gecko/content/xul/templates/public/nsIXULTemplateQueryProcessor.idl
2012-05-21 12:12:37 +01:00

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "domstubs.idl"
#include "nsISupports.idl"
interface nsIAtom;
interface nsIArray;
interface nsISimpleEnumerator;
interface nsIXULTemplateResult;
interface nsIXULTemplateRuleFilter;
interface nsIXULTemplateBuilder;
/**
* A query processor takes a template query and generates results for it given
* a datasource and a reference point. There is a one-to-one relationship
* between a template builder and a query processor. The template builder
* creates the query processor, and there is no other means to retrieve it.
*
* A template query is the contents inside a <query> element within the
* template. The actual syntax is opaque to the template builder and defined
* by a query processor. The query is expected to consist of either text or
* DOM nodes that, when executed by a call to the generateResults method, will
* allow the generation of a list of results.
*
* The template builder will supply two variables, the reference variable and
* the member variable to further indicate what part of the datasource is to
* be examined in addition to the query itself. The reference is always
* a placeholder for the starting point and the member is always a placeholder
* for the end points (the results).
*
* The reference point is important when generating output recursively, as
* the query will be the same for each iteration, however, the reference point
* will differ.
*
* For instance, when examining an XML source, an XML query processor might
* begin at the node referred by the reference variable and end at a list of
* that node's children.
*
* Some queries may not need the reference variable if the syntax or the form
* of the data implies the value. For instance, a datasource that holds a
* table that can only produce one set of results.
*
* The reference variable may be specified in a template by setting the
* "container" attribute on the <template> element to the variable to use. The
* member variable may be specified in a similar way using the "member"
* attribute, or it may be specified in the first <action> body in the
* template as the value of a uri attribute on an element. A breadth-first
* search of the first action is performed to find this element.
*
* If unspecified, the default value of the reference variable is ?uri.
*
* For example, a query might have the following syntax:
*
* (?id, ?name, ?url) from Bookmarks where parentfolder = ?start
*
* This query might generate a result for each bookmark within a given folder.
* The variable ?start would be the reference variable, while the variable ?id
* would be the member variable, since it is the unique value that identifies
* a result. Each result will have the four variables referred to defined for
* it and the values may be retrieved using the result's getBindingFor and
* getBindingObjectFor methods.
*
* The template builder must call initializeForBuilding before the other
* methods, except for translateRef. The builder will then call compileQuery
* for each query in the template to compile the queries. When results need
* to be generated, the builder will call generateResults. The
* initializeForBuilding, compileQuery and addBinding methods may not be
* called after generateResults has been called until the builder indicates
* that the generated output is being removed by calling the done method.
*
* Currently, the datasource supplied to the methods will always be an
* nsIRDFDataSource or a DOM node, and will always be the same one in between
* calls to initializeForBuilding and done.
*/
[scriptable, uuid(C257573F-444F-468A-BA27-DE979DC55FE4)]
interface nsIXULTemplateQueryProcessor : nsISupports
{
/**
* Retrieve the datasource to use for the query processor. The list of
* datasources in a template is specified using the datasources attribute as
* a space separated list of URIs. This list is processed by the builder and
* supplied to the query processor in the aDataSources array as a list of
* nsIURI objects or nsIDOMNode objects. This method may return an object
* corresponding to these URIs and the builder will supply this object to
* other query processor methods. For example, for an XML source, the
* datasource might be an nsIDOMNode.
*
* All of these URIs are checked by the builder so it is safe to use them,
* however note that a URI that redirects may still needs to be checked to
* ensure that the document containing aRootNode may access it. This is the
* responsibility of the query processor if it needs to load the content of
* the URI.
*
* If the query processor needs to load the datasource asynchronously, it
* may set the aShouldDelayBuilding returned parameter to true to delay
* building the template content, and call the builder's Rebuild method when
* the data is available.
*
* @param aDataSources the list of nsIURI objects and/or nsIDOMNode objects
* @param aRootNode the root node the builder is attached to
* @param aIsTrusted true if the template is in a trusted document
* @param aBuilder the template builder
* @param aShouldDelayBuilding [out] whether the builder should wait to
* build the content or not
* @returns a datasource object
*/
nsISupports getDatasource(in nsIArray aDataSources,
in nsIDOMNode aRootNode,
in boolean aIsTrusted,
in nsIXULTemplateBuilder aBuilder,
out boolean aShouldDelayBuilding);
/**
* Initialize for query generation. This will be called before the rules are
* processed and whenever the template is rebuilt. This method must be
* called once before any of the other query processor methods except for
* translateRef.
*
* @param aDatasource datasource for the data
* @param aBuilder the template builder
* @param aRootNode the root node the builder is attached to
*
* @throws NS_ERROR_INVALID_ARG if the datasource is not supported or
* NS_ERROR_UNEXPECTED if generateResults has already been called.
*/
void initializeForBuilding(in nsISupports aDatasource,
in nsIXULTemplateBuilder aBuilder,
in nsIDOMNode aRootNode);
/**
* Called when the template builder is being destroyed so that the query
* processor can clean up any state. The query processor should remove as
* much state as possible, such as results or references to the builder.
* This method will also be called when the template is going to be rebuilt.
*/
void done();
/**
* Compile a query from a node. The result of this function will later be
* passed to generateResults for result generation. If null is returned,
* the query will be ignored.
*
* The template builder will call this method once for each query within
* the template, before any results can be generated using generateResults,
* but after initializeForBuilding has been called. This method should not
* be called again for the same query unless the template is rebuilt.
*
* The reference variable may be used by the query processor as a
* placeholder for the reference point, or starting point in the query.
*
* The member variable is determined from the member attribute on the
* template, or from the uri in the first action's rule if that attribute is
* not present. A rule processor may use the member variable as a hint to
* indicate what variable is expected to contain the results.
*
* @param aBuilder the template builder
* @param aQuery <query> node to compile
* @param aRefVariable the reference variable
* @param aMemberVariable the member variable
*
* @returns a compiled query object
*/
nsISupports compileQuery(in nsIXULTemplateBuilder aBuilder,
in nsIDOMNode aQuery,
in nsIAtom aRefVariable,
in nsIAtom aMemberVariable);
/**
* Generate the results of a query and return them in an enumerator. The
* enumerator must contain nsIXULTemplateResult objects. If there are no
* results, an empty enumerator must be returned.
*
* The datasource will be the same as the one passed to the earlier
* initializeForBuilding method. The context reference (aRef) is a reference
* point used when calculating results.
*
* The value of aQuery must be the result of a previous call to compileQuery
* from this query processor. This method may be called multiple times,
* typically with different values for aRef.
*
* @param aDatasource datasource for the data
* @param aRef context reference value used as a starting point
* @param aQuery the compiled query returned from query compilation
*
* @returns an enumerator of nsIXULTemplateResult objects as the results
*
* @throws NS_ERROR_INVALID_ARG if aQuery is invalid
*/
nsISimpleEnumerator generateResults(in nsISupports aDatasource,
in nsIXULTemplateResult aRef,
in nsISupports aQuery);
/**
* Add a variable binding for a particular rule. A binding allows an
* additional variable to be set for a result, outside of those defined
* within the query. These bindings are always optional, in that they will
* never affect the results generated.
*
* This function will never be called after generateResults. Any bindings
* that were added should be applied to each result when the result's
* ruleMatched method is called, since the bindings are different for each
* rule.
*
* The reference aRef may be used to determine the reference when
* calculating the value for the binding, for example when a value should
* depend on the value of another variable.
*
* The syntax of the expression aExpr is defined by the query processor. If
* the syntax is invalid, the binding should be ignored. Only fatal errors
* should be thrown, or NS_ERROR_UNEXPECTED if generateResults has already
* been called.
*
* As an example, if the reference aRef is the variable '?count' which
* holds the value 5, and the expression aExpr is the string '+2', the value
* of the variable aVar would be 7, assuming the query processor considers
* the syntax '+2' to mean add two to the reference.
*
* @param aRuleNode rule to add the binding to
* @param aVar variable that will be bound
* @param aRef variable that holds reference value
* @param aExpr expression used to compute the value to assign
*/
void addBinding(in nsIDOMNode aRuleNode,
in nsIAtom aVar,
in nsIAtom aRef,
in AString aExpr);
/**
* Translate a ref attribute string into a result. This is used as the
* reference point by the template builder when generating the first level
* of content. For recursive generation, the result from the parent
* generation phase will be used directly as the reference so a translation
* is not needed. This allows all levels to be generated using objects that
* all implement the nsIXULTemplateResult interface.
*
* This method may be called before initializeForBuilding, so the
* implementation may use the supplied datasource if it is needed to
* translate the reference.
*
* @param aDatasource datasource for the data
* @param aRefString the ref attribute string
*
* @return the translated ref
*/
nsIXULTemplateResult translateRef(in nsISupports aDatasource,
in AString aRefString);
/**
* Compare two results to determine their order, used when sorting results.
* This method should return -1 when the left result is less than the right,
* 0 if both are equivalent, and 1 if the left is greater than the right.
* The comparison should only consider the values for the specified
* variable.
*
* If the comparison variable is null, the results may be
* sorted in a natural order, for instance, based on the order the data in
* stored in the datasource.
*
* The sort hints are the flags in nsIXULSortService.
*
* This method must only be called with results that were created by this
* query processor.
*
* @param aLeft the left result to compare
* @param aRight the right result to compare
* @param aVar variable to compare
*
* @param returns -1 if less, 0 if equal, or 1 if greater
*/
PRInt32 compareResults(in nsIXULTemplateResult aLeft,
in nsIXULTemplateResult aRight,
in nsIAtom aVar,
in unsigned long aSortHints);
};