Mihaela Mihaljevic
4fe8771fb9
Add Query.value(at:position:size:variables:) to evaluate an expression against a context node already in a tree, with its proximity position, size, and variable bindings. position(), last(), and the upward axes resolve from that node. This completes full XPath 1.0: the per-node entry point that downstream engines (XSLT, Schematron) drive. Closes #43
71 lines
3.3 KiB
Swift
71 lines
3.3 KiB
Swift
public extension PureXML.XPath {
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/// A compiled XPath 1.0 expression: all thirteen axes with their
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/// abbreviations, the node tests, the operator grammar (`or`, `and`, `=`,
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/// `!=`, `<`, `<=`, `>`, `>=`, `+`, `-`, `*`, `div`, `mod`, unary `-`, `|`),
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/// number and string literals, variable references, function calls, and
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/// filter expressions, all over the four-type model (node-set, boolean,
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/// number, string). Reimplemented from the XPath 1.0 specification.
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struct Query: Sendable {
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let expression: Expression
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/// Compiles an XPath expression, throwing ``QueryError`` on a syntax error.
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public init(_ path: String) throws {
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expression = try Compiler.compile(path)
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}
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/// Evaluates the query over a node, returning the selected node-set in
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/// document order. A non-node-set expression yields an empty list; use
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/// ``value(over:variables:)`` for typed results.
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public func evaluate(over node: PureXML.Model.Node) -> [Selection] {
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Evaluator.evaluate(expression, over: node)
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}
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/// Evaluates the query and returns the selected elements only.
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public func elements(over node: PureXML.Model.Node) -> [PureXML.Model.Element] {
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evaluate(over: node).compactMap(\.element)
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}
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/// Evaluates the query and returns the string-value of each selection.
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public func strings(over node: PureXML.Model.Node) -> [String] {
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evaluate(over: node).map(\.stringValue)
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}
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/// Evaluates the query to a typed ``Value`` with optional variable bindings.
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public func value(
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over node: PureXML.Model.Node,
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variables: [String: Value] = [:],
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) throws -> Value {
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try Evaluator.value(expression, over: node, variables: variables)
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}
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/// Evaluates the query against an explicit context: a node already in a
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/// tree (``PureXML/Model/TreeNode``), its one-based proximity `position`
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/// within a node-set of `size`, and variable bindings. Downstream engines
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/// (XSLT, Schematron) drive this per context node; `position()` and
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/// `last()` reflect the supplied values.
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public func value(
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at node: PureXML.Model.TreeNode,
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position: Int = 1,
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size: Int = 1,
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variables: [String: Value] = [:],
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) throws -> Value {
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try Evaluator.value(expression, at: node, position: position, size: size, variables: variables)
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}
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/// Evaluates the query and coerces the result to a number.
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public func number(over node: PureXML.Model.Node, variables: [String: Value] = [:]) throws -> Double {
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try value(over: node, variables: variables).number
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}
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/// Evaluates the query and coerces the result to a string.
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public func string(over node: PureXML.Model.Node, variables: [String: Value] = [:]) throws -> String {
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try value(over: node, variables: variables).string
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}
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/// Evaluates the query and coerces the result to a boolean.
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public func boolean(over node: PureXML.Model.Node, variables: [String: Value] = [:]) throws -> Bool {
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try value(over: node, variables: variables).boolean
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}
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}
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}
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