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
}

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")
	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} {
		if err := os.MkdirAll(dir, 0o755); 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
}