"""The strictly validated decision schema returned by every LLM policy (and the mock)."""
from __future__ import annotations

from typing import Literal

from pydantic import BaseModel, Field, ValidationError, field_validator


class Decision(BaseModel):
    action: Literal["hold", "place", "cancel"]
    side: Literal["buy", "sell"] | None = None
    order_type: Literal["limit", "market"] | None = None
    quantity: int | None = Field(default=None, ge=0)
    limit_price: float | None = Field(default=None, gt=0)      # currency units (e.g. 199.50)
    cancel_order_ids: list[int] = Field(default_factory=list)
    confidence: float | None = Field(default=None, ge=0.0, le=1.0)
    rationale: str = Field(default="", max_length=400)

    @field_validator("rationale")
    @classmethod
    def _trim(cls, v: str) -> str:
        return v.strip()[:400]


DECISION_JSON_SCHEMA: dict = {
    "type": "object",
    "properties": {
        "action": {"type": "string", "enum": ["hold", "place", "cancel"]},
        "side": {"type": ["string", "null"], "enum": ["buy", "sell", None]},
        "order_type": {"type": ["string", "null"], "enum": ["limit", "market", None]},
        "quantity": {"type": ["integer", "null"]},
        "limit_price": {"type": ["number", "null"]},
        "cancel_order_ids": {"type": "array", "items": {"type": "integer"}},
        "confidence": {"type": ["number", "null"]},
        "rationale": {"type": "string"},
    },
    "required": ["action", "side", "order_type", "quantity", "limit_price", "cancel_order_ids", "confidence", "rationale"],
    "additionalProperties": False,
}


def parse_decision(text: str) -> tuple[Decision | None, str]:
    """Parse the model's JSON text; returns (decision, error). Lenient about code fences."""
    import json
    s = text.strip()
    if s.startswith("```"):
        s = s.strip("`")
        if s.lower().startswith("json"):
            s = s[4:]
    try:
        obj = json.loads(s)
    except json.JSONDecodeError as e:
        # try to locate the first {...} block
        i, j = s.find("{"), s.rfind("}")
        if i >= 0 and j > i:
            try:
                obj = json.loads(s[i:j + 1])
            except json.JSONDecodeError:
                return None, f"json: {e.msg}"
        else:
            return None, f"json: {e.msg}"
    try:
        return Decision.model_validate(obj), ""
    except ValidationError as e:
        return None, "schema: " + "; ".join(f"{'.'.join(map(str, err['loc']))}: {err['msg']}" for err in e.errors()[:3])