from __future__ import annotations

import re
from typing import Dict, Iterable, Optional

from jinja2 import BaseLoader, Environment, StrictUndefined
from jinja2.exceptions import TemplateError

from fastapi import HTTPException

from ..schemas import (
    TemplatePreviewRequest,
    TemplateRecord,
    TemplateRenderRequest,
    VariableDefinition,
)


class TemplateRenderer:
    """Render templates with strict undefined variables to catch errors early."""

    def __init__(self) -> None:
        self.env = Environment(
            loader=BaseLoader(),
            undefined=StrictUndefined,
            trim_blocks=True,
            lstrip_blocks=True,
            autoescape=False,
        )

    def render_from_record(self, record: TemplateRecord, parameters: dict) -> str:
        normalized = self._normalize_parameters(parameters, record.input_variables)
        return self._render(record.template_body, normalized)

    def preview(self, payload: TemplatePreviewRequest) -> str:
        normalized = self._normalize_parameters(payload.parameters)
        return self._render(payload.template_body, normalized)

    def _render(self, template_body: str, parameters: dict) -> str:
        try:
            template = self.env.from_string(template_body)
            rendered = template.render(**parameters)
            paragraphs = [p.strip() for p in rendered.split("\n\n") if p.strip()]
            return "\n\n".join(paragraphs)
        except TemplateError as exc:
            raise HTTPException(status_code=400, detail=f"模板渲染出错: {exc}") from exc

    def _normalize_parameters(
        self,
        parameters: Dict[str, object],
        definitions: Optional[Iterable[VariableDefinition]] = None,
    ) -> Dict[str, object]:
        type_map = {}
        for definition in definitions or []:
            # Accept both pydantic models and plain dicts from persisted records.
            if isinstance(definition, VariableDefinition):
                name = (definition.name or "").strip()
                data_type = (definition.data_type or "").lower()
            elif isinstance(definition, dict):
                name = (definition.get("name") or "").strip()
                data_type = (definition.get("data_type") or "").lower()
            else:
                continue
            if name:
                type_map[name] = data_type
        return {
            key: self._convert_value(value, type_map.get(key))
            for key, value in parameters.items()
        }

    def _convert_value(self, value: object, data_type: Optional[str]) -> object:
        if value is None or isinstance(value, (int, float, bool)):
            return value
        if isinstance(value, str):
            stripped = value.strip()
            if stripped == "":
                return None
            if (data_type or "").startswith("bool"):
                lowered = stripped.lower()
                if lowered in {"true", "1", "yes", "y", "on"}:
                    return True
                if lowered in {"false", "0", "no", "n", "off"}:
                    return False
            if (data_type or "") in {"number", "integer"} or self._looks_numeric(
                stripped
            ):
                try:
                    return int(stripped) if stripped.isdigit() else float(stripped)
                except ValueError:
                    return value
        return value

    def _looks_numeric(self, value: str) -> bool:
        return bool(re.fullmatch(r"[+-]?\d+(\.\d+)?", value))


renderer = TemplateRenderer()