Basic pandoc module

lib/Pandoc.rakumod

@@ -0,0 +1,49 @@
+#| Interaction with pandoc
+unit module Pandoc;
+
+use JSON::Fast;
+
+sub markdown-title(IO::Path:D $file --> Str:D) is export {
+    # Call into pandoc
+    my $pandoc = run 'pandoc', '-t', 'JSON', $file, :out, :err;
+    my $output = $pandoc.out.slurp: :close;
+    my $stderr = $pandoc.err.slurp: :close;
+
+    # Throw an error if pandoc failed
+    if !$pandoc {
+       die "Pandoc exited with {$pandoc.exitcode}\nout: $output\nerr: $stderr";
+    }
+
+    # Parse out output from pandoc, we are making an executive decision to trust
+    # pandoc here, so we won't do any error handling for pandoc's output
+    my $parsed = from-json $output;
+    # Extract a list of top level headers from the pandoc output, this should
+    # only have one element in it, but as this is user input, its untrusted and
+    # we need to do some error handling
+    my @headers = $parsed.blocks.grep(*.t == "Header").grep(*.c[0] == 1);
+    if @headers.elems > 1 {
+        die "More than one top level header in $file";
+    };
+    if @headers.elems == 0 {
+        die "No top level hearders in $file";
+    };
+
+    # Extract the header and process it into a string
+    my @header = @headers[0].c[2];
+    my $title = "";
+    for @header -> $component {
+        given $component.t {
+            when "Str" {
+                $title = $title ~ $component.c;
+            }
+            when "Space" {
+                $title = $title ~ " ";
+            }
+            default {
+                die "Invalid component type: $_";
+            }
+        }
+    }
+
+    return $title;
+}