use std::env;
use std::ops::Bound;
use std::path::PathBuf;

fn get_env_var(name: &str) -> String {
    match env::var(name) {
        Ok(val) => val,
        Err(env::VarError::NotPresent) => String::new(),
        Err(err) => panic!("cannot get {}: {}", name, err),
    }
}

pub fn probe_lua() -> PathBuf {
    let include_dir = get_env_var("LUA_INC");
    let lib_dir = get_env_var("LUA_LIB");
    let lua_lib = get_env_var("LUA_LIB_NAME");

    println!("cargo:rerun-if-env-changed=LUA_INC");
    println!("cargo:rerun-if-env-changed=LUA_LIB");
    println!("cargo:rerun-if-env-changed=LUA_LIB_NAME");
    println!("cargo:rerun-if-env-changed=LUA_LINK");

    let need_lua_lib = cfg!(any(not(feature = "module"), target_os = "windows"));

    if include_dir != "" {
        if need_lua_lib {
            if lib_dir == "" {
                panic!("LUA_LIB is not set");
            }
            if lua_lib == "" {
                panic!("LUA_LIB_NAME is not set");
            }

            let mut link_lib = "";
            if get_env_var("LUA_LINK") == "static" {
                link_lib = "static=";
            };
            println!("cargo:rustc-link-search=native={}", lib_dir);
            println!("cargo:rustc-link-lib={}{}", link_lib, lua_lib);
        }
        return PathBuf::from(include_dir);
    }

    // Find using `pkg-config`

    #[cfg(feature = "lua54")]
    {
        let mut lua = pkg_config::Config::new()
            .range_version((Bound::Included("5.4"), Bound::Excluded("5.5")))
            .cargo_metadata(need_lua_lib)
            .probe("lua");

        if lua.is_err() {
            lua = pkg_config::Config::new()
                .cargo_metadata(need_lua_lib)
                .probe("lua5.4");
        }

        lua.unwrap().include_paths[0].clone()
    }

    #[cfg(feature = "lua53")]
    {
        let mut lua = pkg_config::Config::new()
            .range_version((Bound::Included("5.3"), Bound::Excluded("5.4")))
            .cargo_metadata(need_lua_lib)
            .probe("lua");

        if lua.is_err() {
            lua = pkg_config::Config::new()
                .cargo_metadata(need_lua_lib)
                .probe("lua5.3");
        }

        lua.unwrap().include_paths[0].clone()
    }

    #[cfg(feature = "lua52")]
    {
        let mut lua = pkg_config::Config::new()
            .range_version((Bound::Included("5.2"), Bound::Excluded("5.3")))
            .cargo_metadata(need_lua_lib)
            .probe("lua");

        if lua.is_err() {
            lua = pkg_config::Config::new()
                .cargo_metadata(need_lua_lib)
                .probe("lua5.2");
        }

        lua.unwrap().include_paths[0].clone()
    }

    #[cfg(feature = "lua51")]
    {
        let mut lua = pkg_config::Config::new()
            .range_version((Bound::Included("5.1"), Bound::Excluded("5.2")))
            .cargo_metadata(need_lua_lib)
            .probe("lua");

        if lua.is_err() {
            lua = pkg_config::Config::new()
                .cargo_metadata(need_lua_lib)
                .probe("lua5.1");
        }

        lua.unwrap().include_paths[0].clone()
    }

    #[cfg(feature = "luajit")]
    {
        let lua = pkg_config::Config::new()
            .range_version((Bound::Included("2.0.5"), Bound::Unbounded))
            .cargo_metadata(need_lua_lib)
            .probe("luajit");

        lua.unwrap().include_paths[0].clone()
    }
}