Final value calculator in Discord

--- tags: user stories title: Final value calculator in Discord description: A slash-command based computation bot that computes outcome of SIP /lumpsum / step-up SIP etc. --- # Intro We want to offer slash commands on Discord, that can be used to compute common one-off stuff in Discord itself. At present, we are looking to offer these: - Final value of an SIP (a garden-variety SIP calculator) - Final value of a lumpsum investment (your common bank FD calculator) - Final value of a step-up SIP In future, we can probably build a goal-planner, but we can get to those eventually, and not in scope for current exploration. :::warning In this doc, we want to discuss only for SIP calculator, and cover the other two (Lumpsum & SIP step-up) later. ::: # Why - These calculations need to be **commoditized** With slash commands, we can put these right in the finger-tip of every member of our community. No more googling for an SIP calculator, or a step-up SIP calculator, or an FD calculator. It reduces the distractions, from a flow of conversations. - It's often too easy to form wrong perception around assets, looking at only the _promised returns_. Checking final value from two different assets, with different promised returns, can give perspective around real ROI of the extra effort / risk. # Details ## SIP command Command is `/sip` or `/dca`. Can be configured to have any variant as its name. But for now, let's proceed assuming it's `/sip` ![](https://i.imgur.com/FuanQI1.png) **Invocation** User can invoke it by typing `/sip` or a sub-text of it and selecting the command from slash command pallette. ### Arguments & Usage SIP calculators normally take 3 arguments: - SIP amount (fixed) :arrow_right: `amount(₹)` - Time period :arrow_right: `years` - Rate of Return :arrow_right: `return` [Sample SIP calculator](https://sipcalculator.in/) In our case, we have the following default values: | SIP Amount | Time Period | Rate of Return | | -------- | -------- | -------- | | 10k | 5 years | 10% | :::info These default values should be configurable, including currency. Possibly through some YAML config / JSON config file. ::: ### Sample invocation | Command with Args | What it should do | | -------- | -------- | | `/sip` | Final value of SIP of 10k / month, for 5 years, 10% p.a. XIRR | | `/sip amount(₹): 1500` | Final value of SIP of 1.5k / month, for 5 years, 10% p.a. XIRR | | `/sip years: 3` | Final value of SIP of 10k / month, for 3 years, 10% p.a. XIRR | | `/sip years: 3 return: 15` | Final value of SIP of 10k / month, for 3 years, 15% p.a. XIRR| | `/sip years:7 amount(₹): 40000 return: 8` | Final value of SIP of 40k / month, for 7 years, 8% p.a. XIRR | ### User Input Parsing - **Amount** | Input Value | ✅ / ❌ | Parsed Input | | -------- | -------- | -------- | | 5000 | ✅ | 5000 | | 5,000 | ✅ | 5000 | | 50,000,000 | ✅ | 50000000 | | 5L / 5l | ✅ | 500000 | | 5k / 5K | ✅ | 5000 | | 50Cr. / 50 cr / 50Cr | ✅ | 500000000 | | 7.8k | ✅ | 7800 | | _random string_ | ❌ | default value | | 0 | ✅ | 0| | 0.89 | ✅ | 0.89 | | 4000 INR | ✅ | 4000 | | 0.0000000001 |✅| 0.0000000001 | | (1+3i) | ❌ | default value | **Input values can be arbitrary expressions as well**. `3.5L + 1.2k - (1 + 4%)^68 + 12 Cr.` should be a valid expression as input. - **Years** | Input Value | ✅ / ❌ | Parsed Input | | -------- | -------- | -------- | | 5 | ✅ | 5 | | 5yr / 5Y / 5 years / 5 year / 5 yr | ✅ | 5 | | _random string_ | ❌ | default value | | 4.2 | ✅ | 4 years 2 months | |5yr 3mo / 5yr 3m / 5yr 3M | ✅ | 5 years 3 months | Any arbirary date range, should be fine too. For instance, `1/1/2018 - 1/6/2026` is a valid range, and parser should compute SIP final values correctly. - **Rate of Returns** | Input Value | ✅ / ❌ | Parsed Input | | -------- | -------- | -------- | | 14 | ✅ | 14.0 | | 12.245738849 | ✅ | 12.25 | | 12.652463 | ✅ | 12.65 | | 5.6% | ✅ | 5.6 | | 4.98% p.a. | ✅ | 4.98 | | _random string_ | ❌ | default value | Any arbirary return range, should be fine too. For instance, `5%-8% p.a.` is a valid range, and parser should compute SIP final values correctly. `p.m.` should also be allowed, in lieu of _per month_ rate. --- # Outputs This is where our SIP calculator gets a bit interesting. We want to have the bot post _meaningful_ outputs. One thing to keep in mind here: we would use some free-tier hosting. And it's to our own advantage, if most users won't need to use this beyond once / twice in the span of 10-15 mins. Output should be: - easy to read / understand - give meaningful information, that covers the intent behind same search / invocation When a user is asking _what would be value of SIP of 10k / month in 6 years at 12% p.a._, **they're not worried about exact final value**. In this case, the exact value would be $1,057,570$. But this is of little interest to the user. They'd want to know the range / ballpark. A better outcome is to report it as $10.6$L. Or, $10$L-$11$L. Let's go further. Why 10k? Probably user wants to start with a number for monthly amount. That's all. Why 6 years? Most likely it's investment for a time-period between 5-7 years. Why 12% p.a.? Most likely user thinks that's a rate of return that they can sustain over 6 years. ### A sample output ![](https://i.imgur.com/CMIUbEA.png) This covers: - how the investment valuation changes with time - how the investment valuation changes with returns We didn't post a field-set with amount variation, because if the actual amount is different, user can mentally scale-up or down as needed. For example, user might be doing an SIP of 30k / month, and if that's the case, they can mentally multiply by 3x and get a ballpark estimate. We need **6 datapoints** for each variation, 3 in each row. These datapoints are not equi-distant. For instance, if the return value is 10%+, we can go for difference of 2% plus-minus, both ways to get 6 data points. But if it's below 10, we can do plus-minus of 1%. For example, is user requests estimate for 7% p.a. returns, we can do 6 data points of 4% p.a., 5% p.a., 6% p.a., 8% p.a., 9% p.a, and 10% p.a. If it's below 5%, we can tweak the range to be of difference 0.5%. For instance, if the user requests simulation for 2% p.a., we should execute for 0.5%, 1%, 1.5%, 2.5%, 3%, 3.5% p.a. Similarly, for duration variation, we'd have to be somewhat intelligent in that aspect as well. Someone asking for a 25Y estimate, should also see estimate of 10Y, 15Y, 20Y, 30Y, 35Y, 40Y. But someone asking for an estimate of 5.2Y, should only see variation of 3Y / 4Y / 5Y / 6Y / 7Y / 8Y. ### Extra Ideally, we'd want to plug a link to a HTML-CSS-JS based page, where user can play with actual SIP calculator. TBD on that front.