"""JSON-based parser per la strategia di trading (Phase 1).

L'AST è una piccola gerarchia di dataclass:

* :class:`Strategy` è il top-level (lista di :class:`Rule`).
* :class:`Rule` accoppia una condizione (Node) ad un'azione (str).
* :class:`Node` è un'unione: nodi operatore (:class:`OpNode`) e nodi leaf
  (:class:`IndicatorNode`, :class:`FeatureNode`, :class:`LiteralNode`).

Convenzione di shape sui dict in input:

* Nodi operatore: ``{"op": "<name>", "args": [<node>, ...]}``.
* Nodi indicator: ``{"kind": "indicator", "name": "<name>", "params": [<num>, ...]}``.
* Nodi feature:   ``{"kind": "feature",   "name": "<name>"}``.
* Nodi literal:   ``{"kind": "literal",   "value": <number>}``.
"""

from __future__ import annotations

import json
from dataclasses import dataclass, field
from typing import Any

from .grammar import (
    ACTION_VALUES,
    ALL_OPS,
)


class ParseError(Exception):
    """Raised when a JSON strategy cannot be parsed into a valid AST."""


# ---------------------------------------------------------------------------
# Dataclass AST
# ---------------------------------------------------------------------------


@dataclass
class OpNode:
    """Operator node: logical / comparator / crossover."""

    op: str
    args: list[Node] = field(default_factory=list)


@dataclass
class IndicatorNode:
    """Leaf: indicatore tecnico calcolato sul dataframe OHLCV."""

    name: str
    params: list[float] = field(default_factory=list)


@dataclass
class FeatureNode:
    """Leaf: colonna OHLCV (open/high/low/close/volume)."""

    name: str


@dataclass
class LiteralNode:
    """Leaf: costante numerica."""

    value: float


Node = OpNode | IndicatorNode | FeatureNode | LiteralNode


@dataclass
class Rule:
    condition: Node
    action: str


@dataclass
class Strategy:
    rules: list[Rule]


# ---------------------------------------------------------------------------
# Conversione dict -> Node
# ---------------------------------------------------------------------------


def _to_node(obj: Any) -> Node:
    if not isinstance(obj, dict):
        raise ParseError(f"Node must be a JSON object, got {type(obj).__name__}")

    has_op = "op" in obj
    has_kind = "kind" in obj
    if has_op and has_kind:
        raise ParseError(
            "Node cannot define both 'op' and 'kind' (mutually exclusive)"
        )
    if not has_op and not has_kind:
        raise ParseError("Node must define either 'op' or 'kind'")

    if has_op:
        op = obj["op"]
        if not isinstance(op, str):
            raise ParseError(f"'op' must be a string, got {type(op).__name__}")
        if op not in ALL_OPS:
            raise ParseError(f"Unknown op: {op!r}")
        raw_args = obj.get("args")
        if not isinstance(raw_args, list):
            raise ParseError(f"Operator '{op}' missing 'args' list")
        args = [_to_node(a) for a in raw_args]
        return OpNode(op=op, args=args)

    # leaf node
    kind = obj["kind"]
    if not isinstance(kind, str):
        raise ParseError(f"'kind' must be a string, got {type(kind).__name__}")

    if kind == "indicator":
        name = obj.get("name")
        if not isinstance(name, str):
            raise ParseError("indicator node requires string 'name'")
        raw_params = obj.get("params", [])
        if not isinstance(raw_params, list):
            raise ParseError("indicator 'params' must be a list")
        params: list[float] = []
        for p in raw_params:
            if isinstance(p, bool) or not isinstance(p, (int, float)):
                raise ParseError(
                    f"indicator '{name}' params accept only numbers, got {p!r}"
                )
            params.append(float(p))
        return IndicatorNode(name=name, params=params)

    if kind == "feature":
        name = obj.get("name")
        if not isinstance(name, str):
            raise ParseError("feature node requires string 'name'")
        return FeatureNode(name=name)

    if kind == "literal":
        if "value" not in obj:
            raise ParseError("literal node requires 'value'")
        value = obj["value"]
        if isinstance(value, bool) or not isinstance(value, (int, float)):
            raise ParseError(f"literal value must be numeric, got {value!r}")
        return LiteralNode(value=float(value))

    raise ParseError(f"Unknown leaf kind: {kind!r}")


# ---------------------------------------------------------------------------
# Top-level parser
# ---------------------------------------------------------------------------


def parse_strategy(src: str) -> Strategy:
    """Parse a JSON strategy string into a :class:`Strategy` AST.

    Lo schema atteso è::

        {
          "rules": [
            {"condition": <node>, "action": "<action-string>"},
            ...
          ]
        }

    Raise :class:`ParseError` su JSON malformato o struttura inattesa.
    """
    try:
        parsed = json.loads(src)
    except json.JSONDecodeError as e:
        raise ParseError(f"invalid JSON: {e}") from e

    if not isinstance(parsed, dict):
        raise ParseError("Top-level must be a JSON object with 'rules'")
    if "rules" not in parsed:
        raise ParseError("Top-level object must contain 'rules' key")
    raw_rules = parsed["rules"]
    if not isinstance(raw_rules, list):
        raise ParseError("'rules' must be a list")
    if not raw_rules:
        raise ParseError("Strategy must contain at least one rule")

    rules: list[Rule] = []
    for raw in raw_rules:
        if not isinstance(raw, dict):
            raise ParseError(f"Rule must be a JSON object, got {raw!r}")
        if "condition" not in raw or "action" not in raw:
            raise ParseError(
                f"Rule must contain 'condition' and 'action' keys: {raw!r}"
            )
        action = raw["action"]
        if not isinstance(action, str):
            raise ParseError(f"action must be a string, got {action!r}")
        if action not in ACTION_VALUES:
            raise ParseError(
                f"action must be one of {sorted(ACTION_VALUES)}, got {action!r}"
            )
        cond = _to_node(raw["condition"])
        rules.append(Rule(condition=cond, action=action))

    return Strategy(rules=rules)