sqlite select and inserts with guards

.gitignore

@@ -4,3 +4,4 @@ members/c-bindings/lib/cmake_install.cmake
 members/c-bindings/lib/libtest.so
 members/c-bindings/lib/libtest.so.1
 members/c-bindings/lib/libtest.so.1.0.1
+members/sqlite-demo/data/cats.db

members/sqlite-demo/src/main.rs

@@ -1,34 +1,116 @@
+use std::path::PathBuf;
+use std::{env, fs};
+
 use anyhow::Ok;
 /// This demo application uses a sqlite file to store some data. It does *not* use ORM (that would
 /// be done with the `diesel` crate.)!
 ///
 /// A very useful ressource is the
 /// [rust-cookbook](https://rust-lang-nursery.github.io/rust-cookbook/database/sqlite.html).
-use rusqlite::{Connection, Result};
+use rusqlite::Connection;
+
+const DBNAME: &str = "cats.db";
+const TABLE_CAT_COLOR: &str = "cat_colors";
+const TABLE_CAT: &str = "cats";
+
+fn connect() -> anyhow::Result<Connection> {
+    let mut wd = env::current_dir()?;
+    let mut dbpath: Option<PathBuf> = None;
+
+    // does the current directory have a data/cats.db ? (the file need not exist, we can create it
+    // if data exists)
+    {
+        let mut wddata = wd.clone();
+        wddata.push("data");
+        if wddata.exists() {
+            println!("found {DBNAME} in {:?}", &wddata);
+            wddata.push(DBNAME);
+            dbpath = Some(wddata);
+        }
+    }
+
+    // otherwise, does the current or any higher directories contain a cats.db ?
+    'search_dir: while dbpath.is_none() {
+        for entry in fs::read_dir(&wd)? {
+            let entry = entry?;
+            if entry.file_name() == DBNAME {
+                println!("found {DBNAME} in {:?}", wd);
+                dbpath = Some(entry.path());
+                break 'search_dir;
+            }
+        }
+        if !wd.pop() {
+            // we are at the root!
+            break 'search_dir;
+        }
+    }
+
+    // if all fails, use $PWD/data/cats.db
+    if dbpath.is_none() {
+        println!(
+            "No {DBNAME} found, using {:?}/data/{DBNAME}",
+            env::current_dir()?
+        );
+        fs::create_dir("data")?;
+        let mut path = env::current_dir()?;
+        path.push("data");
+        path.push(DBNAME);
+        dbpath = Some(path);
+    }
+
+    let conn = Connection::open(dbpath.unwrap())?;
+
+    Ok(conn)
+}
 
 fn setup(conn: &Connection) -> anyhow::Result<()> {
     conn.execute(
-        "create table if not exists cat_colors (
+        &format!(
-             id integer primary key,
+            "CREATE TABLE IF NOT EXISTS {TABLE_CAT_COLOR} (
-             name text not null unique
+             id INTEGER PRIMARY KEY,
-         )",
+             name TEXT NOT NULL UNIQUE COLLATE NOCASE
+         )"
+        ),
         (),
     )?;
     conn.execute(
-        "create table if not exists cats (
+        &format!(
-             id integer primary key,
+            "CREATE TABLE IF NOT EXISTS {TABLE_CAT} (
-             name text not null,
+             id INTEGER PRIMARY KEY,
-             color_id integer not null references cat_colors(id)
+             name TEXT NOT NULL COLLATE NOCASE,
-         )",
+             COLOR_ID INTEGER NOT NULL REFERENCES CAT_COLORS(ID)
+         )"
+        ),
         (),
     )?;
 
     Ok(())
 }
 
+/// Add a new color to the cat_colors table
+///
+/// Will fail if the sql fails
+///
+/// If the color already exists, will return Ok(())
+///
+/// The table stores the name in lowercase
 fn new_color(conn: &Connection, color: &str) -> anyhow::Result<()> {
+    // check if the color already exists, so we can just try adding a color and not worry if it
+    // already exists
+
+    let mut stmt = conn.prepare(&format!(
+        "SELECT EXISTS( SELECT 1 FROM {TABLE_CAT_COLOR} WHERE name = (?1))"
+    ))?;
+    if let Some(row) = stmt.query([color.to_string()])?.next()? {
+        if row.get::<usize, usize>(0)? == 1 {
+            // the color already exists
+            return Ok(());
+        }
+    };
+
+    // do the inserting
     conn.execute(
-        "INSERT INTO cat_colors (name) values (?1)",
+        "INSERT INTO cat_colors (name) VALUES (?1)",
         [color.to_string()],
     )?;
 
@@ -36,11 +118,12 @@ fn new_color(conn: &Connection, color: &str) -> anyhow::Result<()> {
 }
 
 fn main() -> anyhow::Result<()> {
-    let conn = Connection::open("cats.db")?;
+    let conn = connect()?;
 
     setup(&conn)?;
     new_color(&conn, "black")?;
     new_color(&conn, "red")?;
+    new_color(&conn, "white")?;
 
     Ok(())
 }