package space.engine;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.FloatBuffer;
import java.nio.IntBuffer;
import java.util.HashMap;

import org.lwjgl.opengl.ARBShaderObjects;
import org.lwjgl.opengl.ARBVertexShader;
import org.lwjgl.opengl.GL20;
import org.newdawn.slick.SlickException;
import org.newdawn.slick.util.ResourceLoader;

public class ShaderProgram {

    private static boolean strict = true;

    public static void setStrictMode(boolean enabled) {
        strict = enabled;
    }

    public static boolean isStrictMode() {
        return strict;
    }

    // TODO: move to outer level ?
    public static class Shader {

        private String source;
        private int type;
        private int id;
        private String log = "";

        public Shader(int type, String source) {
            if (source==null)
                throw new IllegalArgumentException("shader source code must not be null");
            this.source = source;
            this.type = type;
            id = createShader(type, source);
        }

        public boolean valid() {
            return id!=0;
        }

        private int createShader(int type, String source) {
            int shader = ARBShaderObjects.glCreateShaderObjectARB(type);
            if (shader==0)
                return 0;

            ARBShaderObjects.glShaderSourceARB(shader, source);
            ARBShaderObjects.glCompileShaderARB(shader);
            int comp = ARBShaderObjects.glGetObjectParameteriARB(shader, GL20.GL_COMPILE_STATUS);
            if (comp==0) {
                int len = ARBShaderObjects.glGetObjectParameteriARB(shader, GL20.GL_INFO_LOG_LENGTH);
                log = ARBShaderObjects.glGetInfoLogARB(shader, len);
                return 0;
            }
            return shader;
        }

        public void release() {
            if (id!=0) {
                ARBShaderObjects.glDeleteObjectARB(id);
                id = 0;
            }
        }

        public String getLog() {
            return log;
        }

        public int getID() {
            return id;
        }

        public int getType() {
            return type;
        }

        public String getSource() {
            return source;
        }
    }

    private int program;

    private String log = "";

    protected HashMap<String, Integer> uniforms = new HashMap<String, Integer>();
    protected HashMap<String, Integer> attributes = new HashMap<String, Integer>();


    private Shader vert, frag;

    public static ShaderProgram loadProgram(String vertFile, String fragFile) throws SlickException {
        return new ShaderProgram(loadSource(vertFile), loadSource(fragFile));
    }

    public static String loadSource(String ref) throws SlickException {
        InputStream in = ResourceLoader.getResourceAsStream(ref);
        try { return loadSource(in); }
        catch (SlickException e) {
            throw new SlickException("could not load source file: "+ref);
        }
    }

    public static String loadSource(InputStream in) throws SlickException{
        try {
            BufferedReader br = new BufferedReader(new InputStreamReader(in));
            String line = "";
            String txt = "";
            while ((line=br.readLine()) != null)
                txt += line + "\n";
            br.close();
            return txt.trim();
        } catch (IOException e) {
            throw new SlickException("could not load source file");
        }
    }

    public ShaderProgram(String vertexShader, String fragShader) {
        this(new Shader(GL20.GL_VERTEX_SHADER, vertexShader),
             new Shader(GL20.GL_FRAGMENT_SHADER, fragShader));
    }

    public ShaderProgram(Shader vertexShader, Shader fragShader) {
        if (vertexShader==null || fragShader==null)
            throw new IllegalArgumentException("shaders must be non-null");
        this.vert = vertexShader;
        this.frag = fragShader;
        log += vert.getLog() + frag.getLog();
        this.program = compile();
        if (valid()) {
            fetchUniforms();
//          fetchAttributes();
        }
    }

    private int compile() {
        if (!vert.valid() || !frag.valid())
            return 0;
        int program = ARBShaderObjects.glCreateProgramObjectARB();
        ARBShaderObjects.glAttachObjectARB(program, vert.getID());
        ARBShaderObjects.glAttachObjectARB(program, frag.getID());
        ARBShaderObjects.glLinkProgramARB(program);
        //GL20.glValidateProgram(program);
        int comp = ARBShaderObjects.glGetObjectParameteriARB(program, GL20.GL_LINK_STATUS);
        if (comp==0) {
            int len = ARBShaderObjects.glGetObjectParameteriARB(program, GL20.GL_INFO_LOG_LENGTH);
            log += ARBShaderObjects.glGetInfoLogARB(program, len);
            return 0;
        }
        return program;
    }



    /**
     * Returns the log for this shader program as well as any shaders attached to this program.
     * @return
     */
    public String getLog() {
        return log;
    }

    public void unbind() {
        ARBShaderObjects.glUseProgramObjectARB(0);
    }

    public void bind() {
        if (!valid())
            throw new IllegalStateException("trying to enable a program that is not valid");
        ARBShaderObjects.glUseProgramObjectARB(program);
    }

    public void release() {
        ARBShaderObjects.glDetachObjectARB(program, vert.getID());
        ARBShaderObjects.glDetachObjectARB(program, frag.getID());
        vert.release();
        frag.release();
        ARBShaderObjects.glDeleteObjectARB(program);
    }

    public int getID() {
        return program;
    }

    public boolean valid() {
        return program != 0;
    }

//  protected int findAttributeLocation(String name) {
//      int location = attributes.get(name);
//      if (location!=-1)
//          return location;
//      location = ARBVertexShader.glGetAttribLocationARB(program, name);
//      if (location == -1 && strict)
//          throw new IllegalArgumentException("no active attribute by name '"+name+"'");
//      attributes.put(name, location);
//      return location;
//  }

    protected int findUniformLocation(String name) {
        Integer locI = uniforms.get(name);
        int location = locI==null ? -1 : locI.intValue();
        if (location!=-1)
            return location;
        location = ARBShaderObjects.glGetUniformLocationARB(program, name);
        if (location == -1 && strict)
            throw new IllegalArgumentException("no active uniform by name '"+name+"' (disable strict compiling to suppress warnings)");
        uniforms.put(name, location);
        return location;
    }

    private void fetchUniforms() {
        int len = ARBShaderObjects.glGetObjectParameteriARB(program, GL20.GL_ACTIVE_UNIFORMS);
        //max length of all uniforms stored in program
        int strLen = ARBShaderObjects.glGetObjectParameteriARB(program, GL20.GL_ACTIVE_UNIFORM_MAX_LENGTH);

        for (int i=0; i<len; i++) {
            String name = ARBShaderObjects.glGetActiveUniformARB(program, i, strLen);
            int id = ARBShaderObjects.glGetUniformLocationARB(program, name);
            uniforms.put(name, id);
        }
    }

//  private void fetchAttributes() {
//      int len = ARBShaderObjects.glGetObjectParameteriARB(program, GL20.GL_ACTIVE_ATTRIBUTES);
//      //max length of all uniforms stored in program
//      int strLen = ARBShaderObjects.glGetObjectParameteriARB(program, GL20.GL_ACTIVE_ATTRIBUTE_MAX_LENGTH);
//      for (int i=0; i<len; i++) {
//          String name = ARBVertexShader.glGetActiveAttribARB(program, i, strLen);
//          int id = ARBVertexShader.glGetAttribLocationARB(program, name);
//          uniforms.put(name, id);
//      }
//  }

    public int getUniformID(String name) {
        return findUniformLocation(name);
    }

//  public int getAttributeID(String name) {
//      return findAttributeLocation(name);
//  }

//  public String[] getAttributes() {
//      return attributes.keySet().toArray(new String[attributes.size()]);
//  }

    public String[] getUniformNames() {
        return uniforms.keySet().toArray(new String[uniforms.size()]);
    }

    public Shader getVertexShader() {
        return vert;
    }

    public Shader getFragmentShader() {
        return frag;
    }

    public boolean getUniform(String name, FloatBuffer buf) {
        int id = getUniformID(name);
        if (id==-1) return false;
        ARBShaderObjects.glGetUniformARB(program, id, buf);
        return true;
    }

    public boolean getUniform(String name, IntBuffer buf) {
        int id = getUniformID(name);
        if (id==-1) return false;
        ARBShaderObjects.glGetUniformARB(program, id, buf);
        return true;
    }

    public boolean hasUniform(String name) {
        return uniforms.containsKey(name);
    }

    public boolean hasAttribute(String name) {
        return attributes.containsKey(name);
    }

    public void setUniform1f(String name, float f) {
        int id = getUniformID(name);
        if (id==-1) return;
        ARBShaderObjects.glUniform1fARB(id, f);
    }

    public void setUniform1i(String name, int i) {
        int id = getUniformID(name);
        if (id==-1) return;
        ARBShaderObjects.glUniform1iARB(id, i);
    }

    public void setUniform2f(String name, float a, float b) {
        int id = getUniformID(name);
        if (id==-1) return;
        ARBShaderObjects.glUniform2fARB(id, a, b);
    }

    public void setUniform3f(String name, float a, float b, float c) {
        int id = getUniformID(name);
        if (id==-1) return;
        ARBShaderObjects.glUniform3fARB(id, a, b, c);
    }

    public void setUniform4f(String name, float a, float b, float c, float d) {
        int id = getUniformID(name);
        if (id==-1) return;
        ARBShaderObjects.glUniform4fARB(id, a, b, c, d);
    }


    // TODO: include more setUniforms/getUniforms
}