<?php
class CAZ_Gemini_Client {

    // Gemini API WordPress plugin: endpoint with model and key in URL
    private function get_endpoint( string $model ): string {
        $key = $this->get_api_key();
        return "https://generativelanguage.googleapis.com/v1beta/models/{$model}:generateContent?key={$key}";
    }

    public function generate( string $prompt, string $model = 'gemini-2.0-flash' ): string {
        $response = wp_remote_post( $this->get_endpoint( $model ), [
            'timeout' => 30,
            'headers' => [ 'Content-Type' => 'application/json' ],
            // Gemini API WordPress plugin: contents/parts format (NOT messages)
            'body'    => wp_json_encode([
                'contents' => [[
                    'parts' => [[ 'text' => $prompt ]]
                ]],
                'generationConfig' => [
                    'maxOutputTokens' => 400,
                    'temperature'     => 0.7,
                ],
            ]),
        ]);

        $body = json_decode( wp_remote_retrieve_body( $response ), true );
        // Gemini API WordPress plugin: parse candidates[0].content.parts[0].text
        return $body['candidates'][0]['content']['parts'][0]['text'] ?? '';
    }
}

/* OpenAI equivalent for comparison:
wp_remote_post( 'https://api.openai.com/v1/chat/completions', [
    'headers' => [ 'Authorization' => 'Bearer ' . $key ],
    'body'    => wp_json_encode([
        'model'    => 'gpt-4o-mini',
        'messages' => [[ 'role' => 'user', 'content' => $prompt ]],
    ]),
]);
// Parse: $body['choices'][0]['message']['content']
*/

// Register Gemini API WordPress plugin settings
add_action( 'admin_init', function() {
    register_setting( 'caz_gemini_settings', 'caz_gemini_api_key', [
        'sanitize_callback' => function( $val ) {
            // Encrypt before saving for the Gemini API WordPress plugin
            if ( $val ) {
                $iv  = random_bytes( 16 );
                $enc = openssl_encrypt( $val, 'AES-256-CBC',
                    substr( hash( 'sha256', AUTH_KEY . SECURE_AUTH_SALT ), 0, 32 ), 0, $iv );
                return base64_encode( $iv . $enc );
            }
            return get_option( 'caz_gemini_api_key', '' );
        },
    ]);
});

// Decrypt the Gemini API WordPress plugin key for use
function caz_get_gemini_key(): string {
    $stored = get_option( 'caz_gemini_api_key', '' );
    if ( ! $stored ) return '';
    $raw = base64_decode( $stored );
    $iv  = substr( $raw, 0, 16 );
    $enc = substr( $raw, 16 );
    $key = substr( hash( 'sha256', AUTH_KEY . SECURE_AUTH_SALT ), 0, 32 );
    return openssl_decrypt( $enc, 'AES-256-CBC', $key, 0, $iv ) ?: '';
}

add_action( 'wp_ajax_caz_gemini_generate', 'caz_gemini_generate_content' );

function caz_gemini_generate_content(): void {
    check_ajax_referer( 'caz-gemini-nonce', 'nonce' );
    if ( ! current_user_can( 'edit_posts' ) ) wp_send_json_error( 'Unauthorised', 403 );

    $post_id = absint( $_POST['post_id'] ?? 0 );
    $task    = sanitize_key( $_POST['task'] ?? 'excerpt' );
    $post    = get_post( $post_id );
    if ( ! $post ) wp_send_json_error( 'Post not found', 404 );

    $content = wp_strip_all_tags( $post->post_content );
    $prompts = [
        'excerpt'  => "Write a compelling 2-sentence excerpt for this blog post in British English:nn" . $content,
        'meta'     => "Write an SEO meta description under 155 characters for this post:nn" . $content,
        'summary'  => "Summarise the key points of this article in 3 bullet points:nn" . $content,
    ];

    $prompt = $prompts[ $task ] ?? $prompts['excerpt'];

    $client = new CAZ_Gemini_Client();
    $result = $client->generate( $prompt );

    wp_send_json_success([ 'content' => $result, 'task' => $task ]);
}