Commit graph

7 commits

Author SHA1 Message Date
William Carroll
239ff24c95 Use ORDER BY to sort the response for GET /trips
SQL is quite useful.
2020-08-02 19:50:28 +01:00
William Carroll
ed557fb6be Support PATCH /trips
Support a top-level PATCH request to trips that permits any admin to update any
trip, and any user to update any of their trips.

I'm using Aeson's (:?) combinator to support missing fields from the incoming
JSON requests, and then M.fromMaybe to apply these values to any record that
matches the primary key.

See the TODOs that I introduced for some shortcomings.
2020-07-31 11:25:36 +01:00
William Carroll
7d64011cbd Protect GET /trips with a session cookie
When an admin requests /trips, they see all of the trips in the Trips
table. When a user requests /trips, they see only their trips.
2020-07-31 10:55:10 +01:00
William Carroll
8ebc89b44b Remove erroneous parens around columns in SELECT statement
These were causing runtime errors... whoops!
2020-07-30 19:52:04 +01:00
William Carroll
6ecab8c3a6 Prefer SELECT (a,b,c) to SELECT *
"SELECT *" in SQL may not guarantee the order in which a record's columns are
returned. For example, in my FromRow instances for Account, I make successive call

The following scenario silently and erroneously assigns:

firstName, lastName = lastName, firstName

```sql
CREATE TABLE People (
  firstName TEXT NOT NULL,
  lastName TEXT NOT NULL,
  age INTEGER NOT NULL,
  PRIMARY KEY (firstName, lastName)
)
```

```haskell
data Person = Person { firstName :: String, lastName :: String, age :: Integer }

fromRow = do
  firstName <- field
  lastName  <- field
  age       <- field
  pure Person{..}

getPeople :: Connection -> IO [Person]
getPeople conn = query conn "SELECT * FROM People"
```

This silently fails because both firstName and lastName are Strings, and so the
FromRow Person instance type-checks, but you should expect to receive a list of
names like "Wallace William" instead of "William Wallace".

The following won't break the type-checker, but will result in a runtime parsing
error:

```haskell
-- all code from the previous example remains the same except for:

fromRow = do
  age       <- field
  firstName <- field
  lastName  <- field
```

The "SELECT *" will return records like (firstName,lastName,age), but the
FromRow instance for Person will attempt to parse firstName as
Integer.

So... what have we learned? Prefer "SELECT (firstName,lastName,age)" instead of
"SELECT *".
2020-07-30 18:52:45 +01:00
William Carroll
90a521c78f Create Utils module for (|>) operator
For the past 3-4 Haskell projects on which I've worked, I've tried to habituate
the usage of the (&) operator, but I find that -- as petty as it may sound -- I
don't like the way that it looks, and I end up avoiding using it as a result.

This time around, I'm aliasing it to (|>) (i.e. Elixir style), and I'm hoping to
use it more.
2020-07-28 18:47:40 +01:00
William Carroll
012296f156 Move SQL out of API and into separate modules
Create modules for each Table in our SQL database. This cleans up the handler
bodies at the expense of introducing more files and indirection.
2020-07-28 18:38:30 +01:00