9 files changed, 282 insertions(+), 0 deletions(-)

A go/atbash-cipher/.exercism/config.json
A go/atbash-cipher/.exercism/metadata.json
A go/atbash-cipher/HELP.md
A go/atbash-cipher/README.md
A go/atbash-cipher/atbash_cipher.go
A go/atbash-cipher/atbash_cipher.go.1
A go/atbash-cipher/atbash_cipher_test.go
A go/atbash-cipher/cases_test.go
A go/atbash-cipher/go.mod

@@ 0,0 1,37 @@
+{
+  "blurb": "Create an implementation of the atbash cipher, an ancient encryption system created in the Middle East.",
+  "authors": [
+    "zilkey"
+  ],
+  "contributors": [
+    "alebaffa",
+    "bitfield",
+    "ekingery",
+    "ferhatelmas",
+    "hilary",
+    "kytrinyx",
+    "leenipper",
+    "petertseng",
+    "robphoenix",
+    "sebito91",
+    "strangeman",
+    "tleen",
+    "tompao"
+  ],
+  "files": {
+    "solution": [
+      "atbash_cipher.go"
+    ],
+    "test": [
+      "atbash_cipher_test.go"
+    ],
+    "example": [
+      ".meta/example.go"
+    ],
+    "editor": [
+      "cases_test.go"
+    ]
+  },
+  "source": "Wikipedia",
+  "source_url": "http://en.wikipedia.org/wiki/Atbash"
+}

@@ 0,0 1,1 @@
+{"track":"go","exercise":"atbash-cipher","id":"7115dba7a4d545ef84e71780b66f814b","url":"https://exercism.org/tracks/go/exercises/atbash-cipher","handle":"telemachus","is_requester":true,"auto_approve":false}<
\ No newline at end of file

@@ 0,0 1,40 @@
+# Help
+
+## Running the tests
+
+To run the tests run the command `go test` from within the exercise directory.
+
+If the test suite contains benchmarks, you can run these with the `--bench` and `--benchmem`
+flags:
+
+    go test -v --bench . --benchmem
+
+Keep in mind that each reviewer will run benchmarks on a different machine, with
+different specs, so the results from these benchmark tests may vary.
+
+## Submitting your solution
+
+You can submit your solution using the `exercism submit atbash_cipher.go` command.
+This command will upload your solution to the Exercism website and print the solution page's URL.
+
+It's possible to submit an incomplete solution which allows you to:
+
+- See how others have completed the exercise
+- Request help from a mentor
+
+## Need to get help?
+
+If you'd like help solving the exercise, check the following pages:
+
+- The [Go track's documentation](https://exercism.org/docs/tracks/go)
+- [Exercism's support channel on gitter](https://gitter.im/exercism/support)
+- The [Frequently Asked Questions](https://exercism.org/docs/using/faqs)
+
+Should those resources not suffice, you could submit your (incomplete) solution to request mentoring.
+
+To get help if you're having trouble, you can use one of the following resources:
+
+- [How to Write Go Code](https://golang.org/doc/code.html)
+- [Effective Go](https://golang.org/doc/effective_go.html)
+- [Go Resources](http://golang.org/help)
+- [StackOverflow](http://stackoverflow.com/questions/tagged/go)<
\ No newline at end of file

@@ 0,0 1,61 @@
+# Atbash Cipher
+
+Welcome to Atbash Cipher on Exercism's Go Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Instructions
+
+Create an implementation of the atbash cipher, an ancient encryption system created in the Middle East.
+
+The Atbash cipher is a simple substitution cipher that relies on
+transposing all the letters in the alphabet such that the resulting
+alphabet is backwards. The first letter is replaced with the last
+letter, the second with the second-last, and so on.
+
+An Atbash cipher for the Latin alphabet would be as follows:
+
+```text
+Plain:  abcdefghijklmnopqrstuvwxyz
+Cipher: zyxwvutsrqponmlkjihgfedcba
+```
+
+It is a very weak cipher because it only has one possible key, and it is
+a simple mono-alphabetic substitution cipher. However, this may not have
+been an issue in the cipher's time.
+
+Ciphertext is written out in groups of fixed length, the traditional group size
+being 5 letters, leaving numbers unchanged, and punctuation is excluded.
+This is to make it harder to guess things based on word boundaries.
+
+## Examples
+
+- Encoding `test` gives `gvhg`
+- Encoding `x123 yes` gives `c123b vh`
+- Decoding `gvhg` gives `test`
+- Decoding `gsvjf rxpyi ldmul cqfnk hlevi gsvoz abwlt` gives `thequickbrownfoxjumpsoverthelazydog`
+
+## Source
+
+### Created by
+
+- @zilkey
+
+### Contributed to by
+
+- @alebaffa
+- @bitfield
+- @ekingery
+- @ferhatelmas
+- @hilary
+- @kytrinyx
+- @leenipper
+- @petertseng
+- @robphoenix
+- @sebito91
+- @strangeman
+- @tleen
+- @tompao
+
+### Based on
+
+Wikipedia - http://en.wikipedia.org/wiki/Atbash<
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@@ 0,0 1,25 @@
+package atbash
+
+import (
+	"strings"
+)
+
+func Atbash(s string) string {
+	var atbash strings.Builder
+	for _, b := range []byte(s) {
+		// This leaves an unwanted space at the end of the string. Trim that off
+		// later.
+		if atbash.Len()%6 == 5 {
+			atbash.WriteByte(' ')
+		}
+		switch {
+		case b >= 'a' && b <= 'z':
+			atbash.WriteByte('z' - b + 'a')
+		case b >= 'A' && b <= 'Z':
+			atbash.WriteByte('z' - b + 'A')
+		case b >= '0' && b <= '9':
+			atbash.WriteByte(b)
+		}
+	}
+	return strings.TrimSuffix(atbash.String(), " ")
+}

@@ 0,0 1,29 @@
+package atbash
+
+import "strings"
+
+const (
+	plain  = "abcdefghijklmnopqrstuvwxyz123456789"
+	cipher = "zyxwvutsrqponmlkjihgfedcba123456789"
+)
+
+func Atbash(s string) string {
+	bs := make([]byte, 0, len(s))
+	kept := 0
+	s = strings.ToLower(s)
+
+	for _, b := range []byte(s) {
+		n := strings.IndexByte(plain, b)
+		if n == -1 {
+			continue
+		}
+		// This adds an unwanted space when kept == 0. Trim that off
+		// later rather than add a test if keep == 0 to every loop.
+		if kept%5 == 0 {
+			bs = append(bs, ' ')
+		}
+		bs = append(bs, cipher[n])
+		kept++
+	}
+	return strings.TrimPrefix(string(bs), " ")
+}

@@ 0,0 1,25 @@
+package atbash
+
+import "testing"
+
+func TestAtbash(t *testing.T) {
+	for _, test := range tests {
+		actual := Atbash(test.s)
+		if actual != test.expected {
+			t.Errorf("Atbash('%s'): expected '%s', actual '%s'", test.s, test.expected, actual)
+		}
+	}
+}
+
+func BenchmarkAtbash(b *testing.B) {
+	if testing.Short() {
+		b.Skip("skipping benchmark in short mode.")
+	}
+	for i := 0; i < b.N; i++ {
+
+		for _, test := range tests {
+			Atbash(test.s)
+		}
+
+	}
+}

@@ 0,0 1,61 @@
+package atbash
+
+// Source: exercism/problem-specifications
+// Commit: dda678b atbash-cipher: Apply new "input" policy
+// Problem Specifications Version: 1.1.0
+
+type atbashTest struct {
+	s        string
+	expected string
+}
+
+var tests = []atbashTest{
+	{
+		s:        "yes",
+		expected: "bvh",
+	},
+	{
+		s:        "no",
+		expected: "ml",
+	},
+	{
+		s:        "OMG",
+		expected: "lnt",
+	},
+	{
+		s:        "O M G",
+		expected: "lnt",
+	},
+	{
+		s:        "mindblowingly",
+		expected: "nrmwy oldrm tob",
+	},
+	{
+		s:        "Testing,1 2 3, testing.",
+		expected: "gvhgr mt123 gvhgr mt",
+	},
+	{
+		s:        "Truth is fiction.",
+		expected: "gifgs rhurx grlm",
+	},
+	{
+		s:        "The quick brown fox jumps over the lazy dog.",
+		expected: "gsvjf rxpyi ldmul cqfnk hlevi gsvoz abwlt",
+	},
+	{
+		s:        "exercism",
+		expected: "vcvix rhn",
+	},
+	{
+		s:        "anobstacleisoftenasteppingstone",
+		expected: "zmlyh gzxov rhlug vmzhg vkkrm thglm v",
+	},
+	{
+		s:        "testing123testing",
+		expected: "gvhgr mt123 gvhgr mt",
+	},
+	{
+		s:        "thequickbrownfoxjumpsoverthelazydog",
+		expected: "gsvjf rxpyi ldmul cqfnk hlevi gsvoz abwlt",
+	},
+}

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+module atbash
+
+go 1.16