package main

import (
	"bytes"
	"net"
	"os"
	"path/filepath"
	"strings"
)

func word(words []string, i int) string {
	if i < len(words) {
		return words[i]
	}
	return ""
}

// splitLines splits s on newlines, dropping a trailing newline and returning
// nil for empty input.
func splitLines(s string) []string {
	s = strings.TrimRight(s, "\n")
	if s == "" {
		return nil
	}
	return strings.Split(s, "\n")
}

func isDir(p string) bool {
	fi, err := os.Stat(p)
	return err == nil && fi.IsDir()
}

// truthy reports whether a config string means "on" (1/true/yes/on).
func truthy(s string) bool {
	switch strings.ToLower(strings.TrimSpace(s)) {
	case "1", "true", "yes", "on":
		return true
	}
	return false
}

// falsy reports whether a config string explicitly means "off". It is not the
// negation of truthy: for a setting that defaults to on, an unset value or a
// typo must leave it on, and only a deliberate "off" may switch it off.
func falsy(s string) bool {
	switch strings.ToLower(strings.TrimSpace(s)) {
	case "0", "false", "no", "off":
		return true
	}
	return false
}

func fileExists(p string) bool {
	fi, err := os.Stat(p)
	return err == nil && !fi.IsDir()
}

func filesEqual(a, b string) bool {
	da, ea := os.ReadFile(a)
	db, eb := os.ReadFile(b)
	if ea != nil || eb != nil {
		return false
	}
	return bytes.Equal(da, db)
}

func copyFile(src, dst string) error {
	data, err := os.ReadFile(src)
	if err != nil {
		return err
	}
	if err := os.MkdirAll(filepath.Dir(dst), 0755); err != nil {
		return err
	}
	mode := os.FileMode(0644)
	if fi, err := os.Stat(src); err == nil {
		mode = fi.Mode()
	}
	return os.WriteFile(dst, data, mode)
}

func resolveIP() string {
	h, err := os.Hostname()
	if err != nil {
		return ""
	}
	addrs, err := net.LookupHost(h)
	if err != nil || len(addrs) == 0 {
		return ""
	}
	for _, a := range addrs {
		if ip := net.ParseIP(a); ip != nil && ip.To4() != nil {
			return a
		}
	}
	return addrs[0]
}

func shortHostname() string {
	h, _ := os.Hostname()
	if i := strings.IndexByte(h, '.'); i >= 0 {
		h = h[:i]
	}
	return h
}