Provide exception messages

UmbrellaNotFoundError: serial
UmbrellaValueError: field

3 files changed, 34 insertions, 9 deletions

diff --git a/jimbrella/admin.py b/jimbrella/admin.py
index df751ee..4c604be 100644
--- a/jimbrella/admin.py
+++ b/jimbrella/admin.py
@@ -1,6 +1,7 @@
 from flask import Blueprint, request, render_template, redirect, url_for
 from user_agents import parse as user_agent
 from .database import Database
+from .exceptions import *
 from .config import *
 
 bp = Blueprint("admin", __name__, url_prefix="/admin")
@@ -25,11 +26,17 @@ def index():
 def umbrellas():
     umbrellas = db.read()
     edit = request.args.get("edit")
+    error = request.args.get("error")
+    template = (
+        "admin/umbrellas_mobile.html"
+        if user_agent(request.user_agent.string).is_mobile
+        else "admin/umbrellas_desktop.html"
+    )
     return render_template(
-        "admin/umbrellas.html",
+        template,
         umbrellas=umbrellas,
         edit=int(edit) if edit else None,
-        mobile=user_agent(request.user_agent.string).is_mobile,
+        error=error,
     )
 
 
@@ -48,5 +55,17 @@ def umbrellas_edit():
     ]:
         data[key] = request.form.get(key)
 
-    db.update(data)
+    error = None
+    try:
+        db.update(data)
+    except UmbrellaValueError as e:
+        # invalid field is in `e.message`.
+        return redirect(
+            "{0}?edit={1}&error={2}".format(
+                url_for("admin.umbrellas"), request.form.get("serial"), e.message
+            )
+        )
+    except UmbrellaNotFoundError:
+        pass  # impossible on web console
+
     return redirect(url_for("admin.umbrellas"))
diff --git a/jimbrella/database.py b/jimbrella/database.py
index ab945da..e43b8f2 100644
--- a/jimbrella/database.py
+++ b/jimbrella/database.py
@@ -190,7 +190,7 @@ class Database:
         umb["serial"] = int(umb["serial"])
         umb_in_db = self._find_by_serial(umb["serial"])
         if umb_in_db is None:
-            raise UmbrellaNotFoundError
+            raise UmbrellaNotFoundError(umb["serial"])
 
         status = umb_in_db["status"]
         if "status" in umb and umb["status"]:
@@ -261,7 +261,7 @@ class Database:
         """When a user has borrowed an umbrella."""
         umb = self._find_by_serial(serial)
         if umb is None:
-            raise UmbrellaNotFoundError
+            raise UmbrellaNotFoundError(serial)
         elif umb["status"] != "available":
             raise UmbrellaStatusError
         umb["status"] = "lent"
@@ -276,7 +276,7 @@ class Database:
         """When a user has returned an umbrella."""
         umb = self._find_by_serial(serial)
         if umb is None:
-            raise UmbrellaNotFoundError
+            raise UmbrellaNotFoundError(serial)
         elif umb["status"] not in ("lent", "overdue"):
             raise UmbrellaStatusError
         umb["status"] = "available"
@@ -289,7 +289,7 @@ class Database:
         """When an umbrella is overdue, change its status to "overdue"."""
         umb = self._find_by_serial(serial)
         if umb is None:
-            raise UmbrellaNotFoundError
+            raise UmbrellaNotFoundError(serial)
         elif umb["status"] != "lent":
             raise UmbrellaStatusError
         umb["status"] = "overdue"
diff --git a/jimbrella/exceptions.py b/jimbrella/exceptions.py
index 2c62bc4..ad92b50 100644
--- a/jimbrella/exceptions.py
+++ b/jimbrella/exceptions.py
@@ -4,7 +4,10 @@
 class UmbrellaNotFoundError(Exception):
     """For when an umbrella with required serial is not found in database."""
 
-    pass
+    def __init__(self, serial):
+        self.serial = serial
+        self.message = f"No umbrella {serial} found."
+        super().__init__(self.message)
 
 
 class UmbrellaStatusError(Exception):
@@ -18,4 +21,7 @@ class UmbrellaStatusError(Exception):
 class UmbrellaValueError(Exception):
     """For when an admin enters an invalid value when modifying the database."""
 
-    pass
+    def __init__(self, field: str):
+        self.field = field
+        self.message = f"Invalid field: {field}."
+        super().__init__(self.message)