-module(prometheus_http).
-if(?OTP_RELEASE >= 27).
-define(MODULEDOC(Str), -moduledoc(Str)).
-define(DOC(Str), -doc(Str)).
-else.
-define(MODULEDOC(Str), -compile([])).
-define(DOC(Str), -compile([])).
-endif.

?MODULEDOC("HTTP instrumentation helpers").

-export([microseconds_duration_buckets/0, status_class/1]).

-export_type([status_code/0, status_class/0]).

-type status_code() :: pos_integer().
-type status_class() :: prometheus:label_value().

?DOC("""
Returns default microseconds buckets for measuring http requests duration.

```erlang
1> prometheus_http:microseconds_duration_buckets().
[10, 25, 50, 100, 250, 500,
 1000, 2500, 5000, 10000, 25000, 50000, 100000, 250000, 500000,
 1000000, 2500000, 5000000, 10000000]
```
""").
-spec microseconds_duration_buckets() -> prometheus_buckets:buckets().
microseconds_duration_buckets() ->
    [
        10,
        25,
        50,
        100,
        250,
        500,
        1000,
        2500,
        5000,
        10000,
        25000,
        50000,
        100000,
        250000,
        500000,
        1000000,
        2500000,
        5000000,
        10000000
    ].

?DOC("""
Returns status class for the http status code `SCode`.

```erlang
2> prometheus_http:status_class(202).
\"success\"

```

Raises `{invalid_value_error, SCode, Message}` error if `SCode` isn't a positive integer.
""").
-spec status_class(SCode) -> StatusClass when
    SCode :: status_code(),
    StatusClass :: status_class().
status_class(SCode) when
    is_integer(SCode) andalso
        SCode > 0 andalso
        SCode < 100
->
    "unknown";
status_class(SCode) when
    is_integer(SCode) andalso
        SCode > 0 andalso
        SCode < 200
->
    "informational";
status_class(SCode) when
    is_integer(SCode) andalso
        SCode > 0 andalso
        SCode < 300
->
    "success";
status_class(SCode) when
    is_integer(SCode) andalso
        SCode > 0 andalso
        SCode < 400
->
    "redirection";
status_class(SCode) when
    is_integer(SCode) andalso
        SCode > 0 andalso
        SCode < 500
->
    "client-error";
status_class(SCode) when
    is_integer(SCode) andalso
        SCode > 0 andalso
        SCode < 600
->
    "server-error";
status_class(SCode) when
    is_integer(SCode) andalso
        SCode > 0 andalso
        SCode >= 600
->
    "unknown";
status_class(C) ->
    erlang:error({invalid_value, C, "status code must be a positive integer"}).