dropbreak/examples/migration.rs.incomplete

/* This file is a complete work in progress! And is meant to illustrate a possible way of
 * migrating databases with Rustbreak.
 *
 * Currently the major challenge is to statically define the upgrade process.
 *
 * This is currently done by using the `upgrading_macro`.
 *
 * The idea is to read the 'version' tag in the file, load it into a simple tag struct and
 * read the version from there. This version is then used to dynamically get the corresponding
 * struct type. This then gets converted to the latest version.
 */


extern crate rustbreak;
#[macro_use] extern crate serde_derive;

use rustbreak::FileDatabase;
use rustbreak::deser::Ron;

mod data {
    #[derive(Debug, Serialize, Deserialize, Clone, Copy)]
    pub enum Version {
        First, Second, Third,
    }

    #[derive(Debug, Serialize, Deserialize, Clone)]
    pub struct Versioning {
        pub version: Version
    }

    pub mod v1 {
        use data::Version;
        use std::collections::HashMap;

        #[derive(Debug, Serialize, Deserialize, Clone)]
        pub struct Players {
            version: Version,
            pub players: HashMap<i32, String>,
        }

        impl Players {
            pub fn new() -> Players {
                Players {
                    version: Version::First,
                    players: HashMap::new(),
                }
            }
        }
    }

    pub mod v2 {
        use data::Version;
        use std::collections::HashMap;

        #[derive(Debug, Serialize, Deserialize, Clone)]
        pub struct Player {
            pub name: String,
            pub level: i32,
        }

        #[derive(Debug, Serialize, Deserialize, Clone)]
        pub struct Players {
            version: Version,
            pub players: HashMap<i32, Player>,
        }

        impl Players {
            pub fn new() -> Players {
                Players {
                    version: Version::Second,
                    players: HashMap::new(),
                }
            }
        }
    }

    pub mod v3 {
        use data::Version;
        use std::collections::HashMap;

        #[derive(Debug, Serialize, Deserialize, Clone)]
        pub struct Player {
            pub name: String,
            pub score: i64
        }

        #[derive(Debug, Serialize, Deserialize, Clone)]
        pub struct Players {
            version: Version,
            pub players: HashMap<i32, Player>,
        }

        impl Players {
            pub fn new() -> Players {
                Players {
                    version: Version::Third,
                    players: HashMap::new(),
                }
            }
        }
    }

    pub fn convert_v1_v2(input: v1::Players) -> v2::Players {
        let mut new = v2::Players::new();
        for (key, player) in input.players {
            new.players.insert(key,
                               v2::Player {
                                   name: player,
                                   level: 1
                               });
        }

        new
    }

    pub fn convert_v2_v3(input: v2::Players) -> v3::Players {
        let mut new = v3::Players::new();
        for (key, player) in input.players {
            new.players.insert(key,
                               v3::Player {
                                   name: player.name,
                                   score: 0
                               });
        }

        new
    }
}

macro_rules! migration_rules {
    ( $name:ident -> $res:ty { $( $t:ty => $conv:path ),* $(,)* } ) => {
        fn $name<T: 'static>(input: T) -> Option<$res> {
            fn inner(mut input: Box<std::any::Any>) -> Option<$res> {
                println!("We have: {:#?}", input);
                $(
                    {
                        let mut maybe_in = None;
                        if let Some(out) = input.downcast_ref::<$t>() {
                            maybe_in = Some(Box::new($conv(out.clone())));
                        }

                        if let Some(inp) = maybe_in {
                            input = inp;
                        }
                    }
                )*

                if let Ok(out) = input.downcast::<$res>() {
                    return Some(*out);
                }

                None
            }
            inner(Box::new(input))
        }
    }
}

migration_rules! {
    update_database -> data::v3::Players {
        data::v1::Players => data::convert_v1_v2,
        data::v2::Players => data::convert_v2_v3,
    }
}

fn get_version() -> data::Version {
    let db = FileDatabase::<data::Versioning, Ron>::from_path("migration.ron", data::Versioning { version: data::Version::First }).unwrap();
    db.load().unwrap();
    db.read(|ver| ver.version).unwrap()
}

fn main() {
    use data::v3::Players;

    let version = get_version();


    // Let's check if there are any updates
    let updated_data = update_database(database.get_data(false).unwrap()).unwrap();
    let database = FileDatabase::<Players, Ron>::from_path("migration.ron", updated_data).unwrap();

    println!("{:#?}", database);
}