<?php
// SPDX-License-Identifier: GPL-3.0-or-later
declare(strict_types=1);

namespace Aiwend\Usage;

use Aiwend\Db\Connection;

/**
 * Aggregate view of the separately accounted embedding budget (owner decision D1), for a future administration screen. Indexing
 * reserves against the site's "embedding" bucket only, so it can neither consume nor be hidden inside the chat budget; reservations
 * that touch only that bucket are summarised here and excluded from Ledger::usageSummary()/breakdown().
 *
 * Units are Aiwend's accounting units (provider-reported tokens where the provider reported them), NOT money: there is no price
 * table and no currency conversion anywhere. Estimated and held amounts are reported separately from provider-reported ones so an
 * estimate is never presented as confirmed usage. Nothing here exposes request ids, credentials or content. Query embeddings are
 * charged to the chat buckets (site + session) and therefore appear in the chat usage, not here.
 */
final class EmbeddingUsage
{
    public const BUCKET = 'embedding';
    /** The exact bucket list of an indexing reservation, as the ledger stores it. */
    public const BUCKETS_JSON = '["embedding"]';

    public function __construct(private Connection $db)
    {
    }

    /**
     * @return array{unit:string, money:bool, budget:?array{limit:int, reserved:int, spent:int, available:int}, confirmed:array{requests:int, units:int},
     *   estimated_unconfirmed:array{requests:int, units:int}, administrator_entered:array{requests:int, units:int}, in_progress:array{requests:int, units:int},
     *   uncertain:array{requests:int, units:int}, not_dispatched:array{requests:int, units:int}, released:array{requests:int, units:int}}
     */
    public function summary(int $siteId): array
    {
        $zero = ['requests' => 0, 'units' => 0];
        $out = ['unit' => 'tokens', 'money' => false, 'budget' => null, 'confirmed' => $zero, 'estimated_unconfirmed' => $zero, 'administrator_entered' => $zero,
            'in_progress' => $zero, 'uncertain' => $zero, 'not_dispatched' => $zero, 'released' => $zero];
        $b = $this->db->selectOne('SELECT limit_units, reserved_units, spent_units FROM {budgets} WHERE site_id = ? AND bucket = ?', [$siteId, self::BUCKET]);
        if ($b !== null) {
            $limit = (int) $b['limit_units'];
            $out['budget'] = ['limit' => $limit, 'reserved' => (int) $b['reserved_units'], 'spent' => (int) $b['spent_units'], 'available' => $limit - (int) $b['reserved_units'] - (int) $b['spent_units']];
        }
        $rows = $this->db->select(
            'SELECT state, usage_basis, COUNT(*) AS n, SUM(reserved_units) AS reserved, SUM(COALESCE(settled_units, 0)) AS settled
             FROM {reservations} WHERE site_id = ? AND buckets = ? GROUP BY state, usage_basis',
            [$siteId, self::BUCKETS_JSON]
        );
        foreach ($rows as $row) {
            $basis = (string) ($row['usage_basis'] ?? '');
            [$key, $units] = match ((string) $row['state']) {
                Reservation::RESERVED, Reservation::DISPATCHED => ['in_progress', (int) $row['reserved']],
                Reservation::UNCERTAIN => ['uncertain', (int) $row['reserved']],
                Reservation::RELEASED => ['released', (int) $row['reserved']],
                default => match ($basis) {
                    Reservation::BASIS_NOT_DISPATCHED => ['not_dispatched', 0],
                    Reservation::BASIS_ESTIMATED => ['estimated_unconfirmed', (int) $row['settled']],
                    Reservation::BASIS_ADMIN_ENTERED => ['administrator_entered', (int) $row['settled']],
                    default => ['confirmed', (int) $row['settled']],
                },
            };
            $out[$key]['requests'] += (int) $row['n'];
            $out[$key]['units'] += $units;
        }
        return $out;
    }
}