3 files changed, 136 insertions, 0 deletions

diff --git a/Cargo.lock b/Cargo.lock
index aa25765..5cd0345 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -127,6 +127,12 @@ dependencies = [
 ]
 
 [[package]]
+name = "pico-args"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d70072c20945e1ab871c472a285fc772aefd4f5407723c206242f2c6f94595d6"
+
+[[package]]
 name = "radium"
 version = "0.6.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -156,6 +162,7 @@ dependencies = [
  "env_logger",
  "log",
  "obi",
+ "pico-args",
  "sdl2",
 ]
 
diff --git a/Cargo.toml b/Cargo.toml
index 277d6b0..ce5d614 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -11,3 +11,4 @@ sdl2 = {version = "0.34", features = ["ttf"]}
 obi = { git = "https://github.com/nerdypepper/obi" }
 env_logger = "0.8.3"
 log = "0.4.0"
+pico-args = "0.4.0"
diff --git a/src/cli.rs b/src/cli.rs
new file mode 100644
index 0000000..1dbd098
--- /dev/null
+++ b/src/cli.rs
@@ -0,0 +1,128 @@
+use std::{
+    default::Default,
+    fmt,
+    path::{Path, PathBuf},
+};
+
+pub static HELP_TEXT: &'static str = "
+Usage
+-----
+
+slate new <FILE> -d WIDTHxHEIGHT
+
+Options
+-------
+
+    -h, --help      Prints help information
+    -d,             Specify dimensions for new file (default: 200x200)
+";
+
+#[derive(Debug)]
+pub enum CliError {
+    NoDimensions,
+    FileAlreadyExists,
+    FileDoesNotExist,
+    DimensionParseError,
+    NewRequiresFile,
+    InvalidSubCommand(String),
+    SubCommandParseError,
+}
+
+impl fmt::Display for CliError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::NoDimensions => write!(f, "no dimensions provided"),
+            Self::FileAlreadyExists => {
+                write!(f, "cannot initialize project, file already exists")
+            }
+            Self::FileDoesNotExist => {
+                write!(f, "cannot open existing project, file does not exist")
+            }
+            Self::DimensionParseError => write!(f, "invalid dimension string"),
+            Self::NewRequiresFile => write!(f, "new subcommand requires file name"),
+            Self::InvalidSubCommand(s) => write!(f, "invalid subcommand `{}`", s),
+            Self::SubCommandParseError => write!(f, "error parsing subcommand"),
+        }
+    }
+}
+
+impl std::error::Error for CliError {}
+
+#[derive(Debug)]
+pub enum Config {
+    NewProject {
+        file_name: Option<PathBuf>,
+        dimensions: (u32, u32),
+    },
+    ExistingProject {
+        file_name: PathBuf,
+    },
+    Help,
+}
+
+impl Default for Config {
+    fn default() -> Self {
+        Self::NewProject {
+            file_name: None,
+            dimensions: (200, 200),
+        }
+    }
+}
+
+pub fn parse_args() -> Result<Config, CliError> {
+    let mut args = pico_args::Arguments::from_env();
+
+    if args.contains(["-h", "--help"]) {
+        return Ok(Config::Help);
+    }
+
+    match args.subcommand() {
+        Ok(cmd) => match cmd.as_deref() {
+            Some("new") => new_project(&mut args),
+            Some(s) => {
+                if !Path::new(s).is_file() {
+                    return Err(CliError::FileDoesNotExist);
+                }
+                return Ok(Config::ExistingProject {
+                    file_name: PathBuf::from(s),
+                });
+            }
+            None => return Ok(Config::Help),
+        },
+        _ => Err(CliError::SubCommandParseError),
+    }
+}
+
+fn new_project(args: &mut pico_args::Arguments) -> Result<Config, CliError> {
+    let file_name = args.free_from_str();
+    if let Ok(f) = &file_name {
+        if Path::new(&f).is_file() {
+            return Err(CliError::FileAlreadyExists);
+        }
+    }
+    let dimensions = args
+        .opt_value_from_fn(["-d", "--dimensions"], parse_dimensions)
+        .map_err(|_| CliError::DimensionParseError)?
+        .unwrap_or((200, 200));
+    return Ok(Config::NewProject {
+        file_name: file_name.ok(),
+        dimensions,
+    });
+}
+
+fn parse_dimensions(input: &str) -> Result<(u32, u32), CliError> {
+    let dimensions: Vec<&str> = input.split('x').collect();
+    match &dimensions[..] {
+        [width, height] => {
+            return Ok((
+                width
+                    .parse::<u32>()
+                    .map_err(|_| CliError::DimensionParseError)?,
+                height
+                    .parse::<u32>()
+                    .map_err(|_| CliError::DimensionParseError)?,
+            ))
+        }
+        _ => return Err(CliError::DimensionParseError),
+    }
+}