implement user skeleton struct

.gitignore

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+/target
+**/*.rs.bk
+Cargo.lock

Cargo.toml

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+[package]
+name = "libmatrix-client"
+version = "0.1.0"
+authors = ["Edward Shen <code@eddie.sh>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

src/api/mod.rs

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+use std::fmt;
+
+#[derive(Debug, PartialEq)]
+pub struct Client {}
+
+impl Client{
+    pub fn new() -> Self {
+        Client {}
+    }
+}
+
+#[derive(Default)]
+pub struct ApiError {}
+
+impl fmt::Display for ApiError {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "an error occurred!")
+    }
+}

src/lib.rs

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+#![forbid(unsafe_code)]
+
+mod api;
+mod client;
+mod room;
+mod user;

src/room/mod.rs

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+pub struct Room {}

src/user.rs

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+use crate::api::{ApiError, Client};
+use crate::room::Room;
+use std::fmt;
+
+#[derive(Debug, PartialEq, Eq)]
+enum UserInitErrorReason {
+    InvalidUsername,
+    NoDomainProvided,
+}
+
+#[derive(Debug, PartialEq)]
+struct UserInitError {
+    message: String,
+    reason: UserInitErrorReason,
+}
+
+impl UserInitError {
+    fn new(msg: &str, reason: UserInitErrorReason) -> Self {
+        UserInitError {
+            message: msg.to_string(),
+            reason,
+        }
+    }
+}
+
+impl fmt::Display for UserInitError {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "{}", self.message)
+    }
+}
+
+#[derive(Debug, PartialEq)]
+struct User {
+    id: String,
+    display_name: Option<String>,
+    client: Client,
+}
+
+impl User {
+    /// Constructs a new User. This represents a user in a room.
+    ///
+    /// # Arguments
+    /// - `id` - The fully qualified user id, following the form @user:domain. Currently, this only
+    ///     checks whether the id starts with `@` and contains a `:`.
+    /// - `display_name` - Some display name to use??? TODO: Figure out what this does
+    ///
+    /// Returns either a new User struct or an error containing the reason why it failed to create a
+    /// new User.
+    pub fn new(id: String, display_name: Option<String>) -> Result<Self, UserInitError> {
+        if !id.starts_with("@") {
+            Err(UserInitError::new(
+                "User ID must start with a @",
+                UserInitErrorReason::InvalidUsername,
+            ))
+        } else if !id.contains(":") {
+            Err(UserInitError::new(
+                "User ID must contain a :",
+                UserInitErrorReason::NoDomainProvided,
+            ))
+        } else {
+            Ok(User {
+                id,
+                display_name,
+                client: Client::new(),
+            })
+        }
+    }
+
+    fn get_display_name(room: Room) -> String {
+        unimplemented!()
+    }
+
+    fn set_display_name(&mut self, name: &str) -> Result<(), ApiError> {
+        unimplemented!()
+    }
+
+    fn get_avatar_url() -> Result<String, ApiError> {
+        unimplemented!()
+    }
+
+    fn set_avatar_url(url: &str) -> Result<(), ApiError> {
+        unimplemented!()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn new_returns_err_on_invalid_id() {
+        assert_eq!(
+            User::new(String::from("abc:edf"), None),
+            Err(UserInitError {
+                message: "User ID must start with a @".to_string(),
+                reason: UserInitErrorReason::InvalidUsername
+            })
+        );
+
+        assert_eq!(
+            User::new(String::from("@abcedf"), None),
+            Err(UserInitError {
+                message: "User ID must contain a :".to_string(),
+                reason: UserInitErrorReason::NoDomainProvided
+            })
+        );
+    }
+
+    #[test]
+    fn new_returns_struct_on_valid_input() {
+        assert_eq!(
+            User::new("@eddie:eddie.sh".to_string(), None),
+            Ok(User {
+                id: "@eddie:eddie.sh".to_string(),
+                display_name: None,
+                client: Client::new()
+            })
+        )
+    }
+}