revanced-patcher/src/test/kotlin/app/revanced/patcher/usage/ExampleBytecodePatch.kt

package app.revanced.patcher.usage

import app.revanced.patcher.data.implementation.BytecodeData
import app.revanced.patcher.extensions.addInstructions
import app.revanced.patcher.extensions.or
import app.revanced.patcher.patch.implementation.BytecodePatch
import app.revanced.patcher.patch.implementation.metadata.PackageMetadata
import app.revanced.patcher.patch.implementation.metadata.PatchMetadata
import app.revanced.patcher.patch.implementation.misc.PatchResult
import app.revanced.patcher.patch.implementation.misc.PatchResultSuccess
import app.revanced.patcher.proxy.mutableTypes.MutableField.Companion.toMutable
import app.revanced.patcher.proxy.mutableTypes.MutableMethod.Companion.toMutable
import app.revanced.patcher.signature.MethodMetadata
import app.revanced.patcher.signature.MethodSignature
import app.revanced.patcher.signature.MethodSignatureMetadata
import app.revanced.patcher.signature.PatternScanMethod
import app.revanced.patcher.smali.toInstruction
import app.revanced.patcher.smali.toInstructions
import com.google.common.collect.ImmutableList
import org.jf.dexlib2.AccessFlags
import org.jf.dexlib2.Format
import org.jf.dexlib2.Opcode
import org.jf.dexlib2.builder.MutableMethodImplementation
import org.jf.dexlib2.builder.instruction.BuilderInstruction11x
import org.jf.dexlib2.builder.instruction.BuilderInstruction21c
import org.jf.dexlib2.iface.instruction.formats.Instruction21c
import org.jf.dexlib2.immutable.ImmutableField
import org.jf.dexlib2.immutable.ImmutableMethod
import org.jf.dexlib2.immutable.ImmutableMethodImplementation
import org.jf.dexlib2.immutable.reference.ImmutableFieldReference
import org.jf.dexlib2.immutable.reference.ImmutableStringReference
import org.jf.dexlib2.immutable.value.ImmutableFieldEncodedValue
import org.jf.dexlib2.util.Preconditions

val packageMetadata = listOf(
    PackageMetadata(
        "com.example.examplePackage",
        listOf("0.0.1", "0.0.2")
    )
)

class ExampleBytecodePatch : BytecodePatch(
    PatchMetadata(
        "example-patch",
        "ReVanced example patch",
        "A demonstrative patch to feature the core features of the ReVanced patcher",
        packageMetadata,
        "0.0.1"
    ),
    setOf(
        MethodSignature(
            MethodSignatureMetadata(
                "Example signature",
                MethodMetadata(
                    "TestClass",
                    "main",
                ),
                PatternScanMethod.Fuzzy(1),
                packageMetadata,
                "The main method of TestClass",
                "1.0.0"
            ),
            "V",
            AccessFlags.PUBLIC or AccessFlags.STATIC,
            listOf("[L"),
            listOf(
                Opcode.SGET_OBJECT,
                null,                 // Testing unknown opcodes.
                Opcode.INVOKE_STATIC, // This is intentionally wrong to test the Fuzzy resolver.
                Opcode.RETURN_VOID
            ),
            null
        )
    )
) {
    // This function will be executed by the patcher.
    // You can treat it as a constructor
    override fun execute(data: BytecodeData): PatchResult {
        // Get the resolved method for the signature from the resolver cache
        val result = signatures.first().result!!

        // Get the implementation for the resolved method
        val implementation = result.method.implementation!!

        // Let's modify it, so it prints "Hello, ReVanced! Editing bytecode."
        // Get the start index of our opcode pattern.
        // This will be the index of the instruction with the opcode CONST_STRING.
        val startIndex = result.scanData.startIndex

        implementation.replaceStringAt(startIndex, "Hello, ReVanced! Editing bytecode.")

        // Get the class in which the method matching our signature is defined in.
        val mainClass = data.findClass {
            it.type == result.definingClassProxy.immutableClass.type
        }!!.resolve()

        // Add a new method returning a string
        mainClass.methods.add(
            ImmutableMethod(
                result.definingClassProxy.immutableClass.type,
                "returnHello",
                null,
                "Ljava/lang/String;",
                AccessFlags.PRIVATE or AccessFlags.STATIC,
                null,
                null,
                ImmutableMethodImplementation(
                    1,
                    ImmutableList.of(
                        BuilderInstruction21c(
                            Opcode.CONST_STRING,
                            0,
                            ImmutableStringReference("Hello, ReVanced! Adding bytecode.")
                        ),
                        BuilderInstruction11x(Opcode.RETURN_OBJECT, 0)
                    ),
                    null,
                    null
                )
            ).toMutable()
        )

        // Add a field in the main class
        // We will use this field in our method below to call println on
        // The field holds the Ljava/io/PrintStream->out; field
        mainClass.fields.add(
            ImmutableField(
                mainClass.type,
                "dummyField",
                "Ljava/io/PrintStream;",
                AccessFlags.PRIVATE or AccessFlags.STATIC,
                ImmutableFieldEncodedValue(
                    ImmutableFieldReference(
                        "Ljava/lang/System;",
                        "out",
                        "Ljava/io/PrintStream;"
                    )
                ),
                null,
                null
            ).toMutable()
        )

        // store the fields initial value into the first virtual register
        implementation.replaceInstruction(
            0,
            "sget-object v0, LTestClass;->dummyField:Ljava/io/PrintStream;".toInstruction()
        )

        // Now let's create a new call to our method and print the return value!
        // You can also use the smali compiler to create instructions.
        // For this sake of example I reuse the TestClass field dummyField inside the virtual register 0.
        //
        // Control flow instructions are not supported as of now.
        val instructions = """
                        invoke-static { }, LTestClass;->returnHello()Ljava/lang/String;
                        move-result-object v1
                        invoke-virtual { v0, v1 }, Ljava/io/PrintStream;->println(Ljava/lang/String;)V
                    """.trimIndent().toInstructions()
        implementation.addInstructions(startIndex + 2, instructions)

        // Finally, tell the patcher that this patch was a success.
        // You can also return PatchResultError with a message.
        // If an exception is thrown inside this function,
        // a PatchResultError will be returned with the error message.
        return PatchResultSuccess()
    }

    /**
     * Replace the string for an instruction at the given index with a new one.
     * @param index The index of the instruction to replace the string for
     * @param string The replacing string
     */
    private fun MutableMethodImplementation.replaceStringAt(index: Int, string: String) {
        val instruction = this.instructions[index]

        // Utility method of dexlib2
        Preconditions.checkFormat(instruction.opcode, Format.Format21c)

        // Cast this to an instruction of the format 21c
        // The instruction format can be found in the docs at
        // https://source.android.com/devices/tech/dalvik/dalvik-bytecode
        val strInstruction = instruction as Instruction21c

        // In our case we want an instruction with the opcode CONST_STRING
        // The format is 21c, so we create a new BuilderInstruction21c
        // This instruction will hold the string reference constant in the virtual register of the original instruction
        // For that a reference to the string is needed. It can be created with an ImmutableStringReference.
        // At last, use the method replaceInstruction to replace it at the given index startIndex.
        this.replaceInstruction(
            index,
            BuilderInstruction21c(
                Opcode.CONST_STRING,
                strInstruction.registerA,
                ImmutableStringReference(string)
            )
        )
    }
}