package terraform

import (
	"sort"
)

// Semaphore is a wrapper around a channel to provide
// utility methods to clarify that we are treating the
// channel as a semaphore
type Semaphore chan struct{}

// NewSemaphore creates a semaphore that allows up
// to a given limit of simultaneous acquisitions
func NewSemaphore(n int) Semaphore {
	if n == 0 {
		panic("semaphore with limit 0")
	}
	ch := make(chan struct{}, n)
	return Semaphore(ch)
}

// Acquire is used to acquire an available slot.
// Blocks until available.
func (s Semaphore) Acquire() {
	s <- struct{}{}
}

// TryAcquire is used to do a non-blocking acquire.
// Returns a bool indicating success
func (s Semaphore) TryAcquire() bool {
	select {
	case s <- struct{}{}:
		return true
	default:
		return false
	}
}

// Release is used to return a slot. Acquire must
// be called as a pre-condition.
func (s Semaphore) Release() {
	select {
	case <-s:
	default:
		panic("release without an acquire")
	}
}

// strSliceContains checks if a given string is contained in a slice
// When anybody asks why Go needs generics, here you go.
func strSliceContains(haystack []string, needle string) bool {
	for _, s := range haystack {
		if s == needle {
			return true
		}
	}
	return false
}

// deduplicate a slice of strings
func uniqueStrings(s []string) []string {
	if len(s) < 2 {
		return s
	}

	sort.Strings(s)
	result := make([]string, 1, len(s))
	result[0] = s[0]
	for i := 1; i < len(s); i++ {
		if s[i] != result[len(result)-1] {
			result = append(result, s[i])
		}
	}
	return result
}