SilentDragonPaper/lib/src/pdf.rs

extern crate printpdf;

use crate::paper::params;

use qrcode::QrCode;
use qrcode::types::Color;

use std::io::BufWriter;
use std::convert::From;
use std::f64;
use std::fs::File;
use printpdf::*;


/**
 * Save the list of wallets (address + private keys) to the given PDF file name.
 */
pub fn save_to_pdf(addresses: &str, filename: &str) -> Result<(), String> {
    let (doc, page1, layer1) = PdfDocument::new("SilentDragonPaper Wallet", Mm(210.0), Mm(297.0), "Layer 1");

    let font  = doc.add_builtin_font(BuiltinFont::Courier).unwrap();
    let font_bold = doc.add_builtin_font(BuiltinFont::CourierBold).unwrap();

    let keys = json::parse(&addresses).unwrap();

    // Position on the PDF page.
    let mut pos = 0;

    let mut current_layer = doc.get_page(page1).get_layer(layer1);
    
    let total_pages      = f64::ceil(keys.len() as f64 / 1.0);   // 1 per page
    let mut current_page = 1; 

    for kv in keys.members() {
        // Add next page when moving to the next position.
        if pos >= 1 {
            pos = 0;
            current_page = current_page + 1;

            // Add a page
            let (page2, _) = doc.add_page(Mm(210.0), Mm(297.0),"Page 2, Layer 1");
            current_layer = doc.get_page(page2).add_layer("Layer 3");
        }

        let address  = kv["address"].as_str().unwrap();
        let pk       = kv["private_key"].as_str().unwrap();
        let is_taddr = !address.starts_with(&params().zaddress_prefix);

        let (seed, hdpath) = if kv["type"].as_str().unwrap() == "zaddr" && kv.contains("seed") {
            (kv["seed"]["HDSeed"].as_str().unwrap(), kv["seed"]["path"].as_str().unwrap())
        } else {
            ("", "")
        };

        // Add address + private key
        add_address_to_page(&current_layer, &font, &font_bold, address, is_taddr, pos);
        add_pk_to_page(&current_layer, &font, &font_bold, pk, address, is_taddr, seed, hdpath, pos);
 
        let line1 = Line {
            points: vec![(Point::new(Mm(5.0), Mm(98.0)), false), (Point::new(Mm(205.0), Mm(98.0)), false)],
            is_closed: true,
            has_fill: false,
            has_stroke: true,
            is_clipping_path: false,
        };

	    let line2 = Line {
            points: vec![(Point::new(Mm(5.0), Mm(198.0)), false), (Point::new(Mm(205.0), Mm(198.0)), false)],
            is_closed: true,
            has_fill: false,
            has_stroke: true,
            is_clipping_path: false,
        };

        let outline_color = printpdf::Color::Rgb(Rgb::new(0.0, 0.0, 0.0, None));

        current_layer.set_outline_color(outline_color);
        current_layer.set_outline_thickness(2.0);

        // Set title
        current_layer.use_text("Speak and Transact Freely", 32f64, Mm(19.0), Mm(277.0), &font_bold);
        current_layer.use_text("Private Cryptocurrency and Messenger on Zero Knowledge Proof Encryption", 13f64, Mm(7.0), Mm(266.0), &font_bold);

        // Draw lines
        current_layer.add_shape(line1);
        current_layer.add_shape(line2);

        // Add footer of page, only once for each pair of addresses
        if pos == 0 {
            add_footer_to_page(&current_layer, &font, &format!("Page {} of {}", current_page, total_pages));
        }

        // Add to the position to move to the next set, but remember to add a new page every 2 wallets
        // We'll add a new page at the start of the loop, so we add it to the PDF only if required.
        pos = pos + 1;        
    };
    
    let file = match File::create(filename) {
        Ok(f)  => f,
        Err(e) => {            
            return Err(format!("Couldn't open {} for writing. Aborting. {}", filename, e));
        }
    };

    match doc.save(&mut BufWriter::new(file)) {
        Ok(_)   => (),
        Err(e)  => {
            return Err(format!("Couldn't save {}. Aborting. {}", filename, e));
        }
    };

    return Ok(());
}

/**
 * Generate a qrcode. The outout is a vector of RGB values of size (qrcode_modules * scalefactor) + padding
 */
fn qrcode_scaled(data: &str, scalefactor: usize) -> (Vec<u8>, usize) {
    let code = QrCode::new(data.as_bytes()).unwrap();
    let output_size = code.width();

    let imgdata = code.to_colors();

    // Add padding around the QR code, otherwise some scanners can't seem to read it. 
    let padding     = 10;
    let scaledsize  = output_size * scalefactor;
    let finalsize   = scaledsize + (2 * padding);

    // Build a scaled image
    let scaledimg: Vec<u8> = (0..(finalsize*finalsize)).flat_map( |i| {
        let x = i / finalsize;
        let y = i % finalsize;
        if x < padding || y < padding || x >= (padding+scaledsize) || y >= (padding+scaledsize) {
            vec![255u8; 3]
        } else {
            if imgdata[(x - padding)/scalefactor * output_size + (y - padding)/scalefactor] != Color::Light {vec![0u8; 3] } else { vec![255u8; 3] }
        }
    }).collect();

    return (scaledimg, finalsize);
}

/**
 * Add a footer at the bottom of the page
 */
fn add_footer_to_page(current_layer: &PdfLayerReference, font: &IndirectFontRef, footer: &str) {
    current_layer.use_text(footer, 10f64, Mm(5.0), Mm(5.0), &font);
}


/**
 * Add the address section to the PDF at `pos`. Note that each page can fit only 2 wallets, so pos has to effectively be either 0 or 1.
 */
fn add_address_to_page(current_layer: &PdfLayerReference, font: &IndirectFontRef, font_bold: &IndirectFontRef, address: &str, is_taddr: bool, pos: u32) {
    let (scaledimg, finalsize) = qrcode_scaled(address, if is_taddr {13} else {10});

    //         page_height  top_margin  vertical_padding  position               
    let ypos = 297.0        - 5.0       - 77.0            - (140.0 * pos as f64);
    let title = if is_taddr {"HUSH t-address"} else {"HUSH z-address"};

    add_address_at(current_layer, font, font_bold, title, address, &scaledimg, finalsize, ypos);
}

fn add_address_at(current_layer: &PdfLayerReference, font: &IndirectFontRef, font_bold: &IndirectFontRef, title: &str, address: &str, qrcode: &Vec<u8>, finalsize: usize, ypos: f64) {
    add_qrcode_image_to_page(current_layer, qrcode, finalsize, Mm(10.0), Mm(ypos));
    current_layer.use_text(title, 14f64, Mm(55.0), Mm(ypos+22.5), &font_bold);
    
    let strs = split_to_max(&address, 39, 39);  // No spaces, so user can copy the address
    for i in 0..strs.len() {
        current_layer.use_text(strs[i].clone(), 12f64, Mm(55.0), Mm(ypos+15.0-((i*5) as f64)), &font);
    }
}

/**
 * Add the private key section to the PDF at `pos`, which can effectively be only 0 or 1.
 */
fn add_pk_to_page(current_layer: &PdfLayerReference, font: &IndirectFontRef, font_bold: &IndirectFontRef, pk: &str, address: &str, is_taddr: bool, seed: &str, path: &str, pos: u32) {
    //         page_height  top_margin  vertical_padding  position               
    let ypos = 297.0        - 5.0       - 242.0           - (140.0 * pos as f64);
    
    let (scaledimg, finalsize) = qrcode_scaled(pk, if is_taddr {20} else {10});

    add_qrcode_image_to_page(current_layer, &scaledimg, finalsize, Mm(145.0), Mm(ypos-17.5));

    current_layer.use_text("Private Key", 14f64, Mm(10.0), Mm(ypos+37.5), &font_bold);
    let strs = split_to_max(&pk, 45, 45);   // No spaces, so user can copy the private key
    for i in 0..strs.len() {
        current_layer.use_text(strs[i].clone(), 12f64, Mm(10.0), Mm(ypos+32.5-((i*5) as f64)), &font);
    }

    // Add the address a second time below the private key
    let title = if is_taddr {"HUSH t-address"} else {"HUSH z-address"};
    current_layer.use_text(title, 12f64, Mm(10.0), Mm(ypos-10.0), &font_bold);    
    let strs = split_to_max(&address, 39, 39);  // No spaces, so user can copy the address
    for i in 0..strs.len() {
        current_layer.use_text(strs[i].clone(), 12f64, Mm(10.0), Mm(ypos-15.0-((i*5) as f64)), &font);
    }

    // And add the seed too. 
    if !seed.is_empty() {
        current_layer.use_text(format!("HDSeed: {}, Path: {}", seed, path).as_str(), 8f64, Mm(10.0), Mm(ypos-35.0), &font);
    }
}

/**
 * Insert the given QRCode into the PDF at the given x,y co-ordinates. The qr code is a vector of RGB values. 
 */
fn add_qrcode_image_to_page(current_layer: &PdfLayerReference, qr: &Vec<u8>, qrsize: usize, x: Mm, y: Mm) {
    // you can also construct images manually from your data:
    let image_file_2 = ImageXObject {
            width: Px(qrsize),
            height: Px(qrsize),
            color_space: ColorSpace::Rgb,
            bits_per_component: ColorBits::Bit8,
            interpolate: true,
            /* put your bytes here. Make sure the total number of bytes =
            width * height * (bytes per component * number of components)
            (e.g. 2 (bytes) x 3 (colors) for RGB 16bit) */
            image_data: qr.to_vec(),
            image_filter: None, /* does not work yet */
            clipping_bbox: None, /* doesn't work either, untested */
    };
    
    let image2 = Image::from(image_file_2);
    image2.add_to_layer(current_layer.clone(), Some(x), Some(y), None, None, None, None);
}

/**
 * Split a string into multiple lines, each with a `max` length and add spaces in each line at `blocksize` intervals
 */
fn split_to_max(s: &str, max: usize, blocksize: usize) -> Vec<String> {
    let mut ans: Vec<String> = Vec::new();

    // Split into lines. 
    for i in 0..((s.len() / max)+1) {
        let start = i * max;
        let end   = if start + max > s.len() { s.len() } else { start + max };

        let line = &s[start..end];

        // Now, add whitespace into the individual lines to better readability.
        let mut spaced_line = String::default();
        for j in 0..((line.len() / blocksize)+1) {
            let start = j * blocksize;
            let end   = if start + blocksize > line.len() {line.len()} else {start + blocksize};

            spaced_line.push_str(" ");
            spaced_line.push_str(&line[start..end]);
        }

        // If there was nothing to split in the blocks, just add the whole line
        if spaced_line.is_empty() {
            spaced_line = line.to_string();
        }

        ans.push(spaced_line.trim().to_string());
    }

    // Add spaces
    return ans;
}