Initial Functionality

The initial functionality works.  There's still a number of TODOs to
clean up, and some edge cases to work around, and some errors that could
be handled better.

pkg/client/types.go

@@ -0,0 +1,62 @@
+// Copyright 2017 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package prometheus provides bindings to the Prometheus HTTP API:
+// http://prometheus.io/docs/querying/api/
+package client
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+// ErrorType is the type of the API error.
+type ErrorType string
+
+const (
+	ErrBadData     ErrorType = "bad_data"
+	ErrTimeout               = "timeout"
+	ErrCanceled              = "canceled"
+	ErrExec                  = "execution"
+	ErrBadResponse           = "bad_response"
+)
+
+// Error is an error returned by the API.
+type Error struct {
+	Type ErrorType
+	Msg  string
+}
+
+func (e *Error) Error() string {
+	return fmt.Sprintf("%s: %s", e.Type, e.Msg)
+}
+
+// ResponseStatus is the type of response from the API: succeeded or error.
+type ResponseStatus string
+const (
+	ResponseSucceeded ResponseStatus = "succeeded"
+	ResponseError                    = "error"
+)
+
+// APIResponse represents the raw response returned by the API.
+type APIResponse struct {
+	// Status indicates whether this request was successful or whether it errored out.
+	Status ResponseStatus `json:"status"`
+	// Data contains the raw data response for this request.
+	Data json.RawMessage `json:"data"`
+
+	// ErrorType is the type of error, if this is an error response.
+	ErrorType ErrorType `json:"errorType"`
+	// Error is the error message, if this is an error response.
+	Error string `json:"error"`
+}