// How to run this example:
// ```sh
// docker run -d --rm -p 5432:5432 techempower/tfb.database.postgres:latest
// cargo run --release --no-default-features --example techempower
// ```
fn main() {
    __impl::main();
}

#[cfg(not(unix))]
mod __impl {
    pub fn main() {
        println!("This example only works on unix");
    }
}

#[cfg(unix)]
mod __impl {
    #[global_allocator]
    static GLOBAL: mimalloc::MiMalloc = mimalloc::MiMalloc;

    use std::fmt::Write;
    use std::io;
    use std::sync::Arc;

    use bytes::BytesMut;
    use may_minihttp::{HttpService, HttpServiceFactory, Request, Response};
    use may_postgres::{types::ToSql, Client, Statement};
    use nanorand::{Rng, WyRand};
    use smallvec::SmallVec;
    use yarte::{ywrite_html, Serialize};

    mod utils {
        use atoi::FromRadix10;

        pub fn get_query_param(query: &str) -> u16 {
            let q = if let Some(pos) = query.find("?q") {
                u16::from_radix_10(query.split_at(pos + 3).1.as_ref()).0
            } else {
                1
            };
            q.clamp(1, 500)
        }
    }

    #[derive(Serialize)]
    struct HelloMessage {
        message: &'static str,
    }

    #[derive(Serialize)]
    struct WorldRow {
        id: i32,
        randomnumber: i32,
    }

    #[derive(Serialize)]
    pub struct Fortune<'a> {
        id: i32,
        message: &'a str,
    }

    struct PgConnectionPool {
        clients: Vec<PgConnection>,
    }

    impl PgConnectionPool {
        fn new(db_url: &'static str) -> PgConnectionPool {
            let size = num_cpus::get();
            let clients = (0..size)
                .map(|_| may::go!(move || PgConnection::new(db_url)))
                .collect::<Vec<_>>();
            let mut clients: Vec<_> = clients.into_iter().map(|t| t.join().unwrap()).collect();
            clients.sort_by(|a, b| (a.client.id() % size).cmp(&(b.client.id() % size)));
            // for c in &clients {
            //     println!("client id: {}", c.client.id());
            // }
            PgConnectionPool { clients }
        }

        fn get_connection(&self, id: usize) -> PgConnection {
            let len = self.clients.len();
            let connection = &self.clients[id % len];
            assert_eq!(connection.client.id() % len, id % len);
            PgConnection {
                client: connection.client.clone(),
                statement: connection.statement.clone(),
            }
        }
    }

    struct PgStatement {
        world: Statement,
        fortune: Statement,
        updates: Vec<Statement>,
    }

    struct PgConnection {
        client: Client,
        statement: Arc<PgStatement>,
    }

    impl PgConnection {
        fn new(db_url: &str) -> Self {
            let client = may_postgres::connect(db_url).unwrap();

            let world = client.prepare("SELECT * FROM world WHERE id=$1").unwrap();
            let fortune = client.prepare("SELECT * FROM fortune").unwrap();

            let mut updates = Vec::new();
            for num in 1..=500u16 {
                let mut pl: u16 = 1;
                let mut q = String::new();
                q.push_str("UPDATE world SET randomnumber = CASE id ");
                for _ in 1..=num {
                    let _ = write!(&mut q, "when ${} then ${} ", pl, pl + 1);
                    pl += 2;
                }
                q.push_str("ELSE randomnumber END WHERE id IN (");
                for _ in 1..=num {
                    let _ = write!(&mut q, "${pl},");
                    pl += 1;
                }
                q.pop();
                q.push(')');
                updates.push(client.prepare(&q).unwrap());
            }

            let statement = Arc::new(PgStatement {
                world,
                fortune,
                updates,
            });

            PgConnection { client, statement }
        }

        fn get_world(&self, random_id: i32) -> Result<WorldRow, may_postgres::Error> {
            let mut q = self
                .client
                .query_raw(&self.statement.world, &[&random_id])?;
            match q.next().transpose()? {
                Some(row) => Ok(WorldRow {
                    id: row.get(0),
                    randomnumber: row.get(1),
                }),
                None => unreachable!("random_id={}", random_id),
            }
        }

        fn get_worlds(
            &self,
            num: usize,
            rand: &mut WyRand,
        ) -> Result<SmallVec<[WorldRow; 32]>, may_postgres::Error> {
            let mut queries = SmallVec::<[_; 32]>::new();
            for _ in 0..num {
                let random_id = (rand.generate::<u32>() % 10_000 + 1) as i32;
                queries.push(
                    self.client
                        .query_raw(&self.statement.world, &[&random_id])?,
                );
            }

            let mut worlds = SmallVec::<[_; 32]>::new();
            for mut q in queries {
                match q.next().transpose()? {
                    Some(row) => worlds.push(WorldRow {
                        id: row.get(0),
                        randomnumber: row.get(1),
                    }),
                    None => unreachable!(),
                }
            }
            Ok(worlds)
        }

        fn updates(
            &self,
            num: usize,
            rand: &mut WyRand,
        ) -> Result<SmallVec<[WorldRow; 32]>, may_postgres::Error> {
            let mut queries = SmallVec::<[_; 32]>::new();
            for _ in 0..num {
                let random_id = (rand.generate::<u32>() % 10_000 + 1) as i32;
                queries.push(
                    self.client
                        .query_raw(&self.statement.world, &[&random_id])?,
                );
            }

            let mut worlds = SmallVec::<[_; 32]>::new();
            for mut q in queries {
                let new_random_num = (rand.generate::<u32>() % 10_000 + 1) as i32;
                match q.next().transpose()? {
                    Some(row) => worlds.push(WorldRow {
                        id: row.get(0),
                        randomnumber: new_random_num,
                    }),
                    None => unreachable!(),
                }
            }

            let mut params: Vec<&(dyn ToSql)> = Vec::with_capacity(num * 3);
            for w in &worlds {
                params.push(&w.id);
                params.push(&w.randomnumber);
            }
            for w in &worlds {
                params.push(&w.id);
            }

            // use `query_one` to sync wait result
            let _ = self
                .client
                .query_one(&self.statement.updates[num - 1], &params);
            Ok(worlds)
        }

        fn tell_fortune(&self, buf: &mut BytesMut) -> Result<(), may_postgres::Error> {
            let rows = self.client.query_raw(&self.statement.fortune, &[])?;

            let all_rows = Vec::from_iter(rows.map(|r| r.unwrap()));
            let mut fortunes = Vec::with_capacity(all_rows.len() + 1);
            fortunes.extend(all_rows.iter().map(|r| Fortune {
                id: r.get(0),
                message: r.get(1),
            }));
            fortunes.push(Fortune {
                id: 0,
                message: "Additional fortune added at request time.",
            });
            fortunes.sort_by(|it, next| it.message.cmp(next.message));

            let mut body = unsafe { std::ptr::read(buf) };
            ywrite_html!(body, "{{> fortune }}");
            unsafe { std::ptr::write(buf, body) };
            Ok(())
        }
    }

    struct Techempower {
        db: PgConnection,
        rng: WyRand,
    }

    impl HttpService for Techempower {
        fn call(&mut self, req: Request, rsp: &mut Response) -> io::Result<()> {
            // Bare-bones router
            match req.path() {
                "/json" => {
                    rsp.header("Content-Type: application/json");
                    let msg = HelloMessage {
                        message: "Hello, World!",
                    };
                    msg.to_bytes_mut(rsp.body_mut());
                }
                "/plaintext" => {
                    rsp.header("Content-Type: text/plain").body("Hello, World!");
                }
                "/db" => {
                    rsp.header("Content-Type: application/json");
                    let random_id = (self.rng.generate::<u32>() % 10_000 + 1) as i32;
                    let world = self.db.get_world(random_id).unwrap();
                    world.to_bytes_mut(rsp.body_mut())
                }
                "/fortunes" => {
                    rsp.header("Content-Type: text/html; charset=utf-8");
                    self.db.tell_fortune(rsp.body_mut()).unwrap();
                }
                p if p.starts_with("/queries") => {
                    rsp.header("Content-Type: application/json");
                    let q = utils::get_query_param(p) as usize;
                    let worlds = self.db.get_worlds(q, &mut self.rng).unwrap();
                    worlds.to_bytes_mut(rsp.body_mut());
                }
                p if p.starts_with("/updates") => {
                    rsp.header("Content-Type: application/json");
                    let q = utils::get_query_param(p) as usize;
                    let worlds = self.db.updates(q, &mut self.rng).unwrap();
                    worlds.to_bytes_mut(rsp.body_mut());
                }
                _ => {
                    rsp.status_code(404, "Not Found");
                }
            }

            Ok(())
        }
    }

    struct HttpServer {
        db_pool: PgConnectionPool,
    }

    impl HttpServiceFactory for HttpServer {
        type Service = Techempower;

        fn new_service(&self, id: usize) -> Self::Service {
            let db = self.db_pool.get_connection(id);
            let rng = WyRand::new();
            Techempower { db, rng }
        }
    }

    pub fn main() {
        may::config().set_pool_capacity(1000).set_stack_size(0x1000);

        let connect_str = "postgres://benchmarkdbuser:benchmarkdbpass@tfb-database/hello_world";
        let server = HttpServer {
            db_pool: PgConnectionPool::new(connect_str),
        };

        println!("Starting http server: 127.0.0.1:8081");
        server.start("0.0.0.0:8081").unwrap().join().unwrap();
    }
}