Diesel code migrations

/// This is one of two sources of DB migrations.
/// The other one is pure SQL files found in the `migrations/` folder.
/// This module contains migrations made with Rust code.
use diesel::connection::BoxableConnection;
use diesel::migration::{Result as MResult, *};
use diesel::pg::Pg;
use diesel_migrations::EmbeddedMigrations;
use std::fmt::*;

mod scan_scope;

pub const MIGRATIONS: EmbeddedMigrations = diesel_migrations::embed_migrations!();

macro_rules! include_migration {
    ($migrations:ident, $mod_path:tt) => {
        $migrations.push(Box::new(CodeMigration {
            run: $mod_path::run,
            revert: $mod_path::revert,
            name: Name {
                name: $mod_path::name(),
            },
        }))
    };
}

pub struct AllMigrations;

impl MigrationSource<Pg> for AllMigrations {
    fn migrations(&self) -> MResult<Vec<Box<dyn Migration<Pg>>>> {
        let mut migrations = MIGRATIONS.migrations()?;
        include_migration!(migrations, scan_scope);
        Ok(migrations)
    }
}

pub struct CodeMigration<Run, Revert>
where
    Run: Fn(&mut dyn BoxableConnection<Pg>) -> MResult<()>,
    Revert: Fn(&mut dyn BoxableConnection<Pg>) -> MResult<()>,
{
    run: Run,
    revert: Revert,
    name: Name,
}

impl<Run, Revert> Migration<Pg> for CodeMigration<Run, Revert>
where
    Run: Fn(&mut dyn BoxableConnection<Pg>) -> MResult<()>,
    Revert: Fn(&mut dyn BoxableConnection<Pg>) -> MResult<()>,
{
    fn run(&self, conn: &mut dyn BoxableConnection<Pg>) -> MResult<()> {
        (self.run)(conn)
    }
    fn revert(&self, conn: &mut dyn BoxableConnection<Pg>) -> MResult<()> {
        (self.revert)(conn)
    }
    fn metadata(&self) -> &dyn MigrationMetadata {
        &Metadata
    }
    fn name(&self) -> &dyn MigrationName {
        &self.name
    }
}

struct Metadata;
impl MigrationMetadata for Metadata {}

struct Name {
    name: &'static str,
}

impl Display for Name {
    fn fmt(&self, f: &mut Formatter) -> std::result::Result<(), Error> {
        write!(f, "{}", self.name)
    }
}

impl MigrationName for Name {
    fn version(&self) -> MigrationVersion<'_> {
        self.name
            .chars()
            .filter(|c| c.is_numeric())
            .collect::<String>()
            .into()
    }
}