if not minetest.settings:get_bool("enable_damage") then
	minetest.log("warning", "[stamina] Stamina will not load if damage is disabled (enable_damage=false)")
	return
end

stamina = {}
local modname = minetest.get_current_modname()
local armor_mod = minetest.get_modpath("3d_armor") and minetest.global_exists("armor") and armor.def
local player_monoids_mod = minetest.get_modpath("player_monoids") and minetest.global_exists("player_monoids")

function stamina.log(level, message, ...)
	return minetest.log(level, ("[%s] %s"):format(modname, message:format(...)))
end

local function get_setting(key, default)
	local value = minetest.settings:get("stamina." .. key)
	local num_value = tonumber(value)
	if value and not num_value then
		stamina.log("warning", "Invalid value for setting %s: %q. Using default %q.", key, value, default)
	end
	return num_value or default
end

stamina.settings = {
	-- see settingtypes.txt for descriptions
	eat_particles = minetest.settings:get_bool("stamina.eat_particles", true),
	sprint = minetest.settings:get_bool("stamina.sprint", true),
	sprint_particles = minetest.settings:get_bool("stamina.sprint_particles", true),
	sprint_lvl = get_setting("sprint_lvl", 6),
	sprint_speed = get_setting("sprint_speed", 0.8),
	sprint_jump = get_setting("sprint_jump", 0.1),
	sprint_with_fast = minetest.settings:get_bool("stamina.sprint_with_fast", false),
	tick = get_setting("tick", 800),
	tick_min = get_setting("tick_min", 4),
	health_tick = get_setting("health_tick", 4),
	move_tick = get_setting("move_tick", 0.5),
	poison_tick = get_setting("poison_tick", 2.0),
	exhaust_dig = get_setting("exhaust_dig", 3),
	exhaust_place = get_setting("exhaust_place", 1),
	exhaust_move = get_setting("exhaust_move", 1.5),
	exhaust_jump = get_setting("exhaust_jump", 5),
	exhaust_craft = get_setting("exhaust_craft", 20),
	exhaust_punch = get_setting("exhaust_punch", 40),
	exhaust_sprint = get_setting("exhaust_sprint", 28),
	exhaust_lvl = get_setting("exhaust_lvl", 160),
	heal = get_setting("heal", 1),
	heal_lvl = get_setting("heal_lvl", 5),
	starve = get_setting("starve", 1),
	starve_lvl = get_setting("starve_lvl", 3),
	visual_max = get_setting("visual_max", 20),
}
local settings = stamina.settings

local attribute = {
	saturation = "stamina:level",
	poisoned = "stamina:poisoned",
	exhaustion = "stamina:exhaustion",
}

local function is_player(player)
	return (
		minetest.is_player(player) and
		not player.is_fake_player
	)
end

local function set_player_attribute(player, key, value)
	if player.get_meta then
		if value == nil then
			player:get_meta():set_string(key, "")
		else
			player:get_meta():set_string(key, tostring(value))
		end
	else
		player:set_attribute(key, value)
	end
end

local function get_player_attribute(player, key)
	if player.get_meta then
		return player:get_meta():get_string(key)
	else
		return player:get_attribute(key)
	end
end

local hud_ids_by_player_name = {}

local function get_hud_id(player)
	return hud_ids_by_player_name[player:get_player_name()]
end

local function set_hud_id(player, hud_id)
	hud_ids_by_player_name[player:get_player_name()] = hud_id
end

--- SATURATION API ---
function stamina.get_saturation(player)
	return tonumber(get_player_attribute(player, attribute.saturation))
end

function stamina.set_saturation(player, level)
	set_player_attribute(player, attribute.saturation, level)
	player:hud_change(
		get_hud_id(player),
		"number",
		math.min(settings.visual_max, level)
	)
end

stamina.registered_on_update_saturations = {}
function stamina.register_on_update_saturation(fun)
	table.insert(stamina.registered_on_update_saturations, fun)
end

function stamina.update_saturation(player, level)
	for _, callback in ipairs(stamina.registered_on_update_saturations) do
		local result = callback(player, level)
		if result then
			return result
		end
	end

	local old = stamina.get_saturation(player)

	if level == old then  -- To suppress HUD update
		return
	end

	-- players without interact priv cannot eat
	if old < settings.heal_lvl and not minetest.check_player_privs(player, {interact=true}) then
		return
	end

	stamina.set_saturation(player, level)
end

function stamina.change_saturation(player, change)
	if not is_player(player) or not change or change == 0 then
		return false
	end
	local level = stamina.get_saturation(player) + change
	level = math.max(level, 0)
	level = math.min(level, settings.visual_max)
	stamina.update_saturation(player, level)
	return true
end

stamina.change = stamina.change_saturation -- for backwards compatablity
--- END SATURATION API ---
--- POISON API ---
function stamina.is_poisoned(player)
	return get_player_attribute(player, attribute.poisoned) == "yes"
end

function stamina.set_poisoned(player, poisoned)
	local hud_id = get_hud_id(player)
	if poisoned then
		player:hud_change(hud_id, "text", "stamina_hud_poison.png")
		set_player_attribute(player, attribute.poisoned, "yes")
	else
		player:hud_change(hud_id, "text", "stamina_hud_fg.png")
		set_player_attribute(player, attribute.poisoned, "no")
	end
end

local function poison_tick(player_name, ticks, interval, elapsed)
	local player = minetest.get_player_by_name(player_name)
	if not player or not stamina.is_poisoned(player) then
		return
	elseif elapsed > ticks then
		stamina.set_poisoned(player, false)
	else
		local hp = player:get_hp() - 1
		if hp > 0 then
			player:set_hp(hp)
		end
		minetest.after(interval, poison_tick, player_name, ticks, interval, elapsed + 1)
	end
end

stamina.registered_on_poisons = {}
function stamina.register_on_poison(fun)
	table.insert(stamina.registered_on_poisons, fun)
end

function stamina.poison(player, ticks, interval)
	for _, fun in ipairs(stamina.registered_on_poisons) do
		local rv = fun(player, ticks, interval)
		if rv == true then
			return
		end
	end
	if not is_player(player) then
		return
	end
	stamina.set_poisoned(player, true)
	local player_name = player:get_player_name()
	poison_tick(player_name, ticks, interval, 0)
end
--- END POISON API ---
--- EXHAUSTION API ---
stamina.exhaustion_reasons = {
	craft = "craft",
	dig = "dig",
	heal = "heal",
	jump = "jump",
	move = "move",
	place = "place",
	punch = "punch",
	sprint = "sprint",
}

function stamina.get_exhaustion(player)
	return tonumber(get_player_attribute(player, attribute.exhaustion))
end

function stamina.set_exhaustion(player, exhaustion)
	set_player_attribute(player, attribute.exhaustion, exhaustion)
end

stamina.registered_on_exhaust_players = {}
function stamina.register_on_exhaust_player(fun)
	table.insert(stamina.registered_on_exhaust_players, fun)
end

function stamina.exhaust_player(player, change, cause)
	for _, callback in ipairs(stamina.registered_on_exhaust_players) do
		local result = callback(player, change, cause)
		if result then
			return result
		end
	end

	if not is_player(player) then
		return
	end

	local exhaustion = stamina.get_exhaustion(player) or 0

	exhaustion = exhaustion + change

	if exhaustion >= settings.exhaust_lvl then
		exhaustion = exhaustion - settings.exhaust_lvl
		stamina.change(player, -1)
	end

	stamina.set_exhaustion(player, exhaustion)
end
--- END EXHAUSTION API ---
--- SPRINTING API ---
stamina.registered_on_sprintings = {}
function stamina.register_on_sprinting(fun)
	table.insert(stamina.registered_on_sprintings, fun)
end

function stamina.set_sprinting(player, sprinting)
	for _, fun in ipairs(stamina.registered_on_sprintings) do
		local rv = fun(player, sprinting)
		if rv == true then
			return
		end
	end

	if player_monoids_mod then
		if sprinting then
			player_monoids.speed:add_change(player, 1 + settings.sprint_speed, "stamina:physics")
			player_monoids.jump:add_change(player, 1 + settings.sprint_jump, "stamina:physics")
		else
			player_monoids.speed:del_change(player, "stamina:physics")
			player_monoids.jump:del_change(player, "stamina:physics")
		end
	else
		local def
		if armor_mod then
			-- Get player physics from 3d_armor mod
			local name = player:get_player_name()
			def = {
				speed=armor.def[name].speed,
				jump=armor.def[name].jump,
				gravity=armor.def[name].gravity
			}
		else
			def = {
				speed=1,
				jump=1,
				gravity=1
			}
		end

		if sprinting then
			def.speed = def.speed + settings.sprint_speed
			def.jump = def.jump + settings.sprint_jump
		end

		player:set_physics_override(def)
	end

	if settings.sprint_particles and sprinting then
		local pos = player:getpos()
		local node = minetest.get_node({x = pos.x, y = pos.y - 1, z = pos.z})
		local def = minetest.registered_nodes[node.name] or {}
		local drawtype = def.drawtype
		if drawtype ~= "airlike" and drawtype ~= "liquid" and drawtype ~= "flowingliquid" then
			minetest.add_particlespawner({
				amount = 5,
				time = 0.01,
				minpos = {x = pos.x - 0.25, y = pos.y + 0.1, z = pos.z - 0.25},
				maxpos = {x = pos.x + 0.25, y = pos.y + 0.1, z = pos.z + 0.25},
				minvel = {x = -0.5, y = 1, z = -0.5},
				maxvel = {x = 0.5, y = 2, z = 0.5},
				minacc = {x = 0, y = -5, z = 0},
				maxacc = {x = 0, y = -12, z = 0},
				minexptime = 0.25,
				maxexptime = 0.5,
				minsize = 0.5,
				maxsize = 1.0,
				vertical = false,
				collisiondetection = false,
				texture = "default_dirt.png",
			})
		end
	end
end
--- END SPRINTING API ---

-- Time based stamina functions
local function move_tick()
	for _,player in ipairs(minetest.get_connected_players()) do
		local controls = player:get_player_control()
		local is_moving = controls.up or controls.down or controls.left or controls.right
		local velocity = player:get_player_velocity()
		velocity.y = 0
		local horizontal_speed = vector.length(velocity)
		local has_velocity = horizontal_speed > 0.05

		if controls.jump then
			stamina.exhaust_player(player, settings.exhaust_jump, stamina.exhaustion_reasons.jump)
		elseif is_moving and has_velocity then
			stamina.exhaust_player(player, settings.exhaust_move, stamina.exhaustion_reasons.move)
		end

		if settings.sprint then
			local can_sprint = (
				controls.aux1 and
				not player:get_attach() and
				(settings.sprint_with_fast or not minetest.check_player_privs(player, {fast = true})) and
				stamina.get_saturation(player) > settings.sprint_lvl
			)

			if can_sprint then
				stamina.set_sprinting(player, true)
				if is_moving and has_velocity then
					stamina.exhaust_player(player, settings.exhaust_sprint, stamina.exhaustion_reasons.sprint)
				end
			else
				stamina.set_sprinting(player, false)
			end
		end
	end
end

local function stamina_tick()
	-- lower saturation by 1 point after settings.tick second(s)
	for _,player in ipairs(minetest.get_connected_players()) do
		local saturation = stamina.get_saturation(player)
		if saturation > settings.tick_min then
			stamina.update_saturation(player, saturation - 1)
		end
	end
end

local function health_tick()
	-- heal or damage player, depending on saturation
	for _,player in ipairs(minetest.get_connected_players()) do
		local air = player:get_breath() or 0
		local hp = player:get_hp()
		local saturation = stamina.get_saturation(player)

		-- don't heal if dead, drowning, or poisoned
		local should_heal = (
			saturation >= settings.heal_lvl and
			saturation >= hp and
			hp > 0 and
			air > 0
			and not stamina.is_poisoned(player)
		)
		-- or damage player by 1 hp if saturation is < 2 (of 30)
		local is_starving = (
			saturation < settings.starve_lvl and
			hp > 0
		)

		if should_heal then
			player:set_hp(hp + settings.heal)
			stamina.exhaust_player(player, settings.exhaust_lvl, stamina.exhaustion_reasons.heal)
		elseif is_starving then
			player:set_hp(hp - settings.starve)
		end
	end
end

local stamina_timer = 0
local health_timer = 0
local action_timer = 0

local function stamina_globaltimer(dtime)
	stamina_timer = stamina_timer + dtime
	health_timer = health_timer + dtime
	action_timer = action_timer + dtime

	if action_timer > settings.move_tick then
		action_timer = 0
		move_tick()
	end

	if stamina_timer > settings.tick then
		stamina_timer = 0
		stamina_tick()
	end

	if health_timer > settings.health_tick then
		health_timer = 0
		health_tick()
	end
end

-- override minetest.do_item_eat() so we can redirect hp_change to stamina
stamina.core_item_eat = minetest.do_item_eat
function minetest.do_item_eat(hp_change, replace_with_item, itemstack, player, pointed_thing)
	for _, callback in ipairs(minetest.registered_on_item_eats) do
		local result = callback(hp_change, replace_with_item, itemstack, player, pointed_thing)
		if result then
			return result
		end
	end

	if not is_player(player) or not itemstack then
		return itemstack
	end

	local level = stamina.get_saturation(player) or 0
	if level >= settings.visual_max then
		-- don't eat if player is full
		return itemstack
	end

	local itemname = itemstack:get_name()
	if replace_with_item then
		stamina.log("action", "%s eats %s for %s stamina, replace with %s",
			player:get_player_name(), itemname, hp_change, replace_with_item)
	else
		stamina.log("action", "%s eats %s for %s stamina",
			player:get_player_name(), itemname, hp_change)
	end
	minetest.sound_play("stamina_eat", {to_player = player:get_player_name(), gain = 0.7})

	if hp_change > 0 then
		stamina.change_saturation(player, hp_change)
		stamina.set_exhaustion(player, 0)
	else
		-- assume hp_change < 0.
		stamina.poison(player, -hp_change, settings.poison_tick)
	end

	if settings.eat_particles then
		-- particle effect when eating
		local pos = player:getpos()
		pos.y = pos.y + 1.5 -- mouth level
		local texture  = minetest.registered_items[itemname].inventory_image
		local dir = player:get_look_dir()

		minetest.add_particlespawner({
			amount = 5,
			time = 0.1,
			minpos = pos,
			maxpos = pos,
			minvel = {x = dir.x - 1, y = dir.y, z = dir.z - 1},
			maxvel = {x = dir.x + 1, y = dir.y, z = dir.z + 1},
			minacc = {x = 0, y = -5, z = 0},
			maxacc = {x = 0, y = -9, z = 0},
			minexptime = 1,
			maxexptime = 1,
			minsize = 1,
			maxsize = 2,
			texture = texture,
		})
	end

	itemstack:take_item()

	if replace_with_item then
		if itemstack:is_empty() then
			itemstack:add_item(replace_with_item)
		else
			local inv = player:get_inventory()
			if inv:room_for_item("main", {name=replace_with_item}) then
				inv:add_item("main", replace_with_item)
			else
				local pos = player:getpos()
				pos.y = math.floor(pos.y - 1.0)
				minetest.add_item(pos, replace_with_item)
			end
		end
	end

	return itemstack
end

minetest.register_on_joinplayer(function(player)
	local level = stamina.get_saturation(player) or settings.visual_max
	local id = player:hud_add({
		name = "stamina",
		hud_elem_type = "statbar",
		position = {x = 0.5, y = 1},
		size = {x = 24, y = 24},
		text = "stamina_hud_fg.png",
		number = level,
		alignment = {x = -1, y = -1},
		offset = {x = -266, y = -110},
		max = 0,
	})
	stamina.set_saturation(player, level)
	set_hud_id(player, id)
	-- reset poisoned
	stamina.set_poisoned(player, false)
	-- remove legacy hud_id from player metadata
	set_player_attribute(player, "stamina:hud_id", nil)
end)

minetest.register_on_leaveplayer(function(player)
	set_hud_id(player, nil)
end)

minetest.register_globalstep(stamina_globaltimer)

minetest.register_on_placenode(function(pos, oldnode, player, ext)
	stamina.exhaust_player(player, settings.exhaust_place, stamina.exhaustion_reasons.place)
end)
minetest.register_on_dignode(function(pos, oldnode, player, ext)
	stamina.exhaust_player(player, settings.exhaust_dig, stamina.exhaustion_reasons.dig)
end)
minetest.register_on_craft(function(itemstack, player, old_craft_grid, craft_inv)
	stamina.exhaust_player(player, settings.exhaust_craft, stamina.exhaustion_reasons.craft)
end)
minetest.register_on_punchplayer(function(player, hitter, time_from_last_punch, tool_capabilities, dir, damage)
	stamina.exhaust_player(hitter, settings.exhaust_punch, stamina.exhaustion_reasons.punch)
end)
minetest.register_on_respawnplayer(function(player)
	stamina.update_saturation(player, settings.visual_max)
end)