/*jshint strict: false */

////////////////////////////////////////////////////////////////////////////////
/// @brief AQL user functions management
///
/// @file
///
/// DISCLAIMER
///
/// Copyright 2012 triagens GmbH, Cologne, Germany
///
/// 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.
///
/// Copyright holder is triAGENS GmbH, Cologne, Germany
///
/// @author Jan Steemann
/// @author Copyright 2012, triAGENS GmbH, Cologne, Germany
////////////////////////////////////////////////////////////////////////////////

var internal = require("internal");
var arangodb = require("@arangodb");

var db = arangodb.db;
var ArangoError = arangodb.ArangoError;

// -----------------------------------------------------------------------------
// --SECTION--                               module "@arangodb/aql/functions"
// -----------------------------------------------------------------------------

// -----------------------------------------------------------------------------
// --SECTION--                                                 private functions
// -----------------------------------------------------------------------------

////////////////////////////////////////////////////////////////////////////////
/// @brief return the _aqlfunctions collection
////////////////////////////////////////////////////////////////////////////////

var getStorage = function () {
  'use strict';

  var functions = db._collection("_aqlfunctions");

  if (functions === null) {
    var err = new ArangoError();
    err.errorNum = arangodb.errors.ERROR_ARANGO_COLLECTION_NOT_FOUND.code;
    err.errorMessage = "collection '_aqlfunctions' not found";

    throw err;
  }

  return functions;
};

////////////////////////////////////////////////////////////////////////////////
/// @brief apply a prefix filter on the functions
////////////////////////////////////////////////////////////////////////////////

var getFiltered = function (group) {
  'use strict';

  var result = [ ];

  if (group !== null && group !== undefined && group.length > 0) {
    var prefix = group.toUpperCase();

    if (group.length > 1 && group.substr(group.length - 2, 2) !== '::') {
      prefix += '::';
    }

    getStorage().toArray().forEach(function (f) {
      if (f.name.toUpperCase().substr(0, prefix.length) === prefix) {
        result.push(f);
      }
    });
  }
  else {
    result = getStorage().toArray();
  }

  return result;
};

////////////////////////////////////////////////////////////////////////////////
/// @brief validate a function name
////////////////////////////////////////////////////////////////////////////////

var validateName = function (name) {
  'use strict';

  if (typeof name !== 'string' ||
      ! name.match(/^[a-zA-Z0-9_]+(::[a-zA-Z0-9_]+)+$/) ||
      name.substr(0, 1) === "_") {
    var err = new ArangoError();
    err.errorNum = arangodb.errors.ERROR_QUERY_FUNCTION_INVALID_NAME.code;
    err.errorMessage = arangodb.errors.ERROR_QUERY_FUNCTION_INVALID_NAME.message;

    throw err;
  }
};

////////////////////////////////////////////////////////////////////////////////
/// @brief validate user function code
////////////////////////////////////////////////////////////////////////////////

var stringifyFunction = function (code, name) {
  'use strict';

  if (typeof code === 'function') {
    code = String(code) + "\n";
  }

  if (typeof code === 'string') {
    code = "(" + code + "\n)";

    if (! internal.parse) {
      // no parsing possible. assume always valid
      return code;
    }

    try {
      if (internal.parse(code, name)) {
        // parsing successful
        return code;
      }
    }
    catch (e) {
    }
  }

  // fall-through intentional

  var err = new ArangoError();
  err.errorNum = arangodb.errors.ERROR_QUERY_FUNCTION_INVALID_CODE.code;
  err.errorMessage = arangodb.errors.ERROR_QUERY_FUNCTION_INVALID_CODE.message;

  throw err;
};

// -----------------------------------------------------------------------------
// --SECTION--                                                  public functions
// -----------------------------------------------------------------------------

////////////////////////////////////////////////////////////////////////////////
/// @startDocuBlock aqlFunctionsUnregister
/// @brief delete an existing AQL user function
/// `aqlfunctions.unregister(name)`
///
/// Unregisters an existing AQL user function, identified by the fully qualified
/// function name.
///
/// Trying to unregister a function that does not exist will result in an
/// exception.
///
/// @EXAMPLES
///
/// ```js
///   require("@arangodb/aql/functions").unregister("myfunctions::temperature::celsiustofahrenheit");
/// ```
/// @endDocuBlock
////////////////////////////////////////////////////////////////////////////////

var unregisterFunction = function (name) {
  'use strict';

  var func = null;

  validateName(name);

  try {
    func = getStorage().document(name.toUpperCase());
  }
  catch (err1) {
  }

  if (func === null) {
    var err = new ArangoError();
    err.errorNum = arangodb.errors.ERROR_QUERY_FUNCTION_NOT_FOUND.code;
    err.errorMessage = internal.sprintf(arangodb.errors.ERROR_QUERY_FUNCTION_NOT_FOUND.message, name);

    throw err;
  }

  getStorage().remove(func._id);
  internal.reloadAqlFunctions();

  return true;
};

////////////////////////////////////////////////////////////////////////////////
/// @startDocuBlock aqlFunctionsUnregisterGroup
/// @brief delete a group of AQL user functions
/// `aqlfunctions.unregisterGroup(prefix)`
///
/// Unregisters a group of AQL user function, identified by a common function
/// group prefix.
///
/// This will return the number of functions unregistered.
///
/// @EXAMPLES
///
/// ```js
///   require("@arangodb/aql/functions").unregisterGroup("myfunctions::temperature");
///
///   require("@arangodb/aql/functions").unregisterGroup("myfunctions");
/// ```
/// @endDocuBlock
////////////////////////////////////////////////////////////////////////////////

var unregisterFunctionsGroup = function (group) {
  'use strict';

  if (group.length === 0) {
    var err = new ArangoError();
    err.errorNum = arangodb.errors.ERROR_BAD_PARAMETER.code;
    err.errorMessage = arangodb.errors.ERROR_BAD_PARAMETER.message;

    throw err;
  }

  var deleted = 0;

  getFiltered(group).forEach(function (f) {
    getStorage().remove(f._id);
    deleted++;
  });

  if (deleted > 0) {
    internal.reloadAqlFunctions();
  }

  return deleted;
};

////////////////////////////////////////////////////////////////////////////////
/// @startDocuBlock aqlFunctionsRegister
/// @brief register an AQL user function
/// `aqlfunctions.register(name, code, isDeterministic)`
///
/// Registers an AQL user function, identified by a fully qualified function
/// name. The function code in *code* must be specified as a JavaScript
/// function or a string representation of a JavaScript function.
/// If the function code in *code* is passed as a string, it is required that
/// the string evaluates to a JavaScript function definition.
///
/// If a function identified by *name* already exists, the previous function
/// definition will be updated. Please also make sure that the function code
/// does not violate the [Conventions](../AqlExtending/Conventions.md) for AQL 
/// functions.
///
/// The *isDeterministic* attribute can be used to specify whether the
/// function results are fully deterministic (i.e. depend solely on the input
/// and are the same for repeated calls with the same input values). It is not
/// used at the moment but may be used for optimizations later.
///
/// The registered function is stored in the selected database's system 
/// collection *_aqlfunctions*.
///
/// The function returns *true* when it updates/replaces an existing AQL 
/// function of the same name, and *false* otherwise. It will throw an exception
/// when it detects syntactially invalid function code.
///
/// @EXAMPLES
///
/// ```js
///   require("@arangodb/aql/functions").register("myfunctions::temperature::celsiustofahrenheit",
///   function (celsius) {
///     return celsius * 1.8 + 32;
///   });
/// ```
/// @endDocuBlock
////////////////////////////////////////////////////////////////////////////////

var registerFunction = function (name, code, isDeterministic) {
  // validate input
  validateName(name);

  code = stringifyFunction(code, name);

  var testCode = "(function() { var callback = " + code + "; return callback; })()";
  var err;

  try {
    if (internal && internal.hasOwnProperty("executeScript")) {
      var evalResult = internal.executeScript(testCode, undefined, "(user function " + name + ")");
      if (typeof evalResult !== "function") {
        err = new ArangoError();
        err.errorNum = arangodb.errors.ERROR_QUERY_FUNCTION_INVALID_CODE.code;
        err.errorMessage = arangodb.errors.ERROR_QUERY_FUNCTION_INVALID_CODE.message + 
                           ": code must be contained in function";
        throw err;
      }
    }
  }
  catch (err1) {
    err = new ArangoError();
    err.errorNum = arangodb.errors.ERROR_QUERY_FUNCTION_INVALID_CODE.code;
    err.errorMessage = arangodb.errors.ERROR_QUERY_FUNCTION_INVALID_CODE.message;
    throw err;
  }

  var result = db._executeTransaction({
    collections: {
      write: getStorage().name()
    },
    action: function (params) {
      var exists = false;
      var collection = require("internal").db._collection(params.collection);
      var name = params.name;

      try {
        var doc = collection.document(name.toUpperCase());
        if (doc !== null) {
          collection.remove(doc._key);
          exists = true;
        }
      }
      catch (err2) {
      }

      var data = {
        _key: name.toUpperCase(),
        name: name,
        code: params.code,
        isDeterministic: params.isDeterministic || false
      };

      collection.save(data);
      return exists;
    },
    params: {
      name: name,
      code: code,
      isDeterministic: isDeterministic,
      collection: getStorage().name()
    }
  });

  internal.reloadAqlFunctions();

  return result;
};

////////////////////////////////////////////////////////////////////////////////
/// @startDocuBlock aqlFunctionsToArray
/// @brief list all AQL user functions
/// `aqlfunctions.toArray()`
///
/// Returns all previously registered AQL user functions, with their fully
/// qualified names and function code.
///
/// The result may optionally be restricted to a specified group of functions
/// by specifying a group prefix:
///
/// `aqlfunctions.toArray(prefix)`
///
/// @EXAMPLES
///
/// To list all available user functions:
///
/// ```js
///   require("@arangodb/aql/functions").toArray();
/// ```
///
/// To list all available user functions in the *myfunctions* namespace:
///
/// ```js
///   require("@arangodb/aql/functions").toArray("myfunctions");
/// ```
///
/// To list all available user functions in the *myfunctions::temperature* namespace:
///
/// ```js
///   require("@arangodb/aql/functions").toArray("myfunctions::temperature");
/// ```
/// @endDocuBlock
////////////////////////////////////////////////////////////////////////////////

var toArrayFunctions = function (group) {
  'use strict';

  var result = [ ];

  getFiltered(group).forEach(function (f) {
    result.push({ name: f.name, code: f.code.substr(1, f.code.length - 2).trim() });
  });

  return result;
};

// -----------------------------------------------------------------------------
// --SECTION--                                                    module exports
// -----------------------------------------------------------------------------

exports.unregister      = unregisterFunction;
exports.unregisterGroup = unregisterFunctionsGroup;
exports.register        = registerFunction;
exports.toArray         = toArrayFunctions;

// -----------------------------------------------------------------------------
// --SECTION--                                                       END-OF-FILE
// -----------------------------------------------------------------------------

// Local Variables:
// mode: outline-minor
// outline-regexp: "/// @brief\\|/// @addtogroup\\|// --SECTION--\\|/// @page\\|/// @}\\|/\\*jslint"
// End: