/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package aQute.shell.runtime;

import java.util.*;

import org.osgi.service.command.*;

public class Closure extends Reflective implements Function {
    private static final long serialVersionUID = 1L;
    final CharSequence        source;
    final Closure             parent;
    CommandSessionImpl        session;
    List<Object>              parms;

    Closure(CommandSessionImpl session, Closure parent, CharSequence source) {
        this.session = session;
        this.parent = parent;
        this.source = source;
    }

    public Object execute(CommandSession x, List<Object> values)
            throws Exception {
        parms = values;
        Parser parser = new Parser(source);
        ArrayList<Pipe> pipes = new ArrayList<Pipe>();
        List<List<List<CharSequence>>> program = parser.program();

        for (List<List<CharSequence>> statements : program) {
            Pipe current = new Pipe(this, statements);

            if (pipes.isEmpty()) {
                current.setIn(session.in);
                current.setOut(session.out);
            } else {
                Pipe previous = pipes.get(pipes.size() - 1);
                previous.connect(current);
            }
            pipes.add(current);
        }
        if (pipes.size() == 0)
            return null;

        if (pipes.size() == 1) {
            pipes.get(0).run();
        } else {
            for (Pipe pipe : pipes) {
                pipe.start();
            }
            for (Pipe pipe : pipes) {
                pipe.join();
            }
        }

        Pipe last = pipes.get(pipes.size() - 1);
        if (last.exception != null)
            throw last.exception;

        if (last.result instanceof Object[]) {
            return Arrays.asList((Object[]) last.result);
        }
        return last.result;
    }

    Object executeStatement(List<CharSequence> statement) throws Exception {
        Object result;
        List<Object> values = new ArrayList<Object>();
        Object cmd = eval(statement.remove(0));
        for (CharSequence token : statement)
            values.add(eval(token));

        result = execute(cmd, values);
        return result;
    }

    private Object execute(Object cmd, List<Object> values) throws Exception {
        if (cmd == null) {
            if (values.isEmpty())
                return null;
            else
                throw new IllegalArgumentException(
                        "Command name evaluates to null");
        }

        // Now there are the following cases
        // <string> '=' statement // complex assignment
        // <string> statement // cmd call
        // <object> // value of <object>
        // <object> statement // method call

        if (cmd instanceof CharSequence) {
            String scmd = cmd.toString();

            if (values.size() > 0 && "=".equals(values.get(0))) {
                if (values.size() == 0)
                    return session.variables.remove(scmd);
                else {
                    Object value = execute(values.get(1), values.subList(2,
                            values.size()));
                    return assignment(scmd, value);
                }
            } else {
                String scopedFunction = scmd;
                Object x = get(scmd);
                if ( !(x instanceof Function) ) {
                    if (scmd.indexOf(':') < 0) {
                        scopedFunction = "*:" + scmd;
                    }
                    x = get(scopedFunction);
                    if (x == null || !(x instanceof Function)) {
                        if (values.isEmpty())
                            return scmd;
                        throw new IllegalArgumentException("Command not found:  "
                                + scopedFunction);
                    } 
                 }
                return ((Function) x).execute(session, values);
            }
        } else {
            if (values.isEmpty())
                return cmd;
            else
                return method(session, cmd, values.remove(0).toString(), values);
        }
    }

    private Object assignment(Object name, Object value) {
        session.variables.put(name, value);
        return value;
    }

    private Object eval(CharSequence seq) throws Exception {
        int end = seq.length();
        switch (seq.charAt(0)) {
        case '$':
            return var(seq);
        case '<':
            Closure c = new Closure(session, this, seq.subSequence(1, end - 1));
            return c.execute(session, parms);
        case '[':
            return array(seq.subSequence(1, end - 1));

        case '{':
            return new Closure(session, this, seq.subSequence(1, end - 1));

        default:
            String result = new Parser(seq).unescape();
            if ("null".equals(result))
                return null;
            if ("true".equalsIgnoreCase(result))
                return true;
            if ("false".equalsIgnoreCase(result))
                return false;
            return seq;
        }
    }

    private Object array(CharSequence array) throws Exception {
        List<Object> list = new ArrayList<Object>();
        Map<Object, Object> map = new LinkedHashMap<Object, Object>();
        Parser p = new Parser(array);

        while (!p.eof()) {
            CharSequence token = p.value();

            p.ws();
            if (p.peek() == '=') {
                p.next();
                p.ws();
                if (!p.eof()) {
                    CharSequence value = p.messy();
                    map.put(eval(token), eval(value));
                }
            } else
                list.add(eval(token));

            if (p.peek() == ',')
                p.next();
            p.ws();
        }
        p.ws();
        if (!p.eof())
            throw new IllegalArgumentException("Invalid array syntax: " + array);

        if (map.size() != 0 && list.size() != 0)
            throw new IllegalArgumentException(
                    "You can not mix maps and arrays: " + array);

        if (map.size() > 0)
            return map;
        else
            return list;
    }

    private Object var(CharSequence var) throws Exception {
        String name = eval(var.subSequence(1, var.length())).toString();
        return get(name);
    }

    /**
     * 
     * @param name
     * @return
     */
    private Object get(String name) {
        if (parms != null) {
            if ("it".equals(name))
                return parms.get(0);
            if ("args".equals(name))
                return parms;

            if (name.length() == 1 && Character.isDigit(name.charAt(0)))
                return parms.get(name.charAt(0) - '0');
        }
        return session.get(name);
    }
}