool, PostgresError> {
        let result = self.query("SELECT 1", &[]);
        match result {
            Ok(_) => Ok(true),
            Err(e) => Err(e),
        }
    }
}

/// Get the PostgreSQL client instance
pub fn get_postgres_client() -> Result<Arc<PostgresClientWrapper>, PostgresError> {
    // Check if we already have a client
    {
        let guard = POSTGRES_CLIENT.lock().unwrap();
        if let Some(ref client) = &*guard {
            return Ok(Arc::clone(client));
        }
    }

    // Create a new client
    let client = create_postgres_client()?;

    // Store the client globally
    {
        let mut guard = POSTGRES_CLIENT.lock().unwrap();
        *guard = Some(Arc::clone(&client));
    }

    Ok(client)
}

/// Create a new PostgreSQL client
fn create_postgres_client() -> Result<Arc<PostgresClientWrapper>, PostgresError> {
    // Try to get connection details from environment variables
    let host = env::var("POSTGRES_HOST").unwrap_or_else(|_| String::from("localhost"));
    let port = env::var("POSTGRES_PORT")
        .ok()
        .and_then(|p| p.parse::<u16>().ok())
        .unwrap_or(5432);
    let user = env::var("POSTGRES_USER").unwrap_or_else(|_| String::from("postgres"));
    let password = env::var("POSTGRES_PASSWORD").ok();
    let database = env::var("POSTGRES_DB").unwrap_or_else(|_| String::from("postgres"));

    // Build the connection string
    let mut builder = PostgresConfigBuilder::new()
        .host(&host)
        .port(port)
        .user(&user)
        .database(&database);

    if let Some(pass) = password {
        builder = builder.password(&pass);
    }

    let connection_string = builder.build_connection_string();

    // Create the client wrapper
    let wrapper = Arc::new(PostgresClientWrapper::new(connection_string));

    // Test the connection
    match wrapper.ping() {
        Ok(_) => Ok(wrapper),
        Err(e) => Err(e),
    }
}

/// Reset the PostgreSQL client
pub fn reset() -> Result<(), PostgresError> {
    // Clear the existing client
    {
        let mut client_guard = POSTGRES_CLIENT.lock().unwrap();
        *client_guard = None;
    }

    // Create a new client, only return error if it fails
    get_postgres_client()?;
    Ok(())
}

/// Execute a query on the PostgreSQL connection
pub fn execute(
    query: &str,
    params: &[&(dyn postgres::types::ToSql + Sync)],
) -> Result<u64, PostgresError> {
    let client = get_postgres_client()?;
    client.execute(query, params)
}

/// Execute a query on the PostgreSQL connection and return the rows
pub fn query(
    query: &str,
    params: &[&(dyn postgres::types::ToSql + Sync)],
) -> Result<Vec<Row>, PostgresError> {
    let client = get_postgres_client()?;
    client.query(query, params)
}

/// Execute a query on the PostgreSQL connection and return a single row
pub fn query_one(
    query: &str,
    params: &[&(dyn postgres::types::ToSql + Sync)],
) -> Result<Row, PostgresError> {
    let client = get_postgres_client()?;
    client.query_one(query, params)
}

/// Execute a query on the PostgreSQL connection and return an optional row
pub fn query_opt(
    query: &str,
    params: &[&(dyn postgres::types::ToSql + Sync)],
) -> Result<Option<Row>, PostgresError> {
    let client = get_postgres_client()?;
    client.query_opt(query, params)
}

/// Create a new PostgreSQL client with custom configuration
pub fn with_config(config: PostgresConfigBuilder) -> Result<Client, PostgresError> {
    config.build()
}

/// Create a new PostgreSQL connection pool with custom configuration
pub fn with_pool_config(
    config: PostgresConfigBuilder,
) -> Result<Pool<PostgresConnectionManager<NoTls>>, r2d2::Error> {
    config.build_pool()
}

/// Get the PostgreSQL connection pool instance
pub fn get_postgres_pool() -> Result<Arc<Pool<PostgresConnectionManager<NoTls>>>, PostgresError> {
    // Check if we already have a pool
    {
        let guard = POSTGRES_POOL.lock().unwrap();
        if let Some(ref pool) = &*guard {
            return Ok(Arc::clone(pool));
        }
    }

    // Create a new pool
    let pool = create_postgres_pool()?;

    // Store the pool globally
    {
        let mut guard = POSTGRES_POOL.lock().unwrap();
        *guard = Some(Arc::clone(&pool));
    }

    Ok(pool)
}

/// Create a new PostgreSQL connection pool
fn create_postgres_pool() -> Result<Arc<Pool<PostgresConnectionManager<NoTls>>>, PostgresError> {
    // Try to get connection details from environment variables
    let host = env::var("POSTGRES_HOST").unwrap_or_else(|_| String::from("localhost"));
    let port = env::var("POSTGRES_PORT")
        .ok()
        .and_then(|p| p.parse::<u16>().ok())
        .unwrap_or(5432);
    let user = env::var("POSTGRES_USER").unwrap_or_else(|_| String::from("postgres"));
    let password = env::var("POSTGRES_PASSWORD").ok();
    let database = env::var("POSTGRES_DB").unwrap_or_else(|_| String::from("postgres"));

    // Build the configuration
    let mut builder = PostgresConfigBuilder::new()
        .host(&host)
        .port(port)
        .user(&user)
        .database(&database)
        .use_pool(true);

    if let Some(pass) = password {
        builder = builder.password(&pass);
    }

    // Create the pool
    match builder.build_pool() {
        Ok(pool) => {
            // Test the connection
            match pool.get() {
                Ok(_) => Ok(Arc::new(pool)),
                Err(e) => Err(create_postgres_error(&format!(
                    "Failed to connect to PostgreSQL: {}",
                    e
                ))),
            }
        }
        Err(e) => Err(create_postgres_error(&format!(
            "Failed to create PostgreSQL connection pool: {}",
            e
        ))),
    }
}

/// Reset the PostgreSQL connection pool
pub fn reset_pool() -> Result<(), PostgresError> {
    // Clear the existing pool
    {
        let mut pool_guard = POSTGRES_POOL.lock().unwrap();
        *pool_guard = None;
    }

    // Create a new pool, only return error if it fails
    get_postgres_pool()?;
    Ok(())
}

/// Execute a query using the connection pool
pub fn execute_with_pool(
    query: &str,
    params: &[&(dyn postgres::types::ToSql + Sync)],
) -> Result<u64, PostgresError> {
    let pool = get_postgres_pool()?;
    let mut client = pool.get().map_err(|e| {
        create_postgres_error(&format!("Failed to get connection from pool: {}", e))
    })?;
    client.execute(query, params)
}

/// Execute a query using the connection pool and return the rows
pub fn query_with_pool(
    query: &str,
    params: &[&(dyn postgres::types::ToSql + Sync)],
) -> Result<Vec<Row>, PostgresError> {
    let pool = get_postgres_pool()?;
    let mut client = pool.get().map_err(|e| {
        create_postgres_error(&format!("Failed to get connection from pool: {}", e))
    })?;
    client.query(query, params)
}

/// Execute a query using the connection pool and return a single row
pub fn query_one_with_pool(
    query: &str,
    params: &[&(dyn postgres::types::ToSql + Sync)],
) -> Result<Row, PostgresError> {
    let pool = get_postgres_pool()?;
    let mut client = pool.get().map_err(|e| {
        create_postgres_error(&format!("Failed to get connection from pool: {}", e))
    })?;
    client.query_one(query, params)
}

/// Execute a query using the connection pool and return an optional row
pub fn query_opt_with_pool(
    query: &str,
    params: &[&(dyn postgres::types::ToSql + Sync)],
) -> Result<Option<Row>, PostgresError> {
    let pool = get_postgres_pool()?;
    let mut client = pool.get().map_err(|e| {
        create_postgres_error(&format!("Failed to get connection from pool: {}", e))
    })?;
    client.query_opt(query, params)
}

/// Parameter builder for PostgreSQL queries
///
/// This struct helps build parameterized queries for PostgreSQL.
/// It provides a type-safe way to build query parameters.
#[derive(Default)]
pub struct QueryParams {
    params: Vec<Box<dyn ToSql + Sync>>,
}

impl QueryParams {
    /// Create a new empty parameter builder
    pub fn new() -> Self {
        Self { params: Vec::new() }
    }

    /// Add a parameter to the builder
    pub fn add<T: 'static + ToSql + Sync>(&mut self, value: T) -> &mut Self {
        self.params.push(Box::new(value));
        self
    }

    /// Add a string parameter to the builder
    pub fn add_str(&mut self, value: &str) -> &mut Self {
        self.add(value.to_string())
    }

    /// Add an integer parameter to the builder
    pub fn add_int(&mut self, value: i32) -> &mut Self {
        self.add(value)
    }

    /// Add a float parameter to the builder
    pub fn add_float(&mut self, value: f64) -> &mut Self {
        self.add(value)
    }

    /// Add a boolean parameter to the builder
    pub fn add_bool(&mut self, value: bool) -> &mut Self {
        self.add(value)
    }

    /// Add an optional parameter to the builder
    pub fn add_opt<T: 'static + ToSql + Sync>(&mut self, value: Option<T>) -> &mut Self {
        if let Some(v) = value {
            self.add(v);
        } else {
            // Add NULL value
            self.params.push(Box::new(None::<String>));
        }
        self
    }

    /// Get the parameters as a slice of references
    pub fn as_slice(&self) -> Vec<&(dyn ToSql + Sync)> {
        self.params
            .iter()
            .map(|p| p.as_ref() as &(dyn ToSql + Sync))
            .collect()
    }
}

/// Execute a query with the parameter builder
pub fn execute_with_params(query_str: &str, params: &QueryParams) -> Result<u64, PostgresError> {
    let client = get_postgres_client()?;
    client.execute(query_str, &params.as_slice())
}

/// Execute a query with the parameter builder and return the rows
pub fn query_with_params(query_str: &str, params: &QueryParams) -> Result<Vec<Row>, PostgresError> {
    let client = get_postgres_client()?;
    client.query(query_str, &params.as_slice())
}

/// Execute a query with the parameter builder and return a single row
pub fn query_one_with_params(query_str: &str, params: &QueryParams) -> Result<Row, PostgresError> {
    let client = get_postgres_client()?;
    client.query_one(query_str, &params.as_slice())
}

/// Execute a query with the parameter builder and return an optional row
pub fn query_opt_with_params(
    query_str: &str,
    params: &QueryParams,
) -> Result<Option<Row>, PostgresError> {
    let client = get_postgres_client()?;
    client.query_opt(query_str, &params.as_slice())
}

/// Execute a query with the parameter builder using the connection pool
pub fn execute_with_pool_params(
    query_str: &str,
    params: &QueryParams,
) -> Result<u64, PostgresError> {
    execute_with_pool(query_str, &params.as_slice())
}

/// Execute a query with the parameter builder using the connection pool and return the rows
pub fn query_with_pool_params(
    query_str: &str,
    params: &QueryParams,
) -> Result<Vec<Row>, PostgresError> {
    query_with_pool(query_str, &params.as_slice())
}

/// Execute a query with the parameter builder using the connection pool and return a single row
pub fn query_one_with_pool_params(
    query_str: &str,
    params: &QueryParams,
) -> Result<Row, PostgresError> {
    query_one_with_pool(query_str, &params.as_slice())
}

/// Execute a query with the parameter builder using the connection pool and return an optional row
pub fn query_opt_with_pool_params(
    query_str: &str,
    params: &QueryParams,
) -> Result<Option<Row>, PostgresError> {
    query_opt_with_pool(query_str, &params.as_slice())
}

/// Send a notification on a channel
///
/// This function sends a notification on the specified channel with the specified payload.
///
/// Example:
/// ```no_run
/// use sal_postgresclient::notify;
///
/// notify("my_channel", "Hello, world!").expect("Failed to send notification");
/// ```
pub fn notify(channel: &str, payload: &str) -> Result<(), PostgresError> {
    let client = get_postgres_client()?;
    client.execute(&format!("NOTIFY {}, '{}'", channel, payload), &[])?;
    Ok(())
}

/// Send a notification on a channel using the connection pool
///
/// This function sends a notification on the specified channel with the specified payload using the connection pool.
///
/// Example:
/// ```no_run
/// use sal_postgresclient::notify_with_pool;
///
/// notify_with_pool("my_channel", "Hello, world!").expect("Failed to send notification");
/// ```
pub fn notify_with_pool(channel: &str, payload: &str) -> Result<(), PostgresError> {
    let pool = get_postgres_pool()?;
    let mut client = pool.get().map_err(|e| {
        create_postgres_error(&format!("Failed to get connection from pool: {}", e))
    })?;
    client.execute(&format!("NOTIFY {}, '{}'", channel, payload), &[])?;
    Ok(())
}