Create query method

src/data/error.rs

@@ -0,0 +1,28 @@
+use core::fmt;
+use serde::export::Formatter;
+use std::error;
+
+/// Simple rust error
+///
+/// @author Pierre Hubert
+
+#[derive(Debug, Clone)]
+pub struct ExecError(pub String);
+
+impl ExecError {
+    pub fn new(msg: &str) -> ExecError {
+        ExecError(msg.to_string())
+    }
+
+    pub fn boxed_new(msg: &str) -> Box<ExecError> {
+        Box::new(ExecError(msg.to_string()))
+    }
+}
+
+impl fmt::Display for ExecError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        write!(f, "Encountered error: {}", self.0)
+    }
+}
+
+impl error::Error for ExecError {}

src/data/mod.rs

@@ -1,3 +1,5 @@
+pub mod error;
 pub mod config;
+
 pub mod http_error;
 pub mod http_request_handler;

src/helpers/database.rs

@@ -1,14 +1,20 @@
+use std::collections;
 use std::error::Error;
+use std::ops::Add;
 use std::sync::{Arc, Mutex};
 
-use mysql::Pool;
+use mysql::{Binary, Pool, ResultSet};
+use mysql::prelude::Queryable;
 
 use crate::data::config::DatabaseConfig;
+use crate::data::error::ExecError;
 
 /// Database access helper
 ///
 /// @author Pierre Hubert
 
+pub type ProcessRowResult<E> = Result<E, Box<dyn Error>>;
+
 // Pool shared across threads
 static mut POOL: Option<Arc<Mutex<mysql::Pool>>> = None;
 
@@ -40,3 +46,155 @@ pub fn get_connection() -> Result<mysql::PooledConn, Box<dyn Error>> {
 
     Ok(pool.get_conn()?)
 }
+
+
+pub struct QueryInfo {
+    /// Fetched table
+    pub table: String,
+
+    /// Query limits
+    pub conditions: collections::HashMap<String, String>,
+
+    /// Limit of the query (0 = no limit)
+    pub limit: u64,
+
+    /// Queried arguments
+    pub fields: Vec<String>,
+}
+
+impl QueryInfo {
+    /// Initialize a new query on the database
+    pub fn new(table: &str) -> QueryInfo {
+        QueryInfo {
+            table: table.to_string(),
+            conditions: collections::HashMap::new(),
+            limit: 0,
+            fields: Vec::new(),
+        }
+    }
+
+    pub fn cond(&mut self, key: &str, val: &str) {
+        self.conditions.insert(key.to_string(), val.to_string());
+    }
+}
+
+/// Struct used to read the result of a request
+pub struct RowResult<'a> {
+    row: &'a mysql::Row
+}
+
+impl<'a> RowResult<'a> {
+    pub fn new(row: &mysql::Row) -> RowResult {
+        RowResult {
+            row
+        }
+    }
+
+    /// Find a column in result set
+    fn find_col(&self, name: &str) -> Result<usize, ExecError> {
+        let name_bytes = name.as_bytes();
+        let mut index = 0;
+        for c in self.row.columns_ref() {
+            if c.name_ref().eq(name_bytes) {
+                return Ok(index);
+            }
+
+            index += 1;
+        }
+
+        Err(ExecError(format!("Column {} not found in database result set!", name)))
+    }
+
+    /// Find an integer included in the request
+    pub fn get_int64(&self, name: &str) -> Result<i64, ExecError> {
+        let value: Option<i64> = self.row.get(self.find_col(name)?);
+
+        match value {
+            None => Err(ExecError(format!("Could not extract integer field {} !", name))),
+            Some(s) => Ok(s)
+        }
+    }
+
+    /// Find a string included in the request
+    pub fn get_str(&self, name: &str) -> Result<String, ExecError> {
+        let value: Option<String> = self.row.get(self.find_col(name)?);
+
+        match value {
+            None => Err(ExecError(format!("Could not extract string field {} !", name))),
+            Some(s) => Ok(s)
+        }
+    }
+}
+
+
+/// Query a single row of the database
+pub fn query_row<E, F: Fn(&RowResult) -> ProcessRowResult<E>>(mut info: QueryInfo,
+                                                              process_function: F) -> Result<E, Box<dyn Error>> {
+    info.limit = 1;
+    let mut list = query(info, process_function)?;
+
+    match list.len() {
+        0 => Err(ExecError::boxed_new("Request did not return a result!")),
+        _ => Ok(list.remove(0))
+    }
+}
+
+/// Make a simple query
+pub fn query<E, F: Fn(&RowResult) -> ProcessRowResult<E>>(info: QueryInfo, process_function: F)
+                                                          -> Result<Vec<E>, Box<dyn Error>> {
+    let mut params = vec![];
+
+    let select_elements = match info.fields.len() {
+        0 => "*".to_string(),
+        _ => info.fields.join(", ")
+    };
+
+    // Build query
+    let mut query = format!("SELECT {} FROM {} ", select_elements, info.table);
+
+
+    // WHERE clause
+    if !info.conditions.is_empty() {
+        let mut where_args = vec![];
+
+        for (k, v) in info.conditions {
+            where_args.push(format!("{} = ?", k));
+            params.push(v)
+        }
+
+        let where_args = format!(" WHERE {} ", where_args.join(" AND "));
+        query = query.add(&where_args);
+    }
+
+    // LIMIT clause
+    if info.limit > 0 {
+        query = query.add(&format!(" LIMIT {}", info.limit));
+    }
+
+    // Execute query
+    let mut con = get_connection()?;
+    let stmt = con.prep(&query)?;
+
+    let mut res = con.exec_iter(stmt, params)?;
+
+    // This system is made to support only one dataset
+    let result_set = res.next_set();
+    if let None = result_set {
+        return Err(Box::new(ExecError::new("No result set in a query!")));
+    }
+    let result_set: ResultSet<Binary> = result_set.unwrap()?;
+
+
+    // Parse each result of the dataset
+    let mut res: Vec<E> = vec![];
+    for row in result_set {
+        let row = row?;
+        let result = RowResult::new(&row);
+
+        let parsed = process_function(&result)?;
+        res.push(parsed);
+    }
+
+
+    Ok(res)
+}

src/main.rs

@@ -1,6 +1,13 @@
 use comunic_server::data::config::{conf, Config};
 use comunic_server::helpers::database;
 use comunic_server::controllers::server;
+use comunic_server::helpers::database::QueryInfo;
+
+#[derive(Debug)]
+struct User {
+    id : i64,
+    name: String,
+}
 
 #[actix_rt::main]
 async fn main() -> std::io::Result<()> {
@@ -11,6 +18,16 @@ async fn main() -> std::io::Result<()> {
     // Connect to the database
     database::connect(&conf().database).expect("Could not connect to database!");
 
+    let mut query = QueryInfo::new("user");
+    query.cond("age", "190");
+    //query.cond("id", "1");
+    let res = database::query_row(query, |res| Ok(User {
+        id: res.get_int64("id")?,
+        name: res.get_str("name")?,
+    })).unwrap();
+
+    println!("{:#?}", res);
+
     // Start the server
     server::start_server(conf()).await
 }