git ssb

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var { h, Value, Dict, dictToCollection, map, computed } = require('mutant')
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var nest = require('depnest')
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exports.gives = nest('app.views')
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exports.create = function (api) {
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  return nest('app.views', function (renderPage, defaultViews) {
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    var views = Dict({})
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    var forwardHistory = []
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    var backHistory = []
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    if (defaultViews) {
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      defaultViews.forEach((view) => {
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        views.put(view, renderPage(view))
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      })
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    }
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    var lastViewed = {}
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    // delete cached view after 5 mins of last seeing
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    setInterval(() => {
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      views.keys().forEach((view) => {
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        if (!defaultViews.includes(view)) {
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          if (lastViewed[view] !== true && Date.now() - lastViewed[view] > (5 * 60e3) && view !== currentView()) {
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            views.delete(view)
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          }
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        }
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      })
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    }, 60e3)
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    var canGoForward = Value(false)
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    var canGoBack = Value(false)
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    var currentView = Value(defaultViews && defaultViews[0] || null)
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    var viewCollection = dictToCollection(views)
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    var html = h('div.main', map(viewCollection, (item) => {
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      return h('div.view', {
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        attributes: {
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          'data-href': item.key
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        },
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        hidden: computed([item.key, currentView], (a, b) => a !== b)
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      }, [ item.value ])
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    }))
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    return {
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      get: views.get,
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      defaultViews,
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      canGoForward,
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      canGoBack,
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      currentView,
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      setView,
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      goBack,
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      goForward,
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      html
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    }
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    // scoped
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    function goBack () {
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      if (backHistory.length) {
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        canGoForward.set(true)
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        forwardHistory.push(currentView())
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        var view = backHistory.pop()
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        loadView(view)
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        currentView.set(view)
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        canGoBack.set(backHistory.length > 0)
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      }
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    }
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    function goForward () {
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      if (forwardHistory.length) {
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        backHistory.push(currentView())
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        var view = forwardHistory.pop()
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        loadView(view)
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        currentView.set(view)
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        canGoForward.set(forwardHistory.length > 0)
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        canGoBack.set(true)
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      }
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    }
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    function loadView (view) {
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      if (!views.has(view)) {
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        var page = renderPage(view)
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        if (page.uniqueKey) {
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          views.keys().forEach(k => {
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            if (views.get(k).uniqueKey === page.uniqueKey) {
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              views.delete(k)
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            }
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          })
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        }
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        views.put(view, page)
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      }
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    }
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    function setView (view) {
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      loadView(view)
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      if (lastViewed[view] !== true) {
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        lastViewed[view] = Date.now()
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      }
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      if (currentView() && lastViewed[currentView()] !== true) {
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        lastViewed[currentView()] = Date.now()
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      }
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      if (view !== currentView()) {
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        canGoForward.set(false)
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        canGoBack.set(true)
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        forwardHistory.length = 0
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        backHistory.push(currentView())
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        currentView.set(view)
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      }
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    }
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  })
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}
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