Add new @Pattern feature to centralize version-aware code

That is, most of the business code should not be aware that it is being compiled
to multiple versions even when it heavily interacts with MC, preprocessor
statements should be an escape hatch, not the norm.
Similarly, code should not be forced to do `MCVer.getWindow(mc)` instead of the
much more intuitive `mc.getWindow()`, and this new preprocessor (technically remap)
feature makes this possible by defining "search and replace"-like patterns (but
smarter in that they are type-aware) in one or more central places which then
are applied all over the code base.

In a way, this is another step in the automatic back-porting process where
preprocessor statements are used when we cannot yet do something automatically.
Previously we "merely" automatically converted between different mapping, this
new feature now also allows us to automatically perform simple refactoring
tasks like changing field access to a getter+setter (e.g. `mc.getWindow()`), or
changing how a method is called (e.g. `BufferBuilder.begin`), or changing a
method call chain (e.g. `dispatcher.camera.getYaw()`), or most other
search-and-replace-like changes and any combination of those.
The only major limitation is that the replacement itself is not smart, so
arguments must be kept in same order (or be temporarily assigned to local
variables which then can be used in any order).

1 files changed, 23 insertions, 2 deletions

diff --git a/src/main/kotlin/com/replaymod/gradle/remap/Transformer.kt b/src/main/kotlin/com/replaymod/gradle/remap/Transformer.kt
index 85e5acd..dd4215f 100644
--- a/src/main/kotlin/com/replaymod/gradle/remap/Transformer.kt
+++ b/src/main/kotlin/com/replaymod/gradle/remap/Transformer.kt
@@ -41,9 +41,14 @@ import kotlin.system.exitProcess
 
 class Transformer(private val map: MappingSet) {
     var classpath: Array<String>? = null
+    var patternAnnotation: String? = null
 
     @Throws(IOException::class)
-    fun remap(sources: Map<String, String>): Map<String, Pair<String, List<Pair<Int, String>>>> {
+    fun remap(sources: Map<String, String>): Map<String, Pair<String, List<Pair<Int, String>>>> =
+            remap(sources, emptyMap())
+
+    @Throws(IOException::class)
+    fun remap(sources: Map<String, String>, processedSource: Map<String, String>): Map<String, Pair<String, List<Pair<Int, String>>>> {
         val tmpDir = Files.createTempDirectory("remap")
         val disposable = Disposer.newDisposable()
         try {
@@ -90,13 +95,29 @@ class Transformer(private val map: MappingSet) {
                     { scope: GlobalSearchScope -> environment.createPackagePartProvider(scope) }
             )
 
+            val patterns = patternAnnotation?.let { annotationFQN ->
+                val patterns = PsiPatterns(annotationFQN)
+                val annotationName = annotationFQN.substring(annotationFQN.lastIndexOf('.') + 1)
+                for ((unitName, source) in sources) {
+                    if (!source.contains(annotationName)) continue
+                    try {
+                        val patternFile = vfs.findFileByIoFile(tmpDir.resolve(unitName).toFile())!!
+                        val patternPsiFile = psiManager.findFile(patternFile)!!
+                        patterns.read(patternPsiFile, processedSource[unitName]!!)
+                    } catch (e: Exception) {
+                        throw RuntimeException("Failed to read patterns from file \"$unitName\".", e)
+                    }
+                }
+                patterns
+            }
+
             val results = HashMap<String, Pair<String, List<Pair<Int, String>>>>()
             for (name in sources.keys) {
                 val file = vfs.findFileByIoFile(tmpDir.resolve(name).toFile())!!
                 val psiFile = psiManager.findFile(file)!!
 
                 val mapped = try {
-                    PsiMapper(map, psiFile).remapFile(analysis.bindingContext)
+                    PsiMapper(map, psiFile, patterns).remapFile(analysis.bindingContext)
                 } catch (e: Exception) {
                     throw RuntimeException("Failed to map file \"$name\".", e)
                 }