Diff string

Diff.kt

class StringDifference(sw: String, sn: String, cursorStartBefore: Int = 0, cursorEndBefore: Int = 0, cursorStartAfter: Int = 0, cursorEndAfter: Int = 0) {
    var start: Int = 0
    var count: Int = 0
    var after: Int = 0
    var added: Int = 0
        get() = if (count == 0) after else 0

    var removed = 0
        get() = if (after == 0) count else 0

    var replaced = 0
        get() = if (count != 0 && after != 0) after else 0

    var noDiff = false
        get() = count == 0 && after == 0

    init {
        var end = 0
        var lw = sw.length - 1
        var ln = sn.length - 1
        val min = Math.min(lw, ln) + 1

        for (i in cursor..min) {
            start = i
            if (i >= min) break
            if (sw[i] != sn[i]) {
                break
            }
        }

        for (i in 0..min) {
            end = i
            if (i >= min) break
            if (sw[lw - i] != sn[ln - i]) break
        }

//        "x", "xxx"
        if (ln > lw) {
            val endFromStart = ln - end + 1
            if (endFromStart < start) {
                val s = Math.min(endFromStart, start)
                val e = Math.max(endFromStart, start)
                start = s
                end = e
            }
        }
        count = Math.max(lw - ln, 0)
        after = Math.max(ln - lw, 0)
        val lenDiff = ln - lw
//        if (after < lenDiff) after = lenDiff
//        if (count < -lenDiff) count = -lenDiff
    }
}

test.kt

    @Test
    fun addition_isCorrect() {
        testDiff("x", "xxx", 1, 2, 0)
        testDiff("jj", "jjj", 1, 2, 0)
        testDiff("xxxxxxxxx", "xxxxxxxxxxxxxx", 3, 5, 0)
        testDiff("ttttt", "tttttttt", 1, 3, 0)
        testDiff("xxx", "x", 1, 0, 2)
        testDiff("f", "fafa", 1, 3, 0)
        testDiff("@Serg", "@@Serg", 0, 1, 0)
        testDiff("@Serg", " @@Serg", 0, 2, 0)
        testDiff("@S", "@S @", 2, 2, 0)
        testDiff("x @Serg", "x @@Serg", 2, 1, 0)
        testDiff("@Sergey Petrov ", "@Sergey Petrov g", 15, 1, 0)
    }

    fun testDiff(s1: String, s2: String, strt: Int, add: Int, rem: Int) {
        println("add \"$s1\" \"$s2\"")
        val diff = StringDifference(s1, s2)
        with(diff) { println("added=${added}($add), removed=${removed}($rem), replaced=${replaced}, start=${start}($strt), count=${count}, after=${after}") }
//        assertTrue(strt == diff.start)
//        assertTrue(diff.count >= 0)
//        assertTrue(diff.after >= 0)
//        assertTrue(diff.added == add)
//        assertTrue(diff.removed == rem)
    }