From 67b01b750d6704c7c9ca1accab2e41c1fd8cdc74 Mon Sep 17 00:00:00 2001
From: brxken128 <77554505+brxken128@users.noreply.github.com>
Date: Tue, 26 Jul 2022 11:42:17 +0100
Subject: [PATCH] structs: add trio

---
 src/structs.rs      |   2 +
 src/structs/trio.rs | 126 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 128 insertions(+)
 create mode 100644 src/structs/trio.rs

diff --git a/src/structs.rs b/src/structs.rs
index 00f1e8d..86c0232 100644
--- a/src/structs.rs
+++ b/src/structs.rs
@@ -5,6 +5,8 @@
 
 mod pair;
 mod sep_vec;
+mod trio;
 
 pub use pair::*;
 pub use sep_vec::*;
+pub use trio::*;
diff --git a/src/structs/trio.rs b/src/structs/trio.rs
new file mode 100644
index 0000000..65aa650
--- /dev/null
+++ b/src/structs/trio.rs
@@ -0,0 +1,126 @@
+//! Contains the implementations to parse triple-tuple type
+//!
+
+use crate::core::EString;
+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 trio (A, B, C) tuple to split string by separators (`S1` and `S2`).
+///
+/// **NOTE**: Required the enabling of the `tuple` feature.
+///
+/// # Examples
+///
+/// ```rust
+/// use estring::{Trio, EString};
+///
+/// type EqTrio<A, B, C> = Trio<A, '=', B, '=', C>;
+///
+/// fn main() -> Result<(), estring::ParseError> {
+///     let res = EString::from("one=two=free").parse::<EqTrio<&str, &str, &str>>()?;
+///     assert_eq!(res, Trio("one", "two", "free"));
+///     Ok(())
+/// }
+/// ```
+///
+#[derive(Debug, PartialEq, Clone)]
+pub struct Trio<A, const S1: char, B, const S2: char, C>(pub A, pub B, pub C);
+
+impl<A, B, C, const S1: char, const S2: char> From<(A, B, C)> for Trio<A, S1, B, S2, C> {
+    #[inline]
+    fn from((a, b, c): (A, B, C)) -> Self {
+        Self(a, b, c)
+    }
+}
+
+impl<A, B, C, const S1: char, const S2: char> std::fmt::Display for Trio<A, S1, B, S2, C>
+where
+    A: std::fmt::Display,
+    B: std::fmt::Display,
+    C: 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())?;
+        f.write_char(S2)?;
+        f.write_str(&self.2.to_string())
+    }
+}
+
+impl<A, const S1: char, B, const S2: char, C> TryFrom<EString> for Trio<A, S1, B, S2, C>
+where
+    A: TryFrom<EString>,
+    B: TryFrom<EString>,
+    C: 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))?;
+            b.split_once(S2).ok_or(Error::Split).and_then(|(b, c)| {
+                let b = B::try_from(EString::from(b)).map_err(|_| Error::Parse(1))?;
+                let c = C::try_from(EString::from(c)).map_err(|_| Error::Parse(2))?;
+                Ok(Self(a, b, c))
+            })
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::structs::SepVec;
+
+    #[test]
+    fn should_parse_into_trio() {
+        type EqTrio<A, B, C> = Trio<A, '=', B, '=', C>;
+        let estr = EString::from("hello=world=hello");
+        match estr.parse::<EqTrio<&str, &str, &str>>() {
+            Ok(res) => assert_eq!((res.0, res.1, res.2), ("hello", "world", "hello")),
+            _ => unreachable!(),
+        };
+    }
+
+    #[test]
+    fn should_parse_into_trio_with_alternate_delims() {
+        type EqTrio<A, B, C> = Trio<A, '-', B, '^', C>;
+        let estr = EString::from("hello-world^hello");
+        match estr.parse::<EqTrio<&str, &str, &str>>() {
+            Ok(res) => assert_eq!((res.0, res.1, res.2), ("hello", "world", "hello")),
+            _ => unreachable!(),
+        };
+    }
+
+    #[test]
+    fn should_parse_rest_as_trio() {
+        type EqTrio<A, B, C> = Trio<A, '=', B, '=', C>;
+        let estr = EString::from("hello=world=hello=world=hello");
+        match estr.parse::<EqTrio<&str, &str, EqTrio<&str, &str, &str>>>() {
+            Ok(res) => assert_eq!(res, Trio("hello", "world", Trio("hello", "world", "hello"))),
+            _ => unreachable!(),
+        };
+    }
+}