<?php

declare(strict_types=1);

namespace LIT\MCP\Integrations\Divi\Pages;

use LIT\MCP\Abilities\Errors;
use LIT\MCP\Abilities\Rev;
use LIT\MCP\Abilities\ToolResult;
use LIT\MCP\Abilities\WriteFailed;
use LIT\MCP\ChangeLog\ChangeLog;
use LIT\MCP\Integrations\Divi\BlockTree\Block;
use LIT\MCP\Integrations\Divi\BlockTree\NodeIndex;
use LIT\MCP\Integrations\Divi\BlockTree\NodeSummary;
use LIT\MCP\Integrations\Divi\BlockTree\Outline;
use LIT\MCP\Integrations\Divi\BlockTree\Serializer;
use LIT\MCP\Integrations\Divi\Design\DesignSystemReader;
use LIT\MCP\Integrations\WordPress\PostChangeResult;
use WP_Error;

/**
 * The shared frame of every Divi write (spec §5.6): load with rights and the tree_rev lock
 * (ruling P16; a mismatch is rev_mismatch and nothing is written), let the ability change the
 * tree – only when its whole input validated (all or nothing) –, serialize, save via DiviSaver,
 * then lit_mcp_after_save, change log and the ToolResult with changed nodes, affected outline,
 * quality warnings (spec §5.5), revision_id, the new rev and tree_rev. Not final so abilities
 * can be tested with a mock.
 */
class DiviWriter
{
    public const OUTLINE_TRUNCATED = 'Die Übersicht der geänderten Abschnitte ist gekürzt; vollständig mit '
        . 'lit-divi-outline lesen.';

    public function __construct(
        private DiviPageLoader $loader,
        private DiviSaver $saver,
        private ChangeLog $log,
        private DesignSystemReader $design,
        private DiviComposition $composition
    ) {
    }

    /** @return array<string, array<string, mixed>> post_id and tree_rev of every Divi write. */
    public static function inputProperties(): array
    {
        return [
            'post_id' => ['type' => 'integer', 'minimum' => 1],
            'tree_rev' => [
                'type' => 'string',
                'description' => 'tree_rev aus lit-divi-outline bzw. der letzten Divi-Änderung (Pflicht).',
            ],
        ];
    }

    /** @return array<string, array<string, mixed>> Target position of insert and move. */
    public static function positionProperties(): array
    {
        return [
            'parent' => [
                'type' => 'string',
                'description' => 'Pfad-ID des Elternknotens (z. B. Spalte "s0.r0.c1"); ohne parent/before/after: '
                    . 'Ende der Seite.',
            ],
            'before' => ['type' => 'string', 'description' => 'Pfad-ID: vor diesem Knoten einfügen.'],
            'after' => ['type' => 'string', 'description' => 'Pfad-ID: nach diesem Knoten einfügen.'],
            'index' => ['type' => 'integer', 'minimum' => 0, 'description' => 'Position unter parent (0 = zuerst).'],
        ];
    }

    /**
     * The page to change, after rights, type, layout and the tree_rev lock were checked.
     *
     * @param array<string, mixed> $input
     */
    public function page(array $input): DiviPage|WP_Error
    {
        $page = $this->loader->load($input['post_id'] ?? null, true);
        if ($page instanceof WP_Error) {
            return $page;
        }

        $problem = $this->loader->writable($page);
        if ($problem !== null) {
            return $problem;
        }

        if (! is_string($input['tree_rev'] ?? null) || $input['tree_rev'] !== $page->treeRev()) {
            return Errors::revMismatch(
                'Die Divi-Seite wurde seit dem letzten Lesen geändert (tree_rev passt nicht); nichts wurde '
                    . 'geschrieben.',
                DiviPageLoader::OUTLINE_HINT
            );
        }

        return $page;
    }

    /**
     * The Compose classes for $page: bound to its entry, so placeholders and $variable(…)$
     * references are checked against Divi's dynamic content options for it (ruling S22).
     */
    public function composition(DiviPage $page): DiviComposition
    {
        return $this->composition->forPost((int) $page->post->ID);
    }

    /** Section label around $block, for automatic admin labels ("" when none). */
    public static function sectionLabel(NodeIndex $index, ?Block $block): string
    {
        for ($node = $block; $node !== null; $node = self::parentBlock($index, $node)) {
            if ($node->name() === 'divi/section') {
                return NodeSummary::label($node);
            }
        }

        return '';
    }

    /**
     * Saves the changed tree of $page and returns the ToolResult array. Call it only when the
     * whole input validated – every error before means nothing is written.
     *
     * @param array<string, mixed> $input
     * @return array<string, mixed>
     * @throws WriteFailed
     */
    public function save(string $ability, DiviPage $page, DiviChange $change, array $input): array
    {
        $post = $page->post;
        $content = Serializer::document($page->document);
        if ($content === (string) $post->post_content) {
            return ToolResult::ok('Keine Änderung – die Seite ist bereits so.')
                ->rev(Rev::ofPost($post))
                ->with('tree_rev', $page->treeRev())
                ->warnings($change->warnings())
                ->toArray();
        }

        $index = NodeIndex::build($page->document);
        $quality = $this->composition->warnings()->collect($index, $change->touched());
        $warnings = array_merge($change->warnings(), $quality);

        try {
            $saved = $this->saver->save($post, $content);
        } catch (WriteFailed $e) {
            if (! $e->rolledBack) {
                $this->log->recordPartial(
                    $ability,
                    (string) $post->post_type,
                    (string) $post->ID,
                    sprintf('Divi "%s": Änderung nur teilweise zurückgenommen', $post->post_title),
                    $e->revisionId
                );
            }
            throw $e;
        }

        $outline = $this->outline($index, $change);
        if ($outline['truncated']) {
            $warnings[] = self::OUTLINE_TRUNCATED;
        }

        $result = (new PostChangeResult(
            $ability,
            $this->log,
            (int) $post->ID,
            'die Änderung',
            array_merge($warnings, $saved['warnings'])
        ))->afterSave($input);
        $updated = $result->reread($post) ?? $post;
        $summary = sprintf('Divi "%s": %s', $post->post_title, $change->summary);
        $result->log((string) $post->post_type, $summary, $saved['revision_id']);

        $status = sprintf('%s (Status unverändert: %s).', $change->summary, $updated->post_status);
        $tool = $result->result($status, $updated)
            ->revisionId($saved['revision_id'])
            ->outline($outline['text'])
            ->with('tree_rev', Rev::of((string) $updated->post_content))
            ->urls((string) get_preview_post_link($updated), $page->editUrl());
        foreach ($change->entries() as $entry) {
            $id = $entry['id'] ?? ($entry['block'] !== null ? $index->idOf($entry['block']) : null);
            $tool->changed($id ?? '?', $entry['type'], $entry['action'], $entry['label']);
        }

        return $tool->toArray();
    }

    /**
     * Outline of the sections that contain changed nodes (breadth limit of ruling S18).
     *
     * @return array{text: ?string, truncated: bool}
     */
    private function outline(NodeIndex $index, DiviChange $change): array
    {
        $sections = [];
        foreach ($change->entries() as $entry) {
            $id = $entry['block'] !== null ? $index->idOf($entry['block']) : null;
            if ($id !== null) {
                $sections[explode('.', $id)[0]] = true;
            }
        }

        if ($sections === []) {
            return ['text' => null, 'truncated' => false];
        }

        $outline = new Outline($this->design->read()->presetNames());
        $texts = [];
        $truncated = false;
        foreach (array_keys($sections) as $sectionId) {
            $texts[] = $outline->text($outline->rows($index, (string) $sectionId));
            $truncated = $truncated || $outline->wasTruncated();
        }

        return ['text' => implode("\n", $texts), 'truncated' => $truncated];
    }

    private static function parentBlock(NodeIndex $index, Block $block): ?Block
    {
        $parent = $index->parentOf($block);

        return $parent instanceof Block && $parent->name() !== 'divi/placeholder' ? $parent : null;
    }
}