use v6.e.PREVIEW;

#| Post database
unit module DB;

use Pandoc;
use JSON::Class:auth<zef:vrurg>;

use DB::Post;
use DB::BlogMeta;
use DB::MarkdownPost;
use DB::IdrisPost;
use DB::PlaceholderPost;

subset PostTypes where MarkdownPost:D | IdrisPost:D | PlaceholderPost:D;

#| The top level posts database
class PostDB {
   #| The metadata for the blog
   has BlogMeta:D $.meta is required;
   #| A mapping from post ids to posts
   # has %.posts is Posts;
   has %.posts{Int} of PostTypes = %();
   #| The post id to use for placeholder posts
   has Int $.placeholder-id = 0;

   #| Get the next unused post ID
   method next-post-id(--> Int) {
       if %!posts.elems > 0 {
           %!posts.keys.max + 1
       } else {
           0
       }
   }

   #| Insert a new post to the DB, returning its id
   method insert-post(PostTypes $post --> Int) {
       my $id = self.next-post-id;
       %!posts{$id} = $post;
       $id
   }

   #| Initialize a new database
   method init(BlogMeta:D $meta --> PostDB:D) {
       my %posts{Int} of PostTypes = %();
       %posts{0} = PlaceholderPost.empty;
       PostDB.new(
           meta => $meta,
           posts => %posts,
       )
   }

   #| Write a database to a directory
   method write(IO::Path:D $dir) {
       my $posts-dir = $dir.add('posts/');
       # Make sure directory structrue exists
       mkdir $dir unless $dir.e;
       mkdir $posts-dir unless $posts-dir.e;
       # Write out metadata
       # TODO: Track changes and only write changed files
       $dir.add('meta.json').spurt: $!meta.to-json;
       # Write out posts (ids are the filename)
       for %!posts.kv -> $key, $value {
          $posts-dir.add("$key.json").spurt: $value.to-json;
       }
   }
}

sub read-db(IO::Path:D $dir --> PostDB:D) is export {
   my $posts-dir = $dir.add('posts/');
   die "DB directory does not exist" unless $dir.e;
   die "posts directory does not exist" unless $posts-dir.e;
   # Read metadata
   my $meta = BlogMeta.from-json: $dir.add('meta.json').slurp;
   # Read posts
   my %posts{Int} of PostTypes = %();
   for dir $posts-dir -> $post {
       my $id = $post.extension("").basename.Int;
       # TODO: Dejankify this, maybe see if we can work with parsed, but
       # unmarshalled json
       given $post.slurp {
           when /'"placeholder": true'/ {
               %posts{$id} = PlaceholderPost.from-json: $_;
           }
           when /'"markdown": true'/ {
               %posts{$id} = MarkdownPost.from-json: $_;
           }
           when /'"idris": true'/ {
               %posts{$id} = IdrisPost.from-json: $_;
           }
           default {
               die "Unsupported post type: $post";
           }
       }
   }
   # Build db structure
   PostDB.new: meta => $meta, posts => %posts
}