pdf-rs 0.1.7-dev

use crate::catalog::NodeId;
use crate::document::PDFDocument;
use crate::error::PDFError::{ContentStreamTypeError, PageNotFound};
use crate::error::Result;
use crate::filter::decode_stream;
use crate::objects::{PDFObject, Stream};

/// Extracts content streams from a specific page in the PDF document.
///
/// This function retrieves all content streams associated with a page,
/// which contain the graphical and textual content to be rendered.
///
/// # Arguments
///
/// * `document` - A mutable reference to the PDF document
/// * `page_id` - The ID of the page to extract content from
///
/// # Returns
///
/// A `Result` containing a vector of `Stream` objects representing the page's content,
/// or an error if the page is not found or the content stream type is invalid
fn extract_page_content_stream(document: &mut PDFDocument, page_id: NodeId) -> Result<Vec<Stream>> {
    let page = match document.get_page(page_id) {
        Some(page) => page,
        None => return Err(PageNotFound(format!("Page not found:{}", page_id))),
    };
    let contents = page.get_contents();
    let mut streams = Vec::new();
    for tuple in contents {
        match document.read_object_with_ref(tuple)? {
            Some(PDFObject::IndirectObject(_, _, obj)) => match *obj {
                PDFObject::Stream(stream) => streams.push(stream),
                _ => return Err(ContentStreamTypeError)
            }
            _ => return Err(ContentStreamTypeError)
        }
    }
    Ok(streams)
}

/// Extracts text content from a specific page in the PDF document.
///
/// This function retrieves and processes the text content from a page's content streams.
/// Currently returns an empty string as a placeholder for future text extraction implementation.
///
/// # Arguments
///
/// * `document` - A mutable reference to the PDF document
/// * `page_id` - The ID of the page to extract text from
///
/// # Returns
///
/// A `Result` containing an optional string with the extracted text,
/// or an error if the page cannot be accessed
pub fn extract_page_text(document: &mut PDFDocument, page_id: NodeId) -> Result<Option<String>> {
    let streams = extract_page_content_stream(document, page_id)?;
    for stream in streams {
        let text = decode_stream(&stream)?;
    }
    Ok(Some(String::new()))
}