<?php

use dokuwiki\Parsing\Handler;
use dokuwiki\Extension\SyntaxPlugin;
use dokuwiki\File\PageResolver;
use dokuwiki\Logger;
use dokuwiki\Search\MetadataSearch;

/**
 * DokuWiki Syntax Plugin Backlinks (Section-aware) — DEBUG BUILD.
 *
 * This file is a diagnostic copy. It logs every stage of the backlink
 * resolution pipeline so we can see exactly where entries are dropped.
 * Once the bug is found, apply the minimal fix to the real syntax.php
 * and delete this file.
 *
 * Syntax:  {{backlinkswas>[pagename][#filterNS][#!filterNS]...}}
 *
 * Original authors:
 *   Mark C. Prins <mprins@users.sf.net>
 *   Michael Klier <chi@chimeric.de>
 *   https://www.dokuwiki.org/plugin:backlinks
 *
 * Section-aware modifications:
 *   Wizardry and Steamworks <wizardry.steamworks@outlook.com>
 *
 * @license GPL 2 (http://www.gnu.org/licenses/gpl.html)
 */
class syntax_plugin_backlinkswas extends SyntaxPlugin
{
    public function getType(): string
    {
        return 'substition';
    }

    public function getPType(): string
    {
        return 'block';
    }

    public function getSort(): int
    {
        return 304;
    }

    public function connectTo($mode): void
    {
        $this->Lexer->addSpecialPattern('\{\{backlinkswas>.+?\}\}', $mode, 'plugin_backlinkswas');
    }

    public function handle($match, $state, $pos, Handler $handler): array
    {
        Logger::error("backlinkswas[handle]: RAW match=[" . $match . "] len=" . strlen($match));

        // strip {{backlinkswas> from start and }} from end  (15 chars)
        $match = substr($match, 15, -2);

        Logger::error("backlinkswas[handle]: stripped=[" . $match . "]");

        $includeNS = [];
        $excludeNS = [];

        if (str_contains($match, "#")) {
            $filters = explode('#', substr(strstr($match, "#"), 1));
            $match   = strstr($match, "#", true);

            foreach ($filters as $filter) {
                if ($filter === '') {
                    continue;
                }
                if (str_starts_with($filter, '!')) {
                    $excludeNS[] = substr($filter, 1);
                } else {
                    $includeNS[] = $filter;
                }
            }
        }

        Logger::error("backlinkswas[handle]: match=[" . $match . "] includeNS=" . json_encode($includeNS) . " excludeNS=" . json_encode($excludeNS));

        return ([$match, $includeNS, $excludeNS]);
    }

    public function render($format, Doku_Renderer $renderer, $data): bool
    {
        global $lang;
        global $INFO;
        global $ID;

        Logger::error(sprintf(
            "backlinkswas[render]: ENTER format=[%s] ID=[%s] INFO[id]=[%s] data0=[%s] data1=%s data2=%s",
            $format,
            $ID ?? 'null',
            $INFO['id'] ?? 'null',
            var_export($data[0] ?? null, true),
            json_encode($data[1] ?? []),
            json_encode($data[2] ?? [])
        ));

        $id = $ID;
        // If it's a sidebar, get the original id.
        if ($INFO != null) {
            $id = $INFO['id'];
        }

        Logger::error("backlinkswas[render]: resolved id=[$id]");

        $match = $data[0];
        $match = ($match == '.') ? $id : $match;

        Logger::error("backlinkswas[render]: after dot-resolution match=[$match]");

        if (str_contains($match, ".:")) {
            $resolver = new PageResolver($id);
            $match = $resolver->resolveId($match);
            Logger::error("backlinkswas[render]: after PageResolver match=[$match]");
        }

        if ($format != 'xhtml') {
            Logger::error("backlinkswas[render]: non-xhtml format, bailing");
            return false;
        }

        $renderer->info['cache'] = false;

        // 1. Candidate pages from the index.
        $candidates = (new MetadataSearch())->backlinks($match);
        Logger::error("backlinkswas[render]: primary lookup match=[$match] candidates=" . json_encode($candidates));

        if ($candidates === []) {
            // Fall back to a wiki:-prefixed form in case the target was
            // indexed under a URL-style /wiki/... prefix.
            $alt = 'wiki:' . ltrim(str_replace('/', ':', $match), ':');
            if ($alt !== $match) {
                $candidates = (new MetadataSearch())->backlinks($alt);
                Logger::error("backlinkswas[render]: fallback lookup alt=[$alt] candidates=" . json_encode($candidates));
            }
        }

        $includeNS = $data[1];
        $excludeNS = $data[2];

        // 2. Namespace include filter.
        if ($candidates !== [] && $includeNS !== []) {
            Logger::error("backlinkswas[render]: applying includeNS=" . json_encode($includeNS));
            $candidates = array_filter(
                $candidates,
                static function ($ns) use ($includeNS) {
                    foreach ($includeNS as $filterNS) {
                        if (stripos($ns, (string) $filterNS) === 0) {
                            return true;
                        }
                    }
                    return false;
                }
            );
            Logger::error("backlinkswas[render]: after includeNS candidates=" . json_encode(array_values($candidates)));
        }

        // 3. Namespace exclude filter.
        if ($candidates !== [] && $excludeNS !== []) {
            Logger::error("backlinkswas[render]: applying excludeNS=" . json_encode($excludeNS));
            $candidates = array_filter(
                $candidates,
                static function ($ns) use ($excludeNS) {
                    foreach ($excludeNS as $filterNS) {
                        if (stripos($ns, (string) $filterNS) === 0) {
                            return false;
                        }
                    }
                    return true;
                }
            );
            Logger::error("backlinkswas[render]: after excludeNS candidates=" . json_encode(array_values($candidates)));
        }

        // 4. Resolve each candidate into (page, fragment) pairs.
        $backlinks = [];
        foreach ($candidates as $candidate) {
            Logger::error("backlinkswas[render]: scanning candidate=[$candidate] for target=[$match]");
            $fragments = $this->findLinkLocations($candidate, $match, $id);
            Logger::error("backlinkswas[render]: candidate=[$candidate] fragments=" . json_encode($fragments));
            foreach ($fragments as $fragment) {
                $key = $candidate . '#' . $fragment;
                $backlinks[$key] = [$candidate, $fragment];
            }
        }
        $backlinks = array_values($backlinks);

        Logger::error("backlinkswas[render]: final backlinks=" . json_encode(
            array_map(static fn($x) => $x[0] . '#' . $x[1], $backlinks)
        ));

        $renderer->doc .= '<div id="plugin__backlinkswas">' . "\n";

        if ($backlinks !== []) {
            $renderer->doc .= '<ul class="idx">';

            foreach ($backlinks as [$page, $fragment]) {
                $name = p_get_metadata($page, 'title');
                if (empty($name)) {
                    $name = $page;
                }

                $label = $name;
                if ($fragment !== '') {
                    $sectionTitle = $this->getSectionTitle($page, $fragment);
                    if ($sectionTitle !== '') {
                        $label .= ' » ' . $sectionTitle;
                    }
                }

                $targetId = ':' . $page;
                if ($fragment !== '') {
                    $targetId .= '#' . $fragment;
                }

                Logger::error("backlinkswas[render]: emitting link target=[$targetId] label=[$label]");

                $renderer->doc .= '<li><div class="li">';
                $renderer->doc .= html_wikilink($targetId, $label);
                $renderer->doc .= '</div></li>' . "\n";
            }

            $renderer->doc .= '</ul>' . "\n";
        } else {
            Logger::error("backlinkswas[render]: nothing found, rendering empty message");
            $renderer->doc .= "<strong>Plugin Backlinks: " . $lang['nothingfound'] . "</strong>" . "\n";
        }

        $renderer->doc .= '</div>' . "\n";

        return true;
    }

    /**
     * Find every location in $sourcePageId where a link to $targetPageId occurs.
     *
     * @return string[] List of fragments (may contain '' for top-of-page).
     */
    protected function findLinkLocations(string $sourcePageId, string $targetPageId, string $contextId): array
    {
        $file = wikiFN($sourcePageId);
        $exists = file_exists($file);
        Logger::error("backlinkswas[findLinkLocations]: source=[$sourcePageId] file=[$file] exists=" . ($exists ? 'yes' : 'no'));

        if (!$exists) {
            return [];
        }

        $source = io_readFile($file, false);
        Logger::error("backlinkswas[findLinkLocations]: source length=" . strlen($source));

        if ($source === '') {
            return [];
        }

        // Resolve the target the same way DokuWiki would, so relative links match.
        $resolver = new PageResolver($sourcePageId);
        $resolvedTarget = $resolver->resolveId($targetPageId);
        Logger::error("backlinkswas[findLinkLocations]: context=[$sourcePageId] target=[$targetPageId] resolvedTarget=[$resolvedTarget] cleanTarget=[" . cleanID($resolvedTarget) . "]");

        $fragments = [];

        // DokuWiki link syntax: [[target]] or [[target|label]] or [[target#frag|label]]
        $pattern = '/\[\[([^\]\|]+)(?:\|[^\]]*)?\]\]/u';

        $count = preg_match_all($pattern, $source, $matches, PREG_OFFSET_CAPTURE);
        Logger::error("backlinkswas[findLinkLocations]: regex matched " . (int)$count . " link(s)");

        if (!$count) {
            return [];
        }

        $headings = $this->findHeadings($source);
        Logger::error("backlinkswas[findLinkLocations]: headings found=" . json_encode(array_map(
            static fn($h) => ['off' => $h['offset'], 'id' => $h['id'], 'title' => $h['title']],
            $headings
        )));

        foreach ($matches[1] as [$rawTarget, $offset]) {
            $rawTargetOrig = $rawTarget;
            $rawTarget = trim($rawTarget);

            $explicitFragment = '';
            if (str_contains($rawTarget, '#')) {
                [$rawTarget, $explicitFragment] = explode('#', $rawTarget, 2);
                $explicitFragment = trim($explicitFragment);
            }

            Logger::error("backlinkswas[findLinkLocations]: link raw=[$rawTargetOrig] cleaned=[$rawTarget] explicitFrag=[$explicitFragment] offset=[$offset]");

            if ($rawTarget === '' || str_contains($rawTarget, '://') || str_contains($rawTarget, '>')) {
                Logger::error("backlinkswas[findLinkLocations]:   -> skipped (external/empty)");
                continue;
            }

            $resolved = $resolver->resolveId($rawTarget);
            $resolvedClean = cleanID($resolved);
            $targetClean   = cleanID($resolvedTarget);

            Logger::error("backlinkswas[findLinkLocations]:   -> resolved=[$resolved] clean=[$resolvedClean] want=[$targetClean]");

            if ($resolvedClean !== $targetClean) {
                Logger::error("backlinkswas[findLinkLocations]:   -> MISMATCH, skipping");
                continue;
            }

            if ($explicitFragment !== '') {
                Logger::error("backlinkswas[findLinkLocations]:   -> MATCH, using explicit fragment=[$explicitFragment]");
                $fragments[] = cleanID($explicitFragment);
                continue;
            }

            $section = $this->headingBeforeOffset($headings, $offset);
            Logger::error("backlinkswas[findLinkLocations]:   -> MATCH, section=[$section]");
            $fragments[] = $section;
        }

        $result = array_values(array_unique($fragments));
        Logger::error("backlinkswas[findLinkLocations]: result=" . json_encode($result));

        return $result;
    }

    /**
     * Extract headings from raw wiki source.
     *
     * @return array<int, array{offset:int, id:string, title:string, level:int}>
     */
    protected function findHeadings(string $source): array
    {
        $headings = [];
        $lines = explode("\n", $source);
        $offset = 0;

        foreach ($lines as $line) {
            if (preg_match('/^(\s*)(={2,6})([^=].*?)\2\s*$/', $line, $m)) {
                $level = strlen($m[2]);
                $title = trim($m[3]);
                $id = $this->sectionId($title);
                if ($id !== '') {
                    $headings[] = [
                        'offset' => $offset,
                        'id'     => $id,
                        'title'  => $title,
                        'level'  => $level,
                    ];
                }
            }
            $offset += strlen($line) + 1;
        }

        return $headings;
    }

    /**
     * Mirror DokuWiki's section-ID generation.
     */
    protected function sectionId(string $title): string
    {
        $id = str_replace(' ', '_', strtolower($title));
        $id = preg_replace('/[^a-z0-9_\-\.]/u', '', $id);
        return $id;
    }

    /**
     * Find the ID of the nearest heading at or before $offset.
     * Returns '' if the link is above the first heading.
     */
    protected function headingBeforeOffset(array $headings, int $offset): string
    {
        $current = '';
        foreach ($headings as $h) {
            if ($h['offset'] > $offset) {
                break;
            }
            $current = $h['id'];
        }
        return $current;
    }

    /**
     * Look up the human-readable heading title for a fragment on a page.
     */
    protected function getSectionTitle(string $pageId, string $fragment): string
    {
        $file = wikiFN($pageId);
        if (!file_exists($file)) {
            return '';
        }
        $source = io_readFile($file, false);
        if ($source === '') {
            return '';
        }

        foreach ($this->findHeadings($source) as $h) {
            if ($h['id'] === $fragment) {
                return $h['title'];
            }
        }
        return '';
    }
}