rs-chunks 0.1.0

use std::io::{Cursor, Read};

fn open_cfb(bytes: &[u8]) -> Result<cfb::CompoundFile<Cursor<Vec<u8>>>, String> {
    cfb::CompoundFile::open(Cursor::new(bytes.to_vec()))
        .map_err(|e| format!("Cannot open .doc file (invalid CFB format): {e}"))
}

/// Reads the "WordDocument" stream from the CFB container (from raw file bytes).
/// Returns raw bytes; caller parses the FIB from these bytes.
pub fn read_word_document_stream(bytes: &[u8]) -> Result<Vec<u8>, String> {
    let mut compound = open_cfb(bytes)?;
    let mut buf = Vec::new();
    compound
        .open_stream("/WordDocument")
        .map_err(|_| "Missing WordDocument stream — not a valid .doc file".to_string())?
        .read_to_end(&mut buf)
        .map_err(|e| format!("Failed to read WordDocument stream: {e}"))?;
    Ok(buf)
}

/// Reads the table stream ("0Table" or "1Table") chosen by `which` (0 or 1).
pub fn read_table_stream(bytes: &[u8], which: u8) -> Result<Vec<u8>, String> {
    let stream_name = if which == 1 { "/1Table" } else { "/0Table" };
    let mut compound = open_cfb(bytes)?;
    let mut buf = Vec::new();
    compound
        .open_stream(stream_name)
        .map_err(|_| format!("Missing {stream_name} stream — not a valid .doc file"))?
        .read_to_end(&mut buf)
        .map_err(|e| format!("Failed to read {stream_name}: {e}"))?;
    Ok(buf)
}

/// Reads the optional "Data" stream, which stores inline picture data (PICF
/// structures referenced by sprmCPicLocation). Returns `None` when the
/// stream is absent — a document without inline pictures is not an error.
pub fn read_data_stream(bytes: &[u8]) -> Result<Option<Vec<u8>>, String> {
    let mut compound = open_cfb(bytes)?;
    let mut stream = match compound.open_stream("/Data") {
        Ok(s) => s,
        Err(_) => return Ok(None),
    };
    let mut buf = Vec::new();
    stream
        .read_to_end(&mut buf)
        .map_err(|e| format!("Failed to read Data stream: {e}"))?;
    Ok(Some(buf))
}