feat: Add warnings for Fuzzy resolver

src/main/kotlin/app/revanced/patcher/Patcher.kt

@@ -4,6 +4,7 @@ import app.revanced.patcher.patch.Patch
 import app.revanced.patcher.patch.PatchMetadata
 import app.revanced.patcher.patch.PatchResultSuccess
 import app.revanced.patcher.proxy.ClassProxy
+import app.revanced.patcher.signature.MethodSignature
 import app.revanced.patcher.signature.resolver.SignatureResolver
 import app.revanced.patcher.util.ListBackedSet
 import lanchon.multidexlib2.BasicDexFileNamer
@@ -116,22 +117,37 @@ class Patcher(
         patcherData.patches.addAll(patches)
     }
 
+    /**
+     * Resolves all signatures.
+     * @throws IllegalStateException if no patches were added or signatures have already been resolved.
+     */
+    fun resolveSignatures(): List<MethodSignature> {
+        if (signaturesResolved) {
+            throw IllegalStateException("Signatures have already been resolved.")
+        }
+        val signatures = patcherData.patches.flatMap { it.signatures }
+        if (signatures.isEmpty()) {
+            throw IllegalStateException("No signatures found to resolve.")
+        }
+        SignatureResolver(patcherData.classes, signatures).resolve()
+        signaturesResolved = true
+        return signatures
+    }
+
     /**
      * Apply patches loaded into the patcher.
      * @param stopOnError If true, the patches will stop on the first error.
      * @return A map of [PatchResultSuccess]. If the [Patch] was successfully applied,
      * [PatchResultSuccess] will always be returned to the wrapping Result object.
      * If the [Patch] failed to apply, an Exception will always be returned to the wrapping Result object.
+     * @throws IllegalStateException if signatures have not been resolved.
      */
     fun applyPatches(
         stopOnError: Boolean = false,
         callback: (String) -> Unit = {}
     ): Map<PatchMetadata, Result<PatchResultSuccess>> {
-
         if (!signaturesResolved) {
-            val signatures = patcherData.patches.flatMap { it.signatures }
-            SignatureResolver(patcherData.classes, signatures).resolve()
-            signaturesResolved = true
+            throw IllegalStateException("Signatures not yet resolved, please invoke Patcher#resolveSignatures() first.")
         }
         return buildMap {
             for (patch in patcherData.patches) {

src/main/kotlin/app/revanced/patcher/signature/MethodSignature.kt

@@ -5,14 +5,14 @@ import org.jf.dexlib2.Opcode
 
 /**
  * Represents the [MethodSignature] for a method.
- * @param methodSignatureMetadata Metadata for this [MethodSignature].
+ * @param metadata Metadata for this [MethodSignature].
  * @param returnType The return type of the method.
  * @param accessFlags The access flags of the method.
  * @param methodParameters The parameters of the method.
  * @param opcodes The list of opcodes of the method.
  */
 class MethodSignature(
-    val methodSignatureMetadata: MethodSignatureMetadata,
+    val metadata: MethodSignatureMetadata,
     internal val returnType: String?,
     internal val accessFlags: Int?,
     internal val methodParameters: Iterable<String>?,
@@ -24,9 +24,13 @@ class MethodSignature(
     var result: SignatureResolverResult? = null // TODO: figure out how to get rid of nullable
         get() {
             return field ?: throw MethodNotFoundException(
-                "Could not resolve required signature ${methodSignatureMetadata.name}"
+                "Could not resolve required signature ${metadata.name}"
             )
         }
+    val resolved: Boolean
+        get() {
+            return result != null
+        }
 }
 
 /**
@@ -70,5 +74,29 @@ interface PatternScanMethod {
     /**
      * When comparing the signature, if [threshold] or more of the opcodes do not match, skip.
      */
-    class Fuzzy(internal val threshold: Int) : PatternScanMethod
+    class Fuzzy(internal val threshold: Int) : PatternScanMethod {
+        /**
+         * A list of warnings the resolver found.
+         *
+         * This list will be allocated when the signature has been found.
+         * Meaning, if the signature was not found,
+         * or the signature was not yet resolved,
+         * the list will be null.
+         */
+        lateinit var warnings: List<Warning>
+
+        /**
+         * Represents a resolver warning.
+         * @param expected The opcode the signature expected it to be.
+         * @param actual The actual opcode it was. Always different from [expected].
+         * @param expectedIndex The index for [expected]. Relative to the instruction list.
+         * @param actualIndex The index for [actual]. Relative to the pattern list from the signature.
+         */
+        data class Warning(
+            val expected: Opcode,
+            val actual: Opcode,
+            val expectedIndex: Int,
+            val actualIndex: Int,
+        )
+    }
 }

src/main/kotlin/app/revanced/patcher/signature/resolver/SignatureResolver.kt

@@ -83,24 +83,26 @@ internal class SignatureResolver(
             val count = instructions.count()
             val pattern = signature.opcodes!!
             val size = pattern.count()
-            var threshold = 0
-            if (signature.methodSignatureMetadata.patternScanMethod is PatternScanMethod.Fuzzy) {
-                threshold = signature.methodSignatureMetadata.patternScanMethod.threshold
-            }
+            val method = signature.metadata.patternScanMethod
+            val threshold = if (method is PatternScanMethod.Fuzzy)
+                method.threshold else 0
 
             for (instructionIndex in 0 until count) {
                 var patternIndex = 0
                 var currentThreshold = threshold
                 while (instructionIndex + patternIndex < count) {
-                    if (
-                        instructions.elementAt(
-                            instructionIndex + patternIndex
-                        ).opcode != pattern.elementAt(patternIndex)
-                        && currentThreshold-- == 0
-                    ) break
+                    val originalOpcode = instructions.elementAt(instructionIndex + patternIndex).opcode
+                    val patternOpcode = pattern.elementAt(patternIndex)
+                    if (originalOpcode != patternOpcode && currentThreshold-- == 0) break
                     if (++patternIndex < size) continue
 
-                    return PatternScanResult(instructionIndex, instructionIndex + patternIndex)
+                    val result = PatternScanResult(instructionIndex, instructionIndex + patternIndex)
+                    if (method is PatternScanMethod.Fuzzy) {
+                        method.warnings = generateWarnings(
+                            signature, instructions, result
+                        )
+                    }
+                    return result
                 }
             }
 
@@ -113,6 +115,24 @@ internal class SignatureResolver(
         ): Boolean {
             return signature.count() != original.size || !(signature.all { a -> original.any { it.startsWith(a) } })
         }
+
+        private fun generateWarnings(
+            signature: MethodSignature,
+            instructions: Iterable<Instruction>,
+            scanResult: PatternScanResult,
+        ) = buildList {
+            val pattern = signature.opcodes!!
+            for ((patternIndex, originalIndex) in (scanResult.startIndex until scanResult.endIndex).withIndex()) {
+                val originalOpcode = instructions.elementAt(originalIndex).opcode
+                val patternOpcode = pattern.elementAt(patternIndex)
+                if (originalOpcode != patternOpcode) {
+                    this.add(PatternScanMethod.Fuzzy.Warning(
+                        originalOpcode, patternOpcode,
+                        originalIndex, patternIndex
+                    ))
+                }
+            }
+        }
     }
 }
 

src/test/kotlin/app/revanced/patcher/PatcherTest.kt

@@ -0,0 +1,37 @@
+package app.revanced.patcher
+
+import app.revanced.patcher.signature.PatternScanMethod
+import app.revanced.patcher.usage.ExamplePatch
+import org.junit.jupiter.api.Test
+import java.io.File
+import kotlin.test.assertTrue
+
+internal class PatcherTest {
+    @Test
+    fun testPatcher() {
+        val patcher = Patcher(File(PatcherTest::class.java.getResource("/test1.dex")!!.toURI()))
+        patcher.addPatches(listOf(ExamplePatch()))
+        for (signature in patcher.resolveSignatures()) {
+            if (!signature.resolved) {
+                throw Exception("Signature ${signature.metadata.name} was not resolved!")
+            }
+            val patternScanMethod = signature.metadata.patternScanMethod
+            if (patternScanMethod is PatternScanMethod.Fuzzy) {
+                val warnings = patternScanMethod.warnings
+                println("Signature ${signature.metadata.name} had ${warnings.size} warnings!")
+                for (warning in warnings) {
+                    println(warning.toString())
+                }
+            }
+        }
+        for ((metadata, result) in patcher.applyPatches()) {
+            if (result.isFailure) {
+                throw Exception("Patch ${metadata.shortName} failed", result.exceptionOrNull()!!)
+            } else {
+                println("Patch ${metadata.shortName} applied successfully!")
+            }
+        }
+        val out = patcher.save()
+        assertTrue(out.isNotEmpty(), "Expected the output of Patcher#save() to not be empty.")
+    }
+}

src/test/kotlin/app/revanced/patcher/usage/ExamplePatch.kt

@@ -31,7 +31,6 @@ import org.jf.dexlib2.immutable.reference.ImmutableStringReference
 import org.jf.dexlib2.immutable.value.ImmutableFieldEncodedValue
 import org.jf.dexlib2.util.Preconditions
 
-@Suppress("unused") // TODO: Add tests
 class ExamplePatch : Patch(
     metadata = PatchMetadata(
         shortName = "example-patch",
@@ -48,7 +47,7 @@ class ExamplePatch : Patch(
                     definingClass = "TestClass",
                     name = "main",
                 ),
-                patternScanMethod = PatternScanMethod.Fuzzy(2),
+                patternScanMethod = PatternScanMethod.Fuzzy(1),
                 compatiblePackages = listOf("com.example.examplePackage"),
                 description = "The main method of TestClass",
                 version = "1.0.0"
@@ -67,7 +66,6 @@ class ExamplePatch : Patch(
     // This function will be executed by the patcher.
     // You can treat it as a constructor
     override fun execute(patcherData: PatcherData): PatchResult {
-
         // Get the resolved method for the signature from the resolver cache
         val result = signatures.first().result!!