centralise msgs in copy/en.js

plus some other fixes

src/models/Interface.js

@@ -2,6 +2,12 @@
 /**
  * Model is a class whose sole responsibility is to save and load blueprints.
  * It allows for different storage mechanisms for different kinds of blueprints.
+ * 
+ * ERRORS:
+ * When a load function fails, it should throw either:
+ * 1. A __ error if the resource doesn't exist on that sheet/tab.
+ * 2. A __ error if a fragment lookup fails because it doesn't exist.
+ * 3. A __ error if something else goes wrong.
  */
 class Model {
   /**

src/models/StoreJson.js

@@ -1,5 +1,6 @@
 import fs from 'mz/fs'
 import { fmtSourceTitle } from '../lib/util'
+import copy from '../copy/en'
 
 const STORAGE_DIRNAME = 'temp'
 
@@ -22,39 +23,36 @@ class StoreJson {
     const fname = `${STORAGE_DIRNAME}/${parts[0]}__${parts[1]}__${
       parts[2]
     }.json`
-    return fs
-      .exists(fname)
-      .then(isAvailable => {
-        if (isAvailable) return fs.readFile(fname, 'utf8')
-        else {
-          throw new Error('No resource exists')
-        }
-      })
-      .then(data => JSON.parse(data))
-      .then(data => {
-        if (parts.length === 3) {
-          // No lookup if the requested url doesn't have a fragment
-          return data
-        } else if (parts[2] === 'ids') {
-          // Do a lookup if fragment is included to filter a relevant item
-          // When the resource requested is 'ids'
-          const id = parseInt(parts[3])
-          if (!isNaN(id) && id >= 0 && id < data.length) {
-            return data[id]
+    if (fs.existsSync(fname)) {
+      return fs.readFile(fname, 'utf8')
+        .then(data => JSON.parse(data))
+        .then(data => {
+          if (parts.length === 3) {
+            // No lookup if the requested url doesn't have a fragment
+            return data
+          } else if (parts[2] === 'ids') {
+            // Do a lookup if fragment is included to filter a relevant item
+            // When the resource requested is 'ids'
+            const id = parseInt(parts[3])
+            if (!isNaN(id) && id >= 0 && id < data.length) {
+              return data[id]
+            } else {
+              throw new Error(copy.errors.noFragment(parts))
+            }
           } else {
-            throw new Error(`Fragment index does not exist`)
+            // Do a lookup if fragment is included to filter a relevant item
+            const index = parseInt(parts[3])
+            if (!isNaN(index) && index >= 0 && index < data.length) {
+              console.log(data, index)
+              return data.filter((vl, idx) => idx === index)[0]
+            } else {
+              throw new Error(copy.errors.noFragment(parts))
+            }
           }
-        } else {
-          // Do a lookup if fragment is included to filter a relevant item
-          const index = parseInt(parts[3])
-          if (!isNaN(index) && index >= 0 && index < data.length) {
-            console.log(data, index)
-            return data.filter((vl, idx) => idx === index)[0]
-          } else {
-            throw new Error(`Fragment index does not exist`)
-          }
-        }
-      })
+        })
+    } else {
+      return Promise.reject(new Error(copy.errors.noResource(parts)))
+    }
   }
 
   // TODO: add method to build blueprint from data source