feat(engine): 实现阵营技能树系统

- 新增 FactionSkill、FactionSkillTree、FactionSkills 数据模型
- 创建 faction_skills.py 模块处理技能解锁和效果应用
- 技能解锁条件：power >= cost 且前置技能已解锁
- 技能效果：increase_positive_emotion、reduce_conflict、increase_fear、suppress_others
- 添加 4 个技能树测试用例，全部 30 个测试通过

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

engine-python/app/engine.py

@@ -11,6 +11,7 @@ from .factions import (
     update_factions, apply_faction_influence, check_and_trigger_faction_event
 )
 from .voting import process_votes, apply_votes_to_factions
+from .faction_skills import check_and_unlock_skills, apply_skill_effects
 
 MAX_EVENTS = 20
 MAX_MEMORY_PER_AGENT = 3
@@ -106,6 +107,12 @@ def process_events(state: WorldState, events: List[Event]) -> WorldState:
     # 派系影响世界情绪
     apply_faction_influence(state)
 
+    # 检查并解锁技能
+    check_and_unlock_skills(state)
+
+    # 应用已解锁技能效果
+    apply_skill_effects(state)
+
     return state
 
 

engine-python/app/faction_skills.py

@@ -0,0 +1,126 @@
+"""阵营技能树系统 - 允许阵营通过累积能量解锁技能"""
+from typing import List, Optional
+from .models import (
+    WorldState, FactionSkill, FactionSkillTree, FactionSkills
+)
+
+
+def get_default_faction_skills() -> FactionSkills:
+    """返回默认技能树配置"""
+    return FactionSkills(
+        optimists=FactionSkillTree(
+            skills={
+                "festival_boost": FactionSkill(
+                    unlocked=False,
+                    cost=10,
+                    effect="increase_positive_emotion",
+                    requires=[]
+                ),
+                "unity": FactionSkill(
+                    unlocked=False,
+                    cost=20,
+                    effect="reduce_conflict",
+                    requires=["festival_boost"]
+                )
+            }
+        ),
+        fearful=FactionSkillTree(
+            skills={
+                "panic_spread": FactionSkill(
+                    unlocked=False,
+                    cost=10,
+                    effect="increase_fear",
+                    requires=[]
+                ),
+                "control": FactionSkill(
+                    unlocked=False,
+                    cost=20,
+                    effect="suppress_others",
+                    requires=["panic_spread"]
+                )
+            }
+        )
+    )
+
+
+def _check_requires_met(skill_tree: FactionSkillTree, requires: List[str]) -> bool:
+    """检查前置技能是否已解锁"""
+    for req in requires:
+        if req not in skill_tree.skills:
+            return False
+        if not skill_tree.skills[req].unlocked:
+            return False
+    return True
+
+
+def check_and_unlock_skills(state: WorldState) -> List[str]:
+    """检查并解锁技能
+
+    规则：
+    1. faction.power >= skill.cost
+    2. 技能尚未解锁
+    3. 所有 requires 已解锁
+
+    返回：本次解锁的技能列表
+    """
+    unlocked = []
+
+    # 检查乐观派技能
+    for skill_id, skill in state.faction_skills.optimists.skills.items():
+        if skill.unlocked:
+            continue
+        if state.factions.optimists.power < skill.cost:
+            continue
+        if not _check_requires_met(state.faction_skills.optimists, skill.requires):
+            continue
+
+        # 解锁技能
+        skill.unlocked = True
+        state.factions.optimists.power -= skill.cost
+        unlocked.append(f"optimists:{skill_id}")
+
+    # 检查恐惧派技能
+    for skill_id, skill in state.faction_skills.fearful.skills.items():
+        if skill.unlocked:
+            continue
+        if state.factions.fearful.power < skill.cost:
+            continue
+        if not _check_requires_met(state.faction_skills.fearful, skill.requires):
+            continue
+
+        # 解锁技能
+        skill.unlocked = True
+        state.factions.fearful.power -= skill.cost
+        unlocked.append(f"fearful:{skill_id}")
+
+    return unlocked
+
+
+def apply_skill_effects(state: WorldState) -> None:
+    """应用已解锁技能的持续效果
+
+    效果说明：
+    - increase_positive_emotion: 每 tick 提升 town_mood +1
+    - reduce_conflict: 降低恐惧派能量增长（每 tick -1）
+    - increase_fear: 每 tick 降低 town_mood -1
+    - suppress_others: 降低乐观派能量增长（每 tick -1）
+    """
+    # 乐观派技能效果
+    for skill_id, skill in state.faction_skills.optimists.skills.items():
+        if not skill.unlocked:
+            continue
+
+        if skill.effect == "increase_positive_emotion":
+            state.town_mood = min(10, state.town_mood + 1)
+        elif skill.effect == "reduce_conflict":
+            state.factions.fearful.power = max(0, state.factions.fearful.power - 1)
+
+    # 恐惧派技能效果
+    for skill_id, skill in state.faction_skills.fearful.skills.items():
+        if not skill.unlocked:
+            continue
+
+        if skill.effect == "increase_fear":
+            state.town_mood = max(-10, state.town_mood - 1)
+        elif skill.effect == "suppress_others":
+            state.factions.optimists.power = max(0, state.factions.optimists.power - 1)

engine-python/app/models.py

@@ -66,6 +66,25 @@ class Votes(BaseModel):
     voted_users: List[str] = Field(default_factory=list)
 
 
+class FactionSkill(BaseModel):
+    """单个技能"""
+    unlocked: bool = False
+    cost: int = 10
+    effect: str = ""
+    requires: List[str] = Field(default_factory=list)
+
+
+class FactionSkillTree(BaseModel):
+    """单个阵营的技能树"""
+    skills: Dict[str, FactionSkill] = Field(default_factory=dict)
+
+
+class FactionSkills(BaseModel):
+    """所有阵营的技能树"""
+    optimists: FactionSkillTree = Field(default_factory=FactionSkillTree)
+    fearful: FactionSkillTree = Field(default_factory=FactionSkillTree)
+
+
 class FactionEventResult(BaseModel):
     """阵营事件触发结果"""
     type: Optional[str] = None  # "festival" | "panic" | None
@@ -113,6 +132,7 @@ class WorldState(BaseModel):
     factions: Factions = Field(default_factory=Factions)
     story_arcs: Dict[str, StoryArc] = Field(default_factory=dict)
     votes: Votes = Field(default_factory=Votes)
+    faction_skills: FactionSkills = Field(default_factory=FactionSkills)
 
 
 class Event(BaseModel):

engine-python/app/state.py

@@ -2,6 +2,7 @@ import json
 from pathlib import Path
 from .models import WorldState, AgentState, GlobalMeter, Stance, Factions, FactionData
 from .story_arcs import get_default_story_arcs
+from .faction_skills import get_default_faction_skills
 
 STATE_FILE = Path(__file__).parent.parent / "state.json"
 
@@ -35,6 +36,7 @@ def get_default_state() -> WorldState:
             fearful=FactionData(power=0, threshold=10, skill="panic", members=[])
         ),
         story_arcs=get_default_story_arcs(),
+        faction_skills=get_default_faction_skills(),
     )
 
 

engine-python/tests/test_step.py

@@ -481,3 +481,63 @@ def test_votes_trigger_faction_event(client):
 
     # 要么触发了事件，要么能量在累积
     assert triggered or factions["optimists"]["power"] > 0
+
+
+# ==================== 技能树系统测试 ====================
+
+def test_faction_skills_exists_in_world_state(client):
+    """测试 world_state 包含 faction_skills 字段"""
+    resp = client.post("/step", json={"events": []})
+    data = resp.json()
+
+    assert "faction_skills" in data["world_state"]
+    skills = data["world_state"]["faction_skills"]
+    assert "optimists" in skills
+    assert "fearful" in skills
+
+
+def test_faction_skills_has_required_fields(client):
+    """测试技能包含必要字段"""
+    resp = client.post("/step", json={"events": []})
+    data = resp.json()
+
+    skills = data["world_state"]["faction_skills"]
+    opt_skills = skills["optimists"]["skills"]
+
+    assert "festival_boost" in opt_skills
+    skill = opt_skills["festival_boost"]
+    assert "unlocked" in skill
+    assert "cost" in skill
+    assert "effect" in skill
+    assert "requires" in skill
+
+
+def test_skill_unlock_when_power_sufficient(client):
+    """测试能量足够时解锁技能"""
+    # 多轮投票累积能量到 10+
+    for i in range(6):
+        events = [
+            {"type": "vote", "faction": "optimists", "text": "", "user": f"u{i}_a", "ts": i},
+            {"type": "vote", "faction": "optimists", "text": "", "user": f"u{i}_b", "ts": i+0.1},
+        ]
+        client.post("/step", json={"events": events})
+
+    # 再执行一轮让投票生效
+    resp = client.post("/step", json={"events": []})
+    data = resp.json()
+
+    skills = data["world_state"]["faction_skills"]["optimists"]["skills"]
+    # festival_boost cost=10，应该已解锁
+    assert skills["festival_boost"]["unlocked"] is True
+
+
+def test_skill_requires_prerequisite(client):
+    """测试技能需要前置技能"""
+    resp = client.post("/step", json={"events": []})
+    data = resp.json()
+
+    skills = data["world_state"]["faction_skills"]["optimists"]["skills"]
+    # unity 需要 festival_boost 作为前置
+    assert skills["unity"]["requires"] == ["festival_boost"]
+    # 初始状态下 unity 未解锁
+    assert skills["unity"]["unlocked"] is False