package hook

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

	"git.zb-server.de/Sebi/ssh-netbox-wrapper/internal/storage"
)

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

	// AliasesMarker is the unique string used to detect the aliases source line.
	AliasesMarker = "netssh/aliases.sh"
	// AliasesSourceLine is the bash/zsh line that sources the generated aliases file.
	AliasesSourceLine = "source ~/.cache/netssh/aliases.sh 2>/dev/null  # netssh aliases"
)

// 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":
		dir := os.Getenv("ZDOTDIR")
		if dir == "" {
			dir = os.Getenv("HOME")
		}
		return filepath.Join(dir, ".zshrc"), nil
	case "fish":
		return filepath.Join(FishConfigDir(), "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
	}
	for _, line := range strings.Split(string(data), "\n") {
		if strings.TrimSpace(line) == BlockStart || hookLinePattern.MatchString(strings.TrimSpace(line)) {
			return true
		}
	}
	return false
}

// Install writes the managed netssh block into the profile. Entries written by
// older versions without markers are replaced instead of duplicated; an
// existing managed block (e.g. from install.sh) is left untouched.
// Returns (true, nil) when the profile changed, (false, nil) when already present.
// Creates the profile file (and any parent directories) if they do not exist.
func Install(profilePath, shell string) (installed bool, err error) {
	data, err := os.ReadFile(profilePath)
	if err != nil && !os.IsNotExist(err) {
		return false, fmt.Errorf("reading profile: %w", err)
	}
	for _, line := range strings.Split(string(data), "\n") {
		if strings.TrimSpace(line) == BlockStart {
			return false, nil
		}
	}
	cleaned, _, err := clean(string(data), profilePath)
	if err != nil {
		return false, err
	}
	if cleaned != "" && !strings.HasSuffix(cleaned, "\n") {
		cleaned += "\n"
	}
	if cleaned != "" {
		cleaned += "\n"
	}
	cleaned += Block(shell)
	if err := os.MkdirAll(filepath.Dir(profilePath), 0o755); err != nil {
		return false, fmt.Errorf("creating directory: %w", err)
	}
	if err := writeProfile(profilePath, cleaned); err != nil {
		return false, err
	}
	return true, nil
}

// Block returns the managed profile block for shell.
func Block(shell string) string {
	var b strings.Builder
	b.WriteString(BlockStart + "\n")
	b.WriteString("netssh shell-init\n")
	if shell != "fish" {
		aliases := shellQuote(AliasesPath(), "bash")
		fmt.Fprintf(&b, "[ ! -f %s ] || . %s\n", aliases, aliases)
	}
	if shell == "zsh" {
		b.WriteString(ZshRegistration(ZshFuncDir()))
	}
	b.WriteString(BlockEnd + "\n")
	return b.String()
}

// ZshRegistration adds dir to fpath and registers the completion even when
// compinit already ran earlier in .zshrc (e.g. via oh-my-zsh).
func ZshRegistration(dir string) string {
	return fmt.Sprintf("fpath=(%s $fpath)\nif (( $+functions[compdef] )); then autoload -Uz _netssh && compdef _netssh netssh; fi\n", shellQuote(dir, "bash"))
}

// InstallAliasesSource appends the aliases source line to a bash/zsh profile.
// This is a no-op for fish (which uses conf.d auto-sourcing instead).
// Returns (true, nil) when newly added, (false, nil) when already present.
func InstallAliasesSource(profilePath string) (installed bool, err error) {
	data, err := os.ReadFile(profilePath)
	if err != nil && !os.IsNotExist(err) {
		return false, fmt.Errorf("reading profile: %w", err)
	}
	for _, line := range strings.Split(string(data), "\n") {
		if strings.TrimSpace(line) == BlockStart || aliasesLinePattern.MatchString(strings.TrimSpace(line)) {
			return false, nil
		}
	}
	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, "%s\n", "source "+shellQuote(AliasesPath(), "bash")+" 2>/dev/null  # netssh aliases"); err != nil {
		return false, err
	}
	return true, nil
}

var hookLinePattern = regexp.MustCompile(`^(?:[^\s]*/)?netssh\s+shell-init\s*(?:#.*)?$`)
var aliasesLinePattern = regexp.MustCompile(`^(?:source|\.)\s+["']?[^;|&]*netssh/aliases\.sh["']?(?:\s+2>/dev/null)?\s*(?:#.*)?$`)

// legacyPatterns match the unmarked lines written by older versions and by
// manual setup instructions. They mirror the patterns in install.sh.
var legacyPatterns = []*regexp.Regexp{
	hookLinePattern,
	aliasesLinePattern,
	regexp.MustCompile(`^eval\s+["']?\$\((?:[^\s]*/)?netssh\s+alias(?:\s+--shell\s+(?:bash|zsh))?\)["']?\s*(?:#.*)?$`),
	regexp.MustCompile(`^(?:[^\s]*/)?netssh\s+alias(?:\s+--shell\s+fish)?\s*\|\s*source\s*(?:#.*)?$`),
	regexp.MustCompile(`^source\s+<\((?:[^\s]*/)?netssh\s+alias\)\s*(?:#.*)?$`),
	regexp.MustCompile(`^alias\s+[A-Za-z0-9_.-]+(?:=|\s+)["']netssh(?:\s+[^"']+)?["']\s*(?:#.*)?$`),
}

func isLegacyLine(line string) bool {
	for _, pattern := range legacyPatterns {
		if pattern.MatchString(line) {
			return true
		}
	}
	return false
}

// HasEntries reports whether the profile contains a managed block or legacy lines.
func HasEntries(profilePath string) bool {
	data, err := os.ReadFile(profilePath)
	if err != nil {
		return false
	}
	_, removed, err := clean(string(data), profilePath)
	return removed || err != nil
}

// Uninstall removes legacy hook lines and complete installer-managed blocks.
// Missing profiles are a no-op; malformed blocks leave the file unchanged.
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)
	}
	cleaned, removed, err := clean(string(data), profilePath)
	if err != nil || !removed {
		return false, err
	}
	return true, writeProfile(profilePath, cleaned)
}

// clean strips managed blocks and legacy lines from profile content.
func clean(data, profilePath string) (cleaned string, removed bool, err error) {
	if data == "" {
		return "", false, nil
	}
	var kept []string
	inside := false
	for _, line := range strings.Split(data, "\n") {
		value := strings.TrimSpace(line)
		switch value {
		case BlockStart:
			if inside {
				return "", false, fmt.Errorf("nested netssh block in %s", profilePath)
			}
			inside = true
			removed = true
			continue
		case BlockEnd:
			if !inside {
				return "", false, fmt.Errorf("unmatched netssh block in %s", profilePath)
			}
			inside = false
			continue
		}
		if inside {
			continue
		}
		if isLegacyLine(value) {
			removed = true
			continue
		}
		kept = append(kept, line)
	}
	if inside {
		return "", false, fmt.Errorf("unclosed netssh block in %s", profilePath)
	}
	if !removed {
		return data, false, nil
	}
	cleaned = strings.ReplaceAll(strings.Join(kept, "\n"), "\n\n\n", "\n\n")
	// Drop the blank separator line Install puts in front of the block.
	if strings.HasSuffix(cleaned, "\n\n") {
		cleaned = strings.TrimRight(cleaned, "\n") + "\n"
	}
	return cleaned, true, nil
}

// writeProfile replaces the profile atomically, following dotfile symlinks
// and keeping the permissions of an existing file.
func writeProfile(profilePath, content string) error {
	target, err := filepath.EvalSymlinks(profilePath)
	if os.IsNotExist(err) {
		target = profilePath
	} else if err != nil {
		return err
	}
	mode := os.FileMode(0o644)
	if info, err := os.Stat(target); err == nil {
		mode = info.Mode().Perm()
	}
	if err := storage.WriteFile(target, []byte(content), mode); err != nil {
		return fmt.Errorf("writing profile: %w", err)
	}
	return nil
}

// ProfileCandidates lists every shell profile netssh or install.sh may have
// written to, in the same order as the installer.
func ProfileCandidates() []string {
	home := os.Getenv("HOME")
	zdot := zshDir()
	paths := []string{
		filepath.Join(home, ".bashrc"),
		filepath.Join(home, ".bash_profile"),
		filepath.Join(home, ".bash_login"),
		filepath.Join(home, ".profile"),
		filepath.Join(zdot, ".zshrc"),
		filepath.Join(zdot, ".zprofile"),
		filepath.Join(zdot, ".zshenv"),
	}
	if zdot != home {
		paths = append(paths, filepath.Join(home, ".zshrc"), filepath.Join(home, ".zprofile"), filepath.Join(home, ".zshenv"))
	}
	return append(paths, filepath.Join(FishConfigDir(), "config.fish"))
}