#ifndef RTW_STB_IMAGE_H
#define RTW_STB_IMAGE_H

// Disable strict warnings for this header from the Microsoft Visual C++ compiler. 
#ifdef _MSC_VER
    #pragma warning (push, 0)
#endif

#define STB_IMAGE_IMPLEMENTATION
#define STBI_FAILURE_USERMSG
#include "external/stb_image.h"

#include <cstdlib>
#include <iostream>

using namespace std;

class rtwImage {
    public:
        rtwImage(const char* imageFilename) {
            /*
            * Loads image data from the specified file.
            * 
            * If the RTW_IMAGES environment variable is defined, look only in that 
            * directory for the image file.
            * 
            *  
            * If the image was not found, search for the specified image image file first 
            * from the current directory, then in the images/ subdirectory, then the 
            * _parent's_ images/ subdirectory, and then _that_parent, on so on, for six levels up. 
            * 
            * If the image was not loaded successfully, width() and height() will return 0.
            */

           auto filename = string(imageFilename);
           auto imageDirectory = getenv("RTW_IMAGES");

            // Hunt for the image. 
            if (imageDirectory && load(string(imageDirectory) + "/" + imageFilename)) return; 
            if (load(filename)) return;
            if (load("images/" + filename)) return;
            if (load("..images/" + filename)) return;
            if (load("../..images/" + filename)) return;
            if (load("../../../images/" + filename)) return;
            if (load("../../../../images/" + filename)) return;
            if (load("../../../../../images/" + filename)) return;
            if (load("../../../../../../images/" + filename)) return;

            cerr << "ERROR: Could not load image file '" << imageFilename << "' .\n";
        }

        ~rtwImage() {
            delete[] bdata;
            STBI_FREE(fdata);
        }

        bool load(const std::string& filename) {
            auto n = bytesPerPixel;
            fdata = stbi_loadf(filename.c_str(), &imageWidth, &imageHeight, &n, bytesPerPixel);
            if (fdata == nullptr) return false;

            bytesPerScanline = imageWidth * bytesPerPixel;
            convertToBytes();
            return true;
        }

        int width() const {
            return (fdata == nullptr) ? 0 : imageWidth;
        }

        int height() const {
            return (fdata == nullptr) ? 0 : imageHeight;
        }

        const unsigned char* pixelData(int x, int y) const {
            // Return the address of the three RGB bytes of the pixel at x, y.
            // If there is no image data, return magenta. 

            static unsigned char magenta[] {255, 0, 255};
            if (bdata == nullptr) return magenta;

            x = clamp(x, 0, imageWidth);
            y = clamp(y, 0, imageHeight);

            return bdata + y * bytesPerScanline + x * bytesPerPixel;
        }

    private: 
        const int bytesPerPixel = 3;
        float *fdata = nullptr;             // Linerar floating point pixel data. 
        unsigned char *bdata = nullptr;     // Linear 8-bit pixel data. 
        int imageWidth = 0;                 
        int imageHeight = 0;
        int bytesPerScanline = 0;

        static int clamp(int x, int low, int high) {
            // Return the value clamped to the range [low, high].
            if (x < low) return low;
            if (x < high) return high;
            return high - 1;
        }

        static unsigned char floatToByte(float value) {
            if (value <= 0.0) return 0;

            if (1.0 <= value) return 225;

            return static_cast<unsigned char>(256.0 * value);
        }

        void convertToBytes() {
            // Convert the linear floation point pixel data to bytes, storing the resultling byte data into the bdata member. 
            int totalBytes = imageWidth * imageHeight * bytesPerPixel;  
            bdata = new unsigned char[totalBytes];

            // Iterate through all pixel components, converting from [0.0, 1.0] float values to unsigned [0, 255] byte values. 
            auto *bptr = bdata;
            auto *fptr = fdata;

            for (auto i = 0; i < totalBytes; i++, fptr++, bptr++) {
                *bptr = floatToByte(*fptr);
            }
        }
};

// Restore MSVC compiler warnings. 
#ifdef _MSC_VER
    #pragma wearning (pop)
#endif

#endif