use crate::qr::QrCode;

pub fn render_svg(qr: &QrCode, logo: Option<&[u8]>, fg: &[u8; 3], bg: &[u8; 3]) -> String {
    let matrix_size = qr.size() as u32;
    let margin = qr.margin as u32;
    let total = matrix_size + 2 * margin;

    let fg_hex = format!("#{:02X}{:02X}{:02X}", fg[0], fg[1], fg[2]);
    let bg_hex = format!("#{:02X}{:02X}{:02X}", bg[0], bg[1], bg[2]);

    let dark_count = qr
        .modules()
        .iter()
        .flat_map(|row| row.iter())
        .filter(|&&m| m)
        .count();
    let mut svg = String::with_capacity(300 + dark_count * 50);
    svg.push_str(&format!(
        r#"<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="{total}" height="{total}" viewBox="0 0 {total} {total}">"#
    ));
    svg.push_str(&format!(
        r#"<rect width="{total}" height="{total}" fill="{bg_hex}"/>"#
    ));

    for y in 0..matrix_size {
        for x in 0..matrix_size {
            if qr.modules()[y as usize][x as usize] {
                svg.push_str(&format!(
                    r#"<rect x="{}" y="{}" width="1" height="1" fill="{fg_hex}"/>"#,
                    x + margin,
                    y + margin
                ));
            }
        }
    }

    // Logo 嵌入：base64 PNG data URL
    if let Some(logo_bytes) = logo {
        let b64 = base64_encode(logo_bytes);
        let logo_size = total as f32 * 0.25;
        let logo_x = (total as f32 - logo_size) / 2.0;
        let logo_y = (total as f32 - logo_size) / 2.0;
        svg.push_str(&format!(
            r#"<image x="{logo_x}" y="{logo_y}" width="{logo_size}" height="{logo_size}" xlink:href="data:image/png;base64,{b64}"/>"#
        ));
    }

    svg.push_str("</svg>");
    svg
}

/// 简易 base64 编码（无外部依赖）
fn base64_encode(data: &[u8]) -> String {
    const CHARS: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
    let mut result = String::with_capacity(data.len().div_ceil(3) * 4);
    for chunk in data.chunks(3) {
        let b0 = chunk[0] as u32;
        let b1 = if chunk.len() > 1 { chunk[1] as u32 } else { 0 };
        let b2 = if chunk.len() > 2 { chunk[2] as u32 } else { 0 };
        let triple = (b0 << 16) | (b1 << 8) | b2;
        result.push(CHARS[((triple >> 18) & 0x3F) as usize] as char);
        result.push(CHARS[((triple >> 12) & 0x3F) as usize] as char);
        if chunk.len() > 1 {
            result.push(CHARS[((triple >> 6) & 0x3F) as usize] as char);
        } else {
            result.push('=');
        }
        if chunk.len() > 2 {
            result.push(CHARS[(triple & 0x3F) as usize] as char);
        } else {
            result.push('=');
        }
    }
    result
}