make SQL entities to create their projection

Author: ghubertpalo

mithril-common/src/database/db_version.rs

@@ -8,7 +8,7 @@ use std::{
 use chrono::NaiveDateTime;
 use sqlite::{Connection, Row, Value};
 
-use crate::sqlite::{HydrationError, Projection, ProjectionField, Provider, SqLiteEntity};
+use crate::sqlite::{HydrationError, Projection, Provider, SqLiteEntity};
 
 use super::DbVersion;
 
@@ -69,35 +69,9 @@ impl SqLiteEntity for DatabaseVersion {
             .map_err(|e| HydrationError::InvalidData(format!("{}", e)))?,
         })
     }
-}
-
-impl PartialOrd for DatabaseVersion {
-    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
-        if self.application_type != other.application_type {
-            None
-        } else {
-            self.version.partial_cmp(&other.version)
-        }
-    }
-}
 
-/// Projection dedicated to [DatabaseVersion] entities.
-struct DatabaseVersionProjection {
-    fields: Vec<ProjectionField>,
-}
-
-impl Projection for DatabaseVersionProjection {
-    fn set_field(&mut self, field: ProjectionField) {
-        self.fields.push(field);
-    }
-
-    fn get_fields(&self) -> &Vec<ProjectionField> {
-        &self.fields
-    }
-}
-impl DatabaseVersionProjection {
-    pub fn new() -> Self {
-        let mut projection = Self { fields: Vec::new() };
+    fn get_projection() -> Projection {
+        let mut projection = Projection::default();
         projection.add_field("version", "{:db_version:}.version", "text");
         projection.add_field(
             "application_type",
@@ -110,18 +84,28 @@ impl DatabaseVersionProjection {
     }
 }
 
+impl PartialOrd for DatabaseVersion {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        if self.application_type != other.application_type {
+            None
+        } else {
+            self.version.partial_cmp(&other.version)
+        }
+    }
+}
+
 /// Provider for the [DatabaseVersion] entities using the `DatabaseVersionProjection`.
 pub struct DatabaseVersionProvider<'conn> {
     connection: &'conn Connection,
-    projection: DatabaseVersionProjection,
+    projection: Projection,
 }
 
 impl<'conn> DatabaseVersionProvider<'conn> {
     /// [DatabaseVersionProvider] constructor.
     pub fn new(connection: &'conn Connection) -> Self {
         Self {
             connection,
-            projection: DatabaseVersionProjection::new(),
+            projection: DatabaseVersion::get_projection(),
         }
     }
 
@@ -169,7 +153,7 @@ insert into db_version (application_type, version) values ('{application_type}',
 impl<'conn> Provider<'conn> for DatabaseVersionProvider<'conn> {
     type Entity = DatabaseVersion;
 
-    fn get_projection(&self) -> &dyn Projection {
+    fn get_projection(&self) -> &Projection {
         &self.projection
     }
 
@@ -197,15 +181,15 @@ where {where_clause}
 /// This will perform an UPSERT and return the updated entity.
 pub struct DatabaseVersionUpdater<'conn> {
     connection: &'conn Connection,
-    projection: DatabaseVersionProjection,
+    projection: Projection,
 }
 
 impl<'conn> DatabaseVersionUpdater<'conn> {
     /// [DatabaseVersionUpdater] constructor.
     pub fn new(connection: &'conn Connection) -> Self {
         Self {
             connection,
-            projection: DatabaseVersionProjection::new(),
+            projection: DatabaseVersion::get_projection(),
         }
     }
 
@@ -227,7 +211,7 @@ impl<'conn> DatabaseVersionUpdater<'conn> {
 impl<'conn> Provider<'conn> for DatabaseVersionUpdater<'conn> {
     type Entity = DatabaseVersion;
 
-    fn get_projection(&self) -> &dyn Projection {
+    fn get_projection(&self) -> &Projection {
         &self.projection
     }
 
@@ -257,7 +241,7 @@ mod tests {
 
     #[test]
     fn test_projection() {
-        let projection = DatabaseVersionProjection::new();
+        let projection = DatabaseVersion::get_projection();
         let mut aliases: HashMap<String, String> = HashMap::new();
         let _ = aliases.insert("{:db_version:}".to_string(), "whatever".to_string());
 

mithril-common/src/sqlite/entity.rs

@@ -1,6 +1,8 @@
 use sqlite::Row;
 use thiserror::Error;
 
+use super::Projection;
+
 /// SqLite hydration error
 #[derive(Error, Debug, Clone)]
 pub enum HydrationError {
@@ -25,4 +27,7 @@ pub trait SqLiteEntity {
     fn hydrate(row: Row) -> Result<Self, HydrationError>
     where
         Self: Sized;
+
+    /// Construct a [Projection] that will allow to hydrate this `SqLiteEntity`.
+    fn get_projection() -> Projection;
 }

mithril-common/src/sqlite/projection.rs

@@ -39,27 +39,34 @@ impl ProjectionField {
 /// Projection is a definition of field mapping during a query.
 /// Fields come from one or several source structures (can be tables, views or
 /// sub queries) and are mapped to a Provider query as output.
-pub trait Projection {
+pub struct Projection {
+    fields: Vec<ProjectionField>,
+}
+
+impl Projection {
+    /// Instanciate a new Projection
+    pub fn new(fields: Vec<ProjectionField>) -> Self {
+        Self { fields }
+    }
+
     /// Add a new field to the definition. This is one of the projection
     /// building tool to create a projection out of an existing structure.
     /// This is a blanket implementation.
-    fn add_field(&mut self, field_name: &str, definition: &str, output_type: &str) {
-        self.set_field(ProjectionField {
+    pub fn add_field(&mut self, field_name: &str, definition: &str, output_type: &str) {
+        self.fields.push(ProjectionField {
             name: field_name.to_string(),
             definition: definition.to_string(),
             output_type: output_type.to_string(),
         })
     }
 
-    /// This method is requested by `add_field` to actually save the state in
-    /// the current Provider implementation.
-    fn set_field(&mut self, field: ProjectionField);
-
     /// Returns the list of the ProjectionFields of this Projection.
-    fn get_fields(&self) -> &Vec<ProjectionField>;
+    pub fn get_fields(&self) -> &Vec<ProjectionField> {
+        &self.fields
+    }
 
     /// Turn the Projection into a string suitable for use in SQL queries.
-    fn expand(&self, aliases: HashMap<String, String>) -> String {
+    pub fn expand(&self, aliases: HashMap<String, String>) -> String {
         let mut fields: String = self
             .get_fields()
             .iter()
@@ -75,40 +82,24 @@ pub trait Projection {
     }
 }
 
+impl Default for Projection {
+    fn default() -> Self {
+        Self::new(Vec::new())
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
 
-    struct TestProjection {
-        fields: Vec<ProjectionField>,
-    }
-
-    impl TestProjection {
-        pub fn new() -> Self {
-            let mut projection = Self { fields: Vec::new() };
-
-            projection.add_field("test_id", "{:test:}.test_id", "integer");
-            projection.add_field("name", "{:test:}.name", "text");
-            projection.add_field("created_at", "{:test:}.created_at", "timestamp");
-            projection.add_field("thing_count", "count({:thing:}.*)", "integer");
-
-            projection
-        }
-    }
-
-    impl Projection for TestProjection {
-        fn get_fields(&self) -> &Vec<ProjectionField> {
-            &self.fields
-        }
-
-        fn set_field(&mut self, field: ProjectionField) {
-            self.fields.push(field);
-        }
-    }
-
     #[test]
     fn simple_projection() {
-        let projection = TestProjection::new();
+        let mut projection = Projection::default();
+        projection.add_field("test_id", "{:test:}.test_id", "integer");
+        projection.add_field("name", "{:test:}.name", "text");
+        projection.add_field("created_at", "{:test:}.created_at", "timestamp");
+        projection.add_field("thing_count", "count({:thing:}.*)", "integer");
+
         let aliases: HashMap<String, String> = [("{:test:}", "pika"), ("{:thing:}", "thing_alias")]
             .into_iter()
             .map(|(a, b)| (a.to_string(), b.to_string()))

mithril-common/src/sqlite/provider.rs

@@ -14,7 +14,7 @@ pub trait Provider<'conn> {
     fn get_connection(&'conn self) -> &'conn Connection;
 
     /// Share the projection.
-    fn get_projection(&self) -> &dyn Projection;
+    fn get_projection(&self) -> &Projection;
 
     /// Perform the parametrized definition query.
     fn find(
@@ -41,7 +41,7 @@ pub trait Provider<'conn> {
 
 #[cfg(test)]
 mod tests {
-    use super::super::{entity::HydrationError, ProjectionField, SqLiteEntity};
+    use super::super::{entity::HydrationError, SqLiteEntity};
     use super::*;
 
     #[derive(Debug, PartialEq)]
@@ -61,25 +61,9 @@ mod tests {
                 maybe_null: row.get::<Option<i64>, _>(3),
             })
         }
-    }
-
-    pub struct TestProjection {
-        fields: Vec<ProjectionField>,
-    }
-
-    impl Projection for TestProjection {
-        fn get_fields(&self) -> &Vec<ProjectionField> {
-            &self.fields
-        }
-
-        fn set_field(&mut self, field: ProjectionField) {
-            self.fields.push(field);
-        }
-    }
 
-    impl TestProjection {
-        pub fn new() -> Self {
-            let mut projection = Self { fields: Vec::new() };
+        fn get_projection() -> Projection {
+            let mut projection = Projection::default();
 
             projection.add_field("text_data", "{:test:}.text_data", "text");
             projection.add_field("real_data", "{:test:}.real_data", "real");
@@ -92,14 +76,14 @@ mod tests {
 
     struct TestEntityProvider {
         connection: Connection,
-        projection: TestProjection,
+        projection: Projection,
     }
 
     impl TestEntityProvider {
         pub fn new(connection: Connection) -> Self {
             Self {
                 connection,
-                projection: TestProjection::new(),
+                projection: TestEntity::get_projection(),
             }
         }
     }
@@ -111,7 +95,7 @@ mod tests {
             &self.connection
         }
 
-        fn get_projection(&self) -> &dyn Projection {
+        fn get_projection(&self) -> &Projection {
             &self.projection
         }
 
@@ -128,14 +112,14 @@ mod tests {
 
     struct TestEntityUpdateProvider {
         connection: Connection,
-        projection: TestProjection,
+        projection: Projection,
     }
 
     impl TestEntityUpdateProvider {
         pub fn new(connection: Connection) -> Self {
             Self {
                 connection,
-                projection: TestProjection::new(),
+                projection: TestEntity::get_projection(),
             }
         }
     }
@@ -147,7 +131,7 @@ mod tests {
             &self.connection
         }
 
-        fn get_projection(&self) -> &dyn Projection {
+        fn get_projection(&self) -> &Projection {
             &self.projection
         }