String Processing Utilities

fun main() {
    // Split and join
    val csv = "Alice,30,alice@test.com"
    val (name, age, email) = csv.split(",")
    println("Name: $name, Age: $age, Email: $email")

    val words = "the quick brown fox".split(" ")
    println("Capitalized: ${words.joinToString(" ") { it.replaceFirstChar { c -> c.uppercase() } }}")

    // Padding
    val items = listOf("Laptop" to 999, "Mouse" to 29, "Keyboard" to 79)
    println("\n--- Price List ---")
    items.forEach { (item, price) ->
        println("${item.padEnd(15)} \$${price.toString().padStart(6)}")
    }

    // Trim variants
    val messy = "  \t  Hello, World!  \n  "
    println("\ntrimmed: '${messy.trim()}'")
    println("trimStart: '${messy.trimStart()}'")
    println("trimEnd: '${messy.trimEnd()}'")

    // Remove prefix/suffix
    val filename = "report-2024.csv"
    println("\nNo prefix: ${filename.removePrefix("report-")}")
    println("No suffix: ${filename.removeSuffix(".csv")}")
    println("No surrounding: ${filename.removeSurrounding("report-", ".csv")}")

    // Contains, startsWith, endsWith
    println("\nContains '2024': ${filename.contains("2024")}")
    println("Starts with 'report': ${filename.startsWith("report")}")
    println("Ends with '.csv': ${filename.endsWith(".csv")}")

    // Replace
    val template = "Hello {name}, welcome to {app}!"
    val filled = template
        .replace("{name}", "Alice")
        .replace("{app}", "Kotlin")
    println("\n$filled")

    // Regex replace
    val cleaned = "Price: $99.99 (USD)".replace(Regex("[^\\d.]"), "")
    println("Cleaned price: $cleaned")

    // Substring
    val path = "/api/v2/users/123"
    println("\nAfter last '/': ${path.substringAfterLast("/")}")
    println("Before last '/': ${path.substringBeforeLast("/")}")
    println("After first '/api': ${path.substringAfter("/api")}")

    // Char operations
    val input = "Hello World 123!"
    println("\nDigits only: ${input.filter { it.isDigit() }}")
    println("Letters only: ${input.filter { it.isLetter() }}")
    println("No spaces: ${input.filterNot { it.isWhitespace() }}")

    // Count and checks
    println("\nChar count 'l': ${input.count { it == 'l' }}")
    println("All letters? ${"".all { it.isLetter() }}")
    println("Any digit? ${input.any { it.isDigit() }}")
    println("None upper? ${"hello".none { it.isUpperCase() }}")

    // StringBuilder
    val built = buildString {
        append("Line 1")
        appendLine()
        append("Line 2")
        insert(0, "# ")
    }
    println("\n$built")

    // Repeat
    println("\n${"-".repeat(30)}")
    println("Ha".repeat(5))

    // Lines processing
    val multiline = """
        Line 1
        Line 2
        Line 3
    """.trimIndent()
    val numbered = multiline.lines()
        .mapIndexed { i, line -> "${i + 1}. $line" }
        .joinToString("\n")
    println("\n$numbered")

    // Conversion
    println("\ntoInt: ${"42".toInt()}")
    println("toIntOrNull: ${"abc".toIntOrNull()}")
    println("toDouble: ${"3.14".toDouble()}")
    println("reversed: ${"Kotlin".reversed()}")
    println("lowercase: ${"HELLO".lowercase()}")
    println("uppercase: ${"hello".uppercase()}")
}