/*
    * 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
    *
    *      https://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.internal;
  
  import java.io.Reader;
  import java.io.Writer;
  import java.util.Collections;
  import java.util.List;
  import java.util.Map;
  import java.util.Objects;
  import java.util.Set;
  
  import org.apache.commons.jexl3.JexlContext;
  import org.apache.commons.jexl3.JexlEngine;
  import org.apache.commons.jexl3.JexlException;
  import org.apache.commons.jexl3.JexlInfo;
  import org.apache.commons.jexl3.JexlOptions;
  import org.apache.commons.jexl3.JxltEngine;
  import org.apache.commons.jexl3.internal.TemplateEngine.Block;
  import org.apache.commons.jexl3.internal.TemplateEngine.BlockType;
  import org.apache.commons.jexl3.internal.TemplateEngine.TemplateExpression;
  import org.apache.commons.jexl3.parser.ASTArguments;
  import org.apache.commons.jexl3.parser.ASTFunctionNode;
  import org.apache.commons.jexl3.parser.ASTIdentifier;
  import org.apache.commons.jexl3.parser.ASTJexlScript;
  import org.apache.commons.jexl3.parser.ASTNumberLiteral;
  import org.apache.commons.jexl3.parser.JexlNode;
  
  /**
   * A Template instance.
   */
  public final class TemplateScript implements JxltEngine.Template {
  
      /**
       * Collects the call-site surrounding a call to jexl:print(i).
       * <p>This allows parsing the blocks with the known symbols
       * in the frame visible to the parser.</p>
       *
       * @param node The visited node
       * @param callSites The map of printed expression number to node info
       */
      private static void collectPrintScope(final JexlNode node, final JexlNode.Info[] callSites) {
          final int nc = node.jjtGetNumChildren();
          if (node instanceof ASTFunctionNode && nc == 2) {
              // is child[0] jexl:print()?
              final ASTIdentifier nameNode = (ASTIdentifier) node.jjtGetChild(0);
              if ("print".equals(nameNode.getName()) && "jexl".equals(nameNode.getNamespace())) {
                  // is there one argument?
                  final ASTArguments argNode = (ASTArguments) node.jjtGetChild(1);
                  if (argNode.jjtGetNumChildren() == 1) {
                      // seek the expression number
                      final JexlNode arg0 = argNode.jjtGetChild(0);
                      if (arg0 instanceof ASTNumberLiteral) {
                          final int exprNumber = ((ASTNumberLiteral) arg0).getLiteral().intValue();
                          callSites[exprNumber] = new JexlNode.Info(nameNode);
                          return;
                      }
                  }
              }
          }
          for (int c = 0; c < nc; ++c) {
              collectPrintScope(node.jjtGetChild(c), callSites);
          }
      }
  
      /**
       * Gets the scope from a node info.
       *
       * @param info The node info
       * @param scope The outer scope
       * @return The scope
       */
      private static Scope scopeOf(final JexlNode.Info info, final Scope scope) {
          Scope found = null;
          JexlNode walk = info.getNode();
          while (walk != null) {
              if (walk instanceof ASTJexlScript) {
                  found = ((ASTJexlScript) walk).getScope();
                  break;
              }
              walk = walk.jjtGetParent();
          }
          return found != null ? found : scope;
      }
  
     /**
      * Creates the expression array from the list of blocks.
      *
      * @param scope The outer scope
      * @param blocks The list of blocks
      * @return The array of expressions
      */
     private TemplateExpression[] calleeScripts(final Scope scope, final Block[] blocks, final JexlNode.Info[] callSites) {
         final TemplateExpression[] expressions = new TemplateExpression[callSites.length];
         // jexl:print(...) expression counter
         int jpe = 0;
         // create the expressions using the intended scopes
         for (final Block block : blocks) {
             if (block.getType() == BlockType.VERBATIM) {
                 final JexlNode.Info ji = callSites[jpe];
                 // no node info means this verbatim is surrounded by comments markers;
                 // expr at this index is never called
                 final TemplateExpression te = ji != null
                     ? jxlt.parseExpression(ji, block.getBody(), scopeOf(ji, scope))
                     : jxlt.new ConstantExpression(block.getBody(), null);
                 expressions[jpe++] = te;
             }
         }
         return expressions;
     }
 
     /**
      * Creates the script calling the list of blocks.
      * <p>This is used to create a script from a list of blocks
      * that were parsed from a template.</p>
      *
      * @param blocks The list of blocks
      * @return The script source
      */
     private static String callerScript(final Block[] blocks) {
         final StringBuilder strb = new StringBuilder();
         int nuexpr = 0;
         int line = 1;
         for (final Block block : blocks) {
             final int bl = block.getLine();
             while (line < bl) {
                 strb.append("//\n");
                 line += 1;
             }
             if (block.getType() == BlockType.VERBATIM) {
                 strb.append("jexl:print(");
                 strb.append(nuexpr++);
                 strb.append(");\n");
                 line += 1;
             } else {
                 final String body = block.getBody();
                 strb.append(body);
                 // keep track of the line number
                 for (int c = 0; c < body.length(); ++c) {
                     if (body.charAt(c) == '\n') {
                         line += 1;
                     }
                 }
             }
         }
         return strb.toString();
     }
 
     /** The prefix marker. */
     private final String prefix;
 
     /** The array of source blocks. */
     private final Block[] source;
 
     /** The resulting script. */
     private final ASTJexlScript script;
 
     /** The TemplateEngine expressions called by the script. */
     private final TemplateExpression[] exprs;
 
     /** The engine. */
     private final TemplateEngine jxlt;
 
     /**
      * Creates a new template from an character input.
      *
      * @param engine The template engine
      * @param jexlInfo The source info
      * @param directive The prefix for lines of code; cannot be "$", "${", "#" or "#{"
                   since this would preclude being able to differentiate directives and jxlt expressions
      * @param reader    The input reader
      * @param parms     The parameter names
      * @throws NullPointerException     if either the directive prefix or input is null
      * @throws IllegalArgumentException if the directive prefix is invalid
      */
     public TemplateScript(final TemplateEngine engine,
                           final JexlInfo jexlInfo,
                           final String directive,
                           final Reader reader,
                           final String... parms) {
         Objects.requireNonNull(directive, "directive");
         final String engineImmediateCharString = Character.toString(engine.getImmediateChar());
         final String engineDeferredCharString = Character.toString(engine.getDeferredChar());
 
         if (engineImmediateCharString.equals(directive)
                 || engineDeferredCharString.equals(directive)
                 || (engineImmediateCharString + "{").equals(directive)
                 || (engineDeferredCharString + "{").equals(directive)) {
             throw new IllegalArgumentException(directive + ": is not a valid directive pattern");
         }
         Objects.requireNonNull(reader, "reader");
         this.jxlt = engine;
         this.prefix = directive;
         final Engine jexl = jxlt.getEngine();
         // create the caller script
         final Block[] blocks = jxlt.readTemplate(prefix, reader).toArray(new Block[0]);
         int verbatims = 0;
         for(final Block b : blocks) {
             if (BlockType.VERBATIM == b.getType()) {
                 verbatims += 1;
             }
         }
         final JexlEngine je = Engine.putThreadEngine(jexl);
         try {
             final String scriptSource = callerScript(blocks);
             // allow lambda defining params
             final JexlInfo info = jexlInfo == null ? jexl.createInfo() : jexlInfo;
             final Scope scope = parms == null ? null : new Scope(null, parms);
             final JexlInfo templateInfo = jexl.scriptFeatures.isIgnoreTemplatePrefix()
                 ? new TemplateInfo(info.at(1, 1), Collections.singleton(prefix))
                 : info.at(1, 1);
             final ASTJexlScript callerScript = jexl.jxltParse(templateInfo, false, scriptSource, scope).script();
             // seek the map of expression number to scope so we can parse Unified
             // expression blocks with the appropriate symbols
             final JexlNode.Info[] callSites = new JexlNode.Info[verbatims];
             collectPrintScope(callerScript.script(), callSites);
             // create the expressions from the blocks
             this.exprs = calleeScripts(scope, blocks, callSites);
             this.script = callerScript;
             this.source = blocks;
         } finally {
             Engine.putThreadEngine(je);
         }
     }
 
     /**
      * Private ctor used to expand deferred expressions during prepare.
      *
      * @param engine    The template engine
      * @param thePrefix The directive prefix
      * @param theSource The source
      * @param theScript The script
      * @param theExprs  The expressions
      */
     TemplateScript(final TemplateEngine engine,
                    final String thePrefix,
                    final Block[] theSource,
                    final ASTJexlScript theScript,
                    final TemplateExpression[] theExprs) {
         jxlt = engine;
         prefix = thePrefix;
         source = theSource;
         script = theScript;
         exprs = theExprs;
     }
 
     @Override
     public String asString() {
         final StringBuilder strb = new StringBuilder();
         int e = 0;
         for (final Block block : source) {
             if (block.getType() == BlockType.DIRECTIVE) {
                 strb.append(prefix);
                 strb.append(block.getBody());
             } else {
                 exprs[e++].asString(strb);
             }
         }
         return strb.toString();
     }
 
     @Override
     public void evaluate(final JexlContext context, final Writer writer) {
         evaluate(context, writer, (Object[]) null);
     }
 
     @Override
     public void evaluate(final JexlContext context, final Writer writer, final Object... args) {
         final Engine jexl = jxlt.getEngine();
         final JexlOptions options = jexl.evalOptions(script, context);
         final Frame frame = script.createFrame(args);
         final TemplateInterpreter.Arguments targs = new TemplateInterpreter
                 .Arguments(jexl)
                 .context(context)
                 .options(options)
                 .frame(frame)
                 .expressions(exprs)
                 .writer(writer);
         final Interpreter interpreter = jexl.createTemplateInterpreter(targs);
         interpreter.interpret(script);
     }
 
     /**
      * @return exprs
      */
     TemplateExpression[] getExpressions() {
         return exprs;
     }
 
     @Override
     public String[] getParameters() {
         return script.getParameters();
     }
 
     @Override
     public Map<String, Object> getPragmas() {
         return script.getPragmas();
     }
 
     /**
      * @return script
      */
     ASTJexlScript getScript() {
         return script;
     }
 
     @Override
     public Set<List<String>> getVariables() {
         final Engine.VarCollector collector = jxlt.getEngine().varCollector();
         for (final TemplateExpression expr : exprs) {
             expr.getVariables(collector);
         }
         return collector.collected();
     }
 
     @Override
     public TemplateScript prepare(final JexlContext context) {
         return prepare(context, (Object[]) null);
     }
 
     @Override
     public TemplateScript prepare(final JexlContext context, final Object... args) {
         final Engine jexl = jxlt.getEngine();
         final JexlOptions options = jexl.evalOptions(script, context);
         final Frame frame = script.createFrame(args);
         final TemplateInterpreter.Arguments targs = new TemplateInterpreter
                 .Arguments(jxlt.getEngine())
                 .context(context)
                 .options(options)
                 .frame(frame);
         final Interpreter interpreter = jexl.createTemplateInterpreter(targs);
         final TemplateExpression[] prepared = new TemplateExpression[exprs.length];
         for (int e = 0; e < exprs.length; ++e) {
             try {
                 prepared[e] = exprs[e].prepare(interpreter);
             } catch (final JexlException xjexl) {
                 final JexlException xuel = TemplateEngine.createException(xjexl.getInfo(), "prepare", exprs[e], xjexl);
                 if (jexl.isSilent()) {
                     if (jexl.logger.isWarnEnabled()) {
                         jexl.logger.warn(xuel.getMessage(), xuel.getCause());
                     }
                     return null;
                 }
                 throw xuel;
             }
         }
         return new TemplateScript(jxlt, prefix, source, script, prepared);
     }
 
     @Override
     public String toString() {
         final StringBuilder strb = new StringBuilder();
         for (final Block block : source) {
             block.toString(strb, prefix);
         }
         return strb.toString();
     }
 }