package xpath

import (
	"errors"
	"fmt"

	"github.com/antchfx/xmlquery"
)

// Get retrieves nodes from XML data using an XPath expression
func Get(node *xmlquery.Node, path string) ([]*xmlquery.Node, error) {
	if node == nil {
		return nil, errors.New("nil node provided")
	}

	// Execute xpath query directly
	nodes, err := xmlquery.QueryAll(node, path)
	if err != nil {
		return nil, fmt.Errorf("failed to execute XPath query: %v", err)
	}

	return nodes, nil
}

// Set updates a single node in the XML data using an XPath expression
func Set(node *xmlquery.Node, path string, value interface{}) error {
	if node == nil {
		return errors.New("nil node provided")
	}

	// Find the node to update
	nodes, err := xmlquery.QueryAll(node, path)
	if err != nil {
		return fmt.Errorf("failed to execute XPath query: %v", err)
	}

	if len(nodes) == 0 {
		return fmt.Errorf("no nodes found for path: %s", path)
	}

	// Update the first matching node
	updateNodeValue(nodes[0], value)

	return nil
}

// SetAll updates all nodes that match the XPath expression
func SetAll(node *xmlquery.Node, path string, value interface{}) error {
	if node == nil {
		return errors.New("nil node provided")
	}

	// Find all nodes to update
	nodes, err := xmlquery.QueryAll(node, path)
	if err != nil {
		return fmt.Errorf("failed to execute XPath query: %v", err)
	}

	if len(nodes) == 0 {
		return fmt.Errorf("no nodes found for path: %s", path)
	}

	// Update all matching nodes
	for _, matchNode := range nodes {
		updateNodeValue(matchNode, value)
	}

	return nil
}

// Helper function to update a node's value
func updateNodeValue(node *xmlquery.Node, value interface{}) {
	strValue := fmt.Sprintf("%v", value)

	// Handle different node types
	switch node.Type {
	case xmlquery.AttributeNode:
		// For attribute nodes, update the attribute value
		parent := node.Parent
		if parent != nil {
			for i, attr := range parent.Attr {
				if attr.Name.Local == node.Data {
					parent.Attr[i].Value = strValue
					break
				}
			}
		}
	case xmlquery.TextNode:
		// For text nodes, update the text content
		node.Data = strValue
	case xmlquery.ElementNode:
		// For element nodes, clear existing text children and add a new text node
		// First, remove all existing text children
		var nonTextChildren []*xmlquery.Node
		for child := node.FirstChild; child != nil; child = child.NextSibling {
			if child.Type != xmlquery.TextNode {
				nonTextChildren = append(nonTextChildren, child)
			}
		}

		// Clear all children
		node.FirstChild = nil
		node.LastChild = nil

		// Add a new text node
		textNode := &xmlquery.Node{
			Type:   xmlquery.TextNode,
			Data:   strValue,
			Parent: node,
		}

		// Set the text node as the first child
		node.FirstChild = textNode
		node.LastChild = textNode

		// Add back non-text children
		for _, child := range nonTextChildren {
			child.Parent = node

			// If this is the first child being added back
			if node.FirstChild == textNode && node.LastChild == textNode {
				node.FirstChild.NextSibling = child
				child.PrevSibling = node.FirstChild
				node.LastChild = child
			} else {
				// Add to the end of the chain
				node.LastChild.NextSibling = child
				child.PrevSibling = node.LastChild
				node.LastChild = child
			}
		}
	}
}