feat(svg): introduce style tags parsing

This commit introduces the ability to parse CSS code within `<style>` tags in SVG files.

It adds a new `SvgStyleNode` class to represent `<style>` elements and stores the parsed CSS as an Abstract Syntax Tree (AST) for later use.

svg-to-compose/src/commonMain/kotlin/dev/tonholo/s2c/domain/svg/SvgRootNode.kt

@@ -145,6 +145,8 @@ class SvgRootNode(
      */
     val gradients: HashMap<String, SvgGradient<*>> = hashMapOf()
 
+    val styles: MutableList<SvgStyleNode> = mutableListOf()
+
     /**
      * The transform applied to the entire SVG.
      * If the SVG has a viewBox with an offset (x or y not 0), a translation

svg-to-compose/src/commonMain/kotlin/dev/tonholo/s2c/domain/svg/SvgStyleNode.kt

@@ -0,0 +1,41 @@
+package dev.tonholo.s2c.domain.svg
+
+import dev.tonholo.s2c.domain.xml.XmlNode
+import dev.tonholo.s2c.domain.xml.XmlParentNode
+import dev.tonholo.s2c.domain.xml.XmlTextNode
+import dev.tonholo.s2c.extensions.firstInstanceOf
+import dev.tonholo.s2c.lexer.css.CssTokenizer
+import dev.tonholo.s2c.lexer.css.CssTokenKind
+import dev.tonholo.s2c.parser.ast.AstParser
+import dev.tonholo.s2c.parser.ast.css.syntax.node.StyleSheet
+
+class SvgStyleNode(
+    parent: XmlParentNode,
+    override val children: MutableSet<XmlNode>,
+    override val attributes: MutableMap<String, String>,
+) : SvgElementNode<SvgStyleNode>(parent, children, attributes, tagName = TAG_NAME), SvgNode {
+    override val constructor = ::SvgStyleNode
+    override val tagName: String = TAG_NAME
+    val content: String by lazy {
+        children
+            .firstInstanceOf<XmlTextNode>()
+            .content
+    }
+    private var _tree: StyleSheet? = null
+    val tree: StyleSheet
+        get() = checkNotNull(_tree) {
+            "Css tree is not resolved. Did you forget to call `resolveTree()`?"
+        }
+
+    override fun toString(): String = toJsString {
+    }
+
+    internal fun resolveTree(parser: AstParser<CssTokenKind, StyleSheet>) {
+        val tokens = CssTokenizer().tokenize(content).toList()
+        _tree = parser.parse(tokens)
+    }
+
+    companion object {
+        const val TAG_NAME = "style"
+    }
+}

svg-to-compose/src/commonMain/kotlin/dev/tonholo/s2c/domain/xml/XmlNode.kt

@@ -93,6 +93,17 @@ abstract class XmlChildNode(
     }
 }
 
+class XmlTextNode(
+    parent: XmlParentNode,
+    val content: String,
+) : XmlChildNode(parent) {
+    override val tagName: String = parent.tagName
+    override val attributes: MutableMap<String, String> = parent.attributes
+    override fun toString(): String = toJsString {
+        append("\"content\": $content")
+    }
+}
+
 data class XmlRootNode(
     override val tagName: String = "#root",
     override val children: MutableSet<XmlNode>,