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unpack.go
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unpack.go
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package library
import (
"errors"
"github.com/nytlabs/gojee" // jee
"github.com/nytlabs/streamtools/st/blocks" // blocks
"github.com/nytlabs/streamtools/st/util"
)
// specify those channels we're going to use to communicate with streamtools
type Unpack struct {
blocks.Block
queryrule chan chan interface{}
inrule chan interface{}
in chan interface{}
out chan interface{}
quit chan interface{}
}
// we need to build a simple factory so that streamtools can make new blocks of this kind
func NewUnpack() blocks.BlockInterface {
return &Unpack{}
}
// Setup is called once before running the block. We build up the channels and specify what kind of block this is.
func (b *Unpack) Setup() {
b.Kind = "Unpack"
b.Desc = "splits an array of objects from incoming data, emitting each element as a separate message"
b.in = b.InRoute("in")
b.inrule = b.InRoute("rule")
b.queryrule = b.QueryRoute("rule")
b.quit = b.Quit()
b.out = b.Broadcast()
}
// Run is the block's main loop. Here we listen on the different channels we set up.
func (b *Unpack) Run() {
var path string
var err error
var tree *jee.TokenTree
for {
select {
case ruleI := <-b.inrule:
// set a parameter of the block
rule, ok := ruleI.(map[string]interface{})
if !ok {
b.Error(errors.New("cannot assert rule to map"))
}
path, err = util.ParseString(rule, "Path")
if err != nil {
b.Error(err)
continue
}
token, err := jee.Lexer(path)
if err != nil {
b.Error(err)
continue
}
tree, err = jee.Parser(token)
if err != nil {
b.Error(err)
continue
}
case <-b.quit:
// quit the block
return
case msg := <-b.in:
if tree == nil {
continue
}
arrInterface, err := jee.Eval(tree, msg)
if err != nil {
b.Error(err)
continue
}
arr, ok := arrInterface.([]interface{})
if !ok {
b.Error(errors.New("cannot assert " + path + " to array"))
continue
}
for _, out := range arr {
b.out <- out
}
case c := <-b.queryrule:
// deal with a query request
out := map[string]interface{}{
"Path": path,
}
c <- out
}
}
}