feature: flag.go diff

First pass at an implementation. Implement the calculation to determine whether a string is included in the partition or not, using crc32 to coerce the string to an evenly distributed uint32, and a modulo to turn it into a percentage. Implement a store to keep track of available flags and the level of the partition for each flag. Implement an API to retrieve, create, and modify these available flags.

     1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/flag.go	Mon Mar 16 22:45:58 2015 -0400
     1.3 @@ -0,0 +1,52 @@
     1.4 +package feature
     1.5 +
     1.6 +import (
     1.7 +	"hash/crc32"
     1.8 +	"log"
     1.9 +)
    1.10 +
    1.11 +type Flag struct {
    1.12 +	ID    string
    1.13 +	Limit int
    1.14 +}
    1.15 +
    1.16 +func (f Flag) calcOffset() int {
    1.17 +	return calcValue(f.ID)
    1.18 +}
    1.19 +
    1.20 +func (f Flag) Permit(candidate string) bool {
    1.21 +	if f.Limit >= 100 {
    1.22 +		return true
    1.23 +	}
    1.24 +	if f.Limit <= 0 {
    1.25 +		return false
    1.26 +	}
    1.27 +	return (calcValue(candidate)+f.calcOffset())%100 <= f.Limit
    1.28 +}
    1.29 +
    1.30 +type FlagSet struct {
    1.31 +	flags map[string]bool
    1.32 +}
    1.33 +
    1.34 +func (set FlagSet) Check(flag string) bool {
    1.35 +	pass, ok := set.flags[flag]
    1.36 +	if !ok {
    1.37 +		log.Println("Checked for flag that wasn't in response:", flag)
    1.38 +		pass = false
    1.39 +	}
    1.40 +	return pass
    1.41 +}
    1.42 +
    1.43 +func calcValue(in string) int {
    1.44 +	return int(crc32.ChecksumIEEE([]byte(in)) % 100)
    1.45 +}
    1.46 +
    1.47 +/*
    1.48 +
    1.49 +Client has one function:
    1.50 +
    1.51 +1. func (c Client) Load(in string) FlagSet -- loads the flagset with "in" as the parameter to gate on
    1.52 +
    1.53 +// TODO Have the client cache FlagSets in memory by the parameter being gated on; we can reuse FlagSets for a minute or two
    1.54 +
    1.55 +*/

feature

feature/flag.go