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package info.bliki.wiki.model;

import info.bliki.wiki.template.extension.AttributeRenderer;

/**
 * Interface for rendering a wiki model
 *
 */
public interface IContext {

    /**
     * Resolve an attribute reference. It can be in four possible places:
     *
     * 1. the attribute list for the current template 2. if self is an embedded
     * template, somebody invoked us possibly with arguments--check the argument
     * context 3. if self is an embedded template, the attribute list for the
     * enclosing instance (recursively up the enclosing instance chain) 4. if
     * nothing is found in the enclosing instance chain, then it might be a map
     * defined in the group or the its supergroup etc...
     *
     * Attribute references are checked for validity. If an attribute has a value,
     * its validity was checked before template rendering. If the attribute has no
     * value, then we must check to ensure it is a valid reference. Somebody could
     * reference any random value like $xyz$; formal arg checks before rendering
     * cannot detect this--only the ref can initiate a validity check. So, if no
     * value, walk up the enclosed template tree again, this time checking formal
     * parameters not attributes Map. The formal definition must exist even if no
     * value.
     *
     * To avoid infinite recursion in toString(), we have another condition to
     * check regarding attribute values. If your template has a formal argument,
     * foo, then foo will hide any value available from "above" in order to
     * prevent infinite recursion.
     *
     * This method is not static so people can override functionality.
     */
    public Object getAttribute(String attribute);

    /**
     * Set an attribute for this template. If you set the same attribute more than
     * once, you get a multi-valued attribute. If you send in a StringTemplate
     * object as a value, it's enclosing instance (where it will inherit values
     * from) is set to 'this'. This would be the normal case, though you can set
     * it back to null after this call if you want. If you send in a List plus
     * other values to the same attribute, they all get flattened into one List of
     * values. This will be a new list object so that incoming objects are not
     * altered. If you send in an array, it is converted to an ArrayIterator.
     */
    public void setAttribute(String name, Object value);

    /**
     * What renderer is registered for this attributeClassType for this template.
     * If not found, the template's group is queried.
     */
    public AttributeRenderer getAttributeRenderer(Class attributeClassType);

    /**
     * Register a renderer for all objects of a particular type. This overrides
     * any renderer set in the group for this class type.
     */
    public void registerRenderer(Class attributeClassType, AttributeRenderer renderer);
}