wowheadr (pronounced "wow header") is a Ruby gem designed to help leverage the power the Powered by Wowhead JavaScript API. It can help generate links to items, achievements, spells, and other entities in the Wowhead database.
You can generate URLs for (currently) items, achievements, and spells, providing you know the ID for the entity you want a URL for. Use the methods in Wowheadr::URI to generate the URLs. For example, to generate a URL for the item "Bloodied Prison Shank" (http://www.wowhead.com/item=43659), you would use:
gift = Wowheadr::URI.item(43659)
And, to generate a URL for the ability "Bear Form" (http://www.wowhead.com/spell=5487), you would use:
sum_durids = Wowheadr::URI.spell(5487)
Wowhead provides the ability to customize links to various entities on their site using the rel property of the HTML link tag. Wowheadr supports this via the Wowheadr::Entity classes. (Currently, only Item and Spell are available.)
For example, to get the rel attribute for a link to a "Bloodied Arcanite Reaper" (http://www.wowhead.com/item=42943) tuned for a level 25 character, you can use:
zinwrath = Wowheadr::Entity::Item.id(42943).level(25).to_s
(Calling to_s on any Entity class returns the text that should be placed in the rel attribute of your link, as shown:)
<a hef="http://www.warcraftmovies.com/movieview.php?id=7558" rel="item=42943&lvl=25">Arcanite Reaper, HOOOOO</a>
You can add enchants, gems, sockets, other set pieces, and more to an Item:
Wowheadr::Entity::Item.id(25697).gems(23121).enchant(2647).pieces(25695, 25696, 25697)
Spells work similarly. You can change the level using the level() method (for spell scaling), and you can use the buff() method to cause the tooltip to show the buff or debuff the spell causes rather than the spell itself.
man_angle = Wowheadr::Entity::Spell.new(33878).level(10).to_s
level_ten_rel = man_angle.level(10).to_s
debuff_rel = man_angle.buff(true).to_s
More is planned in the immediate future, including a Ruby on Rails gem that provides various helper methods to make integrating Powered by Wowhead even easier. Stay tuned!