making it usable from cli

Cargo.lock

@@ -58,6 +58,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b97f376d85a664d5837dbae44bf546e6477a679ff6610010f17276f686d867e8"
 dependencies = [
  "clap_builder",
+ "clap_derive",
 ]
 
 [[package]]
@@ -72,6 +73,18 @@ dependencies = [
  "strsim",
 ]
 
+[[package]]
+name = "clap_derive"
+version = "4.5.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4ac6a0c7b1a9e9a5186361f67dfa1b88213572f427fb9ab038efb2bd8c582dab"
+dependencies = [
+ "heck",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "clap_lex"
 version = "0.7.2"
@@ -99,6 +112,12 @@ version = "2.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "19d374276b40fb8bbdee95aef7c7fa6b5316ec764510eb64b8dd0e2ed0d7e7f5"
 
+[[package]]
+name = "heck"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2304e00983f87ffb38b55b444b5e3b60a884b5d30c0fca7d82fe33449bbe55ea"
+
 [[package]]
 name = "is_terminal_polyfill"
 version = "1.70.1"
@@ -113,12 +132,47 @@ dependencies = [
  "crc",
 ]
 
+[[package]]
+name = "proc-macro2"
+version = "1.0.89"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f139b0662de085916d1fb67d2b4169d1addddda1919e696f3252b740b629986e"
+dependencies = [
+ "unicode-ident",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.37"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b5b9d34b8991d19d98081b46eacdd8eb58c6f2b201139f7c5f643cc155a633af"
+dependencies = [
+ "proc-macro2",
+]
+
 [[package]]
 name = "strsim"
 version = "0.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7da8b5736845d9f2fcb837ea5d9e2628564b3b043a70948a3f0b778838c5fb4f"
 
+[[package]]
+name = "syn"
+version = "2.0.85"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5023162dfcd14ef8f32034d8bcd4cc5ddc61ef7a247c024a33e24e1f24d21b56"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
+[[package]]
+name = "unicode-ident"
+version = "1.0.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e91b56cd4cadaeb79bbf1a5645f6b4f8dc5bde8834ad5894a8db35fda9efa1fe"
+
 [[package]]
 name = "utf8parse"
 version = "0.2.2"

Cargo.toml

@@ -5,4 +5,4 @@ edition = "2021"
 
 [dependencies]
 crc = "3.2.1"
-clap = "4.5.20"
+clap = { version = "4.5.20", features = ["derive"] }

src/args.rs

@@ -0,0 +1,39 @@
+use clap::{Parser, ValueEnum};
+
+#[derive(Parser, Debug)]
+#[command(version, about)]
+pub struct Args {
+    #[arg(long, value_enum, required = true)]
+    pub mode: Mode,
+
+    #[arg(
+        short,
+        long,
+        required = true,
+    )]
+    pub input_file: Option<String>,
+
+    #[arg(
+        short,
+        long,
+        required_if_eq("mode", "Mode::Encode"),
+        required_if_eq("mode", "Mode::Decode"),
+        required_if_eq("mode", "Mode::Remove")
+    )]
+    pub chunk_type: Option<String>,
+
+    #[arg(
+        short,
+        long,
+        required_if_eq("mode", "Mode::Encode")
+    )]
+    pub message: Option<String>,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, ValueEnum)]
+pub enum Mode {
+    Encode,
+    Decode,
+    Print,
+    Remove
+}

src/main.rs

@@ -4,9 +4,58 @@ mod chunk_type;
 mod commands;
 mod png;
 
+use core::panic;
+use std::path::PathBuf;
+use std::fs::File;
+
+use args::Mode;
+use chunk_type::ChunkType;
+use clap::Parser;
+use crate::args::Args;
+
 pub type Error = Box<dyn std::error::Error>;
 pub type Result<T> = std::result::Result<T, Error>;
 
-fn main() -> Result<()> {
+fn get_image(path: &str) -> File {
+    let image_path: PathBuf = PathBuf::from(path);
+    let path_display = image_path.display();
+
+    let image = match File::open(&image_path) {
+        Err(why) => panic!("couldn't open {}: {}", path_display, why),
+        Ok(file) => file
+    };
+
+    image
+}
+
+fn encode(image: File, chunk_type: ChunkType, message: &str) {
     todo!()
 }
+
+fn decode(image: File, chunk_type: ChunkType) {
+    todo!()
+}
+
+fn print_message(image: File) {
+    todo!()
+}
+
+fn remove_message(image: File, chunk_type: ChunkType) {
+    todo!()
+}
+
+fn main() -> Result<()> {
+    let args = Args::parse();
+
+    let image = get_image(&args.input_file.unwrap());
+
+    match args.mode {
+        Mode::Encode    => todo!(),
+        Mode::Decode    => todo!(),
+        Mode::Print     => todo!(),
+        Mode::Remove    => todo!(),
+        _               => Err("not a valid mode")?
+    }
+
+    Ok(())
+}