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interactive-story/backend/app/worldstate/engine.py
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parththakkar106andClaude Opus 4.8 cf464a48b0 Make NPCs a dedicated section with per-NPC stats
Replace the single shared `npc` stat template (+ npc_card_types) with an
`npcs` section: each NPC keyed by a stable id, carrying its own name,
description, trigger keys, and its OWN stats block. The AI addresses NPCs
as npc.<id>.<stat> (id shown in context), which also fixes the old
card-id-guessing problem. On adventure creation each NPC auto-creates a
story card (name/keys/desc) for lore + in-scene detection, unless a
same-name card already exists. All NPCs instantiate up front.

- engine: npcs instantiate/apply/render/reference, npc_name/npc_triggers
- builder: _visible_npcs matches each NPC's own keys
- create_adventure: auto-create story cards from npcs
- WorldStateDrawer: render defined NPCs with their own stats + desc tooltip
- demo seed: Gwen (health/trust) + Bandit Leader (health/aggression)
- tests updated (34 pass); no new migration (npcs lives in stat_schema JSON)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-07-21 15:17:47 +05:30

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"""RPG world-state engine.
The scenario carries a `stat_schema` (the template: which stats exist, their
bands and rules, and the milestones). An adventure carries a live `world_state`
instantiated from it. Each turn the AI proposes a *delta* (only what changed);
`apply_delta` is the referee — it clamps to min/max, caps per-turn change,
enforces cooldowns, and marks milestones sticky.
Nothing here ever raises on bad AI output: a malformed delta yields `{}` and the
turn continues, exactly like a broken script never breaks a turn.
"""
import copy
import json
import re
# stat_schema top-level sections that hold stat definitions.
STAT_SECTIONS = ("world", "player")
# Appended once to the system prompt so the model knows how to report changes.
EMIT_RULE = (
"After your narration, if and ONLY IF something in the world state changed this "
"turn, append a fenced code block labelled `state` containing a JSON object of "
"the CHANGES ONLY, as deltas (not new totals). Use paths like "
'"player.hp", "world.day", "npc.<id>.<stat>" (use the exact npc id shown in the '
'world state, e.g. npc.gwen.trust); "flags.<name>": true or false to toggle an '
'on/off state; and "milestones.<id>": true when an objective is completed. Send '
"only things that actually changed; never restate unchanged values. If nothing "
"changed, omit the block entirely. Example:\n"
'```state\n{"player.hp": -15, "npc.gwen.trust": 5, "milestones.escaped": true}\n```'
)
# ```state { ... } ``` (also tolerates ```json or an unlabelled fence); DOTALL.
_FENCE_RE = re.compile(r"```(?:state|json)?\s*(\{.*?\})\s*```", re.DOTALL | re.IGNORECASE)
# Fallback: a bare JSON object hugging the end of the text.
_TRAILING_RE = re.compile(r"(\{[^{}]*\})\s*$", re.DOTALL)
def has_schema(stat_schema: dict | None) -> bool:
"""True when a scenario actually defines an RPG layer."""
if not isinstance(stat_schema, dict):
return False
return any(
isinstance(stat_schema.get(k), dict) and stat_schema[k]
for k in (*STAT_SECTIONS, "npcs", "milestones", "flags")
)
def npc_name(ndef: dict, key: str) -> str:
name = ndef.get("name")
return name.strip() if isinstance(name, str) and name.strip() else key
def npc_triggers(ndef: dict, key: str) -> list[str]:
"""Lower-cased trigger words for detecting an NPC in scene: its `keys`
field, falling back to its display name."""
raw = ndef.get("keys") or npc_name(ndef, key)
return [k.strip().lower() for k in str(raw).split(",") if k.strip()]
def _initials(defs: dict) -> dict:
return {
name: d.get("initial", 0)
for name, d in defs.items()
if isinstance(d, dict)
}
def instantiate(stat_schema: dict | None) -> dict:
"""Build a fresh live world_state from a schema (initial values only)."""
if not has_schema(stat_schema):
return {}
ws: dict = {}
for section in STAT_SECTIONS:
ws[section] = _initials(stat_schema.get(section) or {})
# Each defined NPC gets its own stat block from its own `stats` defs.
ws["npc"] = {
key: _initials(ndef.get("stats") or {})
for key, ndef in (stat_schema.get("npcs") or {}).items()
if isinstance(ndef, dict)
}
ws["milestones"] = {} # only reached ones are stored
ws["flags"] = {
name: bool(d.get("initial", False))
for name, d in (stat_schema.get("flags") or {}).items()
if isinstance(d, dict)
}
ws["_meta"] = {"last_changed": {}}
return ws
def band_label(stat_def: dict, value) -> str | None:
"""The word label for `value` from a stat def's bands, if any.
Bands are [lo, hi, label]; matched as lo <= value < hi, with the top band
inclusive of its upper bound so a maxed stat still gets a label.
"""
bands = stat_def.get("bands")
if not isinstance(bands, list) or not isinstance(value, (int, float)):
return None
last_hi = None
for band in bands:
if not (isinstance(band, list) and len(band) == 3):
continue
lo, hi, label = band
last_hi = hi
if lo <= value < hi:
return str(label)
# Inclusive top edge.
if bands and value == last_hi:
return str(bands[-1][2])
return None
# --------------------------------------------------------------------------- #
# Delta extraction
# --------------------------------------------------------------------------- #
def _tolerant_load(blob: str) -> dict:
# Strip trailing commas and leading + on numbers, both of which weaker
# free models emit and strict JSON rejects.
cleaned = re.sub(r",(\s*[}\]])", r"\1", blob)
cleaned = re.sub(r"(:\s*)\+(\d)", r"\1\2", cleaned)
try:
parsed = json.loads(cleaned)
except (json.JSONDecodeError, ValueError):
return {}
return parsed if isinstance(parsed, dict) else {}
def extract_delta(text: str) -> tuple[str, dict]:
"""Pull the trailing state block out of an AI response.
Returns (clean_text, delta). `delta` is `{}` when there is no block or it
can't be parsed; `clean_text` has the block removed. Only strips a bare
trailing object when it actually parses to a delta, so ordinary prose
ending in `}` is never eaten.
"""
matches = list(_FENCE_RE.finditer(text))
if matches:
m = matches[-1]
delta = _tolerant_load(m.group(1))
clean = (text[: m.start()] + text[m.end():]).strip()
return clean, delta
m = _TRAILING_RE.search(text)
if m:
delta = _tolerant_load(m.group(1))
if delta and all("." in str(k) for k in delta):
clean = text[: m.start()].strip()
return clean, delta
return text.strip(), {}
# --------------------------------------------------------------------------- #
# Delta application (the referee)
# --------------------------------------------------------------------------- #
def _coerce_number(value):
if isinstance(value, bool): # bool is an int subclass — reject here
return None
if isinstance(value, (int, float)):
return value
if isinstance(value, str):
try:
return float(value.strip())
except ValueError:
return None
return None
def _apply_stat(container: dict, key: str, stat_def: dict, change,
path: str, action_index: int, meta: dict, report: dict) -> None:
delta = _coerce_number(change)
if delta is None:
report["rejected"].append({"path": path, "reason": "not a number"})
return
cooldown = stat_def.get("cooldown") or 0
last = meta["last_changed"].get(path)
if cooldown and last is not None and action_index - last < cooldown:
report["rejected"].append({"path": path, "reason": "cooldown"})
return
if stat_def.get("type") == "counter" and delta < 0:
report["rejected"].append({"path": path, "reason": "counter can't decrease"})
return
clamped = False
cap = stat_def.get("max_delta_per_turn")
if cap is not None and abs(delta) > cap:
delta = cap if delta > 0 else -cap
clamped = True
old = container.get(key, stat_def.get("initial", 0))
new = old + delta
lo, hi = stat_def.get("min"), stat_def.get("max")
if lo is not None and new < lo:
new, clamped = lo, True
if hi is not None and new > hi:
new, clamped = hi, True
# Keep ints integral for display.
if isinstance(old, int) and float(new).is_integer():
new = int(new)
container[key] = new
meta["last_changed"][path] = action_index
entry = {"path": path, "old": old, "new": new}
report["applied"].append(entry)
if clamped:
report["clamped"].append(entry)
def apply_delta(world_state: dict, stat_schema: dict, delta: dict,
action_index: int) -> tuple[dict, dict]:
"""Validate/clamp `delta` against `stat_schema` and apply to a copy of
`world_state`. Returns (new_world_state, report)."""
ws = copy.deepcopy(world_state) if isinstance(world_state, dict) else {}
if not ws:
ws = instantiate(stat_schema)
ws.setdefault("_meta", {}).setdefault("last_changed", {})
meta = ws["_meta"]
report: dict = {"applied": [], "clamped": [], "rejected": []}
if not isinstance(delta, dict):
return ws, report
milestones = stat_schema.get("milestones") or {}
flag_defs = stat_schema.get("flags") or {}
npcs = stat_schema.get("npcs") or {}
for raw_path, change in delta.items():
path = str(raw_path)
parts = path.split(".")
# flags.<name> — free two-way boolean, either value accepted.
if parts[0] == "flags" and len(parts) == 2:
fid = parts[1]
if fid not in flag_defs:
report["rejected"].append({"path": path, "reason": "unknown flag"})
continue
if not isinstance(change, bool):
report["rejected"].append({"path": path, "reason": "not a boolean"})
continue
flags = ws.setdefault("flags", {})
old = bool(flags.get(fid, False))
if change != old:
flags[fid] = change
report["applied"].append({"path": path, "old": old, "new": change})
continue
# milestones.<id> — sticky boolean, only `true` accepted.
if parts[0] == "milestones" and len(parts) == 2:
mid = parts[1]
if mid not in milestones:
report["rejected"].append({"path": path, "reason": "unknown milestone"})
continue
if change is not True:
report["rejected"].append({"path": path, "reason": "not true"})
continue
reached = ws.setdefault("milestones", {})
if reached.get(mid, {}).get("reached"):
continue # already done — silent no-op
reached[mid] = {"reached": True, "at": action_index}
report["applied"].append({"path": path, "old": False, "new": True})
continue
# world.<stat> / player.<stat>
if parts[0] in STAT_SECTIONS and len(parts) == 2:
stat_def = (stat_schema.get(parts[0]) or {}).get(parts[1])
if not isinstance(stat_def, dict):
report["rejected"].append({"path": path, "reason": "unknown stat"})
continue
container = ws.setdefault(parts[0], {})
_apply_stat(container, parts[1], stat_def, change, path,
action_index, meta, report)
continue
# npc.<npcId>.<stat> — each NPC has its own stat defs.
if parts[0] == "npc" and len(parts) == 3:
ndef = npcs.get(parts[1])
if not isinstance(ndef, dict):
report["rejected"].append({"path": path, "reason": "unknown npc"})
continue
stat_defs = ndef.get("stats") or {}
stat_def = stat_defs.get(parts[2])
if not isinstance(stat_def, dict):
report["rejected"].append({"path": path, "reason": "unknown npc stat"})
continue
npc_state = ws.setdefault("npc", {})
container = npc_state.setdefault(parts[1], _initials(stat_defs))
_apply_stat(container, parts[2], stat_def, change, path,
action_index, meta, report)
continue
report["rejected"].append({"path": path, "reason": "unknown path"})
return ws, report
# --------------------------------------------------------------------------- #
# Context rendering
# --------------------------------------------------------------------------- #
def _stat_line(defs: dict, values: dict) -> str:
parts = []
for name, d in defs.items():
if not isinstance(d, dict):
continue
val = values.get(name, d.get("initial", 0))
hi = d.get("max")
shown = f"{val}/{hi}" if hi is not None else f"{val}"
label = band_label(d, val)
parts.append(f"{name} {shown}" + (f" ({label})" if label else ""))
return ", ".join(parts)
def render_state_section(world_state: dict, stat_schema: dict,
visible_npcs: dict[str, str]) -> str:
"""Compact, always-included context block. `visible_npcs` maps card-id ->
display name for NPCs currently in scene."""
ws = world_state if isinstance(world_state, dict) else {}
lines: list[str] = []
world_defs = stat_schema.get("world") or {}
world_line = _stat_line(world_defs, ws.get("world") or {})
header = "World state" + (f" — {world_line}." if world_line else ".")
lines.append(header)
player_defs = stat_schema.get("player") or {}
player_line = _stat_line(player_defs, ws.get("player") or {})
if player_line:
lines.append(f"You: {player_line}.")
npcs = stat_schema.get("npcs") or {}
npc_state = ws.get("npc") or {}
for npc_key, name in visible_npcs.items():
ndef = npcs.get(npc_key) or {}
stat_defs = ndef.get("stats") or {}
values = npc_state.get(npc_key) or _initials(stat_defs)
npc_line = _stat_line(stat_defs, values)
if npc_line:
# Show the id so the AI can address it as npc.<id>.<stat>.
lines.append(f"{name} (npc.{npc_key}): {npc_line}.")
flag_defs = stat_schema.get("flags") or {}
flag_state = ws.get("flags") or {}
flag_parts = [
f"{name} {'yes' if flag_state.get(name, bool(d.get('initial', False))) else 'no'}"
for name, d in flag_defs.items() if isinstance(d, dict)
]
if flag_parts:
lines.append("Flags: " + ", ".join(flag_parts) + ".")
milestones = stat_schema.get("milestones") or {}
reached = ws.get("milestones") or {}
goals = [d.get("desc", mid) for mid, d in milestones.items()
if not reached.get(mid, {}).get("reached")]
done = [d.get("desc", mid) for mid, d in milestones.items()
if reached.get(mid, {}).get("reached")]
if goals:
lines.append("Goals: " + "; ".join(goals) + ".")
if done:
lines.append("Achieved: " + "; ".join(done) + ".")
return "\n".join(lines)
def _describe_stat(name: str, d: dict) -> str | None:
"""One reference line for a stat. Description and band-ladder are independent —
each is included only when present, so a stat may have either, both, or neither."""
bits: list[str] = []
desc = d.get("desc")
if isinstance(desc, str) and desc.strip():
# Fragments are joined with "; " and end with a single ".", so drop any
# trailing period the author already put on the description.
bits.append(desc.strip().rstrip("."))
lo, hi = d.get("min"), d.get("max")
if isinstance(lo, (int, float)) and isinstance(hi, (int, float)):
bits.append(f"range {lo}–{hi}")
bands = d.get("bands")
if isinstance(bands, list) and bands:
ladder = ", ".join(
f"{b[0]}–{b[1]} {b[2]}"
for b in bands if isinstance(b, list) and len(b) == 3
)
if ladder:
bits.append(f"bands: {ladder}")
return f"{name} — {'; '.join(bits)}." if bits else None
def render_reference(stat_schema: dict) -> str:
"""A fixed, per-scenario legend describing what each stat means (its `desc`)
and its band ladder. Static across turns — separate from the live values."""
lines: list[str] = []
for section in STAT_SECTIONS:
for name, d in (stat_schema.get(section) or {}).items():
if isinstance(d, dict):
row = _describe_stat(name, d)
if row:
lines.append(row)
for npc_key, ndef in (stat_schema.get("npcs") or {}).items():
if not isinstance(ndef, dict):
continue
name = npc_name(ndef, npc_key)
desc = ndef.get("desc")
if isinstance(desc, str) and desc.strip():
lines.append(f"NPC {name} ({npc_key}) — {desc.strip().rstrip('.')}.")
for sname, sdef in (ndef.get("stats") or {}).items():
if isinstance(sdef, dict):
row = _describe_stat(f"{name} {sname}", sdef)
if row:
lines.append(row)
for name, d in (stat_schema.get("flags") or {}).items():
if isinstance(d, dict):
desc = d.get("desc")
if isinstance(desc, str) and desc.strip():
lines.append(f"{name} (flag) — {desc.strip().rstrip('.')}.")
if not lines:
return ""
return "Stat guide (fixed reference):\n" + "\n".join(f"- {ln}" for ln in lines)