package pwgen_test

import (
	"errors"
	"strings"
	"testing"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"

	"sneak.berlin/go/x/internal/pwgen"
)

const generateRounds = 300

// testWords mixes usable words with entries the filter must drop:
// capitalized, too short, too long, punctuation, digits, and non-ASCII.
func testWords() []string {
	return []string{
		"apple", "banana", "cherry", "grape", "lemon", "mango", "melon", "peach",
		"Capital", "ab", "abc", "toolongwordhere", "has-dash", "num3er", "éclair",
	}
}

func usableTestWords() map[string]bool {
	return map[string]bool{
		"apple": true, "banana": true, "cherry": true, "grape": true,
		"lemon": true, "mango": true, "melon": true, "peach": true,
	}
}

func TestNewFiltersWords(t *testing.T) {
	t.Parallel()

	generator, err := pwgen.New(pwgen.Params{Words: testWords()})
	require.NoError(t, err)

	assert.Equal(t, len(usableTestWords()), generator.UsableWords())
}

func TestNewHonorsLengthBounds(t *testing.T) {
	t.Parallel()

	generator, err := pwgen.New(pwgen.Params{
		Words:         testWords(),
		MinWordLength: 2,
		MaxWordLength: 3,
	})
	require.NoError(t, err)

	assert.Equal(t, 2, generator.UsableWords(), `only "ab" and "abc" fit`)
}

func TestNewRejectsNoUsableWords(t *testing.T) {
	t.Parallel()

	_, err := pwgen.New(pwgen.Params{Words: []string{"Capital", "ab"}})
	require.ErrorIs(t, err, pwgen.ErrNoUsableWords)

	_, err = pwgen.New(pwgen.Params{Words: []string{}})
	require.ErrorIs(t, err, pwgen.ErrNoUsableWords)
}

func TestNewRejectsInvalidBounds(t *testing.T) {
	t.Parallel()

	_, err := pwgen.New(pwgen.Params{
		Words:         testWords(),
		MinWordLength: 9,
		MaxWordLength: 4,
	})
	require.ErrorIs(t, err, pwgen.ErrInvalidWordLength)

	_, err = pwgen.New(pwgen.Params{Words: testWords(), MinWordLength: -1})
	require.ErrorIs(t, err, pwgen.ErrInvalidWordLength)
}

func TestGenerateFormat(t *testing.T) {
	t.Parallel()

	generator, err := pwgen.New(pwgen.Params{Words: testWords()})
	require.NoError(t, err)

	usable := usableTestWords()

	for range generateRounds {
		password, err := generator.Generate()
		require.NoError(t, err)

		words, digits, delimiter := parsePassword(t, password)

		assert.Contains(t, pwgen.Delimiters, string(delimiter))
		assert.Len(t, words, pwgen.WordCount)

		for _, word := range words {
			assert.True(t, usable[word], "unexpected word %q in %q", word, password)
		}

		for _, digit := range digits {
			assert.True(t, digit >= '0' && digit <= '9', "digit in %q", password)
		}
	}
}

func TestGenerateVariesDelimitersAndDigits(t *testing.T) {
	t.Parallel()

	generator, err := pwgen.New(pwgen.Params{Words: testWords()})
	require.NoError(t, err)

	delimitersSeen := map[byte]bool{}
	digitsSeen := map[byte]bool{}
	passwordsSeen := map[string]bool{}

	for range generateRounds {
		password, err := generator.Generate()
		require.NoError(t, err)

		_, digits, delimiter := parsePassword(t, password)
		delimitersSeen[delimiter] = true
		passwordsSeen[password] = true

		for _, digit := range digits {
			digitsSeen[digit] = true
		}
	}

	assert.Greater(t, len(delimitersSeen), 1, "delimiter should vary")
	assert.Greater(t, len(digitsSeen), 1, "digits should vary")
	assert.Greater(t, len(passwordsSeen), generateRounds/2, "passwords repeat")
}

func TestNewWithSystemDictionary(t *testing.T) {
	t.Parallel()

	generator, err := pwgen.New(pwgen.Params{})
	if errors.Is(err, pwgen.ErrNoUsableWords) {
		t.Skip("this system has no word list")
	}

	require.NoError(t, err)
	assert.Greater(t, generator.UsableWords(), 1000)

	password, err := generator.Generate()
	require.NoError(t, err)

	parsePassword(t, password)
}

// parsePassword splits a password of the form
// <word><digit><delim><word><digit><delim><word><digit> into its words,
// digits, and the delimiter, failing the test if it is not of that shape.
func parsePassword(t *testing.T, password string) ([]string, []byte, byte) {
	t.Helper()

	delimiterIndex := strings.IndexFunc(password, func(r rune) bool {
		return (r < 'a' || r > 'z') && (r < '0' || r > '9')
	})
	require.NotEqual(t, -1, delimiterIndex, "no delimiter in %q", password)

	delimiter := password[delimiterIndex]
	parts := strings.Split(password, string(delimiter))
	require.Len(t, parts, pwgen.WordCount, "wrong shape: %q", password)

	words := make([]string, 0, len(parts))
	digits := make([]byte, 0, len(parts))

	for _, part := range parts {
		require.GreaterOrEqual(t, len(part), 2, "short part in %q", password)

		words = append(words, part[:len(part)-1])
		digits = append(digits, part[len(part)-1])
	}

	return words, digits, delimiter
}