Normalize shell and patch tool cards

app/androidApp/src/main/kotlin/com/example/aiapp/Highlighter.kt

@@ -7,6 +7,8 @@ import androidx.compose.ui.text.buildAnnotatedString
 
 /** What a span of code is, in the terms the palette has a colour for. */
 enum class Kind {
+    ADDITION,
+    DELETION,
     KEYWORD,
     STRING,
     LITERAL,
@@ -24,6 +26,8 @@ data class Span(val start: Int, val end: Int, val kind: Kind)
  * one instance and lives with the rest of the palette.
  */
 data class SyntaxPalette(
+    val addition: Color,
+    val deletion: Color,
     val keyword: Color,
     val string: Color,
     val literal: Color,
@@ -34,6 +38,8 @@ data class SyntaxPalette(
 ) {
     fun of(kind: Kind): Color =
         when (kind) {
+            Kind.ADDITION -> addition
+            Kind.DELETION -> deletion
             Kind.KEYWORD -> keyword
             Kind.STRING -> string
             Kind.LITERAL -> literal
@@ -44,6 +50,26 @@ data class SyntaxPalette(
         }
 }
 
+/** A unified diff is line-oriented: colour the changed lines and leave context untouched. */
+fun scanDiff(code: String): List<Span> {
+    val spans = ArrayList<Span>()
+    var start = 0
+    while (start < code.length) {
+        val end = code.indexOf('\n', start).let { if (it == -1) code.length else it }
+        val kind =
+            when {
+                code.startsWith("+++", start) || code.startsWith("---", start) -> Kind.METADATA
+                code.startsWith("+", start) -> Kind.ADDITION
+                code.startsWith("-", start) -> Kind.DELETION
+                code.startsWith("@@", start) -> Kind.METADATA
+                else -> null
+            }
+        if (kind != null) spans.add(Span(start, end, kind))
+        start = if (end == code.length) end else end + 1
+    }
+    return spans
+}
+
 /**
  * [code] with its keywords, strings and comments coloured, or plain if there is no language for it.
  *