// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

/*!

Dynamic library facilities.

A simple wrapper over the platforms dynamic library facilities

*/
use cast;
use path;
use libc;
use ops::*;
use option::*;
use result::*;

pub struct DynamicLibrary { priv handle: *libc::c_void }

impl Drop for DynamicLibrary {
    fn finalize(&self) {
        match do dl::check_for_errors_in {
            unsafe {
                dl::close(self.handle)
            }
        } {
            Ok(()) => { },
            Err(str) => fail!(str)
        }
    }
}

impl DynamicLibrary {
    /// Lazily open a dynamic library. When passed None it gives a
    /// handle to the calling process
    pub fn open(filename: Option<&path::Path>) -> Result<DynamicLibrary, ~str> {
        do dl::check_for_errors_in {
            unsafe {
                DynamicLibrary { handle:
                    match filename {
                        Some(name) => dl::open_external(name),
                        None => dl::open_internal()
                    }
                }
            }
        }
    }

    /// Access the value at the symbol of the dynamic library
    pub unsafe fn symbol<T>(&self, symbol: &str) -> Result<T, ~str> {
        // This function should have a lifetime constraint of 'self on
        // T but that feature is still unimplemented

        do dl::check_for_errors_in {
            let symbol_value = do symbol.as_c_str |raw_string| {
                dl::symbol(self.handle, raw_string)
            };

            cast::transmute(symbol_value)
        }
    }
}

#[test]
#[ignore(cfg(windows))]
priv fn test_loading_cosine () {
    // The math library does not need to be loaded since it is already
    // statically linked in
    let libm = match DynamicLibrary::open(None) {
        Err (error) => fail!("Could not load self as module: %s", error),
        Ok (libm) => libm
    };

    // Unfortunately due to issue #6194 it is not possible to call
    // this as a C function
    let cosine: extern fn(libc::c_double) -> libc::c_double = unsafe {
        match libm.symbol("cos") {
            Err (error) => fail!("Could not load function cos: %s", error),
            Ok (cosine) => cosine
        }
    };

    let argument = 0.0;
    let expected_result = 1.0;
    let result = cosine(argument);
    if result != expected_result {
        fail!("cos(%?) != %? but equaled %? instead", argument,
              expected_result, result)
    }
}

#[cfg(target_os = "linux")]
#[cfg(target_os = "android")]
#[cfg(target_os = "macos")]
#[cfg(target_os = "freebsd")]
mod dl {
    use libc;
    use path;
    use ptr;
    use str;
    use task;
    use result::*;

    pub unsafe fn open_external(filename: &path::Path) -> *libc::c_void {
        do filename.to_str().as_c_str |raw_name| {
            dlopen(raw_name, Lazy as libc::c_int)
        }
    }

    pub unsafe fn open_internal() -> *libc::c_void {
        dlopen(ptr::null(), Lazy as libc::c_int)
    }

    pub fn check_for_errors_in<T>(f: &fn()->T) -> Result<T, ~str> {
        unsafe {
            do task::atomically {
                let _old_error = dlerror();

                let result = f();

                let last_error = dlerror();
                if ptr::null() == last_error {
                    Ok(result)
                } else {
                    Err(str::raw::from_c_str(last_error))
                }
            }
        }
    }

    pub unsafe fn symbol(handle: *libc::c_void, symbol: *libc::c_char) -> *libc::c_void {
        dlsym(handle, symbol)
    }
    pub unsafe fn close(handle: *libc::c_void) {
        dlclose(handle); ()
    }

    pub enum RTLD {
        Lazy = 1,
        Now = 2,
        Global = 256,
        Local = 0,
    }

    #[link_name = "dl"]
    extern {
        fn dlopen(filename: *libc::c_char, flag: libc::c_int) -> *libc::c_void;
        fn dlerror() -> *libc::c_char;
        fn dlsym(handle: *libc::c_void, symbol: *libc::c_char) -> *libc::c_void;
        fn dlclose(handle: *libc::c_void) -> libc::c_int;
    }
}

#[cfg(target_os = "win32")]
mod dl {
    use os;
    use libc;
    use path;
    use ptr;
    use str;
    use task;
    use result::*;

    pub unsafe fn open_external(filename: &path::Path) -> *libc::c_void {
        do os::win32::as_utf16_p(filename.to_str()) |raw_name| {
            LoadLibraryW(raw_name)
        }
    }

    pub unsafe fn open_internal() -> *libc::c_void {
        let mut handle = ptr::null();
        GetModuleHandleExW(0 as libc::DWORD, ptr::null(), &handle as **libc::c_void);
        handle
    }

    pub fn check_for_errors_in<T>(f: &fn()->T) -> Result<T, ~str> {
        unsafe {
            do task::atomically {
                SetLastError(0);

                let result = f();

                let error = os::errno();
                if 0 == error {
                    Ok(result)
                } else {
                    Err(fmt!("Error code %?", error))
                }
            }
        }
    }
    pub unsafe fn symbol(handle: *libc::c_void, symbol: *libc::c_char) -> *libc::c_void {
        GetProcAddress(handle, symbol)
    }
    pub unsafe fn close(handle: *libc::c_void) {
        FreeLibrary(handle); ()
    }

    #[link_name = "kernel32"]
    extern "stdcall" {
        fn SetLastError(error: u32);
        fn LoadLibraryW(name: *u16) -> *libc::c_void;
        fn GetModuleHandleExW(dwFlags: libc::DWORD, name: *u16,
                              handle: **libc::c_void) -> *libc::c_void;
        fn GetProcAddress(handle: *libc::c_void, name: *libc::c_char) -> *libc::c_void;
        fn FreeLibrary(handle: *libc::c_void);
    }
}