#!/usr/bin/env ruby

# simulateur de prets immobiliers multiples

require 'optparse'

apport = 0
pret = 160000
pretlen= 25
taux = 5.00
pretzero = 27000
pretzerolen = 8
pret1pc = 9600
pret1pclen = 10

OptionParser.new { |o|
	o.on('-p pret', Integer) { |p| pret = p }
	o.on('-d duree', Integer) { |d| pretlen = d }
	o.on('-a apport', Integer) { |a| apport = a }
	o.on('-t taux', Float) { |t| taux = t }
	o.on('--p0 p0', Integer) { |p0| pretzero = p0 }
	o.on('--p0len p0len', Integer) { |p0len| pretzerolen = p0len }
	o.on('--p1 p1pc', Integer) { |p1pc| pret1pc = p1pc }
	o.on('--p1len p1pclen', Integer) { |p1pclen| pret1pclen = p1pclen }
}.parse!

class Pret
	attr_accessor :du, :taux, :interets
	def initialize(du, taux)
		@du, @taux = du, taux.to_f
		@interets = 0
	end

	def mensualite(mens=0)
		int = @du * @taux / 100 / 12
		@interets += int
		@du += int
		if mens > @du
			@du = 0
		else
			@du -= mens
			mens
		end
	end

	def tpm
		1.00 + @taux.to_f / 100 / 12
	end

	def sumtpm(n)
		tpm == 1.0 ? n.to_f : ((tpm ** n) - 1) / (tpm - 1)
	end

	def calc_mens(duree)
		@du * (tpm ** duree) / sumtpm(duree)
	end

	# duree tot = t3
	# 0 -> t3: paye retval sur differents prets
	# 0 -> t1: paye m1 de moins ( = mens pret 1)
	# 0 -> t2: paye m2 de moins ( = mens pret 2)
	def calc_mens_cx(t3, t1, m1, t2, m2)
		t1, t2, m1, m2 = t2, t1, m2, m1 if t1 > t2
		m1 += m2
		p = @du * (tpm ** t3) + m1.to_f * (tpm ** (t3-t1)) * sumtpm(t1) + m2.to_f * (tpm ** (t3-t2)) * sumtpm(t2-t1)
		q = (tpm ** (t3-t1)) * sumtpm(t1) + (tpm ** (t3-t2)) * sumtpm(t2-t1) + sumtpm(t3-t2)
		p / q
	end
end

p0 = Pret.new(pretzero, 0)
p1 = Pret.new(pret1pc, 1.5)
p  = Pret.new(pret - p0.du - p1.du - apport, taux)

m0 = p0.calc_mens(pretzerolen*12)
m1 = p1.calc_mens(pret1pclen*12)

mb = p.calc_mens_cx(pretlen*12, pretzerolen*12, m0, pret1pclen*12, m1)

puts "mens: t0 %.2f*#{pretzerolen}a  1%% %.2f*#{pret1pclen}a  pret (#{p.du}) %.2f*#{pretlen}a" % [m0, m1, mb-m0-m1]
puts "total => %.2f  (= %.2f / 3)" % [mb, mb*3]

(pretlen * 12).times { |i|
	mens = mb
	mens -= p0.mensualite(m0)
	mens -= p1.mensualite(m1)
	puts "#{i/12} du %.2f  int %.2f" % [p.du, p.interets] if $VERBOSE and i % 12 == 0
	if p.mensualite(mens) == 0
		puts "fini a #{i/12}a#{i%12}"
		break
	end
}

puts "reste du: %.2fe - interets: 1%% %.2f, pret %.2f (%.2f)" % [p.du, p1.interets, p.interets, p1.interets+p.interets]