<?php

namespace App\Services\Glpi;

use Illuminate\Support\Arr;
use Illuminate\Support\Collection;
use Illuminate\Support\Facades\Cache;
use Illuminate\Support\Facades\Http;
use Illuminate\Support\Facades\Log;
use Throwable;

class GlpiClient
{
    public const STATUSES = [
        1 => 'Nouveau',
        2 => 'En cours (assigné)',
        3 => 'En cours (planifié)',
        4 => 'En attente',
        5 => 'Résolu',
        6 => 'Clos',
    ];

    public const STATUS_CLOSED = 6;

    public const PRIORITIES = [
        1 => 'Très basse',
        2 => 'Basse',
        3 => 'Moyenne',
        4 => 'Haute',
        5 => 'Très haute',
        6 => 'Majeure',
    ];

    protected string $baseUrl;

    protected string $appToken;

    protected string $userToken;

    public function __construct()
    {
        $this->baseUrl = rtrim((string) config('glpi.api_url'), '/');
        $this->appToken = (string) config('glpi.app_token');
        $this->userToken = (string) config('glpi.user_token');
    }

    public function isConfigured(): bool
    {
        return $this->baseUrl !== '' && $this->appToken !== '' && $this->userToken !== '';
    }

    /**
     * The GLPI front-end base URL (for building links to tickets), derived
     * from the REST API URL by dropping the trailing "apirest.php".
     */
    public function frontUrl(): string
    {
        return preg_replace('#/apirest\.php$#', '', $this->baseUrl);
    }

    public function ticketUrl(int $ticketId): string
    {
        return $this->frontUrl()."/front/ticket.form.php?id={$ticketId}";
    }

    /**
     * Recent tickets for a GLPI entity, most recently modified first.
     *
     * @return array{tickets: array<int, array<string, mixed>>, total: int, error: ?string}
     */
    public function recentTicketsForEntity(int $entityId, int $limit = 8): array
    {
        if (! $this->isConfigured()) {
            return ['tickets' => [], 'total' => 0, 'error' => null];
        }

        return Cache::remember(
            "glpi.tickets.entity.{$entityId}.{$limit}",
            (int) config('glpi.cache_ttl_seconds', 60),
            function () use ($entityId, $limit) {
                try {
                    return $this->fetchRecentTickets($entityId, $limit);
                } catch (Throwable $e) {
                    Log::warning('GLPI: échec de récupération des tickets', [
                        'entity_id' => $entityId,
                        'message' => $e->getMessage(),
                    ]);

                    return ['tickets' => [], 'total' => 0, 'error' => "Impossible de joindre GLPI pour le moment."];
                }
            }
        );
    }

    /**
     * @return array{tickets: array<int, array<string, mixed>>, total: int, error: ?string}
     */
    protected function fetchRecentTickets(int $entityId, int $limit): array
    {
        return $this->withSession(function (string $sessionToken) use ($entityId, $limit) {
            $response = Http::withHeaders($this->headers($sessionToken))
                ->get("{$this->baseUrl}/search/Ticket", [
                    'criteria' => [
                        ['field' => 80, 'searchtype' => 'equals', 'value' => $entityId],
                        // GLPI's "notequals" searchtype is silently ignored by the search
                        // engine; excluding a value only works via a negated AND link.
                        ['link' => 'AND NOT', 'field' => 12, 'searchtype' => 'equals', 'value' => self::STATUS_CLOSED],
                    ],
                    // 4 = demandeur, 27 = nombre de suivis, 28 = nombre de tâches (les
                    // techniciens répondent parfois via une tâche plutôt qu'un suivi —
                    // les deux comptent comme des interactions), 95 = technicien
                    // responsable, 5 = technicien assigné (repli si 95 n'est pas renseigné).
                    'forcedisplay' => [2, 1, 12, 3, 4, 7, 21, 27, 28, 95, 5, 19],
                    'sort' => 19,
                    'order' => 'DESC',
                    'range' => '0-'.($limit - 1),
                ]);

            if ($response->failed()) {
                throw new GlpiException("GLPI a répondu avec une erreur (HTTP {$response->status()}).");
            }

            $rows = $response->json('data') ?? [];

            $technicianIds = collect($rows)
                ->flatMap(fn (array $row) => [
                    ...Arr::wrap($row['95'] ?? null),
                    ...Arr::wrap($row['5'] ?? null),
                ])
                ->filter()
                ->unique()
                ->values();

            $technicianNames = $this->resolveUserNames($sessionToken, $technicianIds);
            $lastInteractionAuthors = $this->fetchLastInteractionAuthors($sessionToken, $rows);

            $tickets = collect($rows)->map(function (array $row) use ($technicianNames, $lastInteractionAuthors) {
                $technicianIds = filled($row['95'] ?? null) ? Arr::wrap($row['95']) : Arr::wrap($row['5'] ?? null);
                $followupsCount = (int) ($row['27'] ?? 0);
                $tasksCount = (int) ($row['28'] ?? 0);
                $requesterIds = array_map('strval', Arr::wrap($row['4'] ?? null));

                // Nothing yet means the only thing on the ticket is the
                // requester's own opening message — nobody from support has
                // replied (via a followup or a task). Otherwise, check who
                // wrote whichever of those came in last.
                $lastAuthor = ($followupsCount === 0 && $tasksCount === 0)
                    ? Arr::first($requesterIds)
                    : ($lastInteractionAuthors[(string) $row['2']] ?? null);

                return [
                    'id' => $row['2'],
                    'title' => $this->decodeText((string) $row['1']),
                    'status' => (int) $row['12'],
                    'status_label' => self::STATUSES[(int) $row['12']] ?? 'Inconnu',
                    'category' => filled($row['7'] ?? null) ? $this->decodeText((string) $row['7']) : null,
                    'excerpt' => $this->excerpt($row['21'] ?? null),
                    'priority' => (int) $row['3'],
                    'priority_label' => self::PRIORITIES[(int) $row['3']] ?? 'Inconnue',
                    'interactions_count' => $followupsCount + $tasksCount,
                    'awaiting_technician' => $lastAuthor !== null && in_array((string) $lastAuthor, $requesterIds, true),
                    'technician' => collect($technicianIds)
                        ->map(fn ($id) => $technicianNames[$id] ?? null)
                        ->filter()
                        ->implode(', ') ?: null,
                    'date_mod' => $row['19'],
                    'url' => $this->ticketUrl((int) $row['2']),
                ];
            })->all();

            return [
                'tickets' => $tickets,
                'total' => (int) ($response->json('totalcount') ?? count($tickets)),
                'error' => null,
            ];
        });
    }

    /**
     * The search engine can count followups (option 27) and tasks (option 28)
     * but doesn't expose who wrote the most recent one of either — and
     * technicians in this GLPI instance sometimes reply via a task instead of
     * a followup, so both have to be checked. For every ticket that has at
     * least one of either, fetch its last followup AND its last task, then
     * keep whichever is more recent. Run all those lookups concurrently
     * (Http::pool) so an 8-ticket dashboard panel costs one round trip, not
     * up to sixteen sequential ones.
     *
     * @param  array<int, array<string, mixed>>  $rows
     * @return array<string, string> ticket id => author user id
     */
    protected function fetchLastInteractionAuthors(string $sessionToken, array $rows): array
    {
        $ticketIds = collect($rows)
            ->filter(fn (array $row) => (int) ($row['27'] ?? 0) > 0 || (int) ($row['28'] ?? 0) > 0)
            ->pluck('2')
            ->all();

        if (empty($ticketIds)) {
            return [];
        }

        $subItemParams = ['sort' => 'date', 'order' => 'DESC', 'range' => '0-0'];

        $responses = Http::pool(fn ($pool) => collect($ticketIds)->flatMap(fn ($ticketId) => [
            $pool->as("followup-{$ticketId}")->withHeaders($this->headers($sessionToken))
                ->get("{$this->baseUrl}/Ticket/{$ticketId}/ITILFollowup", $subItemParams),
            $pool->as("task-{$ticketId}")->withHeaders($this->headers($sessionToken))
                ->get("{$this->baseUrl}/Ticket/{$ticketId}/TicketTask", $subItemParams),
        ])->all());

        $latestPerTicket = [];

        foreach (['followup', 'task'] as $type) {
            foreach ($ticketIds as $ticketId) {
                $response = $responses["{$type}-{$ticketId}"] ?? null;

                if (! $response instanceof \Illuminate\Http\Client\Response || $response->failed()) {
                    continue;
                }

                $entry = $response->json('0');

                if (! isset($entry['users_id'], $entry['date'])) {
                    continue;
                }

                $ticketId = (string) $ticketId;
                $existing = $latestPerTicket[$ticketId] ?? null;

                if ($existing === null || $entry['date'] > $existing['date']) {
                    $latestPerTicket[$ticketId] = $entry;
                }
            }
        }

        return collect($latestPerTicket)->map(fn ($entry) => (string) $entry['users_id'])->all();
    }

    /**
     * Ticket search results only carry raw GLPI user IDs for the technician
     * fields (unlike single-value dropdowns such as category, these aren't
     * auto-resolved to a display name) — batch-resolve them by name in one
     * extra call within the same session.
     *
     * @param  Collection<int, int|string>  $userIds
     * @return array<string, string> id => "Firstname Lastname"
     */
    protected function resolveUserNames(string $sessionToken, Collection $userIds): array
    {
        if ($userIds->isEmpty()) {
            return [];
        }

        $response = Http::withHeaders($this->headers($sessionToken))
            ->get("{$this->baseUrl}/search/User", [
                'criteria' => $this->buildOrCriteria(2, $userIds->all()),
                'forcedisplay' => [2, 9, 34],
                'range' => '0-'.($userIds->count() - 1),
            ]);

        if ($response->failed()) {
            return [];
        }

        return collect($response->json('data') ?? [])
            ->mapWithKeys(function (array $row) {
                $name = trim(($row['9'] ?? '').' '.($row['34'] ?? ''));

                return [(string) $row['2'] => $name !== '' ? $name : null];
            })
            ->filter()
            ->all();
    }

    /**
     * Builds a GLPI search "criteria" array matching any of the given values
     * against a single field, e.g. field=2 equals 5 OR field=2 equals 9.
     */
    protected function buildOrCriteria(int $field, array $values): array
    {
        $criteria = [];

        foreach (array_values($values) as $index => $value) {
            $criteria[] = [
                ...($index > 0 ? ['link' => 'OR'] : []),
                'field' => $field,
                'searchtype' => 'equals',
                'value' => $value,
            ];
        }

        return $criteria;
    }

    /**
     * GLPI's ticket description comes back as HTML, itself HTML-entity-encoded
     * (e.g. "&#60;p&#62;" for "<p>"). Strip markup and trim to a short
     * plain-text preview.
     */
    protected function excerpt(?string $html, int $length = 160): ?string
    {
        if (blank($html)) {
            return null;
        }

        $text = strip_tags($this->decodeText($html));
        $text = trim(preg_replace('/\s+/', ' ', $text));

        return $text === '' ? null : \Illuminate\Support\Str::limit($text, $length);
    }

    /**
     * Some GLPI fields (rich-text description, titles typed via a rich editor)
     * are HTML-entity-encoded twice over: once because the stored content is
     * itself escaped HTML (e.g. a literal "&amp;"), and again because the
     * search API encodes the whole field for its JSON response. A single
     * decode leaves artifacts like "&amp;" in the output, so decode twice —
     * harmless no-op on text that was only encoded once.
     */
    protected function decodeText(string $value): string
    {
        return html_entity_decode(html_entity_decode($value, ENT_QUOTES), ENT_QUOTES);
    }

    /**
     * Opens a GLPI session, runs the callback with the session token, and
     * always closes the session afterwards — GLPI has no stateless auth mode
     * for the REST API, so every call pays this round trip.
     */
    protected function withSession(\Closure $callback): mixed
    {
        $session = Http::withHeaders([
            'App-Token' => $this->appToken,
            'Authorization' => 'user_token '.$this->userToken,
        ])->get("{$this->baseUrl}/initSession");

        if ($session->failed()) {
            throw new GlpiException("Échec de connexion à GLPI (HTTP {$session->status()}).");
        }

        $sessionToken = $session->json('session_token');

        try {
            return $callback($sessionToken);
        } finally {
            Http::withHeaders($this->headers($sessionToken))->get("{$this->baseUrl}/killSession");
        }
    }

    /**
     * @return array<string, string>
     */
    protected function headers(string $sessionToken): array
    {
        return [
            'App-Token' => $this->appToken,
            'Session-Token' => $sessionToken,
        ];
    }
}