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55 lines
1.4 KiB
CoffeeScript
55 lines
1.4 KiB
CoffeeScript
_ = require 'underscore'
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{NylasStore, DatabaseStore} = require 'nylas-exports'
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class RefreshingJSONCache
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constructor: ({@key, @version, @refreshInterval}) ->
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@_timeoutId = null
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start: ->
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# Clear any scheduled actions
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@end()
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# Look up existing data from db
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DatabaseStore.findJSONBlob(@key).then (json) =>
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# Refresh immediately if json is missing or version is outdated. Otherwise,
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# compute next refresh time and schedule
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timeUntilRefresh = 0
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if json? and json.version is @version
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timeUntilRefresh = Math.max(0, @refreshInterval - (Date.now() - json.time))
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@_timeoutId = setTimeout(@refresh, timeUntilRefresh)
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reset: ->
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# Clear db value, turn off any scheduled actions
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DatabaseStore.inTransaction (t) => t.persistJSONBlob(@key, {})
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@end()
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end: ->
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# Turn off any scheduled actions
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clearInterval(@_timeoutId) if @_timeoutId
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@_timeoutId = null
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refresh: =>
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# Set up next refresh call
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clearTimeout(@_timeoutId) if @_timeoutId
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@_timeoutId = setTimeout(@refresh, @refreshInterval)
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# Call fetch data function, save it to the database
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@fetchData (newValue) =>
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DatabaseStore.inTransaction (t) =>
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t.persistJSONBlob(@key, {
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version: @version
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time: Date.now()
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value: newValue
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})
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fetchData: (callback) =>
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throw new Error("Subclasses should override this method.")
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module.exports = RefreshingJSONCache
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