/*

  * Copyright 2012, Ryan J. McDonough

  *

  * 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 com.damnhandy.uri.template;

 import com.damnhandy.uri.template.impl.Modifier;

 import com.damnhandy.uri.template.impl.Operator;

 import com.damnhandy.uri.template.impl.VarSpec;

 import java.util.ArrayList;

 import java.util.List;

 import java.util.regex.Matcher;

 import java.util.regex.Pattern;

 /**

  * <p>

  * An Expression represents the text between '{' and '}', including the enclosing

  * braces, as defined in <a href="ietf.org/html/rfc6570#section-2">Section 2 of RFC6570</a>.

  * </p>

  * <pre>

  * http://www.example.com/foo{?query,number}

  * \___________/

  * ^

  * |

  * |

  * The expression

  * </pre>

  * <p>

  * This class models this representation and adds helper functions for replacement and reverse matching.

  * </p>

  *

  * @author <a href="ryan@damnhandy.com">Ryan J. McDonough</a>

  * @version $Revision: 1.1 $

  * @since 2.0

  */

 public class Expression extends UriTemplateComponent

 {

     /**

      * The serialVersionUID

      */

     private static final long serialVersionUID = -5305648325957481840L;

     /**

      * A regex quoted string that matches the expression for replacement in the

      * expansion process. For example:

      * <pre>

      *          \Q{?query,number}\E

      * </pre>

      */

     private String replacementPattern;

     /**

      * That {@link Operator} value that is associated with this Expression

      */

     private Operator op;

     /**

      * The character position where this expression occurs in the URI template

      */

     private final int location;

     /**

      * The the parsed {@link VarSpec} instances found in the expression.

      */

     private List<VarSpec> varSpecs;

     /**

      * The Patter that would be used to reverse match this expression

      */

     private Pattern matchPattern;

     /**

      * Creates a new {@link Builder} to create a simple expression according

      * to section <a href="http://tools.ietf.org/html/rfc6570#section-3.2.2">3.2.2</a>.

      * Calling:

      * <pre>

      * String exp = Expression.simple(var("var")).build().toString();

      * </pre>

      * <p>

      * Will return the following expression:

      * </p>

      * <pre>

      * {var}

      * </pre>

      *

      * @return

      */

     public static Builder simple(VarSpec... varSpec)

     {

         return Builder.create(Operator.NUL, varSpec);

     }

     /**

      * Creates a new {@link Builder} to create an expression that will use reserved expansion

      * according to section <a href="http://tools.ietf.org/html/rfc6570#section-3.2.3">3.2.3</a>.

      * Calling:

      * <pre>

      * String exp = Expression.reserved().var("var").build().toString();

      * </pre>

      * <p>

      * Will return the following expression:

      * </p>

      * <pre>

      * {+var}

      * </pre>

      *

      * @return

      */

     public static Builder reserved(VarSpec... varSpec)

     {

         return Builder.create(Operator.RESERVED, varSpec);

     }

     /**

      * Creates a new {@link Builder} to create an expression with a fragment operator

      * according to section <a href="http://tools.ietf.org/html/rfc6570#section-3.2.4">3.2.4</a>.

      * Calling:

      * <pre>

      * String exp = Expression.fragment().var("var").build().toString();

      * </pre>

      * <p>

      * Will return the following expression:

      * </p>

      * <pre>

      * {#var}

      * </pre>

      *

      * @return

      */

     public static Builder fragment(VarSpec... varSpec)

     {

         return Builder.create(Operator.FRAGMENT, varSpec);

     }

     /**

      * Creates a new {@link Builder} to create an expression using label expansion

      * according to section <a href="http://tools.ietf.org/html/rfc6570#section-3.2.5">3.2.5</a>.

      * Calling:

      * <pre>

      * String exp = Expression.label(var("var")).build().toString();

      * </pre>

      * <p>

      * Will return the following expression:

      * </p>

      * <pre>

      * {.var}

      * </pre>

      *

      * @return

      */

     public static Builder label(VarSpec... varSpec)

     {

         return Builder.create(Operator.NAME_LABEL, varSpec);

     }

     /**

      * Creates a new {@link Builder} to create an expression using path expansion

      * according to section <a href="http://tools.ietf.org/html/rfc6570#section-3.2.6">3.2.6</a>.

      * Calling:

      * <pre>

      * String exp = Expression.path().var("var").build().toString();

      * </pre>

      * <p>

      * Will return the following expression:

      * </p>

      * <pre>

      * {/var}

      * </pre>

      *

      * @return

      */

     public static Builder path(VarSpec... varSpec)

     {

         return Builder.create(Operator.PATH, varSpec);

     }

     /**

      * Creates a new {@link Builder} to create an expression using path-style parameter

      * (a.k.a. matrix parameter) expansion according to

      * section <a href="http://tools.ietf.org/html/rfc6570#section-3.2.7">3.2.7</a>.

      * Calling:

      * <pre>

      * String exp = Expression.matrix().var("var").build().toString();

      * </pre>

      * <p>

      * Will return the following expression:

      * </p>

      * <pre>

      * {;var}

      * </pre>

      *

      * @return

      */

     public static Builder matrix(VarSpec... varSpec)

     {

         return Builder.create(Operator.MATRIX, varSpec);

     }

     /**

      * Creates a new {@link Builder} to create an expression using form-style query string expansion

      * according to section <a href="http://tools.ietf.org/html/rfc6570#section-3.2.8">3.2.8</a>.

      * Calling:

      * <pre>

      * String exp = Expression.query().var("var").build().toString();

      * </pre>

      * <p>

      * Will return the following expression:

      * </p>

      * <pre>

      * {?var}

      * </pre>

      *

      * @return

      */

     public static Builder query(VarSpec... varSpec)

     {

         return Builder.create(Operator.QUERY, varSpec);

     }

     /**

      * Creates a new {@link Builder} to create an expression using form-style query continuation expansion

      * according to section <a href="http://tools.ietf.org/html/rfc6570#section-3.2.9">3.2.9</a>.

      * Calling:

      * <pre>

      * String exp = Expression.continuation().var("var").build().toString();

      * </pre>

      * <p>

      * Will return the following expression:

      * </p>

      * <pre>

      * {&var}

      * </pre>

      *

      * @return

      */

     public static Builder continuation(VarSpec... varSpec)

     {

         return Builder.create(Operator.CONTINUATION, varSpec);

     }

     /**

      * Create a new Expression.

      *

      * @param rawExpression

      * @param startPosition

      * @throws MalformedUriTemplateException

      */

     public Expression(final String rawExpression, final int startPosition) throws MalformedUriTemplateException

     {

         super(startPosition);

         this.location = startPosition;

         this.parseRawExpression(rawExpression);

     }

     /**

      * Create a new Expression

      *

      * @param op

      * @param varSpecs

      * @throws MalformedUriTemplateException

      */

     public Expression(final Operator op, final List<VarSpec> varSpecs)

     {

         super(0);

         this.op = op;

         this.varSpecs = varSpecs;

         this.replacementPattern = Pattern.quote(toString());

         this.location = 0;

     }

     /**

      * @param rawExpression

      * @throws MalformedUriTemplateException

      */

     private void parseRawExpression(String rawExpression) throws MalformedUriTemplateException

     {

         final String expressionReplacement = Pattern.quote(rawExpression);

         String token = rawExpression.substring(1, rawExpression.length() - 1);

         // Check for URI operators

         Operator operator = Operator.NUL;

         String firstChar = token.substring(0, 1);

         if (UriTemplate.containsOperator(firstChar))

         {

             try

             {

                 operator = Operator.fromOpCode(firstChar);

             }

             catch (IllegalArgumentException e)

             {

                 throw new MalformedUriTemplateException("Invalid operator", this.location, e);

             }

             token = token.substring(1, token.length());

         }

         String[] varspecStrings = token.split(",");

         List<VarSpec> varspecs = new ArrayList<VarSpec>();

         for (String varname : varspecStrings)

         {

             int subStrPos = varname.indexOf(Modifier.PREFIX.getValue());

          /*

           * Prefix variable

           */

             if (subStrPos > 0)

             {

                 String[] pair = varname.split(Modifier.PREFIX.getValue());

                 try

                 {

                     Integer pos = Integer.valueOf(varname.substring(subStrPos + 1));

                     varspecs.add(new VarSpec(pair[0], Modifier.PREFIX, pos));

                 }

                 catch (NumberFormatException e)

                 {

                     throw new MalformedUriTemplateException("The prefix value for " + pair[0] + " was not a number", this.location, e);

                 }

             }

          /*

           * Variable will be exploded

           */

             else if (varname.lastIndexOf(Modifier.EXPLODE.getValue()) > 0)

             {

                 varspecs.add(new VarSpec(varname, Modifier.EXPLODE));

             }

          /*

           * Standard Value

           */

             else

             {

                 varspecs.add(new VarSpec(varname, Modifier.NONE));

             }

         }

         this.replacementPattern = expressionReplacement;

         this.op = operator;

         this.varSpecs = varspecs;

     }

     private Pattern buildMatchingPattern()

     {

         StringBuilder b = new StringBuilder();

         for (VarSpec v : getVarSpecs())

         {

             b.append("(?<").append(v.getVariableName()).append(">[^\\/]+)");

         }

         return Pattern.compile(b.toString());

     }

     /**

      * Returns a string that contains a regular expression that matches the

      * URI template expression.

      *

      * @return the match pattern

      */

     @Override

     public Pattern getMatchPattern()

     {

         if (this.matchPattern == null)

         {

             this.matchPattern = buildMatchingPattern();

         }

         return this.matchPattern;

     }

     /**

      * Get the replacementToken.

      *

      * @return the replacementToken.

      */

     public String getReplacementPattern()

     {

         return replacementPattern;

     }

     /**

      * Get the {@link Operator} value for this expression.

      *

      * @return the operator value.

      */

     public Operator getOperator()

     {

         return op;

     }

     /**

      * Get the varSpecs.

      *

      * @return the varSpecs.

      */

     public List<VarSpec> getVarSpecs()

     {

         return varSpecs;

     }

     /**

      * Returns the string representation of the expression.

      *

      * @see Object#toString()

      */

     public String toString()

     {

         StringBuilder b = new StringBuilder();

         b.append("{").append(this.getOperator().getOperator());

         for (int i = 0; i < varSpecs.size(); i++)

         {

             VarSpec v = varSpecs.get(i);

             b.append(v.getValue());

             // Double check that the value doesn't already contain the modifier

             int r = v.getValue().lastIndexOf(v.getModifier().getValue());

             if(v.getModifier() != null && v.getValue().lastIndexOf(v.getModifier().getValue()) == -1)

             {

                 b.append(v.getModifier().getValue());

             }

             if (v.getModifier() == Modifier.PREFIX)

             {

                 b.append(v.getPosition());

             }

             if (i != (varSpecs.size() - 1))

             {

                 b.append(",");

             }

         }

         return b.append("}").toString();

     }

     /**

      * Returns the value of this component

      *

      * @return the string value of this component.

      */

     @Override

     public String getValue()

     {

         return toString();

     }

     @Override

     public int hashCode()

     {

         final int prime = 31;

         int result = 1;

         result = prime * result + ((op == null) ? 0 : op.hashCode());

         result = prime * result + ((varSpecs == null) ? 0 : varSpecs.hashCode());

         return result;

     }

     @Override

     public boolean equals(Object obj)

     {

         if (this == obj)

         {

             return true;

         }

         if (obj == null)

         {

             return false;

         }

         if (getClass() != obj.getClass())

         {

             return false;

         }

         Expression other = (Expression) obj;

         if (op != other.op)

         {

             return false;

         }

         if (varSpecs == null)

         {

             if (other.varSpecs != null)

             {

                 return false;

             }

         }

         else if (!varSpecs.equals(other.varSpecs))

         {

             return false;

         }

         return true;

     }

     /**

      * Builder class for creating an {@link Expression}.

      *

      * @author <a href="ryan@damnhandy.com">Ryan J. McDonough</a>

      * @version $Revision: 1.1 $

      */

     public static class Builder

     {

         /**

          *

          */

         private Operator operator;

         /**

          *

          */

         private List<VarSpec> varSpecs;

         /**

          * Create a new ExpressionBuilder.

          *

          * @param operator

          */

         private Builder(Operator operator, VarSpec... varSpec)

         {

             this.operator = operator;

             this.varSpecs = new ArrayList<VarSpec>();

             for (VarSpec v : varSpec)

             {

                 varSpecs.add(v);

             }

         }

         /**

          * @param operator

          * @return the builder

          */

         static Builder create(Operator operator, VarSpec... varSpec)

         {

             return new Builder(operator, varSpec);

         }

         public Expression build()

         {

             return new Expression(operator, varSpecs);

         }

     }

 }