HELP HTTP_CLIENT                HTTP(S) requests with headers and status

    uses http_client;

The client half of the HTTP story (LIB * HTTP_SERVER is the other):
a Pop-11 face over libcurl, so HTTPS, redirects, compression and
proxy environment variables come along for free.  One-time setup:

    $ tools/build-popcurl.sh        (needs libcurl dev headers)

http_get(URL) -> (BODY, STATUS)
    The simple case:
        http_get('https://example.com/data.json') -> (body, status);

http_post(URL, BODY, CTYPE) -> (BODY, STATUS)
    POST with a Content-Type, e.g.
        http_post(url, json_generate(obj), 'application/json')

http_request(METHOD, URL, BODY, HEADERS, TIMEOUT)
                            -> (BODY, RESPHDRS, STATUS)
    The general form.  METHOD any verb ('GET', 'PUT', 'DELETE'...);
    BODY '' for none; HEADERS a list of 'Name: value' strings;
    TIMEOUT in seconds or false.  RESPHDRS is a property of response
    headers with lowercased names (the final hop's headers when
    redirects were followed):

        http_request('GET', url, '', ['Authorization: Bearer ' <> tok], 30)
            -> (body, hdrs, status);
        hdrs('content-type') =>

http_client_version() -> STRING

STATUS is the HTTP status code (404 is a status, not an error).
Transport failures — DNS, connection refused, timeout — mishap with
libcurl's message.

Composes naturally with LIB * JSON:

    json_parse(http_get('https://api.example.com/x') -> status) -> obj;

Note: the shim keeps one response at a time (Poplog is single-
threaded); a request's body/headers are readable until the next
request.  For requests from inside an http_server handler, remember
the server is also single-threaded.

See also: LIB * HTTP_SERVER, LIB * JSON, LIB * CRYPTO (HMAC request
signing), tools/tests/test_http_client.p (client vs. the Pop-11
server, full circle).

--- pop/help/http_client