justjp2 0.1.1

pub mod bio;
pub mod dwt;
pub mod error;
pub mod htj2k;
pub mod j2k;
pub mod jp2;
pub mod jp2_box;
pub mod marker;
pub mod mct;
pub mod mqc;
pub mod pi;
pub mod quantize;
pub mod simd;
pub mod stream;
pub mod t1;
pub mod t2;
pub mod tgt;
pub mod tcd;
pub mod types;

// ── Phase 11: Public API ──

pub use error::{Jp2Error, Result};
pub use types::CodecFormat;

use tcd::{TcdComponent, TcdParams};

/// An image with one or more components.
#[derive(Debug, Clone)]
pub struct Image {
    pub width: u32,
    pub height: u32,
    pub components: Vec<Component>,
}

/// A single image component.
#[derive(Debug, Clone)]
pub struct Component {
    pub data: Vec<i32>,
    pub width: u32,
    pub height: u32,
    pub precision: u32,
    pub signed: bool,
    pub dx: u32,
    pub dy: u32,
}

/// Encoding parameters.
#[derive(Debug, Clone)]
pub struct EncodeParams {
    pub lossless: bool,
    pub num_decomp_levels: u32,
    pub cblk_width: u32,
    pub cblk_height: u32,
    pub format: CodecFormat,
}

impl Default for EncodeParams {
    fn default() -> Self {
        Self {
            lossless: true,
            num_decomp_levels: 5,
            cblk_width: 64,
            cblk_height: 64,
            format: CodecFormat::Jp2,
        }
    }
}

/// Decode a JPEG 2000 file (auto-detects J2K vs JP2 format).
pub fn decode(data: &[u8]) -> Result<Image> {
    decode_with_reduce(data, 0)
}

/// Decode a JPEG 2000 file at a reduced resolution.
///
/// # Arguments
/// * `data` - The encoded JPEG 2000 data
/// * `reduce` - Number of resolution levels to discard (0 = full resolution)
pub fn decode_with_reduce(data: &[u8], reduce: u32) -> Result<Image> {
    if data.len() < 4 {
        return Err(Jp2Error::InvalidData(
            "data too short to detect format".to_string(),
        ));
    }

    let format = detect_format(data)?;

    let (components_data, comp_info) = match format {
        CodecFormat::Jp2 => {
            if reduce > 0 {
                // For JP2, extract the J2K codestream and decode with reduce
                // For now, only J2K format supports reduce directly
                jp2::jp2_decode(data)?
            } else {
                jp2::jp2_decode(data)?
            }
        }
        CodecFormat::J2k => j2k::j2k_decode_with_reduce(data, reduce)?,
    };

    // Derive image dimensions from the first component (reference grid)
    let width = comp_info[0].width;
    let height = comp_info[0].height;

    let components = components_data
        .into_iter()
        .zip(comp_info.iter())
        .map(|(data, ci)| Component {
            data,
            width: ci.width,
            height: ci.height,
            precision: ci.precision,
            signed: ci.signed,
            dx: ci.dx,
            dy: ci.dy,
        })
        .collect();

    Ok(Image {
        width,
        height,
        components,
    })
}

/// Decode only a specific rectangular region of the image.
///
/// The region is specified in pixel coordinates: (x0, y0) is the top-left
/// corner (inclusive) and (x1, y1) is the bottom-right corner (exclusive).
///
/// Returns an `Image` containing only the requested region.
///
/// # Errors
/// Returns an error if the region is invalid (empty, or extends beyond the
/// image bounds) or if the underlying decode fails.
pub fn decode_region(data: &[u8], x0: u32, y0: u32, x1: u32, y1: u32) -> Result<Image> {
    if x0 >= x1 || y0 >= y1 {
        return Err(Jp2Error::InvalidData(
            "decode_region: empty region (x0 >= x1 or y0 >= y1)".to_string(),
        ));
    }

    // Decode the full image first, then crop.
    let full = decode(data)?;

    if x1 > full.width || y1 > full.height {
        return Err(Jp2Error::InvalidData(format!(
            "decode_region: region ({x0},{y0})-({x1},{y1}) exceeds image bounds {}x{}",
            full.width, full.height
        )));
    }

    let region_w = x1 - x0;
    let region_h = y1 - y0;

    let components = full
        .components
        .iter()
        .map(|comp| {
            // Handle sub-sampled components: adjust region coordinates by dx/dy
            let cx0 = x0 / comp.dx;
            let cy0 = y0 / comp.dy;
            let cx1 = ((x1 + comp.dx - 1) / comp.dx).min(comp.width);
            let cy1 = ((y1 + comp.dy - 1) / comp.dy).min(comp.height);
            let cw = cx1 - cx0;
            let ch = cy1 - cy0;

            let mut region_data = vec![0i32; (cw * ch) as usize];
            for y in 0..ch {
                for x in 0..cw {
                    let src_idx = ((cy0 + y) * comp.width + (cx0 + x)) as usize;
                    let dst_idx = (y * cw + x) as usize;
                    region_data[dst_idx] = comp.data[src_idx];
                }
            }

            Component {
                data: region_data,
                width: cw,
                height: ch,
                precision: comp.precision,
                signed: comp.signed,
                dx: comp.dx,
                dy: comp.dy,
            }
        })
        .collect();

    Ok(Image {
        width: region_w,
        height: region_h,
        components,
    })
}

/// Encode an image as JPEG 2000.
pub fn encode(image: &Image, params: &EncodeParams) -> Result<Vec<u8>> {
    if image.components.is_empty() {
        return Err(Jp2Error::InvalidData(
            "image has no components".to_string(),
        ));
    }

    let comp_info: Vec<TcdComponent> = image
        .components
        .iter()
        .map(|c| TcdComponent {
            width: c.width,
            height: c.height,
            precision: c.precision,
            signed: c.signed,
            dx: c.dx,
            dy: c.dy,
        })
        .collect();

    let components_data: Vec<Vec<i32>> = image
        .components
        .iter()
        .map(|c| c.data.clone())
        .collect();

    let use_mct = image.components.len() >= 3;

    let tcd_params = TcdParams {
        num_res: params.num_decomp_levels + 1,
        cblk_w: params.cblk_width,
        cblk_h: params.cblk_height,
        reversible: params.lossless,
        num_layers: 1,
        use_mct,
        reduce: 0,
        max_bytes: None,
    };

    match params.format {
        CodecFormat::Jp2 => jp2::jp2_encode(&components_data, &comp_info, &tcd_params),
        CodecFormat::J2k => j2k::j2k_encode(&components_data, &comp_info, &tcd_params),
    }
}

/// Auto-detect whether data is JP2 or raw J2K.
fn detect_format(data: &[u8]) -> Result<CodecFormat> {
    if data.len() < 4 {
        return Err(Jp2Error::InvalidData(
            "data too short to detect format".to_string(),
        ));
    }

    // Check for JP2: first 4 bytes are a box length (typically 0x0000000C = 12),
    // followed by the JP2 signature box type 0x6A502020.
    if data.len() >= 12 {
        let box_type = u32::from_be_bytes([data[4], data[5], data[6], data[7]]);
        if box_type == jp2_box::JP2_JP {
            return Ok(CodecFormat::Jp2);
        }
    }

    // Check for raw J2K: starts with SOC marker 0xFF4F
    if data[0] == 0xFF && data[1] == 0x4F {
        return Ok(CodecFormat::J2k);
    }

    Err(Jp2Error::InvalidData(
        "unrecognized format: not JP2 or J2K".to_string(),
    ))
}