diff options
Diffstat (limited to 'background_scripts/completion_engines.coffee')
| -rw-r--r-- | background_scripts/completion_engines.coffee | 170 |
1 files changed, 9 insertions, 161 deletions
diff --git a/background_scripts/completion_engines.coffee b/background_scripts/completion_engines.coffee index 638d7f60..07ecfa26 100644 --- a/background_scripts/completion_engines.coffee +++ b/background_scripts/completion_engines.coffee @@ -4,18 +4,20 @@ # # Each completion engine defines three functions: # -# 1. "match" - This takes a searchUrl, and returns a boolean indicating whether this completion engine can +# 1. "match" - This takes a searchUrl and returns a boolean indicating whether this completion engine can # perform completion for the given search engine. # # 2. "getUrl" - This takes a list of query terms (queryTerms) and generates a completion URL, that is, a URL # which will provide completions for this completion engine. # # 3. "parse" - This takes a successful XMLHttpRequest object (the request has completed successfully), and -# returns a list of suggestions (a list of strings). +# returns a list of suggestions (a list of strings). This method is always executed within the context +# of a try/catch block, so errors do not propagate. +# +# Each new completion engine must be add to the list "CompletionEngines" at the bottom of this file. +# +# The lookup logic which uses these completion engines is in "./completion_search.coffee". # -# The main completion entry point is CompletionEngines.complete(). This implements all lookup and caching -# logic. It is possible to add new completion engines without changing the CompletionEngines infrastructure -# itself. # A base class for common regexp-based matching engines. class RegexpEngine @@ -106,7 +108,8 @@ class DummyCompletionEngine getUrl: -> chrome.runtime.getURL "content_scripts/vimium.css" parse: -> [] -completionEngines = [ +# Note: Order matters here. +CompletionEngines = [ Youtube Google DuckDuckGo @@ -116,160 +119,5 @@ completionEngines = [ DummyCompletionEngine ] -# A note on caching. -# Some completion engines allow caching, and Chrome serves up cached responses to requests (e.g. Google, -# Wikipedia, YouTube). Others do not (e.g. Bing, DuckDuckGo, Amazon). A completion engine can set -# @doNotCache to a truthy value to disable caching in cases where it is unnecessary. - -CompletionEngines = - debug: true - - # The amount of time to wait for new requests before launching the HTTP request. The intention is to cut - # down on the number of HTTP requests we issue. - # delay: 100 - delay: 0 - - get: (searchUrl, url, callback) -> - xhr = new XMLHttpRequest() - xhr.open "GET", url, true - xhr.timeout = 1000 - xhr.ontimeout = xhr.onerror = -> callback null - xhr.send() - - xhr.onreadystatechange = -> - if xhr.readyState == 4 - callback(if xhr.status == 200 then xhr else null) - - # Look up the completion engine for this searchUrl. Because of DummyCompletionEngine, above, we know there - # will always be a match. Imagining that there may be many completion engines, and knowing that this is - # called for every query, we cache the result. - lookupEngine: (searchUrl) -> - @engineCache ?= new SimpleCache 30 * 60 * 60 * 1000 # 30 hours (these are small, we can keep them longer). - if @engineCache.has searchUrl - @engineCache.get searchUrl - else - for engine in completionEngines - engine = new engine() - return @engineCache.set searchUrl, engine if engine.match searchUrl - - # True if we have a completion engine for this search URL, undefined otherwise. - haveCompletionEngine: (searchUrl) -> - not @lookupEngine(searchUrl).dummy - - # This is the main entry point. - # - searchUrl is the search engine's URL, e.g. Settings.get("searchUrl"), or a custome search engine's URL. - # This is only used as a key for determining the relevant completion engine. - # - queryTerms are the query terms. - # - callback will be applied to a list of suggestion strings (which may be an empty list, if anything goes - # wrong). - complete: (searchUrl, queryTerms, callback = null) -> - @mostRecentHandler = null - query = queryTerms.join "" - - # If no callback is provided, then we're to provide suggestions only if we can do so synchronously (ie. - # from a cache). In this case we return the results and don't call callback. Return null if we cannot - # service the request synchronously. - returnResultsOnlyFromCache = not callback? - callback ?= (suggestions) -> suggestions - - # We don't complete single characters: the results are usually useless. - return callback [] unless 1 < query.length - - # We don't complete regular URLs or Javascript URLs. - return callback [] if 1 == queryTerms.length and Utils.isUrl query - return callback [] if Utils.hasJavascriptPrefix query - - # Cache completions. However, completions depend upon both the searchUrl and the query terms. So we need - # to generate a key. We mix in some junk generated by pwgen. A key clash might be possible, but - # vanishingly unlikely. - junk = "//Zi?ei5;o//" - completionCacheKey = searchUrl + junk + queryTerms.map((s) -> s.toLowerCase()).join junk - @completionCache ?= new SimpleCache 60 * 60 * 1000, 2000 # One hour, 2000 entries. - if @completionCache.has completionCacheKey - if returnResultsOnlyFromCache - return @completionCache.get completionCacheKey - else - # We add a short delay, even for a cache hit. This avoids an ugly flicker when the additional - # suggestions are posted. - Utils.setTimeout 50, => - console.log "hit", completionCacheKey if @debug - callback @completionCache.get completionCacheKey - return - - if @mostRecentQuery? and @mostRecentSuggestions? - # If the user appears to be typing a continuation of the characters of the most recent query, then we - # can re-use the previous suggestions. - reusePreviousSuggestions = do (query) => - query = queryTerms.join(" ").toLowerCase() - # Verify that the previous query is a prefix of the current query. - return false unless 0 == query.indexOf @mostRecentQuery.toLowerCase() - # Ensure that every previous suggestion contains the text of the new query. - for suggestion in (@mostRecentSuggestions.map (s) -> s.toLowerCase()) - return false unless 0 <= suggestion.indexOf query - # Ok. Re-use the suggestion. - true - - if reusePreviousSuggestions - console.log "reuse previous query:", @mostRecentQuery if @debug - @mostRecentQuery = queryTerms.join " " - return callback @completionCache.set completionCacheKey, @mostRecentSuggestions - - return null if returnResultsOnlyFromCache - - fetchSuggestions = (engine, callback) => - url = engine.getUrl queryTerms - query = queryTerms.join(" ").toLowerCase() - @get searchUrl, url, (xhr = null) => - # Parsing the response may fail if we receive an unexpected or an unexpectedly-formatted response. In - # all cases, we fall back to the catch clause, below. Therefore, we "fail safe" in the case of - # incorrect or out-of-date completion engines. - try - suggestions = engine.parse xhr - # Make sure we really do have an iterable of strings. - suggestions = (suggestion for suggestion in suggestions when "string" == typeof suggestion) - # Filter out the query itself. It's not adding anything. - suggestions = (suggestion for suggestion in suggestions when suggestion.toLowerCase() != query) - console.log "GET", url if @debug - catch - suggestions = [] - # We allow failures to be cached, but remove them after just ten minutes. This (it is hoped) avoids - # repeated unnecessary XMLHttpRequest failures over a short period of time. - removeCompletionCacheKey = => @completionCache.set completionCacheKey, null - setTimeout removeCompletionCacheKey, 10 * 60 * 1000 # Ten minutes. - console.log "fail", url if @debug - - callback suggestions - - # We pause in case the user is still typing. - Utils.setTimeout @delay, handler = @mostRecentHandler = => - if handler != @mostRecentHandler - # Bail! Another completion has begun, or the user is typing. - # NOTE: We do *not* call the callback (because we are not providing results, and we don't want allow - # any higher-level component to cache the results -- specifically, the vomnibar itself, via - # callerMayCacheResults). - console.log "bail", completionCacheKey if @debug - return - @mostRecentHandler = null - # Don't allow duplicate identical active requests. This can happen, for example, when the user enters or - # removes a space, or when they enter a character and immediately delete it. - @inTransit ?= {} - unless @inTransit[completionCacheKey]?.push callback - queue = @inTransit[completionCacheKey] = [] - engine = @lookupEngine searchUrl - fetchSuggestions engine, (suggestions) => - @mostRecentQuery = queryTerms.join " " - @mostRecentSuggestions = suggestions - @completionCache.set completionCacheKey, suggestions unless engine.doNotCache - callback suggestions - delete @inTransit[completionCacheKey] - console.log "callbacks", queue.length, completionCacheKey if @debug and 0 < queue.length - callback suggestions for callback in queue - - # Cancel any pending (ie. blocked on @delay) queries. Does not cancel in-flight queries. - cancel: -> - if @mostRecentHandler? - @mostRecentHandler = null - console.log "cancel (user is typing)" if @debug - root = exports ? window root.CompletionEngines = CompletionEngines |