Mihaela Mihaljevic
1ae6680d94
Add PureXML.XPath: a compiled location-path query engine reimplemented from the XPath 1.0 specification; no upstream code copied. - Compiler parses a path into steps; Evaluator walks the tree returning a Selection node-set (node or attribute) in document order. - Forward axes only (child, descendant //, self ., attribute @), since the value model has no parent pointers. Node tests: name, *, text(), node(), comment(). Predicates: [n], [@a], [@a='v'], [child], [child='v']. - Public surface: XPath.Query (init compiles, evaluate/elements/strings), the Selection enum (element / stringValue), QueryError, and the one-shot PureXML.xpath(_:over:). Upward/sibling axes and the full expression language are explicitly out of scope. - 12 XPath tests; 61 total.
42 lines
1.5 KiB
Swift
42 lines
1.5 KiB
Swift
public extension PureXML.XPath {
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/// A node selected by an XPath query: either a tree node or an attribute
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/// (attributes are not ``PureXML/Model/Node`` values, so they are surfaced
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/// here alongside nodes).
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enum Selection: Equatable, Sendable {
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case node(PureXML.Model.Node)
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case attribute(PureXML.Model.Attribute)
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/// The selected element, when this selection is an element node.
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public var element: PureXML.Model.Element? {
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guard case let .node(node) = self, case let .element(element) = node else {
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return nil
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}
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return element
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}
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/// The XPath string-value: an attribute's value, or the concatenation of
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/// all descendant character data for a node.
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public var stringValue: String {
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switch self {
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case let .attribute(attribute):
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attribute.value
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case let .node(node):
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Self.stringValue(of: node)
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}
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}
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private static func stringValue(of node: PureXML.Model.Node) -> String {
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switch node {
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case let .text(value), let .cdata(value), let .comment(value):
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value
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case let .processingInstruction(_, data):
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data
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case let .element(element):
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element.children.reduce(into: "") { $0 += stringValue(of: $1) }
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case let .document(children):
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children.reduce(into: "") { $0 += stringValue(of: $1) }
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}
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}
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}
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}
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