responsibility-chain.go

package main

import (
	"errors"
	"fmt"
)

// Rule struct
type Rule struct {
	match  func(x, y int) bool
	action func(x, y int) int
}

func match(rules []Rule, x int, y int) (int, error) {
	for _, t := range rules {
		match := t.match
		action := t.action
		isMatch := match(x, y)
		if isMatch {
			return action(x, y), nil
		}
	}

	return 0, errors.New("unmatched")
}

func main() {
	rules := []Rule{
		{
			func(x, y int) bool {
				if x < y {
					return true
				}
				return false
			},
			func(x, y int) int { return y - x },
		},
		{
			func(x, y int) bool {
				if x > y {
					return true
				}
				return false
			},
			func(x, y int) int { return y - x },
		},
		{
			func(x, y int) bool {
				if x == y {
					return true
				}
				return false
			},
			func(x, y int) int { return y - x },
		},
	}

	res, err := match(rules, 1, 2)

	if err != nil {
		fmt.Println(err)
	} else {
		fmt.Println(res)
	}

}