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package com.simiacryptus.diff
import org.apache.commons.text.similarity.LevenshteinDistance
object ApxPatchUtil {
fun patch(source: String, patch: String): String {
val sourceLines = source.lines()
val patchLines = patch.lines()
// This will hold the final result
val result = mutableListOf()
// This will keep track of the current line in the source file
var sourceIndex = 0
// Process each line in the patch
for (patchLine in patchLines.map { it.trim() }) {
when {
// If the line starts with "---" or "+++", it's a file indicator line, skip it
patchLine.startsWith("---") || patchLine.startsWith("+++") -> continue
// If the line starts with "@@", it's a hunk header
patchLine.startsWith("@@") -> continue
// If the line starts with "-", it's a deletion, skip the corresponding source line but otherwise treat it as a context line
patchLine.startsWith("-") -> {
sourceIndex = onDelete(patchLine, sourceIndex, sourceLines, result)
}
// If the line starts with "+", it's an addition, add it to the result
patchLine.startsWith("+") -> {
result.add(patchLine.substring(1))
}
// \d+\: ___ is a line number, strip it
patchLine.matches(Regex("\\d+:.*")) -> {
sourceIndex = onContextLine(patchLine.substringAfter(":"), sourceIndex, sourceLines, result)
}
// it's a context line, advance the source cursor
else -> {
sourceIndex = onContextLine(patchLine, sourceIndex, sourceLines, result)
}
}
}
// Append any remaining lines from the source file
while (sourceIndex < sourceLines.size) {
result.add(sourceLines[sourceIndex])
sourceIndex++
}
return result.joinToString("\n")
}
private fun onDelete(
patchLine: String,
sourceIndex: Int,
sourceLines: List,
result: MutableList
): Int {
var sourceIndex1 = sourceIndex
val delLine = patchLine.substring(1)
val sourceIndexSearch = lookAheadFor(sourceIndex1, sourceLines, delLine)
if (sourceIndexSearch > 0 && sourceIndexSearch + 1 < sourceLines.size) {
val contextChunk = sourceLines.subList(sourceIndex1, sourceIndexSearch)
result.addAll(contextChunk)
sourceIndex1 = sourceIndexSearch + 1
} else {
println("Deletion line not found in source file: $delLine")
// Ignore
}
return sourceIndex1
}
private fun onContextLine(
patchLine: String,
sourceIndex: Int,
sourceLines: List,
result: MutableList
): Int {
var sourceIndex1 = sourceIndex
val sourceIndexSearch = lookAheadFor(sourceIndex1, sourceLines, patchLine)
if (sourceIndexSearch > 0 && sourceIndexSearch + 1 < sourceLines.size) {
val contextChunk = sourceLines.subList(sourceIndex1, sourceIndexSearch + 1)
result.addAll(contextChunk)
sourceIndex1 = sourceIndexSearch + 1
} else {
println("Context line not found in source file: $patchLine")
// Ignore
}
return sourceIndex1
}
private fun lookAheadFor(
sourceIndex: Int,
sourceLines: List,
patchLine: String
): Int {
var sourceIndexSearch = sourceIndex
while (sourceIndexSearch < sourceLines.size) {
if (lineMatches(patchLine, sourceLines[sourceIndexSearch++])) return sourceIndexSearch - 1
}
return -1
}
private fun lineMatches(
a: String,
b: String,
factor: Double = 0.1,
): Boolean {
val threshold = (Math.max(a.trim().length, b.trim().length) * factor).toInt()
val levenshteinDistance = LevenshteinDistance(threshold + 1)
val dist = levenshteinDistance.apply(a.trim(), b.trim())
return if (dist >= 0) {
dist <= threshold
} else {
false
}
}
}
