<?php

namespace App\Services;

use App\Models\SimulationFormDraft;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Str;
use Symfony\Component\HttpKernel\Exception\HttpException;

final class SimulationFormDrafts
{
    /** @param array{personal_snapshot: array<string,mixed>, economic_snapshot: array<string,mixed>} $data */
    public function create(array $data, Request $request, string $key): array
    {
        [$actorId, $tokenHash] = $this->context($request);
        $scope = $actorId === null ? 'anonymous:'.$tokenHash : 'user:'.$actorId;
        $keyHash = hash_hmac('sha256', strtolower($key), (string) config('app.key'));
        $canonicalPayload = json_encode($this->canonical($data), JSON_THROW_ON_ERROR | JSON_UNESCAPED_UNICODE);
        $payloadHash = hash('sha256', $canonicalPayload);

        return DB::transaction(function () use ($actorId, $tokenHash, $scope, $keyHash, $payloadHash, $canonicalPayload, $data): array {
            $this->setContext($actorId, $tokenHash);
            DB::select('select pg_advisory_xact_lock(261010, hashtext(?))', [$scope]);

            $query = SimulationFormDraft::query()->whereNull('deleted_at')->lockForUpdate();
            $query = $actorId === null ? $query->where('anonymous_token_hash', $tokenHash) : $query->where('owner_user_id', $actorId);
            $draft = $query->first();
            if ($draft) {
                if (hash_equals($draft->create_key_hash, $keyHash)) {
                    abort_unless(hash_equals($draft->create_payload_hash, $payloadHash), 409, 'Idempotency-Key já foi utilizada com outros dados.');

                    return ['draft' => $draft, 'replayed' => true];
                }
                throw new HttpException(409, 'Já existe um rascunho activo. Carregue-o antes de guardar novas alterações.');
            }

            $draft = SimulationFormDraft::query()->create([
                'id' => (string) Str::uuid(), 'owner_user_id' => $actorId, 'anonymous_token_hash' => $tokenHash,
                'version_no' => 1, 'create_key_hash' => $keyHash, 'create_payload_hash' => $payloadHash, 'snapshot_sha256' => $payloadHash,
                'personal_snapshot' => SimulationFormDraft::encryptSnapshot($data['personal_snapshot']),
                'economic_snapshot' => SimulationFormDraft::encryptSnapshot($data['economic_snapshot']),
            ]);

            return ['draft' => $draft, 'replayed' => false];
        }, 3);
    }

    /** @param array{personal_snapshot: array<string,mixed>, economic_snapshot: array<string,mixed>} $data */
    public function update(string $id, array $data, Request $request): SimulationFormDraft
    {
        [$actorId, $tokenHash] = $this->context($request);

        return DB::transaction(function () use ($id, $data, $request, $actorId, $tokenHash): SimulationFormDraft {
            $this->setContext($actorId, $tokenHash);
            $draft = SimulationFormDraft::query()->whereNull('deleted_at')->lockForUpdate()->findOrFail($id);
            $this->requireMatch($request, $draft);
            $canonicalPayload = json_encode($this->canonical($data), JSON_THROW_ON_ERROR | JSON_UNESCAPED_UNICODE);
            $draft->update([
                'personal_snapshot' => SimulationFormDraft::encryptSnapshot($data['personal_snapshot']),
                'economic_snapshot' => SimulationFormDraft::encryptSnapshot($data['economic_snapshot']),
                'snapshot_sha256' => hash('sha256', $canonicalPayload), 'version_no' => $draft->version_no + 1,
            ]);

            return $draft->refresh();
        }, 3);
    }

    public function current(Request $request): ?SimulationFormDraft
    {
        [$actorId, $tokenHash] = $this->context($request);

        return DB::transaction(function () use ($actorId, $tokenHash): ?SimulationFormDraft {
            $this->setContext($actorId, $tokenHash);
            $query = SimulationFormDraft::query()->whereNull('deleted_at');

            return ($actorId === null ? $query->where('anonymous_token_hash', $tokenHash) : $query->where('owner_user_id', $actorId))->first();
        });
    }

    public function find(string $id, Request $request): SimulationFormDraft
    {
        [$actorId, $tokenHash] = $this->context($request);

        return DB::transaction(function () use ($id, $actorId, $tokenHash): SimulationFormDraft {
            $this->setContext($actorId, $tokenHash);

            return SimulationFormDraft::query()->whereNull('deleted_at')->findOrFail($id);
        });
    }

    public function delete(string $id, Request $request): void
    {
        [$actorId, $tokenHash] = $this->context($request);
        DB::transaction(function () use ($id, $request, $actorId, $tokenHash): void {
            $this->setContext($actorId, $tokenHash);
            $draft = SimulationFormDraft::query()->whereNull('deleted_at')->lockForUpdate()->findOrFail($id);
            $this->requireMatch($request, $draft);
            $draft->update(['deleted_at' => now()]);
        }, 3);
    }

    /** @return array<string,mixed> */
    public function present(SimulationFormDraft $draft): array
    {
        return [
            'id' => $draft->id,
            'version_no' => $draft->version_no,
            'snapshot_sha256' => $draft->snapshot_sha256,
            'personal_snapshot' => SimulationFormDraft::decryptSnapshot($draft->personal_snapshot),
            'economic_snapshot' => SimulationFormDraft::decryptSnapshot($draft->economic_snapshot),
            'updated_at' => $draft->updated_at,
        ];
    }

    public function etag(SimulationFormDraft $draft): string
    {
        return '"sfd-'.$draft->id.'-v'.$draft->version_no.'"';
    }

    /** @return array{0:int|null,1:string|null} */
    private function context(Request $request): array
    {
        $actorId = $request->user()?->id;
        $token = $request->header('X-Simulation-Token');
        abort_unless($actorId !== null || (is_string($token) && strlen($token) >= 32 && strlen($token) <= 256), 422,
            'X-Simulation-Token opaco é obrigatório para um rascunho anónimo.');

        return [$actorId, $actorId === null ? hash_hmac('sha256', $token, (string) config('app.key')) : null];
    }

    private function setContext(?int $actorId, ?string $tokenHash): void
    {
        DB::select("select set_config('app.actor_user_id', ?, true), set_config('app.simulation_token_hash', ?, true)", [(string) ($actorId ?? ''), (string) ($tokenHash ?? '')]);
    }

    private function requireMatch(Request $request, SimulationFormDraft $draft): void
    {
        $provided = $request->header('If-Match');
        if (! $provided) {
            throw new HttpException(428, 'If-Match é obrigatório.');
        }
        if (! hash_equals($this->etag($draft), trim($provided))) {
            throw new HttpException(412, 'O rascunho foi alterado desde a última leitura.');
        }
    }

    private function canonical(mixed $value): mixed
    {
        if (! is_array($value)) {
            return $value;
        }
        if (! array_is_list($value)) {
            ksort($value);
        }
        foreach ($value as $key => $item) {
            $value[$key] = $this->canonical($item);
        }

        return $value;
    }
}