<?php
class AIT_IAT_Prompt_Builder {
    public static function build_prompt($attachment_id, $seo_keyword = '', $context = '') {

        $language                 = AIT_IAT_Settings::get('default_language') ?: 'en';
        $style                    = AIT_IAT_Settings::get('alt_text_style');
        $min_length               = intval(AIT_IAT_Settings::get('min_alt_text_length'));
        $max_length               = intval(AIT_IAT_Settings::get('max_alt_text_length'));
        $template                 = AIT_IAT_Settings::get('alt_text_prompt_template');
        $duplicate_detection      = AIT_IAT_Settings::get('enable_duplicate_detection');
        $blocklist_keywords       = AIT_IAT_Settings::get('blocklist_keywords');

        $additional_fields        = (array) AIT_IAT_Settings::get( 'additional_generation_fields' );
        $rename_awkward_filenames = (bool) AIT_IAT_Settings::get( 'rename_awkward_filenames' );

        switch ( $style ) {
            case 'seo':
                $desc = "in an SEO-optimized manner";
                break;
            case 'formal':
                $desc = "in a formal tone";
                break;
            case 'casual':
                $desc = "in a friendly, casual tone";
                break;
            case 'descriptive':
            default:
                $desc = "in a clear, descriptive manner";
                break;
        }

        // Fallback template if the user hasn't customised it.
        $template        = $template ?: __( 'Describe this image %1$s in %2$s. Use between %3$d and %4$d characters.', 'ai-image-alt-text' );
        $alt_instruction = sprintf( $template, $desc, $language, $min_length, $max_length );

        // -----------------------------------------------------------------
        // JSON response instructions
        // -----------------------------------------------------------------
        $prompt  = "You are generating structured JSON metadata for an image used in a WordPress website.\n\n";
        $prompt .= "Respond with ONLY a single valid JSON object. Do not include any backticks, code fences, or explanations.\n";
        $prompt .= "Use double quotes for all keys and string values.\n\n";

        // Required field
        $prompt .= "The JSON object MUST always include this key:\n";
        $prompt .= "- \"alt_text\": string – {$alt_instruction}\n\n";

        if ( ! empty( $additional_fields ) or ! empty( $rename_awkward_filenames ) ) {
            $prompt .= "Also include these additional keys:\n";
        }

        if ( in_array( 'caption', $additional_fields, true ) ) {
            $prompt .= "- \"caption\": string – a short human-friendly caption suitable for display directly under the image.\n";
        }

        if ( in_array( 'title', $additional_fields, true ) ) {
            $prompt .= "- \"title\": string – a concise, meaningful title for the image, suitable for the WordPress attachment title.\n";
        }

        if ( in_array( 'description', $additional_fields, true ) ) {
            $prompt .= "- \"description\": string – a slightly longer description of the image, suitable for the WordPress attachment description.\n";
        }

        if ( $rename_awkward_filenames ) {
            $prompt .= "- \"filename\": string – a short, human-readable, lowercase, hyphen-separated file name, without the file extension (for example: \"golden-retriever-puppy-playing\").\n";
        }

        $prompt .= "\nOnly include the keys listed above. Do not invent additional keys.\n";

        if ( ! empty( $seo_keyword ) ) {
            $prompt .= "\n\n" . sprintf( ' The SEO keyword for the overall post is %s.', $seo_keyword );
            $prompt .= " Where possible, naturally incorporate this keyword into the generated text fields without keyword stuffing.";
        }

        if ( $duplicate_detection ) {
            $other_alts = self::get_other_image_alts_on_same_page( $attachment_id );
        
            if ( ! empty( $other_alts ) ) {
                $prompt .= "\n\n";
                $prompt .= "Here are the alt-texts of other images on the same page:\n";
        
                foreach ( $other_alts as $other_alt ) {
                    // Keep it short & safe for the prompt.
                    $prompt .= '- ' . $other_alt . "\n";
                }
        
                $prompt .= "When generating the alt_text for this image, make sure it is clearly distinct from these.\n";
                $prompt .= "Do not repeat the same phrasing or produce alt_text that is so similar that it looks like a duplicate.\n";
            }
        }

        if ( ! empty( $blocklist_keywords ) ) {
            $prompt .= "\n\n" . sprintf(
                ' DO NOT use any of the following words in any of the generated text fields: %s.',
                $blocklist_keywords
            );
        }

        $context = apply_filters( 'ait_iat_prompt_context', $context, (int) $attachment_id );

        if ( AIT_IAT_Settings::get( 'context_enabled' ) && ! empty( $context ) ) {
            $max_words        = intval( AIT_IAT_Settings::get( 'context_max_words' ) );
            $context_template = AIT_IAT_Settings::get( 'context_template' );
            $context_template = $context_template ?: __( ' Here is some additional context about the page where the image will be displayed: %s.', 'ai-image-alt-text' );

            $context_prompt = "\n\n" . sprintf(
                $context_template,
                self::trim_to_words( $context, $max_words )
            );

            $prompt .= $context_prompt;
        }

        return $prompt;
    }

    /**
     * Get alt-texts for other images on the same page as the current attachment.
     *
     * - Uses the attachment's parent post as the "page".
     * - Includes the featured image alt, if any.
     * - Includes alts for images in the post content.
     * - Excludes the current attachment's own alt.
     * - Deduplicates and limits the list to keep prompts reasonable.
     *
     * @param int $attachment_id
     * @return string[]
     */
    protected static function get_other_image_alts_on_same_page( $attachment_id ) {
        $attachment = get_post( $attachment_id );
        if ( ! $attachment || ! $attachment->post_parent ) {
            return [];
        }
    
        $post_id = (int) $attachment->post_parent;
        $alts    = [];
    
        // 1. Featured image alt.
        $featured_id = get_post_thumbnail_id( $post_id );
        if ( $featured_id && $featured_id !== $attachment_id ) {
            $featured_alt = get_post_meta( $featured_id, '_wp_attachment_image_alt', true );
            if ( $featured_alt ) {
                $alts[] = $featured_alt;
            }
        }
    
        // 2. Alts from images in the content.
        $content = get_post_field( 'post_content', $post_id );
        if ( $content && preg_match_all( '/<img[^>]+>/i', $content, $matches ) ) {
            foreach ( $matches[0] as $img_tag ) {
                $img_id = 0;
                $alt    = '';
    
                // Try to get attachment ID from class="... wp-image-123 ..."
                if ( preg_match( '/wp-image-([0-9]+)/', $img_tag, $m ) ) {
                    $img_id = (int) $m[1];
                }
    
                // Skip the current attachment.
                if ( $img_id && $img_id === (int) $attachment_id ) {
                    continue;
                }
    
                if ( $img_id ) {
                    $alt = get_post_meta( $img_id, '_wp_attachment_image_alt', true );
                }
    
                // Fallback: alt attribute in the HTML tag.
                if ( ! $alt && preg_match( '/alt=["\']([^"\']+)["\']/', $img_tag, $m_alt ) ) {
                    $alt = wp_strip_all_tags( $m_alt[1] );
                }
    
                if ( $alt ) {
                    $alts[] = $alt;
                }
            }
        }
    
        // Normalize: trim, remove empties, dedupe.
        $alts = array_values(
            array_unique(
                array_filter(
                    array_map( 'trim', $alts )
                )
            )
        );
    
        // Limit how many to include in the prompt (keep token usage sane).
        $max = 10;
        if ( count( $alts ) > $max ) {
            $alts = array_slice( $alts, 0, $max );
        }
    
        return $alts;
    }

    public static function trim_to_words( $string, $max_words ) {
        // Split the string into words
        $words = preg_split( '/\s+/', trim( $string ) );

        // If word count is within the limit, return original
        if ( count( $words ) <= $max_words ) {
            return $string;
        }

        // Take only the first $max_words and join them
        $trimmed = implode( ' ', array_slice( $words, 0, $max_words ) );

        // Add ellipsis or other indicator if you like
        return $trimmed . '...';
    }
}