<?php

declare(strict_types=1);

namespace TFGraphics\SmartImport\Merge;

use TFGraphics\SmartImport\Merge\Contracts\MergeStrategyInterface;

final class MergeStrategy implements MergeStrategyInterface
{
    public const HIGHEST_QUALITY = 'Highest Quality';
    public const LONGEST_DESCRIPTION = 'Longest Description';
    public const NEWEST = 'Newest';
    public const PREFERRED_PROVIDER = 'Preferred Provider';
    public const HIGHEST_CONFIDENCE = 'Highest Confidence';
    public const MANUAL = 'Manual';

    private MergeScore $score;

    public function __construct(?MergeScore $score = null) { $this->score = $score ?? new MergeScore(); }

    public function select(string $field, array $evidence, MergePolicy $policy): ?MergeEvidence
    {
        $evidence = array_values(array_filter($evidence, static fn ($item): bool => $item instanceof MergeEvidence));
        if ($evidence === []) return null;
        $strategy = $policy->getStrategy($field);

        if ($strategy === self::MANUAL) {
            $manual = $policy->getManualValue($field);
            foreach ($evidence as $candidate) if ($candidate->getValue() === $manual) return $candidate;
            return $manual !== null ? new MergeEvidence($field, $manual, 'Manual', 1.0, 1.0) : null;
        }
        if ($strategy === self::PREFERRED_PROVIDER) {
            $preferred = strtolower((string) $policy->getPreferredProvider($field));
            foreach ($evidence as $candidate) if (strtolower($candidate->getProvider()) === $preferred) return $candidate;
        }

        usort($evidence, function (MergeEvidence $left, MergeEvidence $right) use ($strategy): int {
            if ($strategy === self::LONGEST_DESCRIPTION) {
                $comparison = strlen((string) $right->getValue()) <=> strlen((string) $left->getValue());
            } elseif ($strategy === self::NEWEST) {
                $comparison = ($right->getObservedAt()?->getTimestamp() ?? 0) <=> ($left->getObservedAt()?->getTimestamp() ?? 0);
            } elseif ($strategy === self::HIGHEST_CONFIDENCE) {
                $comparison = $this->score->confidence($right) <=> $this->score->confidence($left);
            } else {
                $comparison = $this->score->quality($right) <=> $this->score->quality($left);
            }

            return $comparison
                ?: ($this->score->combined($right) <=> $this->score->combined($left))
                ?: strcasecmp($left->getProvider(), $right->getProvider())
                ?: strcmp(serialize($left->getValue()), serialize($right->getValue()));
        });

        return $evidence[0];
    }
}