add 'map' cli command to provide map information (#100)

* add 'map' cli command

- provides the following map information functions:
  - list all available maps in the global registry
  - display map metadata

- update docs with map command examples

* add list and info subcommands to map cli command

* rename map command list and info factory functions

* add --all flag to map info subcommand

* handle cmd.Help error

cli/commands/info.go

@@ -0,0 +1,78 @@
+package commands
+
+import (
+	"fmt"
+	"log"
+
+	"github.com/BattlesnakeOfficial/rules/maps"
+	"github.com/spf13/cobra"
+)
+
+type mapInfo struct {
+	All bool
+}
+
+func NewMapInfoCommand() *cobra.Command {
+	info := mapInfo{}
+	var infoCmd = &cobra.Command{
+		Use:   "info [flags] map_name [...map_name]",
+		Short: "Display metadata for given map(s)",
+		Long:  "Display metadata for given map(s)",
+		Run: func(cmd *cobra.Command, args []string) {
+			// handle --all flag first as there would be no args
+			if info.All {
+				mapList := maps.List()
+				for i, m := range mapList {
+					info.display(m)
+					if i < (len(mapList) - 1) {
+						fmt.Print("\n")
+					}
+				}
+				return
+			}
+
+			// display help when no map(s) provided via args
+			if len(args) < 1 {
+				err := cmd.Help()
+				if err != nil {
+					log.Fatal(err)
+				}
+				return
+			}
+
+			// display all maps via command args
+			for i, m := range args {
+				info.display(m)
+				if i < (len(args) - 1) {
+					fmt.Print("\n")
+				}
+			}
+
+		},
+	}
+
+	infoCmd.Flags().BoolVarP(&info.All, "all", "a", false, "Display information for all maps")
+
+	return infoCmd
+}
+
+func (m *mapInfo) display(id string) {
+	gameMap, err := maps.GetMap(id)
+	if err != nil {
+		log.Fatalf("Failed to load game map %#v: %v", id, err)
+	}
+	meta := gameMap.Meta()
+	fmt.Println("Name:", meta.Name)
+	fmt.Println("Author:", meta.Author)
+	fmt.Println("Description:", meta.Description)
+	fmt.Println("Version:", meta.Version)
+	fmt.Println("Min Players:", meta.MinPlayers)
+	fmt.Println("Max Players:", meta.MaxPlayers)
+	fmt.Print("Board Sizes (WxH):")
+	for i, s := range meta.BoardSizes {
+		fmt.Printf(" %dx%d", s.Width, s.Height)
+		if i == (len(meta.BoardSizes) - 1) {
+			fmt.Print("\n")
+		}
+	}
+}

cli/commands/list.go

@@ -0,0 +1,22 @@
+package commands
+
+import (
+	"fmt"
+
+	"github.com/BattlesnakeOfficial/rules/maps"
+	"github.com/spf13/cobra"
+)
+
+func NewMapListCommand() *cobra.Command {
+	var listCmd = &cobra.Command{
+		Use:   "list",
+		Short: "List available game maps",
+		Long:  "List available game maps",
+		Run: func(cmd *cobra.Command, args []string) {
+			for _, m := range maps.List() {
+				fmt.Println(m)
+			}
+		},
+	}
+	return listCmd
+}

cli/commands/map.go

@@ -0,0 +1,24 @@
+package commands
+
+import (
+	"log"
+
+	"github.com/spf13/cobra"
+)
+
+func NewMapCommand() *cobra.Command {
+
+	var mapCmd = &cobra.Command{
+		Use:   "map",
+		Short: "Display map information",
+		Long:  "Display map information",
+		Run: func(cmd *cobra.Command, args []string) {
+			err := cmd.Help()
+			if err != nil {
+				log.Fatal(err)
+			}
+		},
+	}
+
+	return mapCmd
+}

cli/commands/root.go

@@ -21,6 +21,12 @@ var rootCmd = &cobra.Command{
 func Execute() {
 	rootCmd.AddCommand(NewPlayCommand())
 
+	mapCommand := NewMapCommand()
+	mapCommand.AddCommand(NewMapListCommand())
+	mapCommand.AddCommand(NewMapInfoCommand())
+
+	rootCmd.AddCommand(mapCommand)
+
 	if err := rootCmd.Execute(); err != nil {
 		fmt.Println(err)
 		os.Exit(1)