ktlint-ruleset-standard/src/main/kotlin/com/github/shyiko/ktlint/ruleset/standard/SpacingAroundCommaRule.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.impl.source.tree.PsiWhiteSpaceImpl
import org.jetbrains.kotlin.com.intellij.psi.util.PsiTreeUtil
import org.jetbrains.kotlin.psi.psiUtil.startOffset

class SpacingAroundCommaRule : Rule("comma-spacing") {

    override fun visit(
        node: ASTNode,
        autoCorrect: Boolean,
        emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit
    ) {
        if (node is LeafPsiElement && node.textMatches(",") && !node.isPartOfString()) {
            val prevLeaf = PsiTreeUtil.prevLeaf(node, true)
            if (prevLeaf is PsiWhiteSpace) {
                emit(prevLeaf.startOffset, "Unexpected spacing before \"${node.text}\"", true)
                if (autoCorrect) {
                    prevLeaf.node.treeParent.removeChild(prevLeaf.node)
                }
            }
            if (PsiTreeUtil.nextLeaf(node) !is PsiWhiteSpace) {
                emit(node.startOffset + 1, "Missing spacing after \"${node.text}\"", true)
                if (autoCorrect) {
                    node.rawInsertAfterMe(PsiWhiteSpaceImpl(" "))
                }
            }
        }
    }
}