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<h1 id="assembling-pages">Assembling pages</h1>
<p>This is the thirteenth post in the <a
href="https://rsdoiel.github.io/blog/2020/04/11/Mostly-Oberon.html">Mostly
Oberon</a> series. Mostly Oberon documents my exploration of the Oberon
Language, Oberon System and the various rabbit holes I will inevitably
fall into.</p>
<h2 id="pandoc-and-json">Pandoc and JSON</h2>
<p>I use <a href="https://pandoc.org">Pandoc</a> to process Markdown
documents. I like to keep my front matter in JSON rather than Pandoc’s
YAML. Fortunately Pandoc does support working with JSON as a metadata
file include. Normally I would manually split the JSON front matter and
the rest of the markup into two separate files, then process with Pandoc
and other tooling like <a href="https://lunrjs.com">LunrJS</a>. <a
href="AssemblePage.Mod">AssemblePage</a> automates this process.</p>
<p>Example shell usage:</p>
<pre><code>
   AssemblePage MyText.txt \
      metadata=document.json \
      document=document.md
   pandoc --from markdown --to html \
      --metadata-file document.json \
      --standalone \
      document.md &gt;MyText.html
</code></pre>
<h2 id="source-code-for-assemblepage.mod">Source code for
<strong>AssemblePage.Mod</strong></h2>
<pre><code>
MODULE AssemblePage;
  IMPORT Out, Strings, Files, Args := extArgs;

VAR
  srcName, metaName, docName : ARRAY 1024 OF CHAR;

(* FrontMatter takes a &quot;read&quot; Rider, r, and a &quot;write&quot; Rider &quot;w&quot;.
If the first character read by r is an opening curly bracket
(the start of the front matter) it writes it out with w, until
it finds a matching closing curly bracket or the file ends. *)
PROCEDURE FrontMatter*(VAR r : Files.Rider; VAR w : Files.Rider);
  VAR c : BYTE; cCnt : INTEGER;
BEGIN
  (* Scan for opening JSON front matter *)
  cCnt := 0;
  REPEAT
    Files.Read(r, c);
    IF r.eof = FALSE THEN
      IF c = ORD(&quot;{&quot;) THEN
        cCnt := cCnt + 1;
      ELSIF c = ORD(&quot;}&quot;) THEN
        cCnt := cCnt - 1;
      END;
      Files.Write(w, c);
    END;
  UNTIL (r.eof = TRUE) OR (cCnt = 0);
  IF cCnt # 0 THEN
    Out.String(&quot;ERROR: mis matched &#39;{&#39; and &#39;}&#39; in front matter&quot;);
    ASSERT(FALSE);
  END;
END FrontMatter;

(* CopyIO copies the characters from a &quot;read&quot; Rider to a &quot;write&quot; Rider *)
PROCEDURE CopyIO*(VAR r : Files.Rider; VAR w: Files.Rider);
  VAR c : BYTE;
BEGIN
  REPEAT
    Files.Read(r, c);
    IF r.eof = FALSE THEN
      Files.Write(w, c);
    END;
  UNTIL r.eof = TRUE;
END CopyIO;

PROCEDURE ProcessParameters(VAR sName, mName, dName : ARRAY OF CHAR);
  VAR
    arg : ARRAY 1024 OF CHAR;
    i, res : INTEGER;
BEGIN
  mName := &quot;document.json&quot;;
  dName := &quot;document.txt&quot;;
  arg := &quot;&quot;;
  FOR i := 0 TO (Args.count - 1) DO
    Args.Get(i, arg, res);
    IF Strings.Pos(&quot;metadata=&quot;, arg, 0) = 0 THEN
      Strings.Extract(arg, 9, Strings.Length(arg), mName);
    ELSIF Strings.Pos(&quot;document=&quot;, arg, 0) = 0 THEN
      Strings.Extract(arg, 9, Strings.Length(arg), dName);
    ELSE
      Strings.Extract(arg, 0, Strings.Length(arg), sName);
    END;
  END;
END ProcessParameters;

PROCEDURE AssemblePage(srcName, metaName, docName : ARRAY OF CHAR);
VAR
  src, meta, doc : Files.File;
  reader, writer : Files.Rider;
BEGIN
  src := Files.Old(srcName);
  IF src # NIL THEN
    Files.Set(reader, src, 0);
    IF metaName # &quot;&quot; THEN
      meta := Files.New(metaName);
      Files.Register(meta);
      Files.Set(writer, meta, 0);
      FrontMatter(reader, writer);
      Files.Close(meta);
    END;
    IF docName # &quot;&quot; THEN
      doc := Files.New(docName);
      Files.Register(doc);
      Files.Set(writer, doc, 0);
      CopyIO(reader, writer);
      Files.Close(doc);
    END;
  ELSE
    Out.String(&quot;ERROR: Could not read &quot;);Out.String(srcName);Out.Ln();
    ASSERT(FALSE);
  END;
  Files.Close(src);
END AssemblePage;

BEGIN
  ProcessParameters(srcName, metaName, docName);
  AssemblePage(srcName, metaName, docName);
END AssemblePage.
</code></pre>
<h3 id="next-previous">Next, Previous</h3>
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Clock</a></li>
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