package runtime

import (
	"encoding/json"
	"fmt"
	"os/exec"
	"strings"
)

type Docker struct{}

func (d *Docker) Name() string { return "docker" }

type dockerContainer struct {
	Names   string `json:"Names"`
	Image   string `json:"Image"`
	Command string `json:"Command"`
	State   string `json:"State"`
}

func (d *Docker) ListRunning() ([]Container, error) {
	bin, err := exec.LookPath("docker")
	if err != nil {
		return nil, nil // docker not installed — not an error
	}

	out, err := exec.Command(bin, "ps", "--format", "json").Output()
	if err != nil {
		return nil, fmt.Errorf("docker ps: %w", err)
	}

	// Docker outputs one JSON object per line (not a JSON array)
	var containers []Container
	for _, line := range strings.Split(strings.TrimSpace(string(out)), "\n") {
		if line == "" {
			continue
		}
		var c dockerContainer
		if err := json.Unmarshal([]byte(line), &c); err != nil {
			continue
		}
		name := strings.TrimPrefix(c.Names, "/")
		if name == "" {
			continue
		}
		containers = append(containers, Container{
			Name:    name,
			Image:   c.Image,
			Command: c.Command,
			Runtime: "docker",
		})
	}
	return containers, nil
}

func (d *Docker) Exists(name string) (bool, error) {
	bin, err := exec.LookPath("docker")
	if err != nil {
		return false, nil
	}

	out, err := exec.Command(bin, "ps", "-a", "--format", "{{.Names}}").Output()
	if err != nil {
		return false, fmt.Errorf("docker ps -a: %w", err)
	}

	for _, line := range strings.Split(string(out), "\n") {
		if strings.TrimSpace(line) == name {
			return true, nil
		}
	}
	return false, nil
}