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/*
 * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
 * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
 */

package org.jetbrains.kotlin.backend.wasm.dce

import org.jetbrains.kotlin.backend.wasm.WasmBackendContext
import org.jetbrains.kotlin.backend.wasm.ir2wasm.isExported
import org.jetbrains.kotlin.ir.IrElement
import org.jetbrains.kotlin.ir.backend.js.dce.DceDumpNameCache
import org.jetbrains.kotlin.ir.backend.js.utils.*
import org.jetbrains.kotlin.ir.declarations.*
import org.jetbrains.kotlin.ir.expressions.IrBody
import org.jetbrains.kotlin.ir.util.hasAnnotation
import org.jetbrains.kotlin.ir.visitors.IrElementVisitorVoid
import org.jetbrains.kotlin.ir.visitors.acceptChildrenVoid
import org.jetbrains.kotlin.ir.visitors.acceptVoid
import org.jetbrains.kotlin.js.config.JSConfigurationKeys

fun eliminateDeadDeclarations(modules: List, context: WasmBackendContext, dceDumpNameCache: DceDumpNameCache) {
    val printReachabilityInfo =
        context.configuration.getBoolean(JSConfigurationKeys.PRINT_REACHABILITY_INFO) ||
                java.lang.Boolean.getBoolean("kotlin.wasm.dce.print.reachability.info")

    val dumpReachabilityInfoToFile: String? =
        context.configuration.get(JSConfigurationKeys.DUMP_REACHABILITY_INFO_TO_FILE)
            ?: System.getProperty("kotlin.wasm.dce.dump.reachability.info.to.file")

    val usefulDeclarations = WasmUsefulDeclarationProcessor(
        context = context,
        printReachabilityInfo = printReachabilityInfo,
        dumpReachabilityInfoToFile
    ).collectDeclarations(rootDeclarations = buildRoots(modules, context), dceDumpNameCache)

    val remover = WasmUselessDeclarationsRemover(context, usefulDeclarations)
    modules.onAllFiles {
        acceptVoid(remover)
    }
}

private fun buildRoots(modules: List, context: WasmBackendContext): List = buildList {
    val declarationsCollector = object : IrElementVisitorVoid {
        override fun visitElement(element: IrElement): Unit = element.acceptChildrenVoid(this)
        override fun visitBody(body: IrBody): Unit = Unit // Skip

        override fun visitDeclaration(declaration: IrDeclarationBase) {
            super.visitDeclaration(declaration)
            add(declaration)
        }
    }

    modules.onAllFiles {
        declarations.forEach { declaration ->
            when (declaration) {
                is IrFunction -> {
                    if (declaration.isExported()) {
                        declaration.acceptVoid(declarationsCollector)
                    }
                }
                is IrField -> {
                    val propertyForField = declaration.correspondingPropertySymbol?.owner
                    if (propertyForField != null && propertyForField.hasAnnotation(context.wasmSymbols.eagerInitialization)) {
                        add(declaration)
                    }
                }
            }
        }
    }

    add(context.irBuiltIns.throwableClass.owner)
    add(context.findUnitGetInstanceFunction())

    addAll(context.testFunsPerFile.values)
    context.fileContexts.values.forEach {
        it.mainFunctionWrapper?.let(::add)
    }

    if (context.isWasmJsTarget) {
        add(context.wasmSymbols.jsRelatedSymbols.createJsException.owner)
    }

    // Remove all functions used to call a kotlin closure from JS side, reachable ones will be added back later.
    context.fileContexts.values.forEach {
        removeAll(it.closureCallExports.values)
    }
}

private inline fun List.onAllFiles(body: IrFile.() -> Unit) {
    forEach { module ->
        module.files.forEach { file ->
            file.body()
        }
    }
}