#![allow(non_camel_case_types)]
#![allow(dead_code)]
#![allow(missing_copy_implementations)]

use crate::cassandra::cluster::Cluster;
use crate::cassandra::error::*;
use crate::cassandra::future::CassFuture;
use crate::cassandra::metrics::SessionMetrics;
use crate::cassandra::prepared::PreparedStatement;
use crate::cassandra::result::CassResult;
use crate::cassandra::schema::schema_meta::SchemaMeta;
use crate::cassandra::statement::Statement;
use crate::cassandra::util::{Protected, ProtectedInner};
use crate::{cassandra::batch::Batch, BatchType};

use crate::cassandra_sys::cass_session_close;
use crate::cassandra_sys::cass_session_connect;
use crate::cassandra_sys::cass_session_connect_keyspace_n;
use crate::cassandra_sys::cass_session_execute;
use crate::cassandra_sys::cass_session_execute_batch;
use crate::cassandra_sys::cass_session_free;
use crate::cassandra_sys::cass_session_get_metrics;
use crate::cassandra_sys::cass_session_get_schema_meta;
use crate::cassandra_sys::cass_session_new;
use crate::cassandra_sys::cass_session_prepare_n;
use crate::cassandra_sys::CassSession as _Session;

use std::ffi::NulError;
use std::mem;
use std::os::raw::c_char;
use std::sync::Arc;

#[derive(Debug, Eq, PartialEq)]
struct SessionInner<T>(T, *mut _Session);

// The underlying C type has no thread-local state, and explicitly supports access
// from multiple threads: https://datastax.github.io/cpp-driver/topics/#thread-safety
unsafe impl<T: Send> Send for SessionInner<T> {}
unsafe impl<T: Sync> Sync for SessionInner<T> {}

impl<T> SessionInner<T> {
    fn new(bound: T, inner: *mut _Session) -> Arc<Self> {
        Arc::new(Self(bound, inner))
    }
}

/// The session scope defines if the session is bound [`session_scope::Bound`], meaning it is associated
/// with a keyspace.  Or unbound [`session_scope::Unbound`], meaning it is not associated with any keyspace.
///
/// Keyspace association is done by the `connect` and `connect_lazy` methods in [`Cluster`].
pub trait SessionScope: session_scope::sealed::Sealed + Clone + Send + Sync + 'static {}

/// See [`SessionScope`] for more information.
pub mod session_scope {
    pub use super::SessionScope;

    pub(super) mod sealed {
        pub trait Sealed {}
    }

    /// The session is bound to a given keyspace.
    #[derive(Debug, Clone)]
    pub struct Bound {
        pub(crate) keyspace: String,
    }

    impl Bound {
        pub(crate) fn new(keyspace: impl Into<String>) -> Self {
            Self {
                keyspace: keyspace.into(),
            }
        }
    }

    /// The session is not bound to any keyspace in particular.
    #[derive(Debug, Clone)]
    pub struct Unbound;

    impl sealed::Sealed for Bound {}
    impl sealed::Sealed for Unbound {}

    impl super::SessionScope for Bound {}
    impl super::SessionScope for Unbound {}
}
/// A session object is used to execute queries and maintains cluster state through
/// the control connection. The control connection is used to auto-discover nodes and
/// monitor cluster changes (topology and schema). Each session also maintains multiple
/// /pools of connections to cluster nodes which are used to query the cluster.
///
/// Instances of the session object are thread-safe to execute queries.
#[derive(Debug, Clone)]
pub struct Session<T = session_scope::Bound>(Arc<SessionInner<T>>);

impl<T> Eq for Session<T> {}

impl<T> PartialEq for Session<T> {
    fn eq(&self, other: &Self) -> bool {
        (self.0).1 == (other.0).1
    }
}

// The underlying C type has no thread-local state, and explicitly supports access
// from multiple threads: https://datastax.github.io/cpp-driver/topics/#thread-safety
unsafe impl<T: Send> Send for Session<T> {}
unsafe impl<T: Sync> Sync for Session<T> {}

impl<T> ProtectedInner<*mut _Session> for SessionInner<T> {
    fn inner(&self) -> *mut _Session {
        self.1
    }
}

impl<T> ProtectedInner<*mut _Session> for Session<T> {
    fn inner(&self) -> *mut _Session {
        self.0.inner()
    }
}

impl Protected<*mut _Session> for Session<session_scope::Unbound> {
    fn build(inner: *mut _Session) -> Self {
        if inner.is_null() {
            panic!("Unexpected null pointer")
        };
        Session(SessionInner::new(session_scope::Unbound, inner))
    }
}

impl<T> Drop for SessionInner<T> {
    /// Frees a session instance. If the session is still connected it will be synchronously
    /// closed before being deallocated.
    fn drop(&mut self) {
        unsafe { cass_session_free(self.1) }
    }
}

impl Default for Session<session_scope::Unbound> {
    fn default() -> Session<session_scope::Unbound> {
        Session::new(session_scope::Unbound)
    }
}

impl<S> Session<S>
where
    S: SessionScope,
{
    pub(crate) fn new(bound: S) -> Self {
        unsafe { Session(SessionInner::new(bound, cass_session_new())) }
    }

    /// Creates a statement with the given query.
    pub fn statement(&self, query: impl AsRef<str>) -> Statement<S> {
        let query = query.as_ref();
        let param_count = query.matches("?").count();
        Statement::new(self.clone(), query, param_count)
    }

    /// Executes a given query.
    pub async fn execute(&self, query: impl AsRef<str>) -> Result<CassResult> {
        let statement = self.statement(query);
        statement.execute().await
    }

    /// Creates a new batch that is bound to this session.
    pub fn batch(&self, batch_type: BatchType) -> Batch<S> {
        Batch::new(batch_type, self.clone())
    }

    /// Gets a snapshot of this session's schema metadata. The returned
    /// snapshot of the schema metadata is not updated. This function
    /// must be called again to retrieve any schema changes since the
    /// previous call.
    pub fn get_schema_meta(&self) -> SchemaMeta {
        unsafe { SchemaMeta::build(cass_session_get_schema_meta(self.inner())) }
    }

    /// Gets a copy of this session's performance/diagnostic metrics.
    pub fn get_metrics(&self) -> SessionMetrics {
        unsafe {
            let mut metrics = mem::zeroed();
            cass_session_get_metrics(self.inner(), &mut metrics);
            SessionMetrics::build(&metrics)
        }
    }

    /// Create a prepared statement with the given query.
    pub async fn prepare(&self, query: impl AsRef<str>) -> Result<PreparedStatement<S>> {
        let query = query.as_ref();
        let prepare_future = {
            let query_ptr = query.as_ptr() as *const c_char;
            CassFuture::build(self.clone(), unsafe {
                cass_session_prepare_n(self.inner(), query_ptr, query.len())
            })
        };
        prepare_future.await
    }

    //    pub fn get_schema(&self) -> Schema {
    //        unsafe { Schema(cass_session_get_schema(self.0)) }
    //    }
}

impl Session<session_scope::Bound> {
    /// Returns the keyspace that the session is bound to.
    pub fn keyspace(&self) -> &str {
        &(self.0).0.keyspace
    }
}