// Copyright 2021 Code Intelligence GmbH
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.code_intelligence.jazzer.instrumentor

import org.objectweb.asm.ClassReader
import org.objectweb.asm.ClassVisitor
import org.objectweb.asm.ClassWriter
import org.objectweb.asm.MethodVisitor

internal class HookInstrumentor(
    private val hooks: Iterable<Hook>,
    private val java6Mode: Boolean,
    private val classWithHooksEnabledField: String?,
) : Instrumentor {

    private lateinit var random: DeterministicRandom

    override fun instrument(internalClassName: String, bytecode: ByteArray): ByteArray {
        val reader = ClassReader(bytecode)
        val writer = ClassWriter(reader, ClassWriter.COMPUTE_MAXS)
        random = DeterministicRandom("hook", reader.className)
        val interceptor = object : ClassVisitor(Instrumentor.ASM_API_VERSION, writer) {
            override fun visitMethod(
                access: Int,
                name: String?,
                descriptor: String?,
                signature: String?,
                exceptions: Array<String>?,
            ): MethodVisitor? {
                val mv = cv.visitMethod(access, name, descriptor, signature, exceptions) ?: return null
                return if (shouldInstrument(access)) {
                    makeHookMethodVisitor(
                        internalClassName,
                        access,
                        name,
                        descriptor,
                        mv,
                        hooks,
                        java6Mode,
                        random,
                        classWithHooksEnabledField,
                    )
                } else {
                    mv
                }
            }
        }
        reader.accept(interceptor, ClassReader.EXPAND_FRAMES)
        return writer.toByteArray()
    }
}