package nomino

import (
	"errors"
	"math/rand"
)

// Generator is a function that returns the "random" portion of the returned filename.
// Technically, it doesn't necessarily need to be random, and could be based on time, or a counter,
// for example.
type Generator func(conf *Config) (string, error)

// Make allows you to generate a new string directly from a Generator.
func (g Generator) Make(opts ...Option) (string, error) {
	return g.MakeWithConfig(NewConfig(opts...))
}

// MakeWithConfig allows you to generate a new string directly from a Generator
// with a pre-existing Config.
func (g Generator) MakeWithConfig(c Config) (string, error) {
	return Make(c.AddOptions(WithGenerator(g)))
}

// WithGenerator sets the specified generator
func WithGenerator(g Generator) Option {
	return func(c *Config) {
		c.generator = g
	}
}

// ErrMissingGenerators is returned by a multi-generator if no generators are supplied.
var ErrMissingGenerators = errors.New("no generators supplied")

func missingGen(*Config) (string, error) {
	return "", ErrMissingGenerators
}

// MultiGeneratorInOrder allows the use of multiple generators. Each new invokation will use the next generator in turn.
// If none are passed, the generator will always return ErrMissingGenerators.
func MultiGeneratorInOrder(gens ...Generator) Generator {
	if len(gens) == 0 {
		return missingGen
	}

	if len(gens) == 1 {
		return gens[0]
	}

	var idx int
	return func(c *Config) (string, error) {
		st, err := gens[idx](c)
		idx = (idx + 1) % len(gens)
		return st, err
	}
}

// MultiGeneratorRandomOrder allows the use of multiple generators. Each new invokation will use one of the generators randomly.
// If none are passed, the generator will always return ErrMissingGenerators.
func MultiGeneratorRandomOrder(gens ...Generator) Generator {
	if len(gens) == 0 {
		return missingGen
	}

	if len(gens) == 1 {
		return gens[0]
	}

	return func(c *Config) (string, error) {
		idx := rand.Int() % len(gens)
		return gens[idx](c)
	}
}