Add Filesystem layer for loading files from FS without parsing

Signed-off-by: Matthias Beyer <matthias.beyer@atos.net>

2 files changed, 120 insertions, 0 deletions

diff --git a/src/repository/fs.rs b/src/repository/fs.rs
new file mode 100644
index 0000000..6cfd2ff
--- /dev/null
+++ b/src/repository/fs.rs
@@ -0,0 +1,117 @@
+use std::path::Path;
+use std::path::PathBuf;
+use std::collections::HashMap;
+use std::path::Component;
+use std::convert::TryFrom;
+
+use walkdir::DirEntry;
+use walkdir::WalkDir;
+use anyhow::anyhow;
+use anyhow::Context;
+use anyhow::Result;
+use anyhow::Error;
+use resiter::Map;
+use resiter::AndThen;
+
+pub struct FileSystemRepresentation {
+    root: PathBuf,
+    elements: HashMap<PathComponent, Element>,
+}
+
+enum Element {
+    File(String),
+    Dir(HashMap<PathComponent, Element>)
+}
+
+impl Element {
+    fn get_map_mut(&mut self) -> Option<&mut HashMap<PathComponent, Element>> {
+        match self {
+            Element::File(_) => None,
+            Element::Dir(ref mut hm) => Some(hm),
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Hash)]
+enum PathComponent {
+    PkgToml,
+    DirName(String),
+}
+
+impl TryFrom<&std::path::Component<'_>> for PathComponent {
+    type Error = anyhow::Error;
+
+    fn try_from(c: &std::path::Component) -> Result<Self> {
+        match *c {
+            Component::Prefix(_) => anyhow::bail!("Unexpected path component: Prefix"),
+            Component::RootDir => anyhow::bail!("Unexpected path component: RootDir"),
+            Component::CurDir => anyhow::bail!("Unexpected path component: CurDir"),
+            Component::ParentDir => anyhow::bail!("Unexpected path component: ParentDir"),
+            Component::Normal(filename) => {
+                let filename = filename.to_str().ok_or_else(|| anyhow!("UTF8-error"))?;
+                if filename == "pkg.toml" {
+                    Ok(PathComponent::PkgToml)
+                } else {
+                    Ok(PathComponent::DirName(filename.to_string()))
+                }
+            },
+        }
+    }
+}
+
+
+impl FileSystemRepresentation {
+    pub fn load(root: PathBuf) -> Result<Self> {
+        let mut fsr = FileSystemRepresentation {
+            root: root.clone(),
+            elements: HashMap::new(),
+        };
+
+        WalkDir::new(root)
+            .follow_links(false)
+            .max_open(100)
+            .same_file_system(true)
+            .into_iter()
+            .filter_entry(|e| is_pkgtoml(e))
+            .inspect(|el| log::trace!("Loading: {:?}", el))
+            .map_err(Error::from)
+            .and_then_ok(|de| {
+                let mut curr_hm = &mut fsr.elements;
+
+                // traverse the HashMap tree
+                for cmp in de.path().components() {
+                    match PathComponent::try_from(&cmp)? {
+                        PathComponent::PkgToml => {
+                            curr_hm.entry(PathComponent::PkgToml)
+                                .or_insert(Element::File(load_file(de.path())?));
+                        },
+                        dir @ PathComponent::DirName(_) => {
+                            curr_hm.entry(dir.clone())
+                                .or_insert(Element::Dir(HashMap::new()));
+
+                            curr_hm = curr_hm.get_mut(&dir)
+                                .unwrap() // safe, because we just inserted it
+                                .get_map_mut()
+                                .unwrap(); // safe, because we inserted Element::Dir
+                        },
+                    }
+                }
+
+                Ok(())
+            })
+            .collect::<Result<Vec<_>>>()?;
+
+        Ok(fsr)
+    }
+}
+
+fn is_pkgtoml(entry: &DirEntry) -> bool {
+    entry.file_name().to_str().map(|s| s == "pkg.toml").unwrap_or(false)
+}
+
+fn load_file(path: &Path) -> Result<String> {
+    std::fs::read_to_string(path)
+        .with_context(|| anyhow!("Reading file from filesystem: {}", path.display()))
+        .map_err(Error::from)
+}
+
diff --git a/src/repository/mod.rs b/src/repository/mod.rs
index ca24117..63276e4 100644
--- a/src/repository/mod.rs
+++ b/src/repository/mod.rs
@@ -11,3 +11,6 @@
 #![allow(clippy::module_inception)]
 mod repository;
 pub use repository::*;
+
+mod fs;
+