"""BasePrompt schema definition."""
from __future__ import annotations

import warnings
from abc import ABC
from string import Formatter
from typing import Any, Callable, Dict, List, Literal, Set

from langchain.schema.messages import BaseMessage, HumanMessage
from langchain.schema.prompt import PromptValue
from langchain.schema.prompt_template import BasePromptTemplate
from langchain.utils.formatting import formatter


def jinja2_formatter(template: str, **kwargs: Any) -> str:
    """Format a template using jinja2.

    *Security warning*: As of LangChain 0.0.329, this method uses Jinja2's
        SandboxedEnvironment by default. However, this sand-boxing should
        be treated as a best-effort approach rather than a guarantee of security.
        Do not accept jinja2 templates from untrusted sources as they may lead
        to arbitrary Python code execution.

        https://jinja.palletsprojects.com/en/3.1.x/sandbox/
    """
    try:
        from jinja2.sandbox import SandboxedEnvironment
    except ImportError:
        raise ImportError(
            "jinja2 not installed, which is needed to use the jinja2_formatter. "
            "Please install it with `pip install jinja2`."
            "Please be cautious when using jinja2 templates. "
            "Do not expand jinja2 templates using unverified or user-controlled "
            "inputs as that can result in arbitrary Python code execution."
        )

    # This uses a sandboxed environment to prevent arbitrary code execution.
    # Jinja2 uses an opt-out rather than opt-in approach for sand-boxing.
    # Please treat this sand-boxing as a best-effort approach rather than
    # a guarantee of security.
    # We recommend to never use jinja2 templates with untrusted inputs.
    # https://jinja.palletsprojects.com/en/3.1.x/sandbox/
    # approach not a guarantee of security.
    return SandboxedEnvironment().from_string(template).render(**kwargs)


def validate_jinja2(template: str, input_variables: List[str]) -> None:
    """
    Validate that the input variables are valid for the template.
    Issues a warning if missing or extra variables are found.

    Args:
        template: The template string.
        input_variables: The input variables.
    """
    input_variables_set = set(input_variables)
    valid_variables = _get_jinja2_variables_from_template(template)
    missing_variables = valid_variables - input_variables_set
    extra_variables = input_variables_set - valid_variables

    warning_message = ""
    if missing_variables:
        warning_message += f"Missing variables: {missing_variables} "

    if extra_variables:
        warning_message += f"Extra variables: {extra_variables}"

    if warning_message:
        warnings.warn(warning_message.strip())


def _get_jinja2_variables_from_template(template: str) -> Set[str]:
    try:
        from jinja2 import Environment, meta
    except ImportError:
        raise ImportError(
            "jinja2 not installed, which is needed to use the jinja2_formatter. "
            "Please install it with `pip install jinja2`."
        )
    env = Environment()
    ast = env.parse(template)
    variables = meta.find_undeclared_variables(ast)
    return variables


DEFAULT_FORMATTER_MAPPING: Dict[str, Callable] = {
    "f-string": formatter.format,
    "jinja2": jinja2_formatter,
}

DEFAULT_VALIDATOR_MAPPING: Dict[str, Callable] = {
    "f-string": formatter.validate_input_variables,
    "jinja2": validate_jinja2,
}


def check_valid_template(
    template: str, template_format: str, input_variables: List[str]
) -> None:
    """Check that template string is valid.

    Args:
        template: The template string.
        template_format: The template format. Should be one of "f-string" or "jinja2".
        input_variables: The input variables.

    Raises:
        ValueError: If the template format is not supported.
    """
    if template_format not in DEFAULT_FORMATTER_MAPPING:
        valid_formats = list(DEFAULT_FORMATTER_MAPPING)
        raise ValueError(
            f"Invalid template format. Got `{template_format}`;"
            f" should be one of {valid_formats}"
        )
    try:
        validator_func = DEFAULT_VALIDATOR_MAPPING[template_format]
        validator_func(template, input_variables)
    except KeyError as e:
        raise ValueError(
            "Invalid prompt schema; check for mismatched or missing input parameters. "
            + str(e)
        )


def get_template_variables(template: str, template_format: str) -> List[str]:
    """Get the variables from the template.

    Args:
        template: The template string.
        template_format: The template format. Should be one of "f-string" or "jinja2".

    Returns:
        The variables from the template.

    Raises:
        ValueError: If the template format is not supported.
    """
    if template_format == "jinja2":
        # Get the variables for the template
        input_variables = _get_jinja2_variables_from_template(template)
    elif template_format == "f-string":
        input_variables = {
            v for _, v, _, _ in Formatter().parse(template) if v is not None
        }
    else:
        raise ValueError(f"Unsupported template format: {template_format}")

    return sorted(input_variables)


class StringPromptValue(PromptValue):
    """String prompt value."""

    text: str
    """Prompt text."""
    type: Literal["StringPromptValue"] = "StringPromptValue"

    def to_string(self) -> str:
        """Return prompt as string."""
        return self.text

    def to_messages(self) -> List[BaseMessage]:
        """Return prompt as messages."""
        return [HumanMessage(content=self.text)]


class StringPromptTemplate(BasePromptTemplate, ABC):
    """String prompt that exposes the format method, returning a prompt."""

    def format_prompt(self, **kwargs: Any) -> PromptValue:
        """Create Chat Messages."""
        return StringPromptValue(text=self.format(**kwargs))
