use std::{env, io};
use std::fs;
use std::path::Path;
use std::process::Command;

use hex_literal::hex;
use sha2::{Digest, Sha512};

fn main() {

    // Do not fetch lib on docs.rs as it cannot, build will fail, docs won't build
    // https://docs.rs/about/builds
    if std::env::var("DOCS_RS").is_err() {
        let out_dir = env::var_os("OUT_DIR").unwrap();
        println!("cargo:rustc-flags=-L {}", out_dir.to_str().unwrap());
        println!("cargo:rustc-link-lib=Cwtch");

        println!("cargo:rerun-if-changed=build.rs");
        println!("cargo:rerun-if-changed=libCwtch.h");

        let lib_cwtch_path = Path::new(&out_dir).join("libCwtch.so");
        if std::env::var("LCG_DIR").is_err() {
            // https://git.openprivacy.ca/cwtch.im/libcwtch-go/releases v1.7.1
            Command::new("wget")
                .arg("https://git.openprivacy.ca/attachments/5fa8e7f5-13c2-4634-b531-0398cd7c6353")
                .arg("-O")
                .arg(lib_cwtch_path.clone())
                .output()
                .expect("failed to download libCwtch.so");

            let mut hasher = Sha512::new();
            let mut file = fs::File::open(&lib_cwtch_path).expect("could not open lib to hash");
            io::copy(&mut file, &mut hasher).expect("failed to copy file into hasher");
            let hash_bytes = hasher.finalize();

            assert_eq!(hash_bytes[..], hex!("dc53eb4948357128a72f740cf48402e966e886c60bc150bd26d10d3c98dda64c3658322c15f3b93781365d40dd4315b1056fb9aa6ee3a56f8968d4bff1bc8f0d")[..]);
        } else {
            let local_lcg = Path::new(std::env::var("LCG_DIR").unwrap().as_str()).join("libCwtch.so");
            fs::copy(local_lcg, lib_cwtch_path).expect("could not find local lcg");
        }
    }
}