<?php

namespace App\Services\Forecasting;

use App\Models\BrentPrice;
use App\Models\LlmOverlay;
use App\Models\VolatilityRegime;
use App\Services\ApiLogger;
use Carbon\CarbonInterface;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\Http;
use Illuminate\Support\Facades\Log;
use Throwable;

/**
 * Layer 4 — daily news-aware overlay on the calibrated ridge forecast.
 *
 * Calls Anthropic Haiku with the web_search tool, then forces a
 * submit_overlay tool call to get structured output. Cites events with
 * URLs; URLs are verified before storing. Empty citations → rejection.
 *
 * Read-only with respect to the volatility flag — Layer 4 writes its
 * `llm_overlays` row; Layer 5's hourly cron picks it up and decides
 * whether to flip the regime.
 */
final class LlmOverlayService
{
    private const string URL = 'https://api.anthropic.com/v1/messages';

    private const int CONFIDENCE_CAP = 75;

    private const int COOLDOWN_HOURS = 4;

    public function __construct(
        private readonly ApiLogger $apiLogger,
        private readonly WeeklyForecastService $weeklyForecast,
    ) {}

    /**
     * Run an overlay generation. $eventDriven=true respects the 4-hour
     * cooldown; the daily 07:00 cron passes false to always run.
     */
    public function run(bool $eventDriven = false): ?LlmOverlay
    {
        if ($this->apiKey() === null) {
            Log::info('LlmOverlayService: no ANTHROPIC_API_KEY, skipping');

            return null;
        }

        if ($eventDriven && $this->onCooldown()) {
            return null;
        }

        $forecast = $this->weeklyForecast->currentForecast();
        $context = $this->buildContext($forecast);

        $rawResult = $this->callAnthropic($context);
        if ($rawResult === null) {
            return null;
        }

        $verifiedEvents = $this->verifyCitedUrls($rawResult['events_cited'] ?? []);
        if ($verifiedEvents === []) {
            Log::warning('LlmOverlayService: no verified citations, rejecting overlay');

            return null;
        }

        $confidence = max(0, min(self::CONFIDENCE_CAP, (int) ($rawResult['confidence'] ?? 0)));
        $direction = $rawResult['direction'] ?? 'flat';
        $agreesWithRidge = $direction === $this->ridgeDirection($forecast['predicted_direction']);

        return LlmOverlay::query()->create([
            'ran_at' => now(),
            'forecast_for_week' => $this->upcomingMondayDateString(),
            'direction' => $direction,
            'confidence' => $confidence,
            'reasoning' => (string) ($rawResult['reasoning_short'] ?? ''),
            'events_json' => $verifiedEvents,
            'agrees_with_ridge' => $agreesWithRidge,
            'major_impact_event' => (bool) ($rawResult['major_impact_event'] ?? false),
            'volatility_flag_on' => VolatilityRegime::currentlyActive() !== null,
            'search_used' => true,
        ]);
    }

    private function onCooldown(): bool
    {
        $latest = LlmOverlay::query()->orderByDesc('ran_at')->first();

        return $latest !== null
            && $latest->ran_at->greaterThanOrEqualTo(now()->subHours(self::COOLDOWN_HOURS));
    }

    /** @return array<string, mixed> */
    private function buildContext(array $forecast): array
    {
        $ulspWeekly = DB::table('weekly_pump_prices')
            ->orderByDesc('date')
            ->limit(8)
            ->get(['date', 'ulsp_pence'])
            ->reverse()
            ->map(fn ($r): array => ['date' => (string) $r->date, 'ulsp_pence' => round((int) $r->ulsp_pence / 100, 1)])
            ->values()
            ->all();

        $brentRecent = BrentPrice::query()
            ->orderByDesc('date')
            ->limit(14)
            ->get(['date', 'price_usd'])
            ->reverse()
            ->map(fn (BrentPrice $r): array => ['date' => (string) $r->date->toDateString(), 'price_usd' => (float) $r->price_usd])
            ->values()
            ->all();

        return [
            'ulsp_recent_8_weeks' => $ulspWeekly,
            'brent_recent_14_days' => $brentRecent,
            'ridge_model_says' => [
                'direction' => $forecast['predicted_direction'] ?? 'stable',
                'confidence' => $forecast['confidence_score'] ?? 0,
                'magnitude_pence' => $forecast['predicted_change_pence'] ?? 0,
            ],
        ];
    }

    /** @return array<string, mixed>|null */
    private function callAnthropic(array $context): ?array
    {
        $messages = [['role' => 'user', 'content' => $this->prompt($context)]];

        try {
            // Phase 1: web search loop
            for ($i = 0, $response = null; $i < 5; $i++) {
                $response = $this->apiLogger->send('anthropic', 'POST', self::URL, fn () => Http::timeout(45)
                    ->withHeaders($this->headers())
                    ->post(self::URL, [
                        'model' => config('services.anthropic.model', 'claude-haiku-4-5-20251001'),
                        'max_tokens' => 1024,
                        'tools' => [['type' => 'web_search_20250305', 'name' => 'web_search']],
                        'messages' => $messages,
                    ]));

                if (! $response->successful()) {
                    Log::error('LlmOverlayService: search request failed', ['status' => $response->status()]);

                    return null;
                }

                if ($response->json('stop_reason') !== 'pause_turn') {
                    break;
                }

                $messages[] = ['role' => 'assistant', 'content' => $response->json('content')];
            }

            $messages[] = ['role' => 'assistant', 'content' => $response->json('content')];
            $messages[] = ['role' => 'user', 'content' => 'Now submit your overlay using the submit_overlay tool. Cite at least one event with a URL.'];

            // Phase 2: forced structured output
            $submitResponse = $this->apiLogger->send('anthropic', 'POST', self::URL, fn () => Http::timeout(20)
                ->withHeaders($this->headers())
                ->post(self::URL, [
                    'model' => config('services.anthropic.model', 'claude-haiku-4-5-20251001'),
                    'max_tokens' => 512,
                    'tools' => [$this->submitOverlayTool()],
                    'tool_choice' => ['type' => 'tool', 'name' => 'submit_overlay'],
                    'messages' => $messages,
                ]));

            if (! $submitResponse->successful()) {
                Log::error('LlmOverlayService: submit request failed', ['status' => $submitResponse->status()]);

                return null;
            }

            return $this->extractToolInput($submitResponse->json('content') ?? []);
        } catch (Throwable $e) {
            Log::error('LlmOverlayService: callAnthropic failed', ['error' => $e->getMessage()]);

            return null;
        }
    }

    private const string VERIFICATION_USER_AGENT = 'Mozilla/5.0 (compatible; FuelPriceBot/1.0; +https://fuel-price.test/bot)';

    /**
     * Verify each cited URL is reachable. Major news sites (Reuters, FT,
     * Bloomberg, BBC...) often reject HEAD with 403 / 405 even though
     * GET works fine. So: try HEAD first, then fall back to a 1-byte
     * GET (Range header) when HEAD fails. Both must include a
     * browser-shaped User-Agent or Cloudflare etc. block us as a bot.
     *
     * Every URL — verified or rejected — is logged at INFO/WARNING so
     * operators can debug rejections from `storage/logs/laravel.log`
     * without needing to capture the Anthropic response body.
     *
     * @param  array<int, array<string, mixed>>  $events
     * @return array<int, array<string, mixed>>
     */
    private function verifyCitedUrls(array $events): array
    {
        $verified = [];
        foreach ($events as $event) {
            $url = (string) ($event['url'] ?? '');
            if ($url === '') {
                Log::warning('LlmOverlayService: dropping cited event with empty URL', [
                    'headline' => $event['headline'] ?? null,
                    'source' => $event['source'] ?? null,
                ]);

                continue;
            }
            [$reachable, $diagnosis] = $this->urlReachable($url);
            if ($reachable) {
                Log::info('LlmOverlayService: URL verified', [
                    'url' => $url,
                    'via' => $diagnosis,
                ]);
                $verified[] = $event;
            } else {
                Log::warning('LlmOverlayService: URL rejected', [
                    'url' => $url,
                    'reason' => $diagnosis,
                    'headline' => $event['headline'] ?? null,
                    'source' => $event['source'] ?? null,
                ]);
            }
        }

        return $verified;
    }

    /** @return array{0: bool, 1: string} [reachable, diagnostic_string] */
    private function urlReachable(string $url): array
    {
        $headers = ['User-Agent' => self::VERIFICATION_USER_AGENT];
        $headStatus = 'no-attempt';

        try {
            $head = Http::timeout(5)
                ->withHeaders($headers)
                ->head($url);
            $headStatus = 'HEAD='.$head->status();
            if ($head->successful() || $head->redirect()) {
                return [true, $headStatus];
            }
        } catch (Throwable $e) {
            $headStatus = 'HEAD=exception('.class_basename($e).')';
        }

        try {
            $get = Http::timeout(8)
                ->withHeaders($headers + ['Range' => 'bytes=0-0'])
                ->get($url);
            $getStatus = 'GET='.$get->status();
            if ($get->successful() || $get->redirect()) {
                return [true, $headStatus.' → '.$getStatus.' (fallback)'];
            }

            return [false, $headStatus.' → '.$getStatus];
        } catch (Throwable $e) {
            return [false, $headStatus.' → GET=exception('.class_basename($e).')'];
        }
    }

    private function ridgeDirection(string $publicDirection): string
    {
        return match ($publicDirection) {
            'up' => 'rising',
            'down' => 'falling',
            default => 'flat',
        };
    }

    private function upcomingMondayDateString(): string
    {
        $today = now()->startOfDay();
        $monday = $today->isMonday() ? $today : $today->copy()->next(CarbonInterface::MONDAY);

        return $monday->toDateString();
    }

    /** @return array<string, string> */
    private function headers(): array
    {
        return [
            'x-api-key' => $this->apiKey(),
            'anthropic-version' => '2023-06-01',
        ];
    }

    private function apiKey(): ?string
    {
        return config('services.anthropic.api_key');
    }

    private function prompt(array $context): string
    {
        $json = json_encode($context, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES);

        return <<<PROMPT
            You are providing a daily news-aware overlay for a UK weekly pump-price forecast.

            The calibrated ridge model has already produced a directional call from price history.
            Your job is to search recent oil/fuel news and decide whether to AGREE or DISAGREE
            — and most importantly, surface any major-impact event that the ridge model can't see
            from price history alone.

            Search recent news (last 48 hours) for:
            - OPEC+ production decisions or unexpected announcements
            - Geopolitical events affecting oil supply (sanctions, conflict, shipping disruption)
            - Major refinery outages or pipeline incidents
            - US/EU inventory reports that materially moved Brent

            Context for this week:
            $json

            After searching, you will be asked to submit_overlay with direction, confidence
            (capped at $this->confidenceCap), short reasoning, cited events with URLs,
            agrees_with_ridge, and major_impact_event.

            Citing events with REAL URLs is mandatory. An empty citation array will be
            rejected and the overlay discarded.
            PROMPT;
    }

    private string $confidenceCap = '75';

    /** @return array<string, mixed> */
    private function submitOverlayTool(): array
    {
        return [
            'name' => 'submit_overlay',
            'description' => 'Submit the news-aware overlay for the upcoming weekly forecast.',
            'input_schema' => [
                'type' => 'object',
                'properties' => [
                    'direction' => ['type' => 'string', 'enum' => ['rising', 'falling', 'flat']],
                    'confidence' => ['type' => 'integer', 'minimum' => 0, 'maximum' => self::CONFIDENCE_CAP],
                    'reasoning_short' => ['type' => 'string', 'description' => '1–2 sentences.'],
                    'events_cited' => [
                        'type' => 'array',
                        'items' => [
                            'type' => 'object',
                            'properties' => [
                                'headline' => ['type' => 'string'],
                                'source' => ['type' => 'string'],
                                'url' => ['type' => 'string'],
                                'impact' => ['type' => 'string', 'enum' => ['rising', 'falling', 'neutral']],
                            ],
                            'required' => ['headline', 'source', 'url', 'impact'],
                        ],
                    ],
                    'agrees_with_ridge' => ['type' => 'boolean'],
                    'major_impact_event' => ['type' => 'boolean'],
                ],
                'required' => ['direction', 'confidence', 'reasoning_short', 'events_cited', 'agrees_with_ridge', 'major_impact_event'],
            ],
        ];
    }

    /**
     * @param  array<int, mixed>  $content
     * @return array<string, mixed>|null
     */
    private function extractToolInput(array $content): ?array
    {
        $block = collect($content)->firstWhere('type', 'tool_use');

        return $block['input'] ?? null;
    }
}