"""OpenAPI-based tool client for MCP-compatible tool servers.

Compatible with open-webui/openapi-servers (https://github.com/open-webui/openapi-servers).
Fetches the server's OpenAPI spec, converts operations to OpenAI function-calling
definitions, and executes tool calls by making HTTP requests back to the server.
"""

from __future__ import annotations

import json
import logging
from typing import Any

import httpx

logger = logging.getLogger(__name__)


class ToolClient:
    """Client for OpenAPI-compatible tool servers.

    Usage::

        client = ToolClient(base_url="http://localhost:8000", api_key="…")
        tools = await client.get_tools()          # OpenAI tool definitions
        result = await client.call("my_op", {})   # execute a tool call
    """

    def __init__(self, base_url: str, api_key: str = "", timeout: float = 30.0) -> None:
        self._base_url = base_url.rstrip("/")
        self._api_key = api_key
        self._timeout = timeout
        self._spec: dict[str, Any] | None = None
        self._tools: list[dict[str, Any]] | None = None

    @property
    def base_url(self) -> str:
        return self._base_url

    def _headers(self) -> dict[str, str]:
        headers: dict[str, str] = {"Accept": "application/json"}
        if self._api_key:
            headers["Authorization"] = "Bearer " + self._api_key
        return headers

    async def get_spec(self) -> dict[str, Any]:
        """Fetch (and cache) the OpenAPI spec from ``/openapi.json``."""
        if self._spec is not None:
            return self._spec
        async with httpx.AsyncClient(timeout=self._timeout) as http:
            resp = await http.get(
                f"{self._base_url}/openapi.json",
                headers=self._headers(),
            )
            resp.raise_for_status()
            self._spec = resp.json()
        path_count = len(self._spec.get("paths", {}))
        logger.info("Loaded OpenAPI spec from %s (%d paths)", self._base_url, path_count)
        return self._spec

    async def get_tools(self) -> list[dict[str, Any]]:
        """Return OpenAI function-calling tool definitions from the OpenAPI spec."""
        if self._tools is not None:
            return self._tools
        spec = await self.get_spec()
        self._tools = _spec_to_openai_tools(spec)
        logger.info("Registered %d tools from %s", len(self._tools), self._base_url)
        return self._tools

    async def call(self, tool_name: str, arguments: dict[str, Any]) -> str:
        """Execute a named tool call and return the result as a string.

        Resolves *tool_name* to a path+method in the cached OpenAPI spec,
        partitions *arguments* into path params, query params, and request
        body, then makes the HTTP request.
        """
        spec = await self.get_spec()
        path, method, path_params, query_params, body = _resolve_operation(
            spec, tool_name, arguments
        )

        url = self._base_url + path
        for key, value in path_params.items():
            url = url.replace(f"{{{key}}}", str(value))

        async with httpx.AsyncClient(timeout=self._timeout) as http:
            resp = await http.request(
                method=method.upper(),
                url=url,
                headers=self._headers(),
                params=query_params if query_params else None,
                json=body if body else None,
            )
            resp.raise_for_status()
            content_type = resp.headers.get("content-type", "")
            if "application/json" in content_type:
                try:
                    return json.dumps(resp.json(), indent=2)
                except ValueError:
                    pass
            return resp.text


# ---------------------------------------------------------------------------
# OpenAPI → OpenAI tool-definition helpers
# ---------------------------------------------------------------------------


def _resolve_ref(
    schema: dict[str, Any], components: dict[str, Any]
) -> dict[str, Any]:
    """Recursively resolve a ``$ref`` inside an OpenAPI schema."""
    if "$ref" not in schema:
        return schema
    ref: str = schema["$ref"]  # e.g. "#/components/schemas/Foo"
    parts = ref.lstrip("#/").split("/")
    # parts = ["components", "schemas", "Foo"]
    obj: Any = {"components": components}
    for part in parts:
        if not isinstance(obj, dict):
            return {}
        obj = obj.get(part, {})
    return _schema_to_json_schema(obj, components)


def _schema_to_json_schema(
    schema: dict[str, Any], components: dict[str, Any] | None = None
) -> dict[str, Any]:
    """Convert an OpenAPI schema object to a JSON Schema-compatible dict."""
    if not schema:
        return {}
    resolved = _resolve_ref(schema, components or {}) if "$ref" in schema else schema
    result: dict[str, Any] = {}
    for key in ("type", "description", "enum", "format", "default", "minimum", "maximum"):
        if key in resolved:
            result[key] = resolved[key]
    if "items" in resolved:
        result["items"] = _schema_to_json_schema(resolved["items"], components)
    if "properties" in resolved:
        result["properties"] = {
            k: _schema_to_json_schema(v, components)
            for k, v in resolved["properties"].items()
        }
    if "required" in resolved:
        result["required"] = resolved["required"]
    return result


def _operation_id(method: str, path: str, op: dict[str, Any]) -> str:
    """Return an operation ID, generating one from method+path if absent."""
    if op.get("operationId"):
        return str(op["operationId"])
    slug = path.strip("/").replace("/", "_").replace("{", "").replace("}", "")
    return f"{method}_{slug}" if slug else method


def _spec_to_openai_tools(spec: dict[str, Any]) -> list[dict[str, Any]]:
    """Convert an OpenAPI 3.x spec to a list of OpenAI function-calling tool defs."""
    tools: list[dict[str, Any]] = []
    paths: dict[str, Any] = spec.get("paths", {})
    components: dict[str, Any] = spec.get("components", {})

    for path, path_item in paths.items():
        for http_method in ("get", "post", "put", "patch", "delete"):
            op: dict[str, Any] | None = path_item.get(http_method)
            if op is None:
                continue

            op_id = _operation_id(http_method, path, op)
            description: str = op.get("summary") or op.get("description") or ""

            properties: dict[str, Any] = {}
            required: list[str] = []

            # URL / query parameters
            for param in op.get("parameters", []):
                name: str = param["name"]
                schema = _schema_to_json_schema(
                    param.get("schema", {"type": "string"}), components
                )
                if param.get("description"):
                    schema["description"] = param["description"]
                properties[name] = schema
                if param.get("required"):
                    required.append(name)

            # Request body – flatten top-level object properties
            rb: dict[str, Any] = op.get("requestBody", {})
            if rb:
                json_content = rb.get("content", {}).get("application/json", {})
                body_schema = _schema_to_json_schema(
                    json_content.get("schema", {}), components
                )
                if body_schema.get("type") == "object":
                    for prop_name, prop_schema in body_schema.get("properties", {}).items():
                        properties[prop_name] = prop_schema
                    if rb.get("required", False):
                        required.extend(body_schema.get("required", []))

            tool: dict[str, Any] = {
                "type": "function",
                "function": {
                    "name": op_id,
                    "description": description,
                    "parameters": {
                        "type": "object",
                        "properties": properties,
                    },
                },
            }
            if required:
                tool["function"]["parameters"]["required"] = required

            tools.append(tool)

    return tools


def _resolve_operation(
    spec: dict[str, Any],
    operation_id: str,
    arguments: dict[str, Any],
) -> tuple[str, str, dict[str, Any], dict[str, Any], dict[str, Any]]:
    """Find path+method for *operation_id* and split *arguments* into parts.

    Returns ``(path, method, path_params, query_params, body)``.

    * ``path_params`` – values that replace ``{placeholders}`` in the URL path.
    * ``query_params`` – values appended as query string.
    * ``body`` – any remaining arguments sent as the JSON request body.
    """
    paths: dict[str, Any] = spec.get("paths", {})

    for path, path_item in paths.items():
        for http_method in ("get", "post", "put", "patch", "delete"):
            op: dict[str, Any] | None = path_item.get(http_method)
            if op is None:
                continue
            if _operation_id(http_method, path, op) != operation_id:
                continue

            path_params: dict[str, Any] = {}
            query_params: dict[str, Any] = {}
            declared_params: set[str] = set()

            for param in op.get("parameters", []):
                name = param["name"]
                declared_params.add(name)
                if name not in arguments:
                    continue
                if param.get("in") == "path":
                    path_params[name] = arguments[name]
                else:
                    query_params[name] = arguments[name]

            body = {k: v for k, v in arguments.items() if k not in declared_params}
            return path, http_method, path_params, query_params, body

    raise ValueError(f"Operation '{operation_id}' not found in spec")