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fix: every field excursion is a different field (#3) #47

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fix: every field excursion is a different field (#3) #47

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11 changes: 9 additions & 2 deletions lib/game.js
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Original file line number Diff line number Diff line change
Expand Up @@ -196,6 +196,7 @@ class Runa {
this.dungeonReturn = null
this.player = new Player()
this.field = null
this.excursion = 0
this.shop = null
this.cursor = 0
this.title = true
Expand Down Expand Up @@ -774,7 +775,10 @@ class Runa {
this.pending = null

if (location.kind === 'field') {
this.field = new Field({ script: this.scriptSource, player: this.player })
this.excursion++
const seed =
(this.excursion * 2654435761 + this.player.xp * 40503 + this.player.gold) >>> 0
this.field = new Field({ script: this.scriptSource, player: this.player, seed })
Comment on lines +778 to +781

@gitar-bot gitar-bot Bot Aug 25, 2026

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💡 Quality: Seed derivation formula duplicated in two places

The identical (this.excursion * 2654435761 + this.player.xp * 40503 + this.player.gold) >>> 0 expression appears in both loadSlot() and enter(). Duplicating the magic constants risks the two paths drifting apart. Extract a small helper (e.g. nextFieldSeed() that also does this.excursion++) and call it from both sites.

Centralize the seed derivation so both field entry points stay in sync.:

nextFieldSeed() {
  this.excursion++
  return (this.excursion * 2654435761 + this.player.xp * 40503 + this.player.gold) >>> 0
}

// both call sites:
const seed = this.nextFieldSeed()
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this.field.player.x = clampNumber(location.x, 0, this.field.width - 1)
this.field.player.y = clampNumber(location.y, 0, this.field.height - 1)
} else {
Expand Down Expand Up @@ -1177,7 +1181,10 @@ class Runa {
switch (action.kind) {
case 'travel':
if (action.to === 'field') {
this.field = new Field({ player: this.player })
this.excursion++
const seed =
(this.excursion * 2654435761 + this.player.xp * 40503 + this.player.gold) >>> 0
this.field = new Field({ player: this.player, seed })
Comment on lines +1184 to +1187

@gitar-bot gitar-bot Bot Aug 25, 2026

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⚠️ Bug: excursion counter isn't persisted or reset on load

The excursion field is initialized to 0 in the constructor, incremented on every field entry, but never written to saveState() nor reset in loadSlot(). As a result the derived seed after loading a save depends on how many excursions happened earlier in the current session: reloading the same save twice yields different fields, and two players loading an identical save file (same xp/gold) get different maps. This contradicts the PR's stated goal that "una misma partida sigue siendo reproducible." Persist excursion in saveState() and restore it in loadSlot() (and reset it in the constructor path used for new games) so the seed is a pure function of saved state.

Persist and restore the excursion counter so the field seed is reproducible from saved state.:

// in saveState() return object:
    return {
      name: this.name,
      player,
      location,
      excursion: this.excursion,
      ...
    }

// in loadSlot(), before deriving the seed:
    this.excursion = Number(saved.excursion) || 0
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this.field.setScript(this.scriptSource)
this.say('salis de la ciudad. pulsa t para volver cuando no estes peleando')
} else if (action.to === 'dungeon') {
Expand Down
34 changes: 34 additions & 0 deletions test/index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1098,6 +1098,40 @@ test('hitbox combat stays on the field and advances on attack input', (t) => {
)
})

test('two excursions are never the same field (#3)', (t) => {
const game = new Runa({ presence: false })
startGame(game)

const openField = () => {
const gateTile = { x: 0, y: 0 }
// find the '>' exit and step on it via placeAt + enter
for (let y = 0; y < MAPS.city.rows.length; y++) {
const x = MAPS.city.rows[y].indexOf('>')
if (x !== -1) {
gateTile.x = x
gateTile.y = y
break
}
}
game.walker.placeAt('city', gateTile.x, gateTile.y)
press(game, 'e')
}

openField()
t.ok(game.field, 'first excursion opens the field')
const first = game.field.seed

press(game, 't')
t.absent(game.field, 't closes the excursion')
game.player.gold += 7

openField()
t.ok(game.field, 'second excursion opens a fresh field')
const second = game.field.seed

t.not(first, second, 'the seed differs between excursions')
})

test('t returns from the field to the city outside combat', (t) => {
const game = new Runa({ presence: false })
startGame(game)
Expand Down
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