Nested arrays and ConvertTo-Json - json

Question

To use a REST API, I must pass a JSON object that looks like this:
{ "series" :
[{
"metric": "custom.powershell.gauge",
"points":[[1434684739, 1000]]
}
]
}
Note the nested array here. I cannot get to reproduce this. Here is my code:
[int][double]$unixtime=get-date ( (get-date).ToUniversalTime() ) -UFormat %s
$obj=#{}
$series=#{}
$array=#()
$points=#()
$value=get-random -Minimum 0 -Maximum 100
$series.add("metric","custom.powershell.gauge")
$points=#(#($unixtime, $value))
$series.add("points",$points)
$obj.Add("series",#($series))
$json=$obj | ConvertTo-Json -Depth 30 -Compress
$json
And here is the output:
{"series":[{"points":[1434685292,95],"metric":"custom.powershell.gauge"}]}
I've tried many things, I cannot get the 2 arrays to be nested, it always end up looking like a single array.
On the same note, came someone explain this please:
> $a=(1,2)
> $a
1
2
> $a | ConvertTo-Json
[
1,
2
]
> $b=($a,$a)
> $b
1
2
1
2
> $b | ConvertTo-Json
[
{
"value": [
1,
2
],
"Count": 2
},
{
"value": [
1,
2
],
"Count": 2
}
]
Where are these value and Count coming from?
Thanks for your help.

Answer 1

The explanation is that (1,2),(3,4) is an array of array, but Powershell split the first level with the pipe |, and you don't give a name for these arrays so the serializer supplies it. First have a try to this :
# First build your array of array
$z = (1,2),(3,4)
# convert it to JSON using the ,
,$z | ConvertTo-Json -Depth 5 -Compress
[psobject]#{"points"=$z} | ConvertTo-Json -Depth 5 -Compress
It gives the first step:
{"value":[[1,2],[3,4]],"Count":2}
{"points":[[1,2],[3,4]]}
Now the solution I propose :
# First build your array of array
$z = (1,2),(3,4)
# Then build a PSCustom object
$a = [pscustomobject]#{"series" = ,#{"metric"="custom.powershell.gauge"; "points"=$z}}
# At the end convert it to JSON
# don't forget the **Depth** parameter (use **Compress** to retreive one line like above)
$a | ConvertTo-Json -Depth 5
For me it gives something close to what you need:
{
"series": [
{
"points": [
[
1,
2
],
[
3,
4
]
],
"metric": "custom.powershell.gauge"
}
]
}

Answer 2

Late to the party, but I'd like to propose a more visually intuitive solution that's easy to expand (I, like others, am a visual learner so code blocks like the below help me understand things more easily):
[int][double]$unixtime = Get-Date ((Get-Date).ToUniversalTime()) -UFormat %s
$value = Get-Random -Minimum 0 -Maximum 100
$body = #{
'series' = #(
[Ordered]#{
'metric'='custom.powershell.gauge'
'points' = #(
,#($unixtime,$value)
)
}
)
}
ConvertTo-Json -InputObject $body -Depth 4
Outputs:
{
"series": [
{
"metric": "custom.powershell.gauge",
"points": [
[
1473698742,
96
]
]
}
]
}
-Depth 4 gets you the additional set of square brackets around your point values, and [Ordered] ensures that the hashtable is ordered as originally specified. Don't forget -Compress before sending, like others have said.

Answer 3

As JPBlanc suggested, creating a custom object worked. Below is my code:
[long]$value=Get-Random -Minimum 0 -Maximum 100
$points=,#($unixtime, $value)
$metricname="custom.powershell.gauge"
$obj = [pscustomobject]#{"series" = ,#{"metric" = $metricname; "points"=$points}}
$json=$obj | ConvertTo-Json -Depth 5 -Compress
Which outputs:
{"series":[{"points":[[1434810163,53]],"metric":"custom.powershell.gauge"}]}
Don't forget to specify a depth >2.
Thanks!