package math

import luajit "git.sharkk.net/Sky/LuaJIT-to-Go"

// GetMathFunctions returns all math-related Go functions
func GetMathFunctions() map[string]luajit.GoFunction {
	return map[string]luajit.GoFunction{
		"math_factorial": func(s *luajit.State) int {
			if err := s.CheckMinArgs(1); err != nil {
				return s.PushError("math_factorial: %v", err)
			}

			n, err := s.SafeToNumber(1)
			if err != nil || n < 0 || n != float64(int(n)) {
				return s.PushError("math_factorial: argument must be a non-negative integer")
			}

			if n > 170 {
				return s.PushError("math_factorial: argument too large (max 170)")
			}

			result := 1.0
			for i := 2; i <= int(n); i++ {
				result *= float64(i)
			}

			s.PushNumber(result)
			return 1
		},

		"math_gcd": func(s *luajit.State) int {
			if err := s.CheckExactArgs(2); err != nil {
				return s.PushError("math_gcd: %v", err)
			}

			a, err := s.SafeToNumber(1)
			if err != nil || a != float64(int(a)) {
				return s.PushError("math_gcd: first argument must be an integer")
			}

			b, err := s.SafeToNumber(2)
			if err != nil || b != float64(int(b)) {
				return s.PushError("math_gcd: second argument must be an integer")
			}

			ia, ib := int(a), int(b)
			for ib != 0 {
				ia, ib = ib, ia%ib
			}

			s.PushNumber(float64(ia))
			return 1
		},

		"math_lcm": func(s *luajit.State) int {
			if err := s.CheckExactArgs(2); err != nil {
				return s.PushError("math_lcm: %v", err)
			}

			a, err := s.SafeToNumber(1)
			if err != nil || a != float64(int(a)) {
				return s.PushError("math_lcm: first argument must be an integer")
			}

			b, err := s.SafeToNumber(2)
			if err != nil || b != float64(int(b)) {
				return s.PushError("math_lcm: second argument must be an integer")
			}

			ia, ib := int(a), int(b)

			// Calculate GCD
			gcd := func(x, y int) int {
				for y != 0 {
					x, y = y, x%y
				}
				return x
			}

			result := ia * ib / gcd(ia, ib)
			s.PushNumber(float64(result))
			return 1
		},
	}
}