markdown-parsing/Sources/main.swift

import Foundation
@preconcurrency import Parsing

let yamlString = """
---
author: Michael Housh
categories:
  - HVAC
  - General
  - Programming
copy: true
draft: false
date: 2023-10-21
lastmod: 2023-10-21
image: banner.png
featuredImage: banner.png
series:
  - General
tags:
  - HVAC
  - General
  - Programming

---
"""

_ = """
title: "You Should Learn Markdown"
slug: "you-should-learn-markdown"
"""

enum YamlItem {
  case boolean(Bool)
  case date(year: Int, month: Int, day: Int)
  case string(String)

  private static let dateParser = Parse(input: Substring.self) {
    Digits(4)
    "-"
    Digits(2)
    "-"
    Digits(2)
  }.map { Self.date(year: $0.0, month: $0.1, day: $0.2) }

  private static let booleanParser = Parse(input: Substring.self) {
    Bool.parser()
  }.map { Self.boolean($0) }

  private static let quotedString = Parse(input: Substring.self) {
    "\""
    PrefixUpTo("\"")
    "\""
  }

  private static let stringParser = Parse(input: Substring.self) {
    OneOf {
      quotedString
      Rest()
    }
  }.map { Self.string(String($0)) }

  static let parser = OneOf {
    dateParser
    booleanParser
    stringParser
  }
}

enum YamlLine {
  case keyValue(String, YamlItem)
  case list(String, [String])

  static let parser = OneOf {
    listParser
    keyValueParser
  }

  static let keyParser = Parse(input: Substring.self) {
    PrefixUpTo(":")
    ":"
  }.map(String.init)

  static let keyValueParser = Parse(input: Substring.self) {
    PrefixUpTo(":").map(String.init)
    ": "
    YamlItem.parser
  }.map { YamlLine.keyValue($0.0, $0.1) }

  static let listLineParser = Parse(input: Substring.self) {
    Skip { PrefixThrough("- ") }
    PrefixUpTo("\n").map(String.init)
    "\n"
  }

  static let listParser = Parse(input: Substring.self) {
    PrefixUpTo(":\n").map(String.init)
    ":\n"
    Many {
      Skip { PrefixThrough("- ") }
      PrefixUpTo("\n").map(String.init)
      "\n"
    }
  }
  .map { YamlLine.list($0.0, $0.1) }
}

let yamlBlockParser = Parse(input: Substring.UTF8View.self) {
  "---\n".utf8
  Many {
    PrefixUpTo("\n".utf8)
    // From(.substring) { YamlLine.parser }
  } separator: {
    "\n".utf8
  }
  "\n".utf8
  "---".utf8
}

// let yamlLineParser = Parse(input: Substring.UTF8View.self) {
//   PrefixUpTo(":".utf8).map(String.init)
//   ":".utf8
//   OneOf {
//     PrefixUpTo("\n".utf8)
//     Rest()
//   }.map(String.init)
// }

let stringLine = #"author: "Michael Housh""#
// let parsedLine = try yamlLineParser.parse(stringLine[...].utf8)
// print(parsedLine)

let stringItem = "foo"
let quotedItem = "\"foo\""
let dateItem = "2025-01-29"
let boolItem = "true"

try print(YamlItem.parser.parse(stringItem[...]))
try print(YamlItem.parser.parse(quotedItem[...]))
try print(YamlItem.parser.parse(dateItem[...]))
try print(YamlItem.parser.parse(boolItem[...]))

let kvLine = "author: Michael Housh"
var listLine = """
test:
  - HVAC
  - General
  - Programming

"""[...]

try print(YamlLine.parser.parse(kvLine[...]))
try print(YamlLine.parser.parse(&listLine))
print(listLine)

// try print(YamlItem.parser.parse(listItem[...]))

var yamlLines = """
author: Michael Housh
test:
  - HVAC
  - General
  - Programming

"""[...]

let lineParser = Many {
  YamlLine.parser
} separator: {
  "\n"
}

try print(lineParser.parse(yamlLines))

// let lines = try yamlBlockParser.parse(yamlString[...].utf8)
//
// for line in lines {
//   print("line: \(String(line)!)")
//   if let parsed = try? YamlLine.keyValueParser.parse(Substring(line)) {
//     print(parsed)
//   } else {
//     if let key = try? YamlLine.keyParser.parse(Substring(line)) {
//       print("found key: \(String(key))")
//     } else {
//       print("not key value.")
//     }
//   }
// }

// print(lines.map(String.init))
// print(lines)