package util

// Set is a set data structure.
type Set map[interface{}]interface{}

// SetFromStrings creates a Set containing the strings from the given slice
func SetFromStrings(sl []string) Set {
	set := make(Set, len(sl))
	for _, item := range sl {
		set.Add(item)
	}
	return set
}

// Hashable is the interface used by set to get the hash code of a value.
// If this isn't given, then the value of the item being added to the set
// itself is used as the comparison value.
type Hashable interface {
	Hashcode() interface{}
}

// hashcode returns the hashcode used for set elements.
func hashcode(v interface{}) interface{} {
	if h, ok := v.(Hashable); ok {
		return h.Hashcode()
	}

	return v
}

// Add adds an item to the set
func (s Set) Add(v interface{}) {
	s[hashcode(v)] = v
}

// Delete removes an item from the set.
func (s Set) Delete(v interface{}) {
	delete(s, hashcode(v))
}

// Includes returns true/false of whether a value is in the set.
func (s Set) Includes(v interface{}) bool {
	_, ok := s[hashcode(v)]
	return ok
}

// Intersection computes the set intersection with other.
func (s Set) Intersection(other Set) Set {
	result := make(Set)
	if s == nil || other == nil {
		return result
	}
	// Iteration over a smaller set has better performance.
	if other.Len() < s.Len() {
		s, other = other, s
	}
	for _, v := range s {
		if other.Includes(v) {
			result.Add(v)
		}
	}
	return result
}

// Difference returns a set with the elements that s has but
// other doesn't.
func (s Set) Difference(other Set) Set {
	result := make(Set)
	for k, v := range s {
		var ok bool
		if other != nil {
			_, ok = other[k]
		}
		if !ok {
			result.Add(v)
		}
	}

	return result
}

// Some tests whether at least one element in the array passes the test implemented by the provided function.
// It returns a Boolean value.
func (s Set) Some(cb func(interface{}) bool) bool {
	for _, v := range s {
		if cb(v) {
			return true
		}
	}
	return false
}

// Filter returns a set that contains the elements from the receiver
// where the given callback returns true.
func (s Set) Filter(cb func(interface{}) bool) Set {
	result := make(Set)

	for _, v := range s {
		if cb(v) {
			result.Add(v)
		}
	}

	return result
}

// Len is the number of items in the set.
func (s Set) Len() int {
	return len(s)
}

// List returns the list of set elements.
func (s Set) List() []interface{} {
	if s == nil {
		return nil
	}

	r := make([]interface{}, 0, len(s))
	for _, v := range s {
		r = append(r, v)
	}

	return r
}

// UnsafeListOfStrings dangerously casts list to a string
func (s Set) UnsafeListOfStrings() []string {
	if s == nil {
		return nil
	}

	r := make([]string, 0, len(s))
	for _, v := range s {
		r = append(r, v.(string))
	}

	return r
}

// Copy returns a shallow copy of the set.
func (s Set) Copy() Set {
	c := make(Set)
	for k, v := range s {
		c[k] = v
	}
	return c
}