package discovery

import (
	"fmt"
	"strings"
)

// ComposeLabels captures the four Compose-managed labels we need
// to drive a `docker compose pull`/`up -d` against the right stack.
type ComposeLabels struct {
	Project     string
	Service     string
	WorkingDir  string
	ConfigFiles []string
}

const (
	labelProject     = "com.docker.compose.project"
	labelService     = "com.docker.compose.service"
	labelWorkingDir  = "com.docker.compose.project.working_dir"
	labelConfigFiles = "com.docker.compose.project.config_files"
)

// ParseComposeLabels extracts the Compose labels we need. Returns an
// error naming the missing label if any required field is absent —
// in practice this should only happen if the container was not
// started by Compose.
func ParseComposeLabels(labels map[string]string) (ComposeLabels, error) {
	get := func(key string) (string, error) {
		v, ok := labels[key]
		if !ok || v == "" {
			return "", fmt.Errorf("missing required label: %s", key)
		}
		return v, nil
	}

	project, err := get(labelProject)
	if err != nil {
		return ComposeLabels{}, err
	}
	service, err := get(labelService)
	if err != nil {
		return ComposeLabels{}, err
	}
	workingDir, err := get(labelWorkingDir)
	if err != nil {
		return ComposeLabels{}, err
	}
	configFilesRaw, err := get(labelConfigFiles)
	if err != nil {
		return ComposeLabels{}, err
	}

	files := strings.Split(configFilesRaw, ",")
	for i, f := range files {
		files[i] = strings.TrimSpace(f)
	}

	return ComposeLabels{
		Project:     project,
		Service:     service,
		WorkingDir:  workingDir,
		ConfigFiles: files,
	}, nil
}

// HasOptIn reports whether the labels include the opt-in marker with
// value "true" (exact, case-sensitive — anything else is excluded).
func HasOptIn(labels map[string]string, key string) bool {
	return labels[key] == "true"
}