/*
 * Copyright 2013 Simon Taddiken
 *
 * This file is part of Polly HTTP API.
 *
 * Polly HTTP API is free software: you can redistribute it and/or modify 
 * it under the terms of the GNU General Public License as published by 
 * the Free Software Foundation, either version 3 of the License, or (at 
 * your option) any later version.
 *
 * Polly HTTP API 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 General Public License for 
 * more details.
 *
 * You should have received a copy of the GNU General Public License along 
 * with Polly HTTP API. If not, see http://www.gnu.org/licenses/.
 */
package de.skuzzle.polly.http.internal;

import java.lang.annotation.Annotation;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import de.skuzzle.polly.http.api.Controller;
import de.skuzzle.polly.http.api.HttpEvent;
import de.skuzzle.polly.http.api.HttpEvent.RequestMode;
import de.skuzzle.polly.http.api.handler.HttpEventHandler;
import de.skuzzle.polly.http.api.HttpException;
import de.skuzzle.polly.http.annotations.Param;
import de.skuzzle.polly.http.api.ParameterHandler;
import de.skuzzle.polly.http.api.answers.HttpAnswer;


class ReflectionHttpHandler implements HttpEventHandler {
    
    private final String uri;
    private final Method handler;
    private final RequestMode mode;
    private final Controller carrier;
    private final HttpServletServerImpl parent;
    private final boolean matchExactly;
    
    
    public ReflectionHttpHandler(RequestMode mode, String uri, Controller carrier, 
            Method handler, HttpServletServerImpl parent, boolean matchExactly) {
        this.matchExactly = matchExactly;
        this.mode = mode;
        this.carrier = carrier;
        this.uri = uri;
        this.handler = handler;
        this.parent = parent;
    }
    
    
    
    @Override
    public HttpAnswer handleHttpEvent(String registered, HttpEvent e, 
            HttpEventHandler next) throws HttpException {
        
        if (e.getMode() != this.mode || 
                this.matchExactly && !e.getPlainUri().equals(this.uri)) {
            return next.handleHttpEvent(registered, e, next);
        }
        
        
        // extract actual parameters from the request
        final Object[] params = new Object[this.handler.getParameterTypes().length];
        for (int i = 0; i < this.handler.getParameterTypes().length; ++i) {
            final Annotation[] an = this.handler.getParameterAnnotations()[i];
            
            // extract parameter name from annotated method parameter
            // INVARIANT: every parameter is annotated!
            Param key = null;
            for (Annotation a : an) {
                if (a instanceof Param) {
                    key = (Param) a;
                    break;
                }
            }
            
            // value associated with that key in the current request 
            String sValue = e.parameterMap(this.mode).get(key.value());
            if (sValue == null) {
                if (key.optional()) {
                    sValue = key.defaultValue();
                } else {
                    // this handler does not match, try the next one
                    return next.handleHttpEvent(registered, e, next);
                }
            }
            
            final Class<?> type = this.handler.getParameterTypes()[i];
            final ParameterHandler ph = this.parent.findHandler(type, key.typeHint());
            // INVARIANT: ph can not be null
            assert ph != null;
            
            params[i] = ph.parse(sValue);
        }
        
        // execute the function
        try {
            final Controller copy = this.carrier.bind(registered, e);
            return (HttpAnswer) this.handler.invoke(copy, params);
        } catch (InvocationTargetException e1) {
            if (e1.getTargetException() instanceof HttpException) {
                throw (HttpException) e1.getTargetException();
            }
            throw new HttpException(e1.getTargetException());
        } catch (Exception e1) {
            throw new HttpException(e1);
        }
    }
}