From ce39624a39c93ade383e294f1458e56727df50f4 Mon Sep 17 00:00:00 2001
From: Brent Simmons <brent@ranchero.com>
Date: Sat, 21 Sep 2024 11:47:07 -0700
Subject: [PATCH] Create first draft of SAXHTMLParser.

---
 .../Parser/Sources/SAX/SAXHTMLParser.swift    | 255 ++++++++++++++----
 1 file changed, 204 insertions(+), 51 deletions(-)

diff --git a/Modules/Parser/Sources/SAX/SAXHTMLParser.swift b/Modules/Parser/Sources/SAX/SAXHTMLParser.swift
index 43ba1cc38..2f860e297 100644
--- a/Modules/Parser/Sources/SAX/SAXHTMLParser.swift
+++ b/Modules/Parser/Sources/SAX/SAXHTMLParser.swift
@@ -1,54 +1,207 @@
-////
-////  SAXHTMLParser.swift
-////  
-////
-////  Created by Brent Simmons on 8/26/24.
-////
 //
-//import Foundation
-//import libxml2
+//  SAXHTMLParser.swift
+//  
 //
-//protocol SAXHTMLParserDelegate: AnyObject {
+//  Created by Brent Simmons on 8/26/24.
 //
-//	func saxParser(_: SAXHTMLParser, XMLStartElement localName: XMLPointer, attributes: UnsafePointer<XMLPointer?>?)
-//
-//	func saxParser(_: SAXHTMLParser, XMLEndElement localName: XMLPointer?)
-//
-//	// Length is guaranteed to be greater than 0.
-//	func saxParser(_: SAXHTMLParser, XMLCharactersFound characters: XMLPointer?, length: Int)
-//}
-//
-//final class SAXHTMLParser {
-//
-//	fileprivate let delegate: SAXHTMLParserDelegate
-//	private var data: Data
-//
-//	init(delegate: SAXHTMLParserDelegate, data: Data) {
-//
-//		self.delegate = delegate
-//		self.data = data
-//	}
-//
-//	func parse() {
-//
-//		guard !data.isEmpty else {
-//			return
-//		}
-//
-//		data.withUnsafeBytes { bufferPointer in
-//
-//			guard let bytes = bufferPointer.bindMemory(to: xmlChar.self).baseAddress else {
-//				return
-//			}
-//
-//			let characterEncoding = xmlDetectCharEncoding(bytes, Int32(data.count))
-//			let context = htmlCreatePushParserCtxt(&saxHandlerStruct, Unmanaged.passUnretained(self).toOpaque(), nil, 0, nil, characterEncoding)
-//			htmlCtxtUseOptions(context, Int32(XML_PARSE_RECOVER | XML_PARSE_NONET | HTML_PARSE_COMPACT))
-//
-//			htmlParseChunk(context, bytes, Int32(data.count), 0)
-//
-//			htmlParseChunk(context, nil, 0, 1)
-//			htmlFreeParserCtxt(context)
-//		}
-//	}
-//}
+
+import Foundation
+import libxml2
+
+protocol SAXHTMLParserDelegate: AnyObject {
+
+	func saxHTMLParser(_: SAXHTMLParser, startElement name: XMLPointer, attributes: UnsafePointer<XMLPointer?>?)
+
+	func saxHTMLParser(_: SAXHTMLParser, endElement name: XMLPointer?)
+
+	// Length is guaranteed to be greater than 0.
+	func saxHTMLParser(_: SAXHTMLParser, charactersFound characters: XMLPointer?, count: Int)
+}
+
+final class SAXHTMLParser {
+
+	fileprivate let delegate: SAXHTMLParserDelegate
+
+	public var currentCharacters: Data? { // UTF-8 encoded
+
+		guard storingCharacters else {
+			return nil
+		}
+		return characters
+	}
+
+	// Conveniences to get string version of currentCharacters
+
+	public var currentString: String? {
+
+		guard let d = currentCharacters, !d.isEmpty else {
+			return nil
+		}
+		return String(data: d, encoding: .utf8)
+	}
+
+	public var currentStringWithTrimmedWhitespace: String? {
+
+		guard let s = currentString else {
+			return nil
+		}
+		return s.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines)
+	}
+
+	private var data: Data
+	private var storingCharacters = false
+	private var characters = Data()
+
+	public init(delegate: SAXHTMLParserDelegate, data: Data) {
+
+		self.delegate = delegate
+		self.data = data
+	}
+
+	public func parse() {
+
+		guard !data.isEmpty else {
+			return
+		}
+
+		data.withUnsafeBytes { bufferPointer in
+
+			guard let bytes = bufferPointer.bindMemory(to: xmlChar.self).baseAddress else {
+				return
+			}
+
+			let characterEncoding = xmlDetectCharEncoding(bytes, Int32(data.count))
+			let context = htmlCreatePushParserCtxt(&saxHandlerStruct, Unmanaged.passUnretained(self).toOpaque(), nil, 0, nil, characterEncoding)
+			htmlCtxtUseOptions(context, Int32(XML_PARSE_RECOVER | XML_PARSE_NONET | HTML_PARSE_COMPACT))
+
+			htmlParseChunk(context, bytes, Int32(data.count), 0)
+
+			htmlParseChunk(context, nil, 0, 1)
+			htmlFreeParserCtxt(context)
+		}
+	}
+
+	/// Delegate can call from xmlStartElement. Characters will be available in xmlEndElement as currentCharacters property. Storing characters is stopped after each xmlEndElement.
+	public func beginStoringCharacters() {
+
+		storingCharacters = true
+		characters.count = 0
+	}
+
+	public func endStoringCharacters() {
+
+		storingCharacters = false
+		characters.count = 0
+	}
+
+	public typealias HTMLAttributesDictionary = [String: String]
+
+	public func attributesDictionary(_ attributes: UnsafePointer<XMLPointer?>?) -> HTMLAttributesDictionary? {
+
+		guard let attributes else {
+			return nil
+		}
+
+		var dictionary = [String: String]()
+		var ix = 0
+		var currentKey: String? = nil
+
+		while true {
+			let oneAttribute = attributes[ix]
+			ix += 1
+
+			if currentKey == nil && oneAttribute == nil {
+				break
+			}
+
+			if currentKey == nil {
+				if let oneAttribute {
+					currentKey = String(cString: oneAttribute)
+				}
+			} else {
+				let value: String?
+				if let oneAttribute {
+					value = String(cString: oneAttribute)
+				} else {
+					value = nil
+				}
+
+				dictionary[currentKey!] = value ?? ""
+				currentKey = nil
+			}
+		}
+
+		return dictionary
+	}
+}
+
+private extension SAXHTMLParser {
+
+	func charactersFound(_ xmlCharacters: XMLPointer, count: Int) {
+
+		if storingCharacters {
+			characters.append(xmlCharacters, count: count)
+		}
+
+		delegate.saxHTMLParser(self, charactersFound: characters, count: count)
+	}
+
+	func startElement(_ name: XMLPointer, attributes: UnsafePointer<XMLPointer?>?) {
+
+		delegate.saxHTMLParser(self, startElement: name, attributes: attributes)
+	}
+
+	func endElement(_ name: XMLPointer) {
+
+		delegate.saxHTMLParser(self, endElement: name)
+		endStoringCharacters()
+	}
+}
+
+private func startElement(_ context: UnsafeMutableRawPointer?, name: XMLPointer?, attributes: UnsafeMutablePointer<XMLPointer?>?) {
+
+	guard let context, let name else {
+		return
+	}
+
+	let parser = parser(from: context)
+	parser.startElement(name, attributes: attributes)
+}
+
+
+private func endElement(_ context: UnsafeMutableRawPointer?, name: XMLPointer?) {
+
+	guard let context, let name else {
+		return
+	}
+
+	let parser = parser(from: context)
+	parser.endElement(name)
+}
+
+private func charactersFound(_ context: UnsafeMutableRawPointer?, ch: XMLPointer?, len: CInt) {
+
+	guard let context, let ch, len > 0 else {
+		return
+	}
+
+	let parser = parser(from: context)
+	parser.charactersFound(ch, count: Int(len))
+}
+
+private func parser(from context: UnsafeMutableRawPointer) -> SAXParser {
+
+	Unmanaged<SAXHTMLParser>.fromOpaque(context).takeUnretainedValue()
+}
+
+nonisolated(unsafe) private var saxHandlerStruct: xmlSAXHandler = {
+
+	var handler = xmlSAXHandler()
+
+	handler.characters = charactersFound
+	handler.startElement = startElement
+	handler.endElement = endElement
+	handler.initialized = XML_SAX2_MAGIC
+
+	return handler
+}()