Centralize command-line parsing

command/base/command.go

@@ -0,0 +1,238 @@
+package base
+
+import (
+	"bufio"
+	"bytes"
+	"flag"
+	"fmt"
+	"io"
+	"strings"
+
+	"github.com/hashicorp/consul/api"
+	"github.com/mitchellh/cli"
+	text "github.com/tonnerre/golang-text"
+)
+
+// maxLineLength is the maximum width of any line.
+const maxLineLength int = 72
+
+// FlagSetFlags is an enum to define what flags are present in the
+// default FlagSet returned.
+type FlagSetFlags uint
+
+const (
+	FlagSetNone       FlagSetFlags = 1 << iota
+	FlagSetClientHTTP FlagSetFlags = 1 << iota
+	FlagSetServerHTTP FlagSetFlags = 1 << iota
+
+	FlagSetHTTP = FlagSetClientHTTP | FlagSetServerHTTP
+)
+
+type Command struct {
+	Ui    cli.Ui
+	Flags FlagSetFlags
+
+	flagSet *flag.FlagSet
+
+	// These are the options which correspond to the HTTP API options
+	httpAddr   stringValue
+	token      stringValue
+	datacenter stringValue
+	stale      boolValue
+}
+
+// HTTPClient returns a client with the parsed flags. It panics if the command
+// does not accept HTTP flags or if the flags have not been parsed.
+func (c *Command) HTTPClient() (*api.Client, error) {
+	if !c.hasClientHTTP() && !c.hasServerHTTP() {
+		panic("no http flags defined")
+	}
+	if !c.flagSet.Parsed() {
+		panic("flags have not been parsed")
+	}
+
+	config := api.DefaultConfig()
+	c.httpAddr.Merge(&config.Address)
+	c.token.Merge(&config.Token)
+	c.datacenter.Merge(&config.Datacenter)
+	return api.NewClient(config)
+}
+
+// httpFlagsClient is the list of flags that apply to HTTP connections.
+func (c *Command) httpFlagsClient(f *flag.FlagSet) *flag.FlagSet {
+	if f == nil {
+		f = flag.NewFlagSet("", flag.ContinueOnError)
+	}
+
+	f.Var(&c.httpAddr, "http-addr",
+		"Address and port to the Consul HTTP agent. The value can be an IP "+
+			"address or DNS address, but it must also include the port. This can "+
+			"also be specified via the CONSUL_HTTP_ADDR environment variable. The "+
+			"default value is 127.0.0.1:8500.")
+	f.Var(&c.token, "token",
+		"ACL token to use in the request. This can also be specified via the "+
+			"CONSUL_HTTP_TOKEN environment variable. If unspecified, the query will "+
+			"default to the token of the Consul agent at the HTTP address.")
+
+	return f
+}
+
+// httpFlagsServer is the list of flags that apply to HTTP connections.
+func (c *Command) httpFlagsServer(f *flag.FlagSet) *flag.FlagSet {
+	if f == nil {
+		f = flag.NewFlagSet("", flag.ContinueOnError)
+	}
+
+	f.Var(&c.datacenter, "datacenter",
+		"Name of the datacenter to query. If unspecified, this will default to "+
+			"the datacenter of the queried agent.")
+	f.Var(&c.stale, "stale",
+		"Permit any Consul server (non-leader) to respond to this request. This "+
+			"allows for lower latency and higher throughput, but can result in "+
+			"stale data. This option has no effect on non-read operations. The "+
+			"default value is false.")
+
+	return f
+}
+
+// NewFlagSet creates a new flag set for the given command. It automatically
+// generates help output and adds the appropriate API flags.
+func (c *Command) NewFlagSet(command cli.Command) *flag.FlagSet {
+	f := flag.NewFlagSet("", flag.ContinueOnError)
+	f.Usage = func() { c.Ui.Error(command.Help()) }
+
+	if c.hasClientHTTP() {
+		c.httpFlagsClient(f)
+	}
+
+	if c.hasServerHTTP() {
+		c.httpFlagsServer(f)
+	}
+
+	errR, errW := io.Pipe()
+	errScanner := bufio.NewScanner(errR)
+	go func() {
+		for errScanner.Scan() {
+			c.Ui.Error(errScanner.Text())
+		}
+	}()
+	f.SetOutput(errW)
+
+	c.flagSet = f
+
+	return f
+}
+
+// Parse is used to parse the underlying flag set.
+func (c *Command) Parse(args []string) error {
+	return c.flagSet.Parse(args)
+}
+
+// Help returns the help for this flagSet.
+func (c *Command) Help() string {
+	return c.helpFlagsFor(c.flagSet)
+}
+
+// hasClientHTTP returns true if this meta command contains client HTTP flags.
+func (c *Command) hasClientHTTP() bool {
+	return c.Flags&FlagSetClientHTTP != 0
+}
+
+// hasServerHTTP returns true if this meta command contains server HTTP flags.
+func (c *Command) hasServerHTTP() bool {
+	return c.Flags&FlagSetServerHTTP != 0
+}
+
+// helpFlagsFor visits all flags in the given flag set and prints formatted
+// help output. This function is sad because there's no "merging" of command
+// line flags. We explicitly pull out our "common" options into another section
+// by doing string comparisons :(.
+func (c *Command) helpFlagsFor(f *flag.FlagSet) string {
+	httpFlagsClient := c.httpFlagsClient(nil)
+	httpFlagsServer := c.httpFlagsServer(nil)
+
+	var out bytes.Buffer
+
+	firstHTTP := true
+	if c.hasClientHTTP() {
+		if firstHTTP {
+			printTitle(&out, "HTTP API Options")
+			firstHTTP = false
+		}
+		httpFlagsClient.VisitAll(func(f *flag.Flag) {
+			printFlag(&out, f)
+		})
+	}
+	if c.hasServerHTTP() {
+		if firstHTTP {
+			printTitle(&out, "HTTP API Options")
+			firstHTTP = false
+		}
+		httpFlagsServer.VisitAll(func(f *flag.Flag) {
+			printFlag(&out, f)
+		})
+	}
+
+	firstCommand := true
+	f.VisitAll(func(f *flag.Flag) {
+		// Skip HTTP flags as they will be grouped separately
+		if flagContains(httpFlagsClient, f) || flagContains(httpFlagsServer, f) {
+			return
+		}
+		if firstCommand {
+			printTitle(&out, "Command Options")
+			firstCommand = false
+		}
+		printFlag(&out, f)
+	})
+
+	return strings.TrimRight(out.String(), "\n")
+}
+
+// printTitle prints a consistently-formatted title to the given writer.
+func printTitle(w io.Writer, s string) {
+	fmt.Fprintf(w, "%s\n\n", s)
+}
+
+// printFlag prints a single flag to the given writer.
+func printFlag(w io.Writer, f *flag.Flag) {
+	example, _ := flag.UnquoteUsage(f)
+	if example != "" {
+		fmt.Fprintf(w, "  -%s=<%s>\n", f.Name, example)
+	} else {
+		fmt.Fprintf(w, "  -%s\n", f.Name)
+	}
+
+	indented := wrapAtLength(f.Usage, 5)
+	fmt.Fprintf(w, "%s\n\n", indented)
+}
+
+// flagContains returns true if the given flag is contained in the given flag
+// set or false otherwise.
+func flagContains(fs *flag.FlagSet, f *flag.Flag) bool {
+	var skip bool
+
+	fs.VisitAll(func(hf *flag.Flag) {
+		if skip {
+			return
+		}
+
+		if f.Name == hf.Name && f.Usage == hf.Usage {
+			skip = true
+			return
+		}
+	})
+
+	return skip
+}
+
+// wrapAtLength wraps the given text at the maxLineLength, taking into account
+// any provided left padding.
+func wrapAtLength(s string, pad int) string {
+	wrapped := text.Wrap(s, maxLineLength-pad)
+	lines := strings.Split(wrapped, "\n")
+	for i, line := range lines {
+		lines[i] = strings.Repeat(" ", pad) + line
+	}
+	return strings.Join(lines, "\n")
+}