// file      : butl/triplet -*- C++ -*-
// copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
// license   : MIT; see accompanying LICENSE file

#ifndef BUTL_TRIPLET
#define BUTL_TRIPLET

#include <string>

#include <butl/export>

namespace butl
{
  // This is the ubiquitous 'target triplet' that loosely has the CPU-VENDOR-OS
  // form which, these days, quite often takes the CPU-VENDOR-OS-ABI form. Plus
  // some fields can sometimes be omitted. This looseness makes it hard to base
  // any kind of decisions on the triplet without canonicalizing it and then
  // splitting it into components. the way we are going to split it is like
  // this:
  //
  // CPU
  //
  // This one is reasonably straightforward. Note that we always expect at
  // least two components with the first being the CPU. In other words, we
  // don't try to guess what just 'mingw32' might mean like config.sub does.
  //
  // VENDOR
  //
  // This can be a machine vendor as in i686-apple-darwin8, a toolchain vendor
  // as in i686-lfs-linux-gnu, or something else as in arm-softfloat-linux-gnu.
  // Just as we think vendor is pretty irrelevant and can be ignored, comes
  // MinGW-W64 and calls itself *-w64-mingw32. While it is tempting to
  // attribute w64 to OS-ABI, the MinGW-W64 folks insist it is a (presumably
  // toolchain) vendor.
  //
  // Another example where the vendor seems to be reused for something else
  // entirely is the Intel's MIC architecture: x86_64-k1om-linux.
  //
  // To make things more regular we also convert the information-free vendor
  // names 'pc', 'unknown' and 'none' to the empty name.
  //
  // OS/KERNEL-OS/OS-ABI
  //
  // This is where things get really messy and instead of trying to guess, we
  // call the entire thing SYSTEM. Except, in certain cases, we factor out the
  // trailing version, again, to make SYSTEM easier to compare to. For example,
  // *-darwin14.5.0 becomes 'darwin' and '14.5.0'.
  //
  // Again, to make things more regular, if the first component in SYSTEM is
  // none, then it is removed (so *-none-eabi becomes just 'eabi').
  //
  // Values for two-component systems (e.g., linux-gnu) that don't specify
  // VENDOR explicitly are inherently ambiguous: is 'linux' VENDOR or part of
  // SYSTEM? The only way to handle this is to recognize their specific names
  // as special cases and this is what we do for some of the more common
  // ones. The alternative would be to first run such names through config.sub
  // which adds explicit VENDOR and this could be a reasonable fallback
  // strategy for (presumably less common) cases were we don't split things
  // correctly.
  //
  // Note also that the version splitting is only done for certain commonly-
  // used targets.
  //
  // Some examples of canonicalization and splitting:
  //
  // x86_64-apple-darwin14.5.0        x86_64  apple      darwin         14.5.0
  // x86_64-unknown-freebsd10.2       x86_64             freebsd        10.2
  // i686-elf                         i686               elf
  // arm-eabi                         arm                eabi
  // arm-none-eabi                    arm                eabi
  // arm-none-linux-gnueabi           arm                linux-gnueabi
  // arm-softfloat-linux-gnu          arm     softfloat  linux-gnu
  // i686-pc-mingw32                  i686               mingw32
  // i686-w64-mingw32                 i686    w64        mingw32
  // i686-lfs-linux-gnu               i686    lfs        linux-gnu
  // x86_64-unknown-linux-gnu         x86_64             linux-gnu
  // x86_64-linux-gnux32              x86_64             linux-gnux32
  // x86_64-microsoft-win32-msvc14.0  x86_64  microsoft  win32-msvc     14.0
  //
  // Similar to version splitting, for certain commonly-used targets we also
  // derive the "target class" which can be used as a shorthand, more
  // convenient way to identify a targets. If the target is not recognized,
  // then the special 'other' value is used. Currently the following classes
  // are recognized:
  //
  // linux     *-*-linux-*
  // macosx    *-apple-darwin*
  // bsd       *-*-(freebsd|openbsd|netbsd)*
  // windows   *-*-win32-* | *-*-mingw32
  //
  // References:
  //
  // 1. The libtool repository contains the PLATFORM file that lists many known
  //    triplets.
  //
  // 2. LLVM has the Triple class with similar goals.
  //
  struct LIBBUTL_EXPORT triplet
  {
    std::string cpu;
    std::string vendor;
    std::string system;
    std::string version;
    std::string class_;

    // Parse the triplet optionally returning the canonicalized string. Throw
    // std::invalid_argument if the triplet is not recognizable.
    //
    explicit
    triplet (const std::string&, std::string* canon = nullptr);
    triplet (const std::string& s, std::string& canon): triplet (s, &canon) {}
    triplet () = default;
  };
};

#endif // BUTL_TRIPLET