Add theory to PSI access and edit lessons

introductionSection/setupLesson/lesson-remote-info.yaml

@@ -0,0 +1 @@
+id: 1521434296

introductionSection/welcomeLesson/lesson-remote-info.yaml

@@ -0,0 +1 @@
+id: 2136442658

psiSection/accessingPsiElementsLesson/accessingPsiElementsClassProgrammingTask/task.md

@@ -1,5 +1,4 @@
-
-You need to implement a function `countKtClasses` which will 
+Using your newly gained knowledge about `PsiTreeUtil.findChildrenOfType` method, implement a function `countKtClasses` which will 
 count number of kotlin classes declared in the given kotlin PSI file.
 
 <div class="hint" title="Which class should I use as aClass parameter?">

psiSection/editingPsiElementsLesson/editingPsiElementsTheoryTask/src/main/kotlin/org/jetbrains/academy/plugin/course/dev/access/Task.kt

@@ -1,4 +1,5 @@
 package org.jetbrains.academy.plugin.course.dev.access
+
 fun main() {
     TODO()
 }

psiSection/editingPsiElementsLesson/editingPsiElementsTheoryTask/task.md

@@ -1 +1,22 @@
-TODO
+All operations with code like adding, deleting or moving methods, renaming variable, you name it, are implemented as PSI editions.
+Please skim the [Modify the PSI](https://plugins.jetbrains.com/docs/intellij/modifying-psi.html) documentation.
+
+Methods to edit PSI Element:
+* [`PsiElement.add()`](https://github.com/JetBrains/intellij-community/blob/19d9a1cc2d9c14df9c3bdee391e9e4795ac25cb9/platform/core-api/src/com/intellij/psi/PsiElement.java#L302) - to add a child to PSI Element into tree. To specify the place in children list use [`PsiElement.addBefore()`](https://github.com/JetBrains/intellij-community/blob/19d9a1cc2d9c14df9c3bdee391e9e4795ac25cb9/platform/core-api/src/com/intellij/psi/PsiElement.java#L312C14-L312C23) and [`PsiElement.addAfter()`](https://github.com/JetBrains/intellij-community/blob/19d9a1cc2d9c14df9c3bdee391e9e4795ac25cb9/platform/core-api/src/com/intellij/psi/PsiElement.java#L322) 
+* [`PsiElement.delete()`](https://github.com/JetBrains/intellij-community/blob/19d9a1cc2d9c14df9c3bdee391e9e4795ac25cb9/platform/core-api/src/com/intellij/psi/PsiElement.java#L373) - to delete PSI Element from tree
+* [`PsiElement.replace()`](https://github.com/JetBrains/intellij-community/blob/19d9a1cc2d9c14df9c3bdee391e9e4795ac25cb9/platform/core-api/src/com/intellij/psi/PsiElement.java#L402) - to replace PSI Element in tree
+
+Also, you create PSI Elements by using:
+* [`PsiElement.copy()`](https://github.com/JetBrains/intellij-community/blob/19d9a1cc2d9c14df9c3bdee391e9e4795ac25cb9/platform/core-api/src/com/intellij/psi/PsiElement.java#L293) - to copy PSI Element subtree
+
+Moreover, there are some PisElement-specific methods like [`KtNamedFunction.setName()`](https://github.com/JetBrains/intellij-community/blob/bf3083ca66771e038eb1c64128b4e508f52acfad/platform/core-api/src/com/intellij/psi/PsiNamedElement.java#L39) as well as all `PsiNamedElement` inheritors.
+
+**IMPORTANT!**
+
+Every PSI modifications need to be wrapped in a [write action and in command](https://github.com/JetBrains/intellij-community/blob/master/platform/core-api/src/com/intellij/openapi/command/WriteCommandAction.java)
+
+```kotlin
+WriteCommandAction.runWriteCommandAction(project) {
+    // Here you can modify PSI Elements
+}
+```

psiSection/editingPsiElementsLesson/renameFunctionProgrammingTask/task.md

@@ -1 +1,27 @@
-TODO
+Sometimes, switching between Python and Kotlin leeds to following code style mistake:
+
+Python developers usually use `snake_case` for methods naming like
+```python
+def sort_values(values):
+```
+While in Kotlin or Java `camelCase` is commonly used
+```Kotlin
+fun sortValues(values: List<Int>) {...}
+```
+
+**Your task will be** to help such multi-language programmers and 
+implement method which renames `snake_case` named method to `camelCase`.
+
+So before your method invocation method looked like:
+```Kotlin
+fun sort_values(values: List<Int>) {...}
+```
+but after 
+```Kotlin
+fun sortValues(values: List<Int>) {...}
+```
+
+<div class="hint" title="How to get project for WriteActionCommand?">
+
+  Every PSI element has link to project, just try `psiElement.project`
+</div>

psiSection/editingPsiElementsLesson/sortMethodsProgrammingTask/src/main/kotlin/org/jetbrains/academy/plugin/course/dev/access/PsiElementsSorter.kt

@@ -11,7 +11,7 @@ fun sortMethods(psiFile: PsiFile) {
     WriteCommandAction.runWriteCommandAction(project) {
         val classes = PsiTreeUtil.findChildrenOfType(psiFile, KtClass::class.java)
 
-        for (ktClass in classes){
+        for (ktClass in classes) {
             val methods = ktClass.declarations.filterIsInstance<KtNamedFunction>()
             val sortedMethods = methods.sortedBy { it.name }.map { it.copy() as KtNamedFunction }
 

psiSection/editingPsiElementsLesson/sortMethodsProgrammingTask/task.md

@@ -1 +1,9 @@
-TODO
+Sometimes, you want to make you code more searchable and sort methods by the alphabetical order. 
+Now you can do it automatically, just several lines of code!
+Implement method which takes PSI class and orders all inner methods in alphabetical order.
+
+
+<div class="hint" title="Where to start?">
+
+Get list of class methods, **copy** them and sort list of copies by name. Then use **replace** original methods one by one with copy which should stand in this position in sorted order.
+</div>