<?php

namespace App\Services\Care;

use App\Models\CareUnit;
use App\Models\MarAdministration;
use App\Models\MarOrder;
use App\Models\Prescription;
use App\Models\PrescriptionItem;
use App\Models\Visit;
use Carbon\Carbon;
use Carbon\CarbonInterface;
use Illuminate\Support\Collection;
use Illuminate\Validation\ValidationException;

class MarService
{
    /**
     * Default clock times by frequency code.
     *
     * @var array<string, list<string>>
     */
    protected array $defaultTimes = [
        'od' => ['08:00'],
        'bd' => ['08:00', '20:00'],
        'tds' => ['08:00', '14:00', '20:00'],
        'qds' => ['06:00', '12:00', '18:00', '22:00'],
        'q4h' => ['00:00', '04:00', '08:00', '12:00', '16:00', '20:00'],
        'q6h' => ['00:00', '06:00', '12:00', '18:00'],
        'q8h' => ['06:00', '14:00', '22:00'],
        'prn' => [],
        'stat' => [],
        'custom' => ['08:00'],
    ];

    /**
     * Sync MAR orders from active/dispensed prescriptions on a visit.
     *
     * @return Collection<int, MarOrder>
     */
    public function syncOrdersForVisit(Visit $visit, string $ownerRef): Collection
    {
        $prescriptions = Prescription::owned($ownerRef)
            ->where('visit_id', $visit->id)
            ->whereIn('status', [Prescription::STATUS_ACTIVE, Prescription::STATUS_DISPENSED])
            ->with('items')
            ->get();

        foreach ($prescriptions as $prescription) {
            foreach ($prescription->items as $item) {
                if ($item->is_procedure) {
                    continue;
                }
                $this->upsertOrderFromItem($visit, $prescription, $item, $ownerRef);
            }
        }

        return MarOrder::owned($ownerRef)
            ->where('visit_id', $visit->id)
            ->where('status', MarOrder::STATUS_ACTIVE)
            ->orderBy('drug_name')
            ->get();
    }

    public function upsertOrderFromItem(
        Visit $visit,
        Prescription $prescription,
        PrescriptionItem $item,
        string $ownerRef,
        ?string $frequencyCode = null,
    ): MarOrder {
        $parsed = $this->parseFrequency((string) ($item->frequency ?? ''), $frequencyCode);

        return MarOrder::query()->updateOrCreate(
            ['prescription_item_id' => $item->id],
            [
                'owner_ref' => $ownerRef,
                'organization_id' => $visit->organization_id,
                'visit_id' => $visit->id,
                'patient_id' => $visit->patient_id,
                'prescription_id' => $prescription->id,
                'drug_name' => $item->name,
                'dosage' => $item->dosage,
                'route' => $item->route,
                'frequency_code' => $parsed['code'],
                'times_of_day' => $parsed['times'],
                'is_prn' => $parsed['is_prn'],
                'status' => MarOrder::STATUS_ACTIVE,
                'starts_at' => $visit->placed_at ?? $visit->checked_in_at ?? now(),
                'instructions' => $item->instructions,
            ],
        );
    }

    /**
     * Due / overdue / PRN slots for placed patients on a care unit for a calendar day.
     *
     * @return list<array<string, mixed>>
     */
    public function unitRoundBoard(CareUnit $unit, string $ownerRef, ?CarbonInterface $day = null): array
    {
        $day = Carbon::parse($day ?? now())->startOfDay();

        $visits = Visit::owned($ownerRef)
            ->where('organization_id', $unit->organization_id)
            ->where('care_unit_id', $unit->id)
            ->whereIn('status', [Visit::STATUS_OPEN, Visit::STATUS_IN_PROGRESS])
            ->with(['patient', 'bed'])
            ->get();

        $rows = [];
        foreach ($visits as $visit) {
            $orders = $this->syncOrdersForVisit($visit, $ownerRef);
            foreach ($orders as $order) {
                foreach ($this->dueSlotsForOrder($order, $day) as $slot) {
                    $rows[] = $slot + [
                        'visit' => $visit,
                        'patient' => $visit->patient,
                        'bed' => $visit->bed,
                        'order' => $order,
                    ];
                }
            }
        }

        usort($rows, function (array $a, array $b) {
            $aTime = $a['scheduled_for']?->timestamp ?? PHP_INT_MAX;
            $bTime = $b['scheduled_for']?->timestamp ?? PHP_INT_MAX;
            if ($aTime === $bTime) {
                return strcmp((string) ($a['patient']?->fullName() ?? ''), (string) ($b['patient']?->fullName() ?? ''));
            }

            return $aTime <=> $bTime;
        });

        return $rows;
    }

    /**
     * @return list<array{scheduled_for: ?Carbon, state: string, administration: ?MarAdministration}>
     */
    public function dueSlotsForOrder(MarOrder $order, CarbonInterface $day): array
    {
        $day = Carbon::parse($day)->startOfDay();
        $end = $day->copy()->endOfDay();

        if ($order->status !== MarOrder::STATUS_ACTIVE) {
            return [];
        }

        if ($order->starts_at && $order->starts_at->gt($end)) {
            return [];
        }
        if ($order->ends_at && $order->ends_at->lt($day)) {
            return [];
        }

        $existing = MarAdministration::query()
            ->where('mar_order_id', $order->id)
            ->where(function ($q) use ($day, $end) {
                $q->whereBetween('scheduled_for', [$day, $end])
                    ->orWhere(function ($q2) use ($day, $end) {
                        $q2->whereNull('scheduled_for')
                            ->whereBetween('recorded_at', [$day, $end]);
                    });
            })
            ->get();

        if ($order->is_prn || $order->frequency_code === 'prn') {
            $givenToday = $existing->where('status', MarAdministration::STATUS_GIVEN);

            return [[
                'scheduled_for' => null,
                'state' => $givenToday->isNotEmpty() ? 'prn_given' : 'prn_due',
                'administration' => $givenToday->sortByDesc('recorded_at')->first(),
            ]];
        }

        if ($order->frequency_code === 'stat') {
            $admin = $existing->first();

            return [[
                'scheduled_for' => $order->starts_at ?? $day->copy()->setTime(8, 0),
                'state' => $admin ? $admin->status : 'due',
                'administration' => $admin,
            ]];
        }

        $times = $order->times_of_day ?: ($this->defaultTimes[$order->frequency_code] ?? ['08:00']);
        $slots = [];
        foreach ($times as $time) {
            [$h, $m] = array_map('intval', explode(':', $time) + [0, 0]);
            $scheduled = $day->copy()->setTime($h, $m);
            if ($order->starts_at && $scheduled->lt($order->starts_at)) {
                continue;
            }

            $admin = $existing->first(function (MarAdministration $a) use ($scheduled) {
                return $a->scheduled_for && $a->scheduled_for->equalTo($scheduled);
            });

            $state = 'due';
            if ($admin) {
                $state = $admin->status;
            } elseif ($scheduled->lt(now()->subMinutes(30))) {
                $state = 'overdue';
            }

            $slots[] = [
                'scheduled_for' => $scheduled,
                'state' => $state,
                'administration' => $admin,
            ];
        }

        return $slots;
    }

    public function recordAdministration(
        MarOrder $order,
        string $status,
        string $ownerRef,
        ?string $actorRef,
        ?CarbonInterface $scheduledFor = null,
        ?string $doseGiven = null,
        ?string $route = null,
        ?string $witnessBy = null,
        ?string $reason = null,
        ?string $notes = null,
        ?int $careUnitId = null,
    ): MarAdministration {
        if (! in_array($status, [
            MarAdministration::STATUS_GIVEN,
            MarAdministration::STATUS_HELD,
            MarAdministration::STATUS_REFUSED,
            MarAdministration::STATUS_MISSED,
        ], true)) {
            throw ValidationException::withMessages(['status' => 'Invalid MAR status.']);
        }

        if ($order->status !== MarOrder::STATUS_ACTIVE) {
            throw ValidationException::withMessages(['mar_order_id' => 'This MAR order is not active.']);
        }

        if (in_array($status, [MarAdministration::STATUS_HELD, MarAdministration::STATUS_REFUSED, MarAdministration::STATUS_MISSED], true)
            && blank($reason) && blank($notes)) {
            throw ValidationException::withMessages([
                'reason' => 'Provide a reason when holding, refusing, or marking missed.',
            ]);
        }

        $visit = $order->visit ?? Visit::query()->findOrFail($order->visit_id);

        if ($scheduledFor && ! $order->is_prn) {
            $duplicate = MarAdministration::query()
                ->where('mar_order_id', $order->id)
                ->where('scheduled_for', $scheduledFor)
                ->exists();
            if ($duplicate) {
                throw ValidationException::withMessages([
                    'scheduled_for' => 'This dose slot is already recorded.',
                ]);
            }
        }

        $admin = MarAdministration::create([
            'owner_ref' => $ownerRef,
            'organization_id' => $order->organization_id,
            'mar_order_id' => $order->id,
            'visit_id' => $order->visit_id,
            'patient_id' => $order->patient_id,
            'care_unit_id' => $careUnitId ?? $visit->care_unit_id,
            'scheduled_for' => $scheduledFor,
            'recorded_at' => now(),
            'status' => $status,
            'dose_given' => $doseGiven ?? $order->dosage,
            'route' => $route ?? $order->route,
            'administered_by' => $actorRef,
            'witness_by' => $witnessBy,
            'reason' => $reason,
            'notes' => $notes,
        ]);

        AuditLogger::record(
            $ownerRef,
            'mar.'.$status,
            $order->organization_id,
            $actorRef,
            MarAdministration::class,
            $admin->id,
            ['mar_order_id' => $order->id, 'visit_id' => $order->visit_id],
        );

        return $admin;
    }

    /**
     * @return array{code: string, times: list<string>, is_prn: bool}
     */
    public function parseFrequency(string $frequency, ?string $override = null): array
    {
        if ($override && isset($this->defaultTimes[$override])) {
            return [
                'code' => $override,
                'times' => $this->defaultTimes[$override],
                'is_prn' => $override === 'prn',
            ];
        }

        $raw = strtolower(trim($frequency));
        $map = [
            'od' => 'od', 'once daily' => 'od', 'daily' => 'od', 'once a day' => 'od', '1x' => 'od',
            'bd' => 'bd', 'bid' => 'bd', 'twice daily' => 'bd', 'twice a day' => 'bd', '2x' => 'bd',
            'tds' => 'tds', 'tid' => 'tds', 'three times' => 'tds', '3x' => 'tds',
            'qds' => 'qds', 'qid' => 'qds', 'four times' => 'qds', '4x' => 'qds',
            'q4h' => 'q4h', 'every 4' => 'q4h',
            'q6h' => 'q6h', 'every 6' => 'q6h',
            'q8h' => 'q8h', 'every 8' => 'q8h',
            'prn' => 'prn', 'as needed' => 'prn', 'when required' => 'prn',
            'stat' => 'stat', 'immediately' => 'stat', 'now' => 'stat',
        ];

        foreach ($map as $needle => $code) {
            if ($raw === $needle || str_contains($raw, $needle)) {
                return [
                    'code' => $code,
                    'times' => $this->defaultTimes[$code],
                    'is_prn' => $code === 'prn',
                ];
            }
        }

        return [
            'code' => 'od',
            'times' => $this->defaultTimes['od'],
            'is_prn' => false,
        ];
    }
}