import Foundation
import libxml2

class InNodeConverter: SafeConverter {
    
    /// Converts a single node (from libxml2) into an HTML.Node.
    ///
    /// - Parameters:
    ///     - attributes: the libxml2 attribute to convert.
    ///
    /// - Returns: an HTML.Node.
    ///
    func convert(_ rawNode: xmlNode) -> Node {
        var node: Node

        switch rawNode.type {
        case XML_TEXT_NODE:
            node = createTextNode(rawNode)
        case XML_CDATA_SECTION_NODE:
            node = createTextNode(rawNode)
        case XML_COMMENT_NODE:
            node = createCommentNode(rawNode)
        default:
            node = createElementNode(rawNode)
        }

        return node
    }

    fileprivate func createAttributes(fromNode rawNode: xmlNode) -> [Attribute] {
        let attributesConverter = InAttributesConverter()
        return attributesConverter.convert(rawNode.properties)
    }

    /// Creates an HTML.Node from a libxml2 element node.
    ///
    /// - Parameters:
    ///     - rawNode: the libxml2 xmlNode.
    ///
    /// - Returns: the HTML.ElementNode
    ///
    fileprivate func createElementNode(_ rawNode: xmlNode) -> ElementNode {

        let nodeName = getNodeName(rawNode)

        switch nodeName.lowercased() {
        case RootNode.name:
            return createRootNode(rawNode)
        default:
            break
        }

        var children = [Node]()

        if rawNode.children != nil {
            let nodesConverter = InNodesConverter()
            children.append(contentsOf: nodesConverter.convert(rawNode.children))
        }

        let attributes = createAttributes(fromNode: rawNode)
        let node = ElementNode(name: nodeName, attributes: attributes, children: children)

        // TODO: This can be optimized to be set during instantiation of the child nodes.
        //
        for child in children {
            child.parent = node
        }

        return node
    }

    /// Creates an HTML.RootNode from a libxml2 element root node.
    ///
    /// - Parameters:
    ///     - rawNode: the libxml2 xmlNode.
    ///
    /// - Returns: the HTML.RootNode
    ///
    fileprivate func createRootNode(_ rawNode: xmlNode) -> RootNode {
        var children = [Node]()

        if rawNode.children != nil {
            let nodesConverter = InNodesConverter()
            children.append(contentsOf: nodesConverter.convert(rawNode.children))
        }

        let node = RootNode(children: children)

        // TODO: This can be optimized to be set during instantiation of the child nodes.
        //
        for child in children {
            child.parent = node
        }
        
        return node
    }

    /// Creates an HTML.TextNode from a libxml2 element node.
    ///
    /// - Parameters:
    ///     - rawNode: the libxml2 xmlNode.
    ///
    /// - Returns: the HTML.TextNode
    ///
    fileprivate func createTextNode(_ rawNode: xmlNode) -> TextNode {
        let text = String(cString: rawNode.content)
        let node = TextNode(text: text)

        return node
    }

    /// Creates an HTML.CommentNode from a libxml2 element node.
    ///
    /// - Parameters:
    ///     - rawNode: the libxml2 xmlNode.
    ///
    /// - Returns: the HTML.CommentNode
    ///
    fileprivate func createCommentNode(_ rawNode: xmlNode) -> CommentNode {
        let text = String(cString: rawNode.content)
        let node = CommentNode(text: text)

        return node
    }

    fileprivate func getNodeName(_ rawNode: xmlNode) -> String {
        return String(cString: rawNode.name)
    }
}