<?php

namespace App\Services;

use App\Models\Automation;
use App\Models\Entity;
use Illuminate\Support\Carbon;
use Illuminate\Support\Facades\Log;

/**
 * Minimal trigger → condition → action engine (handoff §13.6). Every automation carries a
 * cooldown (motion sensors flood the queue otherwise) and can run in dry-run mode, which
 * logs the action instead of switching — never develop against the live home (H5).
 */
class AutomationEngine
{
    public function __construct(private readonly DeviceCommandService $commands) {}

    /** Evaluate state-change automations after a device entity changed. */
    public function onStateChange(string $deviceUuid, string $entityKey, array $state): void
    {
        Automation::where('enabled', true)->where('trigger_type', 'state_change')->get()
            ->each(function (Automation $automation) use ($deviceUuid, $entityKey, $state) {
                if ($this->matchesStateTrigger($automation, $deviceUuid, $entityKey, $state)) {
                    $this->maybeRun($automation);
                }
            });
    }

    /** Evaluate time-based automations (called every minute by the scheduler). */
    public function tick(): void
    {
        $hhmm = now()->format('H:i');

        Automation::where('enabled', true)->where('trigger_type', 'time')->get()
            ->each(function (Automation $automation) use ($hhmm) {
                if (data_get($automation->trigger_config, 'at') === $hhmm) {
                    $this->maybeRun($automation);
                }
            });
    }

    private function matchesStateTrigger(Automation $automation, string $deviceUuid, string $entityKey, array $state): bool
    {
        $cfg = $automation->trigger_config ?? [];

        if (($cfg['device'] ?? null) !== $deviceUuid || ($cfg['entity_key'] ?? null) !== $entityKey) {
            return false;
        }

        $field = $cfg['field'] ?? 'on';

        return array_key_exists($field, $state) && $state[$field] == ($cfg['equals'] ?? true);
    }

    private function maybeRun(Automation $automation): void
    {
        // Conditions gate the actions but must not touch the cooldown clock — a rule whose
        // conditions are currently false should stay armed for its next legitimate trigger.
        if (! $this->conditionsMet($automation)) {
            return;
        }

        // Atomically claim the cooldown window: concurrent queue workers processing a burst of
        // state changes would otherwise all read the same stale last_triggered_at and each fire
        // the action. The conditional UPDATE lets exactly one worker win the race (H5).
        if (! $this->claimCooldown($automation)) {
            return;
        }

        foreach ($automation->actions ?? [] as $action) {
            $this->runAction($automation, $action);
        }
    }

    /** Every stored condition ({device, entity_key, field, equals}) must match current state (AND). */
    private function conditionsMet(Automation $automation): bool
    {
        foreach ($automation->conditions ?? [] as $condition) {
            $entity = $this->findEntity($condition['device'] ?? null, $condition['entity_key'] ?? null);
            $state = $entity?->state?->state ?? [];
            $field = $condition['field'] ?? 'on';

            if (! array_key_exists($field, $state) || $state[$field] != ($condition['equals'] ?? true)) {
                return false;
            }
        }

        return true;
    }

    /** Reserve the run atomically; returns false when the cooldown is still active. */
    private function claimCooldown(Automation $automation): bool
    {
        $now = Carbon::instance(now());

        $query = Automation::query()->whereKey($automation->getKey());

        if ($automation->cooldown_seconds > 0) {
            $threshold = $now->copy()->subSeconds($automation->cooldown_seconds);
            $query->where(fn ($q) => $q
                ->whereNull('last_triggered_at')
                ->orWhere('last_triggered_at', '<=', $threshold));
        }

        $claimed = $query->update(['last_triggered_at' => $now]) > 0;

        if ($claimed) {
            $automation->last_triggered_at = $now;
        }

        return $claimed;
    }

    private function runAction(Automation $automation, array $action): void
    {
        $type = $action['type'] ?? null;

        if ($type === 'switch') {
            $entity = $this->findEntity($action['device'] ?? null, $action['entity_key'] ?? null);

            if ($entity === null) {
                return;
            }

            if ($automation->dry_run) {
                Log::info("[automation dry-run] {$automation->name}: switch {$entity->key}", $action);

                return;
            }

            $this->commands->setOn($entity, (bool) ($action['on'] ?? true), 'automation');
        } elseif ($type === 'notify') {
            $message = $action['message'] ?? '';
            Log::info('[automation'.($automation->dry_run ? ' dry-run' : '')."] {$automation->name}: ".$message);

            // Also e-mail it if the SMTP add-on is set up and automation notifications are enabled.
            if (! $automation->dry_run) {
                app(\App\Services\NotificationService::class)->notify('automation', $automation->name, $message);
            }
        }
    }

    private function findEntity(?string $deviceUuid, ?string $entityKey): ?Entity
    {
        if ($deviceUuid === null || $entityKey === null) {
            return null;
        }

        return Entity::query()
            ->whereHas('device', fn ($q) => $q->where('uuid', $deviceUuid))
            ->where('key', $entityKey)
            ->with('device', 'state')->first();
    }
}