/*!
 * Module Dependencies.
 */
var registry = require('../registry');
var assert = require('assert');
var SharedClass = require('strong-remoting').SharedClass;
var extend = require('util')._extend;
var stringUtils = require('underscore.string');

/**
 * The base class for **all models**. 
 *
 * **Inheriting from `Model`**
 *
 * ```js
 * var properties = {...};
 * var options = {...};
 * var MyModel = loopback.Model.extend('MyModel', properties, options);
 * ```
 * 
 * **Options**
 *
 *  - `trackChanges` - If true, changes to the model will be tracked. **Required
 * for replication.**
 *
 * **Events**
 *
 * #### Event: `changed`
 * 
 * Emitted after a model has been successfully created, saved, or updated.
 *
 * ```js
 * MyModel.on('changed', function(inst) {
 *   console.log('model with id %s has been changed', inst.id);
 *   // => model with id 1 has been changed
 * });
 * ```
 * 
 * #### Event: `deleted`
 * 
 * Emitted after an individual model has been deleted.
 *
 * ```js
 * MyModel.on('deleted', function(inst) {
 *   console.log('model with id %s has been deleted', inst.id);
 *   // => model with id 1 has been deleted
 * });
 * ```
 *
 * #### Event: `deletedAll`
 * 
 * Emitted after an individual model has been deleted.
 *
 * ```js
 * MyModel.on('deletedAll', function(where) {
 *   if(where) {
 *     console.log('all models where', where, 'have been deleted');
 *     // => all models where
 *     // => {price: {gt: 100}}
 *     // => have been deleted
 *   }
 * });
 * ```
 * 
 * #### Event: `attached`
 * 
 * Emitted after a `Model` has been attached to an `app`.
 * 
 * #### Event: `dataSourceAttached`
 * 
 * Emitted after a `Model` has been attached to a `DataSource`.
 * 
 * @class
 * @param {Object} data
 * @property {String} modelName The name of the model
 * @property {DataSource} dataSource
 */

var Model = module.exports = registry.modelBuilder.define('Model');

/*!
 * Called when a model is extended.
 */

Model.setup = function () {
  var ModelCtor = this;
  var options = this.settings;

  // create a sharedClass
  var sharedClass = ModelCtor.sharedClass = new SharedClass(
    ModelCtor.modelName,
    ModelCtor,
    options.remoting
  );

  // support remoting prototype methods
  ModelCtor.sharedCtor = function (data, id, fn) {
    var ModelCtor = this;

    if(typeof data === 'function') {
      fn = data;
      data = null;
      id = null;
    } else if (typeof id === 'function') {
      fn = id;
    
      if(typeof data !== 'object') {
        id = data;
        data = null;
      } else {
        id = null;
      }
    }
  
    if(id && data) {
      var model = new ModelCtor(data);
      model.id = id;
      fn(null, model);
    } else if(data) {
      fn(null, new ModelCtor(data));
    } else if(id) {
      ModelCtor.findById(id, function (err, model) {
        if(err) {
          fn(err);
        } else if(model) {
          fn(null, model);
        } else {
          err = new Error('could not find a model with id ' + id);
          err.statusCode = 404;
        
          fn(err);
        }
      });
    } else {
      fn(new Error('must specify an id or data'));
    }
  }

  var idDesc = ModelCtor.modelName + ' id';
  ModelCtor.sharedCtor.accepts = [
    {arg: 'id', type: 'any', required: true, http: {source: 'path'},
      description: idDesc}
    // {arg: 'instance', type: 'object', http: {source: 'body'}}
  ];

  ModelCtor.sharedCtor.http = [
    {path: '/:id'}
  ];
  
  ModelCtor.sharedCtor.returns = {root: true};

  // before remote hook
  ModelCtor.beforeRemote = function (name, fn) {
    var self = this;
    if(this.app) {
      var remotes = this.app.remotes();
      var className = self.modelName;
      remotes.before(className + '.' + name, function (ctx, next) {
        fn(ctx, ctx.result, next);
      });
    } else {
      var args = arguments;
      this.once('attached', function () {
        self.beforeRemote.apply(self, args);
      });
    }
  };
  
  // after remote hook
  ModelCtor.afterRemote = function (name, fn) {
    var self = this;
    if(this.app) {
      var remotes = this.app.remotes();
      var className = self.modelName;
      remotes.after(className + '.' + name, function (ctx, next) {
        fn(ctx, ctx.result, next);
      });
    } else {
      var args = arguments;
      this.once('attached', function () {
        self.afterRemote.apply(self, args);
      });
    }
  };

  // resolve relation functions
  sharedClass.resolve(function resolver(define) {

    var relations = ModelCtor.relations || {};

    // get the relations
    for (var relationName in relations) {
      var relation = relations[relationName];
      if (relation.type === 'belongsTo') {
        ModelCtor.belongsToRemoting(relationName, relation, define)
      } else if (relation.type === 'hasOne') {
        ModelCtor.hasOneRemoting(relationName, relation, define)
      } else if (
        relation.type === 'hasMany' ||
        relation.type === 'embedsMany' ||
        relation.type === 'referencesMany') {
        ModelCtor.hasManyRemoting(relationName, relation, define);
      }
    }

    // handle scopes
    var scopes = ModelCtor.scopes || {};
    for (var scopeName in scopes) {
      ModelCtor.scopeRemoting(scopeName, scopes[scopeName], define);
    }
  });

  return ModelCtor;
};

/*!
 * Get the reference to ACL in a lazy fashion to avoid race condition in require
 */
var _aclModel = null;
Model._ACL = function getACL(ACL) {
  if(ACL !== undefined) {
    // The function is used as a setter
    _aclModel = ACL;
  }
  if(_aclModel) {
    return _aclModel;
  }
  var aclModel = require('./acl').ACL;
  _aclModel = registry.getModelByType(aclModel);
  return _aclModel;
};

/**
 * Check if the given access token can invoke the method
 *
 * @param {AccessToken} token The access token
 * @param {*} modelId The model ID.
 * @param {SharedMethod} sharedMethod The method in question
 * @param {Object} ctx The remote invocation context
 * @callback {Function} callback The callback function
 * @param {String|Error} err The error object
 * @param {Boolean} allowed True if the request is allowed; false otherwise.
 */

Model.checkAccess = function(token, modelId, sharedMethod, ctx, callback) {
  var ANONYMOUS = require('./access-token').ANONYMOUS;
  token = token || ANONYMOUS;
  var aclModel = Model._ACL();

  ctx = ctx || {};
  if(typeof ctx === 'function' && callback === undefined) {
    callback = ctx;
    ctx = {};
  }
  
  aclModel.checkAccessForContext({
    accessToken: token,
    model: this,
    property: sharedMethod.name,
    method: sharedMethod.name,
    sharedMethod: sharedMethod,
    modelId: modelId,
    accessType: this._getAccessTypeForMethod(sharedMethod),
    remotingContext: ctx
  }, function(err, accessRequest) {
    if(err) return callback(err);
    callback(null, accessRequest.isAllowed());
  });
};

/*!
 * Determine the access type for the given `RemoteMethod`.
 *
 * @api private
 * @param {RemoteMethod} method
 */

Model._getAccessTypeForMethod = function(method) {
  if(typeof method === 'string') {
    method = {name: method};
  }
  assert(
    typeof method === 'object', 
    'method is a required argument and must be a RemoteMethod object'
  );

  var ACL = Model._ACL();

  switch(method.name) {
    case'create':
      return ACL.WRITE;
    case 'updateOrCreate':
      return ACL.WRITE;
    case 'upsert':
      return ACL.WRITE;
    case 'exists':
      return ACL.READ;
    case 'findById':
      return ACL.READ;
    case 'find':
      return ACL.READ;
    case 'findOne':
      return ACL.READ;
    case 'destroyById':
      return ACL.WRITE;
    case 'deleteById':
      return ACL.WRITE;
    case 'removeById':
      return ACL.WRITE;
    case 'count':
      return ACL.READ;
    default:
      return ACL.EXECUTE;
  }
}

/**
 * Get the `Application` the Model is attached to.
 *
 * @callback {Function} callback
 * @param {Error} err
 * @param {Application} app
 * @end
 */

Model.getApp = function(callback) {
  var Model = this;
  if(this.app) {
    callback(null, this.app);
  } else {
    Model.once('attached', function() {
      assert(Model.app);
      callback(null, Model.app);
    });
  }
}

/**
 * Enable remote invocation for the method with the given name.
 * See [Remote methods and hooks](http://docs.strongloop.com/display/LB/Remote+methods+and+hooks for more information.
 * Static method example:
 * ```js
 * Model.myMethod();
 * Model.remoteMethod('myMethod');
 * ```
 * 
 * @param {String} name The name of the method.
 * @param {Object} options The remoting options.
 */

Model.remoteMethod = function(name, options) {
  if(options.isStatic === undefined) {
    options.isStatic = true;
  }
  this.sharedClass.defineMethod(name, options);
}

Model.belongsToRemoting = function(relationName, relation, define) {
  var modelName = relation.modelTo && relation.modelTo.modelName;
  modelName = modelName || 'PersistedModel';
  var fn = this.prototype[relationName];
  var pathName = (relation.options.http && relation.options.http.path) || relationName;
  define('__get__' + relationName, {
    isStatic: false,
    http: {verb: 'get', path: '/' + pathName},
    accepts: {arg: 'refresh', type: 'boolean', http: {source: 'query'}},
    description: 'Fetches belongsTo relation ' + relationName,
    returns: {arg: relationName, type: modelName, root: true}
  }, fn);
}

Model.hasOneRemoting = function(relationName, relation, define) {
  var fn = this.prototype[relationName];
  var pathName = (relation.options.http && relation.options.http.path) || relationName;
  define('__get__' + relationName, {
    isStatic: false,
    http: {verb: 'get', path: '/' + pathName},
    accepts: {arg: 'refresh', type: 'boolean', http: {source: 'query'}},
    description: 'Fetches hasOne relation ' + relationName,
    returns: {arg: relationName, type: relation.modelTo.modelName, root: true}
  }, fn);
}

Model.hasManyRemoting = function (relationName, relation, define) {
  var pathName = (relation.options.http && relation.options.http.path) || relationName;
  var toModelName = relation.modelTo.modelName;
  
  var findByIdFunc = this.prototype['__findById__' + relationName];
  define('__findById__' + relationName, {
    isStatic: false,
    http: {verb: 'get', path: '/' + pathName + '/:fk'},
    accepts: {arg: 'fk', type: 'any',
      description: 'Foreign key for ' + relationName, required: true,
      http: {source: 'path'}},
    description: 'Find a related item by id for ' + relationName,
    returns: {arg: 'result', type: toModelName, root: true}
  }, findByIdFunc);

  var destroyByIdFunc = this.prototype['__destroyById__' + relationName];
  define('__destroyById__' + relationName, {
    isStatic: false,
    http: {verb: 'delete', path: '/' + pathName + '/:fk'},
    accepts: {arg: 'fk', type: 'any',
      description: 'Foreign key for ' + relationName, required: true,
      http: {source: 'path'}},
    description: 'Delete a related item by id for ' + relationName,
    returns: {}
  }, destroyByIdFunc);

  var updateByIdFunc = this.prototype['__updateById__' + relationName];
  define('__updateById__' + relationName, {
    isStatic: false,
    http: {verb: 'put', path: '/' + pathName + '/:fk'},
    accepts: [
      {arg: 'fk', type: 'any',
        description: 'Foreign key for ' + relationName, required: true,
        http: {source: 'path'}},
      {arg: 'data', type: toModelName, http: {source: 'body'}}
    ],
    description: 'Update a related item by id for ' + relationName,
    returns: {arg: 'result', type: toModelName, root: true}
  }, updateByIdFunc);

  if (relation.modelThrough || relation.type === 'referencesMany') {
    var modelThrough = relation.modelThrough || relation.modelTo;
        
    var addFunc = this.prototype['__link__' + relationName];
    define('__link__' + relationName, {
      isStatic: false,
      http: {verb: 'put', path: '/' + pathName + '/rel/:fk'},
      accepts: {arg: 'fk', type: 'any',
        description: 'Foreign key for ' + relationName, required: true,
        http: {source: 'path'}},
      description: 'Add a related item by id for ' + relationName,
      returns: {arg: relationName, type: modelThrough.modelName, root: true}
    }, addFunc);

    var removeFunc = this.prototype['__unlink__' + relationName];
    define('__unlink__' + relationName, {
      isStatic: false,
      http: {verb: 'delete', path: '/' + pathName + '/rel/:fk'},
      accepts: {arg: 'fk', type: 'any',
        description: 'Foreign key for ' + relationName, required: true,
        http: {source: 'path'}},
      description: 'Remove the ' + relationName + ' relation to an item by id',
      returns: {}
    }, removeFunc);

    // FIXME: [rfeng] How to map a function with callback(err, true|false) to HEAD?
    // true --> 200 and false --> 404?
    var existsFunc = this.prototype['__exists__' + relationName];
    define('__exists__' + relationName, {
      isStatic: false,
      http: {verb: 'head', path: '/' + pathName + '/rel/:fk'},
      accepts: {arg: 'fk', type: 'any',
        description: 'Foreign key for ' + relationName, required: true,
        http: {source: 'path'}},
      description: 'Check the existence of ' + relationName + ' relation to an item by id',
      returns: {arg: 'exists', type: 'boolean', root: true},
      rest: {
        // After hook to map exists to 200/404 for HEAD
        after: function(ctx, cb) {
          if(ctx.result === false) {
            var modelName = ctx.method.sharedClass.name;
            var id = ctx.getArgByName('id');
            var msg = 'Unknown "' + modelName + '" id "' + id + '".';
            var error = new Error(msg);
            error.statusCode = error.status = 404;
            cb(error);
          } else {
            cb();
          }
        }
      }
    }, existsFunc);
  }
};

Model.scopeRemoting = function(scopeName, scope, define) {
  var pathName = (scope.options && scope.options.http && scope.options.http.path)
    || scopeName;
  var isStatic = scope.isStatic;
  var toModelName = scope.modelTo.modelName;

  define('__get__' + scopeName, {
    isStatic: isStatic,
    http: {verb: 'get', path: '/' + pathName},
    accepts: {arg: 'filter', type: 'object'},
    description: 'Queries ' + scopeName + ' of ' + this.modelName + '.',
    returns: {arg: scopeName, type: [toModelName], root: true}
  });

  define('__create__' + scopeName, {
    isStatic: isStatic,
    http: {verb: 'post', path: '/' + pathName},
    accepts: {arg: 'data', type: toModelName, http: {source: 'body'}},
    description: 'Creates a new instance in ' + scopeName + ' of this model.',
    returns: {arg: 'data', type: toModelName, root: true}
  });

  define('__delete__' + scopeName, {
    isStatic: isStatic,
    http: {verb: 'delete', path: '/' + pathName},
    description: 'Deletes all ' + scopeName + ' of this model.'
  });
};

Model.nestRemoting = function(relationName, options, cb) {
  if (typeof options === 'function' && !cb) {
    cb = options;
    options = {};
  }
  options = options || {};
  
  var regExp = /^__([^_]+)__([^_]+)$/;
  var relation = this.relations[relationName];
  if (relation && relation.modelTo && relation.modelTo.sharedClass) {
    var self = this;
    var sharedClass = this.sharedClass;
    var sharedToClass = relation.modelTo.sharedClass;
    var toModelName = relation.modelTo.modelName;
    
    var pathName = options.pathName || relation.options.path || relationName;
    var paramName = options.paramName || 'nk';
    
    var http = [].concat(sharedToClass.http || [])[0];
    
    if (relation.multiple) {
      var httpPath = pathName + '/:' + paramName;
      var acceptArgs = [
        { 
          arg: paramName, type: 'any', http: { source: 'path' }, 
          description: 'Foreign key for ' + relation.name,
          required: true
        }
      ];
    } else {
      var httpPath = pathName;
      var acceptArgs = [];
    }
    
    // A method should return the method name to use, if it is to be
    // included as a nested method - a falsy return value will skip.
    var filter = cb || options.filterMethod || function(method, relation) {
      var matches = method.name.match(regExp);
      if (matches) {
        return '__' + matches[1] + '__' + relation.name + '__' + matches[2];
      }
    };
    
    sharedToClass.methods().forEach(function(method) {
      var methodName;
      if (!method.isStatic && (methodName = filter(method, relation))) {
        var prefix = relation.multiple ? '__findById__' : '__get__';
        var getterName = options.getterName || (prefix + relationName);
        
        var getterFn = relation.modelFrom.prototype[getterName];
        if (typeof getterFn !== 'function') {
          throw new Error('Invalid remote method: `' + getterName + '`');
        }
        
        var nestedFn = relation.modelTo.prototype[method.name];
        if (typeof nestedFn !== 'function') {
          throw new Error('Invalid remote method: `' + method.name + '`');
        }
        
        var opts = {};
        
        opts.accepts = acceptArgs.concat(method.accepts || []);
        opts.returns = [].concat(method.returns || []);
        opts.description = method.description;
        opts.rest = extend({}, method.rest || {});
        opts.rest.delegateTo = method.name;
        
        opts.http = [];
        var routes = [].concat(method.http || []);
        routes.forEach(function(route) {
          if (route.path) {
            var copy = extend({}, route);
            copy.path = httpPath + route.path;
            opts.http.push(copy);
          }
        });
        
        if (relation.multiple) {
          sharedClass.defineMethod(methodName, opts, function(fkId) {
            var args = Array.prototype.slice.call(arguments, 1);
            var last = args[args.length - 1];
            var cb = typeof last === 'function' ? last : null;
            this[getterName](fkId, function(err, inst) {
              if (err && cb) return cb(err);
              if (inst instanceof relation.modelTo) {
                nestedFn.apply(inst, args);
              } else if (cb) {
                cb(err, null);
              }
            });
          }, method.isStatic);
        } else {
          sharedClass.defineMethod(methodName, opts, function() {
            var args = Array.prototype.slice.call(arguments);
            var last = args[args.length - 1];
            var cb = typeof last === 'function' ? last : null;
            this[getterName](function(err, inst) {
              if (err && cb) return cb(err);
              if (inst instanceof relation.modelTo) {
                nestedFn.apply(inst, args);
              } else if (cb) {
                cb(err, null);
              }
            });
          }, method.isStatic);
        }
      }
    });
    
    if (options.hooks === false) return; // don't inherit before/after hooks
    
    self.once('mounted', function(app, sc, remotes) {
      var listenerTree = extend({}, remotes.listenerTree || {});
      listenerTree.before = listenerTree.before || {};
      listenerTree.after = listenerTree.after || {};
      
      var beforeListeners = remotes.listenerTree.before[toModelName] || {};
      var afterListeners = remotes.listenerTree.after[toModelName] || {};
      
      sharedClass.methods().forEach(function(method) {
        var delegateTo = method.rest && method.rest.delegateTo;
        if (delegateTo) {
          var before = method.isStatic ? beforeListeners : beforeListeners['prototype'];
          var after = method.isStatic ? afterListeners : afterListeners['prototype'];
          var m = method.isStatic ? method.name : 'prototype.' + method.name;
          if (before[delegateTo]) {
            self.beforeRemote(m, function(ctx, result, next) {
              before[delegateTo]._listeners.call(null, ctx, next);
            });
          }
          if (after[delegateTo]) {
            self.afterRemote(m, function(ctx, result, next) {
              after[delegateTo]._listeners.call(null, ctx, next);
            });
          }
        }
      });
    });
    
  } else {
    throw new Error('Relation `' + relationName + '` does not exist for model `' + this.modelName + '`');
  }
};

// setup the initial model
Model.setup();