From feaa32196b83d060ba19df498dd0fc13b5d96e9b Mon Sep 17 00:00:00 2001
From: Matthias Beyer <mail@beyermatthias.de>
Date: Thu, 4 Jan 2018 23:09:30 +0100
Subject: [PATCH] Refactoring: Use function chaining rather than matching

Also introduce error links for this.
---
 .../libimagentrycategory/src/category.rs      | 23 +++++++-------
 lib/entry/libimagentrycategory/src/error.rs   |  8 +++++
 .../libimagentrycategory/src/register.rs      | 30 +++++++++----------
 3 files changed, 34 insertions(+), 27 deletions(-)

diff --git a/lib/entry/libimagentrycategory/src/category.rs b/lib/entry/libimagentrycategory/src/category.rs
index f2a2b2cf..5cef0d6d 100644
--- a/lib/entry/libimagentrycategory/src/category.rs
+++ b/lib/entry/libimagentrycategory/src/category.rs
@@ -19,7 +19,6 @@
 
 use toml_query::insert::TomlValueInsertExt;
 use toml_query::read::TomlValueReadExt;
-use toml_query::error::ErrorKind as TQEK;
 use toml::Value;
 
 use libimagstore::store::Entry;
@@ -81,17 +80,17 @@ impl EntryCategory for Entry {
     }
 
     fn get_category(&self) -> Result<Option<Category>> {
-        match self.get_header().read(&String::from("category.value")) {
-            Err(res) => match res.kind() {
-                &TQEK::IdentifierNotFoundInDocument(_) => Ok(None),
-                _                                      => Err(res),
-            }
-            .chain_err(|| CEK::HeaderReadError),
-
-            Ok(Some(&Value::String(ref s))) => Ok(Some(s.clone().into())),
-            Ok(None) => Err(CE::from_kind(CEK::StoreReadError)).chain_err(|| CEK::HeaderReadError),
-            Ok(_) => Err(CE::from_kind(CEK::TypeError)).chain_err(|| CEK::HeaderReadError),
-        }
+        self.get_header()
+            .read("category.value")
+            .chain_err(|| CEK::HeaderReadError)
+            .and_then(|opt| {
+                opt.map(|v| {
+                    v.as_str()
+                        .map(String::from)
+                        .map(Category::from)
+                })
+                .ok_or(CE::from_kind(CEK::TypeError))
+            })
     }
 
     fn has_category(&self) -> Result<bool> {
diff --git a/lib/entry/libimagentrycategory/src/error.rs b/lib/entry/libimagentrycategory/src/error.rs
index bd3da1a0..32642043 100644
--- a/lib/entry/libimagentrycategory/src/error.rs
+++ b/lib/entry/libimagentrycategory/src/error.rs
@@ -22,6 +22,14 @@ error_chain! {
         CategoryError, CategoryErrorKind, ResultExt, Result;
     }
 
+    links {
+        StoreError(::libimagstore::error::StoreError, ::libimagstore::error::StoreErrorKind);
+    }
+
+    foreign_links {
+        TomlQueryError(::toml_query::error::Error);
+    }
+
     errors {
         StoreReadError {
             description("Store Read error")
diff --git a/lib/entry/libimagentrycategory/src/register.rs b/lib/entry/libimagentrycategory/src/register.rs
index d5b40584..bc1aa929 100644
--- a/lib/entry/libimagentrycategory/src/register.rs
+++ b/lib/entry/libimagentrycategory/src/register.rs
@@ -225,14 +225,13 @@ fn represents_category(store: &Store, sid: StoreId, name: &str) -> Result<bool>
                     .chain_err(|| CEK::StoreReadError)
                     .and_then(|fle| {
                         if let Some(fle) = fle {
-                            match fle.get_header()
+                            fle.get_header()
                                 .read(&String::from(CATEGORY_REGISTER_NAME_FIELD_PATH))
-                                .chain_err(|| CEK::HeaderReadError)
-                            {
-                                Ok(Some(&Value::String(ref s))) => Ok(s == name),
-                                Ok(_)                     => Err(CE::from_kind(CEK::TypeError)),
-                                Err(e)                    => Err(e).chain_err(|| CEK::HeaderReadError),
-                            }
+                                .chain_err(|| CEK::HeaderReadError)?
+                                .ok_or(CE::from_kind(CEK::TypeError))?
+                                .as_str()
+                                .map(|s| s == name)
+                                .ok_or(CE::from_kind(CEK::TypeError))
                         } else {
                             Ok(false)
                         }
@@ -276,14 +275,15 @@ impl<'a> Iterator for CategoryNameIter<'a> {
             .next()
             .map(|sid| {
                 self.0
-                    .get(sid)
-                    .chain_err(|| CEK::StoreReadError)
-                    .and_then(|fle| fle.ok_or(CE::from_kind(CEK::StoreReadError)))
-                    .and_then(|fle| match fle.get_header().read(&query) {
-                        Ok(Some(&Value::String(ref s))) => Ok(Category::from(s.clone())),
-                        Ok(_)  => Err(CE::from_kind(CEK::TypeError)),
-                        Err(e) => Err(e).chain_err(|| CEK::HeaderReadError),
-                    })
+                    .get(sid)?
+                    .ok_or_else(|| CE::from_kind(CEK::StoreReadError))?
+                    .get_header()
+                    .read(&query)
+                    .chain_err(|| CEK::HeaderReadError)?
+                    .and_then(Value::as_str)
+                    .map(String::from)
+                    .map(Category::from)
+                    .ok_or_else(|| CE::from_kind(CEK::TypeError))
             })
     }
 }