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Items (base price, sell fraction) and vendors (stock, buys, refuses) are the game's data handed over at boot; standing, the day, a shortage and "buys beyond its list" are the ShopWorld port; money is ShopPurse and the pack ShopPack. The week's wanted and glutted items come from an Rng seeded by the week, never the world's. The balance invariants - a shop is not a fountain, friction falls and never inverts, raw keeps its order - are the package's tests (nine). ludic.crafting: its private names carry the package's prefix too (a private name is still one global namespace with the game's - ludic.shop's `sp_seed` met the game's). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
60 lines
3.3 KiB
Markdown
60 lines
3.3 KiB
Markdown
# ludic.shop
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Vendors behind counters: what each sells and buys, what a thing costs and fetches at the
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player's standing, what each vendor is short of this week, and buying and selling through the
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game's money and pack. Uses [`ludic.base`](../ludic.base/README.md) and nothing else.
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```ludic
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import "ludic.shop"
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```
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Items and vendors are the game's data, handed over as it boots: every item's base price and the
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fraction of the curve a vendor pays for it (`shop_config_items`), and every vendor's shelves, what
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it buys and the one thing it refuses (`shop_add_vendor`, numbered in the order added). A vendor is
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a number; its name, face and words stay the game's.
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## The rules it keeps
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These hold whatever the numbers become, and the tests hold them:
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1. **A shop is not a fountain.** A vendor never pays as much for a thing it stocks as it charges
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for it - not in a week it wants them, not at the best standing, and not even by a $1 floor: a
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penny item it stocks fetches nothing.
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2. **Friction falls with standing and never inverts.** Buying runs from 1.15x base at standing 0
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to 0.92x at 100, selling from 0.62x to 0.85x (times the item's fraction), so a newcomer pays a
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little over and sells a little under, and the two never cross.
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3. **Raw material keeps its order.** A sale is ROUNDED, not truncated, so cheap things spanning a
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wide range of base prices do not all land on $1.
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## The ports
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```ludic
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export port ShopWorld {
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rep: fn() -> int # standing, 0 to 100
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day: fn() -> int # the game day; the demand turns every week (unbound: 1)
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buy_mult: fn() -> float # a shortage on everything bought (unbound: 1)
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also_buys: fn(int, int) -> bool # (vendor, item) taken beyond its list (unbound: none)
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}
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export port ShopPurse { money: fn() -> int, spend: fn(int) -> bool, earn: fn(int) -> void }
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export port ShopPack { count, take, add, room } # room unbound: no limit
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```
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## API
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| --- | --- |
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| `shop_config_items(prices, sell)`, `shop_clear_vendors()`, `shop_add_vendor(stock, buys, refuses) -> int` | the data |
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| `shop_config_curve(buy_new, buy_best, sell_new, sell_best)`, `shop_config_demand(wants, want_mult, glut_mult, days, seed)` | the numbers (defaults 1.15, 0.92, 0.62, 0.85; 3 wanted at 1.5x, one glut at 0.6x, 7 days, seed 1013) |
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| `shop_visit(v)`, `shop_away()`, `shop_vendor()`, `shop_at_counter()` | who is behind the counter (-1 nobody) |
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| `shop_price_buy(it)`, `shop_price_sell(it)`, `shop_price_sell_at(v, it)`, `shop_buy_factor()`, `shop_sell_factor()` | prices; with no vendor, no demand and no fountain guard |
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| `shop_stocks(v, it)`, `shop_buys(v, it)`, `shop_stock(v)`, `shop_sellable(v)` | shelves, and what in the pack a vendor takes |
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| `shop_wants(v, it)`, `shop_glutted(v, it)`, `shop_wanted(v)`, `shop_demand_mult(v, it)`, `shop_week()`, `shop_set_want(v, it)` | the week's demand, from the shop's own `Rng` seeded by the week |
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| `shop_can_buy(it)`, `shop_buy(it) -> bool`, `shop_sell(it, n) -> int` | one bought; up to `n` sold to the vendor at the counter |
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| `shop_trades() -> Queue<ShopTrade>` | `{ what: SHOP_BOUGHT / SHOP_SOLD, vendor, item, n, price }` |
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| `shop_reset()`, `shop_system() -> System` | `"shop"`, `PH_COMMIT`: a reset; nothing is saved (the week follows from the day) |
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## Tests
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```bash
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ludic test packages/ludic.shop
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```
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