<?php

namespace App\Services;

use App\Models\User;
use Illuminate\Support\Arr;
use Illuminate\Support\Str;

/** Identities and mutation history inside the existing workflow JSON, never parallel tables. */
class OpportunityCanonicalMetadata
{
    /** @param array<string,mixed> $payload
     * @return array<string,array<string,mixed>> */
    private function items(array $payload, string $path = ''): array
    {
        $found = [];
        foreach ($payload as $key => $value) {
            $pointer = ltrim($path.'.'.$key, '.');
            if (! is_array($value)) {
                continue;
            }
            if (! array_is_list($value)) {
                $found[$pointer] = $value;
            }
            $found += $this->items($value, $pointer);
        }

        return $found;
    }

    /** @param array<string,mixed> $before
     * @param array<string,mixed> $after
     * @param array<string,mixed> $metadata
     * @return array<string,mixed> */
    public function mutate(array $before, array $after, array $metadata, User $actor, string $reason): array
    {
        $old = $this->items($before);
        $new = $this->items($after);
        $active = $metadata['active'] ?? [];
        $retired = $metadata['deleted'] ?? [];
        $next = [];
        $used = [];
        foreach ($new as $path => $value) {
            $fingerprint = OpportunityCanonicalValue::hash($value);
            $match = null;
            // A collection reorder preserves identity by bytes, not by its new index.
            foreach ($active as $previousPath => $item) {
                if (! isset($used[$previousPath]) && ($item['fingerprint'] ?? '') === $fingerprint
                    && preg_replace('/\.\d+(?=\.|$)/', '.*', $previousPath) === preg_replace('/\.\d+(?=\.|$)/', '.*', $path)) {
                    $match = $previousPath;
                    break;
                }
            }
            // Named singleton modules have a stable path; list rows need an unambiguous match.
            if ($match === null && ! preg_match('/\.\d+(?:\.|$)/', $path) && isset($active[$path]) && ! isset($used[$path])) {
                $match = $path;
            }
            $item = $match !== null ? $active[$match] : null;
            if ($match !== null) {
                $used[$match] = true;
            }
            $changed = $item === null || ($item['fingerprint'] ?? '') !== $fingerprint;
            $legacy = $item === null && isset($old[$path]);
            $item ??= ['id' => (string) Str::uuid(), 'version' => 0, 'created_by' => $legacy ? null : $actor->id,
                'created_at' => $legacy ? null : now()->toIso8601String(), 'first_observed_at' => now()->toIso8601String(),
                'identity_source' => $legacy ? 'legacy_first_observation_not_creation' : 'server_generated_new_item'];
            if ($changed) {
                $item['version']++;
                $item['updated_by'] = $actor->id;
                $item['updated_at'] = now()->toIso8601String();
            }
            $next[$path] = [...$item, 'fingerprint' => $fingerprint, 'is_deleted' => false,
                'active' => true, 'deleted_at' => null, 'deleted_by' => null, 'delete_reason' => null];
        }
        foreach ($active as $path => $item) {
            if (isset($used[$path])) {
                continue;
            }
            $retired[$item['id']] = [...$item, 'path' => $path, 'version' => $item['version'] + 1,
                'is_deleted' => true, 'active' => false, 'deleted_at' => now()->toIso8601String(),
                'deleted_by' => $actor->id, 'delete_reason' => $reason, 'last_value' => $old[$path] ?? null];
        }

        return ['active' => $next, 'deleted' => $retired, 'rule' => 'existing-json-identities-v1'];
    }

    /** @param array<string,mixed> $payload
     * @param array<string,mixed> $metadata
     * @return array<string,mixed> */
    public function project(array $payload, array $metadata): array
    {
        // Deepest paths first so a parent does not overwrite the children's identities.
        $paths = array_keys($metadata['active'] ?? []);
        foreach ($paths as $path) {
            if (! is_string($path)) {
                throw new \UnexpectedValueException('Canonical item paths must be named fields.');
            }
        }
        usort($paths, fn ($a, $b) => substr_count($b, '.') <=> substr_count($a, '.'));
        foreach ($paths as $path) {
            $value = Arr::get($payload, $path);
            if (! is_array($value)) {
                continue;
            }
            $item = $metadata['active'][$path];
            unset($item['fingerprint']);
            Arr::set($payload, $path, [...$value, ...$item]);
        }

        return $payload;
    }
}