Merge multiple tomls files into one. Add the merging into .gitignore

settings.gradle.kt

/**
  *  Make sure final lib.versions.toml is added into the .gitignore
*/
dependencyResolutionManagement {
    versionCatalogs {
        create("libs") {
            from(mergedToml())
        }
    }
    repositories {
        google()
        mavenCentral()
        gradlePluginPortal()
    }
}

private fun mergedToml(): ConfigurableFileCollection {
    logger.info("Merging toml files...")
    val mergedToml = file("../gradle/libs.versions.toml")
    val tomlFiles: List<File> = file("../gradle").listFiles().orEmpty().filter {
        it.isFile &&
                it.extension == "toml" &&
                it.name != mergedToml.name
    }
    mergeTomlFiles(
        inputFiles = tomlFiles,
        outputFile = mergedToml
    )
    return files("../gradle/libs.versions.toml")
}


private fun mergeTomlFiles(
    inputFiles: Iterable<File>,
    outputFile: File
) {
    val sections = linkedMapOf<String, LinkedHashMap<String, String>>()
    var currentSection: String? = null

    inputFiles.forEach { file ->
        require(file.exists()) { "TOML file not found: ${file.path}" }

        file.forEachLine { raw ->
            val line = raw.trim()

            when {
                line.isEmpty() || line.startsWith("#") -> Unit

                line.startsWith("[") && line.endsWith("]") -> {
                    currentSection = line
                    sections.putIfAbsent(line, linkedMapOf())
                }

                currentSection != null && "=" in line -> {
                    val section = currentSection!!
                    val (key, value) = line.split("=", limit = 2)
                    val map = sections.getValue(section)

                    require(map.putIfAbsent(key.trim(), value.trim()) == null) {
                        "Duplicate key '${key.trim()}' in section $section"
                    }
                }
            }
        }
    }

    outputFile.parentFile.mkdirs()

    outputFile.writeText(
        buildString {
            sections.forEach { (section, entries) ->
                appendLine(section)
                entries.forEach { (k, v) ->
                    appendLine("$k = $v")
                }
                appendLine()
            }
        }
    )
}