// Package compose runs docker compose the way a stack was deployed — which is not always
// simply "on this host". A stack deployed by an orchestrator running inside its own
// container records paths in that container's filesystem, so compose has to run in there;
// a stack deployed to another machine over tcp needs DOCKER_HOST pointed at it. Both the
// console and the scheduled updates it writes must invoke it identically, or a redeploy
// from one would not match the other's labels.
package compose

import (
	"context"
	"os"
	"os/exec"
	"path/filepath"
)

// Spec is everything needed to run compose for one stack.
type Spec struct {
	Project string   // -p
	Files   []string // -f, in order
	Via     string   // a container to run compose inside; "" is this host
	Remote  string   // a DOCKER_HOST; "" is this machine's Docker
	Tool    string   // "docker" or "podman"
}

// Cmd builds the command. args are compose's own, e.g. "pull" or "up", "-d".
func Cmd(ctx context.Context, s Spec, args ...string) *exec.Cmd {
	tool := s.Tool
	if tool == "" {
		tool = "docker"
	}
	base := []string{"compose", "-p", s.Project}
	for _, f := range s.Files {
		base = append(base, "-f", f)
	}
	if s.Via != "" {
		pre := []string{"exec"}
		if s.Remote != "" {
			pre = append(pre, "-e", "DOCKER_HOST="+s.Remote)
		}
		return exec.CommandContext(ctx, tool, append(append(append(pre, s.Via, "docker"), base...), args...)...)
	}
	cmd := exec.CommandContext(ctx, tool, append(base, args...)...)
	if len(s.Files) > 0 {
		cmd.Dir = filepath.Dir(s.Files[0])
	}
	if s.Remote != "" {
		cmd.Env = append(os.Environ(), "DOCKER_HOST="+s.Remote)
	}
	return cmd
}