Merge 234cc45 into d63e1e2

infinitescroll/README.md

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+# Infinite Scroll List
+
+The problem is to design an infinite scroll list like you'd see in a
+webpage.
+
+The implementation should know how many total sites are possible for a
+list. Then *AddSites* is called to add more to your current list. Your
+list should be able to answer questions about sites not yet loaded too.

infinitescroll/problem.go

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+package infinitescroll
+
+// Checkbox represents the state of the select all checkbox
+type Checkbox int
+
+const (
+	// Checked is when the select all box is selected.
+	Checked Checkbox = iota
+	// Unchecked is when the select all box is deselected.
+	Unchecked
+	// Indeterminate is when the select all box is greyed out.
+	Indeterminate
+)
+
+type table struct {
+	currentState           Checkbox
+	sites                  map[string]bool
+	totalCount, clickCount uint64
+}
+
+// Table represents an infinite scroll list in a webpage.
+type Table interface {
+	AddSites(sites []string)
+	ToggleSelectAll()
+	CurrentState() Checkbox
+	IsClicked(site string) bool
+	Click(site string)
+}
+
+// NewTable creates a new instance of an Table
+func NewTable(totalCount uint64) Table {
+	return &table{sites: make(map[string]bool),
+		currentState: Unchecked, totalCount: totalCount}
+}
+
+func (ist *table) AddSites(sites []string) {
+	click := ist.CurrentState() == Checked
+	for _, site := range sites {
+		ist.sites[site] = click
+	}
+	if click {
+		ist.clickCount += uint64(len(sites))
+	}
+}
+
+func (ist *table) ToggleSelectAll() {
+	if ist.currentState == Checked {
+		ist.currentState = Unchecked
+		toggleAll(ist.sites, false)
+		ist.clickCount = 0
+	} else {
+		ist.currentState = Checked
+		toggleAll(ist.sites, true)
+		ist.clickCount = uint64(len(ist.sites))
+	}
+}
+
+func toggleAll(sites map[string]bool, click bool) {
+	for site := range sites {
+		sites[site] = click
+	}
+}
+
+func (ist *table) CurrentState() Checkbox { return ist.currentState }
+
+func (ist *table) IsClicked(site string) bool {
+	if ist.currentState == Checked {
+		return true
+	} else if ist.currentState == Unchecked {
+		return false
+	}
+	return ist.sites[site]
+}
+
+func (ist *table) Click(site string) {
+	if state := ist.CurrentState(); state == Unchecked || state == Checked {
+		ist.currentState = Indeterminate
+	}
+	clicked := ist.sites[site]
+	ist.sites[site] = !clicked
+	if clicked {
+		ist.clickCount--
+	} else {
+		ist.clickCount++
+	}
+	if ist.clickCount == 0 {
+		ist.currentState = Unchecked
+	}
+	if ist.clickCount == ist.totalCount {
+		ist.currentState = Checked
+	}
+}

infinitescroll/problem_test.go

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+package infinitescroll
+
+import "testing"
+
+func TestClickThenUnclick(t *testing.T) {
+	t.Parallel()
+	table := NewTable(3000)
+	table.AddSites([]string{"google", "yahoo", "microsoft", "amazon"})
+	table.Click("amazon")
+	if result := table.CurrentState(); result != Indeterminate {
+		t.Errorf("Expected Indeterminate but got %v", result)
+	}
+	table.Click("amazon")
+	if result := table.CurrentState(); result != Unchecked {
+		t.Errorf("Expected Unchecked but got %v", result)
+	}
+}
+
+func TestIsClickForSeenAndUnseen(t *testing.T) {
+	t.Parallel()
+	table := NewTable(5)
+	table.AddSites([]string{"google", "yahoo", "microsoft", "amazon"})
+	if clicked := table.IsClicked("unseen"); clicked {
+		t.Errorf("Should be unclicked")
+	}
+	if selectAll := table.CurrentState(); selectAll != Unchecked {
+		t.Errorf("Table should be unchecked for all here")
+	}
+	table.Click("amazon")
+	if selectAll := table.CurrentState(); selectAll != Indeterminate {
+		t.Errorf("Table should be indeterminate because 1 site is clicked")
+	}
+	if clicked := table.IsClicked("unseen"); clicked {
+		t.Errorf("Should be unclicked")
+	}
+}
+
+func TestToggleAll(t *testing.T) {
+	t.Parallel()
+	table := NewTable(3)
+	table.AddSites([]string{"google", "yahoo"})
+	table.ToggleSelectAll()
+	if clicked := table.IsClicked("google"); !clicked {
+		t.Errorf("Google should be clicked because of the toggle select all")
+	}
+	if clicked := table.IsClicked("yahoo"); !clicked {
+		t.Errorf("Yahoo should be clicked because of the toggle select all")
+	}
+	if clicked := table.IsClicked("amazon"); !clicked {
+		t.Errorf("Unseen Amazon should be clicked because of the toggle select all")
+	}
+	table.AddSites([]string{"amazon"})
+	table.ToggleSelectAll()
+	if clicked := table.IsClicked("google"); clicked {
+		t.Errorf("Google should be unclicked because of the toggle select all")
+	}
+	if clicked := table.IsClicked("yahoo"); clicked {
+		t.Errorf("Yahoo should be unclicked because of the toggle select all")
+	}
+	if clicked := table.IsClicked("amazon"); clicked {
+		t.Errorf("Amazon should be unclicked because of the toggle select all")
+	}
+}
+
+func TestToggleAllWithClicks(t *testing.T) {
+	t.Parallel()
+	table := NewTable(3)
+	table.ToggleSelectAll()
+	table.AddSites([]string{"google", "yahoo"})
+	if state := table.CurrentState(); state != Checked {
+		t.Errorf("Table should be checked for select all")
+	}
+	table.Click("google")
+	if state := table.CurrentState(); state != Indeterminate {
+		t.Errorf("Table should be indeterminate after a deselect click")
+	}
+	table.ToggleSelectAll()
+	if state := table.CurrentState(); state != Checked {
+		t.Errorf("Table should be select all")
+	}
+}
+
+func TestManuallySelectTotalSites(t *testing.T) {
+	t.Parallel()
+	table := NewTable(3)
+	table.AddSites([]string{"google", "yahoo", "amazon"})
+	if state := table.CurrentState(); state != Unchecked {
+		t.Errorf("Table should be unchecked")
+	}
+	table.Click("google")
+	table.Click("yahoo")
+	if state := table.CurrentState(); state != Indeterminate {
+		t.Errorf("Table should be indeterminate after two clicks")
+	}
+	table.Click("amazon")
+	if state := table.CurrentState(); state != Checked {
+		t.Errorf("Everything manually checked up to the total size")
+	}
+}