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// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at https://mozilla.org/MPL/2.0/.

use std::fs::File;
use std::time::Duration;
use ast::{Defs, Def, Expr, DefEntry};
use std::io::Read;
use std::rc::Rc;
use json;

static URL: &'static str = "https://blockchain.info/stats?format=json";

pub fn parse(mut f: File) -> Result<Defs, String> {
    let mut buf = String::new();
    try!(f.read_to_string(&mut buf).map_err(|x| format!("{}", x)));
    let parsed = try!(json::parse(&*buf).map_err(|x| format!("{}", x)));
    let mut out = vec![];
    if let Some(price) = parsed["market_price_usd"].as_number() {
        let (sign, mantissa, exp) = price.as_parts();
        let integer = format!("{}{}", if sign { "" } else { "-" }, mantissa);
        if let Ok(price) = ::Number::from_parts(&*integer, None, Some(&*format!("{}", exp))) {
            out.push(DefEntry {
                name: "BTC".to_owned(),
                def: Rc::new(Def::Unit(
                    Expr::Mul(vec![
                        Expr::Const(price),
                        Expr::Unit("USD".to_owned())
                    ]))),
                doc: Some(format!("Sourced from blockchain.info.")),
                category: Some("currencies".to_owned()),
            });
        }
    }
    Ok(Defs {
        defs: out
    })
}

pub fn load() -> Result<Defs, String> {
    ::cached("btc.json", URL, Duration::from_secs(3*60*60)).and_then(parse)
}