-- ToME - Tales of Maj'Eyal
-- Copyright (C) 2009, 2010, 2011, 2012 Nicolas Casalini
--
-- This program is free software: you can redistribute it and/or modify
-- it under the terms of the GNU General Public License as published by
-- the Free Software Foundation, either version 3 of the License, or
-- (at your option) any later version.
--
-- This program is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-- GNU General Public License for more details.
--
-- You should have received a copy of the GNU General Public License
-- along with this program.  If not, see <http://www.gnu.org/licenses/>.
--
-- Nicolas Casalini "DarkGod"
-- darkgod@te4.org

local _M = loadPrevious(...)

-- Scale a value up or down by a power
-- x = a numeric value
-- y_low = value to match at x_low
-- y_high = value to match at x_high
-- power = scaling factor (default 0.5)
-- add = amount to add the result (default 0)
-- shift = amount to add to the input value before computation (default 0)
function _M:combatScale(x, y_low, x_low, y_high, x_high, power, add, shift)
	power, add, shift = power or 0.5, add or 0, shift or 0
	local x_low_adj, x_high_adj = (x_low+shift)^power, (x_high+shift)^power
	local m = (y_high - y_low)/(x_high_adj - x_low_adj)
	local b = y_low - m*x_low_adj
	return m * (x + shift)^power + b + add
end

-- Scale a value up or down subject to a limit
-- x = a numeric value
-- limit = value approached as x increases
-- y_high = value to match at when x = x_high
-- y_low (optional) = value to match when x = x_low
--	returns (limit - add)*x/(x + halfpoint) + add (= add when x = 0 and limit when x = infinity), halfpoint, add
-- halfpoint and add are internally computed to match the desired high/low values
-- note that the progression low->high->limit must be monotone, consistently increasing or decreasing
function _M:combatLimit(x, limit, y_low, x_low, y_high, x_high)
	if y_low and x_low then
		local p = limit*(x_high-x_low)
		local m = x_high*y_high - x_low*y_low
		local halfpoint = (p-m)/(y_high - y_low)
		local add = (limit*(x_high*y_low-x_low*y_high) + y_high*y_low*(x_low-x_high))/(p-m)
		return (limit-add)*x/(x + halfpoint) + add
--		return (limit-add)*x/(x + halfpoint) + add, halfpoint, add
	else
		local add = 0
		local halfpoint = limit*x_high/(y_high-add)-x_high
		return (limit-add)*x/(x + halfpoint) + add
--		return (limit-add)*x/(x + halfpoint) + add, halfpoint, add
	end
end

-- Compute a diminishing returns value based on talent level that scales with a power
-- t = talent def table or a numeric value
-- low = value to match at talent level 1
-- high = value to match at talent level 5
-- power = scaling factor (default 0.5) or "log" for log10
-- add = amount to add the result (default 0)
-- shift = amount to add to the talent level before computation (default 0)
-- raw if true specifies use of raw talent level
function _M:combatTalentScale(t, low, high, power, add, shift, raw)
	local tl = type(t) == "table" and (raw and self:getTalentLevelRaw(t) or self:getTalentLevel(t)) or t
	power, add, shift = power or 0.5, add or 0, shift or 0
	local x_low, x_high = 1, 5 -- Implied talent levels to fit
	local x_low_adj, x_high_adj
	if power == "log" then
		x_low_adj, x_high_adj = math.log10(x_low+shift), math.log10(x_high+shift)
		tl = math.max(1, tl)
	else
		x_low_adj, x_high_adj = (x_low+shift)^power, (x_high+shift)^power
	end
	local m = (high - low)/(x_high_adj - x_low_adj)
	local b = low - m*x_low_adj
	if power == "log" then -- always >= 0
		return math.max(0, m * math.log10(tl + shift) + b + add)
--		return math.max(0, m * math.log10(tl + shift) + b + add), m, b
	else 
		return math.max(0, m * (tl + shift)^power + b + add)
--		return math.max(0, m * (tl + shift)^power + b + add), m, b
	end
end

-- Compute a diminishing returns value based on a stat value that scales with a power
-- stat == "str", "con",.... or a numeric value
-- low = value to match when stat = 10
-- high = value to match when stat = 100
-- power = scaling factor (default 0.5) or "log" for log10
-- add = amount to add the result (default 0)
-- shift = amount to add to the stat value before computation (default 0)
function _M:combatStatScale(stat, low, high, power, add, shift)
	stat = type(stat) == "string" and self:getStat(stat,nil,true) or stat
	power, add, shift = power or 0.5, add or 0, shift or 0
	local x_low, x_high = 10, 100 -- Implied stat values to match
	local x_low_adj, x_high_adj
	if power == "log" then
		x_low_adj, x_high_adj = math.log10(x_low+shift), math.log10(x_high+shift)
		stat = math.max(1, stat)
	else
		x_low_adj, x_high_adj = (x_low+shift)^power, (x_high+shift)^power
	end
	local m = (high - low)/(x_high_adj - x_low_adj)
	local b = low -m*x_low_adj
	if power == "log" then -- always >= 0
		return math.max(0, m * math.log10(stat + shift) + b + add)
--		return math.max(0, m * math.log10(stat + shift) + b + add), m, b
	else 
		return math.max(0, m * (stat + shift)^power + b + add)
--		return math.max(0, m * (stat + shift)^power + b + add), m, b
	end
end

-- Compute a diminishing returns value based on talent level that cannot go beyond a limit
-- t = talent def table or a numeric value
-- limit = value approached as talent levels increase
-- high = value at talent level 5
-- low = value at talent level 1 (optional)
-- raw if true specifies use of raw talent level
--	returns (limit - add)*TL/(TL + halfpoint) + add == add when TL = 0 and limit when TL = infinity
-- TL = talent level, halfpoint and add are internally computed to match the desired high/low values
-- note that the progression low->high->limit must be monotone, consistently increasing or decreasing
function _M:combatTalentLimit(t, limit, low, high, raw)
	local x_low, x_high = 1,5 -- Implied talent levels for low and high values respectively
	local tl = type(t) == "table" and (raw and self:getTalentLevelRaw(t) or self:getTalentLevel(t)) or t
	if low then
		local p = limit*(x_high-x_low)
		local m = x_high*high - x_low*low
		local halfpoint = (p-m)/(high - low)
		local add = (limit*(x_high*low-x_low*high) + high*low*(x_low-x_high))/(p-m)
		return (limit-add)*tl/(tl + halfpoint) + add
--		return (limit-add)*tl/(tl + halfpoint) + add, halfpoint, add
	else
		local add = 0
		local halfpoint = limit*x_high/(high-add)-x_high
		return (limit-add)*tl/(tl + halfpoint) + add
--		return (limit-add)*tl/(tl + halfpoint) + add, halfpoint, add
	end
end

-- Compute a diminishing returns value based on a stat value that cannot go beyond a limit
-- stat == "str", "con",.... or a numeric value
-- limit = value approached as talent levels increase
-- high = value to match when stat = 100
-- low = value to match when stat = 10 (optional)
--	returns (limit - add)*stat/(stat + halfpoint) + add == add when STAT = 0 and limit when stat = infinity
-- halfpoint and add are internally computed to match the desired high/low values
-- note that the progression low->high->limit must be monotone, consistently increasing or decreasing
function _M:combatStatLimit(stat, limit, low, high)
	local x_low, x_high = 10,100 -- Implied talent levels for low and high values respectively
	stat = type(stat) == "string" and self:getStat(stat,nil,true) or stat
	if low then
		local p = limit*(x_high-x_low)
		local m = x_high*high - x_low*low
		local halfpoint = (p-m)/(high - low)
		local add = (limit*(x_high*low-x_low*high) + high*low*(x_low-x_high))/(p-m)
		return (limit-add)*stat/(stat + halfpoint) + add
--		return (limit-add)*stat/(stat + halfpoint) + add, halfpoint, add
	else
		local add = 0
		local halfpoint = limit*x_high/(high-add)-x_high
		return (limit-add)*stat/(stat + halfpoint) + add
--		return (limit-add)*stat/(stat + halfpoint) + add, halfpoint, add
	end
end

return _M