Reimplement most of the tool:

Most of the tool has been reimplemented, with the exception of the
permission editing feature, which is currently half implemented. There
are also several TODOs spread around that would benefit from some action

src/core/config.rs

@@ -0,0 +1,122 @@
+use std::{fs, path::PathBuf};
+
+use anyhow::Context;
+use clap::Parser;
+use serde::{Deserialize, Serialize};
+use sqlx::{mysql::MySqlConnectOptions, ConnectOptions, MySqlConnection};
+
+#[derive(Debug, Clone, Deserialize, Serialize)]
+pub struct Config {
+    pub mysql: MysqlConfig,
+}
+
+#[derive(Debug, Clone, Deserialize, Serialize)]
+#[serde(rename = "mysql")]
+pub struct MysqlConfig {
+    pub host: String,
+    pub port: Option<u16>,
+    pub username: String,
+    pub password: String,
+}
+
+#[derive(Parser)]
+pub struct ConfigOverrideArgs {
+    #[arg(
+      long,
+      value_name = "PATH",
+      global = true,
+      help_heading = Some("Configuration overrides"),
+      hide_short_help = true,
+      alias = "config",
+      alias = "conf",
+    )]
+    config_file: Option<String>,
+
+    #[arg(
+      long,
+      value_name = "HOST",
+      global = true,
+      help_heading = Some("Configuration overrides"),
+      hide_short_help = true,
+    )]
+    mysql_host: Option<String>,
+
+    #[arg(
+      long,
+      value_name = "PORT",
+      global = true,
+      help_heading = Some("Configuration overrides"),
+      hide_short_help = true,
+    )]
+    mysql_port: Option<u16>,
+
+    #[arg(
+      long,
+      value_name = "USER",
+      global = true,
+      help_heading = Some("Configuration overrides"),
+      hide_short_help = true,
+    )]
+    mysql_user: Option<String>,
+
+    #[arg(
+      long,
+      value_name = "PATH",
+      global = true,
+      help_heading = Some("Configuration overrides"),
+      hide_short_help = true,
+    )]
+    mysql_password_file: Option<String>,
+}
+
+pub fn get_config(args: ConfigOverrideArgs) -> anyhow::Result<Config> {
+    let config_path = args
+        .config_file
+        .unwrap_or("/etc/mysqladm/config.toml".to_string());
+    let config_path = PathBuf::from(config_path);
+
+    let config: Config = fs::read_to_string(&config_path)
+        .context(format!(
+            "Failed to read config file from {:?}",
+            &config_path
+        ))
+        .and_then(|c| toml::from_str(&c).context("Failed to parse config file"))
+        .context(format!(
+            "Failed to parse config file from {:?}",
+            &config_path
+        ))?;
+
+    let mysql = &config.mysql;
+
+    let password = if let Some(path) = args.mysql_password_file {
+        fs::read_to_string(path)
+            .context("Failed to read MySQL password file")
+            .map(|s| s.trim().to_owned())?
+    } else {
+        mysql.password.to_owned()
+    };
+
+    let mysql_config = MysqlConfig {
+        host: args.mysql_host.unwrap_or(mysql.host.to_owned()),
+        port: args.mysql_port.or(mysql.port),
+        username: args.mysql_user.unwrap_or(mysql.username.to_owned()),
+        password,
+    };
+
+    Ok(Config {
+        mysql: mysql_config,
+    })
+}
+
+/// TODO: Add timeout.
+pub async fn mysql_connection_from_config(config: Config) -> anyhow::Result<MySqlConnection> {
+    MySqlConnectOptions::new()
+        .host(&config.mysql.host)
+        .username(&config.mysql.username)
+        .password(&config.mysql.password)
+        .port(config.mysql.port.unwrap_or(3306))
+        .database("mysql")
+        .connect()
+        .await
+        .context("Failed to connect to MySQL")
+}