package xpath

import "errors"

// XPathStep represents a single step in an XPath expression
type XPathStep struct {
	Type      StepType
	Name      string
	Predicate *Predicate
}

// StepType defines the type of XPath step
type StepType int

const (
	// RootStep represents the root step (/)
	RootStep StepType = iota
	// ChildStep represents a child element step (element)
	ChildStep
	// RecursiveDescentStep represents a recursive descent step (//)
	RecursiveDescentStep
	// WildcardStep represents a wildcard step (*)
	WildcardStep
	// PredicateStep represents a predicate condition step ([...])
	PredicateStep
)

// PredicateType defines the type of XPath predicate
type PredicateType int

const (
	// IndexPredicate represents an index predicate [n]
	IndexPredicate PredicateType = iota
	// LastPredicate represents a last() function predicate
	LastPredicate
	// LastMinusPredicate represents a last()-n predicate
	LastMinusPredicate
	// PositionPredicate represents position()-based predicates
	PositionPredicate
	// AttributeExistsPredicate represents [@attr] predicate
	AttributeExistsPredicate
	// AttributeEqualsPredicate represents [@attr='value'] predicate
	AttributeEqualsPredicate
	// ComparisonPredicate represents element comparison predicates
	ComparisonPredicate
)

// Predicate represents a condition in XPath
type Predicate struct {
	Type       PredicateType
	Index      int
	Offset     int
	Attribute  string
	Value      string
	Expression string
}

// XMLNode represents a node in the result set with its value and path
type XMLNode struct {
	Value interface{}
	Path  string
}

// ParseXPath parses an XPath expression into a series of steps
func ParseXPath(path string) ([]XPathStep, error) {
	if path == "" {
		return nil, errors.New("empty path")
	}

	// This is just a placeholder implementation for the tests
	// The actual implementation would parse the XPath expression
	return nil, errors.New("not implemented")
}

// Get retrieves nodes from XML data using an XPath expression
func Get(data interface{}, path string) ([]XMLNode, error) {
	if data == "" {
		return nil, errors.New("empty XML data")
	}

	// This is just a placeholder implementation for the tests
	// The actual implementation would evaluate the XPath against the XML
	return nil, errors.New("not implemented")
}

// Set updates a node in the XML data using an XPath expression
func Set(xmlData string, path string, value interface{}) (string, error) {
	// This is just a placeholder implementation for the tests
	// The actual implementation would modify the XML based on the XPath
	return "", errors.New("not implemented")
}

// SetAll updates all nodes matching an XPath expression in the XML data
func SetAll(xmlData string, path string, value interface{}) (string, error) {
	// This is just a placeholder implementation for the tests
	// The actual implementation would modify all matching nodes
	return "", errors.New("not implemented")
}