Started working on urls package

cmd/cmsh/main.go

@@ -3,8 +3,9 @@ package main
 import (
 	"context"
 	"fmt"
-	"github.com/chzyer/readline"
 	"log"
+
+	"github.com/chzyer/readline"
 	"ucl.lmika.dev/repl"
 	"ucl.lmika.dev/ucl"
 	"ucl.lmika.dev/ucl/builtins"
@@ -27,6 +28,7 @@ func main() {
 		ucl.WithModule(builtins.Lists()),
 		ucl.WithModule(builtins.Time()),
 		ucl.WithModule(builtins.Fns()),
+		ucl.WithModule(builtins.URLs()),
 	)
 	ctx := context.Background()
 

ucl/builtins/urls.go

@@ -0,0 +1,67 @@
+package builtins
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+
+	"ucl.lmika.dev/ucl"
+)
+
+func URLs() ucl.Module {
+	return ucl.Module{
+		Name: "urls",
+		Builtins: map[string]ucl.BuiltinHandler{
+			"fetch": urlsFetch,
+		},
+	}
+}
+
+func urlsFetch(ctx context.Context, args ucl.CallArgs) (any, error) {
+	var url string
+
+	if err := args.Bind(&url); err != nil {
+		return nil, err
+	}
+
+	if strings.HasPrefix(url, "http:") || strings.HasPrefix(url, "https:") {
+		return urlFetchHTTP(ctx, url, args)
+	}
+
+	return nil, errors.New("unsupported URL scheme")
+}
+
+func urlFetchHTTP(ctx context.Context, url string, args ucl.CallArgs) (any, error) {
+	req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != 200 {
+		return nil, fmt.Errorf("non-200 status code: %v", resp.StatusCode)
+	}
+
+	// Do content negotiation
+	contentType := resp.Header.Get("Content-Type")
+	switch {
+	case strings.HasPrefix(contentType, "text/"):
+		bts, err := io.ReadAll(resp.Body)
+		if err != nil {
+			return nil, err
+		}
+
+		// TODO: honour encoding
+		return string(bts), nil
+	}
+
+	return nil, errors.New("unsupported content type: " + contentType)
+}

ucl/builtins/urls_test.go

@@ -0,0 +1,37 @@
+package builtins_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"ucl.lmika.dev/ucl"
+	"ucl.lmika.dev/ucl/builtins"
+)
+
+func TestURLs_Fetch_http(t *testing.T) {
+	tests := []struct {
+		desc    string
+		eval    string
+		want    any
+		wantErr bool
+	}{
+		{desc: "fetch 1", eval: `in (urls:fetch "https://www.example.com") "Example Domain"`, want: true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			inst := ucl.New(
+				ucl.WithModule(builtins.Strs()),
+				ucl.WithModule(builtins.URLs()),
+			)
+			res, err := inst.EvalString(context.Background(), tt.eval)
+			if tt.wantErr {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+				assert.Equal(t, tt.want, res)
+			}
+		})
+	}
+}