<?php

declare(strict_types=1);

namespace App\Services\FormBuilder;

use App\Exceptions\FormBuilder\InvalidOptionSpecException;
use App\Models\FormBuilder\FormField;
use App\Models\FormBuilder\FormFieldLibrary;
use App\Models\FormBuilder\FormFieldOption;
use Illuminate\Support\Collection;
use Illuminate\Support\Facades\DB;

/**
 * Owns all writes to `form_field_options`. Single source of truth for:
 *
 *   - row-shape enforcement (value/label/sort_order/translations)
 *   - duplicate-value detection at the spec level (cleaner 422 than the
 *     bare DB unique-constraint violation)
 *   - library → field row-copy on insertFromLibrary (addendum Q3
 *     row-copy mandate)
 *   - serialisation into the rich-shape JSON consumed by snapshot
 *     writer, API resources, and FilterRegistryController
 *
 * Pattern: one row per (owner, value). An empty specs array on
 * `replaceOptions()` clears all option rows for the owner.
 *
 * Activity log convention — matches WS-5a / §17.4.2 / §17.5: emit
 * `field.options_replaced` on the parent `FormField` only, not on
 * `FormFieldLibrary`. Library-level audits live elsewhere.
 *
 * See ARCH-FORM-BUILDER §17.6 (WS-5d) for the broader rationale.
 */
final class FormFieldOptionService
{
    /**
     * Locale shape: BCP-47 short form — `nl`, `en`, `nl_BE`, `en_GB`.
     */
    private const LOCALE_PATTERN = '/^[a-z]{2}(_[A-Z]{2})?$/';

    /**
     * Eager, ordered by `sort_order`. Scope-aware via the active
     * organisation context.
     *
     * @return Collection<int, FormFieldOption>
     */
    public function optionsFor(FormField|FormFieldLibrary $owner): Collection
    {
        $type = $this->ownerTypeFor($owner);

        return FormFieldOption::query()
            ->where('owner_type', $type)
            ->where('owner_id', $owner->getKey())
            ->orderBy('sort_order')
            ->get();
    }

    /**
     * Replace the full option set on an owner transactionally. Validates
     * every spec's shape (value / label / sort_order / translations /
     * uniqueness) before any write lands.
     *
     * @param  list<array{value:string,label:string,sort_order:int,translations?:array<string,string>}>  $specs
     * @return Collection<int, FormFieldOption>
     */
    public function replaceOptions(FormField|FormFieldLibrary $owner, array $specs): Collection
    {
        $this->assertSpecsValid($specs);

        $ownerType = $this->ownerTypeFor($owner);

        return DB::transaction(function () use ($owner, $ownerType, $specs): Collection {
            FormFieldOption::query()
                ->withoutGlobalScopes()
                ->where('owner_type', $ownerType)
                ->where('owner_id', $owner->getKey())
                ->delete();

            foreach ($specs as $spec) {
                FormFieldOption::query()->withoutGlobalScopes()->create([
                    'owner_type' => $ownerType,
                    'owner_id' => $owner->getKey(),
                    'value' => $spec['value'],
                    'label' => $spec['label'],
                    'sort_order' => $spec['sort_order'],
                    'translations' => $this->normaliseTranslations($spec['translations'] ?? null),
                ]);
            }

            $fresh = $this->optionsFor($owner);

            if ($owner instanceof FormField) {
                $owner->logFieldChange('field.options_replaced', [
                    'options' => $this->toJsonShape($fresh),
                ]);
            }

            return $fresh;
        });
    }

    /**
     * Row-copy from a library entry to a freshly-inserted field
     * (addendum Q3 row-copy mandate). Every column is preserved; only
     * `owner_type` / `owner_id` change. No activity-log emit — the
     * wrapping library-insert emits its own field-creation event.
     *
     * @return Collection<int, FormFieldOption>
     */
    public function copyOptions(FormFieldLibrary|FormField $from, FormField|FormFieldLibrary $to): Collection
    {
        $rows = $this->optionsFor($from);

        if ($rows->isEmpty()) {
            return $rows;
        }

        $toType = $this->ownerTypeFor($to);

        return DB::transaction(function () use ($rows, $to, $toType): Collection {
            foreach ($rows as $row) {
                FormFieldOption::query()->withoutGlobalScopes()->create([
                    'owner_type' => $toType,
                    'owner_id' => $to->getKey(),
                    'value' => $row->value,
                    'label' => $row->label,
                    'sort_order' => $row->sort_order,
                    'translations' => is_array($row->translations) && $row->translations !== []
                        ? $row->translations
                        : null,
                ]);
            }

            return $this->optionsFor($to);
        });
    }

    /**
     * Serialise an option collection into the rich-shape array consumed
     * by snapshot writer, API resources, and FilterRegistryController.
     * Returns the mapped list (possibly empty); callers handle
     * empty-collection → `null` emit at the resource boundary.
     *
     * @param  Collection<int, FormFieldOption>  $options
     * @return list<array{value:string,label:string,sort_order:int,translations?:array<string,string>}>
     */
    public function toJsonShape(Collection $options): array
    {
        return $options
            ->sortBy('sort_order')
            ->values()
            ->map(fn (FormFieldOption $option) => $option->toJsonShape())
            ->all();
    }

    /**
     * Public spec-shape gate — used by FormRequests (WS-5d commit 3) to
     * reject malformed specs at the HTTP boundary before any write
     * lands.
     *
     * @param  list<array<string, mixed>>  $specs
     */
    public function assertSpecsValid(array $specs): void
    {
        $seenValues = [];

        foreach ($specs as $index => $spec) {
            if (! is_array($spec)) {
                throw new InvalidOptionSpecException(
                    "Option spec at index {$index} must be an array.",
                );
            }

            $value = $spec['value'] ?? null;
            if (! is_string($value) || $value === '' || strlen($value) > 255) {
                throw new InvalidOptionSpecException(
                    "Option spec at index {$index}: 'value' is required, must be a non-empty string ≤255 chars.",
                );
            }

            $label = $spec['label'] ?? null;
            if (! is_string($label) || $label === '' || strlen($label) > 255) {
                throw new InvalidOptionSpecException(
                    "Option spec at index {$index}: 'label' is required, must be a non-empty string ≤255 chars.",
                );
            }

            if (! array_key_exists('sort_order', $spec)
                || ! is_int($spec['sort_order'])
                || $spec['sort_order'] < 0) {
                throw new InvalidOptionSpecException(
                    "Option spec at index {$index}: 'sort_order' is required, must be a non-negative integer.",
                );
            }

            if (array_key_exists('translations', $spec) && $spec['translations'] !== null) {
                $translations = $spec['translations'];
                if (! is_array($translations)) {
                    throw new InvalidOptionSpecException(
                        "Option spec at index {$index}: 'translations' must be an associative array of locale ⇒ string.",
                    );
                }
                foreach ($translations as $locale => $translated) {
                    if (! is_string($locale) || preg_match(self::LOCALE_PATTERN, $locale) !== 1) {
                        throw new InvalidOptionSpecException(
                            "Option spec at index {$index}: invalid locale key '{$locale}' (expected BCP-47 short form e.g. 'nl', 'en_GB').",
                        );
                    }
                    if (! is_string($translated) || $translated === '' || strlen($translated) > 255) {
                        throw new InvalidOptionSpecException(
                            "Option spec at index {$index} locale '{$locale}': translated label must be a non-empty string ≤255 chars.",
                        );
                    }
                }
            }

            if (in_array($value, $seenValues, true)) {
                throw new InvalidOptionSpecException(
                    "Option spec at index {$index}: duplicate value '{$value}' within the spec list.",
                );
            }
            $seenValues[] = $value;
        }
    }

    private function ownerTypeFor(FormField|FormFieldLibrary $owner): string
    {
        return $owner instanceof FormField ? 'form_field' : 'form_field_library';
    }

    /**
     * Empty translation bags are stored as NULL — keeps query semantics
     * clean and avoids whitespace differences between equivalent rows.
     *
     * @param  array<string, string>|null  $translations
     * @return array<string, string>|null
     */
    private function normaliseTranslations(?array $translations): ?array
    {
        if ($translations === null || $translations === []) {
            return null;
        }

        return $translations;
    }
}