You'll need to register an 'app' with Weekdone, as per their API docs.
CLIENT_ID={provided by weekdone app registration}
CLIENT_SECRET={provided by weekdone app registration}
REDIRECT_URL=https://localhost # this does not need to be valid, we just use it to snag the auth code
USER=you@example.com
PASSWORD=your_password_here
Login, to get a session cookie
curl -v -X POST -d "email=$USER" -d "password=$PASSWORD" https://weekdone.com/login
#< Set-Cookie: ln=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa; expires=Sat, 10-Sep-2016 23:42:32 GMT; path=/
Then using this cookie, connect to the oauth_authorize endpoint to get the auth code.
# gives 302 redirect to https://localhost/code=xxxx
curl -v --cookie 'ln=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa' "https://weekdone.com/oauth_authorize?client_id=${CLIENT_ID}&redirect_uri=${REDIRECT_URL}&response_type=code"
# it's also possible to get this auth code by browsing to:
# https://weekdone.com/oauth_authorize?client_id=${CLIENT_ID}&redirect_uri=${REDIRECT_URL}&response_type=code
# ... and just pulling it out of the broken localhost redirect that comes back after you login
#
Use auth-code to get token & refresh token
curl -v -X POST -d "client_id=${CLIENT_ID}&client_secret=${CLIENT_SECRET}&redirect_uri=${REDIRECT_URL}&code=${AUTH_CODE}&grant_type=authorization_code" https://weekdone.com/oauth_token
AUTH_TOKEN={returned_by_above}
REFRESH_TOKEN={returned_by_above}
Now start using the API!
# Add an item (type_id=1 == Done, type_id=2 == In Progress)
curl -X POST -d "type_id=1&description=woo-api" https://api.weekdone.com/1/item?token=${AUTH_TOKEN}
# List your own items
curl https://api.weekdone.com/1/items?user_id=me&token=${AUTH_TOKEN} | jq -C '.' | less -r
Token will expire, you can refresh it:
curl -v -X POST -d "client_id=${CLIENT_ID}&client_secret=${CLIENT_SECRET}&redirect_uri=${REDIRECT_URL}&code=${AUTH_CODE}&grant_type=refresh_token&refresh_token=${REFRESH_TOKEN}" https://weekdone.com/oauth_token