package com.example.aiapp

/**
 * A span of milliseconds, written the way somebody reads it.
 *
 * A tool's timeout arrives as `480000`, which nobody reads as eight minutes. The rule has two
 * halves, because a short span and a long one are read for different things. Under a minute the
 * question is "roughly how long", so only the largest unit is shown and a fraction carries the rest
 * -- `2.5s`. At a minute or more the question is "how long exactly", so every unit with something
 * in it is written out -- `5d 12h 4m`. Empty units are left out rather than written as zero.
 *
 * Sub-second precision is dropped past a minute: nothing that takes days is measured in
 * milliseconds.
 */
fun formatMillis(ms: Long): String {
    if (ms < 0) return "-" + formatMillis(-ms)
    if (ms < 1000) return "${ms}ms"
    if (ms < 60_000) {
        val tenths = (ms + 50) / 100
        val whole = tenths / 10
        val rest = tenths % 10
        return if (rest == 0L) "${whole}s" else "$whole.${rest}s"
    }
    val seconds = ms / 1000
    val parts =
        listOf(
            "d" to seconds / 86_400,
            "h" to seconds / 3600 % 24,
            "m" to seconds / 60 % 60,
            "s" to seconds % 60,
        )
    return parts.filter { it.second > 0 }.joinToString(" ") { "${it.second}${it.first}" }
}

/** [text] as a span when it is a whole number of milliseconds, and unchanged when it is not. */
fun formatMillisText(text: String): String =
    text.trim().toLongOrNull()?.let { formatMillis(it) } ?: text