//
// Copyright (C) 2002-2005  3Dlabs Inc. Ltd.
// Copyright (C) 2017 Google, Inc.
//
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//    notice, this list of conditions and the following disclaimer.
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//    Redistributions in binary form must reproduce the above
//    copyright notice, this list of conditions and the following
//    disclaimer in the documentation and/or other materials provided
//    with the distribution.
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//    contributors may be used to endorse or promote products derived
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// POSSIBILITY OF SUCH DAMAGE.
//

#pragma once

#include <vector>
#include <string>
#include <fstream>
#include <algorithm>

#include "./../glslang/Public/ShaderLang.h"

// Default include class for normal include convention of search backward
// through the stack of active include paths (for nested includes).
// Can be overridden to customize.
class DirStackFileIncluder : public glslang::TShader::Includer {
public:
    DirStackFileIncluder() : externalLocalDirectoryCount(0) { }

    virtual IncludeResult* includeLocal(const char* headerName,
                                        const char* includerName,
                                        size_t inclusionDepth) override
    {
        return readLocalPath(headerName, includerName, (int)inclusionDepth);
    }

    virtual IncludeResult* includeSystem(const char* headerName,
                                         const char* /*includerName*/,
                                         size_t /*inclusionDepth*/) override
    {
        return readSystemPath(headerName);
    }

    // Externally set directories. E.g., from a command-line -I<dir>.
    //  - Most-recently pushed are checked first.
    //  - All these are checked after the parse-time stack of local directories
    //    is checked.
    //  - This only applies to the "local" form of #include.
    //  - Makes its own copy of the path.
    virtual void pushExternalLocalDirectory(const std::string& dir)
    {
        directoryStack.push_back(dir);
        externalLocalDirectoryCount = (int)directoryStack.size();
    }

    virtual void releaseInclude(IncludeResult* result) override
    {
        if (result != nullptr) {
            delete [] static_cast<tUserDataElement*>(result->userData);
            delete result;
        }
    }

    virtual ~DirStackFileIncluder() override { }

protected:
    typedef char tUserDataElement;
    std::vector<std::string> directoryStack;
    int externalLocalDirectoryCount;

    // Search for a valid "local" path based on combining the stack of include
    // directories and the nominal name of the header.
    virtual IncludeResult* readLocalPath(const char* headerName, const char* includerName, int depth)
    {
        // Discard popped include directories, and
        // initialize when at parse-time first level.
        directoryStack.resize(depth + externalLocalDirectoryCount);
        if (depth == 1)
            directoryStack.back() = getDirectory(includerName);

        // Find a directory that works, using a reverse search of the include stack.
        for (auto it = directoryStack.rbegin(); it != directoryStack.rend(); ++it) {
            std::string path = *it + '/' + headerName;
            std::replace(path.begin(), path.end(), '\\', '/');
            std::ifstream file(path, std::ios_base::binary | std::ios_base::ate);
            if (file) {
                directoryStack.push_back(getDirectory(path));
                return newIncludeResult(path, file, (int)file.tellg());
            }
        }

        return nullptr;
    }

    // Search for a valid <system> path.
    // Not implemented yet; returning nullptr signals failure to find.
    virtual IncludeResult* readSystemPath(const char* /*headerName*/) const
    {
        return nullptr;
    }

    // Do actual reading of the file, filling in a new include result.
    virtual IncludeResult* newIncludeResult(const std::string& path, std::ifstream& file, int length) const
    {
        char* content = new tUserDataElement [length];
        file.seekg(0, file.beg);
        file.read(content, length);
        return new IncludeResult(path, content, length, content);
    }

    // If no path markers, return current working directory.
    // Otherwise, strip file name and return path leading up to it.
    virtual std::string getDirectory(const std::string path) const
    {
        size_t last = path.find_last_of("/\\");
        return last == std::string::npos ? "." : path.substr(0, last);
    }
};