package util

import(
        "github.com/pierrec/lz4"
        "github.com/long/taskpubsub/logger"
       )



//  1. oldstring element is not in new  : abandon(delete)
//  2. new element is not in oldstring  : add(add)
func Difference(oldstring []string, newstring []string) map[string]string {
	var diff = make(map[string]string)

	// Loop two times, first to find oldstring strings not in newstring,
	// second loop to find newstring strings not in oldstring
	for i := 0; i < 2; i++ {
		for _, s1 := range oldstring {
			found := false
			for _, s2 := range newstring {
				if s1 == s2 {
					found = true
					break
				}
			}
			// String not found. We add it to return slice
			if !found && i == 0 {
				diff[s1] = "delete"
			}
			if !found && i != 0 {
				diff[s1] = "add"
			}
		}
		// Swap the slices, only if it was the first loop
		if i == 0 {
			oldstring, newstring = newstring, oldstring
		}
	}
	return diff
}

// UnCompress uncompress
func UnCompress(in []byte) ([]byte, error) {
    out := make([]byte, 10*len(in))
         n, err := lz4.UncompressBlock(in, out)
         if err != nil {
             logger.Error("uncompress error: ", err)
             return nil, err
         }
     out = out[:n] // uncompressed data
     return out, nil
}

// Compress compress
func Compress(in []byte) ([]byte, error) {
    out := make([]byte, len(in))
         ht := make([]int, 64<<10) // buffer for the compression table
         n, err := lz4.CompressBlock(in, out, ht)
         if err != nil {
             logger.Error("compress: ", err)
                 return nil, err
         }
     if n >= len(in) {
         logger.Error("image is not compressible")
     }
     out = out[:n] // compressed data
         return out, nil
}