<?php

declare(strict_types=1);

namespace LogseqGem;

use League\CommonMark\Node\Inline\Text;
use League\CommonMark\Extension\CommonMark\Node\Inline\Link;
use League\CommonMark\Extension\CommonMark\Node\Block\ListBlock;
use League\CommonMark\Extension\CommonMark\Node\Block\ListItem;

class ArticleParser extends Parser {
    private ?array $properties;

    public function convert(): string {
        $gemtext = [];
        $this->properties = [];

        $in_frontmatter = true;

        $node = null; //current node
        $last_node = null; //updated every time
        $previous_node = null; // we only update this for significant nodes

        $block_level = 0;
        $list_item = 0;

        $walker = $this->document->walker();
        while ($event = $walker->next()) {
            $entering = $event->isEntering();
            $last_node = $node;
            $node = $event->getNode();

            // treat empty node as a newline
            if ($node instanceof ListItem && $last_node === $node && !$entering) {
                $gemtext[] = '';
                continue;
            }

            if (!$entering) {
                if ($node instanceof ListBlock) {
                    $block_level -= 1;
                    $list_item = 0;
                }

                continue;
            }

            if ($node instanceof ListBlock) {
                $block_level += 1;
                $in_frontmatter = false;
                continue;
            }

            if ($node instanceof Text) {
                $text = $node->getLiteral();

                if ($in_frontmatter) {
                    if (preg_match('/^([A-Za-z-]+):: (.*)/', $text, $matches)) {
                        $this->properties[$matches[1]] = $matches[2];
                        continue;
                    } else {
                        $in_frontmatter = false;
                    }
                }

                if ($block_level > 1) {
                    $list_item += 1;

                    $leader = $list_item === 1 ? "\n" : "";
                    $gemtext[] = $leader . '* ' . $text;
                } else {
                    $leader = $previous_node ? "\n" : "";
                    $gemtext[] = $leader . $text;
                }

                $previous_node = $node;

                continue;
            }

            if ($node instanceof Link) {
                $label = $walker->next()->getNode();
                if (!$label instanceof Text) {
                    throw new \Exception('Expected next node in Link to be Text, got ' . get_class($label));
                }

                $leader = ($previous_node && !$previous_node instanceof Link) ? "\n" : "";
                $gemtext[] = $leader . sprintf("=> %s %s", $node->getUrl(), $label->getLiteral());

                $previous_node = $node;

                continue;
            }
        }

        return implode("\n", $gemtext);
    }

    public function getProperties(): array {
        if (is_null($this->properties)) {
            throw new \Exception("Cannot get properties before converting a document");
        }
        return $this->properties;
    }

    public function isPublished(): bool {
        return (($this->getProperties()['status'] ?? '') === 'published');
    }
}