<?php

namespace Modules\Stylist\Diagnostics;

use Illuminate\Filesystem\Filesystem;
use Modules\Stylist\Theme\Loader;
use Modules\Stylist\Theme\Theme;

final class ThemeInspector
{
    public function __construct(
        private readonly Filesystem $files,
        private readonly Loader $loader,
    ) {}

    /** @return array<int, array<string, mixed>> */
    public function themes(): array
    {
        return $this->loader->all()->map(function (Theme $theme): array {
            return [
                'key' => $theme->key(),
                'name' => $theme->name(),
                'parent' => $theme->parent(),
                'path' => $theme->path(),
                'views' => count($this->viewFiles($theme)),
                'entry_view' => $theme->entryView(),
            ];
        })->values()->all();
    }

    /** @return array<string, array<int, array{theme:string,path:string}>> */
    public function duplicateViews(): array
    {
        $ownership = [];

        foreach ($this->loader->all() as $theme) {
            foreach ($this->viewFiles($theme) as $relative => $absolute) {
                $ownership[$relative][] = [
                    'theme' => $theme->key(),
                    'path' => $absolute,
                ];
            }
        }

        return array_filter($ownership, fn (array $owners): bool => count($owners) > 1);
    }

    /** @return array<int, array{severity:string,theme:string,message:string}> */
    public function issues(): array
    {
        $issues = [];
        $themes = $this->loader->all();

        foreach ($themes as $theme) {
            $parent = $theme->parent();

            if ($parent !== null && ! $themes->has($parent)) {
                $issues[] = [
                    'severity' => 'error',
                    'theme' => $theme->key(),
                    'message' => "Parent theme [{$parent}] is not installed.",
                ];
            }

            if ($this->hasInheritanceCycle($theme, $themes->all())) {
                $issues[] = [
                    'severity' => 'error',
                    'theme' => $theme->key(),
                    'message' => 'Theme inheritance contains a cycle.',
                ];
            }

            $entry = $theme->path().'/views/'.str_replace('.', '/', $theme->entryView()).'.blade.php';
            if (! $this->files->exists($entry) && $parent === null) {
                $issues[] = [
                    'severity' => 'warning',
                    'theme' => $theme->key(),
                    'message' => "Entry view [{$theme->entryView()}] does not exist in this theme.",
                ];
            }
        }

        foreach ($this->duplicateViews() as $view => $owners) {
            $issues[] = [
                'severity' => 'error',
                'theme' => implode(', ', array_column($owners, 'theme')),
                'message' => "View [{$view}] has multiple owners.",
            ];
        }

        $default = (string) config('stylist.default_theme');
        if ($default !== '' && ! $themes->has($default)) {
            $issues[] = [
                'severity' => 'warning',
                'theme' => $default,
                'message' => 'Configured default theme is not installed.',
            ];
        }

        return $issues;
    }

    /** @return array<string, string> */
    private function viewFiles(Theme $theme): array
    {
        $root = $theme->path().'/views';
        if (! $this->files->isDirectory($root)) {
            return [];
        }

        $views = [];
        foreach ($this->files->allFiles($root) as $file) {
            if (! str_ends_with($file->getFilename(), '.blade.php')) {
                continue;
            }

            $absolute = str_replace('\\', '/', $file->getPathname());
            $relative = ltrim(str_replace(str_replace('\\', '/', $root), '', $absolute), '/');
            $views[$relative] = $absolute;
        }

        ksort($views);

        return $views;
    }

    /** @param array<string, Theme> $themes */
    private function hasInheritanceCycle(Theme $theme, array $themes): bool
    {
        $seen = [];
        $key = $theme->key();

        while (isset($themes[$key])) {
            if (isset($seen[$key])) {
                return true;
            }

            $seen[$key] = true;
            $key = $themes[$key]->parent() ?? '';
            if ($key === '') {
                return false;
            }
        }

        return false;
    }
}