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use crate::{
    handles::{self, Statement},
    parameter_collection::ParameterCollection,
    CursorImpl, Error, Prepared,
};
use std::thread::panicking;
use widestring::{U16Str, U16String};

impl<'conn> Drop for Connection<'conn> {
    fn drop(&mut self) {
        if let Err(e) = self.connection.disconnect() {
            // Avoid panicking, if we already have a panic. We don't want to mask the original
            // error.
            if !panicking() {
                panic!("Unexpected error disconnecting: {:?}", e)
            }
        }
    }
}

/// The connection handle references storage of all information about the connection to the data
/// source, including status, transaction state, and error information.
pub struct Connection<'c> {
    connection: handles::Connection<'c>,
}

impl<'c> Connection<'c> {
    pub(crate) fn new(connection: handles::Connection<'c>) -> Self {
        Self { connection }
    }

    /// Executes a statement. This is the fastest way to submit an SQL statement for one-time
    /// execution.
    ///
    /// # Parameters
    ///
    /// * `query`: The text representation of the SQL statement. E.g. "SELECT * FROM my_table;". A
    ///   question mark (`?`) may be used to indicate positional parameters in the statement text.
    /// * `params`: Used to bind the placeholders in the statement text to argument values You can
    ///   use `()` to represent no parameters.
    ///
    /// # Return
    ///
    /// Returns `Some` if a cursor is created. If `None` is returned no cursor has been created (
    /// e.g. the query came back empty). Note that an empty query may also create a cursor with zero
    /// rows.
    pub fn exec_direct_utf16(
        &mut self,
        query: &U16Str,
        params: impl ParameterCollection,
    ) -> Result<Option<CursorImpl<Statement>>, Error> {
        let mut stmt = self.connection.allocate_statement()?;

        let paramset_size = params.parameter_set_size();

        if paramset_size == 0 {
            Ok(None)
        } else {
            // Reset parameters so we do not dereference stale once by mistake if we call
            // `exec_direct`.
            stmt.reset_parameters()?;
            unsafe {
                stmt.set_paramset_size(paramset_size)?;
                // Bind new parameters passed by caller.
                params.bind_parameters_to(&mut stmt)?;
                stmt.exec_direct(query)?
            };
            // Check if a result set has been created.
            if stmt.num_result_cols()? == 0 {
                Ok(None)
            } else {
                Ok(Some(CursorImpl::new(stmt)))
            }
        }
    }

    /// Executes a prepareable statement. This is the fastest way to submit an SQL statement for
    /// one-time execution.
    ///
    /// # Parameters
    ///
    /// * `query`: The text representation of the SQL statement. E.g. "SELECT * FROM my_table;".
    /// * `params`: `?` may be used as a placeholder in the statement text. You can use `()` to
    ///   represent no parameters.
    ///
    /// # Return
    ///
    /// Returns `Some` if a cursor is created. If `None` is returned no cursor has been created (
    /// e.g. the query came back empty). Note that an empty query may also create a cursor with zero
    /// rows.
    ///
    /// # Example
    ///
    /// ```no_run
    /// use odbc_api::Environment;
    ///
    /// // I herby solemnly swear that this is the only ODBC environment in the entire process, thus
    /// // making this call safe.
    /// let env = unsafe {
    ///     Environment::new()?
    /// };
    ///
    /// let mut conn = env.connect("YourDatabase", "SA", "<YourStrong@Passw0rd>")?;
    /// if let Some(cursor) = conn.execute("SELECT year, name FROM Birthdays;", ())? {
    ///     // Use cursor to process query results.  
    /// }
    /// # Ok::<(), odbc_api::Error>(())
    /// ```
    pub fn execute(
        &mut self,
        query: &str,
        params: impl ParameterCollection,
    ) -> Result<Option<CursorImpl<Statement>>, Error> {
        let query = U16String::from_str(query);
        self.exec_direct_utf16(&query, params)
    }

    /// Prepares an SQL statement. This is recommended for repeated execution of similar queries.
    ///
    /// # Parameters
    ///
    /// * `query`: The text representation of the SQL statement. E.g. "SELECT * FROM my_table;". `?`
    ///   may be used as a placeholder in the statement text, to be replaced with parameters during
    ///   execution.
    pub fn prepare_utf16(&self, query: &U16Str) -> Result<Prepared, Error> {
        let mut stmt = self.connection.allocate_statement()?;
        stmt.prepare(query)?;
        Ok(Prepared::new(stmt))
    }

    /// Prepares an SQL statement. This is recommended for repeated execution of similar queries.
    ///
    /// # Parameters
    ///
    /// * `query`: The text representation of the SQL statement. E.g. "SELECT * FROM my_table;". `?`
    ///   may be used as a placeholder in the statement text, to be replaced with parameters during
    ///   execution.
    pub fn prepare(&self, query: &str) -> Result<Prepared, Error> {
        let query = U16String::from_str(query);
        self.prepare_utf16(&query)
    }
}