/*
    * 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 org.apache.commons.jexl3;
  
  import java.math.MathContext;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Map;
  
  import org.apache.commons.jexl3.internal.Engine;
  
  /**
   * Flags and properties that can alter the evaluation behavior.
   * The flags, briefly explained, are the following:
   * <ul>
   * <li>silent: whether errors throw exception</li>
   * <li>safe: whether navigation through null is <em>not</em>an error</li>
   * <li>cancellable: whether thread interruption is an error</li>
   * <li>lexical: whether redefining local variables is an error</li>
   * <li>lexicalShade: whether local variables shade global ones even outside their scope</li>
   * <li>strict: whether unknown or unsolvable identifiers are errors</li>
   * <li>strictArithmetic: whether null as operand is an error</li>
   * <li>sharedInstance: whether these options can be modified at runtime during execution (expert)</li>
   * </ul>
   * The sensible default is cancellable, strict and strictArithmetic.
   * <p>This interface replaces the now deprecated JexlEngine.Options.
   * @since 3.2
   */
  public final class JexlOptions {
      /** The shared instance bit. */
      private static final int SHARED = 7;
      /** The local shade bit. */
      private static final int SHADE = 6;
      /** The antish var bit. */
      private static final int ANTISH = 5;
      /** The lexical scope bit. */
      private static final int LEXICAL = 4;
      /** The safe bit. */
      private static final int SAFE = 3;
      /** The silent bit. */
      private static final int SILENT = 2;
      /** The strict bit. */
      private static final int STRICT = 1;
      /** The cancellable bit. */
      private static final int CANCELLABLE = 0;
      /** The flag names ordered. */
      private static final String[] NAMES = {
          "cancellable", "strict", "silent", "safe", "lexical", "antish", "lexicalShade", "sharedInstance"
      };
      /** Default mask .*/
      private static int DEFAULT = 1 /*<< CANCELLABLE*/ | 1 << STRICT | 1 << ANTISH | 1 << SAFE;
      /** The arithmetic math context. */
      private MathContext mathContext = null;
      /** The arithmetic math scale. */
      private int mathScale = Integer.MIN_VALUE;
      /** The arithmetic strict math flag. */
      private boolean strictArithmetic = true;
      /** The default flags, all but safe. */
      private int flags = DEFAULT;
      /** The namespaces .*/
      private Map<String, Object> namespaces = Collections.emptyMap();
      /** The imports. */
      private Collection<String> imports = Collections.emptySet();
  
      /**
       * Sets the value of a flag in a mask.
       * @param ordinal the flag ordinal
       * @param mask the flags mask
       * @param value true or false
       * @return the new flags mask value
       */
      private static int set(final int ordinal, final int mask, final boolean value) {
          return value? mask | (1 << ordinal) : mask & ~(1 << ordinal);
      }
  
      /**
       * Checks the value of a flag in the mask.
       * @param ordinal the flag ordinal
       * @param mask the flags mask
       * @return the mask value with this flag or-ed in
       */
      private static boolean isSet(final int ordinal, final int mask) {
          return (mask & 1 << ordinal) != 0;
      }
 
     /**
      * Default ctor.
      */
     public JexlOptions() {
         // all inits in members declarations
     }
 
     /**
      * Sets the default (static, shared) option flags.
      * <p>
      * Whenever possible, we recommend using JexlBuilder methods to unambiguously instantiate a JEXL
      * engine; this method should only be used for testing / validation.
      * <p>A '+flag' or 'flag' will set the option named 'flag' as true, '-flag' set as false.
      * The possible flag names are:
      * cancellable, strict, silent, safe, lexical, antish, lexicalShade
      * <p>Calling JexlBuilder.setDefaultOptions("+safe") once before JEXL engine creation
      * may ease validating JEXL3.2 in your environment.
      * @param flags the flags to set
      */
     public static void setDefaultFlags(final String...flags) {
         DEFAULT = parseFlags(DEFAULT, flags);
     }
 
     /**
      * Parses flags by name.
      * <p>A '+flag' or 'flag' will set flag as true, '-flag' set as false.
      * The possible flag names are:
      * cancellable, strict, silent, safe, lexical, antish, lexicalShade
      * @param initial the initial mask state
      * @param flags the flags to set
      * @return the flag mask updated
      */
     public static int parseFlags(final int initial, final String... flags) {
         int mask = initial;
         for (final String flag : flags) {
             boolean b = true;
             final String name;
             if (flag.charAt(0) == '+') {
                 name = flag.substring(1);
             } else if (flag.charAt(0) == '-') {
                 name = flag.substring(1);
                 b = false;
             } else {
                 name = flag;
             }
             for (int f = 0; f < NAMES.length; ++f) {
                 if (NAMES[f].equals(name)) {
                     if (b) {
                         mask |= (1 << f);
                     } else {
                         mask &= ~(1 << f);
                     }
                     break;
                 }
             }
         }
         return mask;
     }
 
     /**
      * Sets this option flags using the +/- syntax.
      * @param opts the option flags
      */
     public void setFlags(final String... opts) {
         flags = parseFlags(flags, opts);
     }
 
     /**
      * The MathContext instance used for +,-,/,*,% operations on big decimals.
      * @return the math context
      */
     public MathContext getMathContext() {
         return mathContext;
     }
 
     /**
      * The BigDecimal scale used for comparison and coercion operations.
      * @return the scale
      */
     public int getMathScale() {
         return mathScale;
     }
 
     /**
      * Checks whether evaluation will attempt resolving antish variable names.
      * @return true if antish variables are solved, false otherwise
      */
     public boolean isAntish() {
         return isSet(ANTISH, flags);
     }
 
     /**
      * Checks whether evaluation will throw JexlException.Cancel (true) or
      * return null (false) if interrupted.
      * @return true when cancellable, false otherwise
      */
     public boolean isCancellable() {
         return isSet(CANCELLABLE, flags);
     }
 
     /**
      * Checks whether runtime variable scope is lexical.
      * <p>If true, lexical scope applies to local variables and parameters.
      * Redefining a variable in the same lexical unit will generate errors.
      * @return true if scope is lexical, false otherwise
      */
     public boolean isLexical() {
         return isSet(LEXICAL, flags);
     }
 
     /**
      * Checks whether local variables shade global ones.
      * <p>After a symbol is defined as local, dereferencing it outside its
      * scope will trigger an error instead of seeking a global variable of the
      * same name. To further reduce potential naming ambiguity errors,
      * global variables (ie non-local) must be declared to be assigned (@link JexlContext#has(String) )
      * when this flag is on; attempting to set an undeclared global variables will
      * raise an error.
      * @return true if lexical shading is applied, false otherwise
      */
     public boolean isLexicalShade() {
         return isSet(SHADE, flags);
     }
 
     /**
      * Checks whether the engine considers null in navigation expression as
      * errors during evaluation..
      * @return true if safe, false otherwise
      */
     public boolean isSafe() {
         return isSet(SAFE, flags);
     }
 
     /**
      * Checks whether the engine will throw a {@link JexlException} when an
      * error is encountered during evaluation.
      * @return true if silent, false otherwise
      */
     public boolean isSilent() {
         return isSet(SILENT, flags);
     }
 
     /**
      * Checks whether the engine considers unknown variables, methods and
      * constructors as errors during evaluation.
      * @return true if strict, false otherwise
      */
     public boolean isStrict() {
         return isSet(STRICT, flags);
     }
 
     /**
      * Checks whether the arithmetic triggers errors during evaluation when null
      * is used as an operand.
      * @return true if strict, false otherwise
      */
     public boolean isStrictArithmetic() {
         return strictArithmetic;
     }
 
     /**
      * Sets whether the engine will attempt solving antish variable names from
      * context.
      * @param flag true if antish variables are solved, false otherwise
      */
     public void setAntish(final boolean flag) {
         flags = set(ANTISH, flags, flag);
     }
 
     /**
      * Sets whether the engine will throw JexlException.Cancel (true) or return
      * null (false) when interrupted during evaluation.
      * @param flag true when cancellable, false otherwise
      */
     public void setCancellable(final boolean flag) {
         flags = set(CANCELLABLE, flags, flag);
     }
 
     /**
      * Sets whether the engine uses a strict block lexical scope during
      * evaluation.
      * @param flag true if lexical scope is used, false otherwise
      */
     public void setLexical(final boolean flag) {
         flags = set(LEXICAL, flags, flag);
     }
 
     /**
      * Sets whether the engine strictly shades global variables.
      * Local symbols shade globals after definition and creating global
      * variables is prohibited during evaluation.
      * If setting to lexical shade, lexical scope is also set.
      * @param flag true if creation is allowed, false otherwise
      */
     public void setLexicalShade(final boolean flag) {
         flags = set(SHADE, flags, flag);
         if (flag) {
             flags = set(LEXICAL, flags, true);
         }
     }
 
     /**
      * Sets the arithmetic math context.
      * @param mcontext the context
      */
     public void setMathContext(final MathContext mcontext) {
         this.mathContext = mcontext;
     }
 
     /**
      * Sets the arithmetic math scale.
      * @param mscale the scale
      */
     public void setMathScale(final int mscale) {
         this.mathScale = mscale;
     }
 
     /**
      * Sets whether the engine considers null in navigation expression as null or as errors
      * during evaluation.
      * <p>If safe, encountering null during a navigation expression - dereferencing a method or a field through a null
      * object or property - will <em>not</em> be considered an error but evaluated as <em>null</em>. It is recommended
      * to use <em>setSafe(false)</em> as an explicit default.</p>
      * @param flag true if safe, false otherwise
      */
     public void setSafe(final boolean flag) {
         flags = set(SAFE, flags, flag);
     }
 
     /**
      * Sets whether the engine will throw a {@link JexlException} when an error
      * is encountered during evaluation.
      * @param flag true if silent, false otherwise
      */
     public void setSilent(final boolean flag) {
         flags = set(SILENT, flags, flag);
     }
 
     /**
      * Sets whether the engine considers unknown variables, methods and
      * constructors as errors during evaluation.
      * @param flag true if strict, false otherwise
      */
     public void setStrict(final boolean flag) {
         flags = set(STRICT, flags, flag);
     }
 
     /**
      * Sets the strict arithmetic flag.
      * @param stricta true or false
      */
     public void setStrictArithmetic(final boolean stricta) {
         this.strictArithmetic = stricta;
     }
 
     /**
      * Whether these options are immutable at runtime.
      * <p>Expert mode; allows instance handled through context to be shared
      * instead of copied.
      * @param flag true if shared, false if not
      */
     public void setSharedInstance(final boolean flag) {
         flags = set(SHARED, flags, flag);
     }
 
     /**
      * @return false if a copy of these options is used during execution,
      * true if those can potentially be modified
      */
     public boolean isSharedInstance() {
         return isSet(SHARED, flags);
     }
 
     /**
      * Set options from engine.
      * @param jexl the engine
      * @return this instance
      */
     public JexlOptions set(final JexlEngine jexl) {
         if (jexl instanceof Engine) {
             ((Engine) jexl).optionsSet(this);
         }
         return this;
     }
 
     /**
      * Set options from options.
      * @param src the options
      * @return this instance
      */
     public JexlOptions set(final JexlOptions src) {
         mathContext = src.mathContext;
         mathScale = src.mathScale;
         strictArithmetic = src.strictArithmetic;
         flags = src.flags;
         namespaces = src.namespaces;
         imports = src.imports;
         return this;
     }
 
     /**
      * Gets the optional map of namespaces.
      * @return the map of namespaces, may be empty, not null
      */
     public Map<String, Object> getNamespaces() {
         return namespaces;
     }
 
     /**
      * Sets the optional map of namespaces.
      * @param ns a namespaces map
      */
     public void setNamespaces(final Map<String, Object> ns) {
         this.namespaces = ns == null || ns.isEmpty()? Collections.emptyMap() : ns;
     }
 
     /**
      * Gets the optional set of imported packages.
      * @return the set of imports, may be empty, not null
      */
     public Collection<String> getImports() {
         return imports;
     }
 
     /**
      * Sets the optional set of imports.
      * @param imports the imported packages
      */
     public void setImports(final Collection<String> imports) {
         this.imports = imports == null || imports.isEmpty()? Collections.emptySet() : imports;
     }
 
     /**
      * Creates a copy of this instance.
      * @return a copy
      */
     public JexlOptions copy() {
         return new JexlOptions().set(this);
     }
 
     @Override public String toString() {
         final StringBuilder strb = new StringBuilder();
         for(int i = 0; i < NAMES.length; ++i) {
             if (i > 0) {
                 strb.append(' ');
             }
             strb.append((flags & (1 << i)) != 0? '+':'-');
             strb.append(NAMES[i]);
         }
         return strb.toString();
     }
 
 }