// Copyright (C) 2022 RozK
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

// Adapted from https://www.khronos.org/opengl/wiki/Tutorial:_OpenGL_3.0_Context_Creation_(GLX)

#include "../display.hpp"
#include "display_glx.hpp"
#include "../events/events_x11.hpp"
#include <cstdio>
#include <cstring>

static bool rk_error_occured = false;

#define GLX_CONTEXT_MAJOR_VERSION_ARB 0x2091
#define GLX_CONTEXT_MINOR_VERSION_ARB 0x2092
typedef GLXContext (*rk_CreateContextAttribsFunc)(Display *, GLXFBConfig, GLXContext, Bool, int const *);

static int const rk_context_attribs[] = {
    GLX_CONTEXT_MAJOR_VERSION_ARB, 3,
    GLX_CONTEXT_MINOR_VERSION_ARB, 2,
    GLX_CONTEXT_PROFILE_MASK_ARB, GLX_CONTEXT_ES_PROFILE_BIT_EXT,
    None
};

static void rk_x11_printf(
    char const * messsage) {
    printf("[X11] %s\n", messsage);
}

static void rk_glx_printf(
    char const * messsage) {
    printf("[GLX] %s\n", messsage);
}

bool rk_extension_supported(
    char const * extensions,
    char const * extension) {
    char const * where = strchr(extension, ' ');
    if (where || *extension == '\0') {
        return false;
    }
    for (char const * start = extensions;;) {
        where = strstr(start, extension);
        if (!where) {
            break;
        }
        char const * const terminator = where + strlen(extension);
        if ((where == start || *(where - 1) == ' ') && (*terminator == ' ' || *terminator == '\0')) {
            return true;
        }
        start = terminator;
    }
    return false;
}

rk_func_ptr rk_resolve_extension(
    char const * extensions,
    char const * extension,
    char const * fn) {
    if (!extensions || !extension || !fn) {
        return nullptr;
    }
    if (!rk_extension_supported(extensions, extension)) {
        printf("[GLX] Extension %s not supported\n", extension);
        return nullptr;
    }
    rk_func_ptr const ptr = glXGetProcAddressARB(reinterpret_cast<GLubyte const *>(fn));
    if (!ptr) {
        printf("[GLX] Function %s::%s not found\n", extension, fn);
    }
    return ptr;
}

static int rk_error_handler(
    Display * display,
    XErrorEvent * event) {
    rk_error_occured = true;
    return 0;
}

rk_display_t rk_create_display(
    rk_char const * name,
    rk_uint width,
    rk_uint height) {
    if (!name || !width || !height) {
        return nullptr;
    };
    rk_display_glx * const display = new rk_display_glx;
    display->display = XOpenDisplay(nullptr);
    display->window = 0;
    display->colormap = 0;
    display->context = nullptr;
    if (!display->display) {
        rk_x11_printf("Failed to open X display.");
        rk_destroy_display(reinterpret_cast<rk_display_t>(display));
        return nullptr;
    }

    int glx_major, glx_minor;
    if (!glXQueryVersion(display->display, &glx_major, &glx_minor) ||
            (glx_major == 1 && glx_minor < 3) || glx_major < 1) {
        rk_glx_printf("Invalid GLX version.");
        rk_destroy_display(reinterpret_cast<rk_display_t>(display));
        return nullptr;
    }

    char const * const glx_exts = glXQueryExtensionsString(display->display, DefaultScreen(display->display));
    // rk_glx_printf(glx_exts);
    rk_CreateContextAttribsFunc const glXCreateContextAttribs = reinterpret_cast<rk_CreateContextAttribsFunc>(
        rk_resolve_extension(glx_exts, "GLX_ARB_create_context", "glXCreateContextAttribsARB"));
    if (!glXCreateContextAttribs) {
        rk_destroy_display(reinterpret_cast<rk_display_t>(display));
        return nullptr;
    }

    int fb_count = 0;
    GLXFBConfig * fb_configs;
    bool const srgb_ext = rk_extension_supported(glx_exts, "GLX_EXT_framebuffer_sRGB");
    if (srgb_ext) {
        rk_glx_printf("GLX_EXT_framebuffer_sRGB extension supported.");
        int const visual_attribs[] = { GLX_FRAMEBUFFER_SRGB_CAPABLE_EXT, True, GLX_DOUBLEBUFFER, True, None };
        fb_configs = glXChooseFBConfig(display->display, DefaultScreen(display->display), visual_attribs, &fb_count);
    } else {
        int const visual_attribs[] = { GLX_DOUBLEBUFFER, True, None };
        fb_configs = glXChooseFBConfig(display->display, DefaultScreen(display->display), visual_attribs, &fb_count);
    }
    printf("[GLX] Found %d framebuffer configs.\n", fb_count);
    if (!fb_configs || !fb_count) {
        rk_glx_printf("Failed to retrieve framebuffer configs.");
        rk_destroy_display(reinterpret_cast<rk_display_t>(display));
        return nullptr;
    }
    GLXFBConfig fb_config;
    int rs = 0;
    int gs = 0;
    int bs = 0;
    int as = 0;
    int ds = 0;
    int ss = 0;
    for (int fb_index = 0; fb_index < fb_count; ++fb_index) {
        GLXFBConfig _config = fb_configs[fb_index];
        int _rs = 0;
        int _gs = 0;
        int _bs = 0;
        int _as = 0;
        int _ds = 0;
        int _ss = 0;
        glXGetFBConfigAttrib(display->display, _config, GLX_RED_SIZE, &_rs);
        glXGetFBConfigAttrib(display->display, _config, GLX_GREEN_SIZE, &_gs);
        glXGetFBConfigAttrib(display->display, _config, GLX_BLUE_SIZE, &_bs);
        glXGetFBConfigAttrib(display->display, _config, GLX_ALPHA_SIZE, &_as);
        glXGetFBConfigAttrib(display->display, _config, GLX_DEPTH_SIZE, &_ds);
        glXGetFBConfigAttrib(display->display, _config, GLX_STENCIL_SIZE, &_ss);
        if ((_rs >= rs && _gs >= gs && _bs >= bs && _as >= as && _ds >= ds && _ss >= ss) &&
            (_rs >  rs || _gs >  gs || _bs >  bs || _as >  as || _ds >  ds || _ss >  ss)) {
            XVisualInfo * const vi = glXGetVisualFromFBConfig(display->display, _config);
            if (vi) {
                XFree(vi);
                rs = _rs;
                gs = _gs;
                bs = _bs;
                as = _as;
                ds = _ds;
                ss = _ss;
                fb_config = _config;
            }
        }
    }
    printf("[RK] Select framebuffer config R%dG%dB%dA%d D%dS%d.\n", rs, gs, bs, as, ds, ss);
    if (srgb_ext) {
        int srgb = 0;
        glXGetFBConfigAttrib(display->display, fb_config, GLX_FRAMEBUFFER_SRGB_CAPABLE_EXT, &srgb);
        if (srgb) {
            rk_glx_printf("sRGB framebuffer selected.");
        }
    }

    XVisualInfo * const vi = glXGetVisualFromFBConfig(display->display, fb_config);
    Window root = RootWindow(display->display, vi->screen);
    display->colormap = XCreateColormap(display->display, root, vi->visual, AllocNone);
    XSetWindowAttributes win_attributes;
    win_attributes.colormap = display->colormap;
    win_attributes.event_mask = RK_EVENTS_MASK;
    display->window = XCreateWindow(display->display, root,
        0, 0, width, height, 0, vi->depth, InputOutput, vi->visual, CWColormap | CWEventMask, &win_attributes);
    XFree(vi);
    XFree(fb_configs);
    if (!display->window) {
        rk_x11_printf("Failed to create window.");
        rk_destroy_display(reinterpret_cast<rk_display_t>(display));
        return nullptr;
    }
    XStoreName(display->display, display->window, name);
    XMapWindow(display->display, display->window);

    rk_error_occured = false;
    int (*oldHandler)(Display *, XErrorEvent *) = XSetErrorHandler(&rk_error_handler);
    display->context = glXCreateContextAttribs(display->display, fb_config, 0, True, rk_context_attribs);
    XSync(display->display, False);
    XSetErrorHandler(oldHandler);
    if (rk_error_occured || !display->context) {
        rk_glx_printf("Failed to create context.");
        rk_destroy_display(reinterpret_cast<rk_display_t>(display));
        return nullptr;
    }

    if (!glXIsDirect(display->display, display->context)) {
        rk_glx_printf("Warning: Rendering context is indirect.");
    }
    glXMakeCurrent(display->display, display->window, display->context);
    if (srgb_ext) {
        glEnable(GL_FRAMEBUFFER_SRGB_EXT);
        if (glIsEnabled(GL_FRAMEBUFFER_SRGB_EXT)) {
            rk_glx_printf("sRGB framebuffer enabled.");
        }
    }

    return reinterpret_cast<rk_display_t>(display);
}

void rk_destroy_display(
    rk_display_t _display) {
    rk_display_glx * const display = reinterpret_cast<rk_display_glx *>(_display);
    if (display) {
        if (display->display) {
            glXMakeCurrent(display->display, 0, nullptr);
            if (display->context) {
                glXDestroyContext(display->display, display->context);
            }
            if (display->window) {
                XDestroyWindow(display->display, display->window);
            }
            if (display->colormap) {
                XFreeColormap(display->display, display->colormap);
            }
            XCloseDisplay(display->display);
        }
        delete display;
    }
}

void rk_swap_buffers(
    rk_display_t _display) {
    rk_display_glx const * const display = reinterpret_cast<rk_display_glx const *>(_display);
    if (display && display->display && display->window) {
        glXSwapBuffers(display->display, display->window);
    }
}