<?php

namespace Modules\Stylist\Theme;

use Modules\Stylist\Theme\Exceptions\InvalidThemeManifestException;

final class ManifestValidator
{
    /** @return array<string, mixed> */
    public function validate(array $manifest, string $path): array
    {
        $errors = [];
        $manifestVersion = $manifest['manifest_version'] ?? $manifest['schema_version'] ?? 1;
        if ((is_string($manifestVersion) && ctype_digit($manifestVersion))) {
            $manifestVersion = (int) $manifestVersion;
        }
        if (! is_int($manifestVersion) || $manifestVersion < 1) {
            $errors[] = 'The manifest_version must be a positive integer.';
        }

        $key = $manifest['key'] ?? $manifest['slug'] ?? basename($path);

        if (! is_string($key) || ! preg_match('/^[a-z0-9][a-z0-9_-]*$/', $key)) {
            $errors[] = 'The key/slug must contain only lowercase letters, numbers, dashes, and underscores.';
        }
        if (isset($manifest['name']) && (! is_string($manifest['name']) || trim($manifest['name']) === '')) {
            $errors[] = 'The name must be a non-empty string.';
        }
        if (isset($manifest['version']) && (! is_string($manifest['version']) || ! preg_match('/^\d+\.\d+\.\d+(?:[-+][0-9A-Za-z.-]+)?$/', $manifest['version']))) {
            $errors[] = 'The version must use semantic versioning, for example 1.2.0.';
        }
        if (isset($manifest['type']) && ! in_array($manifest['type'], ['frontend', 'backend', 'common'], true)) {
            $errors[] = 'The type must be frontend, backend, or common.';
        }
        $parent = $manifest['extends'] ?? $manifest['parent'] ?? null;
        if ($parent !== null && (! is_string($parent) || ! preg_match('/^[a-z0-9][a-z0-9_-]*$/', $parent))) {
            $errors[] = 'The extends/parent value must be a valid theme key.';
        }

        foreach (['stylesheet', 'script', 'preview'] as $field) {
            if (isset($manifest[$field]) && ! $this->isSafeRelativePath($manifest[$field])) {
                $errors[] = "The {$field} value must be a safe relative path.";
            }
        }

        foreach (['assets', 'variables', 'supports', 'capabilities', 'variants', 'appearances', 'accents', 'settings', 'seo'] as $field) {
            if (isset($manifest[$field]) && ! is_array($manifest[$field])) {
                $errors[] = "The {$field} value must be an object or array.";
            }
        }

        $variants = $this->normaliseDefinitions($manifest['variants'] ?? [], 'variants', $errors, false);
        $appearances = $this->normaliseDefinitions($manifest['appearances'] ?? [], 'appearances', $errors);
        $accents = $this->normaliseDefinitions($manifest['accents'] ?? [], 'accents', $errors);
        $capabilities = $this->normaliseCapabilities($manifest['capabilities'] ?? [], $errors);
        $capabilities['appearances'] = $appearances !== [];
        $capabilities['accents'] = $accents !== [];
        $capabilities['preview'] = isset($manifest['preview']) || is_file($path.'/preview.webp');

        $defaultAppearance = $manifest['default_appearance'] ?? null;
        if ($defaultAppearance !== null) {
            if (! is_string($defaultAppearance) || $defaultAppearance === '') {
                $errors[] = 'The default_appearance value must be a non-empty string.';
            } elseif ($appearances === [] || ! array_key_exists($defaultAppearance, $appearances)) {
                $errors[] = 'The default_appearance value must be declared in appearances.';
            }
        }

        $defaultAccent = $manifest['default_accent'] ?? null;
        if ($defaultAccent !== null) {
            if (! is_string($defaultAccent) || $defaultAccent === '') {
                $errors[] = 'The default_accent value must be a non-empty string.';
            } elseif ($accents === [] || ! array_key_exists($defaultAccent, $accents)) {
                $errors[] = 'The default_accent value must be declared in accents.';
            }
        }

        if ($errors !== []) {
            throw InvalidThemeManifestException::forPath($path, $errors);
        }

        $manifest['manifest_version'] = $manifestVersion;
        unset($manifest['schema_version']);
        $manifest['key'] = $key;
        $manifest['slug'] = $key;
        $manifest['name'] = $manifest['name'] ?? str($key)->headline()->toString();
        $manifest['extends'] = $parent;
        $manifest['version'] = (string) ($manifest['version'] ?? '1.0.0');
        $manifest['entry_view'] = (string) ($manifest['entry_view'] ?? 'home');
        $manifest['stylesheet'] = $manifest['stylesheet'] ?? $manifest['css'] ?? 'css/theme.css';
        $manifest['script'] = $manifest['script'] ?? 'js/app.js';
        $manifest['assets'] = is_array($manifest['assets'] ?? null) ? $manifest['assets'] : [];
        $manifest['variables'] = is_array($manifest['variables'] ?? null) ? $manifest['variables'] : [];
        $manifest['supports'] = is_array($manifest['supports'] ?? null) ? $manifest['supports'] : [];
        $manifest['capabilities'] = $capabilities;
        $manifest['variants'] = $variants;
        $manifest['appearances'] = $appearances;
        $manifest['accents'] = $accents;
        $manifest['settings'] = is_array($manifest['settings'] ?? null) ? $manifest['settings'] : [];
        $manifest['seo'] = is_array($manifest['seo'] ?? null) ? $manifest['seo'] : [];
        $manifest['preview'] = $manifest['preview'] ?? (is_file($path.'/preview.webp') ? 'preview.webp' : null);

        return $manifest;
    }

    /**
     * Compact lists such as ["light", "dark"] are accepted and converted to
     * keyed empty definitions. Object definitions remain unchanged.
     *
     * @param  array<int|string, mixed>  $value
     * @param  array<int, string>  $errors
     * @return array<string, array<string, mixed>>
     */
    private function normaliseDefinitions(array $value, string $field, array &$errors, bool $allowCompact = true): array
    {
        if ($value === []) {
            return [];
        }

        if (array_is_list($value)) {
            if (! $allowCompact && $field === 'variants') {
                // Older Theme Builder Phase 1 builds incorrectly wrote accent names
                // to variants. Ignore that list while preserving object-style variants.
                return [];
            }

            $normalised = [];
            foreach ($value as $name) {
                if (! is_string($name) || ! preg_match('/^[a-z0-9][a-z0-9_-]*$/', $name)) {
                    $errors[] = "Every {$field} entry must be a valid lowercase key.";

                    continue;
                }
                $normalised[$name] = [];
            }

            return $normalised;
        }

        $normalised = [];
        foreach ($value as $name => $definition) {
            if (! is_string($name) || ! preg_match('/^[a-z0-9][a-z0-9_-]*$/', $name) || ! is_array($definition)) {
                $errors[] = "Every {$field} definition must use a valid lowercase key and an object value.";

                continue;
            }
            $normalised[$name] = $definition;
        }

        return $normalised;
    }

    /**
     * @param  array<int|string, mixed>  $value
     * @param  array<int, string>  $errors
     * @return array<string, bool>
     */
    private function normaliseCapabilities(array $value, array &$errors): array
    {
        $normalised = [];

        foreach ($value as $name => $enabled) {
            if (! is_string($name) || ! preg_match('/^[a-z0-9][a-z0-9_-]*$/', $name) || ! is_bool($enabled)) {
                $errors[] = 'Every capability must use a valid lowercase key and a boolean value.';

                continue;
            }

            $normalised[$name] = $enabled;
        }

        return $normalised;
    }

    private function isSafeRelativePath(mixed $path): bool
    {
        return is_string($path) && $path !== '' && ! str_starts_with($path, '/') && ! str_contains($path, '..') && ! str_contains($path, "\0");
    }
}