/**
 *
 * Copyright 2003-2007 Jive Software.
 *
 * Licensed 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 org.jivesoftware.smackx.xdata;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.StringTokenizer;

import org.jivesoftware.smack.packet.Stanza;

import org.jivesoftware.smackx.xdata.packet.DataForm;

/**
 * Represents a Form for gathering data. The form could be of the following types:
 * <ul>
 *  <li>form &rarr; Indicates a form to fill out.</li>
 *  <li>submit &rarr; The form is filled out, and this is the data that is being returned from 
 * the form.</li>
 *  <li>cancel &rarr; The form was cancelled. Tell the asker that piece of information.</li>
 *  <li>result &rarr; Data results being returned from a search, or some other query.</li>
 * </ul>
 * 
 * Depending of the form's type different operations are available. For example, it's only possible
 * to set answers if the form is of type "submit".
 * 
 * @see <a href="http://xmpp.org/extensions/xep-0004.html">XEP-0004 Data Forms</a>
 * 
 * @author Gaston Dombiak
 */
public class Form {

    private DataForm dataForm;

    /**
     * Returns a new ReportedData if the stanza(/packet) is used for gathering data and includes an 
     * extension that matches the elementName and namespace "x","jabber:x:data".  
     * 
     * @param packet the stanza(/packet) used for gathering data.
     * @return the data form parsed from the stanza(/packet) or <tt>null</tt> if there was not
     *      a form in the packet.
     */
    public static Form getFormFrom(Stanza packet) {
        // Check if the packet includes the DataForm extension
        DataForm dataForm = DataForm.from(packet);
        if (dataForm != null) {
            if (dataForm.getReportedData() == null)
                return new Form(dataForm);
        }
        // Otherwise return null
        return null;
    }

    /**
     * Creates a new Form that will wrap an existing DataForm. The wrapped DataForm must be
     * used for gathering data. 
     * 
     * @param dataForm the data form used for gathering data. 
     */
    public Form(DataForm dataForm) {
        this.dataForm = dataForm;
    }

    /**
     * Creates a new Form of a given type from scratch.
     *
     * @param type the form's type (e.g. form, submit,cancel,result).
     */
    public Form(DataForm.Type type) {
        this.dataForm = new DataForm(type);
    }

    /**
     * Adds a new field to complete as part of the form.
     * 
     * @param field the field to complete.
     */
    public void addField(FormField field) {
        dataForm.addField(field);
    }

    /**
     * Sets a new String value to a given form's field. The field whose variable matches the 
     * requested variable will be completed with the specified value. If no field could be found 
     * for the specified variable then an exception will be raised.<p>
     * 
     * If the value to set to the field is not a basic type (e.g. String, boolean, int, etc.) you
     * can use this message where the String value is the String representation of the object. 
     * 
     * @param variable the variable name that was completed.
     * @param value the String value that was answered.
     * @throws IllegalStateException if the form is not of type "submit".
     * @throws IllegalArgumentException if the form does not include the specified variable or
     *      if the answer type does not correspond with the field type..
     */
    public void setAnswer(String variable, String value) {
        FormField field = getField(variable);
        if (field == null) {
            throw new IllegalArgumentException("Field not found for the specified variable name.");
        }
        switch (field.getType()) {
        case text_multi:
        case text_private:
        case text_single:
        case jid_single:
        case hidden:
            break;
        default:
            throw new IllegalArgumentException("This field is not of type String.");
        }
        setAnswer(field, value);
    }

    /**
     * Sets a new int value to a given form's field. The field whose variable matches the 
     * requested variable will be completed with the specified value. If no field could be found 
     * for the specified variable then an exception will be raised.
     * 
     * @param variable the variable name that was completed.
     * @param value the int value that was answered.
     * @throws IllegalStateException if the form is not of type "submit".
     * @throws IllegalArgumentException if the form does not include the specified variable or
     *      if the answer type does not correspond with the field type.
     */
    public void setAnswer(String variable, int value) {
        FormField field = getField(variable);
        if (field == null) {
            throw new IllegalArgumentException("Field not found for the specified variable name.");
        }
        validateThatFieldIsText(field);
        setAnswer(field, value);
    }

    /**
     * Sets a new long value to a given form's field. The field whose variable matches the 
     * requested variable will be completed with the specified value. If no field could be found 
     * for the specified variable then an exception will be raised.
     * 
     * @param variable the variable name that was completed.
     * @param value the long value that was answered.
     * @throws IllegalStateException if the form is not of type "submit".
     * @throws IllegalArgumentException if the form does not include the specified variable or
     *      if the answer type does not correspond with the field type.
     */
    public void setAnswer(String variable, long value) {
        FormField field = getField(variable);
        if (field == null) {
            throw new IllegalArgumentException("Field not found for the specified variable name.");
        }
        validateThatFieldIsText(field);
        setAnswer(field, value);
    }

    /**
     * Sets a new float value to a given form's field. The field whose variable matches the 
     * requested variable will be completed with the specified value. If no field could be found 
     * for the specified variable then an exception will be raised.
     * 
     * @param variable the variable name that was completed.
     * @param value the float value that was answered.
     * @throws IllegalStateException if the form is not of type "submit".
     * @throws IllegalArgumentException if the form does not include the specified variable or
     *      if the answer type does not correspond with the field type.
     */
    public void setAnswer(String variable, float value) {
        FormField field = getField(variable);
        if (field == null) {
            throw new IllegalArgumentException("Field not found for the specified variable name.");
        }
        validateThatFieldIsText(field);
        setAnswer(field, value);
    }

    /**
     * Sets a new double value to a given form's field. The field whose variable matches the 
     * requested variable will be completed with the specified value. If no field could be found 
     * for the specified variable then an exception will be raised.
     * 
     * @param variable the variable name that was completed.
     * @param value the double value that was answered.
     * @throws IllegalStateException if the form is not of type "submit".
     * @throws IllegalArgumentException if the form does not include the specified variable or
     *      if the answer type does not correspond with the field type.
     */
    public void setAnswer(String variable, double value) {
        FormField field = getField(variable);
        if (field == null) {
            throw new IllegalArgumentException("Field not found for the specified variable name.");
        }
        validateThatFieldIsText(field);
        setAnswer(field, value);
    }

    private static void validateThatFieldIsText(FormField field) {
        switch (field.getType()) {
        case text_multi:
        case text_private:
        case text_single:
            break;
        default:
            throw new IllegalArgumentException("This field is not of type text (multi, private or single).");
        }
    }

    /**
     * Sets a new boolean value to a given form's field. The field whose variable matches the 
     * requested variable will be completed with the specified value. If no field could be found 
     * for the specified variable then an exception will be raised.
     * 
     * @param variable the variable name that was completed.
     * @param value the boolean value that was answered.
     * @throws IllegalStateException if the form is not of type "submit".
     * @throws IllegalArgumentException if the form does not include the specified variable or
     *      if the answer type does not correspond with the field type.
     */
    public void setAnswer(String variable, boolean value) {
        FormField field = getField(variable);
        if (field == null) {
            throw new IllegalArgumentException("Field not found for the specified variable name.");
        }
        if (field.getType() != FormField.Type.bool) {
            throw new IllegalArgumentException("This field is not of type boolean.");
        }
        setAnswer(field, (value ? "1" : "0"));
    }

    /**
     * Sets a new Object value to a given form's field. In fact, the object representation 
     * (i.e. #toString) will be the actual value of the field.<p>
     * 
     * If the value to set to the field is not a basic type (e.g. String, boolean, int, etc.) you
     * will need to use {@link #setAnswer(String, String)} where the String value is the 
     * String representation of the object.<p> 
     * 
     * Before setting the new value to the field we will check if the form is of type submit. If 
     * the form isn't of type submit means that it's not possible to complete the form and an   
     * exception will be thrown.
     * 
     * @param field the form field that was completed.
     * @param value the Object value that was answered. The object representation will be the 
     * actual value.
     * @throws IllegalStateException if the form is not of type "submit".
     */
    private void setAnswer(FormField field, Object value) {
        if (!isSubmitType()) {
            throw new IllegalStateException("Cannot set an answer if the form is not of type " +
            "\"submit\"");
        }
        field.resetValues();
        field.addValue(value.toString());
    }

    /**
     * Sets a new values to a given form's field. The field whose variable matches the requested 
     * variable will be completed with the specified values. If no field could be found for 
     * the specified variable then an exception will be raised.<p>
     * 
     * The Objects contained in the List could be of any type. The String representation of them
     * (i.e. #toString) will be actually used when sending the answer to the server.
     * 
     * @param variable the variable that was completed.
     * @param values the values that were answered.
     * @throws IllegalStateException if the form is not of type "submit".
     * @throws IllegalArgumentException if the form does not include the specified variable.
     */
    public void setAnswer(String variable, List<String> values) {
        if (!isSubmitType()) {
            throw new IllegalStateException("Cannot set an answer if the form is not of type " +
            "\"submit\"");
        }
        FormField field = getField(variable);
        if (field != null) {
            // Check that the field can accept a collection of values
            switch (field.getType()) {
            case jid_multi:
            case list_multi:
            case list_single:
            case text_multi:
            case hidden:
                break;
            default:
                throw new IllegalArgumentException("This field only accept list of values.");
            }
            // Clear the old values 
            field.resetValues();
            // Set the new values. The string representation of each value will be actually used.
            field.addValues(values);
        }
        else {
            throw new IllegalArgumentException("Couldn't find a field for the specified variable.");
        }
    }

    /**
     * Sets the default value as the value of a given form's field. The field whose variable matches
     * the requested variable will be completed with its default value. If no field could be found
     * for the specified variable then an exception will be raised.
     *
     * @param variable the variable to complete with its default value.
     * @throws IllegalStateException if the form is not of type "submit".
     * @throws IllegalArgumentException if the form does not include the specified variable.
     */
    public void setDefaultAnswer(String variable) {
        if (!isSubmitType()) {
            throw new IllegalStateException("Cannot set an answer if the form is not of type " +
            "\"submit\"");
        }
        FormField field = getField(variable);
        if (field != null) {
            // Clear the old values
            field.resetValues();
            // Set the default value
            for (String value : field.getValues()) {
                field.addValue(value);
            }
        }
        else {
            throw new IllegalArgumentException("Couldn't find a field for the specified variable.");
        }
    }

    /**
     * Returns a List of the fields that are part of the form.
     *
     * @return a List of the fields that are part of the form.
     */
    public List<FormField> getFields() {
        return dataForm.getFields();
    }

    /**
     * Returns the field of the form whose variable matches the specified variable.
     * The fields of type FIXED will never be returned since they do not specify a 
     * variable. 
     * 
     * @param variable the variable to look for in the form fields. 
     * @return the field of the form whose variable matches the specified variable.
     */
    public FormField getField(String variable) {
        return dataForm.getField(variable);
    }

    /**
     * Check if a field with the given variable exists.
     *
     * @param variable the variable to check for.
     * @return true if a field with the variable exists, false otherwise.
     * @since 4.2
     */
    public boolean hasField(String variable) {
        return dataForm.hasField(variable);
    }

    /**
     * Returns the instructions that explain how to fill out the form and what the form is about.
     * 
     * @return instructions that explain how to fill out the form.
     */
    public String getInstructions() {
        StringBuilder sb = new StringBuilder();
        // Join the list of instructions together separated by newlines
        for (Iterator<String> it = dataForm.getInstructions().iterator(); it.hasNext();) {
            sb.append(it.next());
            // If this is not the last instruction then append a newline
            if (it.hasNext()) {
                sb.append('\n');
            }
        }
        return sb.toString();
    }


    /**
     * Returns the description of the data. It is similar to the title on a web page or an X 
     * window.  You can put a title on either a form to fill out, or a set of data results.
     * 
     * @return description of the data.
     */
    public String getTitle() {
        return dataForm.getTitle();
    }


    /**
     * Returns the meaning of the data within the context. The data could be part of a form
     * to fill out, a form submission or data results.
     * 
     * @return the form's type.
     */
    public DataForm.Type getType() {
        return dataForm.getType(); 
    }


    /**
     * Sets instructions that explain how to fill out the form and what the form is about.
     * 
     * @param instructions instructions that explain how to fill out the form.
     */
    public void setInstructions(String instructions) {
        // Split the instructions into multiple instructions for each existent newline
        ArrayList<String> instructionsList = new ArrayList<>();
        StringTokenizer st = new StringTokenizer(instructions, "\n");
        while (st.hasMoreTokens()) {
            instructionsList.add(st.nextToken());
        }
        // Set the new list of instructions
        dataForm.setInstructions(instructionsList);

    }


    /**
     * Sets the description of the data. It is similar to the title on a web page or an X window.
     * You can put a title on either a form to fill out, or a set of data results.
     * 
     * @param title description of the data.
     */
    public void setTitle(String title) {
        dataForm.setTitle(title);
    }

    /**
     * Returns a DataForm that serves to send this Form to the server. If the form is of type 
     * submit, it may contain fields with no value. These fields will be removed since they only 
     * exist to assist the user while editing/completing the form in a UI. 
     * 
     * @return the wrapped DataForm.
     */
    public DataForm getDataFormToSend() {
        if (isSubmitType()) {
            // Create a new DataForm that contains only the answered fields 
            DataForm dataFormToSend = new DataForm(getType());
            for (FormField field : getFields()) {
                if (!field.getValues().isEmpty()) {
                    dataFormToSend.addField(field);
                }
            }
            return dataFormToSend;
        }
        return dataForm;
    }

    /**
     * Returns true if the form is a form to fill out.
     * 
     * @return if the form is a form to fill out.
     */
    private boolean isFormType() {
        return DataForm.Type.form == dataForm.getType();
    }

    /**
     * Returns true if the form is a form to submit.
     * 
     * @return if the form is a form to submit.
     */
    private boolean isSubmitType() {
        return DataForm.Type.submit == dataForm.getType();
    }

    /**
     * Returns a new Form to submit the completed values. The new Form will include all the fields
     * of the original form except for the fields of type FIXED. Only the HIDDEN fields will 
     * include the same value of the original form. The other fields of the new form MUST be 
     * completed. If a field remains with no answer when sending the completed form, then it won't 
     * be included as part of the completed form.<p>
     * 
     * The reason why the fields with variables are included in the new form is to provide a model 
     * for binding with any UI. This means that the UIs will use the original form (of type 
     * "form") to learn how to render the form, but the UIs will bind the fields to the form of
     * type submit.
     * 
     * @return a Form to submit the completed values.
     */
    public Form createAnswerForm() {
        if (!isFormType()) {
            throw new IllegalStateException("Only forms of type \"form\" could be answered");
        }
        // Create a new Form
        Form form = new Form(DataForm.Type.submit);
        for (FormField field : getFields()) {
            // Add to the new form any type of field that includes a variable.
            // Note: The fields of type FIXED are the only ones that don't specify a variable
            if (field.getVariable() != null) {
                FormField newField = new FormField(field.getVariable());
                newField.setType(field.getType());
                form.addField(newField);
                // Set the answer ONLY to the hidden fields 
                if (field.getType() == FormField.Type.hidden) {
                    // Since a hidden field could have many values we need to collect them 
                    // in a list
                    List<String> values = new ArrayList<>();
                    values.addAll(field.getValues());
                    form.setAnswer(field.getVariable(), values);
                }
            }
        }
        return form;
    }

}