cli: work on basic cli and serde error hanlding

crates/app/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "app"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+clap = { workspace = true, features = [ "derive" ] }
+serde = { workspace = true, features = [ "derive" ] }
+ron = { workspace = true }
+serde_json = { workspace = true } 
+ariadne = "0.4"

crates/app/src/main.rs

@@ -0,0 +1,73 @@
+use crate::{config::Configs, error_reporting::report_serde_json_err};
+
+mod cli {
+    use clap::{Parser, Subcommand};
+
+    #[derive(Parser)]
+    struct Args {
+        #[command(subcommand)]
+        command: Command,
+    }
+
+    #[derive(Clone, Subcommand)]
+    enum Command {}
+}
+
+mod config {
+    use serde::{Deserialize, Serialize};
+
+    #[derive(Debug, Serialize, Deserialize)]
+    pub struct Configs<'a> {
+        example_value: i32,
+        example_string: &'a str,
+    }
+
+    impl Configs<'_> {
+        pub fn read_json(config_text: &str) -> serde_json::Result<Configs<'_>> {
+            serde_json::from_str(config_text)
+        }
+    }
+}
+
+mod error_reporting {
+    use std::{ops::Range, process};
+
+    use ariadne::{Report, Source};
+
+    pub fn report_serde_json_err(src: &str, err: serde_json::Error) -> ! {
+        use ariadne::{Color, ColorGenerator, Fmt, Label, Report, ReportKind, Source};
+        let offset = try_reconstruct_loc(src, err.line(), err.column());
+
+        Report::build(ariadne::ReportKind::Error, "test", offset)
+            .with_label(Label::new(("test", offset..offset)))
+            .with_message(err.to_string())
+            .finish()
+            .print(("test", Source::from(src)))
+            .unwrap();
+        process::exit(1);
+    }
+    fn try_reconstruct_loc(src: &str, line_nr: usize, col_nr: usize) -> usize {
+        let (line_nr, col_nr) = (line_nr - 1, col_nr - 1);
+
+        src.lines().enumerate().fold(0, |acc, (i, line)| {
+            if i < line_nr {
+                acc + line.len()
+            } else if i == line_nr {
+                acc + col_nr
+            } else {
+                acc
+            }
+        })
+    }
+}
+
+fn main() {
+    const TEST_JSON_CONFIG: &str = "{ \"example_value\": 42, \"example_string\": \"meow\" }";
+    const TEST_JSON_CONFIG_BROKEN: &str = "{ 
+    \"example_value\": \"42\", 
+    \"example_string\": \"meow\" 
+}";
+
+    dbg!(Configs::read_json(TEST_JSON_CONFIG_BROKEN)
+        .map_err(|e| report_serde_json_err(TEST_JSON_CONFIG_BROKEN, e)));
+}