Update architecture docs

ARCHITECTURE.md

@@ -15,12 +15,18 @@ flowchart TD
     subgraph BUILTIN_CMDS ["Built-in commands"]
         direction LR
         BLD[scarb build]
+        CLN[scarb clean]
         FMT[scarb fmt]
+        RUN[scarb run]
+        NEW[scarb init/new]
         UPD[scarb add/rm/update]
         MET[scarb metadata]
+        CMD[scarb commands]
+        MAN[scarb manifest-path]
     end
     subgraph EXT_CMDS ["External subcommands system"]
         direction LR
+        CAIRO_LS["Cairo Language Server"]
         PROTOSTAR["scarb test\n(will be built from Protostar)"]
         STARKNET["scarb starknet\n(will be built from Protostar)"]
     end
@@ -58,10 +64,22 @@ classDiagram
     }
     class Config~'c~ {
         - manifest path
+        - app exe path
         - app dirs, like config, cache, PATH, etc.
         - target directory handle
         - ui
+        - logging configuration 
+        - cairo plugins 
+        - current profile
         - global locks
+        - tokio runtime
+    }
+    class CodegenRepository {
+        - compilers
+    }
+    class StarknetContractCompiler {
+    }
+    class LibCompiler {
     }
     class Workspace~'c~ {
         + members() Iter~Package~
@@ -73,6 +91,9 @@ classDiagram
     class Manifest {
         + Summary
         + Vec~Target~
+        + compiler config
+        + profile definitions
+        + scripts
         + not important metadata
     }
     class Summary {
@@ -88,7 +109,7 @@ classDiagram
     class Target {
         + TargetKind
         + String name
-        + BTreeMap~String, *~ params
+        + BTreeMap<String, *> params
     }
     class CompilationUnit {
         Contains all information
@@ -105,6 +126,7 @@ classDiagram
 
     Workspace~'c~ *-- Config~'c~
     Workspace~'c~ o-- * Package
+    Config~'c~ *-- CodegenRepository
     Package -- Manifest
     Manifest -- Summary
     Manifest o-- * Target
@@ -117,12 +139,12 @@ classDiagram
     WorkspaceResolve *-- Package
     CompilationUnit ..> WorkspaceResolve : is created from
     CompilationUnit ..> Target : is created from
+    CodegenRepository *-- StarknetContractCompiler 
+    CodegenRepository *-- LibCompiler 
 ```
 
 ### Sources and the internal registry
 
-**THIS IS NOT FULLY IMPLEMENTED YET.**
-
 A _source_ is an object that finds and downloads remote packages based on names and versions.
 The interface of sources is contained within the `Source` trait.
 There are various `Source` implementation for different methods of downloading packages:
@@ -132,6 +154,8 @@ There are various `Source` implementation for different methods of downloading p
 3. `RegistrySource` downloads packages from package registries.
 4. And more...
 
+**CURRENTLY ONLY PATH AND GIT SOURCES ARE IMPLEMENTED.**
+
 The `Registry` object gathers all `Source` objects in a single mapping, and provides a unified interface for querying
 _any_ package, no matter of its source.
 
@@ -182,9 +206,79 @@ overwritten.
 
 ### Targets
 
-**THIS IS NOT IMPLEMENTED YET.**
+Compilation targets are defined in the `Package` manifest. 
+Each target corresponds to source files which can be compiled into a package, and the way how the package is compiled.
+Packages can have a built-in library target, and/or more externally defined targets.
+When building a package, each target of this package will use exactly the same set of dependencies during compilation.
+By default, if the manifest does not list any targets, Scarb will assume the library target with its default parameters.
 
-      TODO(mkaput): Write this section.
+Each compilation target consists of target kind, source path and parameters table. 
+When building a project, compilation targets are used to construct compilation units.
+
+
+### CodegenRepository
+
+**Currently referred to as CompilerRepository within the implementation.**
+
+To compile Cairo code while building a project into appropriate output targets, Scarb relies on Cairo compiler crate.
+Each compilation target requires the Cairo compiler to be appropriately configured before building the project.  
+Scarb defines preconfigured Cairo compiler instances as structs implementing the `Compiler` trait.
+You can see `StarknetContractCompiler` as an example of such implementation.
+
+The CompilerRepository is used to manage the variety of preconfigured Cairo compilers available to Scarb.
+Each compiler is identified by the target kind that uses it for compilation. 
+At any time, there can be only one compiler registered for a specific compilation target kind.
+When building a project, Scarb retrieves appropriate compiler implementation from CodegenRepository by target kind.
+The compiler will later be used to compile the project into the target output.
+
+### Compilation units
+Please see [scarb documentation](https://docs.swmansion.com/docs/reference/compilation-model) for more information.
+
+### CairoPluginRepository
+
+Thanks to the Cairo compiler architecture, the compilation process can be altered in certain ways by use of 
+the Semantic Plugins interface.
+Within Scarb, this functionality is exposed to users as Cairo plugins.  
+Cairo plugin is a special Scarb package that defines a cairo-plugin target and provides additional interface for 
+instantiating compiler Semantic plugins. 
+The Cairo plugins can be used in Scarb to expand the capabilities of the Cairo compiler, empowering users to implement
+extensions that would only be possible in the compiler codebase before. 
+
+Within Scarb, Cairo plugins are managed through `CairoPluginRepository`, residing in Scarb configuration object.
+The plugin repository stores references to all Cairo plugins that are available during the compilation process.
+Plugins appropriate to be used for building a specific package are applied to the compiler database before the compilation. 
+When using Scarb as a library, Cairo plugins can be defined with configuration builder. 
+If not specified otherwise, Scarb comes with predefined StarkNet Cairo plugin, that can be used for StarkNet contracts
+compilation.
+In the future, Scarb will also provide a way to define Cairo plugins as package dependencies.
+
+**The mechanism for requiring Cairo plugins as package dependencies or compiling them in Scarb runtime is not implemented yet.**
+
+Please see [the RFC document](https://github.com/software-mansion/scarb/discussions/227) for more information.
+
+### RootDatabase management within the compiler
+
+Cairo compiler relies on the `RootDatabase` for management of the compilation state.
+When compiling a single compilation unit, Scarb creates and configures the database, and passes it to the Cairo compiler. 
+The compilation of each unit uses a separate database instance, which is then dropped after the compilation is finished.
+The database is initialized with Cairo project configuration, obtained from the Scarb compilation unit, conditional 
+compilation parameters (see [scarb documentation](https://docs.swmansion.com/docs/reference/conditional-compilation) 
+for more information) and active Cairo plugins.
+
+### Profiles implementation
+
+Profiles provide a way to alter the compiler settings from the Scarb manifest file. 
+Please see the [scarb documentation](https://docs.swmansion.com/scarb/docs/reference/profiles) for general information 
+about profile use cases and syntax. 
+
+Overrides imposed by profile definition are applied towards the appropriate settings while converting `TomlManifest` 
+(serialization of Scarb manifest file) into the `Manifest` object.  
+First, profile definition is read from manifest file, including appropriate profile inheritance attributes.
+The full definition of current profile is obtained by merging the parent profile definition with overrides from manifest.
+Then, the definition is used to override appropriate setting, e.g. Cairo compiler configuration by merging appropriate 
+profile definition sections onto the default configuration.
+
+The merging mentioned above is implemented as a merger of two plain `toml::Value` objects.
 
 [pubgrub-algo-docs]: https://nex3.medium.com/pubgrub-2fb6470504f