#include "Skybox.hpp"

#include "Shader.hpp"
#include <stb_image.h>

#include <algorithm>
#include <filesystem>
#include <iostream>

namespace Fs = std::filesystem;

namespace renderer {
Skybox::Skybox () : mTexID( 0 ), mVAO( 0 ), mVBO( 0 ), mInitialized( false ) {}

Skybox::~Skybox () {
    if( mVBO )
        glDeleteBuffers( 1, &mVBO );
    if( mVAO )
        glDeleteVertexArrays( 1, &mVAO );
    if( mTexID )
        glDeleteTextures( 1, &mTexID );
}

static std::string toLower ( const std::string& s ) {
    std::string out = s;
    std::transform( out.begin(), out.end(), out.begin(), [] ( unsigned char c ) { return std::tolower( c ); } );
    return out;
}

bool Skybox::loadFromDirectory ( const std::string& dirPath ) {

    std::vector<std::string> faceTokens = { "right", "left", "top", "bottom", "front", "back" };
    std::vector<std::string> faces( 6 );

    if( !Fs::exists( dirPath ) || !Fs::is_directory( dirPath ) ) {
        std::cerr << "Skybox directory does not exist: " << dirPath << std::endl;
        return false;
    }

    for( auto& entry : Fs::directory_iterator( dirPath ) ) {
        if( !entry.is_regular_file() )
            continue;
        auto        name  = entry.path().filename().string();
        std::string lname = toLower( name );
        for( size_t i = 0; i < faceTokens.size(); ++i ) {
            if( lname.find( faceTokens[i] ) != std::string::npos ) {
                faces[i] = entry.path().string();
            }
        }
    }

    for( size_t i = 0; i < faces.size(); ++i ) {
        if( faces[i].empty() ) {
            std::cerr << "Missing skybox face for token: " << faceTokens[i] << std::endl;
            return false;
        }
    }

    return loadFaces( faces );
}

bool Skybox::loadFaces ( const std::vector<std::string>& faces ) {
    glGenTextures( 1, &mTexID );
    glBindTexture( GL_TEXTURE_CUBE_MAP, mTexID );

    stbi_set_flip_vertically_on_load( false );
    for( unsigned i = 0; i < faces.size(); ++i ) {
        int            w, h, ch;
        unsigned char* data = stbi_load( faces[i].c_str(), &w, &h, &ch, 0 );
        if( !data ) {
            std::cerr << "Failed to load skybox face: " << faces[i] << std::endl;
            glBindTexture( GL_TEXTURE_CUBE_MAP, 0 );
            return false;
        }
        GLenum format = ( ch == 4 ) ? GL_RGBA : GL_RGB;
        glTexImage2D( GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, 0, format, w, h, 0, format, GL_UNSIGNED_BYTE, data );
        stbi_image_free( data );
    }

    glTexParameteri( GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
    glTexParameteri( GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
    glTexParameteri( GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE );
    glTexParameteri( GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE );
    glTexParameteri( GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE );

    glBindTexture( GL_TEXTURE_CUBE_MAP, 0 );

    initMesh();
    mInitialized = true;
    return true;
}

void Skybox::initMesh () {

    float skyboxVertices[] = { -1.0f, 1.0f, -1.0f, -1.0f, -1.0f, -1.0f, 1.0f, -1.0f, -1.0f,
                               1.0f, -1.0f, -1.0f, 1.0f, 1.0f, -1.0f, -1.0f, 1.0f, -1.0f,

                               -1.0f, -1.0f, 1.0f, -1.0f, -1.0f, -1.0f, -1.0f, 1.0f, -1.0f,
                               -1.0f, 1.0f, -1.0f, -1.0f, 1.0f, 1.0f, -1.0f, -1.0f, 1.0f,

                               1.0f, -1.0f, -1.0f, 1.0f, -1.0f, 1.0f, 1.0f, 1.0f, 1.0f,
                               1.0f, 1.0f, 1.0f, 1.0f, 1.0f, -1.0f, 1.0f, -1.0f, -1.0f,

                               -1.0f, -1.0f, 1.0f, -1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f,
                               1.0f, 1.0f, 1.0f, 1.0f, -1.0f, 1.0f, -1.0f, -1.0f, 1.0f,

                               -1.0f, 1.0f, -1.0f, 1.0f, 1.0f, -1.0f, 1.0f, 1.0f, 1.0f,
                               1.0f, 1.0f, 1.0f, -1.0f, 1.0f, 1.0f, -1.0f, 1.0f, -1.0f,

                               -1.0f, -1.0f, -1.0f, -1.0f, -1.0f, 1.0f, 1.0f, -1.0f, -1.0f,
                               1.0f, -1.0f, -1.0f, -1.0f, -1.0f, 1.0f, 1.0f, -1.0f, 1.0f };

    glGenVertexArrays( 1, &mVAO );
    glGenBuffers( 1, &mVBO );
    glBindVertexArray( mVAO );
    glBindBuffer( GL_ARRAY_BUFFER, mVBO );
    glBufferData( GL_ARRAY_BUFFER, sizeof( skyboxVertices ), &skyboxVertices, GL_STATIC_DRAW );
    glEnableVertexAttribArray( 0 );
    glVertexAttribPointer( 0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof( float ), (void*)0 );
    glBindVertexArray( 0 );
}

void Skybox::draw ( const glm::mat4& view, const glm::mat4& proj ) {
    if( !mInitialized )
        return;

    static Shader s;
    static bool   shaderLoaded = false;
    if( !shaderLoaded ) {
        s.fromFiles( "apps/openmb/resources/shaders/skybox.vert", "apps/openmb/resources/shaders/skybox.frag" );
        shaderLoaded = true;
    }

    glDepthFunc( GL_LEQUAL );
    glDepthMask( GL_FALSE );

    s.use();

    glm::mat4 viewNoTrans = glm::mat4( glm::mat3( view ) );
    s.setMat4( "view", viewNoTrans );
    s.setMat4( "proj", proj );

    glActiveTexture( GL_TEXTURE0 );
    glBindTexture( GL_TEXTURE_CUBE_MAP, mTexID );
    s.setInt( "skybox", 0 );

    glBindVertexArray( mVAO );
    glDrawArrays( GL_TRIANGLES, 0, 36 );
    glBindVertexArray( 0 );

    glDepthMask( GL_TRUE );
    glDepthFunc( GL_LESS );
}

}   // namespace renderer