feat: add read-only PostgreSQL inspection TUI

src/main.rs

@@ -0,0 +1,87 @@
+mod app;
+mod db;
+
+use std::{error::Error, io::IsTerminal, process::ExitCode};
+
+type Result<T, E = Box<dyn Error>> = std::result::Result<T, E>;
+
+const HELP: &str = r#"dbdash — read-only PostgreSQL inspection
+
+Usage:
+  dbdash [POSTGRES_CONNECTION_STRING]
+  dbdash --help
+
+With no argument, the connection is read from DATABASE_URL.
+Prefer the environment variable to keep passwords out of process arguments:
+  export DATABASE_URL='postgresql://user@localhost:5432/database'
+  cargo run
+
+PostgreSQL URLs and libpq-style key=value strings are accepted.
+Use sslmode=require for mandatory TLS; certificates and hostnames are verified.
+Use sslmode=disable only for trusted local connections.
+The terminal must be at least 70 columns wide and 12 lines high.
+
+Navigation:
+  Tab / Esc     Switch focus / return to relations
+  Up/Down, j/k  Move selection (Enter opens a relation)
+  Home/End, g/G First / last item
+  s             Toggle rows and column schema
+  Left/Right    Scroll columns (h/l also work)
+  n/p, PgDn/Up  Next / previous 100-row page
+  r             Refresh relations and the active relation
+  q / Ctrl-C    Quit
+
+Reads are enforced read-only by PostgreSQL and have a 5-second query timeout.
+The interface waits for reads to complete. NULL cells are dimmed.
+Pages use primary-key order, or physical order for keyless tables.
+Keyless views have no guaranteed order; concurrent changes can shift pages.
+"#;
+
+fn main() -> ExitCode {
+    match run() {
+        Ok(()) => ExitCode::SUCCESS,
+        Err(error) => {
+            eprintln!("dbdash: {}", error_text(error.as_ref()));
+            ExitCode::FAILURE
+        }
+    }
+}
+
+fn run() -> Result<()> {
+    let mut args = std::env::args_os().skip(1);
+    let connection = match args.next() {
+        Some(argument) if argument == "--help" || argument == "-h" => {
+            print!("{HELP}");
+            return Ok(());
+        }
+        Some(argument) => argument
+            .into_string()
+            .map_err(|_| "connection string must be UTF-8")?,
+        None => std::env::var("DATABASE_URL")
+            .map_err(|_| "set DATABASE_URL or pass a connection string; see dbdash --help")?,
+    };
+    if args.next().is_some() {
+        return Err("expected one connection string; see dbdash --help".into());
+    }
+    if !std::io::stdin().is_terminal() || !std::io::stdout().is_terminal() {
+        return Err("an interactive terminal is required; see dbdash --help".into());
+    }
+    let mut app = app::App::new(db::Database::connect(&connection)?)?;
+    let result = (|| {
+        let mut terminal = ratatui::try_init()?;
+        app.run(&mut terminal)
+    })();
+    ratatui::restore();
+    result
+}
+
+fn error_text(error: &(dyn Error + 'static)) -> String {
+    let mut text = error.to_string();
+    let mut source = error.source();
+    while let Some(error) = source {
+        text.push_str(": ");
+        text.push_str(&error.to_string());
+        source = error.source();
+    }
+    db::display_text(&text)
+}