package paths

import (
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strings"
)

type Layout struct {
	ConfigHome     string
	StateHome      string
	CacheHome      string
	RuntimeHome    string
	ConfigDir      string
	StateDir       string
	CacheDir       string
	RuntimeDir     string
	SocketPath     string
	DBPath         string
	DaemonLog      string
	VMsDir         string
	ImagesDir      string
	KernelsDir     string
	OCICacheDir    string
	SSHDir         string
	KnownHostsPath string
}

func Resolve() (Layout, error) {
	home, err := os.UserHomeDir()
	if err != nil {
		return Layout{}, err
	}
	configHome := getenvDefault("XDG_CONFIG_HOME", filepath.Join(home, ".config"))
	stateHome := getenvDefault("XDG_STATE_HOME", filepath.Join(home, ".local", "state"))
	cacheHome := getenvDefault("XDG_CACHE_HOME", filepath.Join(home, ".cache"))
	runtimeHome := os.Getenv("XDG_RUNTIME_DIR")
	if runtimeHome == "" {
		runtimeHome = filepath.Join(os.TempDir(), fmt.Sprintf("banger-runtime-%d", os.Getuid()))
	}

	layout := Layout{
		ConfigHome:  configHome,
		StateHome:   stateHome,
		CacheHome:   cacheHome,
		RuntimeHome: runtimeHome,
		ConfigDir:   filepath.Join(configHome, "banger"),
		StateDir:    filepath.Join(stateHome, "banger"),
		CacheDir:    filepath.Join(cacheHome, "banger"),
		RuntimeDir:  filepath.Join(runtimeHome, "banger"),
	}
	layout.SocketPath = filepath.Join(layout.RuntimeDir, "bangerd.sock")
	layout.DBPath = filepath.Join(layout.StateDir, "state.db")
	layout.DaemonLog = filepath.Join(layout.StateDir, "bangerd.log")
	layout.VMsDir = filepath.Join(layout.StateDir, "vms")
	layout.ImagesDir = filepath.Join(layout.StateDir, "images")
	layout.KernelsDir = filepath.Join(layout.StateDir, "kernels")
	layout.OCICacheDir = filepath.Join(layout.CacheDir, "oci")
	layout.SSHDir = filepath.Join(layout.StateDir, "ssh")
	layout.KnownHostsPath = filepath.Join(layout.SSHDir, "known_hosts")
	return layout, nil
}

func Ensure(layout Layout) error {
	for _, dir := range []string{layout.ConfigDir, layout.StateDir, layout.CacheDir, layout.RuntimeDir, layout.VMsDir, layout.ImagesDir, layout.KernelsDir, layout.OCICacheDir} {
		if err := os.MkdirAll(dir, 0o755); err != nil {
			return err
		}
	}
	// SSH material (private key, known_hosts) — 0700 like ~/.ssh so
	// strict SSH clients don't complain and no other host user can
	// read it. Empty SSHDir means the caller built a Layout by hand
	// (tests) and doesn't need the subdir; skip silently.
	if strings.TrimSpace(layout.SSHDir) != "" {
		if err := os.MkdirAll(layout.SSHDir, 0o700); err != nil {
			return err
		}
	}
	return nil
}

var executablePath = os.Executable

func BangerdPath() (string, error) {
	if env := os.Getenv("BANGER_DAEMON_BIN"); env != "" {
		return env, nil
	}
	exe, err := executablePath()
	if err != nil {
		return "", err
	}
	dir := filepath.Dir(exe)
	for _, candidate := range []string{
		filepath.Join(dir, "bangerd"),
		filepath.Join(dir, "bangerd.exe"),
	} {
		if _, err := os.Stat(candidate); err == nil {
			return candidate, nil
		}
	}
	return "", errors.New("bangerd binary not found next to banger; run `make build`")
}

func CompanionBinaryPath(name string) (string, error) {
	envNames := []string{
		"BANGER_" + strings.ToUpper(strings.NewReplacer("-", "_", ".", "_").Replace(name)) + "_BIN",
	}
	if trimmed, ok := strings.CutPrefix(name, "banger-"); ok {
		envNames = append(envNames, "BANGER_"+strings.ToUpper(strings.NewReplacer("-", "_", ".", "_").Replace(trimmed))+"_BIN")
	}
	for _, envName := range envNames {
		if env := strings.TrimSpace(os.Getenv(envName)); env != "" {
			return env, nil
		}
	}
	exe, err := executablePath()
	if err != nil {
		return "", err
	}
	exeDir := filepath.Dir(exe)
	for _, candidate := range []string{
		filepath.Join(exeDir, name),
		filepath.Join(exeDir, "..", "lib", "banger", name),
		filepath.Join(exeDir, "..", "libexec", "banger", name),
	} {
		if _, err := os.Stat(candidate); err == nil {
			return candidate, nil
		}
	}
	return "", fmt.Errorf("%s companion binary not found; run `make build` or reinstall banger", name)
}

func getenvDefault(key, fallback string) string {
	if value := strings.TrimSpace(os.Getenv(key)); value != "" {
		return value
	}
	return fallback
}