feat(core): Add smart delete functionality

Signed-off-by: Myzel394 <50424412+Myzel394@users.noreply.github.com>

core/base/src/main/java/app/myzel394/numberhub/core/base/Token.kt

@@ -78,6 +78,10 @@ object Token {
                 power, factorial, modulo, percent, sqrt,
             )
         }
+
+        val allWithoutBrackets by lazy {
+            all.filter { it !in listOf(leftBracket, rightBracket) }
+        }
     }
 
     object Func {

core/ui/src/main/java/app/myzel394/numberhub/core/ui/common/textfield/SmartDeleteHandler.kt

@@ -0,0 +1,88 @@
+package app.myzel394.numberhub.core.ui.common.textfield
+
+import androidx.compose.ui.text.TextRange
+import app.myzel394.numberhub.core.base.Token
+
+// Smartly delete tokens
+data class SmartDeleteHandler(
+    private val value: String,
+    private val selection: TextRange,
+) {
+    fun calculateDeleteRange(): TextRange {
+        if (isSelectionARange()) {
+            return selection
+        }
+
+        val position = selection.start
+
+        val rightBracketPosition =
+            findRightBracket(position);
+        val leftBracketPosition =
+            findLeftBracket(position)
+                ?: return TextRange(
+                    rightBracketPosition?.let { takeNextIfIsOperator(it) }
+                        ?.let { if (it > position) 0 else it } ?: 0,
+                    position,
+                );
+
+        if (rightBracketPosition == null) {
+            val rightBracketRelativeToLeftPosition = findRightBracket(leftBracketPosition + 1)
+
+            return if (rightBracketRelativeToLeftPosition == null) {
+                // 1+2(+5|+6
+                TextRange(leftBracketPosition + 1, position)
+            } else {
+                // 1+2(6)+5|+6
+                TextRange(takeNextIfIsOperator(rightBracketRelativeToLeftPosition + 1), position)
+            }
+        }
+
+        return TextRange(leftBracketPosition + 1, findClosingParen(leftBracketPosition));
+    }
+
+    private fun takeNextIfIsOperator(position: Int): Int {
+        if (position + 1 < value.length && Token.Operator.allWithoutBrackets.contains(value[position].toString())) {
+            return position + 1
+        }
+
+        return position
+    }
+
+    private fun isSelectionARange(): Boolean = selection.start != selection.end
+
+    private fun findLeftBracket(startPosition: Int): Int? {
+        for (index in startPosition.coerceAtMost(value.length - 1) downTo 0) {
+            if (value[index] == Token.Operator.leftBracket[0]) {
+                return index
+            }
+        }
+
+        return null
+    }
+
+    private fun findRightBracket(startPosition: Int): Int? {
+        for (index in startPosition.coerceAtMost(value.length - 1) until value.length) {
+            if (value[index] == Token.Operator.rightBracket[0]) {
+                return index
+            }
+        }
+
+        return null
+    }
+
+    // Based of https://stackoverflow.com/a/12752226/9878135
+    fun findClosingParen(openPos: Int): Int {
+        var closePos = openPos
+        var counter = 1
+
+        while (counter > 0) {
+            val c = value[++closePos]
+            if (c == Token.Operator.leftBracket[0]) {
+                counter++
+            } else if (c == Token.Operator.rightBracket[0]) {
+                counter--
+            }
+        }
+        return closePos
+    }
+}

core/ui/src/main/java/app/myzel394/numberhub/core/ui/common/textfield/TextFieldValueExtensions.kt

@@ -127,6 +127,15 @@ fun TextFieldValue.deleteTokens(): TextFieldValue {
     )
 }
 
+fun TextFieldValue.smartDeleteTokens(): TextFieldValue {
+    val deleteRange = SmartDeleteHandler(text, selection).calculateDeleteRange()
+
+    return this.copy(
+        text = text.removeRange(deleteRange.start, deleteRange.end),
+        selection = TextRange(deleteRange.start),
+    )
+}
+
 fun TextFieldValue.placeCursorAtTheEnd(): TextFieldValue = copy(selection = TextRange(text.length))
 
 /**