Fleshed out "Library" page

reference_guide/project_model/library.md

@@ -18,10 +18,10 @@ Package
 [libraries](upsource:///platform/projectModel-api/src/com/intellij/openapi/roots/libraries)
 provides functionality for working with project libraries and jars.
 
-### How do I get a list of libraries available within a module?
+### How do I get a list of libraries a module depends on?
 
-To get the list of libraries, use `OrderEnumerator.forEachLibrary` method.
-To clarify this, consider the following code snippet that illustrates how to output the list of libraries for the specified module:
+To get the list of libraries that a module depends on, use `OrderEnumerator.forEachLibrary` method. 
+The following snippet demonstrates how you can do this:
 
 ```java
 final List<String> libraryNames = new ArrayList<String>();
@@ -32,7 +32,19 @@ ModuleRootManager.getInstance(module).orderEntries().forEachLibrary(library -> {
 Messages.showInfoMessage(StringUtil.join(libraryNames, "\n"), "Libraries in Module");
 ```
 
-This sample code outputs a list of libraries for the `module` module.
+This sample code outputs a list of libraries that the `module` module depends on.
+
+### How do I get a list of all libraries?
+
+To manage the lists of application and project libraries, the [LibraryTable](upsource:///platform/projectModel-api/src/com/intellij/openapi/roots/libraries/LibraryTable.java) 
+class is used. The list of application-level library tables is accessed by calling `LibraryTablesRegistrar.getInstance().getLibraryTable()`,
+whereas the list of project-level library tables is accessed through `LibraryTablesRegistrar.getInstance().getLibraryTable(Project)`.
+Once you have a `LibraryTable`, you can get the libraries in it by calling `LibraryTable.getLibraries()`.
+
+To get the list of all module libraries defined in a given module, use the following API:
+```java
+OrderEntryUtil.getModuleLibraries(ModuleRootManager.getInstance(module));
+```
 
 ### How do I get the library content?
 
@@ -53,6 +65,32 @@ Messages.showInfoMessage(roots.toString(), "Library Info");
 
 In this sample code, `lib` is of the [Library](upsource:///platform/projectModel-api/src/com/intellij/openapi/roots/libraries/Library.java) type.
 
+### How do I create a library?
+
+To create a library, you need to perform the following steps:
+
+  * Obtain the library table to which you want to add the library. Use one of the following, depending on the library level:
+      * `LibraryTablesRegistrar.getInstance().getLibraryTable()`
+      * `LibraryTablesRegistrar.getInstance().getLibraryTable(Project)`
+      * `ModuleRootManager.getInstance(module).getModifiableModel().getModuleLibraryTable()`
+  * Create the library by calling `LibraryTable.createLibrary()`
+  * Add contents to the library (see below)
+  * For a module-level library, commit the modifiable model returned by `ModuleRootManager.getInstance(module).getModifiableModel()`.
+  
+For module-level libraries, you can also use simplified APIs in the [ModuleRootModificationUtil](upsource:///platform/projectModel-api/src/com/intellij/openapi/roots/ModuleRootModificationUtil.java)
+class to add a library with a single API call. You can find an example of using these APIs in the [sample plugin](https://github.com/JetBrains/intellij-sdk-docs/blob/master/code_samples/project_model/src/com/intellij/tutorials/project/model/ModificationAction.java).
+
+### How do I add contents to a library or modify it?
+
+To add or change the roots of a library, you need to perform the following steps:
+
+  * Get a **modifiable model** for the library, using `Library.getModifiableModel()`
+  * Use methods such as `Library.ModifiableModel.addRoot()` to perform the necessary changes
+  * Commit the model using `Library.ModifiableModel.commit()`.
+  
+### How do I add a library dependency to a module?
+
+Use `ModuleRootModificationUtil.addDependency(module, library)`.  
 
 ### Checking Belonging to a Library