add derive macros

3 files changed, 151 insertions, 0 deletions

diff --git a/confondant_derive/.gitignore b/confondant_derive/.gitignore
new file mode 100644
index 0000000..088ba6b
--- /dev/null
+++ b/confondant_derive/.gitignore
@@ -0,0 +1,10 @@
+# Generated by Cargo
+# will have compiled files and executables
+/target/
+
+# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
+# More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
+Cargo.lock
+
+# These are backup files generated by rustfmt
+**/*.rs.bk
diff --git a/confondant_derive/Cargo.toml b/confondant_derive/Cargo.toml
new file mode 100644
index 0000000..4b94b57
--- /dev/null
+++ b/confondant_derive/Cargo.toml
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+[package]
+name = "confondant_derive"
+version = "0.1.0"
+authors = ["Akshay <[email protected]>"]
+edition = "2018"
+
+[dependencies]
+proc-macro2 = "1.0.9"
+quote = "1.0"
+
+[dependencies.syn]
+version = "1.0"
+features = ["full"]
+
+[lib]
+proc-macro = true
diff --git a/confondant_derive/src/lib.rs b/confondant_derive/src/lib.rs
new file mode 100644
index 0000000..076a66e
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+++ b/confondant_derive/src/lib.rs
@@ -0,0 +1,125 @@
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+use proc_macro2::Span;
+use quote::quote;
+use syn::{parse_macro_input, DeriveInput, Error, Ident, Lit, Meta, MetaNameValue, Result};
+
+#[proc_macro_derive(Config, attributes(filename, extension))]
+pub fn config_attribute(item: TokenStream) -> TokenStream {
+    let ast: DeriveInput = parse_macro_input!(item as DeriveInput);
+    let (filename, filetype) = extract_attributes(&ast);
+
+    gen_impl(
+        &ast,
+        filename.unwrap_or("config".into()),
+        filetype.unwrap_or("toml".into()),
+    )
+}
+
+fn extract_attributes(ast: &DeriveInput) -> (Option<String>, Option<String>) {
+    let mut filename: Option<String> = None;
+    let mut filetype: Option<String> = None;
+    for option in ast.attrs.iter() {
+        let option = option.parse_meta().unwrap();
+        match option {
+            Meta::NameValue(MetaNameValue {
+                ref path, ref lit, ..
+            }) if path.is_ident("filename") => {
+                if let Lit::Str(f) = lit {
+                    filename = Some(f.value());
+                }
+            }
+            Meta::NameValue(MetaNameValue {
+                ref path, ref lit, ..
+            }) if path.is_ident("extension") => {
+                if let Lit::Str(f) = lit {
+                    filetype = Some(f.value());
+                }
+            }
+            _ => {}
+        }
+    }
+    return (filename, filetype);
+}
+
+fn map_ser(ext: &str) -> (Ident, Ident) {
+    match ext.as_ref() {
+        "toml" => (
+            Ident::new("toml", Span::call_site()),
+            Ident::new("to_string_pretty", Span::call_site()),
+        ),
+        "yaml" => (
+            Ident::new("serde_yaml", Span::call_site()),
+            Ident::new("to_string", Span::call_site()),
+        ),
+        "json" => (
+            Ident::new("serde_json", Span::call_site()),
+            Ident::new("to_string_pretty", Span::call_site()),
+        ),
+        _ => panic!("Invalid extension!"),
+    }
+}
+
+fn gen_impl(ast: &DeriveInput, filename: String, filetype: String) -> TokenStream {
+    let struct_name = &ast.ident.to_string();
+    let struct_ident = &ast.ident;
+    let (ser, ser_fn) = map_ser(&filetype);
+
+    let gen = quote! {
+        use ::confondant::{ ProjectDirs, toml, serde_json, serde_yaml, FondantError };
+        use ::std::path::{ Path, PathBuf };
+        use ::std::option::Option;
+        use ::std::fs::{self, File, OpenOptions};
+        use ::std::io::prelude::*;
+        use ::std::io::{ ErrorKind::NotFound, Write };
+
+        impl Config for #struct_ident {
+            fn load() -> Result<#struct_ident, FondantError> {
+                let project = ProjectDirs::from("rs", "", #struct_name).ok_or(FondantError::InvalidHomeDir)?;
+                let config_dir = project.config_dir();
+
+                let tip = (Path::new(#filename)).with_extension(&#filetype);
+                let config_file: PathBuf = [config_dir, &tip].iter().collect();
+
+                match File::open(&config_file) {
+                    Ok(mut cfg) => {
+                        // the file exists, parse the toml and return the struct
+                        let mut cfg_data = String::new();
+                        cfg.read_to_string(&mut cfg_data);
+
+                        let config: #struct_ident = #ser::from_str(&cfg_data[..])
+                            .map_err(|_| FondantError::ConfigParseError)?;
+                        return Ok(config);
+                    },
+                    Err(ref e) if e.kind() == NotFound => {
+                        fs::create_dir_all(project.config_dir());
+                        let default_impl = #struct_ident::default();
+                        Config::store(&default_impl)?;
+                        return Ok(default_impl);
+                    },
+                    Err(e) => return Err(FondantError::LoadError),
+                };
+            }
+            fn store(&self) -> Result<(), FondantError> {
+                let project = ProjectDirs::from("rs", "", #struct_name).ok_or(FondantError::InvalidHomeDir)?;
+                let config_dir = project.config_dir();
+
+                let tip = (Path::new(#filename)).with_extension(&#filetype);
+                let config_file: PathBuf = [config_dir, &tip].iter().collect();
+
+                let mut f = OpenOptions::new()
+                    .write(true)
+                    .create(true)
+                    .truncate(true)
+                    .open(config_file)
+                    .map_err(|_| FondantError::FileOpenError)?;
+
+                let s = #ser::#ser_fn(self).map_err(|_| FondantError::ConfigParseError)?;
+                f.write_all(s.as_bytes()).map_err(|_| FondantError::FileWriteError);
+                Ok(())
+            }
+        }
+    };
+    gen.into()
+}