#!/usr/bin/env perl

use Cwd qw(getcwd);
use File::Basename qw(dirname basename);
use File::Copy::Recursive qw(dircopy);
use File::Find qw(finddepth);
use File::Path qw(make_path);
use File::Slurp;
use POSIX qw(strftime);
use Text::FrontMatter::YAML;
use Text::Template;
use Text::MultiMarkdown 'markdown';

use strict;
use utf8;

use constant {
    OUT_PATH => "/out",
    POSTS_PATH => "/posts",
    ASSETS_PATH => "/assets",
    PAGES_PATH => "/pages",
    TEMPLATES_PATH => "/templates",
};

# globals
my $cwd = getcwd;
my $post_dir = $cwd . POSTS_PATH;
my $pages_dir = $cwd . PAGES_PATH;
my $tmpl_dir = $cwd . TEMPLATES_PATH;
my $post_tmpl = Text::Template->new(SOURCE => "$tmpl_dir/post.html.tmpl");
my $assets_path = $cwd . ASSETS_PATH;
my $out_path = $cwd . OUT_PATH;
my $postout_path = $out_path . POSTS_PATH;

# Converts a post file to a metadata hash.
#
# Takes one argument, the path to the post file.
#
# Returns a hash with the relevant metadata (body text is stored as
# $metadata{"content"}, desired filename is stored as
# $metadata{"fname"}).
sub post_to_meta {
    defined(my $fname = shift) or warn "No filename argument!";

    my $fdata = read_file($fname);
    my $mdfm = Text::FrontMatter::YAML->new(
        document_string => $fdata
    );

    my $metadata = $mdfm->frontmatter_hashref;

    if (chomp($mdfm->body_text) ne "") {
        my $parser = Text::MultiMarkdown->new(
            disable_bibliography => 1,
            use_metadata => 0,
            document_format => 'fragment'
        );

        # for very funny bits, i assure you
        $mdfm->body_text =~ s{\$cn\$}{
            "<a class=\"fn\">[citation needed]</a>"
        }egm;

        $metadata->{content} = $parser->markdown( $mdfm->body_text );
    }

    # HACK: Stuffing the basename in the metadata because I don't want
    # to deal with hashes of hashes
    $metadata->{fname} = basename($fname) unless exists($metadata->{"fname"});

    $metadata;
}

# Gets an array of all posts for a directory.
#
# Takes one argument, the path to the posts directory.
#
# Returns an array of metadata hashes (see post_to_meta above for
# more on what those hashes look like).
sub all_posts_for_dir {
    defined(my $postdir = shift) or warn "No directory argument!";
    my @posts;

    opendir(PD, $postdir) or die $!;
    while (my $fname = readdir(PD)) {
        next if ($fname =~ /^\.+$/);
        my $post = &post_to_meta("$postdir/$fname");
        push @posts, $post;
    }
    closedir(PD);

    sort { $b->{created} cmp $a->{created} } @posts;
}

sub all_pages_for_dir {
    defined(my $pagedir = shift) or warn "No directory argument!";
    my @pages;

    finddepth(sub {
            return if ($File::Find::name =~ /^\.+$/);
            my %page;
            $_ = $File::Find::name;
            if (/^$pagedir\/(.+).tmpl$/) {
                $page{fname} = $1;
                $page{tmpl} = Text::Template->new(SOURCE => $File::Find::name);
                push @pages, \%page;
            }
        }, $pagedir);

    @pages;
}

sub mkpath {
    make_path( shift, { error => \my $path_err } );
    if ($path_err && @$path_err) {
        print "Errors occurred while making posts directory!\n";
        foreach my $err (@$path_err) {
            my ($path, $msg) = %$err;
            if ($path eq '') {
                print "  $msg\n";
            } else {
                print "  $path: $msg\n";
            }
        }
        # effectively die
        return 0;
    } else {
        return 1;
    }
}


sub include_tmpl {
    my $tmpl_name = shift;
    # TODO: do we want to cache snippet-type templates like this?
    my $tmpl = Text::Template->new(SOURCE => "$tmpl_dir/$tmpl_name.tmpl");
    if (defined $tmpl) {
        my $props = shift;
        $tmpl->fill_in(HASH => { props => \$props });
    } else {
        "error: $tmpl_dir/$tmpl_name.tmpl is missing"
    }
}

## End subroutines


# subroutines used in templates
my %utils = (
    strftime => \&strftime,
    include_tmpl => \&include_tmpl,
);


# make posts dir or die
mkpath($postout_path) or die "Unable to create directory.";

my @posts = all_posts_for_dir $post_dir;
print "Generating blog posts...\n";
foreach my $post (@posts) {
    if (!exists $post->{content}) {
        print "  $post->{fname} has no content, not making a page...\n";
        next;
    }
    print "  Processing $post->{fname}...\n";
    my %post_hash = %utils;
    $post_hash{post} = \$post;
    my $post_content = $post_tmpl->fill_in(HASH => \%post_hash);
    if (defined($post_content)) {
        open(POSTOUT, '>', "$postout_path/$post->{fname}.html") or die("Unable to write $post->{fname}.html: $!");
        print POSTOUT $post_content;
        close(POSTOUT);
    } else {
        die "Failed to process $post->{fname}: $Text::Template::ERROR";
    }
}

print "Generating pages...\n";
my @pages = all_pages_for_dir $pages_dir;
foreach my $pg (@pages) {
    mkpath(dirname("$out_path/" . $pg->{fname})) or die "Unable to create directory.";
    print "  Processing $pg->{fname}...\n";
    my %page_hash = %utils;
    $page_hash{posts} = \@posts;
    my $page_content = $pg->{tmpl}->fill_in(HASH => \%page_hash);
    if (defined($page_content)) {
        open(PGOUT, '>', "$out_path/$pg->{fname}") or die("Unable to write $pg->{fname}: $!");
        print PGOUT $page_content;
        close(PGOUT);
    } else {
        die "Failed to process $pg->{fname}: $Text::Template::ERROR";
    }
}

print "Copying static assets...\n";
local $File::Copy::Recursive::RMTrgDir = 2;
dircopy($assets_path, "$out_path/" . ASSETS_PATH) or die "Unable to copy assets: $!";

print "Done! Artifacts have been stored in $out_path.\n";