machines.go

/*
   Copyright 2014 CoreOS, Inc.

   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 api

import (
	"fmt"
	"net/http"
	"path"

	"github.com/coreos/fleet/client"
	"github.com/coreos/fleet/log"
	"github.com/coreos/fleet/machine"
	"github.com/coreos/fleet/schema"
)

func wireUpMachinesResource(mux *http.ServeMux, prefix string, cAPI client.API) {
	res := path.Join(prefix, "machines")
	mr := machinesResource{cAPI}
	mux.Handle(res, &mr)
}

type machinesResource struct {
	cAPI client.API
}

func (mr *machinesResource) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
	if req.Method != "GET" {
		sendError(rw, http.StatusBadRequest, fmt.Errorf("only HTTP GET supported against this resource"))
		return
	}

	token, err := findNextPageToken(req.URL)
	if err != nil {
		sendError(rw, http.StatusBadRequest, err)
		return
	}

	if token == nil {
		def := DefaultPageToken()
		token = &def
	}

	page, err := getMachinePage(mr.cAPI, *token)
	if err != nil {
		log.Errorf("Failed fetching page of Machines: %v", err)
		sendError(rw, http.StatusInternalServerError, nil)
		return
	}

	sendResponse(rw, http.StatusOK, page)
}

func getMachinePage(cAPI client.API, tok PageToken) (*schema.MachinePage, error) {
	all, err := cAPI.Machines()
	if err != nil {
		return nil, err
	}

	page := extractMachinePage(all, tok)
	return page, nil
}

func extractMachinePage(all []machine.MachineState, tok PageToken) *schema.MachinePage {
	total := len(all)

	startIndex := int((tok.Page - 1) * tok.Limit)
	stopIndex := int(tok.Page * tok.Limit)

	var items []machine.MachineState
	var next *PageToken

	if startIndex < total {
		if stopIndex > total {
			stopIndex = total
		} else {
			n := tok.Next()
			next = &n
		}

		items = all[startIndex:stopIndex]
	}

	return newMachinePage(items, next)
}

func newMachinePage(items []machine.MachineState, tok *PageToken) *schema.MachinePage {
	smp := schema.MachinePage{
		Machines: make([]*schema.Machine, 0, len(items)),
	}

	if tok != nil {
		smp.NextPageToken = tok.Encode()
	}

	for _, sm := range items {
		smp.Machines = append(smp.Machines, schema.MapMachineStateToSchema(&sm))
	}
	return &smp
}