Open Source Adventures: Episode 57: Extending BATTLETECH Weapon app
Tags: javascript, svelte, gamedev
Published: 2022-05-09 12:27:01

Time to improve the app. Here are the main features for this episode:

* show stability damage
* include stability damage and minimum range in the form
* show weapon type
* show indirect fire indicator - with 🚀 emoji
* clean up display a bit

### `Slider.svelte`

I added extra property `step` to the component. In Svelte to mark property as optional you need to give it a default value, even if it's `undefined`. Not doing this just results in a warning.

```html
<script>
export let label, min, max, value, format, step = undefined
let id = Math.random().toString(36).slice(2)
</script>

<label for={id}>{label}:</label>
<input type="range" {min} {max} {step} bind:value id={id} />
<span>{format(value)}</span>
```

### `Form.svelte`

Form now has three extra sliders, and uses `step` for them and also for heat compensation.

Arguably now that I have this functionality, I might want to switch 0-100 sliders to 0-1 range with 0.01 step. Right now it's a mix of both.

```html
<script>
import Slider from "./Slider.svelte"

export let ammoRounds
export let heatPercentage
export let doubleHeatSinksPercentage
export let rangeAtLeast
export let damageValue
export let stabDamageValue
</script>

<form>
  <Slider label="Ammo for how many rounds" bind:value={ammoRounds} min={1} max={30} format={(v) => `${v}`}/>
  <Slider label="Heat to compensate for" bind:value={heatPercentage} min={0} max={100} step={5} format={(v) => `${v}%`}/>
  <Slider label="How many double heat sinks" bind:value={doubleHeatSinksPercentage} min={0} max={100} format={(v) => `${v}%`}/>
  <Slider label="Normal damage value" bind:value={damageValue} min={0} max={1} step={0.01} format={(v) => `${v}`}/>
  <Slider label="Stability damage value" bind:value={stabDamageValue} min={0} max={1} step={0.01} format={(v) => `${v}`}/>
  <Slider label="Range at least" bind:value={rangeAtLeast} min={90} max={720} step={30} format={(v) => `${v}m`}/>
</form>

<style>
form {
  display: grid;
  grid-template-columns: auto auto auto;
  margin-bottom: 1em;
}
</style>
```

### `App.svelte`

All the extra functionality didn't really complicate the code too much, but at some point we might want to refactor things out.

I moved rounding to two decimal digits functionality into `Row` component, as doing it here caused some minor rounding issues, and SRM2/SRM4/SRM6 had slightly different values due to too much rounding.

```html
<script>
import {sortBy} from "lodash"
import data from "./data.json"
import Form from "./Form.svelte"
import Headers from "./Headers.svelte"
import Row from "./Row.svelte"

let ammoRounds = 10
let heatPercentage = 80
let doubleHeatSinksPercentage = 0
let rangeAtLeast = 90
let damageValue = 1.0
let stabDamageValue = 0.5

$: heatSinkingPerTon = 3.0 + 3.0 * doubleHeatSinksPercentage / 100
$: costPerHeat = (heatPercentage / 100) / heatSinkingPerTon

let sortedData
$: {
  for (let row of data) {
    row.value = row.shots * (row.baseDamage * damageValue + row.baseStabDamage * stabDamageValue)
    row.ammoWeight = ammoRounds * row.ammoTonnagePerShot
    row.cost = row.tonnage + row.ammoWeight + row.heat * costPerHeat
    row.ratio = row.value / row.cost
    row.id = Math.random().toString(36).slice(2)
  }
  sortedData = sortBy(data, [(x) => -x.ratio, (x) => x.name])
}
</script>

<h1>BATTLETECH Weapons Data</h1>

<Form bind:ammoRounds bind:heatPercentage bind:doubleHeatSinksPercentage bind:rangeAtLeast bind:damageValue bind:stabDamageValue />

<table>
  <Headers />
  {#each sortedData as row (row.id)}
    {#if row.maxRange >= rangeAtLeast}
      <Row data={row} />
    {/if}
  {/each}
</table>

<style>
:global(body) {
  margin: 0;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
}
table :global(tr):nth-child(even) {
  background-color: #f2f2f2;
}
table :global(tr):nth-child(odd) {
  background-color: #e0e0e0;
}
</style>
```

### `Headers.svelte`

Nothing too exciting about this one:

```html
<tr>
  <th>Name</th>
  <th>Bonus</th>
  <th>Type</th>
  <th>Damage</th>
  <th>Stab Damage</th>
  <th>Heat</th>
  <th>Weight</th>
  <th>Ammo Weight</th>
  <th>Range</th>
  <th>Value</th>
  <th>Cost</th>
  <th>Ratio</th>
</tr>
```

### `Row.svelte`

There's some more funcitonality here. Perhaps `typeSymbol` should be moved to the data exporter, I didn't notice that Support weapons are marked as `AntiPersonnel` in game files.

I'm blanking zero fields to improve readability, but not the weight field for MG++.

```html
<script>
export let data

let round100 = (v) => Math.round(v * 100) / 100

let {baseName, bonus, category, baseStabDamage, heat, shots, baseDamage, tonnage, maxRange, value, cost, ratio, ammoWeight, indirectFire} = data
let damage, stabDamage
if (shots == 1) {
  damage = baseDamage
  stabDamage = baseStabDamage
} else {
  damage = `${shots}x${baseDamage}`
  stabDamage = `${shots}x${baseStabDamage}`
}
if (heat == 0) {
  heat = ""
}
if (baseStabDamage == 0) {
  stabDamage = ""
}
if (ammoWeight == 0) {
  ammoWeight = ""
}
let typeSymbol = (category == "AntiPersonnel") ? "S" : category.substring(0, 1)
</script>

<tr>
  <td>{baseName}</td>
  <td>{bonus}</td>
  <td>{typeSymbol}</td>
  <td>{damage}</td>
  <td>{stabDamage}</td>
  <td>{heat}</td>
  <td>{tonnage}</td>
  <td>{round100(ammoWeight)}</td>
  <td>
    {maxRange}m
    {#if indirectFire}
      🚀
    {/if}
  </td>
  <td>{round100(value)}</td>
  <td>{round100(cost)}</td>
  <td>{round100(ratio)}</td>
</tr>
```

### Story so far

[All the code is on GitHub](https://github.com/taw/open-source-adventures).

I deployed this on GitHub Pages, [you can see it here](https://taw.github.io/open-source-adventures/episode-57/).

### Coming next

I think the app is pretty good, so in the next episode I'll move on to something else.