Energy Estimator

Assumptions

I'm making the following initial assumptions as part of the exercise:

• We're always going to get one TurnOff command at the beginning and one at the end of the sequence.
• Whenever we find duplicate entries (i.e. same timestamp) we will only leave the last one (sorted by insertion order)
• For all other purposes, entries will be sorted by timestamp
• I'm currently not enforcing that the dimmer value doesn't go over 1.0 (per one of the examples)
• I'm currently not doing any rounding or trimming of decimals
• EOF will be triggered by Ctrl + D or some other equivalent command (and I'm handling that internally rather than requiring the <<EOF Unix syntax)

Command Validation

I'm assuming the following structure:

<timestamp> <command>

where

• timestamp is any positive integer number
• command is one of:
  • Delta <value>
    • value in turn is composed of:
      • Sign: either + or -
      • Number: an unsigned (because the sign is already included) float number
  • TurnOff
    • This takes no parameters and is implicitly equivalent to: Delta 0.0

Having said all of this, any input that doesn't follow this structure will be rejected as invalid.

Estimation Formula

I'm assuming that the formula for calculating the total energy used will be:

Consumption per period = <period_length> * <consumption_rate>
Total = <period1_consumption> + <period2_consumption> +... + <periodn_consumption>

where

• period_length is a float expressed in hours, calculated as:

  • period_end_timestamp - period_start_timestamp

• consumption_rate is a float expressed in watts (and depends on the wattage of the light bulb being used)

Example usage

$ energy-estimator
> 1544206562 TurnOff
> 1544206563 Delta +0.5
> 1544210163 TurnOff
> EOF
Estimated energy used: 2.5 Wh

$ energy-estimator
> 1544206562 TurnOff
> 1544206563 Delta +0.5
> 1544210163 Delta -0.25
> 1544211963 Delta +0.75
> 1544211963 Delta +0.75
> 1544213763 TurnOff
> EOF
Estimated energy used: 5.625 Wh

Installation

• brew install pipenv (if not already installed)
• make install

Execution

• energy-estimator

This is not a true, standalone executable (it needs to run within the context of the python env), but is simple enough for now.

We could also use pyinstaller to package an actual independent, executable file. (We'll see if we have time for that)

EDIT: I didn't get a chance to test this, but I think what I'm missing is:

pip install pyinstaller --dev

And then to actually create the executable (and this would eventually get included within the Makefile):

pyinstaller cli.py

But again, I didn't test this (didn't want to risk breaking stuff and spending lots of time on it)

Development

• Install dev dependencies with make dev
• Run test scripts with make qa