ktlint-ruleset-standard/src/main/kotlin/com/github/shyiko/ktlint/ruleset/standard/NoConsecutiveBlankLinesRule.kt

package com.github.shyiko.ktlint.ruleset.standard

import com.github.shyiko.ktlint.core.Rule
import org.jetbrains.kotlin.com.intellij.lang.ASTNode
import org.jetbrains.kotlin.com.intellij.psi.PsiWhiteSpace
import org.jetbrains.kotlin.com.intellij.psi.impl.source.tree.LeafPsiElement
import org.jetbrains.kotlin.com.intellij.psi.util.PsiTreeUtil

class NoConsecutiveBlankLinesRule : Rule("no-consecutive-blank-lines") {

    override fun visit(
        node: ASTNode,
        autoCorrect: Boolean,
        emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit
    ) {
        if (node is PsiWhiteSpace) {
            val split = node.getText().split("\n")
            if (split.size > 3 || split.size == 3 && PsiTreeUtil.nextLeaf(node) == null /* eof */) {
                emit(node.startOffset + split[0].length + split[1].length + 2, "Needless blank line(s)", true)
                if (autoCorrect) {
                    (node as LeafPsiElement)
                        .rawReplaceWithText("${split.first()}\n${if (split.size > 3) "\n" else ""}${split.last()}")
                }
            }
        }
    }
}