Add migrate-posts script

Author: valencik

migrate-posts.scala

@@ -0,0 +1,168 @@
+//> using dep org.virtuslab::scala-yaml::0.3.1
+//> using dep co.fs2::fs2-io::3.12.2
+
+import cats.effect.{IO, IOApp}
+import cats.syntax.all.*
+import fs2.io.file.{Files, Path}
+import org.virtuslab.yaml.*
+
+case class PostMeta(author: Option[String]) derives YamlCodec
+
+case class Conf(title: String, category: Option[String], meta: Option[PostMeta])
+    derives YamlCodec
+
+case class Post(conf: Conf, content: String, originalYaml: String) {
+
+  def cleanPostUrl(markdown: String): String = {
+    // Replace {% post_url YYYY-MM-DD-filename %} with filename.md
+    val postUrlPattern = """\{%\s*post_url\s+\d{4}-\d{2}-\d{2}-(.+?)\s*%\}""".r
+    postUrlPattern.replaceAllIn(markdown, "$1.md")
+  }
+
+  def cleanOtherLinks(markdown: String): String = {
+    var cleaned = markdown
+
+    // Replace absolute typelevel.org blog URLs: https://typelevel.org/blog/YYYY/MM/DD/post-name.html with post-name.md
+    val typelevelBlogPattern =
+      """https://typelevel\.org/blog/\d{4}/\d{2}/\d{2}/([^)\s]+)\.html""".r
+    cleaned = typelevelBlogPattern.replaceAllIn(cleaned, "$1.md")
+
+    // Replace relative blog URLs: /blog/YYYY/MM/DD/post-name.html with post-name.md
+    val relativeBlogPattern =
+      """(?<![a-z])/blog/\d{4}/\d{2}/\d{2}/([^)\s]+)\.html""".r
+    cleaned = relativeBlogPattern.replaceAllIn(cleaned, "$1.md")
+
+    // Replace Jekyll site.url variables: {{ site.url }}/... with /...
+    val siteUrlPattern = """\{\{\s*site\.url\s*\}\}""".r
+    cleaned = siteUrlPattern.replaceAllIn(cleaned, "")
+
+    // Replace .html extensions with .md in relative links (but not absolute URLs starting with http)
+    val htmlToMdPattern = """(?<!https?://[^\s)]*)(\.html)""".r
+    cleaned = htmlToMdPattern.replaceAllIn(cleaned, ".md")
+
+    // Fix links
+    cleaned = cleaned.replace("/conduct.md", "/code-of-conduct/README.md")
+    cleaned = cleaned.replace("/code-of-conduct.md", "/code-of-conduct/README.md")
+    cleaned = cleaned.replace("/projects", "/projects/README.md")
+    cleaned = cleaned.replace("/gsoc/ideas", "/gsoc/ideas.md")
+
+    cleaned
+  }
+
+  def buildHoconMetadata(date: String): String = {
+    val authorLine = conf.meta.flatMap(_.author).map(a => s"  author: $${$a}")
+    val dateLine = Some(s"""  date: "$date"""")
+    val tagsLine = conf.category.map(c => s"  tags: [$c]")
+
+    List(
+      Some("{%"),
+      authorLine,
+      dateLine,
+      tagsLine,
+      Some("%}")
+    ).flatten.mkString("\n")
+  }
+
+  def toLaika(date: String, stage: Int): String = {
+    val metadata = buildHoconMetadata(date)
+    val title = s"# ${conf.title}"
+
+    stage match {
+      case 1 =>
+        // Stage 1: Just move to new location, keep original format
+        s"---\n$originalYaml---\n\n$content\n"
+
+      case 2 =>
+        // Stage 2: HOCON metadata + title, no content changes
+        s"$metadata\n\n$title\n\n$content\n"
+
+      case 3 =>
+        // Stage 3: Stage 2 + post_url substitution
+        val transformedContent = cleanPostUrl(content)
+        s"$metadata\n\n$title\n\n$transformedContent\n"
+
+      case _ =>
+        // Stage 4+: All transformations
+        val transformedContent = cleanOtherLinks(cleanPostUrl(content))
+        s"$metadata\n\n$title\n\n$transformedContent\n"
+    }
+  }
+}
+
+object PostParser {
+  def parse(path: Path, content: String): Either[Throwable, Post] = {
+    // Normalize Windows line endings to Unix
+    val normalized = content.replace("\r\n", "\n")
+    val parts = normalized.split("---\n", 3)
+    if (parts.length < 3) {
+      val fn = path.fileName
+      Left(new Exception(s"Invalid post '$fn': no YAML front matter found"))
+    } else {
+      val yamlContent = parts(1)
+      val markdownContent = parts(2).trim
+      yamlContent.as[Conf].map(conf => Post(conf, markdownContent, yamlContent))
+    }
+  }
+}
+
+object MigratePosts extends IOApp {
+  val oldPostsDir = Path("../typelevel.github.com/collections/_posts")
+  val newBlogDir = Path("src/blog")
+
+  // Manual renaming map for files that would collide after date stripping
+  val renameMap: Map[String, String] = Map(
+    "2023-02-23-gsoc.md" -> "gsoc-2023.md",
+    "2024-03-02-gsoc.md" -> "gsoc-2024.md",
+    "2025-02-27-gsoc.md" -> "gsoc-2025.md",
+  )
+
+  def getDateAndName(path: Path): Either[Throwable, (String, String)] = {
+    val filename = path.fileName.toString
+    val datePattern = """(\d{4}-\d{2}-\d{2})-(.+)""".r
+    filename match {
+      case datePattern(date, rest) =>
+        val newName = renameMap.getOrElse(filename, rest)
+        Right((date, newName))
+      case _ =>
+        Left(new Exception(s"Filename doesn't match pattern: $filename"))
+    }
+  }
+
+  def readPost(path: Path): IO[String] = Files[IO]
+    .readAll(path)
+    .through(fs2.text.utf8.decode)
+    .compile
+    .string
+
+  def writePost(path: Path, content: String): IO[Unit] = fs2.Stream
+    .emit(content)
+    .through(fs2.text.utf8.encode)
+    .through(Files[IO].writeAll(path))
+    .compile
+    .drain
+
+  def migratePost(sourcePath: Path, stage: Int): IO[String] = for {
+    (date, newFilename) <- IO.fromEither(getDateAndName(sourcePath))
+    content <- readPost(sourcePath)
+    post <- IO.fromEither(PostParser.parse(sourcePath, content))
+    laikaContent = post.toLaika(date, stage)
+    destPath = newBlogDir / newFilename
+    _ <- writePost(destPath, laikaContent)
+  } yield newFilename
+
+  def migrateAllPosts(stage: Int): IO[Long] = Files[IO]
+    .list(oldPostsDir)
+    .filter(_.fileName.toString.matches("""^\d{4}-\d{2}-\d{2}-.+\.md$"""))
+    .evalMap(path => migratePost(path, stage))
+    .evalMap(newFilename => IO.println(s"Migrated: $newFilename"))
+    .compile
+    .count
+
+  def run(args: List[String]): IO[cats.effect.ExitCode] = {
+    val stage = args.headOption.flatMap(_.toIntOption).getOrElse(4)
+    IO.println(s"Running migration with stage $stage") *>
+      migrateAllPosts(stage)
+        .flatMap(c => IO.println(s"Migrated $c posts"))
+        .as(cats.effect.ExitCode.Success)
+  }
+}