//! Export: a self-contained HTML page with every view prerendered, or one
//! view as a standalone SVG file.

use crate::assets;
use crate::Project;
use isokit_core::fmt::esc;
use isokit_script::ScriptError;
use serde_json::{json, Value};

/// JSON safe to put inside `<script type="application/json">`.
fn script_json(v: &Value) -> String {
    v.to_string().replace("</", "<\\/")
}

/// The static page: all levels in all four rotations, no server needed.
pub fn static_page(p: &Project) -> Result<String, ScriptError> {
    let meta = p.meta();
    let mut views = serde_json::Map::new();
    for l in &meta.levels {
        for rot in 0..4u8 {
            let v = p.render(&l.id, rot, None, false)?;
            views.insert(
                format!("{}/{rot}", l.id),
                json!({ "html": v.html, "info": v.info, "bbox": v.bbox, "focus": v.focus, "north": v.north, "boxes": v.boxes }),
            );
        }
    }
    let data = json!({
        "meta": {
            "title": meta.title, "note": meta.note, "levels": meta.levels,
            "defaultLevel": meta.default_level, "defaultRotation": meta.default_rotation
        },
        "views": views,
        "cfg": p.cfg(None),
        "animation": p.manifest.build.animation,
    });
    let css = format!(
        "{}\n{}",
        assets::get("viewer/isokit-view.css").unwrap_or_default(),
        p.theme.css()
    );
    let page = assets::get("viewer/page.html").unwrap_or_default();
    Ok(page
        .replace("{{title}}", &esc(&meta.title))
        .replace("{{date}}", &today())
        .replace("/*ISOKIT_CSS*/", &css)
        .replace("/*ISOKIT_DATA*/", &script_json(&data))
        .replace(
            "/*ISOKIT_JS*/",
            &assets::get("viewer/isokit-view.js").unwrap_or_default(),
        ))
}

/// One view as a standalone SVG (dark or light scheme, styles inlined).
pub fn svg(p: &Project, level: &str, rot: u8, light: bool) -> Result<String, ScriptError> {
    let v = p.render(level, rot, None, false)?;
    let css = format!(
        "{}\n{}",
        assets::get("viewer/isokit-view.css").unwrap_or_default(),
        p.theme.css_scoped("svg.iso-svg", Some(light))
    );
    let b = v.bbox;
    let bg = if light { "#e8f4ff" } else { "#0b1428" };
    Ok(format!(
        "<svg xmlns=\"http://www.w3.org/2000/svg\" class=\"iso-svg\" viewBox=\"{} {} {} {}\" width=\"{}\" height=\"{}\">\
         <style>{}</style><rect x=\"{}\" y=\"{}\" width=\"{}\" height=\"{}\" fill=\"{bg}\"/>{}</svg>\n",
        b[0], b[1], b[2], b[3], (b[2] * 2.0).round(), (b[3] * 2.0).round(), css, b[0], b[1], b[2], b[3], v.html
    ))
}

/// Today's date (UTC) as YYYY-MM-DD, without a date crate.
pub fn today() -> String {
    // web_time: std's clock traps in the browser (wasm32-unknown-unknown)
    let secs = web_time::SystemTime::now()
        .duration_since(web_time::UNIX_EPOCH)
        .map(|d| d.as_secs())
        .unwrap_or(0);
    let days = (secs / 86_400) as i64;
    // civil-from-days (H. Hinnant)
    let z = days + 719_468;
    let era = z.div_euclid(146_097);
    let doe = z - era * 146_097;
    let yoe = (doe - doe / 1460 + doe / 36_524 - doe / 146_096) / 365;
    let y = yoe + era * 400;
    let doy = doe - (365 * yoe + yoe / 4 - yoe / 100);
    let mp = (5 * doy + 2) / 153;
    let d = doy - (153 * mp + 2) / 5 + 1;
    let m = if mp < 10 { mp + 3 } else { mp - 9 };
    format!("{:04}-{:02}-{:02}", if m <= 2 { y + 1 } else { y }, m, d)
}