use futures::Future;
use std::io::Read;
use tokio_postgres::types::{ToSql, Type};
use tokio_postgres::Error;

use crate::{Client, CopyOutReader, Portal, Query, QueryPortal, Statement, ToStatement};

pub struct Transaction<'a> {
    client: &'a mut Client,
    depth: u32,
    done: bool,
}

impl<'a> Drop for Transaction<'a> {
    fn drop(&mut self) {
        if !self.done {
            let _ = self.rollback_inner();
        }
    }
}

impl<'a> Transaction<'a> {
    pub(crate) fn new(client: &'a mut Client) -> Transaction<'a> {
        Transaction {
            client,
            depth: 0,
            done: false,
        }
    }

    pub fn commit(mut self) -> Result<(), Error> {
        self.done = true;
        if self.depth == 0 {
            self.client.batch_execute("COMMIT")
        } else {
            self.client
                .batch_execute(&format!("RELEASE sp{}", self.depth))
        }
    }

    pub fn rollback(mut self) -> Result<(), Error> {
        self.done = true;
        self.rollback_inner()
    }

    fn rollback_inner(&mut self) -> Result<(), Error> {
        if self.depth == 0 {
            self.client.batch_execute("ROLLBACK")
        } else {
            self.client
                .batch_execute(&format!("ROLLBACK TO sp{}", self.depth))
        }
    }

    pub fn prepare(&mut self, query: &str) -> Result<Statement, Error> {
        self.client.prepare(query)
    }

    pub fn prepare_typed(&mut self, query: &str, types: &[Type]) -> Result<Statement, Error> {
        self.client.prepare_typed(query, types)
    }

    pub fn execute<T>(&mut self, query: &T, params: &[&dyn ToSql]) -> Result<u64, Error>
    where
        T: ?Sized + ToStatement,
    {
        self.client.execute(query, params)
    }

    pub fn query<T>(&mut self, query: &T, params: &[&dyn ToSql]) -> Result<Query<'_>, Error>
    where
        T: ?Sized + ToStatement,
    {
        self.client.query(query, params)
    }

    pub fn bind<T>(&mut self, query: &T, params: &[&dyn ToSql]) -> Result<Portal, Error>
    where
        T: ?Sized + ToStatement,
    {
        let statement = query.__statement(&mut self.client)?;
        self.client
            .get_mut()
            .bind(&statement.0, params)
            .wait()
            .map(Portal)
    }

    pub fn query_portal(
        &mut self,
        portal: &Portal,
        max_rows: i32,
    ) -> Result<QueryPortal<'_>, Error> {
        Ok(QueryPortal::new(
            self.client.get_mut().query_portal(&portal.0, max_rows),
        ))
    }

    pub fn copy_in<T, R>(
        &mut self,
        query: &T,
        params: &[&dyn ToSql],
        reader: R,
    ) -> Result<u64, Error>
    where
        T: ?Sized + ToStatement,
        R: Read,
    {
        self.client.copy_in(query, params, reader)
    }

    pub fn copy_out<T>(
        &mut self,
        query: &T,
        params: &[&dyn ToSql],
    ) -> Result<CopyOutReader<'_>, Error>
    where
        T: ?Sized + ToStatement,
    {
        self.client.copy_out(query, params)
    }

    pub fn batch_execute(&mut self, query: &str) -> Result<(), Error> {
        self.client.batch_execute(query)
    }

    pub fn transaction(&mut self) -> Result<Transaction<'_>, Error> {
        let depth = self.depth + 1;
        self.client
            .batch_execute(&format!("SAVEPOINT sp{}", depth))?;
        Ok(Transaction {
            client: self.client,
            depth,
            done: false,
        })
    }
}