douglashill · March 21, 2025 08:09 · mefuzar · Mar 21, 2025 · douglashill · Mar 21, 2025
diff --git a/Markdown.pl.swift b/Markdown.pl.swift
 // Douglas Hill, November 2023
 // This file is made available under the MIT license included at the bottom of this file.

 // `@testable` needed to access `_data`
 @testable import Markdown // This package: https://github.com/apple/swift-markdown

 /// Writes a Markdown document to HTML.
 ///
 /// The primary goal is for output to match the output of Markdown.pl 1.0.1 as closely as possible.
 /// <https://daringfireball.net/projects/markdown/>
 ///
 /// Usage:
 ///
 /// ```swift
 /// let document = Document(parsing: "Convert *Markdown* to **HTML**.", options: [.disableSmartOpts])
 /// var htmlFormatter = HTMLFormatter()
 /// htmlFormatter.visit(document)
 /// print(htmlFormatter.output) // <p>Convert <em>Markdown</em> to <strong>HTML</strong>.</p>
 /// ```
 ///
 /// Swift Markdown makes all quotation marks curly, but they shouldn’t be for foot and inch marks
 /// so parse the document using the `.disableSmartOpts` option.
 /// See <https://practicaltypography.com/foot-and-inch-marks.html>
 ///
 /// Known discrepancies from Markdown.pl:
 ///
 /// - All instances of > will be replaced with &gt instead of only some.
 /// - Nested lists won’t include as many line breaks.
 /// - There won’t be empty lines between multiple paragraphs in a list item.
 struct HTMLFormatter: MarkupVisitor {
    var output = ""

    mutating func defaultVisit(_ markup: Markup) -> Void {
        let tag: String
        var attributes: [(name: String, value: String)] = []
        if markup is Strong {
            tag = "strong"
        } else if markup is Emphasis {
            tag = "em"
        } else if markup is Paragraph {
            tag = "p"
        } else if markup is Document {
            tag = "body"
        } else if markup is BlockQuote {
            tag = "blockquote"
        } else if markup is ListItem {
            tag = "li"
        } else if markup is OrderedList {
            tag = "ol"
        } else if markup is UnorderedList {
            tag = "ul"
        } else if let heading = markup as? Heading {
            precondition((1...6).contains(heading.level))
            tag = "h\(heading.level)"
        } else if let link = markup as? Link {
            if let destination = link.destination {
                attributes.append((name: "href", value: destination))
            }
            tag = "a"
        } else {
            fatalError("Unknown node: \(String(describing: type(of: markup)))")
        }

        let skipTag = markup is Paragraph && markup.parent is ListItem && (markup.parent!.parent! as! ListItemContainer).skipParagraphsInItems

        if !skipTag {
            output += "<\(tag)"
            for attribute in attributes {
                output += " \(attribute.name)=\"\(attribute.value.replacingWithHTMLEntities())\""
            }
            output += ">"

            if markup is ListItemContainer {
                output += "\n"
            }
            if markup is BlockQuote {
                // Indent only the first child of a blockquote to match Markdown.pl.
                output += "\n  "
            }
        }

        for child in markup.children {
            visit(child)
        }

        if markup is BlockQuote && output.last == "\n" {
            output.removeLast()
        }

        if !skipTag {
            output += "</\(tag)>"
            if markup is ListItem {
                output += "\n"
            } else if markup is BlockMarkup && !(markup is Paragraph && markup.parent is ListItem) {
                output += "\n\n"
            }
        }
    }

    mutating func visitDocument(_ document: Document) -> () {
        // Adding a <body> tag is usually not useful.
        for child in document.children {
            visit(child)
        }
    }

    mutating func visitImage(_ image: Image) -> () {
        var altText: String?
        for child in image.children {
            precondition(altText == nil, "Image node has too many children. Should just be one Text node.")
            altText = (child as! Text).string
        }

        output += "<img src=\"\(image.source ?? "")\" alt=\"\(altText ?? "")\" title=\"\(image.title ?? "")\" />"
    }

    mutating func visitInlineCode(_ inlineCode: InlineCode) -> () {
        for _ in inlineCode.children {
            fatalError("Inline code node should not have any children.")
        }

        output += "<code>\(inlineCode.code.replacingWithHTMLEntities())</code>"
    }

    mutating func visitText(_ markup: Text) -> Void {
        for _ in markup.children {
            fatalError("Text node should not have any children.")
        }

        output += markup.string.replacingWithHTMLEntities()
    }

    mutating func visitCodeBlock(_ codeBlock: CodeBlock) -> () {
        output += "<pre><code>\(codeBlock.code.replacingWithHTMLEntities())</code></pre>\n\n"
    }

    mutating func visitHTMLBlock(_ html: HTMLBlock) -> () {
        precondition(html.rawHTML.hasSuffix("\n"))

        // List taken from _HashHTMLBlocks in Markdown.pl
        let blockElements = [
            "p",
            "div",
            "h1",
            "h2",
            "h3",
            "h4",
            "h5",
            "h6",
            "blockquote",
            "pre",
            "table",
            "dl",
            "ol",
            "ul",
            "script",
            "noscript",
            "form",
            "fieldset",
            "iframe",
            "math",
        ]
        for blockElement in blockElements {
            if html.rawHTML.hasPrefix("<\(blockElement)") {
                output += "\(html.rawHTML.replacingOccurrences(of: "\t", with: "    "))\n"
                return
            }
        }

        // Otherwise it’s an inline element, so wrap it in a paragraph.
        var editableHTML = html.rawHTML
        editableHTML.removeLast()
        output += "<p>\(editableHTML.replacingOccurrences(of: "\t", with: "    "))</p>\n\n"
    }

    mutating func visitInlineHTML(_ html: InlineHTML) -> () {
        output += html.rawHTML
    }

    mutating func visitSoftBreak(_ softBreak: SoftBreak) -> () {
        // This seems to come up when there’s no empty line.
        output += "\n"
    }

    mutating func visitLineBreak(_ lineBreak: LineBreak) -> () {
        output += " <br />\n"
    }

    mutating func visitThematicBreak(_ thematicBreak: ThematicBreak) -> () {
        output += "<hr />\n\n"
    }
 }

 private extension String {
    func replacingWithHTMLEntities() -> String {
        self.replacingOccurrences(of: "&", with: "&amp;")
            .replacingOccurrences(of: "<", with: "&lt;")
        // With inputs that look very similar, Markdown.pl will usually replace > with the entity but sometimes won’t.
        // I don’t understand the implementation.
        // Mostly this entity should not be needed, but replace it anyway to be more similar to Markdown.pl.
            .replacingOccurrences(of: ">", with: "&gt;")
        // Like _Detab in Markdown.pl
            .replacingOccurrences(of: "\t", with: "    ")
    }
 }

 private extension ListItemContainer {

    /// Whether to ignore the `Paragraph` children of the `ListItem` children of this list.
    ///
    /// Swift Markdown always puts a `Paragraph` inside a `ListItem` even when there shouldn’t be one. Have to use internals to distinguish this case.
    ///
    /// This is not very robust.
    var skipParagraphsInItems: Bool {
        var lastStartLine: Int?
        var lineDifference: Int?
        // Enumerating all children results in quadratic complexity because this property will be read for each child.
        for child in children {
            let currentStartLine = child._data.range!.lowerBound.line
            if let lastStartLine {
                let currentLineDifference = currentStartLine - lastStartLine
                if let lineDifference {
                    if lineDifference != currentLineDifference {
                        return true
                    }
                } else {
                    lineDifference = currentLineDifference
                }
            }
            lastStartLine = currentStartLine
        }

        guard let lineDifference else {
            // Single item lists. Don’t include paragraph to match Markdown.pl.
            return true
        }

        return lineDifference == 1
    }
 }

 /*
 The MIT License (MIT)

 Copyright 2023 Douglas Hill

 Permission is hereby granted, free of charge, to any person obtaining a copy of
 this software and associated documentation files (the "Software"), to deal in
 the Software without restriction, including without limitation the rights to
 use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 the Software, and to permit persons to whom the Software is furnished to do so,
 subject to the following conditions:

 The above copyright notice and this permission notice shall be included in all
 copies or substantial portions of the Software.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
	// Douglas Hill, November 2023
	// This file is made available under the MIT license included at the bottom of this file.

	// `@testable` needed to access `_data`
	@testable import Markdown // This package: https://github.com/apple/swift-markdown

	/// Writes a Markdown document to HTML.
	///
	/// The primary goal is for output to match the output of Markdown.pl 1.0.1 as closely as possible.
	/// <https://daringfireball.net/projects/markdown/>
	///
	/// Usage:
	///
	/// ```swift
	/// let document = Document(parsing: "Convert Markdown to HTML.", options: [.disableSmartOpts])
	/// var htmlFormatter = HTMLFormatter()
	/// htmlFormatter.visit(document)
	/// print(htmlFormatter.output) // <p>Convert <em>Markdown</em> to <strong>HTML</strong>.</p>
	/// ```
	///
	/// Swift Markdown makes all quotation marks curly, but they shouldn’t be for foot and inch marks
	/// so parse the document using the `.disableSmartOpts` option.
	/// See <https://practicaltypography.com/foot-and-inch-marks.html>
	///
	/// Known discrepancies from Markdown.pl:
	///
	/// - All instances of > will be replaced with &gt instead of only some.
	/// - Nested lists won’t include as many line breaks.
	/// - There won’t be empty lines between multiple paragraphs in a list item.
	struct HTMLFormatter: MarkupVisitor {
	var output = ""

	mutating func defaultVisit(_ markup: Markup) -> Void {
	let tag: String
	var attributes: [(name: String, value: String)] = []
	if markup is Strong {
	tag = "strong"
	} else if markup is Emphasis {
	tag = "em"
	} else if markup is Paragraph {
	tag = "p"
	} else if markup is Document {
	tag = "body"
	} else if markup is BlockQuote {
	tag = "blockquote"
	} else if markup is ListItem {
	tag = "li"
	} else if markup is OrderedList {
	tag = "ol"
	} else if markup is UnorderedList {
	tag = "ul"
	} else if let heading = markup as? Heading {
	precondition((1...6).contains(heading.level))
	tag = "h\(heading.level)"
	} else if let link = markup as? Link {
	if let destination = link.destination {
	attributes.append((name: "href", value: destination))
	}
	tag = "a"
	} else {
	fatalError("Unknown node: \(String(describing: type(of: markup)))")
	}

	let skipTag = markup is Paragraph && markup.parent is ListItem && (markup.parent!.parent! as! ListItemContainer).skipParagraphsInItems

	if !skipTag {
	output += "<\(tag)"
	for attribute in attributes {
	output += " \(attribute.name)=\"\(attribute.value.replacingWithHTMLEntities())\""
	}
	output += ">"

	if markup is ListItemContainer {
	output += "\n"
	}
	if markup is BlockQuote {
	// Indent only the first child of a blockquote to match Markdown.pl.
	output += "\n "
	}
	}

	for child in markup.children {
	visit(child)
	}

	if markup is BlockQuote && output.last == "\n" {
	output.removeLast()
	}

	if !skipTag {
	output += "</\(tag)>"
	if markup is ListItem {
	output += "\n"
	} else if markup is BlockMarkup && !(markup is Paragraph && markup.parent is ListItem) {
	output += "\n\n"
	}
	}
	}

	mutating func visitDocument(_ document: Document) -> () {
	// Adding a <body> tag is usually not useful.
	for child in document.children {
	visit(child)
	}
	}

	mutating func visitImage(_ image: Image) -> () {
	var altText: String?
	for child in image.children {
	precondition(altText == nil, "Image node has too many children. Should just be one Text node.")
	altText = (child as! Text).string
	}

	output += "<img src=\"\(image.source ?? "")\" alt=\"\(altText ?? "")\" title=\"\(image.title ?? "")\" />"
	}

	mutating func visitInlineCode(_ inlineCode: InlineCode) -> () {
	for _ in inlineCode.children {
	fatalError("Inline code node should not have any children.")
	}

	output += "<code>\(inlineCode.code.replacingWithHTMLEntities())</code>"
	}

	mutating func visitText(_ markup: Text) -> Void {
	for _ in markup.children {
	fatalError("Text node should not have any children.")
	}

	output += markup.string.replacingWithHTMLEntities()
	}

	mutating func visitCodeBlock(_ codeBlock: CodeBlock) -> () {
	output += "<pre><code>\(codeBlock.code.replacingWithHTMLEntities())</code></pre>\n\n"
	}

	mutating func visitHTMLBlock(_ html: HTMLBlock) -> () {
	precondition(html.rawHTML.hasSuffix("\n"))

	// List taken from _HashHTMLBlocks in Markdown.pl
	let blockElements = [
	"p",
	"div",
	"h1",
	"h2",
	"h3",
	"h4",
	"h5",
	"h6",
	"blockquote",
	"pre",
	"table",
	"dl",
	"ol",
	"ul",
	"script",
	"noscript",
	"form",
	"fieldset",
	"iframe",
	"math",
	]
	for blockElement in blockElements {
	if html.rawHTML.hasPrefix("<\(blockElement)") {
	output += "\(html.rawHTML.replacingOccurrences(of: "\t", with: " "))\n"
	return
	}
	}

	// Otherwise it’s an inline element, so wrap it in a paragraph.
	var editableHTML = html.rawHTML
	editableHTML.removeLast()
	output += "<p>\(editableHTML.replacingOccurrences(of: "\t", with: " "))</p>\n\n"
	}

	mutating func visitInlineHTML(_ html: InlineHTML) -> () {
	output += html.rawHTML
	}

	mutating func visitSoftBreak(_ softBreak: SoftBreak) -> () {
	// This seems to come up when there’s no empty line.
	output += "\n"
	}

	mutating func visitLineBreak(_ lineBreak: LineBreak) -> () {
	output += " <br />\n"
	}

	mutating func visitThematicBreak(_ thematicBreak: ThematicBreak) -> () {
	output += "<hr />\n\n"
	}
	}

	private extension String {
	func replacingWithHTMLEntities() -> String {
	self.replacingOccurrences(of: "&", with: "&")
	.replacingOccurrences(of: "<", with: "<")
	// With inputs that look very similar, Markdown.pl will usually replace > with the entity but sometimes won’t.
	// I don’t understand the implementation.
	// Mostly this entity should not be needed, but replace it anyway to be more similar to Markdown.pl.
	.replacingOccurrences(of: ">", with: ">")
	// Like _Detab in Markdown.pl
	.replacingOccurrences(of: "\t", with: " ")
	}
	}

	private extension ListItemContainer {

	/// Whether to ignore the `Paragraph` children of the `ListItem` children of this list.
	///
	/// Swift Markdown always puts a `Paragraph` inside a `ListItem` even when there shouldn’t be one. Have to use internals to distinguish this case.
	///
	/// This is not very robust.
	var skipParagraphsInItems: Bool {
	var lastStartLine: Int?
	var lineDifference: Int?
	// Enumerating all children results in quadratic complexity because this property will be read for each child.
	for child in children {
	let currentStartLine = child._data.range!.lowerBound.line
	if let lastStartLine {
	let currentLineDifference = currentStartLine - lastStartLine
	if let lineDifference {
	if lineDifference != currentLineDifference {
	return true
	}
	} else {
	lineDifference = currentLineDifference
	}
	}
	lastStartLine = currentStartLine
	}

	guard let lineDifference else {
	// Single item lists. Don’t include paragraph to match Markdown.pl.
	return true
	}

	return lineDifference == 1
	}
	}

	/*
	The MIT License (MIT)

	Copyright 2023 Douglas Hill

	Permission is hereby granted, free of charge, to any person obtaining a copy of
	this software and associated documentation files (the "Software"), to deal in
	the Software without restriction, including without limitation the rights to
	use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
	the Software, and to permit persons to whom the Software is furnished to do so,
	subject to the following conditions:

	The above copyright notice and this permission notice shall be included in all
	copies or substantial portions of the Software.

	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
	FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
	COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
	IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
	CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
	*/