Implement human-readable cron expression formatter on CronJobsScreen

app/src/main/java/com/m57/hermescontrol/util/CronExpressionFormatter.kt

@@ -0,0 +1,184 @@
+package com.m57.hermescontrol.util
+
+object CronExpressionFormatter {
+    fun cronToHumanReadable(schedule: String): String {
+        val clean = schedule.trim().replace("\\s+".toRegex(), " ")
+        val parts = clean.split(" ")
+        if (parts.size != 5) {
+            return schedule
+        }
+
+        try {
+            val minutePart = parts[0]
+            val hourPart = parts[1]
+            val domPart = parts[2]
+            val monthPart = parts[3]
+            val dowPart = parts[4]
+
+            // 1. Check for common simple shortcuts
+            // Every X minutes: */X * * * *
+            if (minutePart.startsWith("*/") && hourPart == "*" && domPart == "*" && monthPart == "*" &&
+                dowPart == "*"
+            ) {
+                val step = minutePart.substring(2).toIntOrNull()
+                if (step != null) return "Every $step minutes"
+            }
+
+            // Every X hours: 0 */X * * *
+            if (minutePart == "0" && hourPart.startsWith("*/") && domPart == "*" && monthPart == "*" &&
+                dowPart == "*"
+            ) {
+                val step = hourPart.substring(2).toIntOrNull()
+                if (step != null) return "Every $step hours"
+            }
+
+            // Midnight: 0 0 * * *
+            if (minutePart == "0" && hourPart == "0" && domPart == "*" && monthPart == "*" && dowPart == "*") {
+                return "Every day at midnight"
+            }
+
+            // At time every day: 0 H * * * or 0 H,H2 * * *
+            val hoursList = parseField(hourPart, 0, 23)
+            val minutesList = parseField(minutePart, 0, 59)
+
+            val dowNames =
+                listOf("Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday")
+            val monthNames =
+                listOf(
+                    "",
+                    "January",
+                    "February",
+                    "March",
+                    "April",
+                    "May",
+                    "June",
+                    "July",
+                    "August",
+                    "September",
+                    "October",
+                    "November",
+                    "December",
+                )
+
+            // Format time: "09:00", "midnight", etc.
+            fun formatTime(
+                h: Int,
+                m: Int,
+            ): String {
+                if (h == 0 && m == 0) return "midnight"
+                return String.format("%02d:%02d", h, m)
+            }
+
+            // Helper for ordinals: 1st, 2nd, 3rd, 4th...
+            fun formatOrdinal(d: Int): String =
+                when {
+                    d % 100 in 11..13 -> "${d}th"
+                    d % 10 == 1 -> "${d}st"
+                    d % 10 == 2 -> "${d}nd"
+                    d % 10 == 3 -> "${d}rd"
+                    else -> "${d}th"
+                }
+
+            // Day of Month / Month specific cases:
+            // "0 12 1 * *" -> "On the 1st of every month at 12:00"
+            // "0 0 1 1 *" -> "On January 1st at midnight"
+            if (domPart != "*" && monthPart != "*" && dowPart == "*") {
+                val doms = parseField(domPart, 1, 31)
+                val months = parseField(monthPart, 1, 12)
+                if (doms.size == 1 && months.size == 1 && hoursList.size == 1 && minutesList.size == 1) {
+                    val timeStr = formatTime(hoursList[0], minutesList[0])
+                    val monthStr = monthNames[months[0]]
+                    val domStr = formatOrdinal(doms[0])
+                    return if (timeStr == "midnight") {
+                        "On $monthStr $domStr at midnight"
+                    } else {
+                        "On $monthStr $domStr at $timeStr"
+                    }
+                }
+            }
+
+            if (domPart != "*" && monthPart == "*" && dowPart == "*") {
+                val doms = parseField(domPart, 1, 31)
+                if (doms.size == 1 && hoursList.size == 1 && minutesList.size == 1) {
+                    val timeStr = formatTime(hoursList[0], minutesList[0])
+                    val domStr = formatOrdinal(doms[0])
+                    return "On the $domStr of every month at $timeStr"
+                }
+            }
+
+            // Days of week cases:
+            // "30 8 * * 1-5" -> "At 08:30 Monday through Friday"
+            // "0 9 * * 1" -> "Every Monday at 09:00"
+            if (dowPart != "*" && domPart == "*" && monthPart == "*") {
+                if (hoursList.size == 1 && minutesList.size == 1) {
+                    val timeStr = formatTime(hoursList[0], minutesList[0])
+                    if (dowPart.contains("-")) {
+                        val bounds = dowPart.split("-")
+                        if (bounds.size == 2) {
+                            val start = bounds[0].toIntOrNull() ?: -1
+                            val end = bounds[1].toIntOrNull() ?: -1
+                            if (start in 0..7 && end in 0..7) {
+                                val startName = dowNames[start]
+                                val endName = dowNames[end]
+                                return "At $timeStr $startName through $endName"
+                            }
+                        }
+                    }
+                    val dows = parseField(dowPart, 0, 7)
+                    if (dows.size == 1) {
+                        val dowName = dowNames[dows[0]]
+                        return "Every $dowName at $timeStr"
+                    }
+                }
+            }
+
+            // General case:
+            // e.g. "0 9,21 * * *" -> "At 09:00 and 21:00 every day"
+            if (domPart == "*" && monthPart == "*" && dowPart == "*") {
+                if (hoursList.isNotEmpty() && minutesList.size == 1) {
+                    val timeStrings = hoursList.map { formatTime(it, minutesList[0]) }
+                    val timeDesc =
+                        if (timeStrings.size > 1) {
+                            timeStrings.dropLast(1).joinToString(", ") + " and " + timeStrings.last()
+                        } else {
+                            timeStrings[0]
+                        }
+                    return "At $timeDesc every day"
+                }
+            }
+
+            // Fallback
+            return schedule
+        } catch (e: Exception) {
+            return schedule
+        }
+    }
+
+    private fun parseField(
+        field: String,
+        min: Int,
+        max: Int,
+    ): List<Int> {
+        if (field == "*") return (min..max).toList()
+        if (field.contains(",")) {
+            return field
+                .split(",")
+                .flatMap { parseField(it, min, max) }
+                .distinct()
+                .sorted()
+        }
+        if (field.contains("-")) {
+            val parts = field.split("-")
+            if (parts.size == 2) {
+                val start = parts[0].toIntOrNull() ?: return emptyList()
+                val end = parts[1].toIntOrNull() ?: return emptyList()
+                return (start..end).toList()
+            }
+        }
+        val single = field.toIntOrNull()
+        if (single != null) {
+            return listOf(single)
+        }
+        return emptyList()
+    }
+}