Files
fuel-price/app/Services/Prediction/Signals/TrendSignal.php
Ovidiu U 27c82ef103 refactor: extract 6 prediction signals into Signal classes
The 803-line NationalFuelPredictionService had six private compute*Signal
methods, a private linearRegression helper, and a private disabledSignal
shape factory all crammed together. Each signal is now an independently
testable class.

- App\Services\Prediction\Signals\Signal — interface
- App\Services\Prediction\Signals\SignalContext — input value object
  (FuelType + optional lat/lng + hasCoordinates() helper)
- App\Services\Prediction\Signals\AbstractSignal — shared
  disabledSignal() and linearRegression() helpers
- TrendSignal, DayOfWeekSignal, BrandBehaviourSignal, StickinessSignal,
  RegionalMomentumSignal, OilSignal — one class each, extending
  AbstractSignal

NationalFuelPredictionService receives the 6 signal classes via constructor
injection and orchestrates them. The lat/lng null-guard for regional
momentum now lives inside RegionalMomentumSignal::compute() so the
coordinator no longer branches on coordinate presence.

Aggregation, weekly summary, and reasoning helpers stay in the service
for now — they are coupled to the public predict() output shape and are
candidates for a follow-up extraction once a stable API is locked in.

Service: 803 → 414 lines.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
2026-04-29 19:43:28 +01:00

87 lines
3.3 KiB
PHP

<?php
namespace App\Services\Prediction\Signals;
use Illuminate\Support\Facades\DB;
final class TrendSignal extends AbstractSignal
{
private const float R_SQUARED_THRESHOLD = 0.5;
private const float SLOPE_THRESHOLD_PENCE = 0.3;
private const float SLOPE_SATURATION_PENCE = 0.5;
private const int PREDICTION_HORIZON_DAYS = 7;
/** @return array{score: float, confidence: float, direction: string, detail: string, data_points: int, enabled: bool, slope: float, r_squared: float} */
public function compute(SignalContext $context): array
{
foreach ([5, 14] as $lookbackDays) {
$rows = DB::table('station_prices')
->where('fuel_type', $context->fuelType->value)
->where('price_effective_at', '>=', now()->subDays($lookbackDays))
->selectRaw('DATE(price_effective_at) as day, AVG(price_pence) as avg_price')
->groupBy('day')
->orderBy('day')
->get();
if ($rows->count() < 2) {
continue;
}
$regression = $this->linearRegression($rows->pluck('avg_price')->map(fn ($v) => (float) $v / 100)->values()->all());
if ($regression['r_squared'] >= self::R_SQUARED_THRESHOLD) {
$slope = $regression['slope'];
$direction = match (true) {
$slope >= self::SLOPE_THRESHOLD_PENCE => 'up',
$slope <= -self::SLOPE_THRESHOLD_PENCE => 'down',
default => 'stable',
};
$absSlope = abs($slope);
$score = $direction === 'stable' ? 0.0 : min(1.0, $absSlope / self::SLOPE_SATURATION_PENCE) * ($slope > 0 ? 1 : -1);
$projected = round($slope * $lookbackDays, 1);
$detail = $direction === 'stable'
? "Prices flat over {$lookbackDays} days (slope: {$slope}p/day, R²={$regression['r_squared']})"
: sprintf(
'%s at %sp/day over %d days (R²=%s, ~%s%sp in %dd)',
$slope > 0 ? 'Rising' : 'Falling',
abs(round($slope, 2)),
$lookbackDays,
round($regression['r_squared'], 2),
$projected > 0 ? '+' : '',
$projected,
self::PREDICTION_HORIZON_DAYS,
);
if ($lookbackDays === 5) {
$detail .= ' [Adaptive lookback active]';
}
return [
'score' => $score,
'confidence' => min(1.0, $regression['r_squared']),
'direction' => $direction,
'detail' => $detail,
'data_points' => $rows->count(),
'enabled' => true,
'slope' => round($slope, 3),
'r_squared' => round($regression['r_squared'], 3),
];
}
}
return [
'score' => 0.0,
'confidence' => 0.0,
'direction' => 'stable',
'detail' => 'Insufficient price history or noisy data (R² below threshold)',
'data_points' => 0,
'enabled' => false,
'slope' => 0.0,
'r_squared' => 0.0,
];
}
}