feat(cmd): Add --url flag to load a pattern URL

cmd/cmd.go

@@ -51,9 +51,16 @@ func run(cmd *cobra.Command, _ []string) error {
 	pat := pattern.Pattern{
 		Rule: rule,
 	}
-	if conf.File != "" {
+	format := pattern.Format(conf.FileFormat)
+	switch {
+	case conf.File != "":
 		var err error
-		if pat, err = pattern.UnmarshalFile(conf.File, pattern.Format(conf.FileFormat)); err != nil {
+		if pat, err = pattern.UnmarshalFile(conf.File, format); err != nil {
+			return err
+		}
+	case conf.URL != "":
+		var err error
+		if pat, err = pattern.UnmarshalURL(context.Background(), conf.URL, format); err != nil {
 			return err
 		}
 	}

docs/cli-of-life.md

@@ -10,12 +10,13 @@ cli-of-life [flags]
 
 ```
       --completion string    Output command-line completion code for the specified shell (one of: bash, zsh, fish, powershell)
-  -f, --file string          Loads a pattern file on startup
+  -f, --file string          Load a pattern file
       --file-format string   File format (one of: auto, rle, plaintext) (default "auto")
       --height uint          Board height. Will be ignored if a larger pattern is loaded. (default 600)
   -h, --help                 help for cli-of-life
       --play                 Play on startup
       --rule-string string   Rule string to use. This will be ignored if a pattern file is loaded. (default "B3/S23")
+      --url string           Load a pattern URL
       --width uint           Board width. Will be ignored if a larger pattern is loaded. (default 600)
 ```
 

internal/config/config.go

@@ -4,6 +4,7 @@ import "github.com/gabe565/cli-of-life/internal/pattern"
 
 type Config struct {
 	File       string
+	URL        string
 	FileFormat string
 	RuleString string
 	Play       bool

internal/config/flags.go

@@ -9,6 +9,7 @@ import (
 
 const (
 	FileFlag       = "file"
+	URLFlag        = "url"
 	FileFormatFlag = "file-format"
 	RuleStringFlag = "rule-string"
 	PlayFlag       = "play"
@@ -18,7 +19,8 @@ const (
 )
 
 func (c *Config) RegisterFlags(fs *pflag.FlagSet) {
-	fs.StringVarP(&c.File, FileFlag, "f", c.File, "Loads a pattern file on startup")
+	fs.StringVarP(&c.File, FileFlag, "f", c.File, "Load a pattern file")
+	fs.StringVar(&c.URL, URLFlag, c.URL, "Load a pattern URL")
 	fs.StringVar(&c.FileFormat, FileFormatFlag, c.FileFormat, "File format (one of: "+strings.Join(pattern.FormatStrings(), ", ")+")")
 	fs.StringVar(&c.RuleString, RuleStringFlag, c.RuleString, "Rule string to use. This will be ignored if a pattern file is loaded.")
 	fs.BoolVar(&c.Play, PlayFlag, c.Play, "Play on startup")

internal/pattern/pattern.go

@@ -2,10 +2,13 @@ package pattern
 
 import (
 	"bytes"
+	"context"
 	"errors"
 	"fmt"
 	"io"
+	"net/http"
 	"os"
+	"path"
 	"path/filepath"
 )
 
@@ -67,6 +70,42 @@ func UnmarshalFile(path string, format Format) (Pattern, error) {
 	}
 }
 
+var ErrResponse = errors.New("received an error response")
+
+func UnmarshalURL(ctx context.Context, url string, format Format) (Pattern, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return Pattern{}, err
+	}
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return Pattern{}, err
+	}
+	defer func() {
+		_, _ = io.Copy(io.Discard, resp.Body)
+		_ = resp.Body.Close()
+	}()
+
+	if resp.StatusCode != http.StatusOK {
+		return Pattern{}, ErrResponse
+	}
+
+	ext := path.Ext(url)
+	switch {
+	case format == FormatRLE, ext == ExtRLE:
+		return UnmarshalRLE(resp.Body)
+	case format == FormatPlaintext, ext == ExtPlaintext:
+		return UnmarshalPlaintext(resp.Body)
+	default:
+		pattern, err := Unmarshal(resp.Body)
+		if err != nil {
+			err = fmt.Errorf("%w: %s", err, url)
+		}
+		return pattern, err
+	}
+}
+
 func Unmarshal(r io.Reader) (Pattern, error) {
 	buf, err := io.ReadAll(r)
 	if err != nil {