4 files changed, 99 insertions, 2 deletions
diff --git a/src/db/backend.rs b/src/db/backend.rs
index b75d5ca..5f35dd9 100644
--- a/src/db/backend.rs
+++ b/src/db/backend.rs
@@ -1,7 +1,9 @@
+use barrel::backend::SqlGenerator;
 pub use diesel::connection::Connection;
 
 pub trait Connectable {
     type Connection: Connection;
+    type SqlGenerator: SqlGenerator;
     fn connect(&self) -> diesel::ConnectionResult<Self::Connection>;
 }
 
@@ -11,6 +13,7 @@ pub struct Sqlite {
 
 impl Connectable for Sqlite {
     type Connection = diesel::sqlite::SqliteConnection;
+    type SqlGenerator = barrel::backend::Sqlite;
 
     fn connect(&self) -> diesel::ConnectionResult<Self::Connection> {
         Self::Connection::establish(self.db_file)
diff --git a/src/db/migration/change.rs b/src/db/migration/change.rs
new file mode 100644
index 0000000..b5d0dd5
--- /dev/null
+++ b/src/db/migration/change.rs
@@ -0,0 +1,62 @@
+use diesel::Connection;
+
+use crate::db::backend::Connectable;
+use crate::db::models::Field;
+
+pub enum DatabaseChange {
+    CreateModel {
+        name: &'static str,
+        fields: &'static [Field],
+        options: &'static [CreateModelOption]
+    },
+}
+
+impl DatabaseChange {
+    pub fn apply<C: Connectable>(&self, app_name: &str, connection: &C::Connection) {
+        use barrel::{Migration, Table, types};
+
+        match self {
+            DatabaseChange::CreateModel { name, fields, options } => {
+                let mut m = Migration::new();
+
+                let columns: Vec<(&'static str, _)> = fields.iter().map(|field| match field {
+                    Field::CharField { name, max_length } => {
+                        let name = *name;
+                        let _type = match max_length {
+                            None => types::text(),
+                            Some(max_length) => types::varchar(*max_length),
+                        };
+                        (name, _type)
+                    }
+                    Field::DateTimeField { name } => {
+                        (*name, types::text()) // TODO do smart things on non-sqlite
+                    }
+                    Field::IntField { name } => {
+                        (*name, types::integer())
+                    }
+                }).collect();
+
+                let callback = move |t: &mut Table| {
+                    for (name, _type) in &columns {
+                        t.add_column(*name, _type.clone());
+                    }
+                };
+
+                let table_name = format!("{}-{}", app_name, name);
+
+                if options.contains(&CreateModelOption::IfNotExist) {
+                    m.create_table_if_not_exists(table_name, callback);
+                } else {
+                    m.create_table(table_name, callback);
+                }
+
+                connection.execute(&m.make::<C::SqlGenerator>()).unwrap();
+            }
+        }
+    }
+}
+
+#[derive(PartialEq)]
+pub enum CreateModelOption {
+    IfNotExist,
+}
diff --git a/src/db/migration/mod.rs b/src/db/migration/mod.rs
index d53f46b..d511f88 100644
--- a/src/db/migration/mod.rs
+++ b/src/db/migration/mod.rs
@@ -1,5 +1,13 @@
 pub use tosin_macros::gather_migrations as gather;
 
+use diesel::{Connection, result::Error as DieselError};
+
+use crate::db::backend::Connectable;
+
+mod change;
+
+pub use change::*;
+
 pub struct Migration {
     pub id: usize,
     pub name: &'static str,
@@ -7,6 +15,15 @@ pub struct Migration {
     pub changes: &'static [DatabaseChange],
 }
 
-pub enum DatabaseChange {
-    CreateModel,
+impl Migration {
+    pub fn apply<C: Connectable>(&self, app_name: &str, connection: &C::Connection) {
+        // TODO prevent double-applying
+        connection.transaction::<_, DieselError, _>(|| {
+            for change in self.changes {
+                change.apply::<C>(app_name, connection);
+            }
+
+            Ok(())
+        }).unwrap();
+    }
 }
diff --git a/src/db/models/mod.rs b/src/db/models/mod.rs
index 5e59949..492df92 100644
--- a/src/db/models/mod.rs
+++ b/src/db/models/mod.rs
@@ -1,3 +1,18 @@
 pub use tosin_macros::Model;
 
 pub type Id = usize;
+
+pub enum Field {
+    CharField {
+        name: &'static str,
+        max_length: Option<usize>,
+    },
+
+    DateTimeField {
+        name: &'static str,
+    },
+
+    IntField {
+        name: &'static str,
+    },
+}