// Package drive provides a thin wrapper around the Google Drive v3 API,
// used only to read modifiedTime for cache invalidation.
package drive

import (
	"context"
	"net/http"
	"time"

	"google.golang.org/api/drive/v3"
	"google.golang.org/api/option"
)

// Client wraps the Drive v3 API, scoped to read-only modifiedTime checks.
type Client struct {
	svc *drive.Service
}

// New builds a Client using a service-account credentials file.
// timeout applies to each Drive API call.
func New(ctx context.Context, credentialsPath string, timeout time.Duration) (*Client, error) {
	hc := &http.Client{Timeout: timeout}
	svc, err := drive.NewService(ctx,
		option.WithCredentialsFile(credentialsPath), //nolint:staticcheck
		option.WithScopes(drive.DriveReadonlyScope),
		option.WithHTTPClient(hc),
	)
	if err != nil {
		return nil, err
	}
	return &Client{svc: svc}, nil
}

// ModifiedTime returns the RFC3339 modifiedTime for the given Drive file ID.
// Returns ("", err) if the Drive API call fails.
func (c *Client) ModifiedTime(ctx context.Context, fileID string) (string, error) {
	meta, err := c.svc.Files.Get(fileID).
		Fields("modifiedTime").
		SupportsAllDrives(true).
		Context(ctx).
		Do()
	if err != nil {
		return "", err
	}
	return meta.ModifiedTime, nil
}