package javax.media.opengl.glsl;

import javax.media.opengl.*;

import java.util.HashMap;
import java.util.Iterator;
import java.nio.*;
import java.io.PrintStream;

public class ShaderProgram {
    public ShaderProgram() {
        id = getNextID();
    }

    public boolean linked() {
        return programLinked;
    }

    public boolean inUse() {
        return programInUse;
    }

    public int program() { return shaderProgram; }

    /**
     * returns the uniq shader id as an integer
     * @see #key()
     */
    public int        id() { return id.intValue(); }

    /**
     * returns the uniq shader id as an Integer
     *
     * @see #id()
     */
    public Integer    key() { return id; }

    /**
     * @see #glReleaseAllVertexAttributes
     */
    public synchronized void release(GL2ES2 gl) {
        release(gl, false);
    }

    /**
     * @see #glReleaseAllVertexAttributes
     */
    public synchronized void release(GL2ES2 gl, boolean releaseShaderToo) {
        glUseProgram(gl, false);
        for(Iterator iter=shaderMap.values().iterator(); iter.hasNext(); ) {
            ShaderCode shaderCode = (ShaderCode) iter.next();
            gl.glDetachShader(shaderProgram, shaderCode.shader());
            if(releaseShaderToo) {
                shaderCode.release(gl);
            }
        }
        shaderMap.clear();
        gl.glDeleteProgram(shaderProgram);
        shaderProgram=-1;
    }

    //
    // ShaderCode handling
    //

    /**
     * Adds a new shader to a this non running program.
     *
     * @return false if the program is in use, or the shader already exist,
     *         otherwise true.
     */
    public synchronized boolean add(ShaderCode shaderCode) {
        if(shaderMap.containsKey(shaderCode.key())) return false;
        shaderMap.put(shaderCode.key(), shaderCode);
        return true;
    }

    public synchronized ShaderCode getShader(int id) {
        return (ShaderCode) shaderMap.get(new Integer(id));
    }

    //
    // Program handling
    //

    /**
     * Replace a shader in a 'running' program.
     * Refetches all previously bin/get attribute names
     * and resets all attribute data as well
     *
     * @see getAttribLocation
     * @param gl 
     * @param oldShaderID the to be replace Shader
     * @param newShader   the new ShaderCode
     * @param verboseOut  the optional verbose outputstream
     * @throws GLException is the program is not linked
     *
     * @see #glRefetchAttribLocations
     * @see #glResetAllVertexAttributes
     * @see #glReplaceShader
     */
    public synchronized boolean glReplaceShader(GL2ES2 gl, int oldShaderID, ShaderCode newShader, PrintStream verboseOut) {
        if(!programLinked) throw new GLException("Program is not linked");
        boolean shaderWasInUse = programInUse;
        glUseProgram(gl, false);
        if(!newShader.compile(gl, verboseOut)) {
            return false;
        } 
        if(oldShaderID>=0) {
            ShaderCode oldShader = (ShaderCode) shaderMap.remove(new Integer(oldShaderID));
            if(null!=oldShader) {
                gl.glDetachShader(shaderProgram, oldShader.shader());
            }
        }
        add(newShader);

        gl.glAttachShader(shaderProgram, newShader.shader());
        gl.glLinkProgram(shaderProgram);
        if ( ! gl.glIsProgramValid(shaderProgram, System.err) )  {
            return false;
        }

        if(shaderWasInUse) {
            glUseProgram(gl, true);
        }
        return true;
    }

    public synchronized boolean link(GL2ES2 gl, PrintStream verboseOut) {
        if(programLinked) throw new GLException("Program is already linked");

        if(0>shaderProgram) {
            shaderProgram = gl.glCreateProgram();
        }

        for(Iterator iter=shaderMap.values().iterator(); iter.hasNext(); ) {
            ShaderCode shaderCode = (ShaderCode) iter.next();
            if(!shaderCode.compile(gl, verboseOut)) {
                return false;
            }
            gl.glAttachShader(shaderProgram, shaderCode.shader());
        }

        // Link the program
        gl.glLinkProgram(shaderProgram);

        programLinked = gl.glIsProgramValid(shaderProgram, System.err);

        return programLinked;
    }

    public boolean equals(Object obj) {
        if(this==obj) return true;
        if(obj instanceof ShaderCode) {
            return id()==((ShaderCode)obj).id();
        }
        return false;
    }
    public int hashCode() {
        return id.intValue();
    }
    public String toString() {
        StringBuffer buf = new StringBuffer();
        buf.append("ShaderProgram[id="+id);
        buf.append(", linked="+programLinked+", inUse="+programInUse+", program: "+shaderProgram+", [");
        for(Iterator iter=shaderMap.values().iterator(); iter.hasNext(); ) {
            buf.append((ShaderCode) iter.next());
            buf.append(" ");
        }
        buf.append("]");
        return buf.toString();
    }

    protected synchronized void glUseProgram(GL2ES2 gl, boolean on) {
        if(!programLinked) throw new GLException("Program is not linked");
        if(programInUse==on) return;
        gl.glUseProgram(on?shaderProgram:0);
        programInUse = on;

        //Throwable tX = new Throwable("Info: ShaderProgram.glUseProgram: "+on);
        //tX.printStackTrace();

    }

    protected boolean programLinked = false;
    protected boolean programInUse = false;
    protected int shaderProgram=-1;
    protected HashMap shaderMap = new HashMap();
    protected Integer    id = null;

    private static synchronized Integer getNextID() {
        return new Integer(nextID++);
    }
    protected static int nextID = 1;
}