local function createLabel(ownerFrame, fontObject)
	assert (ownerFrame ~= nil)

	local t = ownerFrame:CreateFontString((ownerFrame:GetName() or '') .. 'Text', 'OVERLAY')
	fontObject = fontObject or NumberFont_OutlineThick_Mono_Small
	assert (fontObject ~= nil)
	t:SetFontObject(fontObject)
	t:SetAllPoints()

	return t
end

local function createBackground(ownerFrame)
	assert (ownerFrame ~= nil)

	local background = ownerFrame:CreateTexture(ownerFrame:GetName() .. 'Background', 'BACKGROUND')
	background:SetAllPoints()
	background:SetTexture(0, 0, 0, 0.8)

	return background
end

local function createUnitButton(parentFrame, frameName, unit)
	assert (parentFrame ~= nil)
	assert (frameName ~= nil)
	assert (unit ~= nil)

	local u = CreateFrame('BUTTON', frameName, parentFrame, 'SecureUnitButtonTemplate')
	u:SetAttribute('type', 'target')
	u:SetAttribute('unit', unit)

	u:SetSize(12 * 6, 12 * 2)

	u.text = createLabel(u)

	local b = createBackground(u)
	b:SetTexture(1.0, 0.0, 0.4, 1.0)
	u.background = b

	u:SetScript('OnEvent', function(self)
		assert (self ~= nil)
		local label = self.text
		assert (label ~= nil)
		local unitDesignation = self:GetAttribute('unit')
		assert (unitDesignation ~= nil)
		label:SetText(UnitName(unitDesignation) or unitDesignation)
	end)
	u:RegisterEvent('PARTY_CONVERTED_TO_RAID')
	u:RegisterEvent('PARTY_MEMBERS_CHANGED')
	u:RegisterEvent('PLAYER_ALIVE')
	u:RegisterEvent('RAID_ROSTER_UPDATE')
	u:RegisterEvent('UPDATE_BATTLEFIELD_SCORE')
	u:RegisterEvent('ADDON_LOADED')

	assert (u ~= nil)
	return u
end

local function createSpoiler(spoilerParent, spoilerDesignation)
	local spoiler = CreateFrame('BUTTON', spoilerDesignation, spoilerParent, 'SecureHandlerClickTemplate')
	spoiler:EnableMouse(true)
	spoiler:SetAttribute('_onclick', [=[
		local debugFlag = true
		local parentFrame = self:GetParent()
		local siblingTable = parentFrame:GetChildList(newtable())
		local i = 0
		while (i < #siblingTable) do
			i = i + 1
			local sibling = siblingTable[i]
			sibling:ClearBindings()
			sibling:Hide()
		end

		self:Show()
		local j = 0
		local childTable = self:GetChildList(newtable())
		--[[local bindingTable = newtable(
			'A', 'S', 'D', 'F', 'G'
		)]]--
		while (j < #childTable) do
			j = j + 1
			local child = childTable[j]
			local unitDesignation = child:GetAttribute('unit')
			if unitDesignation ~= nil and UnitExists(unitDesignation) and not debugFlag then
				child:Show()
			elseif debugFlag then
				child:Show()
			else
				child:Hide()
			end
			print('child', child:GetName())
			local key = GetBindingKey('CLICK ChoirUnitButton' .. tostring(j) .. ':LeftButton')
			--local key = bindingTable[math.min(j, #childTable)]
			if key then
				self:SetBindingClick(true, key, child)
			end
		end
	]=])

	return spoiler
end

local function createGroup(rootFrame, groupNumber, unitTable)
	assert (rootFrame ~= nil)

	assert (groupNumber ~= nil)
	groupNumber = math.floor(math.abs(groupNumber))
	assert ((groupNumber >= 1 and groupNumber <= 8) or unitTable ~= nil)

	local groupSize = 5

	local u
	if unitTable then
		u = unitTable
	else
		local q = 0
		u = {}
		while (q < groupSize) do
			q = q + 1
			u[q] = 'raid' .. tostring((groupNumber - 1) * groupSize + q)
		end
	end
	assert (u ~= nil)
	assert ('table' == type(u))
	assert (#u == groupSize)

	local spoiler = createSpoiler(rootFrame, 'ChoirSpoiler' .. tostring(groupNumber))
	spoiler:SetSize(12 * 6, 12 * 2)
	spoiler:SetPoint('CENTER', 0, 144)

	local i = 0
	local marginLeft = spoiler:GetWidth()
	local padding = 4
	while (i < #u) do
		i = i + 1
		local unitDesignation = u[i]
		assert (unitDesignation ~= nil)
		local memberNumber = (groupNumber - 1) * groupSize + i
		local b = createUnitButton(spoiler, 'ChoirUnitButton' .. tostring(memberNumber), unitDesignation)
		b:SetPoint('BOTTOMLEFT', marginLeft + padding, 0)
		marginLeft = marginLeft + b:GetWidth() + padding

		spoiler:WrapScript(b, 'OnClick', [=[
			print('OnClick', self:GetName())
			local parentFrame = self:GetParent()
			parentFrame:Hide()
		]=])
		b:Hide()

		_G['BINDING_NAME_CLICK ' .. b:GetName() .. ':LeftButton'] = 'Unit ' .. tostring(i)
	end

	_G['BINDING_NAME_CLICK ' .. spoiler:GetName() .. ':LeftButton'] = 'Group ' .. tostring(groupNumber)

	return spoiler
end

local function init(rootFrame)
	assert (rootFrame ~= nil)

	rootFrame:UnregisterAllEvents()

	rootFrame:SetSize(1024, 768)
	rootFrame:SetPoint('CENTER', 0, 0)

	createGroup(rootFrame, 1)
	createGroup(rootFrame, 2)
	createGroup(rootFrame, 3)
	createGroup(rootFrame, 4)
	createGroup(rootFrame, 5)
	createGroup(rootFrame, 6)
	createGroup(rootFrame, 7)
	createGroup(rootFrame, 8)

	--[[ TODO Add Esc key that closes the spoiler without clicking any of the children buttons ]]--
	--[[ TODO Generalize the interface to be used with any kind of child frames, especially nested spoilers and spell buttons ]]--
	local spoilerParty = createGroup(rootFrame, 9, {'player', 'party1', 'party2', 'party3', 'party4'})
	_G['BINDING_NAME_CLICK ' .. spoilerParty:GetName() .. ':LeftButton'] = 'Player party'

	BINDING_HEADER_CHOIR = 'Choir'

	print('[Choir]: init')
end

local function main()
	local rootFrame = CreateFrame('FRAME', 'ChoirFrame', UIParent)
	rootFrame:RegisterEvent('ADDON_LOADED')
	rootFrame:SetScript('OnEvent', init)
end
main()