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authorMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
committerMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
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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"
+
+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
+ */
+ int32_t compareResults(in nsIXULTemplateResult aLeft,
+ in nsIXULTemplateResult aRight,
+ in nsIAtom aVar,
+ in unsigned long aSortHints);
+};