.gitignore

@@ -18,3 +18,5 @@ Cargo.lock
 
 /target
 #Cargo.lock
+
+/.vscode

src/component.rs

@@ -0,0 +1,75 @@
+use std::cell::RefCell;
+use std::ops::Deref;
+use std::rc::Rc;
+
+use super::context::Context;
+use super::error::{AlreadyRegisteredError, Error, NotRegisteredError};
+
+pub struct Component<T: 'static>(Rc<RefCell<T>>);
+
+impl<T: 'static> Component<T> {
+    pub fn from(t: T) -> Self {
+        Component(Rc::new(RefCell::new(t)))
+    }
+}
+
+impl<T: 'static> Deref for Component<T> {
+    type Target = RefCell<T>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl<T: 'static> Clone for Component<T> {
+    fn clone(&self) -> Self {
+        Component(self.0.clone())
+    }
+}
+
+pub trait ContextComponentExtension {
+    fn get_component<T: 'static>(&self) -> Option<Component<T>>;
+
+    fn register_component<T: 'static>(
+        &mut self,
+        t: T,
+    ) -> Result<Component<T>, (AlreadyRegisteredError, T)>;
+
+    fn replace_component<T: 'static>(&self, t: T) -> Result<(Component<T>, T), (Error, T)>;
+}
+
+impl ContextComponentExtension for Context {
+    fn get_component<T: 'static>(&self) -> Option<Component<T>> {
+        self.get::<Component<T>>().cloned()
+    }
+
+    fn register_component<T: 'static>(
+        &mut self,
+        t: T,
+    ) -> Result<Component<T>, (AlreadyRegisteredError, T)> {
+        if self.get::<T>().is_none() {
+            let component = Component::from(t);
+            self.set(component.clone());
+            Ok(component)
+        } else {
+            Err((AlreadyRegisteredError::of_type::<Component<T>>(), t))
+        }
+    }
+
+    fn replace_component<T: 'static>(&self, mut t: T) -> Result<(Component<T>, T), (Error, T)> {
+        if let Some(component) = self.get_component::<T>() {
+            match component.try_borrow_mut() {
+                Err(borrow_mut_error) => return Err((Error::Borrowed(borrow_mut_error), t)),
+                Ok(mut ref_mut) => {
+                    std::mem::swap(&mut *ref_mut, &mut t);
+                    Ok((component.clone(), t))
+                }
+            }
+        } else {
+            Err((
+                Error::NotRegistered(NotRegisteredError::of_type::<Component<T>>()),
+                t,
+            ))
+        }
+    }
+}

src/context.rs

@@ -0,0 +1,65 @@
+use std::any::{Any, TypeId};
+use std::collections::HashMap;
+
+#[derive(Default)]
+pub struct Context {
+    container: HashMap<TypeId, Box<dyn Any>>,
+}
+
+impl Context {
+    pub fn get<T: 'static>(&self) -> Option<&T> {
+        self.container
+            .get(&TypeId::of::<T>())
+            .map(|boxed| boxed.downcast_ref().unwrap())
+    }
+
+    pub fn get_mut<T: 'static>(&mut self) -> Option<&mut T> {
+        self.container
+            .get_mut(&TypeId::of::<T>())
+            .map(|boxed| boxed.downcast_mut().unwrap())
+    }
+
+    pub fn set<T: 'static>(&mut self, t: T) {
+        self.container.insert(TypeId::of::<T>(), Box::from(t));
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_set_and_get() {
+        // Given Context
+        let mut context = Context::default();
+        // And values
+        context.set(1_u32);
+        context.set(String::from("text"));
+
+        // When
+        let num: &u32 = context.get().unwrap();
+        let text: &String = context.get().unwrap();
+
+        // Then
+        assert_eq!(*num, 1);
+        assert_eq!(text, "text");
+    }
+
+    #[test]
+    fn test_set_and_get_mut() {
+        // Given Context
+        let mut context = Context::default();
+        // And values
+        context.set(1_u32);
+
+        // When
+        {
+            let num: &mut u32 = context.get_mut().unwrap();
+            *num = 2;
+        }
+        let num: &u32 = context.get().unwrap();
+
+        // Then
+        assert_eq!(*num, 2);
+    }
+}

src/error.rs

@@ -0,0 +1,64 @@
+use std::any::{type_name, TypeId};
+use std::cell::{BorrowError, BorrowMutError};
+use std::fmt::{Debug, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    AlreadyRegistered(AlreadyRegisteredError),
+    NotRegistered(NotRegisteredError),
+    BorrowedMutably(BorrowError),
+    Borrowed(BorrowMutError),
+    General(String),
+}
+
+pub struct AlreadyRegisteredError(TypeId, &'static str);
+
+impl AlreadyRegisteredError {
+    pub fn of_type<T: 'static>() -> Self {
+        AlreadyRegisteredError(TypeId::of::<T>(), type_name::<T>())
+    }
+
+    pub fn get_msg(&self) -> String {
+        format!("Element of type {} already registered", self.1)
+    }
+
+    pub fn get_type_name(&self) -> &'static str {
+        self.1
+    }
+
+    pub fn get_type_id(&self) -> &TypeId {
+        &self.0
+    }
+}
+
+impl Debug for AlreadyRegisteredError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+        f.write_str(&self.get_msg())
+    }
+}
+
+pub struct NotRegisteredError(TypeId, &'static str);
+
+impl NotRegisteredError {
+    pub fn of_type<T: 'static>() -> Self {
+        NotRegisteredError(TypeId::of::<T>(), type_name::<T>())
+    }
+
+    pub fn get_msg(&self) -> String {
+        format!("Element of type {} not registered", self.1)
+    }
+
+    pub fn get_type_name(&self) -> &'static str {
+        self.1
+    }
+
+    pub fn get_type_id(&self) -> &TypeId {
+        &self.0
+    }
+}
+
+impl Debug for NotRegisteredError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+        f.write_str(&self.get_msg())
+    }
+}

src/factory.rs

@@ -0,0 +1,163 @@
+use std::any::type_name;
+use std::fmt::{Debug, Formatter, Result as FmtResult};
+use std::ops::Deref;
+use std::rc::Rc;
+
+use super::component::{Component, ContextComponentExtension};
+use super::context::Context;
+use super::error::{AlreadyRegisteredError, Error, NotRegisteredError};
+
+pub trait FromContext<T: 'static> {
+    fn from_context(&self, context: &mut Context) -> Result<T, Error>;
+}
+
+impl<T: 'static, FN: Fn(&mut Context) -> Result<T, Error>> FromContext<T> for FN {
+    fn from_context(&self, context: &mut Context) -> Result<T, Error> {
+        self(context)
+    }
+}
+
+pub struct Factory<T: 'static>(Rc<dyn FromContext<T>>);
+
+impl<T: 'static> Debug for Factory<T> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        write!(f, "Factory for component of type {}", type_name::<T>())
+    }
+}
+
+impl<T: 'static> Factory<T> {
+    pub fn from<FC: FromContext<T> + 'static>(from_context: FC) -> Self {
+        Factory(Rc::new(from_context))
+    }
+}
+
+impl<T: 'static> Clone for Factory<T> {
+    fn clone(&self) -> Self {
+        Factory(self.0.clone())
+    }
+}
+
+impl<T: 'static> Deref for Factory<T> {
+    type Target = dyn FromContext<T>;
+
+    fn deref(&self) -> &Self::Target {
+        self.0.deref()
+    }
+}
+
+pub trait ContextFactoryExtension {
+    fn get_factory<T: 'static>(&self) -> Option<Factory<T>>;
+
+    fn register_factory<T: 'static>(
+        &mut self,
+        factory: Factory<T>,
+    ) -> Result<(), (AlreadyRegisteredError, Factory<T>)>;
+
+    fn replace_factory<T: 'static>(
+        &mut self,
+        factory: Factory<T>,
+    ) -> Result<Factory<T>, (NotRegisteredError, Factory<T>)>;
+
+    fn build<T: 'static>(&mut self) -> Result<T, Error>;
+
+    fn build_and_register_component<T: 'static>(&mut self) -> Result<Component<T>, Error>;
+
+    fn get_or_build_component<T: 'static>(&mut self) -> Result<Component<T>, Error>;
+}
+
+impl ContextFactoryExtension for Context {
+    fn get_factory<T: 'static>(&self) -> Option<Factory<T>> {
+        self.get().cloned()
+    }
+
+    fn register_factory<T: 'static>(
+        &mut self,
+        factory: Factory<T>,
+    ) -> Result<(), (AlreadyRegisteredError, Factory<T>)> {
+        if self.get::<Factory<T>>().is_none() {
+            self.set(factory);
+            Ok(())
+        } else {
+            Err((AlreadyRegisteredError::of_type::<Factory<T>>(), factory))
+        }
+    }
+
+    fn replace_factory<T: 'static>(
+        &mut self,
+        mut factory: Factory<T>,
+    ) -> Result<Factory<T>, (NotRegisteredError, Factory<T>)> {
+        match self.get_mut::<Factory<T>>() {
+            Some(mut_ref) => {
+                std::mem::swap(mut_ref, &mut factory);
+                Ok(factory)
+            }
+            None => Err((NotRegisteredError::of_type::<Factory<T>>(), factory)),
+        }
+    }
+
+    fn build<T: 'static>(&mut self) -> Result<T, Error> {
+        match self.get_factory::<T>() {
+            Some(factory) => factory.from_context(self),
+            None => Err(Error::NotRegistered(NotRegisteredError::of_type::<
+                Factory<T>,
+            >())),
+        }
+    }
+
+    fn build_and_register_component<T: 'static>(&mut self) -> Result<Component<T>, Error> {
+        if self.get_component::<T>().is_some() {
+            return Err(Error::AlreadyRegistered(AlreadyRegisteredError::of_type::<
+                Component<T>,
+            >()));
+        }
+        match self.build::<T>() {
+            Ok(t) => self
+                .register_component(t)
+                .map_err(|(error, _)| Error::AlreadyRegistered(error)),
+            Err(error) => Err(error),
+        }
+    }
+
+    fn get_or_build_component<T: 'static>(&mut self) -> Result<Component<T>, Error> {
+        if let Some(component) = self.get_component::<T>() {
+            Ok(component)
+        } else {
+            self.build_and_register_component()
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_factory() {
+        // Given structs
+        #[derive(Debug)]
+        struct Config {
+            initial_count: u32,
+        };
+        #[derive(Debug)]
+        struct Counter(u32);
+        // and context
+        let mut context = Context::default();
+        // and factories registered in context
+        let config_factory = Factory::from(|_: &mut Context| Ok(Config { initial_count: 5 }));
+        context.register_factory(config_factory).unwrap();
+        let counter_factory = Factory::from(|context: &mut Context| {
+            let config_component = context.get_or_build_component::<Config>()?;
+            let initial_count = config_component.borrow().initial_count;
+            Ok(Counter(initial_count))
+        });
+        context.register_factory(counter_factory).unwrap();
+
+        // When
+        let counter_component = context.get_or_build_component::<Counter>().unwrap();
+        let config_component = context.get_component::<Config>().unwrap();
+
+        // Then
+        assert_eq!(counter_component.borrow().0, 5);
+        assert_eq!(config_component.borrow().initial_count, 5);
+    }
+}

src/lib.rs

@@ -1,7 +1,4 @@
-#[cfg(test)]
-mod tests {
-    #[test]
-    fn it_works() {
-        assert_eq!(2 + 2, 4);
-    }
-}
+pub mod component;
+pub mod context;
+pub mod error;
+pub mod factory;