refac: add database connection manager

feat: add supported client to manifest

migra-cli/src/commands/apply.rs

@@ -1,5 +1,4 @@
 use crate::config::Config;
-use crate::databases::*;
 use crate::migration::{DatabaseMigrationManager, MigrationManager};
 use crate::opts::ApplyCommandOpt;
 use crate::path::PathBuilder;
@@ -7,8 +6,7 @@ use crate::StdResult;
 use std::convert::TryFrom;
 
 pub(crate) fn apply_sql(config: Config, opts: ApplyCommandOpt) -> StdResult<()> {
-    let connection = PostgresConnection::try_from(&config)?;
-    let mut manager = MigrationManager::new(connection);
+    let mut manager = MigrationManager::try_from(&config)?;
 
     let file_path = PathBuilder::from(config.directory_path())
         .append(opts.file_name)

migra-cli/src/commands/downgrade.rs

@@ -1,12 +1,10 @@
 use crate::config::Config;
-use crate::migration::{DatabaseMigrationManager, MigrationManager, MigrationNames};
-use crate::databases::*;
+use crate::migration::{DatabaseMigrationManager, MigrationManager};
 use crate::StdResult;
 use std::convert::TryFrom;
 
 pub(crate) fn downgrade_applied_migrations(config: Config) -> StdResult<()> {
-    let connection = PostgresConnection::try_from(&config)?;
-    let mut manager = MigrationManager::new(connection);
+    let mut manager = MigrationManager::try_from(&config)?;
 
     let applied_migrations = manager.applied_migration_names()?;
     let migrations = config.migrations()?;

migra-cli/src/commands/list.rs

@@ -1,16 +1,18 @@
 use crate::config::Config;
-use crate::database::DatabaseConnection;
 use crate::databases::*;
 use crate::error::{ErrorKind, StdResult};
-use crate::migration::{filter_pending_migrations, Migration, MigrationManager, MigrationNames};
+use crate::migration::{
+    filter_pending_migrations, DatabaseMigrationManager, Migration, MigrationManager,
+};
 
 const EM_DASH: char = '—';
 
 pub(crate) fn print_migration_lists(config: Config) -> StdResult<()> {
-    let applied_migration_names = match config.database_connection_string() {
+    let applied_migration_names = match config.database.connection_string() {
         Ok(ref database_connection_string) => {
-            let connection = PostgresConnection::open(database_connection_string)?;
-            let mut manager = MigrationManager::new(connection);
+            let connection_manager = DatabaseConnectionManager::new(&config.database);
+            let conn = connection_manager.connect_with_string(database_connection_string)?;
+            let mut manager = MigrationManager::new(conn);
 
             let applied_migration_names = manager.applied_migration_names()?;
 

migra-cli/src/commands/upgrade.rs

@@ -1,14 +1,12 @@
-use crate::databases::*;
 use crate::migration::{
     filter_pending_migrations, DatabaseMigrationManager, Migration, MigrationManager,
-    MigrationNames,
 };
 use crate::Config;
 use crate::StdResult;
 use std::convert::TryFrom;
 
 pub(crate) fn upgrade_pending_migrations(config: Config) -> StdResult<()> {
-    let mut manager = MigrationManager::new(PostgresConnection::try_from(&config)?);
+    let mut manager = MigrationManager::try_from(&config)?;
 
     let applied_migration_names = manager.applied_migration_names()?;
     let migrations = config.migrations()?;

migra-cli/src/config.rs

@@ -16,21 +16,47 @@ pub(crate) struct Config {
     root: PathBuf,
 
     #[serde(default)]
-    database: DatabaseConfig,
+    pub database: DatabaseConfig,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub(crate) enum SupportedDatabaseClient {
+    Postgres,
 }
 
 #[derive(Debug, Clone, Default, Serialize, Deserialize)]
 pub(crate) struct DatabaseConfig {
+    pub client: Option<SupportedDatabaseClient>,
     pub connection: Option<String>,
 }
 
+impl DatabaseConfig {
+    pub fn client(&self) -> crate::error::Result<SupportedDatabaseClient> {
+        Ok(SupportedDatabaseClient::Postgres)
+    }
+
+    pub fn connection_string(&self) -> crate::error::Result<String> {
+        let connection = self
+            .connection
+            .clone()
+            .unwrap_or_else(|| String::from(DEFAULT_DATABASE_CONNECTION_ENV));
+        if let Some(connection_env) = connection.strip_prefix("$") {
+            env::var(connection_env)
+                .map_err(|e| Error::new(ErrorKind::MissedEnvVar(connection_env.to_string()), e))
+        } else {
+            Ok(connection)
+        }
+    }
+}
+
 impl Default for Config {
     fn default() -> Config {
         Config {
-            manifest_root: PathBuf::new(),
+            manifest_root: PathBuf::default(),
             root: PathBuf::from("database"),
             database: DatabaseConfig {
                 connection: Some(String::from(DEFAULT_DATABASE_CONNECTION_ENV)),
+                ..Default::default()
             },
         }
     }
@@ -91,20 +117,6 @@ impl Config {
             .build()
     }
 
-    pub fn database_connection_string(&self) -> crate::error::Result<String> {
-        let connection = self
-            .database
-            .connection
-            .clone()
-            .unwrap_or_else(|| String::from(DEFAULT_DATABASE_CONNECTION_ENV));
-        if let Some(connection_env) = connection.strip_prefix("$") {
-            env::var(connection_env)
-                .map_err(|e| Error::new(ErrorKind::MissedEnvVar(connection_env.to_string()), e))
-        } else {
-            Ok(connection)
-        }
-    }
-
     pub fn migration_dir_path(&self) -> PathBuf {
         PathBuilder::from(&self.directory_path())
             .append("migrations")

migra-cli/src/database.rs

@@ -14,21 +14,18 @@ pub trait TryFromSql<QueryResultRow>: Sized {
     fn try_from_sql(row: QueryResultRow) -> StdResult<Self>;
 }
 
-pub trait DatabaseConnection: Sized {
-    type QueryResultRow;
-    type QueryResult;
-
+pub trait OpenDatabaseConnection: Sized {
     fn open(connection_string: &str) -> StdResult<Self>;
+}
 
+pub trait DatabaseConnection {
     fn batch_execute(&mut self, query: &str) -> StdResult<()>;
 
     fn execute<'b>(&mut self, query: &str, params: &'b [&'b dyn ToSql]) -> StdResult<u64>;
 
-    fn query<'b, OutputItem>(
+    fn query<'b>(
         &mut self,
         query: &str,
         params: &'b [&'b dyn ToSql],
-    ) -> StdResult<Vec<OutputItem>>
-    where
-        OutputItem: ?Sized + TryFromSql<Self::QueryResultRow>;
+    ) -> StdResult<Vec<Vec<String>>>;
 }

migra-cli/src/databases/mod.rs

@@ -1,3 +1,32 @@
 mod postgres;
 
 pub use self::postgres::*;
+
+use crate::config::{DatabaseConfig, SupportedDatabaseClient};
+use crate::database::{DatabaseConnection, OpenDatabaseConnection};
+use crate::error::StdResult;
+
+pub(crate) struct DatabaseConnectionManager {
+    config: DatabaseConfig,
+}
+
+impl DatabaseConnectionManager {
+    pub fn new(config: &DatabaseConfig) -> Self {
+        Self {
+            config: config.clone(),
+        }
+    }
+
+    pub fn connect_with_string(&self, connection_string: &str) -> StdResult<Box<dyn DatabaseConnection>> {
+        let conn = match self.config.client()? {
+            SupportedDatabaseClient::Postgres => PostgresConnection::open(&connection_string)?,
+        };
+
+        Ok(Box::new(conn))
+    }
+
+    pub fn connect(&self) -> StdResult<Box<dyn DatabaseConnection>> {
+        let connection_string = self.config.connection_string()?;
+        self.connect_with_string(&connection_string)
+    }
+}

migra-cli/src/databases/postgres.rs

@@ -1,32 +1,19 @@
-
-use crate::migration::{MigrationNames, MigrationManager, is_migrations_table_not_found};
-use postgres::{Client, NoTls};
-use crate::config::Config;
-use std::convert::TryFrom;
+use crate::database::{DatabaseConnection, OpenDatabaseConnection, ToSql};
 use crate::error::StdResult;
-use crate::database::{TryFromSql, ToSql, DatabaseConnection};
+use postgres::{Client, NoTls};
 
 pub struct PostgresConnection {
     client: Client,
 }
 
-impl TryFrom<&Config> for PostgresConnection {
-    type Error = Box<dyn std::error::Error>;
-
-    fn try_from(config: &Config) -> Result<Self, Self::Error> {
-        PostgresConnection::open(&config.database_connection_string()?)
-    }
-}
-
-impl DatabaseConnection for PostgresConnection {
-    type QueryResultRow = postgres::Row;
-    type QueryResult = Vec<Self::QueryResultRow>;
-
+impl OpenDatabaseConnection for PostgresConnection {
     fn open(connection_string: &str) -> StdResult<Self> {
         let client = Client::connect(connection_string, NoTls)?;
         Ok(PostgresConnection { client })
     }
+}
 
+impl DatabaseConnection for PostgresConnection {
     fn batch_execute(&mut self, query: &str) -> StdResult<()> {
         self.client.batch_execute(query)?;
         Ok(())
@@ -44,14 +31,11 @@ impl DatabaseConnection for PostgresConnection {
         Ok(res)
     }
 
-    fn query<'b, OutputItem>(
+    fn query<'b>(
         &mut self,
         query: &str,
         params: &'b [&'b dyn ToSql],
-    ) -> StdResult<Vec<OutputItem>>
-    where
-        OutputItem: ?Sized + TryFromSql<Self::QueryResultRow>,
-    {
+    ) -> StdResult<Vec<Vec<String>>> {
         let stmt = params
             .iter()
             .enumerate()
@@ -59,37 +43,16 @@ impl DatabaseConnection for PostgresConnection {
                 str::replace(&acc, &format!("${}", i), &p.to_sql())
             });
 
-        let res: Self::QueryResult = self.client.query(stmt.as_str(), &[])?;
+        let res = self.client.query(stmt.as_str(), &[])?;
 
         let res = res
             .into_iter()
-            .map(OutputItem::try_from_sql)
-            .collect::<Result<Vec<OutputItem>, _>>()?;
+            .map(|row| {
+                let column: String = row.get(0);
+                vec![column]
+            })
+            .collect::<Vec<_>>();
 
         Ok(res)
     }
 }
-
-impl MigrationNames for MigrationManager<PostgresConnection> {
-    fn applied_migration_names(&mut self) -> StdResult<Vec<String>> {
-        let res = self
-            .conn
-            .query(Self::APPLIED_MIGRATIONS_STMT, &[])
-            .or_else(|e| {
-                if is_migrations_table_not_found(&e) {
-                    Ok(Vec::new())
-                } else {
-                    Err(e)
-                }
-            })?;
-
-        Ok(res.into_iter().collect())
-    }
-}
-
-impl TryFromSql<postgres::Row> for String {
-    fn try_from_sql(row: postgres::Row) -> StdResult<Self> {
-        let res: String = row.get(0);
-        Ok(res)
-    }
-}

migra-cli/src/migration.rs

@@ -1,6 +1,9 @@
+use crate::config::Config;
 use crate::database::DatabaseConnection;
+use crate::databases::DatabaseConnectionManager;
 use crate::path::PathBuilder;
 use crate::StdResult;
+use std::convert::TryFrom;
 use std::fs;
 use std::path::PathBuf;
 
@@ -50,16 +53,26 @@ impl Migration {
     }
 }
 
-pub struct MigrationManager<Conn: DatabaseConnection> {
-    pub(crate) conn: Conn,
+pub struct MigrationManager {
+    pub(crate) conn: Box<dyn DatabaseConnection>,
 }
 
-impl<Conn: DatabaseConnection> MigrationManager<Conn> {
-    pub fn new(conn: Conn) -> Self {
+impl MigrationManager {
+    pub fn new(conn: Box<dyn DatabaseConnection>) -> Self {
         MigrationManager { conn }
     }
 }
 
+impl TryFrom<&Config> for MigrationManager {
+    type Error = Box<dyn std::error::Error>;
+
+    fn try_from(config: &Config) -> Result<Self, Self::Error> {
+        let connection_manager = DatabaseConnectionManager::new(&config.database);
+        let conn = connection_manager.connect()?;
+        Ok(Self { conn })
+    }
+}
+
 pub fn is_migrations_table_not_found<D: std::fmt::Display>(error: D) -> bool {
     error
         .to_string()
@@ -75,6 +88,8 @@ pub trait DatabaseMigrationManager {
 
     fn delete_migration_info(&mut self, name: &str) -> StdResult<u64>;
 
+    fn applied_migration_names(&mut self) -> StdResult<Vec<String>>;
+
     fn upgrade(&mut self, migration: &Migration) -> StdResult<()> {
         let content = migration.upgrade_sql_content()?;
 
@@ -95,10 +110,7 @@ pub trait DatabaseMigrationManager {
     }
 }
 
-impl<Conn> DatabaseMigrationManager for MigrationManager<Conn>
-where
-    Conn: DatabaseConnection,
-{
+impl DatabaseMigrationManager for MigrationManager {
     fn apply_sql(&mut self, sql_content: &str) -> StdResult<()> {
         self.conn.batch_execute(sql_content)
     }
@@ -121,12 +133,22 @@ where
         self.conn
             .execute("DELETE FROM migrations WHERE name = $1", &[&name])
     }
+
+    fn applied_migration_names(&mut self) -> StdResult<Vec<String>> {
+        let res = self
+            .conn
+            .query("SELECT name FROM migrations ORDER BY id DESC", &[])
+            .map(|row| row.first().unwrap().clone())
+            .or_else(|e| {
+                if is_migrations_table_not_found(&e) {
+                    Ok(Vec::new())
+                } else {
+                    Err(e)
                 }
+            })?;
 
-pub trait MigrationNames {
-    const APPLIED_MIGRATIONS_STMT: &'static str = "SELECT name FROM migrations ORDER BY id DESC";
-
-    fn applied_migration_names(&mut self) -> StdResult<Vec<String>>;
+        Ok(res.into_iter().collect())
+    }
 }
 
 pub fn filter_pending_migrations(