/*
 * Copyright 2010-2021 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.fir.analysis.checkers.expression

import org.jetbrains.kotlin.config.LanguageFeature
import org.jetbrains.kotlin.diagnostics.DiagnosticReporter
import org.jetbrains.kotlin.diagnostics.reportOn
import org.jetbrains.kotlin.fir.analysis.checkers.MppCheckerKind
import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors
import org.jetbrains.kotlin.fir.expressions.FirAnonymousFunctionExpression
import org.jetbrains.kotlin.fir.expressions.FirCallableReferenceAccess
import org.jetbrains.kotlin.fir.expressions.FirCheckNotNullCall
import org.jetbrains.kotlin.fir.expressions.FirResolvedQualifier
import org.jetbrains.kotlin.fir.expressions.unwrapSmartcastExpression
import org.jetbrains.kotlin.fir.isEnabled
import org.jetbrains.kotlin.fir.resolve.fullyExpandedType
import org.jetbrains.kotlin.fir.types.canBeNull
import org.jetbrains.kotlin.fir.types.isUnit
import org.jetbrains.kotlin.fir.types.resolvedType

object FirNotNullAssertionChecker : FirCheckNotNullCallChecker(MppCheckerKind.Common) {
    context(context: CheckerContext, reporter: DiagnosticReporter)
    override fun check(expression: FirCheckNotNullCall) {
        val argument = expression.argumentList.arguments.singleOrNull() ?: return
        val argumentWithoutSmartcast = argument.unwrapSmartcastExpression()
        if (argumentWithoutSmartcast is FirAnonymousFunctionExpression && argumentWithoutSmartcast.anonymousFunction.isLambda) {
            reporter.reportOn(expression.source, FirErrors.NOT_NULL_ASSERTION_ON_LAMBDA_EXPRESSION)
            return
        }
        if (argumentWithoutSmartcast is FirCallableReferenceAccess) {
            reporter.reportOn(expression.source, FirErrors.NOT_NULL_ASSERTION_ON_CALLABLE_REFERENCE)
            return
        }
        // TODO: use of Unit is subject to change.
        //  See BodyResolveComponents.typeForQualifier in ResolveUtils.kt which returns Unit for no value type.
        val resolvedType = argument.resolvedType
        if (argumentWithoutSmartcast is FirResolvedQualifier && resolvedType.isUnit) {
            // Would be reported as NO_COMPANION_OBJECT
            return
        }

        val type = resolvedType.fullyExpandedType()

        if (!type.canBeNull(context.session) && LanguageFeature.EnableDfaWarningsInK2.isEnabled()) {
            reporter.reportOn(expression.source, FirErrors.UNNECESSARY_NOT_NULL_ASSERTION, type)
        }
    }
}
