From c099d860bd5d1c4e63ba86c9ff6e34a9e6ab3f2a Mon Sep 17 00:00:00 2001
From: Dmitriy Pleshevskiy <dmitriy@ideascup.me>
Date: Sun, 24 Jul 2022 02:18:44 +0300
Subject: [PATCH] core/tuple: add support for pair tuple

---
 Cargo.toml        |   1 +
 src/core.rs       |   5 ++
 src/core/tuple.rs | 132 ++++++++++++++++++++++++++++++++++++++++++++++
 src/core/vec.rs   |   2 -
 src/lib.rs        |   9 ----
 5 files changed, 138 insertions(+), 11 deletions(-)
 create mode 100644 src/core/tuple.rs

diff --git a/Cargo.toml b/Cargo.toml
index 3713155..93c00b0 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -25,6 +25,7 @@ prim = ["number", "bool"]
 number = []
 bool = []
 vec = []
+tuple = []
 
 [dependencies]
 
diff --git a/src/core.rs b/src/core.rs
index 68a2151..3e2fdac 100644
--- a/src/core.rs
+++ b/src/core.rs
@@ -11,6 +11,11 @@ pub mod vec;
 #[cfg(feature = "vec")]
 pub use vec::*;
 
+#[cfg(feature = "tuple")]
+pub mod tuple;
+#[cfg(feature = "tuple")]
+pub use tuple::*;
+
 use crate::ParseError;
 use std::convert::{Infallible, TryFrom};
 
diff --git a/src/core/tuple.rs b/src/core/tuple.rs
new file mode 100644
index 0000000..0e993b5
--- /dev/null
+++ b/src/core/tuple.rs
@@ -0,0 +1,132 @@
+//! Contains the implementations to tuple type
+//!
+//! **NOTE**: Require the enabling of the `tuple` features
+//!
+
+use crate::core::EString;
+use std::convert::TryFrom;
+use std::fmt::Write;
+
+/// The error type for operations interacting with parsing tuples. Possibly returned from
+/// ``EString::parse``
+#[derive(Debug)]
+pub enum Error {
+    /// The specified input string is not split.
+    Split,
+
+    /// The specified substring of the split input string is not parsed
+    Parse(u8),
+}
+
+impl std::fmt::Display for Error {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Error::Split => f.write_str("Cannot split input string"),
+            Error::Parse(n) => write!(f, "Cannot parse {} substring", n),
+        }
+    }
+}
+
+impl std::error::Error for Error {}
+
+/// Wrapper for pair (A, B) tuple to split string by a separator (`S1`).
+///
+/// **NOTE**: Required the enabling of the `tuple` feature.
+///
+/// # Examples
+///
+/// ```rust
+/// use estring::{Pair, EString};
+///
+/// type EqPair<A, B> = Pair<A, '=', B>;
+///
+/// fn main() -> Result<(), estring::ParseError> {
+///     let res = EString::from("one=two=free").parse::<EqPair<&str, &str>>()?;
+///     assert_eq!(res, Pair("one", "two=free"));
+///     Ok(())
+/// }
+/// ```
+///
+#[derive(Debug, PartialEq, Clone)]
+pub struct Pair<A, const S1: char, B>(pub A, pub B);
+
+impl<A, B, const S1: char> From<(A, B)> for Pair<A, S1, B> {
+    #[inline]
+    fn from((a, b): (A, B)) -> Self {
+        Self(a, b)
+    }
+}
+
+impl<A, B, const S1: char> std::fmt::Display for Pair<A, S1, B>
+where
+    A: std::fmt::Display,
+    B: std::fmt::Display,
+{
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str(&self.0.to_string())?;
+        f.write_char(S1)?;
+        f.write_str(&self.1.to_string())
+    }
+}
+
+impl<A, const S1: char, B> TryFrom<EString> for Pair<A, S1, B>
+where
+    A: TryFrom<EString>,
+    B: TryFrom<EString>,
+{
+    type Error = Error;
+
+    fn try_from(value: EString) -> Result<Self, Self::Error> {
+        value.split_once(S1).ok_or(Error::Split).and_then(|(a, b)| {
+            let a = A::try_from(EString::from(a)).map_err(|_| Error::Parse(0))?;
+            let b = B::try_from(EString::from(b)).map_err(|_| Error::Parse(1))?;
+            Ok(Self(a, b))
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    type EqPair<A, B> = Pair<A, '=', B>;
+
+    #[test]
+    fn should_parse_into_pair() {
+        let estr = EString::from("hello=world=hello");
+        match estr.parse::<EqPair<&str, &str>>() {
+            Ok(res) => assert_eq!((res.0, res.1), ("hello", "world=hello")),
+            _ => unreachable!(),
+        };
+    }
+
+    #[test]
+    fn should_parse_rest_as_pair() {
+        let estr = EString::from("hello=world=hello");
+        match estr.parse::<EqPair<&str, EqPair<&str, &str>>>() {
+            Ok(res) => assert_eq!(res, Pair("hello", Pair("world", "hello"))),
+            _ => unreachable!(),
+        };
+    }
+
+    #[cfg(feature = "number")]
+    mod vec {
+        use crate::SepVec;
+
+        use super::*;
+
+        type LineVec<T> = SepVec<T, '\n'>;
+
+        #[test]
+        fn should_parse_vec_of_pairs() {
+            let estr = EString::from(
+                "foo=bar
+hello=bar",
+            );
+            match estr.parse::<LineVec<EqPair<&str, &str>>>() {
+                Ok(res) => assert_eq!(res, SepVec(vec![Pair("foo", "bar"), Pair("hello", "bar"),])),
+                _ => unreachable!(),
+            };
+        }
+    }
+}
diff --git a/src/core/vec.rs b/src/core/vec.rs
index c59d45c..3077379 100644
--- a/src/core/vec.rs
+++ b/src/core/vec.rs
@@ -21,10 +21,8 @@ use std::fmt::Write;
 /// fn main() -> Result<(), estring::ParseError> {
 ///     let res = EString::from("1,2,3").parse::<CommaVec<u8>>()?;
 ///     assert_eq!(*res, vec![1, 2, 3]);
-///
 ///     Ok(())
 /// }
-///
 /// ```
 ///
 #[derive(Debug, PartialEq, Clone)]
diff --git a/src/lib.rs b/src/lib.rs
index ef409a0..3d57f5d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -36,12 +36,3 @@ mod error;
 
 pub use crate::core::*;
 pub use crate::error::ParseError;
-
-#[cfg(test)]
-mod tests {
-    #[test]
-    fn it_works() {
-        let result = 2 + 2;
-        assert_eq!(result, 4);
-    }
-}