#include "sass.hpp"

#include "functions.hpp"

#include "ast.hpp"

#include "context.hpp"

#include "backtrace.hpp"

#include "parser.hpp"

#include "constants.hpp"

#include "inspect.hpp"

#include "extend.hpp"

#include "eval.hpp"

#include "util.hpp"

#include "expand.hpp"

#include "utf8_string.hpp"

#include "sass/base.h"

#include "utf8.h"

#include <cstdint>

#include <cstdlib>

#include <cmath>

#include <cctype>

#include <sstream>

#include <string>

#include <iomanip>

#include <iostream>

#include <random>

#include <set>

#ifdef __MINGW32__

#include "windows.h"

#include "wincrypt.h"

#endif

#define ARG(argname, argtype) get_arg<argtype>(argname, env, sig, pstate, backtrace)

#define ARGR(argname, argtype, lo, hi) get_arg_r(argname, env, sig, pstate, lo, hi, backtrace)

#define ARGM(argname, argtype, ctx) get_arg_m(argname, env, sig, pstate, backtrace, ctx)

namespace Sass {

  using std::stringstream;

  using std::endl;

  Definition_Ptr make_native_function(Signature sig, Native_Function func, Context& ctx)

  {

    Parser sig_parser = Parser::from_c_str(sig, ctx, ParserState("[built-in function]"));

    sig_parser.lex<Prelexer::identifier>();

    std::string name(Util::normalize_underscores(sig_parser.lexed));

    Parameters_Obj params = sig_parser.parse_parameters();

    return SASS_MEMORY_NEW(Definition,

                           ParserState("[built-in function]"),

                           sig,

                           name,

                           params,

                           func,

                           false);

  }

  Definition_Ptr make_c_function(Sass_Function_Entry c_func, Context& ctx)

  {

    using namespace Prelexer;

    const char* sig = sass_function_get_signature(c_func);

    Parser sig_parser = Parser::from_c_str(sig, ctx, ParserState("[c function]"));

    // allow to overload generic callback plus @warn, @error and @debug with custom functions

    sig_parser.lex < alternatives < identifier, exactly <'*'>,

                                    exactly < Constants::warn_kwd >,

                                    exactly < Constants::error_kwd >,

                                    exactly < Constants::debug_kwd >

                   >              >();

    std::string name(Util::normalize_underscores(sig_parser.lexed));

    Parameters_Obj params = sig_parser.parse_parameters();

    return SASS_MEMORY_NEW(Definition,

                           ParserState("[c function]"),

                           sig,

                           name,

                           params,

                           c_func,

                           false, true);

  }

  std::string function_name(Signature sig)

  {

    std::string str(sig);

    return str.substr(0, str.find('('));

  }

  namespace Functions {

    inline void handle_utf8_error (const ParserState& pstate, Backtrace* backtrace)

    {

      try {

       throw;

      }

      catch (utf8::invalid_code_point) {

        std::string msg("utf8::invalid_code_point");

        error(msg, pstate, backtrace);

      }

      catch (utf8::not_enough_room) {

        std::string msg("utf8::not_enough_room");

        error(msg, pstate, backtrace);

      }

      catch (utf8::invalid_utf8) {

        std::string msg("utf8::invalid_utf8");

        error(msg, pstate, backtrace);

      }

      catch (...) { throw; }

    }

    template <typename T>

    T* get_arg(const std::string& argname, Env& env, Signature sig, ParserState pstate, Backtrace* backtrace)

    {

      // Minimal error handling -- the expectation is that built-ins will be written correctly!

      T* val = Cast<T>(env[argname]);

      if (!val) {

        std::string msg("argument `");

        msg += argname;

        msg += "` of `";

        msg += sig;

        msg += "` must be a ";

        msg += T::type_name();

        error(msg, pstate, backtrace);

      }

      return val;

    }

    Map_Ptr get_arg_m(const std::string& argname, Env& env, Signature sig, ParserState pstate, Backtrace* backtrace, Context& ctx)

    {

      // Minimal error handling -- the expectation is that built-ins will be written correctly!

      Map_Ptr val = Cast<Map>(env[argname]);

      if (val) return val;

      List_Ptr lval = Cast<List>(env[argname]);

      if (lval && lval->length() == 0) return SASS_MEMORY_NEW(Map, pstate, 0);

      // fallback on get_arg for error handling

      val = get_arg<Map>(argname, env, sig, pstate, backtrace);

      return val;

    }

    Number_Ptr get_arg_r(const std::string& argname, Env& env, Signature sig, ParserState pstate, double lo, double hi, Backtrace* backtrace)

    {

      // Minimal error handling -- the expectation is that built-ins will be written correctly!

      Number_Ptr val = get_arg<Number>(argname, env, sig, pstate, backtrace);

      double v = val->value();

      if (!(lo <= v && v <= hi)) {

        std::stringstream msg;

        msg << "argument `" << argname << "` of `" << sig << "` must be between ";

        msg << lo << " and " << hi;

        error(msg.str(), pstate, backtrace);

      }

      return val;

    }

    #define ARGSEL(argname, seltype, contextualize) get_arg_sel<seltype>(argname, env, sig, pstate, backtrace, ctx)

    template <typename T>

    T get_arg_sel(const std::string& argname, Env& env, Signature sig, ParserState pstate, Backtrace* backtrace, Context& ctx);

    template <>

    Selector_List_Obj get_arg_sel(const std::string& argname, Env& env, Signature sig, ParserState pstate, Backtrace* backtrace, Context& ctx) {

      Expression_Obj exp = ARG(argname, Expression);

      if (exp->concrete_type() == Expression::NULL_VAL) {

        std::stringstream msg;

        msg << argname << ": null is not a valid selector: it must be a string,\n";

        msg << "a list of strings, or a list of lists of strings for `" << function_name(sig) << "'";

        error(msg.str(), pstate);

      }

      if (String_Constant_Ptr str = Cast<String_Constant>(exp)) {

        str->quote_mark(0);

      }

      std::string exp_src = exp->to_string(ctx.c_options);

      return Parser::parse_selector(exp_src.c_str(), ctx);

    }

    template <>

    Compound_Selector_Obj get_arg_sel(const std::string& argname, Env& env, Signature sig, ParserState pstate, Backtrace* backtrace, Context& ctx) {

      Expression_Obj exp = ARG(argname, Expression);

      if (exp->concrete_type() == Expression::NULL_VAL) {

        std::stringstream msg;

        msg << argname << ": null is not a string for `" << function_name(sig) << "'";

        error(msg.str(), pstate);

      }

      if (String_Constant_Ptr str = Cast<String_Constant>(exp)) {

        str->quote_mark(0);

      }

      std::string exp_src = exp->to_string(ctx.c_options);

      Selector_List_Obj sel_list = Parser::parse_selector(exp_src.c_str(), ctx);

      if (sel_list->length() == 0) return NULL;

      Complex_Selector_Obj first = sel_list->first();

      if (!first->tail()) return first->head();

      return first->tail()->head();

    }

    #ifdef __MINGW32__

    uint64_t GetSeed()

    {

      HCRYPTPROV hp = 0;

      BYTE rb[8];

      CryptAcquireContext(&hp, 0, 0, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);

      CryptGenRandom(hp, sizeof(rb), rb);

      CryptReleaseContext(hp, 0);

      uint64_t seed;

      memcpy(&seed, &rb[0], sizeof(seed));

      return seed;

    }

    #else

    uint64_t GetSeed()

    {

      std::random_device rd;

      return rd();

    }

    #endif

    // note: the performance of many  implementations of

    // random_device degrades sharply once the entropy pool

    // is exhausted. For practical use, random_device is

    // generally only used to seed a PRNG such as mt19937.

    static std::mt19937 rand(static_cast<unsigned int>(GetSeed()));

    // features

    static std::set<std::string> features {

      "global-variable-shadowing",

      "extend-selector-pseudoclass",

      "at-error",

      "units-level-3"

    };

    ////////////////

    // RGB FUNCTIONS

    ////////////////

    inline double color_num(Number_Ptr n) {

      if (n->unit() == "%") {

        return std::min(std::max(n->value() * 255 / 100.0, 0.0), 255.0);

      } else {

        return std::min(std::max(n->value(), 0.0), 255.0);

      }

    }

    inline double alpha_num(Number_Ptr n) {

      if (n->unit() == "%") {

        return std::min(std::max(n->value(), 0.0), 100.0);

      } else {

        return std::min(std::max(n->value(), 0.0), 1.0);

      }

    }

    Signature rgb_sig = "rgb($red, $green, $blue)";

    BUILT_IN(rgb)

    {

      return SASS_MEMORY_NEW(Color,

                             pstate,

                             color_num(ARG("$red",   Number)),

                             color_num(ARG("$green", Number)),

                             color_num(ARG("$blue",  Number)));

    }

    Signature rgba_4_sig = "rgba($red, $green, $blue, $alpha)";

    BUILT_IN(rgba_4)

    {

      return SASS_MEMORY_NEW(Color,

                             pstate,

                             color_num(ARG("$red",   Number)),

                             color_num(ARG("$green", Number)),

                             color_num(ARG("$blue",  Number)),

                             alpha_num(ARG("$alpha", Number)));

    }

    Signature rgba_2_sig = "rgba($color, $alpha)";

    BUILT_IN(rgba_2)

    {

      Color_Ptr c_arg = ARG("$color", Color);

      Color_Ptr new_c = SASS_MEMORY_COPY(c_arg);

      new_c->a(alpha_num(ARG("$alpha", Number)));

      new_c->disp("");

      return new_c;

    }

    Signature red_sig = "red($color)";

    BUILT_IN(red)

    { return SASS_MEMORY_NEW(Number, pstate, ARG("$color", Color)->r()); }

    Signature green_sig = "green($color)";

    BUILT_IN(green)

    { return SASS_MEMORY_NEW(Number, pstate, ARG("$color", Color)->g()); }

    Signature blue_sig = "blue($color)";

    BUILT_IN(blue)

    { return SASS_MEMORY_NEW(Number, pstate, ARG("$color", Color)->b()); }

    Signature mix_sig = "mix($color-1, $color-2, $weight: 50%)";

    BUILT_IN(mix)

    {

      Color_Obj  color1 = ARG("$color-1", Color);

      Color_Obj  color2 = ARG("$color-2", Color);

      Number_Obj weight = ARGR("$weight", Number, 0, 100);

      double p = weight->value()/100;

      double w = 2*p - 1;

      double a = color1->a() - color2->a();

      double w1 = (((w * a == -1) ? w : (w + a)/(1 + w*a)) + 1)/2.0;

      double w2 = 1 - w1;

      return SASS_MEMORY_NEW(Color,

                             pstate,

                             Sass::round(w1*color1->r() + w2*color2->r(), ctx.c_options.precision),

                             Sass::round(w1*color1->g() + w2*color2->g(), ctx.c_options.precision),

                             Sass::round(w1*color1->b() + w2*color2->b(), ctx.c_options.precision),

                             color1->a()*p + color2->a()*(1-p));

    }

    ////////////////

    // HSL FUNCTIONS

    ////////////////

    // RGB to HSL helper function

    struct HSL { double h; double s; double l; };

    HSL rgb_to_hsl(double r, double g, double b)

    {

      // Algorithm from http://en.wikipedia.org/wiki/wHSL_and_HSV#Conversion_from_RGB_to_HSL_or_HSV

      r /= 255.0; g /= 255.0; b /= 255.0;

      double max = std::max(r, std::max(g, b));

      double min = std::min(r, std::min(g, b));

      double delta = max - min;

      double h = 0;

      double s;

      double l = (max + min) / 2.0;

      if (max == min) {

        h = s = 0; // achromatic

      }

      else {

        if (l < 0.5) s = delta / (max + min);

        else         s = delta / (2.0 - max - min);

        if      (r == max) h = (g - b) / delta + (g < b ? 6 : 0);

        else if (g == max) h = (b - r) / delta + 2;

        else if (b == max) h = (r - g) / delta + 4;

      }

      HSL hsl_struct;

      hsl_struct.h = h / 6 * 360;

      hsl_struct.s = s * 100;

      hsl_struct.l = l * 100;

      return hsl_struct;

    }

    // hue to RGB helper function

    double h_to_rgb(double m1, double m2, double h) {

      while (h < 0) h += 1;

      while (h > 1) h -= 1;

      if (h*6.0 < 1) return m1 + (m2 - m1)*h*6;

      if (h*2.0 < 1) return m2;

      if (h*3.0 < 2) return m1 + (m2 - m1) * (2.0/3.0 - h)*6;

      return m1;

    }

    Color_Ptr hsla_impl(double h, double s, double l, double a, Context& ctx, ParserState pstate)

    {

      h /= 360.0;

      s /= 100.0;

      l /= 100.0;

      if (l < 0) l = 0;

      if (s < 0) s = 0;

      if (l > 1) l = 1;

      if (s > 1) s = 1;

      while (h < 0) h += 1;

      while (h > 1) h -= 1;

      // if saturation is exacly zero, we loose

      // information for hue, since it will evaluate

      // to zero if converted back from rgb. Setting

      // saturation to a very tiny number solves this.

      if (s == 0) s = 1e-10;

      // Algorithm from the CSS3 spec: http://www.w3.org/TR/css3-color/#hsl-color.

      double m2;

      if (l <= 0.5) m2 = l*(s+1.0);

      else m2 = (l+s)-(l*s);

      double m1 = (l*2.0)-m2;

      // round the results -- consider moving this into the Color constructor

      double r = (h_to_rgb(m1, m2, h + 1.0/3.0) * 255.0);

      double g = (h_to_rgb(m1, m2, h) * 255.0);

      double b = (h_to_rgb(m1, m2, h - 1.0/3.0) * 255.0);

      return SASS_MEMORY_NEW(Color, pstate, r, g, b, a);

    }

    Signature hsl_sig = "hsl($hue, $saturation, $lightness)";

    BUILT_IN(hsl)

    {

      return hsla_impl(ARG("$hue", Number)->value(),

                       ARG("$saturation", Number)->value(),

                       ARG("$lightness",  Number)->value(),

                       1.0,

                       ctx,

                       pstate);

    }

    Signature hsla_sig = "hsla($hue, $saturation, $lightness, $alpha)";

    BUILT_IN(hsla)

    {

      return hsla_impl(ARG("$hue", Number)->value(),

                       ARG("$saturation", Number)->value(),

                       ARG("$lightness",  Number)->value(),

                       ARG("$alpha",  Number)->value(),

                       ctx,

                       pstate);

    }

    Signature hue_sig = "hue($color)";

    BUILT_IN(hue)

    {

      Color_Ptr rgb_color = ARG("$color", Color);

      HSL hsl_color = rgb_to_hsl(rgb_color->r(),

                                 rgb_color->g(),

                                 rgb_color->b());

      return SASS_MEMORY_NEW(Number, pstate, hsl_color.h, "deg");

    }

    Signature saturation_sig = "saturation($color)";

    BUILT_IN(saturation)

    {

      Color_Ptr rgb_color = ARG("$color", Color);

      HSL hsl_color = rgb_to_hsl(rgb_color->r(),

                                 rgb_color->g(),

                                 rgb_color->b());

      return SASS_MEMORY_NEW(Number, pstate, hsl_color.s, "%");

    }

    Signature lightness_sig = "lightness($color)";

    BUILT_IN(lightness)

    {

      Color_Ptr rgb_color = ARG("$color", Color);

      HSL hsl_color = rgb_to_hsl(rgb_color->r(),

                                 rgb_color->g(),

                                 rgb_color->b());

      return SASS_MEMORY_NEW(Number, pstate, hsl_color.l, "%");

    }

    Signature adjust_hue_sig = "adjust-hue($color, $degrees)";

    BUILT_IN(adjust_hue)

    {

      Color_Ptr rgb_color = ARG("$color", Color);

      Number_Ptr degrees = ARG("$degrees", Number);

      HSL hsl_color = rgb_to_hsl(rgb_color->r(),

                                 rgb_color->g(),

                                 rgb_color->b());

      return hsla_impl(hsl_color.h + degrees->value(),

                       hsl_color.s,

                       hsl_color.l,

                       rgb_color->a(),

                       ctx,

                       pstate);

    }

    Signature lighten_sig = "lighten($color, $amount)";

    BUILT_IN(lighten)

    {

      Color_Ptr rgb_color = ARG("$color", Color);

      Number_Ptr amount = ARGR("$amount", Number, 0, 100);

      HSL hsl_color = rgb_to_hsl(rgb_color->r(),

                                 rgb_color->g(),

                                 rgb_color->b());

      //Check lightness is not negative before lighten it

      double hslcolorL = hsl_color.l;

      if (hslcolorL < 0) {

        hslcolorL = 0;

      }

      return hsla_impl(hsl_color.h,

                       hsl_color.s,

                       hslcolorL + amount->value(),

                       rgb_color->a(),

                       ctx,

                       pstate);

    }

    Signature darken_sig = "darken($color, $amount)";

    BUILT_IN(darken)

    {

      Color_Ptr rgb_color = ARG("$color", Color);

      Number_Ptr amount = ARGR("$amount", Number, 0, 100);

      HSL hsl_color = rgb_to_hsl(rgb_color->r(),

                                 rgb_color->g(),

                                 rgb_color->b());

      //Check lightness if not over 100, before darken it

      double hslcolorL = hsl_color.l;

      if (hslcolorL > 100) {

        hslcolorL = 100;

      }

      return hsla_impl(hsl_color.h,

                       hsl_color.s,

                       hslcolorL - amount->value(),

                       rgb_color->a(),

                       ctx,

                       pstate);

    }

    Signature saturate_sig = "saturate($color, $amount: false)";

    BUILT_IN(saturate)

    {

      // CSS3 filter function overload: pass literal through directly

      Number_Ptr amount = Cast<Number>(env["$amount"]);

      if (!amount) {

        return SASS_MEMORY_NEW(String_Quoted, pstate, "saturate(" + env["$color"]->to_string(ctx.c_options) + ")");

      }

      ARGR("$amount", Number, 0, 100);

      Color_Ptr rgb_color = ARG("$color", Color);

      HSL hsl_color = rgb_to_hsl(rgb_color->r(),

                                 rgb_color->g(),

                                 rgb_color->b());

      double hslcolorS = hsl_color.s + amount->value();

      // Saturation cannot be below 0 or above 100

      if (hslcolorS < 0) {

        hslcolorS = 0;

      }

      if (hslcolorS > 100) {

        hslcolorS = 100;

      }

      return hsla_impl(hsl_color.h,

                       hslcolorS,

                       hsl_color.l,

                       rgb_color->a(),

                       ctx,

                       pstate);

    }

    Signature desaturate_sig = "desaturate($color, $amount)";

    BUILT_IN(desaturate)

    {

      Color_Ptr rgb_color = ARG("$color", Color);

      Number_Ptr amount = ARGR("$amount", Number, 0, 100);

      HSL hsl_color = rgb_to_hsl(rgb_color->r(),

                                 rgb_color->g(),

                                 rgb_color->b());

      double hslcolorS = hsl_color.s - amount->value();

      // Saturation cannot be below 0 or above 100

      if (hslcolorS <= 0) {

        hslcolorS = 0;

      }

      if (hslcolorS > 100) {

        hslcolorS = 100;

      }

      return hsla_impl(hsl_color.h,

                       hslcolorS,

                       hsl_color.l,

                       rgb_color->a(),

                       ctx,

                       pstate);

    }

    Signature grayscale_sig = "grayscale($color)";

    BUILT_IN(grayscale)

    {

      // CSS3 filter function overload: pass literal through directly

      Number_Ptr amount = Cast<Number>(env["$color"]);

      if (amount) {

        return SASS_MEMORY_NEW(String_Quoted, pstate, "grayscale(" + amount->to_string(ctx.c_options) + ")");

      }

      Color_Ptr rgb_color = ARG("$color", Color);

      HSL hsl_color = rgb_to_hsl(rgb_color->r(),

                                 rgb_color->g(),

                                 rgb_color->b());

      return hsla_impl(hsl_color.h,

                       0.0,

                       hsl_color.l,

                       rgb_color->a(),

                       ctx,

                       pstate);

    }

    Signature complement_sig = "complement($color)";

    BUILT_IN(complement)

    {

      Color_Ptr rgb_color = ARG("$color", Color);

      HSL hsl_color = rgb_to_hsl(rgb_color->r(),

                                 rgb_color->g(),

                                 rgb_color->b());

      return hsla_impl(hsl_color.h - 180.0,

                       hsl_color.s,

                       hsl_color.l,

                       rgb_color->a(),

                       ctx,

                       pstate);

    }

    Signature invert_sig = "invert($color)";

    BUILT_IN(invert)

    {

      // CSS3 filter function overload: pass literal through directly

      Number_Ptr amount = Cast<Number>(env["$color"]);

      if (amount) {

        return SASS_MEMORY_NEW(String_Quoted, pstate, "invert(" + amount->to_string(ctx.c_options) + ")");

      }

      Color_Ptr rgb_color = ARG("$color", Color);

      return SASS_MEMORY_NEW(Color,

                             pstate,

                             255 - rgb_color->r(),

                             255 - rgb_color->g(),

                             255 - rgb_color->b(),

                             rgb_color->a());

    }

    ////////////////////

    // OPACITY FUNCTIONS

    ////////////////////

    Signature alpha_sig = "alpha($color)";

    Signature opacity_sig = "opacity($color)";

    BUILT_IN(alpha)

    {

      String_Constant_Ptr ie_kwd = Cast<String_Constant>(env["$color"]);

      if (ie_kwd) {

        return SASS_MEMORY_NEW(String_Quoted, pstate, "alpha(" + ie_kwd->value() + ")");

      }

      // CSS3 filter function overload: pass literal through directly

      Number_Ptr amount = Cast<Number>(env["$color"]);

      if (amount) {

        return SASS_MEMORY_NEW(String_Quoted, pstate, "opacity(" + amount->to_string(ctx.c_options) + ")");

      }

      return SASS_MEMORY_NEW(Number, pstate, ARG("$color", Color)->a());

    }

    Signature opacify_sig = "opacify($color, $amount)";

    Signature fade_in_sig = "fade-in($color, $amount)";

    BUILT_IN(opacify)

    {

      Color_Ptr color = ARG("$color", Color);

      double amount = ARGR("$amount", Number, 0, 1)->value();

      double alpha = std::min(color->a() + amount, 1.0);

      return SASS_MEMORY_NEW(Color,

                             pstate,

                             color->r(),

                             color->g(),

                             color->b(),

                             alpha);

    }

    Signature transparentize_sig = "transparentize($color, $amount)";

    Signature fade_out_sig = "fade-out($color, $amount)";

    BUILT_IN(transparentize)

    {

      Color_Ptr color = ARG("$color", Color);

      double amount = ARGR("$amount", Number, 0, 1)->value();

      double alpha = std::max(color->a() - amount, 0.0);

      return SASS_MEMORY_NEW(Color,

                             pstate,

                             color->r(),

                             color->g(),

                             color->b(),

                             alpha);

    }

    ////////////////////////

    // OTHER COLOR FUNCTIONS

    ////////////////////////

    Signature adjust_color_sig = "adjust-color($color, $red: false, $green: false, $blue: false, $hue: false, $saturation: false, $lightness: false, $alpha: false)";

    BUILT_IN(adjust_color)

    {

      Color_Ptr color = ARG("$color", Color);

      Number_Ptr r = Cast<Number>(env["$red"]);

      Number_Ptr g = Cast<Number>(env["$green"]);

      Number_Ptr b = Cast<Number>(env["$blue"]);

      Number_Ptr h = Cast<Number>(env["$hue"]);

      Number_Ptr s = Cast<Number>(env["$saturation"]);

      Number_Ptr l = Cast<Number>(env["$lightness"]);

      Number_Ptr a = Cast<Number>(env["$alpha"]);

      bool rgb = r || g || b;

      bool hsl = h || s || l;

      if (rgb && hsl) {

        error("Cannot specify HSL and RGB values for a color at the same time for `adjust-color'", pstate);

      }

      if (rgb) {

        double rr = r ? ARGR("$red",   Number, -255, 255)->value() : 0;

        double gg = g ? ARGR("$green", Number, -255, 255)->value() : 0;

        double bb = b ? ARGR("$blue",  Number, -255, 255)->value() : 0;

        double aa = a ? ARGR("$alpha", Number, -1, 1)->value() : 0;

        return SASS_MEMORY_NEW(Color,

                               pstate,

                               color->r() + rr,

                               color->g() + gg,

                               color->b() + bb,

                               color->a() + aa);

      }

      if (hsl) {

        HSL hsl_struct = rgb_to_hsl(color->r(), color->g(), color->b());

        double ss = s ? ARGR("$saturation", Number, -100, 100)->value() : 0;

        double ll = l ? ARGR("$lightness",  Number, -100, 100)->value() : 0;

        double aa = a ? ARGR("$alpha",      Number, -1, 1)->value() : 0;

        return hsla_impl(hsl_struct.h + (h ? h->value() : 0),

                         hsl_struct.s + ss,

                         hsl_struct.l + ll,

                         color->a() + aa,

                         ctx,

                         pstate);

      }

      if (a) {

        return SASS_MEMORY_NEW(Color,

                               pstate,

                               color->r(),

                               color->g(),

                               color->b(),

                               color->a() + (a ? a->value() : 0));

      }

      error("not enough arguments for `adjust-color'", pstate);

      // unreachable

      return color;

    }

    Signature scale_color_sig = "scale-color($color, $red: false, $green: false, $blue: false, $hue: false, $saturation: false, $lightness: false, $alpha: false)";

    BUILT_IN(scale_color)

    {

      Color_Ptr color = ARG("$color", Color);

      Number_Ptr r = Cast<Number>(env["$red"]);

      Number_Ptr g = Cast<Number>(env["$green"]);

      Number_Ptr b = Cast<Number>(env["$blue"]);

      Number_Ptr h = Cast<Number>(env["$hue"]);

      Number_Ptr s = Cast<Number>(env["$saturation"]);

      Number_Ptr l = Cast<Number>(env["$lightness"]);

      Number_Ptr a = Cast<Number>(env["$alpha"]);

      bool rgb = r || g || b;

      bool hsl = h || s || l;

      if (rgb && hsl) {

        error("Cannot specify HSL and RGB values for a color at the same time for `scale-color'", pstate);

      }

      if (rgb) {

        double rscale = (r ? ARGR("$red",   Number, -100.0, 100.0)->value() : 0.0) / 100.0;

        double gscale = (g ? ARGR("$green", Number, -100.0, 100.0)->value() : 0.0) / 100.0;

        double bscale = (b ? ARGR("$blue",  Number, -100.0, 100.0)->value() : 0.0) / 100.0;

        double ascale = (a ? ARGR("$alpha", Number, -100.0, 100.0)->value() : 0.0) / 100.0;

        return SASS_MEMORY_NEW(Color,

                               pstate,

                               color->r() + rscale * (rscale > 0.0 ? 255 - color->r() : color->r()),

                               color->g() + gscale * (gscale > 0.0 ? 255 - color->g() : color->g()),

                               color->b() + bscale * (bscale > 0.0 ? 255 - color->b() : color->b()),

                               color->a() + ascale * (ascale > 0.0 ? 1.0 - color->a() : color->a()));

      }

      if (hsl) {

        double hscale = (h ? ARGR("$hue",        Number, -100.0, 100.0)->value() : 0.0) / 100.0;

        double sscale = (s ? ARGR("$saturation", Number, -100.0, 100.0)->value() : 0.0) / 100.0;

        double lscale = (l ? ARGR("$lightness",  Number, -100.0, 100.0)->value() : 0.0) / 100.0;

        double ascale = (a ? ARGR("$alpha",      Number, -100.0, 100.0)->value() : 0.0) / 100.0;

        HSL hsl_struct = rgb_to_hsl(color->r(), color->g(), color->b());

        hsl_struct.h += hscale * (hscale > 0.0 ? 360.0 - hsl_struct.h : hsl_struct.h);

        hsl_struct.s += sscale * (sscale > 0.0 ? 100.0 - hsl_struct.s : hsl_struct.s);

        hsl_struct.l += lscale * (lscale > 0.0 ? 100.0 - hsl_struct.l : hsl_struct.l);

        double alpha = color->a() + ascale * (ascale > 0.0 ? 1.0 - color->a() : color->a());

        return hsla_impl(hsl_struct.h, hsl_struct.s, hsl_struct.l, alpha, ctx, pstate);

      }

      if (a) {

        double ascale = (ARGR("$alpha", Number, -100.0, 100.0)->value()) / 100.0;

        return SASS_MEMORY_NEW(Color,

                               pstate,

                               color->r(),

                               color->g(),

                               color->b(),

                               color->a() + ascale * (ascale > 0.0 ? 1.0 - color->a() : color->a()));

      }

      error("not enough arguments for `scale-color'", pstate);

      // unreachable

      return color;

    }

    Signature change_color_sig = "change-color($color, $red: false, $green: false, $blue: false, $hue: false, $saturation: false, $lightness: false, $alpha: false)";

    BUILT_IN(change_color)

    {

      Color_Ptr color = ARG("$color", Color);

      Number_Ptr r = Cast<Number>(env["$red"]);

      Number_Ptr g = Cast<Number>(env["$green"]);

      Number_Ptr b = Cast<Number>(env["$blue"]);

      Number_Ptr h = Cast<Number>(env["$hue"]);

      Number_Ptr s = Cast<Number>(env["$saturation"]);

      Number_Ptr l = Cast<Number>(env["$lightness"]);

      Number_Ptr a = Cast<Number>(env["$alpha"]);

      bool rgb = r || g || b;

      bool hsl = h || s || l;

      if (rgb && hsl) {

        error("Cannot specify HSL and RGB values for a color at the same time for `change-color'", pstate);

      }

      if (rgb) {

        return SASS_MEMORY_NEW(Color,

                               pstate,

                               r ? ARGR("$red",   Number, 0, 255)->value() : color->r(),

                               g ? ARGR("$green", Number, 0, 255)->value() : color->g(),

                               b ? ARGR("$blue",  Number, 0, 255)->value() : color->b(),

                               a ? ARGR("$alpha", Number, 0, 255)->value() : color->a());

      }

      if (hsl) {

        HSL hsl_struct = rgb_to_hsl(color->r(), color->g(), color->b());

        if (h) hsl_struct.h = std::fmod(h->value(), 360.0);

        if (s) hsl_struct.s = ARGR("$saturation", Number, 0, 100)->value();

        if (l) hsl_struct.l = ARGR("$lightness",  Number, 0, 100)->value();

        double alpha = a ? ARGR("$alpha", Number, 0, 1.0)->value() : color->a();

        return hsla_impl(hsl_struct.h, hsl_struct.s, hsl_struct.l, alpha, ctx, pstate);

      }

      if (a) {

        double alpha = ARGR("$alpha", Number, 0, 1.0)->value();

        return SASS_MEMORY_NEW(Color,

                               pstate,

                               color->r(),

                               color->g(),

                               color->b(),

                               alpha);

      }

      error("not enough arguments for `change-color'", pstate);

      // unreachable

      return color;

    }

    template <size_t range>

    static double cap_channel(double c) {

      if      (c > range) return range;

      else if (c < 0)     return 0;

      else                return c;

    }

    Signature ie_hex_str_sig = "ie-hex-str($color)";

    BUILT_IN(ie_hex_str)

    {

      Color_Ptr c = ARG("$color", Color);

      double r = cap_channel<0xff>(c->r());

      double g = cap_channel<0xff>(c->g());

      double b = cap_channel<0xff>(c->b());

      double a = cap_channel<1>   (c->a()) * 255;

      std::stringstream ss;

      ss << '#' << std::setw(2) << std::setfill('0');

      ss << std::hex << std::setw(2) << static_cast<unsigned long>(Sass::round(a, ctx.c_options.precision));

      ss << std::hex << std::setw(2) << static_cast<unsigned long>(Sass::round(r, ctx.c_options.precision));

      ss << std::hex << std::setw(2) << static_cast<unsigned long>(Sass::round(g, ctx.c_options.precision));

      ss << std::hex << std::setw(2) << static_cast<unsigned long>(Sass::round(b, ctx.c_options.precision));

      std::string result(ss.str());

      for (size_t i = 0, L = result.length(); i < L; ++i) {

        result[i] = std::toupper(result[i]);

      }

      return SASS_MEMORY_NEW(String_Quoted, pstate, result);

    }

    ///////////////////

    // STRING FUNCTIONS

    ///////////////////

    Signature unquote_sig = "unquote($string)";

    BUILT_IN(sass_unquote)

    {

      AST_Node_Obj arg = env["$string"];

      if (String_Quoted_Ptr string_quoted = Cast<String_Quoted>(arg)) {

        String_Constant_Ptr result = SASS_MEMORY_NEW(String_Constant, pstate, string_quoted->value());

        // remember if the string was quoted (color tokens)

        result->is_delayed(true); // delay colors

        return result;

      }

      else if (String_Constant_Ptr str = Cast<String_Constant>(arg)) {