111 lines
4.2 KiB
Swift
111 lines
4.2 KiB
Swift
//
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// GeminiParser.swift
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// GeminiFormat
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//
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// Created by Shadowfacts on 7/12/20.
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//
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import Foundation
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struct GeminiParser {
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private init() {}
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static func parse(text: String, baseURL: URL) -> Document {
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var doc = Document(url: baseURL)
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var preformattingState = PreformattingState.off
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text.enumerateLines { (line, stop) in
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if line.starts(with: "```") {
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switch preformattingState {
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case .off:
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let alt: String?
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if line.count > 3 {
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alt = String(line[line.index(line.startIndex, offsetBy: 3)...])
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} else {
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alt = nil
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}
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preformattingState = .on(alt)
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case .on(_):
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preformattingState = .off
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}
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if case .off = preformattingState {
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}
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} else if case let .on(alt) = preformattingState {
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doc.lines.append(.preformattedText(line, alt: alt))
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} else if line.starts(with: "=>") {
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// Link line
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let urlStart = line.firstNonWhitespaceIndex(after: line.index(line.startIndex, offsetBy: 2))
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let urlEnd = line.firstWhitespaceIndex(after: urlStart)
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let textStart = line.firstNonWhitespaceIndex(after: urlEnd)
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let urlString = String(line[urlStart..<urlEnd])
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// todo: if the URL initializer fails, should there be a .link line with a nil URL?
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let url = URL(string: urlString, relativeTo: baseURL)!.absoluteURL
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let text: String?
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if textStart < line.endIndex {
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text = String(line[textStart..<line.endIndex])
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} else {
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text = nil
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}
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doc.lines.append(.link(url, text: text))
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} else if line.starts(with: "#") {
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let level: Document.HeadingLevel
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if line.starts(with: "###") {
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level = .h3
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} else if line.starts(with: "##") {
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level = .h2
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} else {
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level = .h1
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}
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let headingStart = line.firstNonWhitespaceIndex(after: line.index(line.startIndex, offsetBy: level.rawValue))
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let headingText = String(line[headingStart...])
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doc.lines.append(.heading(headingText, level: level))
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} else if line.starts(with: "* ") {
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let listItemStart = line.firstNonWhitespaceIndex(after: line.index(line.startIndex, offsetBy: 2))
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let listItemText = String(line[listItemStart...])
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doc.lines.append(.unorderedListItem(listItemText))
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} else if line.starts(with: ">") {
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let quoteStartIndex = line.firstNonWhitespaceIndex(after: line.index(after: line.startIndex))
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let quoteText = String(line[quoteStartIndex...])
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doc.lines.append(.quote(quoteText))
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} else {
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doc.lines.append(.text(line))
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}
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}
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return doc
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}
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}
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fileprivate extension GeminiParser {
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enum PreformattingState {
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case off
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case on(_ alt: String?)
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}
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}
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fileprivate extension String {
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func firstNonWhitespaceIndex(after index: String.Index) -> String.Index {
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var index = index
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// using .unicodeScalars.first should be fine, since all whitespace characters are single scalars
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while index < self.endIndex, CharacterSet.whitespaces.contains(self[index].unicodeScalars.first!) {
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index = self.index(after: index)
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}
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return index
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}
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func firstWhitespaceIndex(after index: String.Index) -> String.Index {
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var index = index
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// todo: could the first unicode scalar of a character be whitespace even though the whole character is not?
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while index < self.endIndex, !CharacterSet.whitespaces.contains(self[index].unicodeScalars.first!) {
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index = self.index(after: index)
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}
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return index
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}
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}
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