module spasm.ct;

import std.traits : isPointer, isSomeString, isType;
import std.meta : Filter, AliasSeq;

template getName(alias sym)
{
  enum getName = __traits(identifier, sym);
}

template getStringUDAs(alias symbol) {
  template isStringUDA(alias t) {
    static if (isType!t) {
      enum isStringUDA = isSomeString!(t);
    } else
      enum isStringUDA = isSomeString!(typeof(t));
  }
  alias getStringUDAs = Filter!(isStringUDA,AliasSeq!(__traits(getAttributes, symbol)));
}

template getMember(alias T, string name) {
  import std.meta : AliasSeq;
  alias getMember = AliasSeq!(__traits(getMember, T, name))[0];
}

template from(string moduleName)
{
  mixin("import from = " ~ moduleName ~ ";");
}

// NOTE: below is mainly stuff from phobos modified a tiny bit for betterC

template toLower(string str)
{
  static if (str.length == 0)
    enum toLower = "";
  else static if (str[0] < 0xAA)
  {
    static if (str[0] < 'A')
      enum toLower = c ~ toLower!(str[1 .. $]);
    else static if (str[0] <= 'Z')
      enum toLower = str[0] + 32 ~ toLower!(str[1 .. $]);
    else
      enum toLower = str[0] ~ toLower!(str[1 .. $]);
  }
  else
    enum toLower = str[0] ~ toLower!(str[1 .. $]);
}

template capitalize(string str)
{
  static if (str.length == 0)
    enum capitalize = "";
  else static if (str[0] < 0xAA)
  {
    static if (str[0] < 'a')
      enum capitalize = str;
    else static if (str[0] <= 'z')
      enum capitalize = str[0] - 32 ~ str[1 .. $];
    else
      enum capitalize = str;
  }
  else
    enum capitalize = str;
}

template isSomeFunction(T...) if (T.length == 1)
{
  static if (is(typeof(&T[0]) U : U*) && is(U == function) || is(typeof(&T[0]) U == delegate))
  {
    // T is a (nested) function symbol.
    enum bool isSomeFunction = true;
  }
  else static if (is(T[0] W) || is(typeof(T[0]) W))
  {
    // T is an expression or a type.  Take the type of it and examine.
    static if (is(W F : F*) && is(F == function))
      enum bool isSomeFunction = true; // function pointer
    else
      enum bool isSomeFunction = is(W == function) || is(W == delegate);
  }
  else
    enum bool isSomeFunction = false;
}

template isCallable(T...)if (T.length == 1)
{
  static if (is(typeof( & T[0].opCall) == delegate)) // T is a object which has a member function opCall().
    enum bool isCallable = true;
  else static if (is(typeof( & T[0].opCall) V : V * ) && is(V == function)) // T is a type which has a static member function opCall().
    enum bool isCallable = true;
  else
    enum bool isCallable = isSomeFunction!T;
}

template isDelegate(T...) if (T.length == 1)
{
  static if (is(typeof(&T[0]) U : U*) && is(typeof(&T[0]) U == delegate))
  {
    // T is a (nested) function symbol.
    enum bool isDelegate = true;
  }
  else static if (is(T[0] W) || is(typeof(T[0]) W))
  {
    // T is an expression or a type.  Take the type of it and examine.
    enum bool isDelegate = is(W == delegate);
  }
  else
    enum bool isDelegate = false;
}

template isFunctionPointer(T...) if (T.length == 1)
{
  static if (is(T[0] U) || is(typeof(T[0]) U))
  {
    static if (is(U F : F*) && is(F == function))
      enum bool isFunctionPointer = true;
    else
      enum bool isFunctionPointer = false;
  }
  else
    enum bool isFunctionPointer = false;
}

template FunctionTypeOf(func...)
if (func.length == 1 && isCallable!func)
{
    static if (is(typeof(& func[0]) Fsym : Fsym*) && is(Fsym == function) || is(typeof(& func[0]) Fsym == delegate))
    {
        alias FunctionTypeOf = Fsym; // HIT: (nested) function symbol
    }
    else static if (is(typeof(& func[0].opCall) Fobj == delegate))
    {
        alias FunctionTypeOf = Fobj; // HIT: callable object
    }
    else static if (is(typeof(& func[0].opCall) Ftyp : Ftyp*) && is(Ftyp == function))
    {
        alias FunctionTypeOf = Ftyp; // HIT: callable type
    }
    else static if (is(func[0] T) || is(typeof(func[0]) T))
    {
        static if (is(T == function))
            alias FunctionTypeOf = T;    // HIT: function
        else static if (is(T Fptr : Fptr*) && is(Fptr == function))
            alias FunctionTypeOf = Fptr; // HIT: function pointer
        else static if (is(T Fdlg == delegate))
            alias FunctionTypeOf = Fdlg; // HIT: delegate
        else
            static assert(0);
    }
    else
        static assert(0);
}

template ParameterIdentifierTuple(func...)
if (func.length == 1 && isCallable!func)
{
  import std.meta : AliasSeq;
    static if (is(FunctionTypeOf!func PT == __parameters))
    {
        template Get(size_t i)
        {
            static if (!isFunctionPointer!func && !isDelegate!func
                       // Unnamed parameters yield CT error.
                       && is(typeof(__traits(identifier, PT[i .. i+1]))))
            {
                enum Get = __traits(identifier, PT[i .. i+1]);
            }
            else
            {
                enum Get = "";
            }
        }
    }
    else
    {
        static assert(0, func[0].stringof ~ "is not a function");

        // Define dummy entities to avoid pointless errors
        template Get(size_t i) { enum Get = ""; }
        alias PT = AliasSeq!();
    }

    template Impl(size_t i = 0)
    {
        static if (i == PT.length)
            alias Impl = AliasSeq!();
        else
            alias Impl = AliasSeq!(Get!i, Impl!(i+1));
    }

    alias ParameterIdentifierTuple = Impl!();
}

template getNamedFields(size_t I = 0, Specs...) {
  static if (Specs[0].name.length != 0)
    enum byName = "alias " ~ Specs[0].name ~ " = _" ~ I.stringof ~ ";";
  else
    enum byName = "";
  enum namedField = "alias _" ~ I.stringof ~ " = Identity!(field[" ~ I.stringof ~ "]);" ~ byName;
  static if (Specs.length == 1) {
    enum getNamedFields = namedField;
  } else {
    enum getNamedFields = namedField ~ getNamedFields!(I+1,Specs[1..$]);
  }
}

template Tuple(Specs...)
if (distinctFieldNames!(Specs))
{
  import std.meta : AliasSeq;
    import std.meta : staticMap;

    // Parse (type,name) pairs (FieldSpecs) out of the specified
    // arguments. Some fields would have name, others not.
    template parseSpecs(Specs...)
    {
        static if (Specs.length == 0)
        {
            alias parseSpecs = AliasSeq!();
        }
        else static if (is(Specs[0]))
        {
            static if (is(typeof(Specs[1]) : string))
            {
                alias parseSpecs =
                    AliasSeq!(FieldSpec!(Specs[0 .. 2]),
                              parseSpecs!(Specs[2 .. $]));
            }
            else
            {
                alias parseSpecs =
                    AliasSeq!(FieldSpec!(Specs[0]),
                              parseSpecs!(Specs[1 .. $]));
            }
        }
        else
        {
            static assert(0, "Attempted to instantiate Tuple with an "
                            ~"invalid argument: "~ Specs[0].stringof);
        }
    }

    template FieldSpec(T, string s = "")
    {
        alias Type = T;
        alias name = s;
    }

    alias fieldSpecs = parseSpecs!Specs;

    // Used with staticMap.
    alias extractType(alias spec) = spec.Type;
    alias extractName(alias spec) = spec.name;

    // Returns Specs for a subtuple this[from .. to] preserving field
    // names if any.
    alias sliceSpecs(size_t from, size_t to) =
        staticMap!(expandSpec, fieldSpecs[from .. to]);

    template expandSpec(alias spec)
    {
        static if (spec.name.length == 0)
        {
            alias expandSpec = AliasSeq!(spec.Type);
        }
        else
        {
            alias expandSpec = AliasSeq!(spec.Type, spec.name);
        }
    }

    enum areCompatibleTuples(Tup1, Tup2, string op) = isTuple!Tup2 && is(typeof(
    (ref Tup1 tup1, ref Tup2 tup2)
    {
        static assert(tup1.field.length == tup2.field.length);
        static foreach (i; 0 .. Tup1.Types.length)
        {{
            auto lhs = typeof(tup1.field[i]).init;
            auto rhs = typeof(tup2.field[i]).init;
            static if (op == "=")
                lhs = rhs;
            else
                auto result = mixin("lhs "~op~" rhs");
        }}
    }));

    enum areBuildCompatibleTuples(Tup1, Tup2) = isTuple!Tup2 && is(typeof(
    {
        static assert(Tup1.Types.length == Tup2.Types.length);
        static foreach (i; 0 .. Tup1.Types.length)
            static assert(isBuildable!(Tup1.Types[i], Tup2.Types[i]));
    }));

    /+ Returns `true` iff a `T` can be initialized from a `U`. +/
    enum isBuildable(T, U) =  is(typeof(
    {
        U u = U.init;
        T t = u;
    }));
    /+ Helper for partial instantiation +/
    template isBuildableFrom(U)
    {
        enum isBuildableFrom(T) = isBuildable!(T, U);
    }

    struct Tuple
    {
        /**
         * The types of the `Tuple`'s components.
         */
        alias Types = staticMap!(extractType, fieldSpecs);

        private alias _Fields = Specs;

        /**
         * The names of the `Tuple`'s components. Unnamed fields have empty names.
         */
        alias fieldNames = staticMap!(extractName, fieldSpecs);

        /**
         * Use `t.expand` for a `Tuple` `t` to expand it into its
         * components. The result of `expand` acts as if the `Tuple`'s components
         * were listed as a list of values. (Ordinarily, a `Tuple` acts as a
         * single value.)
         */
        Types expand;
      mixin(getNamedFields!(0, fieldSpecs));

        static if (is(Specs))
        {
            // This is mostly to make t[n] work.
            alias expand this;
        }
        else
        {
            @property
            ref inout(Tuple!Types) _Tuple_super() inout @trusted
            {
                static foreach (i; 0 .. Types.length)   // Rely on the field layout
                {
                    static assert(typeof(return).init.tupleof[i].offsetof ==
                                                       expand[i].offsetof);
                }
                return *cast(typeof(return)*) &(field[0]);
            }
            // This is mostly to make t[n] work.
            alias _Tuple_super this;
        }

        // backwards compatibility
        alias field = expand;

        /**
         * Constructor taking one value for each field.
         *
         * Params:
         *     values = A list of values that are either the same
         *              types as those given by the `Types` field
         *              of this `Tuple`, or can implicitly convert
         *              to those types. They must be in the same
         *              order as they appear in `Types`.
         */
        static if (Types.length > 0)
        {
            this(Types values)
            {
                field[] = values[];
            }
        }

        /**
         * Constructor taking a compatible array.
         *
         * Params:
         *     values = A compatible static array to build the `Tuple` from.
         *              Array slices are not supported.
         */
        this(U, size_t n)(U[n] values)
        if (n == Types.length && allSatisfy!(isBuildableFrom!U, Types))
        {
            static foreach (i; 0 .. Types.length)
            {
                field[i] = values[i];
            }
        }

        /**
         * Constructor taking a compatible `Tuple`. Two `Tuple`s are compatible
         * $(B iff) they are both of the same length, and, for each type `T` on the
         * left-hand side, the corresponding type `U` on the right-hand side can
         * implicitly convert to `T`.
         *
         * Params:
         *     another = A compatible `Tuple` to build from. Its type must be
         *               compatible with the target `Tuple`'s type.
         */
        this(U)(U another)
        if (areBuildCompatibleTuples!(typeof(this), U))
        {
            field[] = another.field[];
        }

        /**
         * Comparison for equality. Two `Tuple`s are considered equal
         * $(B iff) they fulfill the following criteria:
         *
         * $(UL
         *   $(LI Each `Tuple` is the same length.)
         *   $(LI For each type `T` on the left-hand side and each type
         *        `U` on the right-hand side, values of type `T` can be
         *        compared with values of type `U`.)
         *   $(LI For each value `v1` on the left-hand side and each value
         *        `v2` on the right-hand side, the expression `v1 == v2` is
         *        true.))
         *
         * Params:
         *     rhs = The `Tuple` to compare against. It must meeting the criteria
         *           for comparison between `Tuple`s.
         *
         * Returns:
         *     true if both `Tuple`s are equal, otherwise false.
         */
        bool opEquals(R)(R rhs)
        if (areCompatibleTuples!(typeof(this), R, "=="))
        {
            return field[] == rhs.field[];
        }

        /// ditto
        bool opEquals(R)(R rhs) const
        if (areCompatibleTuples!(typeof(this), R, "=="))
        {
            return field[] == rhs.field[];
        }

        /// ditto
        bool opEquals(R...)(auto ref R rhs)
        if (R.length > 1 && areCompatibleTuples!(typeof(this), Tuple!R, "=="))
        {
            static foreach (i; 0 .. Types.length)
                if (field[i] != rhs[i])
                    return false;

            return true;
        }

        /**
         * Comparison for ordering.
         *
         * Params:
         *     rhs = The `Tuple` to compare against. It must meet the criteria
         *           for comparison between `Tuple`s.
         *
         * Returns:
         * For any values `v1` on the right-hand side and `v2` on the
         * left-hand side:
         *
         * $(UL
         *   $(LI A negative integer if the expression `v1 < v2` is true.)
         *   $(LI A positive integer if the expression `v1 > v2` is true.)
         *   $(LI 0 if the expression `v1 == v2` is true.))
         */
        int opCmp(R)(R rhs)
        if (areCompatibleTuples!(typeof(this), R, "<"))
        {
            static foreach (i; 0 .. Types.length)
            {
                if (field[i] != rhs.field[i])
                {
                    return field[i] < rhs.field[i] ? -1 : 1;
                }
            }
            return 0;
        }

        /// ditto
        int opCmp(R)(R rhs) const
        if (areCompatibleTuples!(typeof(this), R, "<"))
        {
            static foreach (i; 0 .. Types.length)
            {
                if (field[i] != rhs.field[i])
                {
                    return field[i] < rhs.field[i] ? -1 : 1;
                }
            }
            return 0;
        }

        /**
         Concatenate Tuples.
         Tuple concatenation is only allowed if all named fields are distinct (no named field of this tuple occurs in `t`
         and no named field of `t` occurs in this tuple).
         Params:
             t = The `Tuple` to concatenate with
         Returns: A concatenation of this tuple and `t`
         */
        auto opBinary(string op, T)(auto ref T t)
        if (op == "~")
        {
            static if (isTuple!T)
            {
                static assert(distinctFieldNames!(_Fields, T._Fields),
                    "Cannot concatenate tuples with duplicate fields: " ~ fieldNames.stringof ~
                    " - " ~ T.fieldNames.stringof);
                return Tuple!(_Fields, T._Fields)(expand, t.expand);
            }
            else
            {
                return Tuple!(_Fields, T)(expand, t);
            }
        }

        /// ditto
        auto opBinaryRight(string op, T)(auto ref T t)
        if (op == "~")
        {
            static if (isTuple!T)
            {
                static assert(distinctFieldNames!(_Fields, T._Fields),
                    "Cannot concatenate tuples with duplicate fields: " ~ T.stringof ~
                    " - " ~ fieldNames.fieldNames.stringof);
                return Tuple!(T._Fields, _Fields)(t.expand, expand);
            }
            else
            {
                return Tuple!(T, _Fields)(t, expand);
            }
        }

        /**
         * Assignment from another `Tuple`.
         *
         * Params:
         *     rhs = The source `Tuple` to assign from. Each element of the
         *           source `Tuple` must be implicitly assignable to each
         *           respective element of the target `Tuple`.
         */
        ref Tuple opAssign(R)(auto ref R rhs)
        if (areCompatibleTuples!(typeof(this), R, "="))
        {
            import std.algorithm.mutation : swap;

            static if (is(R : Tuple!Types) && !__traits(isRef, rhs))
            {
                if (__ctfe)
                {
                    // Cannot use swap at compile time
                    field[] = rhs.field[];
                }
                else
                {
                    // Use swap-and-destroy to optimize rvalue assignment
                    swap!(Tuple!Types)(this, rhs);
                }
            }
            else
            {
                // Do not swap; opAssign should be called on the fields.
                field[] = rhs.field[];
            }
            return this;
        }

        /**
         * Renames the elements of a $(LREF Tuple).
         *
         * `rename` uses the passed `names` and returns a new
         * $(LREF Tuple) using these names, with the content
         * unchanged.
         * If fewer names are passed than there are members
         * of the $(LREF Tuple) then those trailing members are unchanged.
         * An empty string will remove the name for that member.
         * It is an compile-time error to pass more names than
         * there are members of the $(LREF Tuple).
         */
        ref rename(names...)() return
        if (names.length == 0 || allSatisfy!(isSomeString, typeof(names)))
        {
            import std.algorithm.comparison : equal;
            // to circumvent bug 16418
            static if (names.length == 0 || equal([names], [fieldNames]))
                return this;
            else
            {
                enum nT = Types.length;
                enum nN = names.length;
                static assert(nN <= nT, "Cannot have more names than tuple members");
                alias allNames = AliasSeq!(names, fieldNames[nN .. $]);

                template GetItem(size_t idx)
                {
                    import std.array : empty;
                    static if (idx < nT)
                        alias GetItem = Alias!(Types[idx]);
                    else static if (allNames[idx - nT].empty)
                        alias GetItem = AliasSeq!();
                    else
                        alias GetItem = Alias!(allNames[idx - nT]);
                }

                import std.range : roundRobin, iota;
                alias NewTupleT = Tuple!(staticMap!(GetItem, aliasSeqOf!(
                        roundRobin(iota(nT), iota(nT, 2*nT)))));
                return *(() @trusted => cast(NewTupleT*)&this)();
            }
        }

        /**
         * Overload of $(LREF _rename) that takes an associative array
         * `translate` as a template parameter, where the keys are
         * either the names or indices of the members to be changed
         * and the new names are the corresponding values.
         * Every key in `translate` must be the name of a member of the
         * $(LREF tuple).
         * The same rules for empty strings apply as for the variadic
         * template overload of $(LREF _rename).
        */
        ref rename(alias translate)()
        if (is(typeof(translate) : V[K], V, K) && isSomeString!V &&
                (isSomeString!K || is(K : size_t)))
        {
            import std.range : ElementType;
            static if (isSomeString!(ElementType!(typeof(translate.keys))))
            {
                {
                    import std.conv : to;
                    import std.algorithm.iteration : filter;
                    import std.algorithm.searching : canFind;
                    enum notFound = translate.keys
                        .filter!(k => fieldNames.canFind(k) == -1);
                    static assert(notFound.empty, "Cannot find members "
                        ~ notFound.to!string ~ " in type "
                        ~ typeof(this).stringof);
                }
                return this.rename!(aliasSeqOf!(
                    {
                        import std.array : empty;
                        auto names = [fieldNames];
                        foreach (ref n; names)
                            if (!n.empty)
                                if (auto p = n in translate)
                                    n = *p;
                        return names;
                    }()));
            }
            else
            {
                {
                    import std.algorithm.iteration : filter;
                    import std.conv : to;
                    enum invalid = translate.keys.
                        filter!(k => k < 0 || k >= this.length);
                    static assert(invalid.empty, "Indices " ~ invalid.to!string
                        ~ " are out of bounds for tuple with length "
                        ~ this.length.to!string);
                }
                return this.rename!(aliasSeqOf!(
                    {
                        auto names = [fieldNames];
                        foreach (k, v; translate)
                            names[k] = v;
                        return names;
                    }()));
            }
        }

        /**
         * Takes a slice by-reference of this `Tuple`.
         *
         * Params:
         *     from = A `size_t` designating the starting position of the slice.
         *     to = A `size_t` designating the ending position (exclusive) of the slice.
         *
         * Returns:
         *     A new `Tuple` that is a slice from `[from, to$(RPAREN)` of the original.
         *     It has the same types and values as the range `[from, to$(RPAREN)` in
         *     the original.
         */
        @property
        ref inout(Tuple!(sliceSpecs!(from, to))) slice(size_t from, size_t to)() inout @trusted
        if (from <= to && to <= Types.length)
        {
            static assert(
                (typeof(this).alignof % typeof(return).alignof == 0) &&
                (expand[from].offsetof % typeof(return).alignof == 0),
                "Slicing by reference is impossible because of an alignment mistmatch. (See Phobos issue #15645.)");

            return *cast(typeof(return)*) &(field[from]);
        }

        /**
            Creates a hash of this `Tuple`.
            Returns:
                A `size_t` representing the hash of this `Tuple`.
         */
        // size_t toHash() const nothrow @safe
        // {
        //     size_t h = 0;
        //     static foreach (i, T; Types)
        //     {{
        //         const k = typeid(T).getHash((() @trusted => cast(const void*) &field[i])());
        //         static if (i == 0)
        //             h = k;
        //         else
        //             // As in boost::hash_combine
        //             // https://www.boost.org/doc/libs/1_55_0/doc/html/hash/reference.html#boost.hash_combine
        //             h ^= k + 0x9e3779b9 + (h << 6) + (h >>> 2);
        //     }}
        //     return h;
        // }

        /**
         * Converts to string.
         *
         * Returns:
         *     The string representation of this `Tuple`.
         */
        string toString()() const
        {
            import std.array : appender;
            auto app = appender!string();
            this.toString((const(char)[] chunk) => app ~= chunk);
            return app.data;
        }

        import std.format : FormatSpec;

        /**
         * Formats `Tuple` with either `%s`, `%(inner%)` or `%(inner%|sep%)`.
         *
         * $(TABLE2 Formats supported by Tuple,
         * $(THEAD Format, Description)
         * $(TROW $(P `%s`), $(P Format like `Tuple!(types)(elements formatted with %s each)`.))
         * $(TROW $(P `%(inner%)`), $(P The format `inner` is applied the expanded `Tuple`$(COMMA) so
         *      it may contain as many formats as the `Tuple` has fields.))
         * $(TROW $(P `%(inner%|sep%)`), $(P The format `inner` is one format$(COMMA) that is applied
         *      on all fields of the `Tuple`. The inner format must be compatible to all
         *      of them.)))
         *
         * Params:
         *     sink = A `char` accepting delegate
         *     fmt = A $(REF FormatSpec, std,format)
         */
        void toString(DG)(scope DG sink) const
        {
            auto f = FormatSpec!char();
            toString(sink, f);
        }

        /// ditto
        void toString(DG, Char)(scope DG sink, const ref FormatSpec!Char fmt) const
        {
            import std.format : formatElement, formattedWrite, FormatException;
            if (fmt.nested)
            {
                if (fmt.sep)
                {
                    foreach (i, Type; Types)
                    {
                        static if (i > 0)
                        {
                            sink(fmt.sep);
                        }
                        // TODO: Change this once formattedWrite() works for shared objects.
                        static if (is(Type == class) && is(Type == shared))
                        {
                            sink(Type.stringof);
                        }
                        else
                        {
                            formattedWrite(sink, fmt.nested, this.field[i]);
                        }
                    }
                }
                else
                {
                    formattedWrite(sink, fmt.nested, staticMap!(sharedToString, this.expand));
                }
            }
            else if (fmt.spec == 's')
            {
                enum header = Unqual!(typeof(this)).stringof ~ "(",
                     footer = ")",
                     separator = ", ";
                sink(header);
                foreach (i, Type; Types)
                {
                    static if (i > 0)
                    {
                        sink(separator);
                    }
                    // TODO: Change this once formatElement() works for shared objects.
                    static if (is(Type == class) && is(Type == shared))
                    {
                        sink(Type.stringof);
                    }
                    else
                    {
                        FormatSpec!Char f;
                        formatElement(sink, field[i], f);
                    }
                }
                sink(footer);
            }
            else
            {
                throw new FormatException(
                    "Expected '%s' or '%(...%)' or '%(...%|...%)' format specifier for type '" ~
                        Unqual!(typeof(this)).stringof ~ "', not '%" ~ fmt.spec ~ "'.");
            }
        }
    }
}

enum bool distinctFieldNames(names...) = __traits(compiles, {
    static foreach (__name; names)
      static if (is(typeof(__name) : string))
        mixin("enum int " ~ __name ~ " = 0;");
  });

// TODO: can we import this directly
alias Identity(alias A) = A;

enum isTuple(T) = __traits(compiles,
                           {
                             void f(Specs...)(Tuple!Specs tup) {}
                             f(T.init);
                           } );

template tuple(Names...)
{
  import std.meta : AliasSeq;

  /**
    Params:
        args = Values to initialize the `Tuple` with. The `Tuple`'s type will
               be inferred from the types of the values given.
    Returns:
        A new `Tuple` with its type inferred from the arguments given.
     */
    auto tuple(Args...)(Args args)
    {
        static if (Names.length == 0)
        {
            // No specified names, just infer types from Args...
            return Tuple!Args(args);
        }
        else static if (!is(typeof(Names[0]) : string))
        {
            // Names[0] isn't a string, must be explicit types.
            return Tuple!Names(args);
        }
        else
        {
            // Names[0] is a string, so must be specifying names.
            static assert(Names.length == Args.length,
                "Insufficient number of names given.");

            // Interleave(a, b).and(c, d) == (a, c, b, d)
            // This is to get the interleaving of types and names for Tuple
            // e.g. Tuple!(int, "x", string, "y")
            template Interleave(A...)
            {
                template and(B...) if (B.length == 1)
                {
                    alias and = AliasSeq!(A[0], B[0]);
                }

                template and(B...) if (B.length != 1)
                {
                    alias and = AliasSeq!(A[0], B[0],
                        Interleave!(A[1..$]).and!(B[1..$]));
                }
            }
            return Tuple!(Interleave!(Args).and!(Names))(args);
        }
    }
}

template replace(string str, dchar from, dchar to) {
  static if (str.length == 0) {
    enum replace = "";
  } else static if (str[0] == from) {
    enum replace = to ~ replace!(str[1..$],from,to);
  } else
    enum replace = str[0] ~ replace!(str[1..$],from,to);
}

template Joiner(Ts...) {
  static if (Ts.length > 0) {
    enum Joiner = Ts[0] ~ Joiner!(Ts[1..$]);
  } else
    enum Joiner = "";
}