package gofakeit

import "math/rand"

// Letter will generate a single random lower case ASCII letter
func Letter() string { return letter(globalFaker.Rand) }

// Letter will generate a single random lower case ASCII letter
func (f *Faker) Letter() string { return letter(f.Rand) }

func letter(r *rand.Rand) string { return string(randLetter(r)) }

// LetterN will generate a random ASCII string with length N. Note that this function returns a string with a length of 1 when 0 is passed.
func LetterN(n uint) string { return letterN(globalFaker.Rand, n) }

// LetterN will generate a random ASCII string with length N. Note that this function returns a string with a length of 1 when 0 is passed.
func (f *Faker) LetterN(n uint) string { return letterN(f.Rand, n) }

func letterN(r *rand.Rand, n uint) string {
	// Make sure we dont use 0
	if n == 0 {
		n = 1
	}
	out := make([]rune, n)
	for i := 0; i < int(n); i++ {
		out[i] = randLetter(r)
	}
	return string(out)
}

// Vowel will generate a single random lower case vowel
func Vowel() string { return vowel(globalFaker.Rand) }

// Vowel will generate a single random lower case vowel
func (f *Faker) Vowel() string { return vowel(f.Rand) }

func vowel(r *rand.Rand) string { return string(randCharacter(r, vowels)) }

// Digit will generate a single ASCII digit
func Digit() string { return digit(globalFaker.Rand) }

// Digit will generate a single ASCII digit
func (f *Faker) Digit() string { return digit(f.Rand) }

func digit(r *rand.Rand) string { return string(randDigit(r)) }

// DigitN will generate a random string of length N consists of ASCII digits. Note that the string generated can start with 0 and this function returns a string with a length of 1 when 0 is passed.
func DigitN(n uint) string { return digitN(globalFaker.Rand, n) }

// DigitN will generate a random string of length N consists of ASCII digits. Note that the string generated can start with 0 and this function returns a string with a length of 1 when 0 is passed.
func (f *Faker) DigitN(n uint) string { return digitN(f.Rand, n) }

func digitN(r *rand.Rand, n uint) string {
	// Make sure we dont use 0
	if n == 0 {
		n = 1
	}
	out := make([]rune, n)
	for i := 0; i < int(n); i++ {
		out[i] = randDigit(r)
	}
	return string(out)
}

// Numerify will replace # with random numerical values
func Numerify(str string) string { return numerify(globalFaker.Rand, str) }

// Numerify will replace # with random numerical values
func (f *Faker) Numerify(str string) string { return numerify(f.Rand, str) }

func numerify(r *rand.Rand, str string) string { return replaceWithNumbers(r, str) }

// Lexify will replace ? with random generated letters
func Lexify(str string) string { return lexify(globalFaker.Rand, str) }

// Lexify will replace ? with random generated letters
func (f *Faker) Lexify(str string) string { return lexify(f.Rand, str) }

func lexify(r *rand.Rand, str string) string { return replaceWithLetters(r, str) }

// ShuffleStrings will randomize a slice of strings
func ShuffleStrings(a []string) { shuffleStrings(globalFaker.Rand, a) }

// ShuffleStrings will randomize a slice of strings
func (f *Faker) ShuffleStrings(a []string) { shuffleStrings(f.Rand, a) }

func shuffleStrings(r *rand.Rand, a []string) {
	swap := func(i, j int) {
		a[i], a[j] = a[j], a[i]
	}
	//to avoid upgrading to 1.10 I copied the algorithm
	n := len(a)
	if n <= 1 {
		return
	}

	//if size is > int32 probably it will never finish, or ran out of entropy
	i := n - 1
	for ; i > 0; i-- {
		j := int(r.Int31n(int32(i + 1)))
		swap(i, j)
	}
}

// RandomString will take in a slice of string and return a randomly selected value
func RandomString(a []string) string { return randomString(globalFaker.Rand, a) }

// RandomString will take in a slice of string and return a randomly selected value
func (f *Faker) RandomString(a []string) string { return randomString(f.Rand, a) }

func randomString(r *rand.Rand, a []string) string {
	size := len(a)
	if size == 0 {
		return ""
	}
	if size == 1 {
		return a[0]
	}
	return a[r.Intn(size)]
}

func addStringLookup() {
	AddFuncLookup("letter", Info{
		Display:     "Letter",
		Category:    "string",
		Description: "Generate a single random lower case ASCII letter",
		Example:     "g",
		Output:      "string",
		Generate: func(r *rand.Rand, m *MapParams, info *Info) (interface{}, error) {
			return letter(r), nil
		},
	})

	AddFuncLookup("lettern", Info{
		Display:     "LetterN",
		Category:    "string",
		Description: "Generate a random ASCII string with length N",
		Example:     "gbRMaRxHki",
		Output:      "string",
		Params: []Param{
			{Field: "count", Display: "Count", Type: "uint", Description: "Number of digits to generate"},
		},
		Generate: func(r *rand.Rand, m *MapParams, info *Info) (interface{}, error) {
			ui, err := info.GetUint(m, "count")
			if err != nil {
				return nil, err
			}

			return letterN(r, ui), nil
		},
	})

	AddFuncLookup("vowel", Info{
		Display:     "Vowel",
		Category:    "string",
		Description: "Generate a single random lower case vowel",
		Example:     "a",
		Output:      "string",
		Generate: func(r *rand.Rand, m *MapParams, info *Info) (interface{}, error) {
			return vowel(r), nil
		},
	})

	AddFuncLookup("digit", Info{
		Display:     "Digit",
		Category:    "string",
		Description: "Generate a single ASCII digit",
		Example:     "0",
		Output:      "string",
		Generate: func(r *rand.Rand, m *MapParams, info *Info) (interface{}, error) {
			return digit(r), nil
		},
	})

	AddFuncLookup("digitn", Info{
		Display:     "DigitN",
		Category:    "string",
		Description: "Generate a random string of length N consists of ASCII digits",
		Example:     "0136459948",
		Output:      "string",
		Params: []Param{
			{Field: "count", Display: "Count", Type: "uint", Description: "Number of digits to generate"},
		},
		Generate: func(r *rand.Rand, m *MapParams, info *Info) (interface{}, error) {
			ui, err := info.GetUint(m, "count")
			if err != nil {
				return nil, err
			}

			return digitN(r, ui), nil
		},
	})

	AddFuncLookup("numerify", Info{
		Display:     "Numerify",
		Category:    "string",
		Description: "Replace # with random numerical values",
		Example:     "(###)###-#### => (555)867-5309",
		Output:      "string",
		Params: []Param{
			{Field: "str", Display: "String", Type: "string", Description: "String value to replace #'s"},
		},
		Generate: func(r *rand.Rand, m *MapParams, info *Info) (interface{}, error) {
			str, err := info.GetString(m, "str")
			if err != nil {
				return nil, err
			}

			return numerify(r, str), nil
		},
	})

	AddFuncLookup("lexify", Info{
		Display:     "Lexify",
		Category:    "string",
		Description: "Replace ? with random generated letters",
		Example:     "?????@??????.com => billy@mister.com",
		Output:      "string",
		Params: []Param{
			{Field: "str", Display: "String", Type: "string", Description: "String value to replace ?'s"},
		},
		Generate: func(r *rand.Rand, m *MapParams, info *Info) (interface{}, error) {
			str, err := info.GetString(m, "str")
			if err != nil {
				return nil, err
			}

			return lexify(r, str), nil
		},
	})

	AddFuncLookup("shufflestrings", Info{
		Display:     "Shuffle Strings",
		Category:    "string",
		Description: "Shuffle an array of strings",
		Example:     "hello,world,whats,up => whats,world,hello,up",
		Output:      "[]string",
		ContentType: "application/json",
		Params: []Param{
			{Field: "strs", Display: "Strings", Type: "[]string", Description: "Delimited separated strings"},
		},
		Generate: func(r *rand.Rand, m *MapParams, info *Info) (interface{}, error) {
			strs, err := info.GetStringArray(m, "strs")
			if err != nil {
				return nil, err
			}

			shuffleStrings(r, strs)

			return strs, nil
		},
	})

	AddFuncLookup("randomstring", Info{
		Display:     "Random String",
		Category:    "string",
		Description: "Randomly grab one string from array",
		Example:     "hello,world,whats,up => world",
		Output:      "[]string",
		Params: []Param{
			{Field: "strs", Display: "Strings", Type: "[]string", Description: "Delimited separated strings"},
		},
		Generate: func(r *rand.Rand, m *MapParams, info *Info) (interface{}, error) {
			strs, err := info.GetStringArray(m, "strs")
			if err != nil {
				return nil, err
			}

			return randomString(r, strs), nil
		},
	})
}