package docker

import (
	"context"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/docker/docker/client"
)

// EngineInfo — runtime yang benar-benar terdeteksi (Docker ATAU Podman).
type EngineInfo struct {
	Name string // "docker" | "podman"
	Host string // unix:///… atau tcp://… (kosong = default/env DOCKER_HOST)
}

// candidate — endpoint yang dicoba berurutan saat deteksi.
type candidate struct {
	name string
	host string // kosong = biarkan env/DOCKER_HOST yang menentukan
}

// engineCandidates — urutan kandidat: override config → DOCKER_HOST →
// docker default → podman rootless (XDG) → podman rootful.
func engineCandidates(override string) []candidate {
	switch {
	case override != "":
		return []candidate{{name: nameFromHost(override), host: override}}
	case os.Getenv("DOCKER_HOST") != "":
		h := os.Getenv("DOCKER_HOST")
		return []candidate{{name: nameFromHost(h), host: ""}}
	}
	out := []candidate{{name: "docker", host: ""}}
	if xdg := os.Getenv("XDG_RUNTIME_DIR"); xdg != "" {
		out = append(out, candidate{
			name: "podman",
			host: "unix://" + filepath.Join(xdg, "podman", "podman.sock"),
		})
	}
	out = append(out, candidate{name: "podman", host: "unix:///run/podman/podman.sock"})
	return out
}

func nameFromHost(host string) string {
	if strings.Contains(host, "podman") {
		return "podman"
	}
	return "docker"
}

// Detect — client pertama yang ping-nya hidup, plus info runtime-nya.
// Podman mengekspos API kompatibel-Docker di podman.sock, jadi client yang
// sama dipakai untuk keduanya.
func Detect(override string) (*Client, EngineInfo, error) {
	connect := func(host string) (*Client, error) {
		opts := []client.Opt{client.WithAPIVersionNegotiation()}
		if host == "" {
			opts = append(opts, client.FromEnv)
		} else {
			opts = append(opts, client.WithHost(host))
		}
		cli, err := client.NewClientWithOpts(opts...)
		if err != nil {
			return nil, err
		}
		ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
		defer cancel()
		if _, err := cli.Ping(ctx); err != nil {
			_ = cli.Close()
			return nil, err
		}
		return &Client{cli: cli}, nil
	}
	return detectWith(engineCandidates(override), connect)
}

// detectWith — inti deteksi; connect dapat di-stub di unit test.
func detectWith(cands []candidate, connect func(host string) (*Client, error)) (*Client, EngineInfo, error) {
	var lastErr error
	for _, c := range cands {
		cl, err := connect(c.host)
		if err == nil {
			return cl, EngineInfo{Name: c.name, Host: c.host}, nil
		}
		lastErr = err
	}
	return nil, EngineInfo{}, fmt.Errorf("engine: tidak ada Docker/Podman yang merespons: %w", lastErr)
}

// New — pintasan auto-detect (kompatibilitas; info runtime diabaikan).
func New() (*Client, error) {
	cl, _, err := Detect("")
	return cl, err
}