var http = use('http')
var json = use('json')

var registry = {}
var server_fd = null
var port = 9000

function handle_request(req) {
  var result = null
  var _try = null

  if (req.method == "GET" && req.path == "/discover") {
    result = discover()
    http.respond(req._conn, 200, {"content-type": "application/json"},
      json.encode(result))
    return
  }

  if (req.method == "POST" && req.path == "/probe") {
    _try = function() {
      result = handle_probe(req)
    } disruption {
      result = {ok: false, error: "probe failed"}
    }
    _try()
    http.respond(req._conn, 200, {"content-type": "application/json"},
      json.encode(result))
    return
  }

  if (req.method == "POST" && req.path == "/snapshot") {
    _try = function() {
      result = handle_snapshot(req)
    } disruption {
      result = {ok: false, error: "snapshot failed"}
    }
    _try()
    http.respond(req._conn, 200, {"content-type": "application/json"},
      json.encode(result))
    return
  }

  http.respond(req._conn, 404, {"content-type": "application/json"},
    json.encode({ok: false, error: "not found"}))
}

function discover() {
  var targets = {}
  var target_keys = array(registry)
  var i = 0
  while (i < length(target_keys)) {
    targets[target_keys[i]] = array(registry[target_keys[i]])
    i = i + 1
  }
  return {ok: true, targets: targets}
}

function handle_probe(req) {
  var body = json.decode(req.body)
  var target = body.target
  var name = body.name
  var args = body.args

  if (target == null || name == null) {
    return {ok: false, error: "missing target or name"}
  }

  var target_probes = registry[target]
  if (target_probes == null) {
    return {ok: false, error: "unknown target: " + target}
  }

  var probe_fn = target_probes[name]
  if (probe_fn == null) {
    return {ok: false, error: "unknown probe: " + target + "/" + name}
  }

  if (args == null) args = {}
  var result = probe_fn(args)
  return {ok: true, result: result}
}

function handle_snapshot(req) {
  var body = json.decode(req.body)
  var probes = body.probes
  if (probes == null) {
    return {ok: false, error: "missing probes array"}
  }

  var results = {}
  var i = 0
  var p = null
  var target_probes = null
  var probe_fn = null
  var key = null
  while (i < length(probes)) {
    p = probes[i]
    key = p.target + "/" + p.name
    target_probes = registry[p.target]
    if (target_probes != null) {
      probe_fn = target_probes[p.name]
      if (probe_fn != null) {
        results[key] = probe_fn(p.args != null ? p.args : {})
      }
    }
    i = i + 1
  }
  return {ok: true, results: results}
}

function start_server() {
  server_fd = http.serve(port)
  http.on_request(server_fd, handle_request)
}

function register(target, probes) {
  registry[target] = probes
  if (server_fd == null) start_server()
}

return {
  register: register,
  port: port
}