und3f / devchallenge-2023-spreadsheet

Made during DEV Challenge 2023 competition (backend nomination)

Spreadsheet REST service

Made during DEV Challenge 2023 competition (backend nomination).

Test

The tests are executed during container build as a part of the Dockerfile.

To execute tests separately run:

docker build --target test --progress plain --no-cache .

Also you may execute tests locally by running:

go test -v ./...

Run

To start application simply run:

docker compose up --build

REST operations

# Set cell to a constant
curl -X POST localhost:8080/api/v1/devchallenge-xx/var1 -d '{"value": "123"}'

# Set cell to a formula expression
curl -X POST localhost:8080/api/v1/devchallenge-xx/var2 -d '{"value": "=var1*2"}'

# Get cell
curl localhost:8080/api/v1/devchallenge-xx/var1

# Get whole spreadsheet
curl localhost:8080/api/v1/devchallenge-xx

Corner cases

Cell identifies

You could use utf8 characters for cellId, the identifier should start with a letter, but next characters could be any printable except for +-*/():

curl -X POST localhost:8080/api/v1/devchallenge-xx/拿 -d '{"value": "2"}'
curl -X POST localhost:8080/api/v1/devchallenge-xx/á._ -d '{"value": "3"}'
curl -X POST localhost:8080/api/v1/devchallenge-xx/說 -d '{"value": "=á._+拿"}'

So 1abc is not valid variable name as it starts with a number, not a letter.

Both cell and spreadsheet identifiers length is limited by the http protocol.

Circular formulas

In case of circular dependency in formula result would be error. In a case of such error the update formula would be rejected:

curl -X POST localhost:8080/api/v1/devchallenge-xx/var2 -d '{"value": "1"}'
curl -X POST localhost:8080/api/v1/devchallenge-xx/var1 -d '{"value": "=var2"}'

curl -X POST localhost:8080/api/v1/devchallenge-xx/var2 -d '{"value": "=var1"}'
# Error occured because of circular dependency: var2 = var1 = var2 ...

Outputs: {"value":"=var2","result":"ERROR"}

Same applies for self referencing formulas:

curl -X POST localhost:8080/api/v1/devchallenge-xx/var1 -d '{"value": "=var1"}'

Types extrapolation

If INTEGER is mixed with the FLOAT the result would be FLOAT:

curl -X POST localhost:8080/api/v1/devchallenge-xx/var1 -d '{"value": "=1 + 2.2"}'

Result: {"value":"=1 + 2.2","result":"3.2"}

STRING is not applicable to mathematical operations, still it could be placed in brackets:

curl -X POST localhost:8080/api/v1/devchallenge-xx/var1 -d '{"value": "Some string"}'
curl -X POST localhost:8080/api/v1/devchallenge-xx/var2 -d '{"value": "=(var1)"}'

Result: {"value":"=(var1)","result":"Some string"}

Also division of INTEGER by INTEGER would result in FLOAT type for precision.

Formula expression

You may specify unary operator right after a binary and it would be treated as following token modifier, e.g. next formulas are legit: =1 * -2 = -2, =1 + -2 = -1, =1 + +2 = 3

Division by zero

You will receive ERROR during formula evaluation if division by zero occurs:

curl -X POST localhost:8080/api/v1/devchallenge-xx/var2 -d '{"value": "0.0"}' -H "Content-Type: application/json"
curl -X POST localhost:8080/api/v1/devchallenge-xx/var1 -d '{"value": "=1/var2"}' -H "Content-Type: application/json"

{
    "error": "division by zero",
    "result": "ERROR",
    "value": "=1/var2"
}

Dependent cell breaking prevention

The system prevents from breaking any dependant cell to be broken. Consider next case:

curl -X POST localhost:8080/api/v1/devchallenge-xx/var3 -d '{"value": "0"}' -H "Content-Type: application/json"
curl -X POST localhost:8080/api/v1/devchallenge-xx/var2 -d '{"value": "=var3 - 1"}' -H "Content-Type: application/json"
curl -X POST localhost:8080/api/v1/devchallenge-xx/var1 -d '{"value": "=1 / var2"}' -H "Content-Type: application/json"

# Next UPSERT would be rejected as it would break var1
curl -X POST localhost:8080/api/v1/devchallenge-xx/var3 -d '{"value": "1"}' -H "Content-Type: application/json"

# var3 is still 0
curl localhost:8080/api/v1/devchallenge-xx/var3

Cell value type determination

Cell value that starts with = would be considered as the formula.

Sequence of digits optionally precedent with a plus or minus sign considered as INT value: 1, -1, +1

If a number has fractional part it would be treated as a FLOAT value: 1.01, 1., -1.0, +1.0

Every other value would be treated as the STRING value: some string, 1.0.0, ++1

Numbers size

Numbers size is not limited, next expression would evaluate correctly:

curl -X POST localhost:8080/api/v1/devchallenge-xx/byte -d '{"value": "255"}' -H "Content-Type: application/json"
curl -X POST localhost:8080/api/v1/devchallenge-xx/short -d '{"value": "=byte * byte"}' -H "Content-Type: application/json"
curl -X POST localhost:8080/api/v1/devchallenge-xx/int32 -d '{"value": "=short * short"}' -H "Content-Type: application/json"
curl -X POST localhost:8080/api/v1/devchallenge-xx/int64 -d '{"value": "=int32 * int32"}' -H "Content-Type: application/json"
curl -X POST localhost:8080/api/v1/devchallenge-xx/int128 -d '{"value": "=int64 * int64"}' -H "Content-Type: application/json"
curl -X POST localhost:8080/api/v1/devchallenge-xx/whatever_you_want \
    -d '{"value": "=int128 * int128 * int128 * int128 * int128"}' \
    -H "Content-Type: application/json"

{
    "result": "3335910840989723103946716225008276488526215899027251552832106642768471211926062170159900171395553219118558904881722547998563003168023964769375828837692267436754178788760327734053134918212890625",
    "value": "=int128 * int128 * int128 * int128 * int128"
}

Copyright

Copyright (C) 2023-2024 Serhii Zasenko

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see https://www.gnu.org/licenses/.