tiny-forge/internal/docker/build.go

package docker

import (
	"archive/tar"
	"context"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"

	"github.com/moby/moby/client"
)

// BuildImage builds a Docker image from a directory containing a Dockerfile.
// The directory is packaged as a tar archive and sent to the Docker daemon.
// The tag parameter is the image name:tag to apply (e.g., "dw-site-myapp:latest").
func (c *Client) BuildImage(ctx context.Context, contextDir, tag string) error {
	// Create tar archive of the build context.
	pr, pw := io.Pipe()

	go func() {
		tw := tar.NewWriter(pw)
		err := filepath.Walk(contextDir, func(path string, info os.FileInfo, err error) error {
			if err != nil {
				return err
			}

			relPath, err := filepath.Rel(contextDir, path)
			if err != nil {
				return fmt.Errorf("rel path: %w", err)
			}
			relPath = filepath.ToSlash(relPath)

			if relPath == "." {
				return nil
			}

			header, err := tar.FileInfoHeader(info, "")
			if err != nil {
				return fmt.Errorf("tar header for %s: %w", relPath, err)
			}
			header.Name = relPath

			if err := tw.WriteHeader(header); err != nil {
				return fmt.Errorf("write tar header for %s: %w", relPath, err)
			}

			if info.IsDir() {
				return nil
			}

			file, err := os.Open(path)
			if err != nil {
				return fmt.Errorf("open %s: %w", path, err)
			}
			defer file.Close()

			if _, err := io.Copy(tw, file); err != nil {
				return fmt.Errorf("copy %s to tar: %w", relPath, err)
			}

			return nil
		})

		if closeErr := tw.Close(); closeErr != nil && err == nil {
			err = closeErr
		}
		pw.CloseWithError(err)
	}()

	resp, err := c.api.ImageBuild(ctx, pr, client.ImageBuildOptions{
		Dockerfile:  "Dockerfile",
		Tags:        []string{tag},
		Remove:      true,
		ForceRemove: true,
	})
	if err != nil {
		return fmt.Errorf("build image %s: %w", tag, err)
	}
	defer resp.Body.Close()

	// Read the build output to completion (required for the build to finish).
	output, err := io.ReadAll(resp.Body)
	if err != nil {
		return fmt.Errorf("read build output for %s: %w", tag, err)
	}

	// Check for error in build output.
	if strings.Contains(string(output), `"error"`) {
		return fmt.Errorf("build image %s: build errors in output", tag)
	}

	return nil
}