package classes

import (
	"crypto/sha256"
	"encoding/hex"
	"regexp"
	"strings"
	"testing"
)

// TestDeviceCodes pins the device token and short code (D-11, D-06)
// without a database: 10,000 tokens are 64 base64url characters, all
// distinct, and their stored form is the SHA-256 hex; 10,000 short codes
// are XXXX-XXXX over DeviceShortCodeAlphabet with every character of the
// alphabet in every position and no character far from its expected
// share; NormalizeDeviceShortCode accepts case, spaces and a missing
// hyphen and refuses lengths other than eight and the excluded letters.
func TestDeviceCodes(t *testing.T) {
	const draws = 10000

	t.Run("tokens", func(t *testing.T) {
		seen := make(map[string]struct{}, draws)
		for range draws {
			tok, err := NewDeviceToken()
			if err != nil {
				t.Fatal(err)
			}
			if len(tok) != 64 {
				t.Fatalf("token %q has %d characters", tok, len(tok))
			}
			if strings.Trim(tok, "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_") != "" {
				t.Fatalf("token %q is not base64url", tok)
			}
			if _, dup := seen[tok]; dup {
				t.Fatalf("token %q drawn twice", tok)
			}
			seen[tok] = struct{}{}
		}
		tok, _ := NewDeviceToken()
		sum := sha256.Sum256([]byte(tok))
		if got := HashAPIToken(tok); got != hex.EncodeToString(sum[:]) || len(got) != 64 || got == tok {
			t.Fatalf("stored form %q is not the SHA-256 hex of the token", got)
		}
	})

	t.Run("short_codes", func(t *testing.T) {
		alphabet := DeviceShortCodeAlphabet
		if alphabet != "23456789ABCDEFGHJKMNPQRSTUVWXYZ" || len(alphabet) != 31 {
			t.Fatalf("alphabet = %q", alphabet)
		}
		format := regexp.MustCompile(`^[` + alphabet + `]{4}-[` + alphabet + `]{4}$`)
		perPosition := make([]map[byte]int, 8)
		for i := range perPosition {
			perPosition[i] = map[byte]int{}
		}
		total := map[byte]int{}
		seen := map[string]struct{}{}
		for range draws {
			code, err := NewDeviceShortCode()
			if err != nil {
				t.Fatal(err)
			}
			if !format.MatchString(code) {
				t.Fatalf("short code %q", code)
			}
			seen[code] = struct{}{}
			raw := code[:4] + code[5:]
			for i := 0; i < 8; i++ {
				perPosition[i][raw[i]]++
				total[raw[i]]++
			}
		}
		// 31^8 codes: 10,000 draws repeating more than a handful would mean
		// a broken generator.
		if len(seen) < draws-5 {
			t.Fatalf("%d distinct codes in %d draws", len(seen), draws)
		}
		for i, counts := range perPosition {
			for j := 0; j < len(alphabet); j++ {
				if counts[alphabet[j]] == 0 {
					t.Fatalf("character %q never drawn at position %d", alphabet[j], i)
				}
			}
		}
		// Each character is expected 80000/31 ≈ 2581 times; a modulo bias
		// of the byte draw would push the first 8 characters ~3% up. Allow
		// 10% either way, far outside the noise of a fair draw.
		expected := float64(8*draws) / float64(len(alphabet))
		for j := 0; j < len(alphabet); j++ {
			got := float64(total[alphabet[j]])
			if got < expected*0.9 || got > expected*1.1 {
				t.Fatalf("character %q drawn %v times, expected about %.0f", alphabet[j], got, expected)
			}
		}
		for _, excluded := range "01ILO" {
			if total[byte(excluded)] != 0 {
				t.Fatalf("excluded character %q drawn", excluded)
			}
		}
	})

	t.Run("normalization", func(t *testing.T) {
		for _, c := range []struct{ in, want string }{
			{"ABCD-EFGH", "ABCD-EFGH"},
			{"abcd-efgh", "ABCD-EFGH"},
			{"AbCd-eFgH", "ABCD-EFGH"},
			{"ABCDEFGH", "ABCD-EFGH"},
			{"abcdefgh", "ABCD-EFGH"},
			{" ab cd ef gh ", "ABCD-EFGH"},
			{"ABCD - EFGH", "ABCD-EFGH"},
			{"A-B-C-D-E-F-G-H", "ABCD-EFGH"},
			{"2345-6789", "2345-6789"},
			{"zzzz zzzz", "ZZZZ-ZZZZ"},
		} {
			if got, ok := NormalizeDeviceShortCode(c.in); !ok || got != c.want {
				t.Errorf("normalize %q = %q, %v; want %q", c.in, got, ok, c.want)
			}
		}
		for _, in := range []string{
			"", "-", "ABCDEFG", "ABCD-EFG", "ABCDEFGHJ", "ABCD-EFGHJ",
			"ABCDEFG0", "ABCDEFG1", "ABCDEFGI", "ABCDEFGL", "ABCDEFGO", "abcdefgo", "abcdefgl", "abcdefgi",
			"ABCD_EFGH", "ABCD.EFGH", "ABCDÉFGH", "ABCD\tEFGH",
		} {
			if got, ok := NormalizeDeviceShortCode(in); ok {
				t.Errorf("normalize %q accepted as %q", in, got)
			}
		}
	})
}