Harbor as HTTP server

The harbor server can be used as a HTTP server. You can use the function harbor.http.register to register HTTP handlers. Its parameters are are follow:

harbor.http.register(port=8080,method="GET",uri,handler)```
 where:

* `port` is the port where to receive incoming connections
* `method` is for the http method (or verb), one of: `"GET"`, `"PUT"`, `"POST"`, `"DELETE"`, `"OPTIONS"` and `"HEAD"`
* `uri` is used to match requested uri. Perl regular expressions are accepted.

* `handler` is the function used to process requests.

`handler` function has type:

(~protocol:string, ~data:string, ~headers:[(string*string)], string)->string))->unit


where:

* `protocol` is the HTTP protocol used by the client. Currently, one of `"HTTP/1.0"` or `"HTTP/1.1"`
* `data` is the data passed during a POST request
* `headers` is the list of HTTP headers sent by the client
* `string` is the (unparsed) uri requested by the client, e.g.: `"/foo?var=bar"`

The `handler` function returns HTTP and HTML data to be sent to the client,
for instance:
HTTP/1.1 200 OK
Content-type: text/html
Content-Length: 35

It works!

(`\r\n` should always be used for line return
in HTTP content)

For convenience, a `http_response` function is provided to 
create a HTTP response string. It has the following type:

(?protocol:string,?code:int,?headers:[(string*string)], ?data:string)->string


where:

* `protocol` is the HTTP protocol of the response (default `HTTP/1.1`)
* `code` is the response code (default `200`)
* `headers` is the response headers. It defaults to `[]` but an appropriate `"Content-Length"` header is added if not set by the user and `data` is not empty.
* `data` is an optional response data (default `""`)

Thess functions can be used to create your own HTTP interface. Some examples
are:

Redirect Icecast's pages
------------------------
Some source clients using the harbor may also request pages that
are served by an icecast server, for instance listeners statistics.
In this case, you can register the following handler:

Redirect all files other

# than /admin.* to icecast, # located at localhost:8000 def redirect_icecast(protocol,data,~headers,uri) = http_response( protocol=protocol, code=301, headers=[(“Location”,“http://localhost:8000#{uri}”)] ) end

# Register this handler at port 8005 # (provided harbor sources are also served # from this port). harbor.http.register(port=8005,method=“GET”, “^/(?!admin)”, redirect_icecast)


Another alternative, less recommended, is to
directly fetch the page's content from the Icecast server:

Serve all files other

# than /admin.* by fetching data # from Icecast, located at localhost:8000 def proxy_icecast(protocol,data,~headers,uri) = def f(x) = # Replace Host if string.capitalize(fst(x)) == “HOST” then “Host: localhost:8000” else “#{fst(x)}: #{snd(x)}” end end headers = list.map(f,headers) headers = string.concat(separator=“”,headers) request = “#{method} #{uri} #{protocol}
#{headers}” get_process_output(“echo #{quote(request)} |
nc localhost 8000”) end

# Register this handler at port 8005 # (provided harbor sources are also served # from this port). harbor.http.register(port=8005,method=“GET”, “^/(?!admin)”, proxy_icecast)


This method is not recommended because some servers may not
close the socket after serving a request, causing `nc` and
liquidsoap to hang.

Get metadata
------------
You can use harbor to register HTTP services to 
fecth/set the metadata of a source. For instance, 
using the [JSON export function](json.html) `json_of`:

meta = ref []

s = some source

Update current metadata

converted in UTF8

def update_meta(m) = m = metadata.export(m) recode = string.recode(out_enc=“UTF-8”) def f(x) = (recode(fst(x)),recode(snd(x))) end meta := list.map(f,m) end

Apply update_metadata

every time we see a new

metadata

s = on_metadata(update_meta,s)

Return the json content

of meta

def get_meta(protocol,data,~headers,uri) = m = !meta http_response( protocol=protocol, code=200, headers=[(“Content-Type”,“application/json; charset=utf-8”)], data=json_of(m) ) end

Register get_meta at port 700

harbor.http.register(port=7000,method=“GET”,“/getmeta”,get_meta)


Once the script is running, 
a GET/POST request for `/getmeta` at port `7000`
returns the following:

HTTP/1.1 200 OK Content-Type: application/json; charset=utf-8

{ “genre”: “Soul”, “album”: “The Complete Stax-Volt Singles: 1959-1968 (Disc 8)”, “artist”: “Astors”, “title”: “Daddy Didn’t Tell Me” }


Which can be used with AJAX-based backends to fetch the current 
metadata of source `s`

Set metadata
------------
Using `insert_metadata`, you can register a GET handler that
updates the metadata of a given source. For instance:

s = some source

x is of type ((metadata)->unit)*source # first part is a function used to update # metadata and second part is the source # whose metadata are updated x = insert_metadata(s)

Get the function

insert = fst(x)

# Redefine s as the new source s = snd(x)

The handler

def set_meta(protocol,data,~headers,uri) = # Split uri of the form request?foo=bar&… # into (request,[(“foo”,“bar”),..]) x = url.split(uri)

# Filter out unusual metadata meta = metadata.export(snd(x))

# Grab the returned message ret = if meta != [] then insert(meta) “OK!” else “No metadata to add!” end

# Return response http_response( protocol=protocol, code=200, headers=[(“Content-Type”,“text/html”)], data=" #{ret}

" ) end

# Register handler on port 700 harbor.http.register(port=7000,method=“GET”,“/setmeta”,set_meta) ```

Now, a request of the form http://server:7000/setmeta?title=foo will update the metadata of source s with [("title","foo")]. You can use this handler, for instance, in a custom HTML form.

Limitations

When using harbor’s HTTP server, please be warned that the server is not meant to be used under heavy load. Therefore, it should not be exposed to your users/listeners if you expect many of them. In this case, you should use it as a backend/middle-end and have some kind of caching between harbor and the final user. In particular, the harbor server is not meant to server big files because it loads their entire content in memory before sending them. However, the harbor HTTP server is fully equipped to serve any kind of CGI script.