# Define the list of system with their properties.
#
# See https://clang.llvm.org/docs/CrossCompilation.html and
# http://llvm.org/docs/doxygen/html/Triple_8cpp_source.html especially
# Triple::normalize. Parsing should essentially act as a more conservative
# version of that last function.
#
# Most of the types below come in "open" and "closed" pairs. The open ones
# specify what information we need to know about systems in general, and the
# closed ones are sub-types representing the whitelist of systems we support in
# practice.
#
# Code in the remainder of nixpkgs shouldn't rely on the closed ones in
# e.g. exhaustive cases. Its more a sanity check to make sure nobody defines
# systems that overlap with existing ones and won't notice something amiss.
#
{ lib }:
with lib.lists;
with lib.types;
with lib.attrsets;
with lib.strings;
with (import ./inspect.nix { inherit lib; }).predicates;

let
  inherit (lib.options) mergeOneOption;

  setTypes = type:
    mapAttrs (name: value:
      assert type.check value;
      setType type.name ({ inherit name; } // value));

in

rec {

  ################################################################################

  types.openSignificantByte = mkOptionType {
    name = "significant-byte";
    description = "Endianness";
    merge = mergeOneOption;
  };

  types.significantByte = enum (attrValues significantBytes);

  significantBytes = setTypes types.openSignificantByte {
    bigEndian = {};
    littleEndian = {};
  };

  ################################################################################

  # Reasonable power of 2
  types.bitWidth = enum [ 8 16 32 64 128 ];

  ################################################################################

  types.openCpuType = mkOptionType {
    name = "cpu-type";
    description = "instruction set architecture name and information";
    merge = mergeOneOption;
    check = x: types.bitWidth.check x.bits
      && (if 8 < x.bits
          then types.significantByte.check x.significantByte
          else !(x ? significantByte));
  };

  types.cpuType = enum (attrValues cpuTypes);

  cpuTypes = with significantBytes; setTypes types.openCpuType {
    arm      = { bits = 32; significantByte = littleEndian; family = "arm"; };
    armv5tel = { bits = 32; significantByte = littleEndian; family = "arm"; version = "5"; };
    armv6m   = { bits = 32; significantByte = littleEndian; family = "arm"; version = "6"; };
    armv6l   = { bits = 32; significantByte = littleEndian; family = "arm"; version = "6"; };
    armv7a   = { bits = 32; significantByte = littleEndian; family = "arm"; version = "7"; };
    armv7r   = { bits = 32; significantByte = littleEndian; family = "arm"; version = "7"; };
    armv7m   = { bits = 32; significantByte = littleEndian; family = "arm"; version = "7"; };
    armv7l   = { bits = 32; significantByte = littleEndian; family = "arm"; version = "7"; };
    armv8a   = { bits = 32; significantByte = littleEndian; family = "arm"; version = "8"; };
    armv8r   = { bits = 32; significantByte = littleEndian; family = "arm"; version = "8"; };
    armv8m   = { bits = 32; significantByte = littleEndian; family = "arm"; version = "8"; };
    aarch64  = { bits = 64; significantByte = littleEndian; family = "arm"; version = "8"; };
    aarch64_be = { bits = 64; significantByte = bigEndian; family = "arm"; version = "8"; };

    i686     = { bits = 32; significantByte = littleEndian; family = "x86"; };
    x86_64   = { bits = 64; significantByte = littleEndian; family = "x86"; };

    mips     = { bits = 32; significantByte = bigEndian;    family = "mips"; };
    mipsel   = { bits = 32; significantByte = littleEndian; family = "mips"; };
    mips64   = { bits = 64; significantByte = bigEndian;    family = "mips"; };
    mips64el = { bits = 64; significantByte = littleEndian; family = "mips"; };

    powerpc  = { bits = 32; significantByte = bigEndian;    family = "power"; };
    powerpc64 = { bits = 64; significantByte = bigEndian; family = "power"; };
    powerpc64le = { bits = 64; significantByte = littleEndian; family = "power"; };
    powerpcle = { bits = 32; significantByte = littleEndian; family = "power"; };

    riscv32  = { bits = 32; significantByte = littleEndian; family = "riscv"; };
    riscv64  = { bits = 64; significantByte = littleEndian; family = "riscv"; };

    sparc    = { bits = 32; significantByte = bigEndian;    family = "sparc"; };
    sparc64  = { bits = 64; significantByte = bigEndian;    family = "sparc"; };

    wasm32   = { bits = 32; significantByte = littleEndian; family = "wasm"; };
    wasm64   = { bits = 64; significantByte = littleEndian; family = "wasm"; };
    
    alpha    = { bits = 64; significantBye = littleEndian; family = "alpha"; };

    avr      = { bits = 8; family = "avr"; };
  };

  ################################################################################

  types.openVendor = mkOptionType {
    name = "vendor";
    description = "vendor for the platform";
    merge = mergeOneOption;
  };

  types.vendor = enum (attrValues vendors);

  vendors = setTypes types.openVendor {
    apple = {};
    pc = {};

    none = {};
    unknown = {};
  };

  ################################################################################

  types.openExecFormat = mkOptionType {
    name = "exec-format";
    description = "executable container used by the kernel";
    merge = mergeOneOption;
  };

  types.execFormat = enum (attrValues execFormats);

  execFormats = setTypes types.openExecFormat {
    aout = {}; # a.out
    elf = {};
    macho = {};
    pe = {};

    unknown = {};
  };

  ################################################################################

  types.openKernelFamily = mkOptionType {
    name = "exec-format";
    description = "executable container used by the kernel";
    merge = mergeOneOption;
  };

  types.kernelFamily = enum (attrValues kernelFamilies);

  kernelFamilies = setTypes types.openKernelFamily {
    bsd = {};
    darwin = {};
  };

  ################################################################################

  types.openKernel = mkOptionType {
    name = "kernel";
    description = "kernel name and information";
    merge = mergeOneOption;
    check = x: types.execFormat.check x.execFormat
        && all types.kernelFamily.check (attrValues x.families);
  };

  types.kernel = enum (attrValues kernels);

  kernels = with execFormats; with kernelFamilies; setTypes types.openKernel {
    # TODO(@Ericson2314): Don't want to mass-rebuild yet to keeping 'darwin' as
    # the nnormalized name for macOS.
    macos   = { execFormat = macho;   families = { inherit darwin; }; name = "darwin"; };
    ios     = { execFormat = macho;   families = { inherit darwin; }; };
    freebsd = { execFormat = elf;     families = { inherit bsd; }; };
    linux   = { execFormat = elf;     families = { }; };
    netbsd  = { execFormat = elf;     families = { inherit bsd; }; };
    none    = { execFormat = unknown; families = { }; };
    openbsd = { execFormat = elf;     families = { inherit bsd; }; };
    solaris = { execFormat = elf;     families = { }; };
    windows = { execFormat = pe;      families = { }; };
  } // { # aliases
    # 'darwin' is the kernel for all of them. We choose macOS by default.
    darwin = kernels.macos;
    watchos = kernels.ios;
    tvos = kernels.ios;
    win32 = kernels.windows;
  };

  ################################################################################

  types.openAbi = mkOptionType {
    name = "abi";
    description = "binary interface for compiled code and syscalls";
    merge = mergeOneOption;
  };

  types.abi = enum (attrValues abis);

  abis = setTypes types.openAbi {
    cygnus       = {};
    msvc         = {};
    eabi         = {};
    elf         = {};

    androideabi  = {};
    android      = {
      assertions = [
        { assertion = platform: !platform.isAarch32;
          message = ''
            The "android" ABI is not for 32-bit ARM. Use "androideabi" instead.
          '';
        }
      ];
    };

    gnueabi      = { float = "soft"; };
    gnueabihf    = { float = "hard"; };
    gnu          = {
      assertions = [
        { assertion = platform: !platform.isAarch32;
          message = ''
            The "gnu" ABI is ambiguous on 32-bit ARM. Use "gnueabi" or "gnueabihf" instead.
          '';
        }
      ];
    };

    musleabi     = { float = "soft"; };
    musleabihf   = { float = "hard"; };
    musl         = {};

    uclibceabihf = { float = "soft"; };
    uclibceabi   = { float = "hard"; };
    uclibc       = {};

    unknown = {};
  };

  ################################################################################

  types.parsedPlatform = mkOptionType {
    name = "system";
    description = "fully parsed representation of llvm- or nix-style platform tuple";
    merge = mergeOneOption;
    check = { cpu, vendor, kernel, abi }:
           types.cpuType.check cpu
        && types.vendor.check vendor
        && types.kernel.check kernel
        && types.abi.check abi;
  };

  isSystem = isType "system";

  mkSystem = components:
    assert types.parsedPlatform.check components;
    setType "system" components;

  mkSkeletonFromList = l: {
    "1" = if elemAt l 0 == "avr"
      then { cpu = elemAt l 0; kernel = "none"; abi = "unknown"; }
      else throw "Target specification with 1 components is ambiguous";
    "2" = # We only do 2-part hacks for things Nix already supports
      if elemAt l 1 == "cygwin"
        then { cpu = elemAt l 0;                      kernel = "windows";  abi = "cygnus";   }
      else if (elemAt l 1 == "eabi")
        then { cpu = elemAt l 0; vendor = "none"; kernel = "none"; abi = elemAt l 1; }
      else if (elemAt l 1 == "elf")
        then { cpu = elemAt l 0; vendor = "none"; kernel = "none"; abi = elemAt l 1; }
      else   { cpu = elemAt l 0;                      kernel = elemAt l 1;                   };
    "3" = # Awkwards hacks, beware!
      if elemAt l 1 == "apple"
        then { cpu = elemAt l 0; vendor = "apple";    kernel = elemAt l 2;                   }
      else if (elemAt l 1 == "linux") || (elemAt l 2 == "gnu")
        then { cpu = elemAt l 0;                      kernel = elemAt l 1; abi = elemAt l 2; }
      else if (elemAt l 2 == "mingw32") # autotools breaks on -gnu for window
        then { cpu = elemAt l 0; vendor = elemAt l 1; kernel = "windows";  abi = "gnu"; }
      else if hasPrefix "netbsd" (elemAt l 2)
        then { cpu = elemAt l 0; vendor = elemAt l 1;    kernel = elemAt l 2;                }
      else if (elemAt l 2 == "eabi")
        then { cpu = elemAt l 0; vendor = elemAt l 1; kernel = "none"; abi = elemAt l 2; }
      else if (elemAt l 2 == "elf")
        then { cpu = elemAt l 0; vendor = elemAt l 1; kernel = "none"; abi = elemAt l 2; }
      else throw "Target specification with 3 components is ambiguous";
    "4" =    { cpu = elemAt l 0; vendor = elemAt l 1; kernel = elemAt l 2; abi = elemAt l 3; };
  }.${toString (length l)}
    or (throw "system string has invalid number of hyphen-separated components");

  # This should revert the job done by config.guess from the gcc compiler.
  mkSystemFromSkeleton = { cpu
                         , # Optional, but fallback too complex for here.
                           # Inferred below instead.
                           vendor ? assert false; null
                         , kernel
                         , # Also inferred below
                           abi    ? assert false; null
                         } @ args: let
    getCpu    = name: cpuTypes.${name} or (throw "Unknown CPU type: ${name}");
    getVendor = name:  vendors.${name} or (throw "Unknown vendor: ${name}");
    getKernel = name:  kernels.${name} or (throw "Unknown kernel: ${name}");
    getAbi    = name:     abis.${name} or (throw "Unknown ABI: ${name}");

    parsed = rec {
      cpu = getCpu args.cpu;
      vendor =
        /**/ if args ? vendor    then getVendor args.vendor
        else if isDarwin  parsed then vendors.apple
        else if isWindows parsed then vendors.pc
        else                     vendors.unknown;
      kernel = if hasPrefix "darwin" args.kernel      then getKernel "darwin"
               else if hasPrefix "netbsd" args.kernel then getKernel "netbsd"
               else                                   getKernel args.kernel;
      abi =
        /**/ if args ? abi       then getAbi args.abi
        else if isLinux   parsed then
          if isAarch32 parsed then
            if lib.versionAtLeast (parsed.cpu.version or "0") "6"
            then abis.gnueabihf
            else abis.gnueabi
          else abis.gnu
        else if isWindows parsed then abis.gnu
        else                     abis.unknown;
    };

  in mkSystem parsed;

  mkSystemFromString = s: mkSystemFromSkeleton (mkSkeletonFromList (lib.splitString "-" s));

  doubleFromSystem = { cpu, vendor, kernel, abi, ... }:
    /**/ if abi == abis.cygnus       then "${cpu.name}-cygwin"
    else if kernel.families ? darwin then "${cpu.name}-darwin"
    else "${cpu.name}-${kernel.name}";

  tripleFromSystem = { cpu, vendor, kernel, abi, ... } @ sys: assert isSystem sys; let
    optAbi = lib.optionalString (abi != abis.unknown) "-${abi.name}";
  in "${cpu.name}-${vendor.name}-${kernel.name}${optAbi}";

  ################################################################################

}