/**
The contents of this file are subject to the Mozilla Public License Version 1.1 
(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.mozilla.org/MPL/ 
Software distributed under the License is distributed on an "AS IS" basis, 
WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for the 
specific language governing rights and limitations under the License. 

The Original Code is "AbstractSegment.java".  Description: 
"Provides common functionality needed by implementers of the Segment interface.
  Implementing classes should define all the fields for the segment they represent 
  in their constructor" 

The Initial Developer of the Original Code is University Health Network. Copyright (C) 
2001.  All Rights Reserved. 

Contributor(s): ______________________________________. 

Alternatively, the contents of this file may be used under the terms of the 
GNU General Public License (the  ?GPL?), in which case the provisions of the GPL are 
applicable instead of those above.  If you wish to allow use of your version of this 
file only under the terms of the GPL and not to allow others to use your version 
of this file under the MPL, indicate your decision by deleting  the provisions above 
and replace  them with the notice and other provisions required by the GPL License.  
If you do not delete the provisions above, a recipient may use your version of 
this file under either the MPL or the GPL. 

 */

package ca.uhn.hl7v2.model;

import java.lang.reflect.InvocationTargetException;
import java.util.ArrayList;
import java.util.List;

import ca.uhn.hl7v2.HL7Exception;
import ca.uhn.hl7v2.parser.EncodingCharacters;
import ca.uhn.hl7v2.parser.ModelClassFactory;

/**
 * <p>
 * Provides common functionality needed by implementers of the Segment
 * interface.
 * </p>
 * <p>
 * Implementing classes should define all the fields for the segment they
 * represent in their constructor. The add() method is useful for this purpose.
 * </p>
 * <p>
 * For example the constructor for an MSA segment might contain the following
 * code:<br>
 * <code>this.add(new ID(), true, 2, null);<br>
 * this.add(new ST(), true, 20, null);<br>...</code>
 * </p>
 * 
 * @author Bryan Tripp (bryan_tripp@sourceforge.net)
 */
public abstract class AbstractSegment extends AbstractStructure implements
                Segment {

        /**
         * Do not use
         */
        static final String ERROR_MSH_1_OR_2_NOT_SET = "Can not invoke parse(String) on a segment if the encoding characters (MSH-1 and MSH-2) are not already correctly set on the message";

        private static final long serialVersionUID = -6686329916234746948L;
        
        private List<List<Type>> fields;
        private List<Class<? extends Type>> types;
        private List<Boolean> required;
        private List<Integer> length;
        private List<Object> args;
        private List<Integer> maxReps;
        private List<String> names;

        /**
         * Calls the abstract init() method to create the fields in this segment.
         * 
         * @param parent
         *            parent group
         * @param factory
         *            all implementors need a model class factory to find datatype
         *            classes, so we include it as an arg here to emphasize that
         *            fact ... AbstractSegment doesn't actually use it though
         */
        public AbstractSegment(Group parent, ModelClassFactory factory) {
                super(parent);
                this.fields = new ArrayList<List<Type>>();
                this.types = new ArrayList<Class<? extends Type>>();
                this.required = new ArrayList<Boolean>();
                this.length = new ArrayList<Integer>();
                this.args = new ArrayList<Object>();
                this.maxReps = new ArrayList<Integer>();
                this.names = new ArrayList<String>();
        }

        /**
         * Returns an array of Field objects at the specified location in the
         * segment. In the case of non-repeating fields the array will be of length
         * one. Fields are numbered from 1.
         */
        public Type[] getField(int number) throws HL7Exception {
                List<Type> retVal = getFieldAsList(number);
                return retVal.toArray(new Type[retVal.size()]); // note: fields are
                                                                                                                // numbered from 1 from
                                                                                                                // the user's
                                                                                                                // perspective
        }

        /**
         * @see ca.uhn.hl7v2.model.Segment#isEmpty()
         */
        public boolean isEmpty() throws HL7Exception {
                for (int i = 1; i <= numFields(); i++) {
                        Type[] types = getField(i);
                        for (Type type : types) {
                                if (!type.isEmpty()) return false;
                        }
                }
                return true;
        }

        /**
         * Returns an array of a specific type class
         */
        protected <T extends Type> T[] getTypedField(int number, T[] array) {
                List<Type> retVal;
                try {
                        retVal = getFieldAsList(number);
                        @SuppressWarnings("unchecked")
                        List<T> cast = (List<T>) (List<?>) retVal;
                        return cast.toArray(array);
        } catch (ClassCastException cce) {
            log.error("Unexpected problem obtaining field value.  This is a bug.", cce);
            throw new RuntimeException(cce);
        } catch (HL7Exception he) {
            log.error("Unexpected problem obtaining field value.  This is a bug.", he);
            throw new RuntimeException(he);
        }
        }
                
        
    protected int getReps(int number) { 
        try { 
            return getFieldAsList(number).size();
        } catch (HL7Exception he) {
            log.error("Unexpected problem obtaining field value.  This is a bug.", he);
            throw new RuntimeException(he);
        }       
    }   

        private List<Type> getFieldAsList(int number) throws HL7Exception {
                ensureEnoughFields(number);

                if (number < 1 || number > fields.size()) {
                        throw new HL7Exception("Can't retrieve field " + number
                                        + " from segment " + this.getClass().getName()
                                        + " - there are only " + fields.size() + " fields.");
                }

                return fields.get(number - 1);

        }

        /**
         * Returns a specific repetition of field at the specified index. If there
         * exist fewer repetitions than are required, the number of repetitions can
         * be increased by specifying the lowest repetition that does not yet exist.
         * For example if there are two repetitions but three are needed, the third
         * can be created and accessed using the following code: <br>
         * <code>Type t = getField(x, 3);</code>
         * 
         * @param number
         *            the field number (starting at 1)
         * @param rep
         *            the repetition number (starting at 0)
         * @throws HL7Exception
         *             if field index is out of range, if the specified repetition
         *             is greater than the maximum allowed, or if the specified
         *             repetition is more than 1 greater than the existing # of
         *             repetitions.
         */
        public Type getField(int number, int rep) throws HL7Exception {

                ensureEnoughFields(number);

                if (number < 1 || number > fields.size()) {
                        throw new HL7Exception("Can't get field " + number + " in segment "
                                        + getName() + " - there are currently only "
                                        + fields.size() + " reps.");
                }

                List<Type> arr = fields.get(number - 1);

                // check if out of range ...
                if (rep > arr.size())
                        throw new HL7Exception("Can't get repetition " + rep
                                        + " from field " + number + " - there are currently only "
                                        + arr.size() + " reps.");

                // add a rep if necessary ...
                if (rep == arr.size()) {
                        Type newType = createNewType(number);
                        arr.add(newType);
                }

                return arr.get(rep);
        }

        /**
         * Returns a specific repetition of field with concrete type at the specified index
         */
        protected <T extends Type> T getTypedField(int number, int rep) {
                try {
                        @SuppressWarnings("unchecked") T retVal = (T)getField(number, rep);
                        return retVal;
        } catch (ClassCastException cce) {
            log.error("Unexpected problem obtaining field value.  This is a bug.", cce);
            throw new RuntimeException(cce);
        } catch (HL7Exception he) {
            log.error("Unexpected problem obtaining field value.  This is a bug.", he);
            throw new RuntimeException(he);
        }
        }
        
        /**
         * <p>
         * Attempts to create an instance of a field type without using reflection.
         * </p>
         * <p>
         * Note that the default implementation just returns <code>null</code>, and
         * it is not neccesary to override this method to provide any particular
         * behaviour. When a new field instance is needed within a segment, this
         * method is tried first, and if it returns <code>null</code>, reflection is
         * used instead. Implementations of this method is auto-generated by the
         * source generator module.
         * </p>
         * 
         * @return Returns a newly instantiated type, or <code>null</code> if not
         *         possible
         * @param field
         *            Field number - Note that this is zero indexed!
         */
        protected Type createNewTypeWithoutReflection(int field) {
                return null;
        }

        /**
         * Creates a new instance of the Type at the given field number in this
         * segment.
         */
        private Type createNewType(int field) throws HL7Exception {
                Type retVal = createNewTypeWithoutReflection(field - 1);
                if (retVal != null) {
                        return retVal;
                }

                int number = field - 1;
                Class<? extends Type> c = this.types.get(number);

                Type newType = null;
                try {
                        Object[] args = getArgs(number);
                        Class<?>[] argClasses = new Class[args.length];
                        for (int i = 0; i < args.length; i++) {
                                if (args[i] instanceof Message) {
                                        argClasses[i] = Message.class;
                                } else {
                                        argClasses[i] = args[i].getClass();
                                }
                        }
                        newType = c.getConstructor(argClasses).newInstance(args);
                } catch (IllegalAccessException iae) {
                        throw new HL7Exception("Can't access class " + c.getName() + " ("
                                        + iae.getClass().getName() + "): " + iae.getMessage());
                } catch (InstantiationException ie) {
                        throw new HL7Exception("Can't instantiate class " + c.getName()
                                        + " (" + ie.getClass().getName() + "): " + ie.getMessage());
                } catch (InvocationTargetException ite) {
                        throw new HL7Exception("Can't instantiate class " + c.getName()
                                        + " (" + ite.getClass().getName() + "): "
                                        + ite.getMessage());
                } catch (NoSuchMethodException nme) {
                        throw new HL7Exception("Can't instantiate class " + c.getName()
                                        + " (" + nme.getClass().getName() + "): "
                                        + nme.getMessage());
                }
                return newType;
        }

        // defaults to {this.getMessage}
        private Object[] getArgs(int fieldNum) {
                Object[] result = null;

                Object o = this.args.get(fieldNum);
                if (o != null && o instanceof Object[]) {
                        result = (Object[]) o;
                } else {
                        result = new Object[] { getMessage() };
                }

                return result;
        }

        /**
         * Returns true if the given field is required in this segment - fields are
         * numbered from 1.
         * 
         * @throws HL7Exception
         *             if field index is out of range.
         */
        public boolean isRequired(int number) throws HL7Exception {
                if (number < 1 || number > required.size()) {
                        throw new HL7Exception("Can't retrieve optionality of field "
                                        + number + " from segment " + this.getClass().getName()
                                        + " - there are only " + fields.size() + " fields.");
                }

                try {
                        return required.get(number - 1);
                } catch (Exception e) {
                        throw new HL7Exception("Can't retrieve optionality of field "
                                        + number + ": " + e.getMessage());
                }
        }

        /**
         * Returns the maximum length of the field at the given index, in characters
         * - fields are numbered from 1.
         * 
         * @throws HL7Exception
         *             if field index is out of range.
         */
        public int getLength(int number) throws HL7Exception {
                if (number < 1 || number > length.size()) {
                        throw new HL7Exception("Can't retrieve max length of field "
                                        + number + " from segment " + this.getClass().getName()
                                        + " - there are only " + fields.size() + " fields.");
                }

                try {
                        return length.get(number - 1); // fields #d from 1 to user
                } catch (Exception e) {
                        throw new HL7Exception("Can't retrieve max length of field "
                                        + number + ": " + e.getMessage());
                }

        }

        /**
         * Returns the number of repetitions of this field that are allowed.
         * 
         * @throws HL7Exception
         *             if field index is out of range.
         */
        public int getMaxCardinality(int number) throws HL7Exception {
                if (number < 1 || number > length.size()) {
                        throw new HL7Exception("Can't retrieve cardinality of field "
                                        + number + " from segment " + this.getClass().getName()
                                        + " - there are only " + fields.size() + " fields.");
                }

                try {
                        return maxReps.get(number - 1); // fields #d from 1 to user
                } catch (Exception e) {
                        throw new HL7Exception("Can't retrieve max repetitions of field "
                                        + number + ": " + e.getMessage());
                }
        }

        /**
         * @deprecated Use {@link #add(Class, boolean, int, int, Object[], String)}
         */
        protected void add(Class<? extends Type> c, boolean required, int maxReps,
                        int length, Object[] constructorArgs) throws HL7Exception {
                add(c, required, maxReps, length, constructorArgs, null);
        }

        /**
         * Adds a field to the segment. The field is initially empty (zero
         * repetitions). The field number is sequential depending on previous add()
         * calls. Implementing classes should use the add() method in their
         * constructor in order to define fields in their segment.
         * 
         * @param c
         *            the class of the datatype for the field - this should inherit
         *            from {@link Type}
         * @param required
         *            whether a value for the field is required in order for the
         *            segment to be valid
         * @param maxReps
         *            The maximum number of repetitions for the field. Note that 0 implies that there is no
         *            limit, and 1 implies that the field may not repeat.
         * @param length
         *            the maximum length of each repetition of the field (in
         *            characters)
         * @param constructorArgs
         *            This parameter provides an array of objects that will be used 
         *            as constructor arguments
         *            if new instances of this class are created (use null for
         *            zero-arg constructor). To determine the appropriate value for
         *            this parameter, consult the javadoc for the specific datatype class
         *            passed to the first argument of this method, and provide an array
         *            which satisfies the requirements of its constructor. For example, most
         *            datatypes take a single {@link Message} argument in their constructor. 
         *            In that case, the appropriate value for this argument is as follows:
         *            <code>new Object[]{ getMessage() }</code>
         * @param name
         *            A textual description of the name of the field
         * @throws HL7Exception
         *             if the given class does not inherit from Type or if it can
         *             not be instantiated.
         */
        protected void add(Class<? extends Type> c, boolean required, int maxReps,
                        int length, Object[] constructorArgs, String name)
                        throws HL7Exception {
                List<Type> arr = new ArrayList<Type>();
                this.types.add(c);
                this.fields.add(arr);
                this.required.add(required);
                this.length.add(length);
                this.args.add(constructorArgs);
                this.maxReps.add(maxReps);
                this.names.add(name);
        }

        /**
         * Called from getField(...) methods. If a field has been requested that
         * doesn't exist (eg getField(15) when only 10 fields in segment) adds
         * Varies fields to the end of the segment up to the required number.
         */
        private void ensureEnoughFields(int fieldRequested) {
                int fieldsToAdd = fieldRequested - this.numFields();
                if (fieldsToAdd < 0) {
                        fieldsToAdd = 0;
                }

                try {
                        for (int i = 0; i < fieldsToAdd; i++) {
                                this.add(Varies.class, false, 0, 65536, null); // using 65536
                                                                                                                                // following
                                                                                                                                // example of
                                                                                                                                // OBX-5
                        }
                } catch (HL7Exception e) {
                        log.error(
                                        "Can't create additional generic fields to handle request for field "
                                                        + fieldRequested, e);
                }
        }

        public static void main(String[] args) {
                /*
                 * try { Message mess = new TestMessage(); MSH msh = new MSH(mess);
                 * 
                 * //get empty array Type[] ts = msh.getField(1);
                 * System.out.println("Got Type array of length " + ts.length);
                 * 
                 * //get first field Type t = msh.getField(1, 0);
                 * System.out.println("Got a Type of class " + t.getClass().getName());
                 * 
                 * //get array now Type[] ts2 = msh.getField(1);
                 * System.out.println("Got Type array of length " + ts2.length);
                 * 
                 * //set a value ST str = (ST)t; str.setValue("hello");
                 * 
                 * //get first field Type t2 = msh.getField(1, 0);
                 * System.out.println("Got a Type of class " + t.getClass().getName());
                 * System.out.println("It's value is " + ((ST)t2).getValue());
                 * 
                 * msh.getFieldSeparator().setValue("thing");
                 * System.out.println("Field Sep: " +
                 * msh.getFieldSeparator().getValue());
                 * 
                 * msh.getConformanceStatementID(0).setValue("ID 1");
                 * msh.getConformanceStatementID(1).setValue("ID 2");
                 * System.out.println("Conf ID #2: " +
                 * msh.getConformanceStatementID(1).getValue());
                 * 
                 * ID[] cid = msh.getConformanceStatementID();
                 * System.out.println("CID: " + cid); for (int i = 0; i < cid.length;
                 * i++) { System.out.println("Conf ID element: " + i + ": " +
                 * cid[i].getValue()); }
                 * msh.getConformanceStatementID(3).setValue("this should fail");
                 * 
                 * 
                 * } catch (HL7Exception e) { e.printStackTrace(); }
                 */
        }

        /**
         * Returns the number of fields defined by this segment (repeating fields
         * are not counted multiple times).
         */
        public int numFields() {
                return this.fields.size();
        }

        /**
         * Returns the class name (excluding package).
         * 
         * @see Structure#getName()
         */
        public String getName() {
                String fullName = this.getClass().getName();
                return fullName.substring(fullName.lastIndexOf('.') + 1,
                                fullName.length());
        }

        /**
         * Sets the segment name. This would normally be called by a Parser.
         */
        /*
         * public void setName(String name) { this.name = name; }
         */

        /**
         * {@inheritDoc}
         */
        public String[] getNames() {
                return names.toArray(new String[names.size()]);
        }

        /**
         * {@inheritDoc }
         * 
         * <p>
         * <b>Note that this method will not currently work to parse an MSH segment
         * if the encoding characters are not already set. This limitation should be
         * resolved in a future version</b>
         * </p>
         */
        public void parse(String string) throws HL7Exception {
                if (string == null) {
                        throw new NullPointerException("String can not be null");
                }
                
                EncodingCharacters encodingCharacters;
                try {
                        encodingCharacters = EncodingCharacters.getInstance(getMessage());
                } catch (HL7Exception e) {
                        throw new HL7Exception(ERROR_MSH_1_OR_2_NOT_SET);
                }
                clear();
                getMessage().getParser().parse(this, string, encodingCharacters);
        }

        /**
         * {@inheritDoc }
         */
        public String encode() throws HL7Exception {
                return getMessage().getParser().doEncode(this,
                                EncodingCharacters.getInstance(getMessage()));
        }

        /**
         * Removes a repetition of a given field by name. For example, if a PID
         * segment contains 10 repetitions a "Patient Identifier List" field and
         * "Patient Identifier List" is supplied with an index of 2, then this call
         * would remove the 3rd repetition.
         * 
         * @return The removed structure
         * @throws HL7Exception
         *             if the named Structure is not part of this Group.
         */
        protected Type removeRepetition(int fieldNum, int index)
                        throws HL7Exception {
                if (fieldNum < 1 || fieldNum > fields.size()) {
                        throw new HL7Exception("The field " + fieldNum
                                        + " does not exist in the segment "
                                        + this.getClass().getName());
                }

                String name = names.get(fieldNum - 1);
                List<Type> list = fields.get(fieldNum - 1);
                if (list.size() == 0) {
                        throw new HL7Exception("Invalid index: " + index + ", structure "
                                        + name + " has no repetitions");
                }
                if (list.size() <= index) {
                        throw new HL7Exception("Invalid index: " + index + ", structure "
                                        + name + " must be between 0 and " + (list.size() - 1));
                }

                return list.remove(index);
        }

        /**
         * Inserts a repetition of a given Field into repetitions of that field by
         * name.
         * 
         * @return The newly created and inserted field
         * @throws HL7Exception
         *             if the named Structure is not part of this Group.
         */
        protected Type insertRepetition(int fieldNum, int index)
                        throws HL7Exception {
                if (fieldNum < 1 || fieldNum > fields.size()) {
                        throw new HL7Exception("The field " + fieldNum
                                        + " does not exist in the segment "
                                        + this.getClass().getName());
                }

                List<Type> list = fields.get(fieldNum - 1);
                Type newType = createNewType(fieldNum);

                list.add(index, newType);

                return newType;
        }

        /**
         * Clears all data from this segment
         */
        public void clear() {
                for (List<Type> next : fields) {
                        next.clear();
                }
        }

}