begin dependency feature

Signed-off-by: Luke-zhang-04 <luke.zhang2004dev@gmail.com>

src/onefetch/deps.rs

@@ -0,0 +1,48 @@
+use {
+    crate::onefetch::error::*,
+    std::{ffi::OsStr, fs},
+    std::collections::HashMap,
+};
+
+mod Parsers {
+    fn npm(contents: &str) -> i32 {
+        println!(contents)
+        return 0
+    }
+}
+
+
+type DependencyParser = fn(&str) -> i32;
+let package_managers: HashMap<&str, (&str, DependencyParser)> = [
+    ("npm", ("package.json", Parsers.npm)),
+].iter().cloned().collect();
+
+pub struct Detector {}
+
+impl Detector {
+    pub fn get_dep_count(&self, dir: &str) -> Result<String> {
+        fn is_package_file<S: AsRef<str>>(file_name: S) -> bool {
+            package_managers
+                .iter()
+                .any(|&info| file_name.as_ref().starts_with(info[0]))
+        }
+
+        let mut package_files = fs::read_dir(dir)
+            .chain_err(|| "Could not read directory")?
+            .filter_map(std::result::Result::ok)
+            .map(|entry| entry.path())
+            .filter(|entry| {
+                entry.is_file()
+                    && entry
+                        .file_name()
+                        .map(OsStr::to_string_lossy)
+                        .map(is_package_file)
+                        .unwrap_or_default()
+            })
+            .filter_map(|entry| {
+                let contents = fs::read_to_string(entry).unwrap_or_default();
+                self.analyze(&contents)
+            })
+            .collect::<Vec<_>>();
+    }
+}