Add percent_encode and percent_decode (#121)

3 files changed, 104 insertions, 1 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c9c9dfe..06389e9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,9 +5,10 @@
 - The `function` module gains `curry2` to `curry6`.
 - The `list` module gains the `each`, and `partition` functions.
 - The `int` and `float` modules gain the `negate` function.
+- The `int` module gains the `to_float` function.
 - The `result` module gains the `all` function.
 - The `dynamic` module gains the `option` function.
-- The `int` module gains the `to_float` function.
+- The `uri` module gains the `percent_encode` and `percent_decode` functions.
 
 ## v0.11.0 - 2020-08-22
 
diff --git a/src/gleam/uri.gleam b/src/gleam/uri.gleam
index 32910b5..2ff542a 100644
--- a/src/gleam/uri.gleam
+++ b/src/gleam/uri.gleam
@@ -14,6 +14,7 @@ import gleam/string
 import gleam/dynamic.{Dynamic}
 import gleam/map.{Map}
 import gleam/function
+import gleam/pair
 
 /// Type representing holding the parsed components of an URI.
 /// All components of a URI are optional, except the path.
@@ -119,6 +120,33 @@ pub fn query_to_string(query: List(tuple(String, String))) -> String {
   |> result.unwrap("")
 }
 
+/// Encode a string into a percent encoded representation.
+/// Note that this encodes space as +.
+///
+/// ## Example
+///
+/// percent_encode("100% great")
+/// > "100%25+great"
+///
+pub fn percent_encode(value: String) -> String {
+  query_to_string([tuple("k", value)])
+  |> string.replace(each: "k=", with: "")
+}
+
+/// Decode a percent encoded string.
+///
+/// ## Example
+///
+/// percent_decode("100%25+great")
+/// > Ok("100% great")
+///
+pub fn percent_decode(value: String) -> Result(String, Nil) {
+  string.concat(["k=", value])
+  |> parse_query
+  |> result.then(list.head)
+  |> result.map(pair.second)
+}
+
 fn do_remove_dot_segments(
   input: List(String),
   accumulator: List(String),
diff --git a/test/gleam/uri_test.gleam b/test/gleam/uri_test.gleam
index 55a4bd6..779e078 100644
--- a/test/gleam/uri_test.gleam
+++ b/test/gleam/uri_test.gleam
@@ -1,5 +1,7 @@
 import gleam/uri
 import gleam/should
+import gleam/string
+import gleam/list
 import gleam/option.{None, Some}
 
 pub fn full_parse_test() {
@@ -92,6 +94,78 @@ pub fn empty_query_to_string_test() {
   should.equal(query_string, "")
 }
 
+fn percent_codec_fixtures() {
+  [
+    tuple(" ", "+"),
+    tuple(",", "%2C"),
+    tuple(";", "%3B"),
+    tuple(":", "%3A"),
+    tuple("!", "%21"),
+    tuple("?", "%3F"),
+    tuple("'", "%27"),
+    tuple("(", "%28"),
+    tuple(")", "%29"),
+    tuple("[", "%5B"),
+    tuple("@", "%40"),
+    tuple("/", "%2F"),
+    tuple("\\", "%5C"),
+    tuple("&", "%26"),
+    tuple("#", "%23"),
+    tuple("=", "%3D"),
+    tuple("~", "%7E"),
+    tuple("ñ", "%C3%B1"),
+    // Allowed chars
+    tuple("-", "-"),
+    tuple("_", "_"),
+    tuple(".", "."),
+    tuple("*", "*"),
+    tuple("100% great", "100%25+great"),
+  ]
+}
+
+pub fn percent_encode_test() {
+  percent_codec_fixtures()
+  |> list.map(fn(t) {
+    let tuple(a, b) = t
+    uri.percent_encode(a)
+    |> should.equal(b)
+  })
+}
+
+pub fn percent_encode_consistency_test() {
+  let k = "foo bar[]"
+  let v = "ñaña (,:*~)"
+
+  assert query_string = uri.query_to_string([tuple(k, v)])
+
+  let encoded_key = uri.percent_encode(k)
+  let encoded_value = uri.percent_encode(v)
+  let manual_query_string = string.concat([encoded_key, "=", encoded_value])
+
+  should.equal(query_string, manual_query_string)
+}
+
+pub fn percent_decode_test() {
+  percent_codec_fixtures()
+  |> list.map(fn(t) {
+    let tuple(a, b) = t
+    uri.percent_decode(b)
+    |> should.equal(Ok(a))
+  })
+}
+
+pub fn percent_decode_consistency_test() {
+  let k = "foo+bar[]"
+  let v = "%C3%B6rebro"
+  let query = string.concat([k, "=", v])
+  assert Ok(parsed) = uri.parse_query(query)
+
+  assert Ok(decoded_key) = uri.percent_decode(k)
+  assert Ok(decoded_value) = uri.percent_decode(v)
+
+  should.equal(parsed, [tuple(decoded_key, decoded_value)])
+}
+
 pub fn parse_segments_test() {
   should.equal(uri.path_segments("/"), [])
   should.equal(uri.path_segments("/foo/bar"), ["foo", "bar"])