-- JSON DBC: Database connectivity over a JSON-RPC link.
-- Server-side code

-- Safe to reload live, but obviously only on the sdmon, and i don't think
-- there's a way to do that yet

require "jsonrpc/server"

db_serv = db_serv or {}

function db_serv.make_server(DB_Host, DB_Name, DB_User, DB_Pass, jsonrpc_login_magic)
  db_serv.mysql_env = assert(luasql.mysql())
  db_serv.mysql_conn = assert(db_serv.mysql_env:connect(DB_Name, DB_User, DB_Pass, DB_Host))
  local err
  db_serv.Server, err = JSONRPC.make_server(jsonrpc_port, 
    { -- request methods
      login=function(conn, userid, magic)
        if magic == jsonrpc_login_magic then
          conn.peername = userid..'@'..conn.tcp:GetPeerName()
          print('login: '..conn.peername)
          return "ok"
        end
        return "invalid magic"
      end,
      dbquery=function(conn, qstr, qid)
        if not conn.peername then return nil, "not authorized" end
        local nrows=0
        local cur,err = db_serv.mysql_conn:execute(qstr)
        if not cur then return cur,err end
        if type(cur) == "number" then return cur end
        local row,err = cur:fetch({}, "a")
        while row do
          nrows=nrows+1
          conn:notify('dbdata',qid,row,nrows)
          row,err = cur:fetch(row, "a")
        end
        return nrows
      end,
      checkpoint=function(conn) -- simple mechanism to ensure an end-to-end flush of write queues
        return 1
      end
    }, 
    { -- notify methods
      execute = function(conn, qstr)
        if not conn.peername then return end -- not logged in, but can't send response in this context
        local ok,err = db_serv.mysql_conn:execute(qstr)
        if not ok then 
          log.error("error in async query execution("..tostring(qstr).."): "..err) 
        end
      end
    },
    function(conn) -- connect callback
      --print('(connection established to '..conn.tcp:GetPeerName()..')')
    end,
    function(conn) -- disconnect callback
      -- neat, tcp is basically bunk at this point because the connection is closed!
      print(conn.peername..' disconnected')
      conn.peername = nil
    end)

  if not db_serv.Server then
    return nil, err
  end

  return db_serv.Server
end