package hook

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

const (
	// Marker is the unique string used to detect an existing hook installation.
	Marker = "netssh shell-init"
	// Line is the full line written into the shell profile.
	Line = "netssh shell-init  # netssh cache auto-refresh"
)

// ProfilePath returns the canonical shell profile path for the given shell name.
func ProfilePath(shell string) (string, error) {
	switch shell {
	case "bash":
		return filepath.Join(os.Getenv("HOME"), ".bashrc"), nil
	case "zsh":
		return filepath.Join(os.Getenv("HOME"), ".zshrc"), nil
	case "fish":
		configDir, err := os.UserConfigDir()
		if err != nil {
			configDir = filepath.Join(os.Getenv("HOME"), ".config")
		}
		return filepath.Join(configDir, "fish", "config.fish"), nil
	default:
		return "", fmt.Errorf("unsupported shell %q — supported: bash, zsh, fish", shell)
	}
}

// ReloadNote returns the shell-specific hint for reloading the profile.
func ReloadNote(profilePath string) string {
	return "Reload with: source " + profilePath
}

// IsInstalled reports whether the hook marker is present in the profile file.
// Returns false if the file does not exist or cannot be read.
func IsInstalled(profilePath string) bool {
	data, err := os.ReadFile(profilePath)
	if err != nil {
		return false
	}
	return strings.Contains(string(data), Marker)
}

// Install appends the hook line to the profile if it is not already present.
// Returns (true, nil) when newly installed, (false, nil) when already present.
// Creates the profile file (and any parent directories) if they do not exist.
func Install(profilePath string) (installed bool, err error) {
	if IsInstalled(profilePath) {
		return false, nil
	}
	if err := os.MkdirAll(filepath.Dir(profilePath), 0o755); err != nil {
		return false, fmt.Errorf("creating directory: %w", err)
	}
	f, err := os.OpenFile(profilePath, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0o644)
	if err != nil {
		return false, fmt.Errorf("opening profile: %w", err)
	}
	defer f.Close()
	if _, err := fmt.Fprintf(f, "\n%s\n", Line); err != nil {
		return false, err
	}
	return true, nil
}

// Uninstall removes the hook line from the profile.
// Returns (true, nil) when removed, (false, nil) when the hook was not found.
// Returns (false, nil) — not an error — when the file does not exist.
func Uninstall(profilePath string) (removed bool, err error) {
	data, err := os.ReadFile(profilePath)
	if os.IsNotExist(err) {
		return false, nil
	}
	if err != nil {
		return false, fmt.Errorf("reading profile: %w", err)
	}
	content := string(data)
	if !strings.Contains(content, Marker) {
		return false, nil
	}

	var kept []string
	for _, line := range strings.Split(content, "\n") {
		if strings.Contains(line, Marker) {
			continue
		}
		kept = append(kept, line)
	}
	// Collapse triple blank lines that the removal may leave.
	cleaned := strings.ReplaceAll(strings.Join(kept, "\n"), "\n\n\n", "\n\n")

	if err := os.WriteFile(profilePath, []byte(cleaned), 0o644); err != nil {
		return false, fmt.Errorf("writing profile: %w", err)
	}
	return true, nil
}