Add Go version module (#44)

src/modules/go.rs

@@ -0,0 +1,96 @@
+use ansi_term::Color;
+use std::path::PathBuf;
+use std::process::Command;
+
+use super::{Context, Module};
+
+/// Creates a segment with the current Python version
+///
+/// Will display the Python version if any of the following criteria are met:
+///     - Current directory contains a `.go` file
+///     - Current directory contains a `go.mod` file
+///     - Current directory contains a `go.sum` file
+///     - Current directory contains a `Godeps` directory
+///     - Current directory contains a `glide.yaml` file
+///     - Current directory contains a `Gopkg.yml` file
+///     - Current directory contains a `Gopkg.lock` file
+pub fn segment(context: &Context) -> Option<Module> {
+    let is_go_project = context.dir_files.iter().any(has_go_files);
+    if !is_go_project {
+        return None;
+    }
+
+    const GO_CHAR: &str = "🐹 ";
+    let module_color = Color::Cyan.bold();
+
+    let mut module = Module::new("go");
+    module.set_style(module_color);
+
+    let go_version = get_go_version()?;
+    let formatted_version = format_go_version(go_version)?;
+    module.new_segment("symbol", GO_CHAR);
+    module.new_segment("version", formatted_version);
+
+    Some(module)
+}
+
+fn has_go_files(dir_entry: &PathBuf) -> bool {
+    let is_go_mod =
+        |d: &PathBuf| -> bool { d.is_file() && d.file_name().unwrap_or_default() == "go.mod" };
+    let is_go_sum =
+        |d: &PathBuf| -> bool { d.is_file() && d.file_name().unwrap_or_default() == "go.sum" };
+    let is_godeps =
+        |d: &PathBuf| -> bool { d.is_dir() && d.file_name().unwrap_or_default() == "Godeps" };
+    let is_glide_yaml =
+        |d: &PathBuf| -> bool { d.is_file() && d.file_name().unwrap_or_default() == "glide.yaml" };
+    let is_go_file =
+        |d: &PathBuf| -> bool { d.is_file() && d.extension().unwrap_or_default() == "go" };
+    let is_gopkg_yml =
+        |d: &PathBuf| -> bool { d.is_file() && d.file_name().unwrap_or_default() == "Gopkg.yml" };
+    let is_gopkg_lock =
+        |d: &PathBuf| -> bool { d.is_file() && d.file_name().unwrap_or_default() == "Gopkg.lock" };
+
+    is_go_mod(&dir_entry)
+        || is_go_sum(&dir_entry)
+        || is_godeps(&dir_entry)
+        || is_glide_yaml(&dir_entry)
+        || is_go_file(&dir_entry)
+        || is_gopkg_yml(&dir_entry)
+        || is_gopkg_lock(&dir_entry)
+}
+
+fn get_go_version() -> Option<String> {
+    Command::new("go")
+        .arg("version")
+        .output()
+        .ok()
+        .and_then(|output| String::from_utf8(output.stdout).ok())
+}
+
+fn format_go_version(go_stdout: String) -> Option<String> {
+    let mut version = go_stdout
+        // split into ["", "1.12.4 linux/amd64"]
+        .splitn(2, "go version go")
+        // return "1.12.4 linux/amd64"
+        .nth(1)?
+        // split into ["1.12.4", "linux/amd64"]
+        .split_whitespace()
+        // return "1.12.4"
+        .next()?;
+
+    let mut formatted_version = String::with_capacity(version.len() + 1);
+    formatted_version.push('v');
+    formatted_version.push_str(version);
+    Some(formatted_version)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_format_go_version() {
+        let input = String::from("go version go1.12 darwin/amd64");
+        assert_eq!(format_go_version(input), Some("v1.12".to_string()));
+    }
+}