package pwgen

var (
	_         Generator = (*DefaultGenerator)(nil)
	Default   DefaultGenerator
	lowerCase = alphabet('a', 'z')
	upperCase = alphabet('A', 'Z')
	letters   = merge(lowerCase, upperCase)
	digits    = alphabet('0', '9')
)

type DefaultGenerator struct {
}

func (d DefaultGenerator) Generate(opts ...GeneratorOption) (string, error) {
	compiledOptions := defaultOptions(opts...)
	fullAlphabet := merge(lowerCase, upperCase, digits, []rune(compiledOptions.SpecialsAlphabet))

	effectiveLength, err := compiledOptions.effectiveLength()
	if err != nil {
		return "", err
	}

	generated := make([]rune, 0, effectiveLength)

	for i := uint(0); i < compiledOptions.Lowercase; i++ {
		generated = append(generated, runeFor(lowerCase, compiledOptions.PRNG))
	}

	for i := uint(0); i < compiledOptions.Uppercase; i++ {
		generated = append(generated, runeFor(upperCase, compiledOptions.PRNG))
	}

	for i := uint(0); i < compiledOptions.Digits; i++ {
		generated = append(generated, runeFor(digits, compiledOptions.PRNG))
	}

	for i := uint(0); i < compiledOptions.Specials; i++ {
		generated = append(generated, runeFor([]rune(compiledOptions.SpecialsAlphabet), compiledOptions.PRNG))
	}

	for i := compiledOptions.Lowercase + compiledOptions.Uppercase; i < compiledOptions.Letters; i++ {
		generated = append(generated, runeFor(letters, compiledOptions.PRNG))
	}

	for i := uint(len(generated)); i < effectiveLength; i++ {
		generated = append(generated, runeFor(fullAlphabet, compiledOptions.PRNG))
	}

	return string(shuffle(generated, compiledOptions.PRNG)), nil
}