<?php
declare(strict_types=1);

namespace App;

use DateTimeImmutable;
use DateTimeZone;

final class ModuleCronScheduler
{
    public function __construct(
        private ModuleManager $modules,
        private ?\PDO $pdo
    ) {
    }

    public function definitions(string $moduleName): array
    {
        $module = $this->modules->get($moduleName);
        $tasks = is_array($module['scheduler_jobs'] ?? null) ? $module['scheduler_jobs'] : (is_array($module['cron_tasks'] ?? null) ? $module['cron_tasks'] : []);
        $definitions = [];

        foreach ($tasks as $task) {
            if (!is_array($task)) {
                continue;
            }

            $name = trim((string) ($task['name'] ?? ''));
            $callback = trim((string) ($task['callback'] ?? ''));
            if ($name === '' || $callback === '') {
                continue;
            }

            $definitions[$name] = [
                'name' => $name,
                'label' => trim((string) ($task['label'] ?? $name)),
                'callback' => $callback,
                'mode' => in_array((string) ($task['mode'] ?? 'single'), ['single', 'multi'], true) ? (string) ($task['mode'] ?? 'single') : 'single',
                'default_enabled' => array_key_exists('default_enabled', $task) ? (bool) $task['default_enabled'] : false,
                'default_cron' => trim((string) ($task['default_cron'] ?? '0 * * * *')),
                'default_timezone' => trim((string) ($task['default_timezone'] ?? 'UTC')) ?: 'UTC',
                'timezone_setting' => trim((string) ($task['timezone_setting'] ?? '')),
                'lock_minutes' => max(1, (int) ($task['lock_minutes'] ?? 10)),
                'builder' => is_array($task['builder'] ?? null) ? $task['builder'] : [],
                'help' => trim((string) ($task['help'] ?? '')),
            ];
        }

        return $definitions;
    }

    public function statuses(string $moduleName): array
    {
        $definitions = $this->definitions($moduleName);
        if ($definitions === []) {
            return [];
        }

        $settings = $this->modules->settings($moduleName);
        $states = $this->fetchStates($moduleName);
        $nowUtc = new DateTimeImmutable('now', new DateTimeZone('UTC'));
        $statuses = [];

        foreach ($definitions as $name => $definition) {
            foreach ($this->jobConfigs($definition, $settings) as $entryIndex => $config) {
                $stateKey = $this->stateKey($name, $entryIndex);
                $state = $states[$stateKey] ?? [];
                $timezone = $this->safeTimezone((string) ($config['timezone'] ?? 'UTC'));
                $expression = trim((string) ($config['cron_expression'] ?? ''));
                $isLocked = $this->isLockActive($state, $nowUtc->getTimestamp());
                $parseError = null;
                $previousDueUtc = null;
                $nextDueUtc = null;
                $isDue = false;

                try {
                    $cron = CronExpression::parse($expression);
                    if (!empty($config['enabled'])) {
                        $previousDueUtc = $cron->previousRun($nowUtc, $timezone);
                        $lastScheduledFor = $this->parseUtc((string) ($state['last_scheduled_for'] ?? ''));
                        $isDue = !$isLocked
                            && $previousDueUtc instanceof DateTimeImmutable
                            && ($lastScheduledFor === null || $previousDueUtc > $lastScheduledFor);
                        $nextDueUtc = $isDue
                            ? $previousDueUtc
                            : $cron->nextRun($nowUtc, $timezone);
                    }
                } catch (\Throwable $exception) {
                    $parseError = $exception->getMessage();
                }

                $statuses[] = $definition + [
                    'job_name' => $name,
                    'entry_index' => $entryIndex,
                    'state_key' => $stateKey,
                    'config' => $config,
                    'state' => $state,
                    'last_started_at_local' => ($this->parseUtc((string) ($state['last_started_at'] ?? '')))?->setTimezone($timezone)->format('Y-m-d H:i:s'),
                    'last_success_at_local' => ($this->parseUtc((string) ($state['last_success_at'] ?? '')))?->setTimezone($timezone)->format('Y-m-d H:i:s'),
                    'enabled' => !empty($config['enabled']),
                    'cron_expression' => $expression,
                    'timezone' => $timezone->getName(),
                    'is_due' => $isDue,
                    'is_locked' => $isLocked,
                    'parse_error' => $parseError,
                    'previous_due_at' => $previousDueUtc?->format('Y-m-d H:i:s'),
                    'next_due_at' => $nextDueUtc?->format('Y-m-d H:i:s'),
                    'previous_due_at_local' => $previousDueUtc?->setTimezone($timezone)->format('Y-m-d H:i:s'),
                    'next_due_at_local' => $nextDueUtc?->setTimezone($timezone)->format('Y-m-d H:i:s'),
                ];
            }
        }

        return $statuses;
    }

    public function runDue(string $moduleName): array
    {
        $results = [];
        foreach ($this->statuses($moduleName) as $task) {
            if (empty($task['enabled']) || empty($task['is_due']) || !empty($task['parse_error'])) {
                continue;
            }

            if (!$this->modules->hasFunction($moduleName, (string) $task['callback'])) {
                $results[] = [
                    'task' => $task['job_name'],
                    'entry_index' => $task['entry_index'],
                    'ok' => false,
                    'message' => 'Callback nicht registriert.',
                ];
                continue;
            }

            if (!$this->acquireLock($moduleName, (string) $task['state_key'], (int) $task['lock_minutes'])) {
                continue;
            }

            $startedAt = gmdate('Y-m-d H:i:s');
            $scheduledForUtc = trim((string) ($task['previous_due_at'] ?? ''));
            $timezone = $this->safeTimezone((string) ($task['timezone'] ?? 'UTC'));

            $this->persistState($moduleName, (string) $task['state_key'], [
                'last_started_at' => $startedAt,
                'last_status' => 'running',
                'last_message' => 'Cron-Lauf gestartet.',
            ]);

            try {
                $result = $this->modules->call($moduleName, (string) $task['callback'], [
                    'task' => $task,
                    'trigger' => 'cron_runner',
                    'started_at' => $startedAt,
                    'scheduled_for_utc' => $scheduledForUtc,
                    'scheduled_for_local' => $scheduledForUtc !== ''
                        ? $this->parseUtc($scheduledForUtc)?->setTimezone($timezone)?->format('Y-m-d H:i:s')
                        : null,
                    'timezone' => $timezone->getName(),
                ]);

                $ok = !is_array($result) || !array_key_exists('ok', $result) || !empty($result['ok']);
                $skipped = is_array($result) && !empty($result['skipped']);
                $message = is_array($result) ? trim((string) ($result['message'] ?? '')) : '';
                $finishedAt = gmdate('Y-m-d H:i:s');

                $payload = [
                    'last_finished_at' => $finishedAt,
                    'last_status' => $skipped ? 'skipped' : ($ok ? 'success' : 'error'),
                    'last_message' => $message,
                    'lock_until' => null,
                    'last_scheduled_for' => $scheduledForUtc !== '' ? $scheduledForUtc : null,
                ];
                if ($ok && !$skipped) {
                    $payload['last_success_at'] = $finishedAt;
                }
                $this->persistState($moduleName, (string) $task['state_key'], $payload);

                $results[] = [
                    'task' => $task['job_name'],
                    'entry_index' => $task['entry_index'],
                    'ok' => $ok,
                    'message' => $message,
                ];
            } catch (\Throwable $e) {
                $finishedAt = gmdate('Y-m-d H:i:s');
                $this->persistState($moduleName, (string) $task['state_key'], [
                    'last_finished_at' => $finishedAt,
                    'last_status' => 'error',
                    'last_message' => $e->getMessage(),
                    'lock_until' => null,
                    'last_scheduled_for' => $scheduledForUtc !== '' ? $scheduledForUtc : null,
                ]);
                $results[] = [
                    'task' => $task['job_name'],
                    'entry_index' => $task['entry_index'],
                    'ok' => false,
                    'message' => $e->getMessage(),
                ];
            }
        }

        return $results;
    }

    private function jobConfigs(array $definition, array $settings): array
    {
        $jobs = is_array($settings['scheduler_jobs'] ?? null)
            ? $settings['scheduler_jobs']
            : (is_array($settings['cron_jobs'] ?? null) ? $settings['cron_jobs'] : []);
        $jobExists = array_key_exists($definition['name'], $jobs) && is_array($jobs[$definition['name']] ?? null);
        $job = $jobExists ? $jobs[$definition['name']] : [];
        $timezoneSetting = trim((string) ($definition['timezone_setting'] ?? ''));
        $fallbackTimezone = $timezoneSetting !== '' ? trim((string) ($settings[$timezoneSetting] ?? '')) : '';
        $defaultEntry = [
            'enabled' => (bool) $definition['default_enabled'],
            'cron_expression' => trim((string) ($definition['default_cron'] ?? '0 * * * *')),
            'timezone' => trim((string) ($fallbackTimezone !== '' ? $fallbackTimezone : ($definition['default_timezone'] ?? 'UTC'))),
            'builder' => [],
        ];

        $entries = is_array($job['entries'] ?? null) ? $job['entries'] : [];
        if (!$jobExists && $entries === []) {
            $legacyEntry = [];
            foreach (['enabled', 'cron_expression', 'timezone', 'builder'] as $field) {
                if (array_key_exists($field, $job)) {
                    $legacyEntry[$field] = $job[$field];
                }
            }
            $entries = [$legacyEntry !== [] ? $legacyEntry : $defaultEntry];
        }

        if ($jobExists && $entries === [] && ($definition['mode'] ?? 'single') === 'multi') {
            return [];
        }

        $result = [];
        foreach (array_values($entries) as $entry) {
            if (!is_array($entry)) {
                continue;
            }
            $result[] = [
                'enabled' => array_key_exists('enabled', $entry) ? $this->settingBool($entry['enabled'], (bool) $defaultEntry['enabled']) : (bool) $defaultEntry['enabled'],
                'cron_expression' => trim((string) ($entry['cron_expression'] ?? $defaultEntry['cron_expression'])),
                'timezone' => trim((string) ($entry['timezone'] ?? $defaultEntry['timezone'])),
                'builder' => is_array($entry['builder'] ?? null) ? $entry['builder'] : [],
            ];
        }

        if ($result === []) {
            $result[] = $defaultEntry;
        }

        if (($definition['mode'] ?? 'single') !== 'multi') {
            return [0 => $result[0]];
        }

        return $result;
    }

    private function stateKey(string $jobName, int $entryIndex): string
    {
        return $jobName . '#' . $entryIndex;
    }

    private function fetchStates(string $moduleName): array
    {
        if (!$this->pdo) {
            return [];
        }

        $stmt = $this->pdo->prepare(
            'SELECT *
             FROM nexus_module_cron_runs
             WHERE module_name = :module_name'
        );
        $stmt->execute(['module_name' => $moduleName]);

        $states = [];
        foreach ($stmt->fetchAll(\PDO::FETCH_ASSOC) ?: [] as $row) {
            $name = trim((string) ($row['job_name'] ?? ''));
            if ($name !== '') {
                $states[$name] = $row;
            }
        }

        return $states;
    }

    private function acquireLock(string $moduleName, string $jobName, int $lockMinutes): bool
    {
        if (!$this->pdo) {
            return true;
        }

        $states = $this->fetchStates($moduleName);
        $state = $states[$jobName] ?? [];
        if ($this->isLockActive($state, time())) {
            return false;
        }

        $lockUntil = gmdate('Y-m-d H:i:s', time() + ($lockMinutes * 60));
        $this->persistState($moduleName, $jobName, [
            'lock_until' => $lockUntil,
        ]);

        return true;
    }

    private function persistState(string $moduleName, string $jobName, array $values): void
    {
        if (!$this->pdo) {
            return;
        }

        $current = $this->fetchStates($moduleName)[$jobName] ?? [];
        $payload = array_merge($current, $values, [
            'module_name' => $moduleName,
            'job_name' => $jobName,
            'updated_at' => gmdate('Y-m-d H:i:s'),
        ]);

        $params = [
            'module_name' => $moduleName,
            'job_name' => $jobName,
            'last_scheduled_for' => $this->nullOrString($payload['last_scheduled_for'] ?? null),
            'last_started_at' => $this->nullOrString($payload['last_started_at'] ?? null),
            'last_finished_at' => $this->nullOrString($payload['last_finished_at'] ?? null),
            'last_success_at' => $this->nullOrString($payload['last_success_at'] ?? null),
            'last_status' => $this->nullOrString($payload['last_status'] ?? null),
            'last_message' => $this->nullOrString($payload['last_message'] ?? null),
            'lock_until' => $this->nullOrString($payload['lock_until'] ?? null),
            'updated_at' => $payload['updated_at'],
        ];

        $updateStmt = $this->pdo->prepare(
            'UPDATE nexus_module_cron_runs
             SET last_scheduled_for = :last_scheduled_for,
                 last_started_at = :last_started_at,
                 last_finished_at = :last_finished_at,
                 last_success_at = :last_success_at,
                 last_status = :last_status,
                 last_message = :last_message,
                 lock_until = :lock_until,
                 updated_at = :updated_at
             WHERE module_name = :module_name
               AND job_name = :job_name'
        );
        $updateStmt->execute($params);
        if ($updateStmt->rowCount() > 0) {
            return;
        }

        $insertStmt = $this->pdo->prepare(
            'INSERT INTO nexus_module_cron_runs (
                module_name,
                job_name,
                last_scheduled_for,
                last_started_at,
                last_finished_at,
                last_success_at,
                last_status,
                last_message,
                lock_until,
                updated_at
            ) VALUES (
                :module_name,
                :job_name,
                :last_scheduled_for,
                :last_started_at,
                :last_finished_at,
                :last_success_at,
                :last_status,
                :last_message,
                :lock_until,
                :updated_at
            )'
        );
        $insertStmt->execute($params);
    }

    private function nullOrString(mixed $value): ?string
    {
        $value = trim((string) $value);
        return $value !== '' ? $value : null;
    }

    private function settingBool(mixed $value, bool $default): bool
    {
        if ($value === null || $value === '') {
            return $default;
        }
        return in_array((string) $value, ['1', 'true', 'yes', 'on'], true);
    }

    private function isLockActive(array $state, int $nowTs): bool
    {
        $lockUntil = trim((string) ($state['lock_until'] ?? ''));
        if ($lockUntil === '') {
            return false;
        }

        $lockTs = strtotime($lockUntil);
        return $lockTs !== false && $lockTs > $nowTs;
    }

    private function parseUtc(string $value): ?DateTimeImmutable
    {
        $value = trim($value);
        if ($value === '') {
            return null;
        }

        try {
            return new DateTimeImmutable($value, new DateTimeZone('UTC'));
        } catch (\Throwable) {
            return null;
        }
    }

    private function safeTimezone(string $timezone): DateTimeZone
    {
        try {
            return new DateTimeZone(trim($timezone) !== '' ? trim($timezone) : 'UTC');
        } catch (\Throwable) {
            return new DateTimeZone('UTC');
        }
    }
}