initial working read only state

auth.go

@@ -0,0 +1,66 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/url"
+	"os"
+	"os/exec"
+	"strings"
+	"time"
+)
+
+type commandRunner func(context.Context, string, ...string) ([]byte, error)
+
+func resolveToken(endpoint string) (string, error) {
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	return resolveTokenWith(ctx, endpoint, os.Getenv, runCommand)
+}
+
+func resolveTokenWith(ctx context.Context, endpoint string, getenv func(string) string, run commandRunner) (string, error) {
+	if token := firstNonEmpty(
+		getenv("GH_TOKEN"),
+		getenv("GITHUB_TOKEN"),
+		getenv("GH_ENTERPRISE_TOKEN"),
+		getenv("GITHUB_ENTERPRISE_TOKEN"),
+	); token != "" {
+		return token, nil
+	}
+
+	host, err := githubHost(endpoint)
+	if err != nil {
+		return "", err
+	}
+	output, err := run(ctx, "gh", "auth", "token", "--hostname", host)
+	if err != nil {
+		if errors.Is(err, exec.ErrNotFound) {
+			return "", errors.New("no environment token found and gh is not installed; install gh and run `gh auth login`, or set GH_TOKEN")
+		}
+		if ctx.Err() != nil {
+			return "", fmt.Errorf("read authentication from gh: %w", ctx.Err())
+		}
+		return "", fmt.Errorf("no usable authentication for %s; run `gh auth login --hostname %s`, or set GH_TOKEN: %w", host, host, err)
+	}
+	token := strings.TrimSpace(string(output))
+	if token == "" {
+		return "", fmt.Errorf("gh returned an empty token for %s; run `gh auth login --hostname %s`", host, host)
+	}
+	return token, nil
+}
+
+func githubHost(endpoint string) (string, error) {
+	parsed, err := url.Parse(endpoint)
+	if err != nil || parsed.Scheme == "" || parsed.Hostname() == "" {
+		return "", fmt.Errorf("invalid GitHub GraphQL endpoint %q", endpoint)
+	}
+	if parsed.Hostname() == "api.github.com" {
+		return "github.com", nil
+	}
+	return parsed.Hostname(), nil
+}
+
+func runCommand(ctx context.Context, name string, args ...string) ([]byte, error) {
+	return exec.CommandContext(ctx, name, args...).Output()
+}