package string_manipulation

import (
	"errors"
	"math"
	"math/rand"
	"regexp"
	"strings"
	"time"
	"unicode"
)

// input is struct that holds input form user and result
type input struct {
	Input  string
	Result string
}

// StringManipulation is an interface that holds all abstract methods to manipulate strings
type StringManipulation interface {
	Between(start, end string) StringManipulation
	Boolean() bool
	CamelCase(rule ...string) string
	ContainsAll(check ...string) bool
	Delimited(delimiter string, rule ...string) StringManipulation
	Get() string
	KebabCase(rule ...string) StringManipulation
	LcFirst() string
	Lines() []string
	Pad(length int, with, padType string) string
	RemoveSpecialCharacter() string
	ReplaceFirst(search, replace string) string
	ReplaceLast(search, replace string) string
	Reverse() string
	Shuffle() string
	Surround(with string) string
	SnakeCase(rule ...string) StringManipulation
	Tease(length int, indicator string) string
	ToLower() string
	ToUpper() string
	UcFirst() string
}

// New func returns pointer to input struct
func New(val string) StringManipulation {
	return &input{Input: val}
}

// Between takes two param start and end which are string
// return value after omitting start and end part of input
func (i *input) Between(start, end string) StringManipulation {
	if start == "" && end == "" || i.Input == "" {
		return i
	}

	input := strings.ToLower(i.Input)
	lcStart := strings.ToLower(start)
	lcEnd := strings.ToLower(end)
	var startIndex, endIndex int

	if len(start) > 0 && strings.Contains(input, lcStart) {
		startIndex = len(start)
	}
	if len(end) > 0 && strings.Contains(input, lcEnd) {
		endIndex = strings.Index(input, lcEnd)
	} else if len(input) > 0 {
		endIndex = len(input)
	}
	i.Result = strings.TrimSpace(i.Input[startIndex:endIndex])
	return i
}

// Boolean func return boolean value of string value like on, off, 0, 1, yes, no
// returns boolean value of string input
func (i *input) Boolean() bool {
	input := getInput(*i)
	inputLower := strings.ToLower(input)
	off := contains(False, inputLower)
	if off {
		return false
	}
	on := contains(True, inputLower)
	if on {
		return true
	}
	panic(errors.New("invalid string value to test boolean value"))
}

// CamelCase takes one Param rule and it returns passed string in
// camel case form and rule helps to omit character you want from string
// Example input: hello user
// Result : HelloUser
func (i *input) CamelCase(rule ...string) string {
	input := getInput(*i)
	// removing excess space
	wordArray := caseHelper(input, true, rule...)
	for i, word := range wordArray {
		wordArray[i] = ucfirst(word)
	}
	return strings.Join(wordArray, "")
}

// ContainsAll function takes multiple string param and
// checks if they are present in input
func (i *input) ContainsAll(check ...string) bool {
	input := getInput(*i)
	for _, item := range check {
		if !strings.Contains(input, item) {
			return false
		}
	}
	return true
}

// Delimited function joins the string by passed delimeter
func (i *input) Delimited(delimiter string, rule ...string) StringManipulation {
	input := getInput(*i)
	if strings.TrimSpace(delimiter) == "" {
		delimiter = "."
	}
	wordArray := caseHelper(input, false, rule...)
	i.Result = strings.Join(wordArray, delimiter)
	return i
}

// Get simply returns result and can be chained on function which
// returns StringManipulation interface
func (i *input) Get() string {
	return getInput(*i)
}

// KebabCase takes one Param rule and it returns passed string in
// kebab case form and rule helps to omit character you want from string
// Example input: hello user
// Result : hello-user
func (i *input) KebabCase(rule ...string) StringManipulation {
	input := getInput(*i)
	wordArray := caseHelper(input, false, rule...)
	i.Result = strings.Join(wordArray, "-")
	return i
}

// LcFirst simply returns result by lowercasing first letter of string and
// it can be chained on function which return StringManipulation interface
func (i *input) LcFirst() string {
	input := getInput(*i)
	for i, v := range input {
		return string(unicode.ToUpper(v)) + input[i+1:]
	}
	return input
}

// Lines returns slice of strings by removing white space characters
func (i *input) Lines() []string {
	input := getInput(*i)
	matchWord := regexp.MustCompile(`[\s]*[\W]\pN`)
	result := matchWord.ReplaceAllString(input, " ")
	return strings.Fields(strings.TrimSpace(result))
}

// Pad takes three param length i.e total length to be after padding,
// with i.e  what to pad with and pad type which can be (both or left or right)
// it return string after padding upto length by with param and on padType type
// it can be chained on function which return StringManipulation interface
func (i *input) Pad(length int, with, padType string) string {
	input := getInput(*i)
	inputLength := len(input)
	padLength := len(with)
	if inputLength >= length {
		return input
	}
	switch padType {
	case Right:
		var count = 1 + ((length - padLength) / padLength)
		var result = input + strings.Repeat(with, count)
		return result[:length]
	case Left:
		var count = 1 + ((length - padLength) / padLength)
		var result = strings.Repeat(with, count) + input
		return result[(len(result) - length):]
	case Both:
		length := (float64(length - inputLength)) / float64(2)
		repeat := math.Ceil(length / float64(padLength))
		return strings.Repeat(with, int(repeat))[:int(math.Floor(float64(length)))] + input + strings.Repeat(with, int(repeat))[:int(math.Ceil(float64(length)))]
	default:
		return input
	}
}

// RemoveSpecialCharacter removes all special characters and returns the string
// it can be chained on function which return StringManipulation interface
func (i *input) RemoveSpecialCharacter() string {
	input := getInput(*i)
	var result strings.Builder
	for i := 0; i < len(input); i++ {
		b := input[i]
		if ('a' <= b && b <= 'z') ||
			('A' <= b && b <= 'Z') ||
			('0' <= b && b <= '9') ||
			b == ' ' {
			result.WriteByte(b)
		}
	}
	return result.String()
}

// ReplaceFirst takes two param search and replace
// it return string by searching search sub string and replacing it
// with replace substring on first occurrence
// it can be chained on function which return StringManipulation interface
func (i *input) ReplaceFirst(search, replace string) string {
	input := getInput(*i)
	return replaceStr(input, search, replace, First)
}

// ReplaceLast takes two param search and replace
// it return string by searching search sub string and replacing it
// with replace substring on last occurrence
// it can be chained on function which return StringManipulation interface
func (i *input) ReplaceLast(search, replace string) string {
	input := getInput(*i)
	return replaceStr(input, search, replace, Last)
}

// Reverse reverses the passed strings
// it can be chained on function which return StringManipulation interface
func (i *input) Reverse() string {
	input := getInput(*i)
	r := []rune(input)
	for i, j := 0, len(r)-1; i < len(r)/2; i, j = i+1, j-1 {
		r[i], r[j] = r[j], r[i]
	}
	return string(r)
}

// Shuffle shuffles the given string randomly
// it can be chained on function which return StringManipulation interface
func (i *input) Shuffle() string {
	input := getInput(*i)
	rand.Seed(time.Now().Unix())

	inRune := []rune(input)
	rand.Shuffle(len(inRune), func(i, j int) {
		inRune[i], inRune[j] = inRune[j], inRune[i]
	})
	return string(inRune)
}

// SnakeCase is variadic function that takes one param rule
// it returns passed string in snake case form and rule helps to
// omit character you want from string
// Example input: hello user
// Result : hello_user
func (i *input) SnakeCase(rule ...string) StringManipulation {
	input := getInput(*i)
	wordArray := caseHelper(input, false, rule...)
	i.Result = strings.Join(wordArray, "_")
	return i
}

// Surround takes one param with which is used to surround user input
// it can be chained on function which return StringManipulation interface
func (i *input) Surround(with string) string {
	input := getInput(*i)
	return with + input + with
}

// Tease takes two params length and indicator and it shortens given string
// on passed length and adds indicator on end
// it can be chained on function which return StringManipulation interface
func (i *input) Tease(length int, indicator string) string {
	input := getInput(*i)
	if input == "" || len(input) < length {
		return input
	}
	return input[:length] + indicator
}

// ToLowerr makes all string of user input to lowercase
// it can be chained on function which return StringManipulation interface
func (i *input) ToLower() (result string) {
	input := getInput(*i)
	return strings.ToLower(input)
}

// ToUpper makes all string of user input to uppercase
// it can be chained on function which return StringManipulation interface
func (i *input) ToUpper() string {
	input := getInput(*i)
	return strings.ToUpper(input)
}

// UcFirst makes first word of user input to uppercase
// it can be chained on function which return StringManipulation interface
func (i *input) UcFirst() string {
	input := getInput(*i)
	return ucfirst(input)
}