add puppet integration code

Puppet can be used on the basis of the ffrank-mgmtgraph module.
There are three modes available:
* fetching catalogs from the master (--puppet agent)
* compiling a manifest from a local file (--puppet /path/to/file.pp)
* compiling a manifest from the cli (--puppet "<manifest>")

Catalogs from the master are currently never refreshed. We should
add some more code to re-run the parsing function at an interval
equal to Puppet's local 'runinterval' setting.

There is also still a distinct lack of tests.

Still, this fixes #8

puppet.go

@@ -0,0 +1,137 @@
+// Mgmt
+// Copyright (C) 2013-2016+ James Shubin and the project contributors
+// Written by James Shubin <james@shubin.ca> and the project contributors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package main
+
+import (
+	"bufio"
+	"io"
+	"log"
+	"os/exec"
+	"strconv"
+	"strings"
+)
+
+const (
+	PuppetYAMLBufferSize = 65535
+)
+
+func runPuppetCommand(cmd *exec.Cmd) ([]byte, error) {
+	if DEBUG {
+		log.Printf("Puppet: running command: %v", cmd)
+	}
+
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		log.Printf("Puppet: Error opening pipe to puppet command: %v", err)
+		return nil, err
+	}
+	stderr, err := cmd.StderrPipe()
+	if err != nil {
+		log.Printf("Puppet: Error opening error pipe to puppet command: %v", err)
+		return nil, err
+	}
+
+	if err := cmd.Start(); err != nil {
+		log.Printf("Puppet: Error starting puppet command: %v", err)
+		return nil, err
+	}
+
+	// XXX: the current implementation is likely prone to fail
+	// as soon as the YAML data overflows the buffer.
+	data := make([]byte, PuppetYAMLBufferSize)
+	var result []byte
+	for err == nil {
+		var count int
+		count, err = stdout.Read(data)
+		if err != nil && err != io.EOF {
+			log.Printf("Puppet: Error reading YAML data from puppet: %v", err)
+			return nil, err
+		}
+		// Slicing down to the number of actual bytes is important, the YAML parser
+		// will choke on an oversized slice. http://stackoverflow.com/a/33726617/3356612
+		result = append(result, data[0:count]...)
+	}
+	if DEBUG {
+		log.Printf("Puppet: read %v bytes of data from puppet", len(result))
+	}
+	for scanner := bufio.NewScanner(stderr); scanner.Scan(); {
+		log.Printf("Puppet: (output) %v", scanner.Text())
+	}
+	if err := cmd.Wait(); err != nil {
+		log.Printf("Puppet: Error: puppet command did not complete: %v", err)
+		return nil, err
+	}
+
+	return result, nil
+}
+
+func ParseConfigFromPuppet(puppetParam, puppetConf string) *GraphConfig {
+	var puppetConfArg string
+	if puppetConf != "" {
+		puppetConfArg = "--config=" + puppetConf
+	}
+
+	var cmd *exec.Cmd
+	if puppetParam == "agent" {
+		cmd = exec.Command("puppet", "mgmtgraph", "print", puppetConfArg)
+	} else if strings.HasSuffix(puppetParam, ".pp") {
+		cmd = exec.Command("puppet", "mgmtgraph", "print", puppetConfArg, "--manifest", puppetParam)
+	} else {
+		cmd = exec.Command("puppet", "mgmtgraph", "print", puppetConfArg, "--code", puppetParam)
+	}
+
+	log.Println("Puppet: launching translator")
+
+	var config GraphConfig
+	if data, err := runPuppetCommand(cmd); err != nil {
+		return nil
+	} else if err := config.Parse(data); err != nil {
+		log.Printf("Puppet: Error: Could not parse YAML output with Parse: %v", err)
+		return nil
+	}
+
+	return &config
+}
+
+func PuppetInterval(puppetConf string) int {
+	if DEBUG {
+		log.Printf("Puppet: determining graph refresh interval")
+	}
+	var cmd *exec.Cmd
+	if puppetConf != "" {
+		cmd = exec.Command("puppet", "config", "print", "runinterval", "--config", puppetConf)
+	} else {
+		cmd = exec.Command("puppet", "config", "print", "runinterval")
+	}
+
+	log.Println("Puppet: inspecting runinterval configuration")
+
+	interval := 1800
+	data, err := runPuppetCommand(cmd)
+	if err != nil {
+		log.Printf("Puppet: could not determine configured run interval (%v), using default of %v", err, interval)
+		return interval
+	}
+	result, err := strconv.ParseInt(strings.TrimSpace(string(data)), 10, 0)
+	if err != nil {
+		log.Printf("Puppet: error reading numeric runinterval value (%v), using default of %v", err, interval)
+		return interval
+	}
+
+	return int(result)
+}