function widget:GetInfo()
  return {
    name      = "Attack Warning",
    desc      = "Warns if stuff gets attacked",
    author    = "knorke, Birdulon",
    date      = "Oct 2011, June 2020",
    license   = "GNU GPL, v2 or later",
    layer     = 0,
    enabled   = true,
  }
end

options_path = "Settings/Alerts"
options_order = {
	'voiceSelfVolume', 'voiceAllyVolume', 'voiceSelfCooldown', 'voiceAllyCooldown',
	'markersEnable', 'markersSelfDuration', 'markersAllyDuration', 'markersSelfRadius', 'markersAllyRadius',
}
options = {
	markersEnable = {
		name = "Enable attack alert markers",
		type = "bool",
		value = true,
		desc = "Place temporary map markers to increase visibility of off-screen attacks",
		noHotkey = true,
	},
	markersSelfDuration = {
		name = "Attack marker duration (s) - self",
		type = "number",
		value = 5.0,
		min = 0.5,
		max = 15.0,
		step = 0.5,
		desc = "Attack markers for your own forces will be removed after this many seconds",
		noHotkey = true,
	},
	markersSelfRadius = {
		name = "Attack marker spacing (elmo) - self",
		type = "number",
		value = 750,
		min = 250,
		max = 2000,
		step = 250,
		desc = "If your forces are attacked within this distance of an existing attack marker, suppress the alert",
		noHotkey = true,
	},
	markersAllyDuration = {
		name = "Attack marker duration (s) - ally",
		type = "number",
		value = 2.5,
		min = 0.5,
		max = 15.0,
		step = 0.5,
		desc = "Attack markers for allied forces will be removed after this many seconds. You might want them to expire quicker than for your own forces.",
		noHotkey = true,
	},
	markersAllyRadius = {
		name = "Attack marker spacing (elmo) - ally",
		type = "number",
		value = 1500,
		min = 250,
		max = 3000,
		step = 250,
		desc = "If allied forces are attacked within this distance of an existing attack marker, suppress the alert. You might want them spaced out further than attacks on your forces.",
		noHotkey = true,
	},
	voiceSelfVolume = {
		name = "Attack alert volume - self",
		type = "number",
		value = 1.0,
		min = 0.0,
		max = 1.0,
		step = 0.05,
		desc = "Volume for attack alerts for your forces",
		noHotkey = true,
	},
	voiceSelfCooldown = {
		name = "Attack alert cooldown (s) - self",
		type = "number",
		value = 6,
		min = 1,
		max = 30,
		step = 1,
		desc = "Attack alerts for your forces will not be sounded if the last alert sound was within this period",
		noHotkey = true,
	},
	voiceAllyVolume = {
		name = "Attack alert volume - ally",
		type = "number",
		value = 1.0,
		min = 0.0,
		max = 1.0,
		step = 0.05,
		desc = "Volume for attack alerts for your forces",
		noHotkey = true,
	},
	voiceAllyCooldown = {
		name = "Attack alert cooldown (s) - ally",
		type = "number",
		value = 6,
		min = 1,
		max = 30,
		step = 1,
		desc = "Attack alerts for your forces will not be sounded if the last alert sound was within this period",
		noHotkey = true,
	},
}

local voiceFilenameSelfBaseAttacked = "sounds/alerts/SelfBaseAttacked.ogg"
local voiceFilenameSelfUnitAttacked = "sounds/alerts/SelfUnitAttacked.ogg"
local voiceFilenameAllyBaseAttacked = "sounds/alerts/AllyBaseAttacked.ogg"
local voiceFilenameAllyUnitAttacked = "sounds/alerts/AllyUnitAttacked.ogg"
local voiceFilenames = { -- [bSelf][isBuilding]
	[false]={
		[false]=voiceFilenameAllyUnitAttacked,
		[true]=voiceFilenameAllyBaseAttacked,
	},
	[true]={
		[false]=voiceFilenameSelfUnitAttacked,
		[true]=voiceFilenameSelfBaseAttacked,
	},
}

local osClock = os.clock
local spPlaySoundFile = Spring.PlaySoundFile  -- (filename, volume, posx, posy, posz, speedx, speedy, speedz, channel)
local spMarkerAddPoint = Spring.MarkerAddPoint  -- (x, y, z, text, localonly)
local spMarkerErasePosition = Spring.MarkerErasePosition  -- (x, y, z)  Sadly you can't keep handles of markers
local spGetUnitPosition = Spring.GetUnitPosition
local spAreTeamsAllied = Spring.AreTeamsAllied
local spGetGameFrame  = Spring.GetGameFrame
local spGetSpectatingState = Spring.GetSpectatingState
local spEcho = Spring.Echo
local spSetLastMessagePosition = Spring.SetLastMessagePosition

local warningDelay = 30 * 5  --in frames
local lastWarning = 0  --in frames
local localTeamID = Spring.GetLocalTeamID()

local under_attack_translation
local function languageChanged()
	under_attack_translation = WG.Translate("interface", "unit_under_attack")
end

local function dist2(x1, z1, x2, z2)
  -- Distance squared between two points
  -- Coords are X and Z because Spring uses Y as the vertical axis, and we only care about the planar position.
  local dx, dz = x2-x1, z2-z1
  return dx*dx + dz*dz
end

function TextAlert(unitDefID, x, y, z)
	local currentFrame = spGetGameFrame()
	if (lastWarning+warningDelay > currentFrame) then return end
	lastWarning = currentFrame
	spEcho("game_message: " .. Spring.Utilities.GetHumanName(UnitDefs[unitDefID])  .. " " .. under_attack_translation)
	spSetLastMessagePosition(x, y, z)
end

local attackMarkers = {}
local tLastVoice = 0
local markerOffset = 2  -- Offset the marker Y coord by this much to avoid potential conflict with user-placed markers

local data = {  -- [bSelf]
	[false]={
		voiceCooldown=options.voiceAllyCooldown.value,
		voiceVolume=options.voiceAllyVolume.value,
		markerD2=options.markersAllyRadius.value*options.markersAllyRadius.value,
		markerPrefix={[false]="Allied Unit", [true]="Allied Base"},
		markerDuration=options.markersAllyDuration.value,
	},
	[true]={
		voiceCooldown=options.voiceSelfCooldown.value,
		voiceVolume=options.voiceSelfVolume.value,
		markerD2=options.markersSelfRadius.value*options.markersSelfRadius.value,
		markerPrefix={[false]="Unit", [true]="Base"},
		markerDuration=options.markersSelfDuration.value,
	},
}
function UpdateOptions()
	data = {  -- [bSelf]
		[false]={
			voiceCooldown=options.voiceAllyCooldown.value,
			voiceVolume=options.voiceAllyVolume.value,
			markerD2=options.markersAllyRadius.value*options.markersAllyRadius.value,
			markerPrefix={[false]="Allied Unit", [true]="Allied Base"},
			markerDuration=options.markersAllyDuration.value,
		},
		[true]={
			voiceCooldown=options.voiceSelfCooldown.value,
			voiceVolume=options.voiceSelfVolume.value,
			markerD2=options.markersSelfRadius.value*options.markersSelfRadius.value,
			markerPrefix={[false]="Unit", [true]="Base"},
			markerDuration=options.markersSelfDuration.value,
		},
	}
end


function MarkerAlert(unitTeam, unitDefID, x, y, z)
	-- Assumptions for calling this function:
	--    - Unit is allied to the player
	--    - Unit is not on-screen for the player
	y = y + markerOffset
	local t = osClock()
	local isBuilding = UnitDefs[unitDefID].isBuilding
	local bSelf = (unitTeam == localTeamID)

	-- Do voice alert if appropriate
	if t > (tLastVoice + data[bSelf].voiceCooldown) then
		spPlaySoundFile(voiceFilenames[bSelf][isBuilding], data[bSelf].voiceVolume, nil, nil, nil, nil, nil, nil, "userinterface")
		spSetLastMessagePosition(x, y, z)
		tLastVoice = t
	end

	-- Check if the new marker would be too close to any existing markers
	for i=1,#attackMarkers do
		local marker = attackMarkers[i]
		local d2 = dist2(x, z, marker.x, marker.z)
		if d2 < data[bSelf].markerD2 then return end
	end
	-- Place a marker
	attackMarkers[#attackMarkers+1] = {x=x, y=y, z=z, tDeath=t+data[bSelf].markerDuration}
	spMarkerAddPoint(x, y, z, data[bSelf].markerPrefix[isBuilding] .. " attacked", true)
	spSetLastMessagePosition(x, y, z)
end


function CleanMarkers()
	local t = osClock()
	for i=#attackMarkers,1,-1 do
		local m = attackMarkers[i]
		if m.tDeath < t then
			spMarkerErasePosition(m.x, m.y, m.z)
			table.remove(attackMarkers, i)
		end
	end
end


local UPDATE_PERIOD = 0.25  -- Check to remove markers every 250ms
local timeframetimer = 0.0
function widget:Update(dt)
	timeframetimer = timeframetimer + dt
	if (timeframetimer > UPDATE_PERIOD) then
		UpdateOptions()  -- Couldn't find a suitable call-in for options being changed
		CleanMarkers()
		timeframetimer = 0
	end
end


function widget:UnitDamaged(unitID, unitDefID, unitTeam, damage, paralyzer, weaponID, attackerID, attackerDefID, attackerTeam)
	if damage <= 0 then return end
	--spEcho("game_message: Processing damage event! " .. tostring(unitID) .. ", " .. tostring(unitDefID) .. ", " .. tostring(unitTeam) .. ", " .. tostring(attackerTeam) .. ", " .. tostring(attackerID));
	if Spring.IsUnitInView(unitID) then return end
	if not spAreTeamsAllied(localTeamID, unitTeam) then return end
	if not unitTeam then return end  -- I don't even?
	if not unitDefID then return end  -- Haven't encountered this being nil but I'm not risking it
	if attackerTeam and spAreTeamsAllied(unitTeam, attackerTeam) then return end  -- Get a lot of nil for attacker stats, probably from things out of vision/radar.
	local x,y,z = spGetUnitPosition(unitID)
	if not (x and y and z) then return end
	TextAlert(unitDefID, x, y, z)
	MarkerAlert(unitTeam, unitDefID, x, y, z)
end


function widget:Initialize()
	if spGetSpectatingState() then
		widgetHandler:RemoveWidget()
	end

	WG.InitializeTranslation(languageChanged, GetInfo().name)
end


function widget:Shutdown()
	WG.ShutdownTranslation(GetInfo().name)
end


--changing teams, rejoin, becoming spec etc
function widget:PlayerChanged(playerID)
	if spGetSpectatingState() then
		--Spring.Echo("<Attack Warning>: Spectator mode. Widget removed.")
		widgetHandler:RemoveWidget()
	end
	localTeamID = Spring.GetLocalTeamID()
end