//
// Copyright (c) 2008-2013 the Urho3D project.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//

#include "Precompiled.h"
#include "ShaderParser.h"
#include "XMLElement.h"

namespace Urho3D
{

bool ShaderParser::Parse(ShaderType type, const XMLElement& element, const Vector<String>& globalDefines, const Vector<String>& globalDefineValues)
{
    if (globalDefines.Size() != globalDefineValues.Size())
    {
        errorMessage_ = "Amount of global define names and values does not match";
        return false;
    }
    
    globalDefines_ = globalDefines;
    globalDefineValues_ = globalDefineValues;
    errorMessage_.Clear();
    options_.Clear();
    combinations_.Clear();
    
    XMLElement shader = element.GetChild("shader");
    while (shader)
    {
        String typeName = String(shader.GetAttribute("type")).ToLower();
        if (typeName.Empty() || (type == VS && typeName == "vs") || (type == PS && typeName == "ps"))
        {
            if (!ParseOptions(shader))
                return false;
            BuildCombinations();
            return true;
        }
        
        shader = shader.GetNext("shader");
    }
    
    return true;
}

bool ShaderParser::HasCombination(const String& name) const
{
    return combinations_.Contains(name);
}

ShaderCombination ShaderParser::GetCombination(const String& name) const
{
    ShaderCombination dest;
    
    HashMap<String, unsigned>::ConstIterator i = combinations_.Find(name);
    if (i != combinations_.End())
    {
        dest.name_ = name;
        
        for (unsigned j = 0; j < options_.Size(); ++j)
        {
            if (i->second_ & (1 << j))
            {
                for (unsigned k = 0; k < options_[j].defines_.Size(); ++k)
                {
                    dest.defines_.Push(options_[j].defines_[k]);
                    dest.defineValues_.Push(options_[j].defineValues_[k]);
                }
                for (unsigned k = 0; k < globalDefines_.Size(); ++k)
                {
                    dest.defines_.Push(globalDefines_[k]);
                    dest.defineValues_.Push(globalDefineValues_[k]);
                }
            }
        }
    }

    return dest;
}

bool ShaderParser::ParseOptions(const XMLElement& element)
{
    XMLElement option = element.GetChild();
    while (option)
    {
        String value = option.GetName().ToLower();
        if (value == "variation" || value == "option")
        {
            String name = option.GetAttribute("name");
            
            ShaderOption newOption;
            newOption.name_ = name;
            newOption.isVariation_ = value == "variation";
            
            String simpleDefine = option.GetAttribute("define");
            if (!simpleDefine.Empty())
            {
                Vector<String> nameAndValue = simpleDefine.Split('=');
                if (nameAndValue.Size() == 2)
                {
                    newOption.defines_.Push(nameAndValue[0]);
                    newOption.defineValues_.Push(nameAndValue[1]);
                }
                else
                {
                    newOption.defines_.Push(simpleDefine);
                    newOption.defineValues_.Push("1");
                }
            }
            
            String simpleExclude = option.GetAttribute("exclude");
            if (!simpleExclude.Empty())
                newOption.excludes_.Push(simpleExclude);
            
            String simpleInclude = option.GetAttribute("include");
            if (!simpleInclude.Empty())
                newOption.includes_.Push(simpleInclude);
            
            String simpleRequire = option.GetAttribute("require");
            if (!simpleRequire.Empty())
                newOption.requires_.Push(simpleRequire);
            
            XMLElement define = option.GetChild("define");
            while (define)
            {
                String defineName = define.GetAttribute("name");
                Vector<String> nameAndValue = defineName.Split('=');
                if (nameAndValue.Size() == 2)
                {
                    newOption.defines_.Push(nameAndValue[0]);
                    newOption.defineValues_.Push(nameAndValue[1]);
                }
                else
                {
                    newOption.defines_.Push(defineName);
                    newOption.defineValues_.Push("1");
                }
                define = define.GetNext("define");
            }
            
            XMLElement exclude = option.GetChild("exclude");
            while (exclude)
            {
                newOption.excludes_.Push(exclude.GetAttribute("name"));
                exclude = exclude.GetNext("exclude");
            }
            
            XMLElement include = option.GetChild("include");
            while (include)
            {
                newOption.includes_.Push(include.GetAttribute("name"));
                include = include.GetNext("include");
            }
            
            XMLElement require = option.GetChild("require");
            while (require)
            {
                newOption.requires_.Push(require.GetAttribute("name"));
                require = require.GetNext("require");
            }
            
            #ifdef RASPI
            newOption.defines_.Push("RASPI");
            newOption.defineValues_.Push("1");
            #endif

            options_.Push(newOption);
            if (options_.Size() > 31)
            {
                errorMessage_ = "Maximum of 31 shader options exceeded";
                return false;
            }
        }
        else
        {
            errorMessage_ = "Unrecognized element " + value + " in shader definition";
            return false;
        }
        
        option = option.GetNext();
    }
    
    return true;
}

void ShaderParser::BuildCombinations()
{
    unsigned combinations = 1;
    unsigned numVariationGroups = 0;
    HashSet<unsigned> usedCombinations;
    HashMap<String, unsigned> nameToIndex;
    
    for (unsigned i = 0; i < options_.Size(); ++i)
    {
        combinations *= 2;
        nameToIndex[options_[i].name_] = i;
        if (options_[i].isVariation_ && (i == 0 || !options_[i - 1].isVariation_))
            ++numVariationGroups;
    }
    
    // Preprocess includes/excludes for faster combination handling
    for (Vector<ShaderOption>::Iterator i = options_.Begin(); i != options_.End(); ++i)
    {
        i->excludeIndices_.Resize(i->excludes_.Size());
        i->includeIndices_.Resize(i->includes_.Size());
        
        for (unsigned j = 0; j < i->excludes_.Size(); ++j)
            i->excludeIndices_[j] = nameToIndex[i->excludes_[j]];
        for (unsigned j = 0; j < i->includes_.Size(); ++j)
            i->includeIndices_[j] = nameToIndex[i->includes_[j]];
    }
    
    // Preprocess requirements
    for (unsigned i = 0; i < options_.Size(); ++i)
    {
        for (unsigned j = 0; j < options_[i].requires_.Size(); ++j)
        {
            unsigned bits = 0;
            for (unsigned l = 0; l < options_.Size(); ++l)
            {
                if (l != i)
                {
                    if (options_[l].name_ == options_[i].requires_[j])
                        bits |= 1 << l;
                    else
                    {
                        for (unsigned m = 0; m < options_[l].defines_.Size(); ++m)
                        {
                            if (options_[l].defines_[m] == options_[i].requires_[j])
                            {
                                bits |= 1 << l;
                                break;
                            }
                        }
                    }
                }
            }
            
            // If requirements are not satisfied by any option, check global defines
            if (!bits)
            {
                for (unsigned l = 0; l < globalDefines_.Size(); ++l)
                {
                    if (globalDefines_[l] == options_[i].requires_[j])
                    {
                        bits |= 0x80000000;
                        break;
                    }
                }
            }
            
            options_[i].requirementBits_.Push(bits);
        }
    }
    
    for (unsigned i = 0; i < combinations; ++i)
    {
        // Variations/options active on this particular combination
        unsigned active = i;
        unsigned variationsActive = 0;
        bool skipThis = false;
        
        // Check for excludes & includes first
        for (unsigned j = 0; j < options_.Size(); ++j)
        {
            if ((active >> j) & 1)
            {
                for (unsigned k = 0; k < options_[j].includeIndices_.Size(); ++k)
                    active |= 1 << options_[j].includeIndices_[k];
                
                for (unsigned k = 0; k < options_[j].excludeIndices_.Size(); ++k)
                    active &= ~(1 << options_[j].excludeIndices_[k]);
                
                // Skip dummy separators (options without name and defines)
                if (options_[j].name_.Empty() && !options_[j].isVariation_ && options_[j].defines_.Empty())
                    active &= ~(1 << j);
                
                // If it's a variation, exclude all other variations in the same group
                if (options_[j].isVariation_)
                {
                    for (unsigned k = j - 1; k < options_.Size(); --k)
                    {
                        if (options_[k].isVariation_)
                            active &= ~(1 << k);
                        else
                            break;
                    }
                    for (unsigned k = j + 1; k < options_.Size(); ++k)
                    {
                        if (options_[k].isVariation_)
                            active &= ~(1 << k);
                        else
                            break;
                    }
                    
                    ++variationsActive;
                }
            }
        }
        
        // Check that combination is correct: a variation chosen from all groups, and is unique
        if (variationsActive < numVariationGroups || usedCombinations.Contains(active))
            continue;
        
        // Check for required defines, which may yet cause this combination to be skipped
        unsigned compareBits = active | 0x80000000;
        for (unsigned j = 0; j < options_.Size(); ++j)
        {
            if (active & (1 << j))
            {
                for (unsigned l = 0; l < options_[j].requirementBits_.Size(); ++l)
                {
                    if (!(compareBits & options_[j].requirementBits_[l]))
                    {
                        skipThis = true;
                        break;
                    }
                }
            }
        }
        
        if (skipThis)
            continue;
        
        String combinationName;
        
        // Build shader combination name from active options
        for (unsigned j = 0; j < options_.Size(); ++j)
        {
            if (active & (1 << j) && options_[j].name_.Length())
                combinationName += options_[j].name_;
        }
        
        combinations_[combinationName] = active;
        usedCombinations.Insert(active);
    }
}

}