import "package:xml/xml.dart";

class XMLNode {
  final String tag;
  Map<String, dynamic> attributes;
  List<XMLNode> children;
  bool closeTag;
  String? text;
  bool isDeclaration;

  XMLNode({ required this.tag, this.attributes = const {}, this.children = const [], this.closeTag = true, this.text, this.isDeclaration = false });
  XMLNode.xmlns({ required this.tag, required String xmlns, Map<String, String> attributes = const {}, this.children = const [], this.closeTag = true, this.text }) : attributes = { "xmlns": xmlns, ...attributes }, isDeclaration = false;

  /// Adds a child to this node.
  void addChild(XMLNode child) {
    children.add(child);
  }

  /// Renders the attributes of the node into "attr1=\"value\" attr2=...".
  String renderAttributes() {
    return attributes.keys.map((key) {
        final value = attributes[key]!;
        assert(value is String || value is int);
        if (value is String) {
          return "$key='$value'";
        } else {
          return "$key=${value.toString()}";
        }
    }).join(" ");
  }

  /// Renders the entire node, including its children, into an XML string.
  String toXml() {
    final decl = isDeclaration ? "?" : "";
    if (children.isEmpty) {
      if (text != null && text!.isNotEmpty) {
        final attrString = attributes.isEmpty ? "" : " " + renderAttributes();
        return "<$tag$attrString>$text</$tag>";
      } else {
        return "<$decl$tag ${renderAttributes()}" + (closeTag ? " />" : "$decl>");
      } 
    } else { 
      final String childXml = children.map((child) => child.toXml()).join();
      final xml = "<$decl$tag ${renderAttributes()}$decl>$childXml";
      return xml + (closeTag ? "</$tag>" : "");
    }
  }

  /// Returns the first child for which [test] returns true. If none is found, returns
  /// null.
  XMLNode? _firstTag(bool Function(XMLNode) test) {
    try {
      return children.firstWhere(test);
    } catch(e) {
      return null;
    }
  }
  
  /// Returns the first xml node that matches the description:
  /// - node's tag is equal to [tag]
  /// - (optional) node's xmlns attribute is equal to [xmlns]
  /// Returns null if none is found.
  XMLNode? firstTag(String tag, { String? xmlns}) {
    return _firstTag((node) {
        if (xmlns != null) {
          return node.tag == tag && node.attributes["xmlns"] == xmlns;
        }

        return node.tag == tag;
    });
  }

  /// Returns the first child whose xmlns attribute is equal to [xmlns]. Returns null
  /// if none is found.
  XMLNode? firstTagByXmlns(String xmlns) {
    return _firstTag((node) {
        return node.attributes["xmlns"] == xmlns;
    });
  }
  
  /// Returns all children whose tag is equal to [tag].
  List<XMLNode> findTags(String tag) {
    return children.where((element) => element.tag == tag).toList();
  }
  
  /// Returns the inner text of the node. If none is set, returns the "".
  String innerText() {
    return text ?? "";
  }

  /// Just for testing purposes
  static XMLNode fromString(String str) {
    return XMLNode.fromXmlElement(
      XmlDocument.parse(str).firstElementChild!
    );
  }

  /// Because this API is better ;)
  /// Don't use in production. Just for testing
  static XMLNode fromXmlElement(XmlElement element) {
    Map<String, String> attributes = {};

    for (var attribute in element.attributes) {
      attributes[attribute.name.qualified] = attribute.value;
    }

    if (element.childElements.isEmpty) {
      return XMLNode(
        tag: element.name.qualified,
        attributes: attributes,
        text: element.innerText
      );
    } else {
      return XMLNode(
        tag: element.name.qualified,
        attributes: attributes,
        children: element.childElements.toList().map((e) => XMLNode.fromXmlElement(e)).toList()
      );
    }
  }
}