// Package util includes various helper functions for common
// string manipulation and file handling operations.
package util

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

var (
	// Error messages.
	err = struct {
		dirNotCreated  string
		dirNotOpened   string
		dirNotRead     string
		fileNotCopied  string
		fileNotCreated string
		fileNotLoaded  string
	}{
		dirNotCreated:  "Error: directory could not be created:",
		dirNotOpened:   "Error: directory could not be opened:",
		dirNotRead:     "Error: directory not readable:",
		fileNotCopied:  "Error: file could not be copied:",
		fileNotCreated: "Error: file could not be created.",
		fileNotLoaded:  "Error: file could not be loaded:",
	}
)

// HasError returns true if error e is a non-empty value and prints
// string msg to standard output, or false otherwise. If exitOnErr is
// true, sends exit signal code 3 instead of a returning a boolean value.
func HasError(e error, msg string, exitOnErr ...bool) bool {
	if e != nil {
		fmt.Println(msg)
		if len(exitOnErr) == 1 {
			if exitOnErr[0] {
				os.Exit(3)
			}
		}
		return true
	} else {
		return false
	}
}

// FileExists returns true a file or directory at path exists, or
// false otherwise.
func FileExists(path string) bool {
	if _, fileErr := os.Stat(path); fileErr == nil {
		return true
	} else {
		return false
	}
}

// MinMax returns the smaller and larger value of two numbers,
// in that order.
func MinMax(n1, n2 int) (int, int) {
	if n1 < n2 {
		return n1, n2
	} else {
		return n2, n1
	}
}

// MultiReplace returns a copy of string str after replacing values
// from map of key-value string pairs rep.
func MultiReplace(str string, rep map[string]string) string {
	s := str
	for k, v := range rep {
		s = strings.ReplaceAll(s, k, v)
	}
	return s
}

// MutliOrdReplace returns a copy of string str after replacing values
// from rep, a slice of maps containing key-value string pairs. Like
// MultiReplace for multiple maps.
func MultiOrdReplace(str string, rep []map[string]string) string {
	s := str
	for _, e := range rep {
		for k, v := range e {
			s = strings.ReplaceAll(s, k, v)
		}
	}
	return s
}

// ReplaceExt returns a copy of the string path with its file extension
// replaced with string ext. If path has no extension, returns a copy of path
// with ext appended to it.
func ReplaceExt(path, ext string) string {
	if filepath.Ext(path) != "" {
		return strings.Replace(path, filepath.Ext(path), ext, 1)
	}
	return path + ext
}

// ConvertPath returns a copy of string path with Unix shorthand locations
// "~/" and "$HOME" expanded to the full absolute path.
func ConvertPath(path string) string {
	home, homeErr := os.UserHomeDir()
	if homeErr == nil {
		if strings.HasPrefix(path, "~/") {
			return strings.Replace(path, "~/", home+string(os.PathSeparator), 1)
		} else if strings.HasPrefix(path, "~"+filepath.Base(home)) {
			return strings.Replace(path, "~"+filepath.Base(home), home, 1)
		} else if strings.HasPrefix(path, "$HOME") {
			return strings.Replace(path, "$HOME", home, 1)
		}
	}
	return path
}

// GetFileList returns a string slice containing a list of files at path.
//
// sortOrder options: modTime, modTimeDesc, name, nameDesc
//
// If includeDirs is true, include directory names in the list.
func GetFileList(path string, sortOrder string, includeDirs bool) []string {
	dir, openErr := os.Open(filepath.FromSlash(path))
	HasError(openErr, err.dirNotOpened+" "+path)
	files, readErr := dir.ReadDir(0)
	HasError(readErr, err.dirNotRead+" "+path)

	var list []string
	if strings.Contains(sortOrder, "modTime") {
		mapTimes := make(map[string]string)
		var times []string
		for _, file := range files {
			if !file.IsDir() || (file.IsDir() && includeDirs) {
				fi, _ := file.Info()
				mapTimes[fmt.Sprint(fi.ModTime())] = filepath.Join(path,
					fi.Name())
				times = append(times, fmt.Sprint(fi.ModTime()))
			}
		}
		slices.Sort(times)
		for _, t := range times {
			list = append(list, mapTimes[t])
		}
	} else if strings.Contains(sortOrder, "name") {
		for _, file := range files {
			if !file.IsDir() || (file.IsDir() && includeDirs) {
				list = append(list, filepath.Join(path, file.Name()))
			}
		}
		slices.Sort(list)
	}

	if strings.Contains(sortOrder, "Desc") {
		slices.Reverse(list)
	}
	return list
}

// MakeDir returns true if a new directory is created successfully or already
// exists at path, or false otherwise. If exitOnErr is true, sends an
// application exit signal if an error occurs.
func MakeDir(path string, exitOnErr ...bool) bool {
	toExit := false
	if len(exitOnErr) == 1 {
		if exitOnErr[0] == true {
			toExit = true
		}
	}
	if !HasError(os.MkdirAll(filepath.FromSlash(path), 0755), err.dirNotCreated+
		" "+path, toExit) {
		return true
	} else {
		return false
	}
}

// CopyFile returns true if a file is copied successfully from srcPath to
// destPath, or false otherwise.
func CopyFile(srcPath, destPath string) bool {
	src, srcErr := os.Open(srcPath)
	HasError(srcErr, err.fileNotLoaded+" "+srcPath)
	defer src.Close()

	dest, destErr := os.Create(destPath)
	HasError(destErr, err.fileNotCreated)
	defer dest.Close()

	_, copyErr := io.Copy(dest, src)
	return HasError(copyErr, err.fileNotCopied+" "+destPath)
}

// CopyFiles copies files in srcPath to destPath. If overwrite is true,
// copying overwrites files of the same name at destPath.
func CopyFiles(srcPath string, destPath string, overwrite bool) {
	files := GetFileList(srcPath, "name", false)
	for _, file := range files {
		destFile := filepath.Join(destPath, filepath.Base(file))
		if !FileExists(destFile) || (FileExists(destFile) && overwrite) {
			CopyFile(file, destFile)
		}
	}
}

// SaveFile writes the string contents of str to file at path. If exitOnErr is
// true, sends an application exit signal if an error occurs.
func SaveFile(path string, str string, exitOnErr ...bool) {
	fh, fileErr := os.Create(filepath.FromSlash(path))
	toExit := false
	if len(exitOnErr) == 1 {
		if exitOnErr[0] == true {
			toExit = true
		}
	}
	if !HasError(fileErr, err.fileNotCreated, toExit) {
		fmt.Fprint(fh, str)
	}
}

// LoadFile returns the contents of path as string. If exitOnErr is true, sends
// an application exit signal if an error occurs.
func LoadFile(path string, exitOnErr ...bool) string {
	contents, fileErr := os.ReadFile(filepath.FromSlash(path))
	toExit := false
	if len(exitOnErr) == 1 {
		if exitOnErr[0] == true {
			toExit = true
		}
	}
	HasError(fileErr, err.fileNotLoaded+" "+path, toExit)
	return string(contents)
}