feat(combat): skills system

src/pf1e_simulator/combat.py

@@ -81,6 +81,7 @@ from typing import TYPE_CHECKING
 
 from pf1e_simulator.conditions import CONDITIONS_BY_NAME
 from pf1e_simulator.effects import ActiveBuff, ActiveCondition, StatModifier, resolve_modifiers
+from pf1e_simulator.models import PREDEFINED_SKILLS
 from pf1e_simulator.spells import (
     BuffEffect,
     ConditionEffect,
@@ -561,6 +562,39 @@ class CombatEngine:
         success = roll != _NATURAL_ONE and (roll == _NATURAL_TWENTY or total >= dc)
         return SaveResult(success=success, roll=roll, total=total, dc=dc)
 
+    def resolve_skill(
+        self, state: CombatantState, skill: str, dc: int
+    ) -> SaveResult:
+        """Roll a skill check against ``dc``.
+
+        """
+        skill_spec = PREDEFINED_SKILLS.get(skill)
+        if skill_spec is None:
+            msg = f"Unknown skill: {skill}"
+            raise ValueError(msg)
+
+        roll = self._rng.d20()
+        skill_rank = state.combatant.skills.get(skill, None)
+        rank = skill_rank.rank if skill_rank else 0
+        # Class skill bonus
+        class_bonus = 3 if skill_rank and skill_rank.class_skill else 0
+        # Armor check penalty
+        armor_penalty = skill_rank.armor_penalty if skill_rank else 0
+        if armor_penalty and skill_spec.armor_check_penalty:
+            armor_penalty = -abs(armor_penalty)
+        else:
+            armor_penalty = 0
+        # Ability modifier
+        ability_name = skill_spec.ability
+        ability_score = getattr(state.combatant.abilities, f"{ability_name}_score")
+        ability_mod = (ability_score - 10) // 2
+        # Effect/condition modifiers
+        mod_bonus = resolve_modifiers(self._stat_modifiers(state, skill))
+        total = roll + rank + class_bonus + ability_mod + armor_penalty + mod_bonus
+        # Natural 1/20 are not auto-fail/success for skills
+        success = total >= dc
+        return SaveResult(success=success, roll=roll, total=total, dc=dc)
+
     def _roll_initiative(self) -> list[CombatantState]:
         rolls: dict[str, tuple[int, int]] = {}
         for state in self._states:

src/pf1e_simulator/effects.py

@@ -43,6 +43,16 @@ StatTarget = Literal[
     "attack", "damage", "ac", "touch_ac", "flat_footed_ac",
     "fort", "ref", "will", "initiative",
     "cmb", "cmd", "speed_ft", "hp", "concentration", "cl",
+    # Skills (37 PF1e skills)
+    "acrobatics", "appraise", "bluff", "climb", "craft",
+    "diplomacy", "disable_device", "disguise", "escape_artist", "fly",
+    "handle_animal", "heal", "intimidate", "knowledge_arcana",
+    "knowledge_dungeoneering", "knowledge_engineering", "knowledge_geography",
+    "knowledge_history", "knowledge_local", "knowledge_nature",
+    "knowledge_nobility", "knowledge_planes", "knowledge_religion",
+    "linguistics", "perception", "perform", "profession", "ride",
+    "sense_motive", "sleight_of_hand", "spellcraft", "stealth",
+    "survival", "swim", "use_magic_device",
 ]
 
 _STACKING_TYPES: frozenset[str] = frozenset({"", "dodge", "racial", "trait"})

src/pf1e_simulator/loaders/foundry.py

@@ -36,6 +36,7 @@ from pf1e_simulator.models import (
     Combatant,
     DamageComponent,
     Saves,
+    SkillRank,
 )
 
 type Json = dict[str, Json] | list[Json] | str | int | float | bool | None
@@ -108,6 +109,30 @@ def _extract_spells(spellcasting: Json) -> list[str]:
     return names
 
 
+def _extract_skills(skills_section: Json) -> dict[str, SkillRank]:
+    """Extract skills from Foundry sheet skills section."""
+    if not isinstance(skills_section, dict):
+        return {}
+    skills: dict[str, SkillRank] = {}
+    for name, data in skills_section.items():
+        if not isinstance(data, dict):
+            continue
+        key = name.lower().replace(" ", "_").replace("(", "").replace(")", "")
+        # Handle special cases
+        key = key.replace("knowledge_", "knowledge_")
+        rank = data.get("rank", 0)
+        class_skill = data.get("classSkill", False)
+        armor_penalty = data.get("armorPenalty", 0)
+        if isinstance(armor_penalty, bool):
+            armor_penalty = 0
+        if isinstance(rank, bool):
+            rank = 0
+        skills[key] = SkillRank(
+            rank=int(rank) if isinstance(rank, (int, float)) else 0,
+            class_skill=bool(class_skill),
+            armor_penalty=int(armor_penalty) if isinstance(armor_penalty, (int, float)) else 0,
+        )
+    return skills
 class SheetLoadError(Exception):
     """Raised when a sheet cannot be loaded; carries path and reason."""
 
@@ -300,7 +325,8 @@ def load_sheet_detailed(path: Path) -> tuple[Combatant, LoadReport]:
     speed_raw = reader.as_dict(combat.get("speed"), "combat.speed")
     ac_raw = reader.as_dict(combat.get("ac"), "combat.ac")
     hp_raw = reader.as_dict(combat.get("hp"), "combat.hp")
-
+    skills_raw = root.get("skills")
+    skills = _extract_skills(skills_raw)
     sheet_id = reader.req_str(meta, "id", "meta.id")
     land_speed = reader.speed(speed_raw.get("land"), "combat.speed.land")
     if land_speed is None:
@@ -350,6 +376,7 @@ def load_sheet_detailed(path: Path) -> tuple[Combatant, LoadReport]:
         attacks=kept,
         features=_extract_features(root.get("feats")),
         spells=_extract_spells(root.get("spellcasting")),
+        skills=skills,
     )
     report = LoadReport(path=str(path), kept=len(kept), skipped=tuple(skipped))
     return combatant, report

src/pf1e_simulator/models.py

@@ -40,6 +40,166 @@ class Saves(_FrozenModel):
     will: int
 
 
+class SkillSpec(_FrozenModel):
+    """Definition of a PF1e skill."""
+
+    name: str
+    ability: Literal["str", "dex", "con", "int", "wis", "cha"]
+    trained_only: bool = False
+    armor_check_penalty: bool = False
+
+
+class SkillRank(_FrozenModel):
+    """A combatant's rank in a skill."""
+
+    rank: int = 0
+    class_skill: bool = False
+    armor_penalty: int = 0
+
+
+# Predefined PF1e skills (37 skills)
+PREDEFINED_SKILLS: dict[str, SkillSpec] = {
+    "acrobatics": SkillSpec(
+        name="Acrobatics", ability="dex",
+        trained_only=False, armor_check_penalty=True
+    ),
+    "appraise": SkillSpec(
+        name="Appraise", ability="int",
+        trained_only=False, armor_check_penalty=False
+    ),
+    "bluff": SkillSpec(
+        name="Bluff", ability="cha",
+        trained_only=False, armor_check_penalty=False
+    ),
+    "climb": SkillSpec(
+        name="Climb", ability="str",
+        trained_only=False, armor_check_penalty=True
+    ),
+    "craft": SkillSpec(
+        name="Craft", ability="int",
+        trained_only=True, armor_check_penalty=False
+    ),
+    "diplomacy": SkillSpec(
+        name="Diplomacy", ability="cha",
+        trained_only=False, armor_check_penalty=False
+    ),
+    "disable_device": SkillSpec(
+        name="Disable Device", ability="dex",
+        trained_only=True, armor_check_penalty=False
+    ),
+    "disguise": SkillSpec(
+        name="Disguise", ability="cha",
+        trained_only=False, armor_check_penalty=False
+    ),
+    "escape_artist": SkillSpec(
+        name="Escape Artist", ability="dex",
+        trained_only=False, armor_check_penalty=True
+    ),
+    "fly": SkillSpec(
+        name="Fly", ability="dex",
+        trained_only=False, armor_check_penalty=True
+    ),
+    "handle_animal": SkillSpec(
+        name="Handle Animal", ability="cha",
+        trained_only=True, armor_check_penalty=False
+    ),
+    "heal": SkillSpec(
+        name="Heal", ability="wis",
+        trained_only=False, armor_check_penalty=False
+    ),
+    "intimidate": SkillSpec(
+        name="Intimidate", ability="cha",
+        trained_only=False, armor_check_penalty=False
+    ),
+    "knowledge_arcana": SkillSpec(
+        name="Knowledge (Arcana)", ability="int",
+        trained_only=True, armor_check_penalty=False
+    ),
+    "knowledge_dungeoneering": SkillSpec(
+        name="Knowledge (Dungeoneering)", ability="int",
+        trained_only=True, armor_check_penalty=False
+    ),
+    "knowledge_engineering": SkillSpec(
+        name="Knowledge (Engineering)", ability="int",
+        trained_only=True, armor_check_penalty=False
+    ),
+    "knowledge_geography": SkillSpec(
+        name="Knowledge (Geography)", ability="int",
+        trained_only=True, armor_check_penalty=False
+    ),
+    "knowledge_history": SkillSpec(
+        name="Knowledge (History)", ability="int",
+        trained_only=True, armor_check_penalty=False
+    ),
+    "knowledge_local": SkillSpec(
+        name="Knowledge (Local)", ability="int",
+        trained_only=True, armor_check_penalty=False
+    ),
+    "knowledge_nature": SkillSpec(
+        name="Knowledge (Nature)", ability="int",
+        trained_only=True, armor_check_penalty=False
+    ),
+    "knowledge_nobility": SkillSpec(
+        name="Knowledge (Nobility)", ability="int",
+        trained_only=True, armor_check_penalty=False
+    ),
+    "knowledge_planes": SkillSpec(
+        name="Knowledge (Planes)", ability="int",
+        trained_only=True, armor_check_penalty=False
+    ),
+    "knowledge_religion": SkillSpec(
+        name="Knowledge (Religion)", ability="int",
+        trained_only=True, armor_check_penalty=False
+    ),
+    "linguistics": SkillSpec(
+        name="Linguistics", ability="int",
+        trained_only=True, armor_check_penalty=False
+    ),
+    "perception": SkillSpec(
+        name="Perception", ability="wis",
+        trained_only=False, armor_check_penalty=False
+    ),
+    "perform": SkillSpec(
+        name="Perform", ability="cha",
+        trained_only=False, armor_check_penalty=False
+    ),
+    "profession": SkillSpec(
+        name="Profession", ability="wis",
+        trained_only=True, armor_check_penalty=False
+    ),
+    "ride": SkillSpec(
+        name="Ride", ability="dex",
+        trained_only=False, armor_check_penalty=True
+    ),
+    "sense_motive": SkillSpec(
+        name="Sense Motive", ability="wis",
+        trained_only=False, armor_check_penalty=False
+    ),
+    "sleight_of_hand": SkillSpec(
+        name="Sleight of Hand", ability="dex",
+        trained_only=True, armor_check_penalty=True
+    ),
+    "spellcraft": SkillSpec(
+        name="Spellcraft", ability="int",
+        trained_only=True, armor_check_penalty=False
+    ),
+    "stealth": SkillSpec(
+        name="Stealth", ability="dex",
+        trained_only=False, armor_check_penalty=True
+    ),
+    "survival": SkillSpec(
+        name="Survival", ability="wis",
+        trained_only=False, armor_check_penalty=False
+    ),
+    "swim": SkillSpec(
+        name="Swim", ability="str",
+        trained_only=False, armor_check_penalty=True
+    ),
+    "use_magic_device": SkillSpec(
+        name="Use Magic Device", ability="cha",
+        trained_only=True, armor_check_penalty=False
+    ),
+}
 class DamageComponent(_FrozenModel):
     """One damage roll with its types (e.g. 1d8 piercing).
 
@@ -116,3 +276,4 @@ class Combatant(_FrozenModel):
     casting_ability: str = "wis"  # ability used for spell DCs: str/dex/con/int/wis/cha
     resources: dict[str, int] = Field(default_factory=dict)  # resource pools per combat
     metamagic_feats: list[str] = Field(default_factory=list)  # e.g. Empower/Maximize/Extend Spell
+    skills: dict[str, SkillRank] = Field(default_factory=dict)