<?php

declare(strict_types=1);

namespace Sarcio\WordPress\Assistant;

use Sarcio\WordPress\Account;
use Sarcio\WordPress\Options;

/**
 * One turn of the conversation, sent to Sarcio as the signed-in member. The
 * service holds no state: every turn carries the site, what the member may
 * do here and the conversation so far, and answers with text and the calls it
 * wants made. Nothing runs on this site unless the plugin runs it. When the
 * conversation outgrows what a turn carries, the oldest part is summarised
 * first and the summary travels with every later turn.
 */
final class Client
{
    private const TIMEOUT_SEC = 120;

    /**
     * @param array<int,mixed> $messages
     * @param array<int,array<string,mixed>>|null $abilities
     * @return array{text?:string,calls?:array<int,array<string,mixed>>,compaction?:array{summary:string,keep:int},reconnect?:bool,error?:string}
     */
    public static function turn(int $userId, array $messages, string $summary = '', ?array $abilities = null): array
    {
        $siteKey = (string) Options::get('site_key');
        if ($siteKey === '') {
            return ['error' => __('Connect this site to Sarcio first.', 'sarcio')];
        }
        $token = Account::accessToken($userId);
        if (!isset($token['access'])) {
            return $token;
        }
        $summary = mb_substr($summary, 0, Transcript::MAX_SUMMARY_CHARS);
        $compaction = null;
        if (count($messages) > Transcript::MAX_MESSAGES) {
            [$old, $keep] = Transcript::split($messages);
            $summarised = self::summarise($userId, $token['access'], $siteKey, $summary, $old);
            if ($summarised !== null) {
                $summary = $summarised;
                $messages = $keep;
                $compaction = ['keep' => count($keep), 'summary' => $summary];
            }
        }
        $body = (string) wp_json_encode(array_filter([
            'abilities' => $abilities ?? Catalog::forCurrentUser(),
            'context' => SiteAbilities::context(),
            'messages' => Transcript::prepare($messages, $summary !== ''),
            'site' => $siteKey,
            'summary' => $summary !== '' ? $summary : null,
        ], static fn ($value): bool => $value !== null));
        $response = self::send($userId, $token['access'], '/api/assistant/turn', $body);
        if (isset($response['reconnect'])) {
            return $response;
        }
        $result = self::interpret($response);
        if ($compaction !== null && !isset($result['error'])) {
            $result['compaction'] = $compaction;
        }
        return $result;
    }

    /**
     * Asks Sarcio for a plain-words summary of the oldest part of the
     * conversation, folded into the summary so far. Null when it could not be
     * had, in which case the turn trims the old way.
     *
     * @param array<int,mixed> $messages
     */
    private static function summarise(int $userId, string $access, string $siteKey, string $summary, array $messages): ?string
    {
        $prepared = Transcript::prepare($messages, true);
        if ($prepared === []) {
            return null;
        }
        $body = (string) wp_json_encode(array_filter([
            'messages' => $prepared,
            'site' => $siteKey,
            'summary' => $summary !== '' ? $summary : null,
        ], static fn ($value): bool => $value !== null));
        $response = self::send($userId, $access, '/api/assistant/summary', $body);
        if (isset($response['reconnect']) || !in_array($response['status'] ?? 0, [200, 201], true)) {
            return null;
        }
        $text = is_array($response['body']) && is_string($response['body']['summary'] ?? null) ? trim($response['body']['summary']) : '';
        return $text === '' ? null : mb_substr($text, 0, Transcript::MAX_SUMMARY_CHARS);
    }

    /**
     * Posts as the member, refreshing the sign-in once on a 401.
     *
     * @return array{status:int,body:mixed}|array{reconnect:true}
     */
    private static function send(int $userId, string $access, string $path, string $body): array
    {
        $response = self::post($access, $path, $body);
        if (($response['status'] ?? 0) === 401) {
            $token = Account::accessToken($userId, true);
            if (!isset($token['access'])) {
                return ['reconnect' => true];
            }
            $response = self::post($token['access'], $path, $body);
            if (($response['status'] ?? 0) === 401) {
                Account::forget($userId);
                return ['reconnect' => true];
            }
        }
        return $response;
    }

    /** @return array{status:int,body:mixed} */
    private static function post(string $access, string $path, string $body): array
    {
        $response = wp_remote_post(Options::apiUrl() . $path, [
            'body' => $body,
            'headers' => [
                'Authorization' => 'Bearer ' . $access,
                'Content-Type' => 'application/json',
            ],
            'redirection' => 0,
            'timeout' => self::TIMEOUT_SEC,
        ]);
        if (is_wp_error($response)) {
            return ['body' => null, 'status' => 0];
        }
        return [
            'body' => json_decode((string) wp_remote_retrieve_body($response), true),
            'status' => (int) wp_remote_retrieve_response_code($response),
        ];
    }

    /**
     * @param array{status:int,body:mixed} $response
     * @return array{text?:string,calls?:array<int,array<string,mixed>>,error?:string}
     */
    private static function interpret(array $response): array
    {
        $status = $response['status'];
        $body = is_array($response['body']) ? $response['body'] : [];
        $message = is_string($body['message'] ?? null) ? sanitize_text_field($body['message']) : '';
        if ($status === 200 || $status === 201) {
            $calls = [];
            foreach ((array) ($body['calls'] ?? []) as $call) {
                if (is_array($call) && is_string($call['ability'] ?? null)) {
                    $calls[] = [
                        'ability' => sanitize_text_field($call['ability']),
                        'args' => is_array($call['args'] ?? null) && $call['args'] !== [] ? $call['args'] : new \stdClass(),
                        'id' => is_string($call['id'] ?? null) ? sanitize_text_field(mb_substr($call['id'], 0, 40)) : '',
                        'why' => is_string($call['why'] ?? null) ? sanitize_text_field(mb_substr($call['why'], 0, 500)) : '',
                    ];
                }
            }
            return ['calls' => $calls, 'text' => is_string($body['text'] ?? null) ? mb_substr($body['text'], 0, Transcript::MAX_TEXT_CHARS) : ''];
        }
        return ['error' => match ($status) {
            0 => __('Could not reach Sarcio. Check your connection and try again.', 'sarcio'),
            402 => $message !== '' ? $message : __('This workspace has used its AI credits for the month. Add credits or wait for the next month.', 'sarcio'),
            403 => $message !== '' ? $message : __('Sarcio did not allow that for this site.', 'sarcio'),
            413 => __('This conversation is too long. Start a new one.', 'sarcio'),
            429 => __('Too many requests at once. Wait a moment and try again.', 'sarcio'),
            503 => __('AI is not turned on for this Sarcio workspace.', 'sarcio'),
            422 => $message !== '' ? $message : __('The assistant could not answer that. Try saying it another way.', 'sarcio'),
            default => __('Sarcio could not answer right now. Try again in a moment.', 'sarcio'),
        }, 'status' => $status];
    }
}