<?php

declare(strict_types=1);

namespace LIT\MCP\Integrations\Divi\Pages;

use Closure;
use LIT\MCP\Integrations\Divi\Compose\DynamicContentRules;
use LIT\MCP\Integrations\Divi\Compose\VariableRef;
use LIT\MCP\Integrations\WordPress\Schema\ContentSchema;
use LIT\MCP\Integrations\WordPress\Schema\FieldDefinition;
use Throwable;

defined('ABSPATH') || exit;

/**
 * The fields of a post type Divi can show as text through dynamic content (answer F4, E12): custom_meta_<key>
 * reads post meta (F25/F26). Relation/file fields show IDs, Pods table storage is no post meta, protected keys
 * never (S12), unknown types not (ruling P9) – each omitted with its reason. Choice fields are offered, but
 * Divi shows their stored value, not the label (stage3b render: "senior") – note(). Hidden fields (security
 * audit M4) are neither offered nor named. Used by lit/divi-dynamic-sources and the Theme Builder body check.
 * Not final so abilities can be tested with a mock.
 */
class DynamicFields
{
    /** Field types Divi can show as text (arrays of strings are joined with ", ", F26). */
    public const TEXT_TYPES = ['string', 'text', 'number', 'integer', 'date', 'datetime', 'time', 'choice'];

    public const ID_TYPES = ['relation', 'file'];

    public const UNKNOWN = 'kein bekanntes Feld dieses Inhaltstyps';

    private const PREFIX = 'custom_meta_';

    /** Divi's option for a meta key typed in by hand (the key is in settings.meta_key). */
    private const MANUAL = 'custom_meta_manual_custom_field_value';

    /** @var Closure(string): ?string */
    private Closure $podStorage;

    /** @var array<string, array{0: list<array<string, string>>, 1: list<array<string, string>>}> offered() by type. */
    private array $known = [];

    /** @param (Closure(string): ?string)|null $podStorage Post type → Pods storage ("meta", "table"), null: none. */
    public function __construct(private ContentSchema $schema, ?Closure $podStorage = null)
    {
        $this->podStorage = $podStorage ?? self::defaultStorage(...);
    }

    /** @return array{0: list<array<string, string>>, 1: list<array<string, string>>} Offered and omitted fields. */
    public function offered(string $postType): array
    {
        $storage = ($this->podStorage)($postType);
        $fields = [];
        $omitted = [];
        foreach ($this->schema->fields($postType) as $field) {
            if ($field->status === FieldDefinition::HIDDEN) {
                continue;
            }

            $entry = ['key' => $field->key, 'label' => $field->label];
            $reason = self::omission($field, $storage);
            if ($reason !== null) {
                $omitted[] = $entry + ['reason' => $reason];
                continue;
            }

            $fields[] = $entry + [
                'type' => $field->type,
                'source' => $field->source,
                'placeholder' => '{{field:' . $field->key . '}}',
            ];
        }

        return [$fields, $omitted];
    }

    /**
     * offered() once per post type for reason()/note() – they run per key and type of a check, and the default
     * storage callback loads the pod each time (review M-12 b).
     *
     * @return array{0: list<array<string, string>>, 1: list<array<string, string>>}
     */
    private function known(string $postType): array
    {
        return $this->known[$postType] ??= $this->offered($postType);
    }

    /** Why {{field:$key}} would not show as text for $postType; null when it does. */
    public function reason(string $postType, string $key): ?string
    {
        [$fields, $omitted] = $this->known($postType);
        foreach ($fields as $field) {
            if ($field['key'] === $key) {
                return null;
            }
        }
        foreach ($omitted as $field) {
            if ($field['key'] === $key) {
                return $field['reason'];
            }
        }

        return self::UNKNOWN;
    }

    /** What to know about an offered field of $postType ($key) that shows other text than expected; else null. */
    public function note(string $postType, string $key): ?string
    {
        [$fields] = $this->known($postType);
        foreach ($fields as $field) {
            if ($field['key'] === $key && $field['type'] === 'choice') {
                return 'Auswahlfeld – Divi zeigt den gespeicherten Wert, nicht die Beschriftung';
            }
        }

        return null;
    }

    /**
     * The meta key the content reference $value reads, in both forms Divi resolves (ruling Q11, stage3b README
     * finding 12; DynamicContentOptionPostMetaKey.php:222-262): the name custom_meta_<key> (the plugin's form)
     * and the name post_meta_key with select_meta_key "custom_meta_<key>" (Divi's dialog), each also with a key
     * typed in by hand (custom_meta_manual_custom_field_value or post_meta_key with only meta_key). Null for
     * anything else. Reads, never validates – writing goes through VariableRef::canonical() (S29/S30).
     */
    public static function metaKeyOf(string $value): ?string
    {
        if (VariableRef::typeOf($value) !== 'content') {
            return null;
        }

        $name = VariableRef::nameOf($value);
        $settings = VariableRef::settingsOf($value);
        $manual = is_string($settings['meta_key'] ?? null) ? $settings['meta_key'] : '';
        if ($name === 'post_meta_key') {
            $selected = $settings['select_meta_key'] ?? '';
            if (! is_string($selected)) {
                return null;
            }
            if ($selected === '') {
                return $manual !== '' ? $manual : null;
            }
            $name = $selected;
        }

        if ($name === null || ! str_starts_with($name, self::PREFIX)) {
            return null;
        }
        if ($name === self::MANUAL) {
            return $manual !== '' ? $manual : null;
        }

        $key = str_replace(self::PREFIX, '', $name);

        return $key !== '' ? $key : null;
    }

    private static function omission(FieldDefinition $field, ?string $storage): ?string
    {
        return match (true) {
            ! DynamicContentRules::isMetaKey($field->key)
                => 'geschütztes oder ungültiges Meta-Feld (beginnt mit „_“)',
            $field->source === 'pods' && $storage === 'table'
                => 'Pods mit Tabellen-Speicherung – Divi liest nur Post-Meta',
            in_array($field->type, self::ID_TYPES, true)
                => 'Beziehungs- oder Dateifeld – Divi zeigt davon nur IDs',
            $field->type === 'unknown'
                => 'Feldtyp unbekannt – Divi zeigt womöglich keinen Text',
            ! in_array($field->type, self::TEXT_TYPES, true)
                => sprintf('Feldtyp „%s“ ist nicht textartig', $field->type),
            default => null,
        };
    }

    private static function defaultStorage(string $postType): ?string
    {
        if (! function_exists('pods_api')) {
            return null;
        }

        try {
            $pod = pods_api()->load_pod(['name' => $postType]);
        } catch (Throwable) {
            return null;
        }

        return is_object($pod) && method_exists($pod, 'get_storage') ? (string) $pod->get_storage() : null;
    }
}