package checks

import (
	"context"
	"encoding/json"
	"os/exec"
	"strings"
	"time"
)

// Container is one docker container's summary state.
type Container struct {
	Name   string
	Image  string
	State  string // running, exited, ...
	Status string // human string, e.g. "Up 3 hours"
}

// Containers runs `docker ps -a` and parses the line-delimited JSON output.
// Returns ([], "") when docker works but no containers exist.
func Containers(ctx context.Context) ([]Container, string) {
	ctx, cancel := context.WithTimeout(ctx, 8*time.Second)
	defer cancel()

	// docker emits one JSON object per line with --format json.
	out, err := exec.CommandContext(ctx, "docker", "ps", "-a", "--format", "json").Output()
	if err != nil {
		msg := err.Error()
		if ee, ok := err.(*exec.ExitError); ok && len(ee.Stderr) > 0 {
			msg = strings.TrimSpace(string(ee.Stderr))
		}
		return nil, msg
	}

	var list []Container
	for _, line := range strings.Split(strings.TrimSpace(string(out)), "\n") {
		if line == "" {
			continue
		}
		var row struct {
			Names  string `json:"Names"`
			Image  string `json:"Image"`
			State  string `json:"State"`
			Status string `json:"Status"`
		}
		if err := json.Unmarshal([]byte(line), &row); err != nil {
			continue
		}
		list = append(list, Container{
			Name:   row.Names,
			Image:  row.Image,
			State:  row.State,
			Status: row.Status,
		})
	}
	return list, ""
}