schemas/graph/cosmo.go

package graph

import (
	"fmt"
	"os"
	"os/exec"
	"path/filepath"

	"gopkg.in/yaml.v3"

	"gitlab.com/unboundsoftware/schemas/graph/model"
)

// GenerateCosmoRouterConfig generates a Cosmo Router execution config from subgraphs
// using the official wgc CLI tool via npx
func GenerateCosmoRouterConfig(subGraphs []*model.SubGraph) (string, error) {
	if len(subGraphs) == 0 {
		return "", fmt.Errorf("no subgraphs provided")
	}

	// Create a temporary directory for composition
	tmpDir, err := os.MkdirTemp("", "cosmo-compose-*")
	if err != nil {
		return "", fmt.Errorf("create temp dir: %w", err)
	}
	defer os.RemoveAll(tmpDir)

	// Write each subgraph SDL to a file
	type SubgraphConfig struct {
		Name         string                 `yaml:"name"`
		RoutingURL   string                 `yaml:"routing_url,omitempty"`
		Schema       map[string]string      `yaml:"schema"`
		Subscription map[string]interface{} `yaml:"subscription,omitempty"`
	}

	type InputConfig struct {
		Version   int              `yaml:"version"`
		Subgraphs []SubgraphConfig `yaml:"subgraphs"`
	}

	inputConfig := InputConfig{
		Version:   1,
		Subgraphs: make([]SubgraphConfig, 0, len(subGraphs)),
	}

	for _, sg := range subGraphs {
		// Write SDL to a temp file
		schemaFile := filepath.Join(tmpDir, fmt.Sprintf("%s.graphql", sg.Service))
		if err := os.WriteFile(schemaFile, []byte(sg.Sdl), 0o644); err != nil {
			return "", fmt.Errorf("write schema file for %s: %w", sg.Service, err)
		}

		subgraphCfg := SubgraphConfig{
			Name: sg.Service,
			Schema: map[string]string{
				"file": schemaFile,
			},
		}

		if sg.URL != nil {
			subgraphCfg.RoutingURL = *sg.URL
		}

		if sg.WsURL != nil {
			subgraphCfg.Subscription = map[string]interface{}{
				"url":                   *sg.WsURL,
				"protocol":              "ws",
				"websocket_subprotocol": "graphql-ws",
			}
		}

		inputConfig.Subgraphs = append(inputConfig.Subgraphs, subgraphCfg)
	}

	// Write input config YAML
	inputFile := filepath.Join(tmpDir, "input.yaml")
	inputYAML, err := yaml.Marshal(inputConfig)
	if err != nil {
		return "", fmt.Errorf("marshal input config: %w", err)
	}
	if err := os.WriteFile(inputFile, inputYAML, 0o644); err != nil {
		return "", fmt.Errorf("write input config: %w", err)
	}

	// Execute wgc router compose
	// wgc is installed globally in the Docker image
	outputFile := filepath.Join(tmpDir, "config.json")
	cmd := exec.Command("wgc", "router", "compose",
		"--input", inputFile,
		"--out", outputFile,
		"--suppress-warnings",
	)

	output, err := cmd.CombinedOutput()
	if err != nil {
		return "", fmt.Errorf("wgc router compose failed: %w\nOutput: %s", err, string(output))
	}

	// Read the generated config
	configJSON, err := os.ReadFile(outputFile)
	if err != nil {
		return "", fmt.Errorf("read output config: %w", err)
	}

	return string(configJSON), nil
}