X-Git-Url: https://piware.de/gitweb/?p=learn-rust.git;a=blobdiff_plain;f=concepts%2Fsrc%2Flib.rs;h=5f1feea9404c8116e1cbb1106b825e5a6d52c677;hp=b7e5eb8f1df11116f8d94fd31fb1afe29491d087;hb=HEAD;hpb=b653e9fe9d8492f2d4b5419721f7e00b392055f9

diff --git a/concepts/src/lib.rs b/concepts/src/lib.rs
index b7e5eb8..f2b1c10 100644
--- a/concepts/src/lib.rs
+++ b/concepts/src/lib.rs
@@ -1,11 +1,10 @@
+use std::collections::HashMap;
 use std::fs::File;
 use std::io::prelude::*;
-use std::collections::HashMap;
 
 pub fn read_file(path: &str) -> Result<String, std::io::Error> {
     let mut s = String::new();
-    File::open(path)?
-        .read_to_string(&mut s)?;
+    File::open(path)?.read_to_string(&mut s)?;
     Ok(s)
 }
 
@@ -71,7 +70,10 @@ where
     V: Copy,
 {
     pub fn new(calc: T) -> Cacher<T, A, V> {
-        Cacher { calc, values: HashMap::new() }
+        Cacher {
+            calc,
+            values: HashMap::new(),
+        }
     }
 
     pub fn value(&mut self, arg: A) -> V {
@@ -87,7 +89,7 @@ where
 }
 
 pub struct Counter5 {
-    count: u32
+    count: u32,
 }
 
 impl Counter5 {
@@ -108,3 +110,158 @@ impl Iterator for Counter5 {
         }
     }
 }
+
+pub struct Post {
+    state: Box<dyn State>,
+    content: String,
+}
+
+impl Post {
+    pub fn new() -> Post {
+        Post {
+            state: Box::new(Draft {}),
+            content: String::new(),
+        }
+    }
+
+    pub fn add_text(&mut self, text: &str) {
+        self.content.push_str(text);
+    }
+
+    pub fn content(&self) -> &str {
+        self.state.content(self)
+    }
+
+    pub fn request_review(&mut self) {
+        self.state = self.state.request_review();
+    }
+
+    pub fn approve(&mut self) {
+        self.state = self.state.approve();
+    }
+
+    pub fn reject(&mut self) {
+        self.state = self.state.reject();
+    }
+}
+
+trait State {
+    fn request_review(&self) -> Box<dyn State>;
+    fn approve(&mut self) -> Box<dyn State>;
+    fn reject(&self) -> Box<dyn State>;
+
+    #[allow(unused_variables)]
+    fn content<'a>(&self, post: &'a Post) -> &'a str {
+        ""
+    }
+}
+
+struct Draft {}
+impl State for Draft {
+    fn request_review(&self) -> Box<dyn State> {
+        Box::new(PendingReview { acks: 0 })
+    }
+
+    fn approve(&mut self) -> Box<dyn State> {
+        // don't change state
+        Box::new(Self {})
+    }
+
+    fn reject(&self) -> Box<dyn State> {
+        Box::new(Self {})
+    }
+}
+
+struct PendingReview {
+    acks: u32,
+}
+
+impl State for PendingReview {
+    fn request_review(&self) -> Box<dyn State> {
+        Box::new(Self { acks: self.acks })
+    }
+
+    fn approve(&mut self) -> Box<dyn State> {
+        if self.acks >= 1 {
+            Box::new(Published {})
+        } else {
+            Box::new(Self {
+                acks: self.acks + 1,
+            })
+        }
+    }
+
+    fn reject(&self) -> Box<dyn State> {
+        Box::new(Draft {})
+    }
+}
+
+struct Published {}
+impl State for Published {
+    fn request_review(&self) -> Box<dyn State> {
+        Box::new(Self {})
+    }
+
+    fn approve(&mut self) -> Box<dyn State> {
+        Box::new(Published {})
+    }
+
+    fn reject(&self) -> Box<dyn State> {
+        Box::new(Self {})
+    }
+
+    fn content<'a>(&self, post: &'a Post) -> &'a str {
+        &post.content
+    }
+}
+
+// state encoded as types; this is the "approved" state
+pub struct TPost {
+    content: String,
+}
+
+impl TPost {
+    pub fn new() -> TPostDraft {
+        TPostDraft {
+            content: String::new(),
+        }
+    }
+
+    pub fn content(&self) -> &str {
+        &self.content
+    }
+}
+
+pub struct TPostDraft {
+    content: String,
+}
+
+impl TPostDraft {
+    pub fn add_text(&mut self, text: &str) {
+        self.content.push_str(text);
+    }
+
+    pub fn request_review(self) -> TPostReview {
+        TPostReview {
+            content: self.content,
+        }
+    }
+}
+
+pub struct TPostReview {
+    content: String,
+}
+
+impl TPostReview {
+    pub fn approve(self) -> TPost {
+        TPost {
+            content: self.content,
+        }
+    }
+
+    pub fn reject(self) -> TPostDraft {
+        TPostDraft {
+            content: self.content,
+        }
+    }
+}